X
Forgot Password

If you have forgotten your password you can enter your email here and get a temporary password sent to your email.

Anti-Actin, clone C4 antibody

RRID:AB_2223041

Antibody ID

AB_2223041

Target Antigen

Actin clone C4 horse, human, bovine, chicken/bird, drosophila/arthropod, mouse, other mammalian, hamster, porcine, xenopus/amphibian, mollusc, non-human primate, rat, donkey, goat, other invertebrate, rabbit, guinea pig, reptile, amoeba/protozoa, bacteria/archaea, canine, plant, zebrafish/fish, c elegans/worm, chemical, feline, virus, sheep, yeast/fungi, all

Proper Citation

(Millipore Cat# MAB1501, RRID:AB_2223041)

Clonality

monoclonal antibody

Comments

seller recommendations: IgG1; IgG1 Immunofluorescence; Immunohistochemistry; Western Blot; Immunocytochemistry; ELISA; ELISA, IC, IF, IH, IH(P), WB
Consolidated with AB_11212828, AB_570950, AB_11214116, and AB_94235 on 10/07/16

Clone ID

Clone C4

Host Organism

mouse

Eldecalcitol Causes FGF23 Resistance for Pi Reabsorption and Improves Rachitic Bone Phenotypes in the Male Hyp Mouse.

  • Kaneko I
  • Endocrinology
  • 2018 Jul 1

Literature context:


Abstract:

X-linked hypophosphatemia (XLH), the most common form of inheritable rickets, is caused by inactivation of phosphate-regulating gene with homologies to endopeptidases on the X chromosome (PHEX) and leads to fibroblast growth factor (FGF) 23-dependent renal inorganic phosphate (Pi) wasting. In the present study, we investigated whether maintaining Pi homeostasis with a potent vitamin D3 analog, eldecalcitol [1α,25-dihydroxy-2β-(3-hydroxypropyloxy) vitamin D3; ED71], could improve hypophosphatemic rickets in a murine model of XLH, the Hyp mouse. Vehicle, ED71, or 1,25-dihydroxyvitamin D was subcutaneously injected five times weekly in wild-type (WT) and Hyp mice for 4 weeks, from 4 to 8 weeks of age. Injection of ED71 into WT mice suppressed the synthesis of renal 1,25-dihydroxyvitamin D and promoted phosphaturic activity. In contrast, administration of ED71 to Hyp mice completely restored renal Pi transport and NaPi-2a protein levels, although the plasma-intact FGF23 levels were further increased. In addition, ED71 markedly increased the levels of the scaffold proteins, renal sodium-hydrogen exchanger regulatory factor 1, and ezrin in the Hyp mouse kidney. Treatment with ED71 increased the body weight and improved hypophosphatemia, the bone volume/total volume, bone mineral content, and growth plate structure in Hyp mice. Thus, ED71 causes FGF23 resistance for phosphate reabsorption and improves rachitic bone phenotypes in Hyp mice. In conclusion, ED71 has opposite effects on phosphate homeostasis in WT and Hyp mice. Analysis of Hyp mice treated with ED71 could result in an additional model for elucidating PHEX abnormalities.

Funding information:
  • NIEHS NIH HHS - P30 ES003819(United States)

Phospholipase PLA2G6, a Parkinsonism-Associated Gene, Affects Vps26 and Vps35, Retromer Function, and Ceramide Levels, Similar to α-Synuclein Gain.

  • Lin G
  • Cell Metab.
  • 2018 Jun 7

Literature context:


Abstract:

Mutations in PLA2G6 (PARK14) cause neurodegenerative disorders in humans, including autosomal recessive neuroaxonal dystrophy and early-onset parkinsonism. We show that loss of iPLA2-VIA, the fly homolog of PLA2G6, reduces lifespan, impairs synaptic transmission, and causes neurodegeneration. Phospholipases typically hydrolyze glycerol phospholipids, but loss of iPLA2-VIA does not affect the phospholipid composition of brain tissue but rather causes an elevation in ceramides. Reducing ceramides with drugs, including myriocin or desipramine, alleviates lysosomal stress and suppresses neurodegeneration. iPLA2-VIA binds the retromer subunits Vps35 and Vps26 and enhances retromer function to promote protein and lipid recycling. Loss of iPLA2-VIA impairs retromer function, leading to a progressive increase in ceramide. This induces a positive feedback loop that affects membrane fluidity and impairs retromer function and neuronal function. Similar defects are observed upon loss of vps26 or vps35 or overexpression of α-synuclein, indicating that these defects may be common in Parkinson disease.

Funding information:
  • NCI NIH HHS - R01 CA130893(United States)

Methylation changes and aberrant expression of FGFR3 in Lewy body disease neurons.

  • Tsuchida T
  • Brain Res.
  • 2018 Jun 14

Literature context:


Abstract:

Lewy body disease (LBD) is characterized by accumulation of aggregated α-synuclein in the central nervous system as eosinophilic cytoplasmic inclusions called Lewy bodies. According to their distribution pattern, it is classified into brainstem LBD, limbic LBD and diffuse neocortical LBD. It has been reported that α-synuclein affects various points in the MAPK cascade but its relationship with FGF receptors, which are the most upstream of the pathway, has not been previously investigated. We discovered that among the four FGFRs, FGFR3 showed neuronal upregulation in LBD brains histopathologically. Further examination using neuron-specific methylome analysis revealed that the gene body of FGFR3 was hypermethylated in LBD, suggesting its increased transcription. Altered methylation was not observed in the non-neuronal genome. Altered methylation status was associated with the severity of α-synuclein pathology.

Funding information:
  • NIDCD NIH HHS - R01DC007487(United States)

Transient increase in sAPPα secretion in response to Aβ1-42 oligomers: an attempt of neuronal self-defense?

  • Rose C
  • Neurobiol. Aging
  • 2018 Jun 4

Literature context:


Abstract:

Amyloid precursor protein (APP), a key molecule of Alzheimer disease, is metabolized in 2 antagonist pathways generating the soluble APP alpha (sAPPα) having neuroprotective properties and the beta amyloid (Aβ) peptide at the origin of neurotoxic oligomers, particularly Aβ1-42. Whether extracellular Aβ1-42 oligomers modulate the formation and secretion of sAPPα is not known. We report here that the addition of Aβ1-42 oligomers to primary cortical neurons induced a transient increase in α-secretase activity and secreted sAPPα 6-9 hours later. Preventing the generation of sAPPα by using small interfering RNAs (siRNAs) for the α-secretases ADAM10 and ADAM17 or for APP led to increased Aβ1-42 oligomer-induced cell death after 24 hours. Neuronal injuries due to oxidative stress or growth factor deprivation also generated sAPPα 7 hours later. Finally, acute injection of Aβ1-42 oligomers into wild-type mouse hippocampi induced transient secretion of sAPPα 48-72 hours later. Altogether, these data suggest that neurons respond to stress by generating sAPPα for their survival. These data must be taken into account when interpreting sAPPα levels as a biomarker in neurological disorders.

Cell-Type-Specific Role of ΔFosB in Nucleus Accumbens In Modulating Intermale Aggression.

  • Aleyasin H
  • J. Neurosci.
  • 2018 Jun 27

Literature context:


Abstract:

A growing number of studies implicate the brain's reward circuitry in aggressive behavior. However, the cellular and molecular mechanisms within brain reward regions that modulate the intensity of aggression as well as motivation for it have been underexplored. Here, we investigate the cell-type-specific influence of ΔFosB, a transcription factor known to regulate a range of reward and motivated behaviors, acting in the nucleus accumbens (NAc), a key reward region, in male aggression in mice. We show that ΔFosB is specifically increased in dopamine D1 receptor (Drd1)-expressing medium spiny neurons (D1-MSNs) in NAc after repeated aggressive encounters. Viral-mediated induction of ΔFosB selectively in D1-MSNs of NAc intensifies aggressive behavior without affecting the preference for the aggression-paired context in a conditioned place preference (CPP) assay. In contrast, ΔFosB induction selectively in D2-MSNs reduces the time spent exploring the aggression-paired context during CPP without affecting the intensity of aggression per se. These data strongly support a dissociable cell-type-specific role for ΔFosB in the NAc in modulating aggression and aggression reward.SIGNIFICANCE STATEMENT Aggressive behavior is associated with several neuropsychiatric disorders and can be disruptive for affected individuals as well as their victims. Studies have shown a positive reinforcement mechanism underlying aggressive behavior that shares many common features with drug addiction. Here, we explore the cell-type-specific role of the addiction-associated transcription factor ΔFosB in the nucleus accumbens in aggression. We found that ΔFosB expression promotes aggressive behavior, effects that are dissociable from its effects on aggression reward. This finding is a significant first step in identifying therapeutic targets for the reduction of aggressive behavior across a range of neuropsychiatric illnesses.

Funding information:
  • NIAID NIH HHS - R21 AI079373(United States)

Stress Granule Assembly Disrupts Nucleocytoplasmic Transport.

  • Zhang K
  • Cell
  • 2018 May 3

Literature context:


Abstract:

Defects in nucleocytoplasmic transport have been identified as a key pathogenic event in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) mediated by a GGGGCC hexanucleotide repeat expansion in C9ORF72, the most common genetic cause of ALS/FTD. Furthermore, nucleocytoplasmic transport disruption has also been implicated in other neurodegenerative diseases with protein aggregation, suggesting a shared mechanism by which protein stress disrupts nucleocytoplasmic transport. Here, we show that cellular stress disrupts nucleocytoplasmic transport by localizing critical nucleocytoplasmic transport factors into stress granules, RNA/protein complexes that play a crucial role in ALS pathogenesis. Importantly, inhibiting stress granule assembly, such as by knocking down Ataxin-2, suppresses nucleocytoplasmic transport defects as well as neurodegeneration in C9ORF72-mediated ALS/FTD. Our findings identify a link between stress granule assembly and nucleocytoplasmic transport, two fundamental cellular processes implicated in the pathogenesis of C9ORF72-mediated ALS/FTD and other neurodegenerative diseases.

Funding information:
  • Canadian Institutes of Health Research - (Canada)

The GABAA Receptor β Subunit Is Required for Inhibitory Transmission.

  • Nguyen QA
  • Neuron
  • 2018 May 16

Literature context:


Abstract:

While the canonical assembly of a GABAA receptor contains two α subunits, two β subunits, and a fifth subunit, it is unclear which variants of each subunit are necessary for native receptors. We used CRISPR/Cas9 to dissect the role of the GABAA receptor β subunits in inhibitory transmission onto hippocampal CA1 pyramidal cells and found that deletion of all β subunits 1, 2, and 3 completely eliminated inhibitory responses. In addition, only knockout of β3, alone or in combination with another β subunit, impaired inhibitory synaptic transmission. We found that β3 knockout impairs inhibitory input from PV but not SOM expressing interneurons. Furthermore, expression of β3 alone on the background of the β1-3 subunit knockout was sufficient to restore synaptic and extrasynaptic inhibitory transmission. These findings reveal a crucial role for the β3 subunit in inhibitory transmission and identify a synapse-specific role of the β3 subunit in GABAergic synaptic transmission.

Funding information:
  • NIGMS NIH HHS - R01 GM084364(United States)

Basal mitophagy is widespread in Drosophila but minimally affected by loss of Pink1 or parkin.

  • Lee JJ
  • J. Cell Biol.
  • 2018 May 7

Literature context:


Abstract:

The Parkinson's disease factors PINK1 and parkin are strongly implicated in stress-induced mitophagy in vitro, but little is known about their impact on basal mitophagy in vivo. We generated transgenic Drosophila melanogaster expressing fluorescent mitophagy reporters to evaluate the impact of Pink1/parkin mutations on basal mitophagy under physiological conditions. We find that mitophagy is readily detectable and abundant in many tissues, including Parkinson's disease-relevant dopaminergic neurons. However, we did not detect mitolysosomes in flight muscle. Surprisingly, in Pink1 or parkin null flies, we did not observe any substantial impact on basal mitophagy. Because these flies exhibit locomotor defects and dopaminergic neuron loss, our findings raise questions about current assumptions of the pathogenic mechanism associated with the PINK1/parkin pathway. Our findings provide evidence that Pink1 and parkin are not essential for bulk basal mitophagy in Drosophila They also emphasize that mechanisms underpinning basal mitophagy remain largely obscure.

Funding information:
  • Medical Research Council - MC_UP_1501/1()
  • NCI NIH HHS - CA111294(United States)

Intrinsic Instability of BOK Enables Membrane Permeabilization in Apoptosis.

  • Zheng JH
  • Cell Rep
  • 2018 May 15

Literature context:


Abstract:

The effector B cell lymphoma-2 (BCL-2) protein BCL-2 ovarian killer (BOK) induces mitochondrial outer membrane permeabilization (MOMP) to initiate apoptosis upon inhibition of the proteasome. How BOK mediates MOMP is mechanistically unknown. The NMR structure of the BCL-2 core of human BOK reveals a conserved architecture with an atypical hydrophobic groove that undergoes conformational exchange. Remarkably, the BCL-2 core of BOK spontaneously associates with purified mitochondria to release cytochrome c in MOMP assays. Alanine substitution of a unique glycine in helix α1 stabilizes BOK, as shown by thermal shift and urea denaturation analyses, and significantly inhibits MOMP, liposome permeabilization, and cell death. Activated BID does not activate WT BOK or the stabilized alanine mutant to promote cell death. We propose that BOK-mediated membrane permeabilization is governed in part by its unique metastability of the hydrophobic groove and helix α1 and not through activation by BH3 ligands.

Funding information:
  • NIAID NIH HHS - R01 AI089417(United States)

EP300-Mediated Lysine 2-Hydroxyisobutyrylation Regulates Glycolysis.

  • Huang H
  • Mol. Cell
  • 2018 May 17

Literature context:


Abstract:

Lysine 2-hydroxyisobutyrylation (Khib) is an evolutionarily conserved and widespread histone mark like lysine acetylation (Kac). Here we report that EP300 functions as a lysine 2-hyroxyisobutyryltransferase to regulate glycolysis in response to nutritional cues. We discovered that EP300 differentially regulates Khib and Kac on distinct lysine sites, with only 6 of the 149 EP300-targeted Khib sites overlapping with the 693 EP300-targeted Kac sites. We demonstrate that diverse cellular proteins, particularly glycolytic enzymes, are targeted by EP300 for Khib, but not for Kac. Specifically, deletion of EP300 significantly reduces Khib levels on several EP300-dependent, Khib-specific sites on key glycolytic enzymes including ENO1, decreasing their catalytic activities. Consequently, EP300-deficient cells have impaired glycolysis and are hypersensitive to glucose-depletion-induced cell death. Our study reveals an EP300-catalyzed, Khib-specific molecular mechanism that regulates cellular glucose metabolism and further indicate that EP300 has an intrinsic ability to select short-chain acyl-CoA-dependent protein substrates.

Funding information:
  • Intramural NIH HHS - ZIA ES102205-10()
  • NIDDK NIH HHS - R01 DK107868()
  • NIGMS NIH HHS - R01 GM115961()
  • NINDS NIH HHS - R01 NS073502(United States)

Ari-1 Regulates Myonuclear Organization Together with Parkin and Is Associated with Aortic Aneurysms.

  • Tan KL
  • Dev. Cell
  • 2018 Apr 23

Literature context:


Abstract:

Nuclei are actively positioned and anchored to the cytoskeleton via the LINC (Linker of Nucleoskeleton and Cytoskeleton) complex. We identified mutations in the Parkin-like E3 ubiquitin ligase Ariadne-1 (Ari-1) that affect the localization and distribution of LINC complex members in Drosophila. ari-1 mutants exhibit nuclear clustering and morphology defects in larval muscles. We show that Ari-1 mono-ubiquitinates the core LINC complex member Koi. Surprisingly, we discovered functional redundancy between Parkin and Ari-1: increasing Parkin expression rescues ari-1 mutant phenotypes and vice versa. We further show that rare variants in the human homolog of ari-1 (ARIH1) are associated with thoracic aortic aneurysms and dissections, conditions resulting from smooth muscle cell (SMC) dysfunction. Human ARIH1 rescues fly ari-1 mutant phenotypes, whereas human variants found in patients fail to do so. In addition, SMCs obtained from patients display aberrant nuclear morphology. Hence, ARIH1 is critical in anchoring myonuclei to the cytoskeleton.

Funding information:
  • Intramural NIH HHS - (United States)

Participation of the dentate-rubral pathway in the kindling model of epilepsy.

  • Hernández-Cerón M
  • J. Neurosci. Res.
  • 2018 Mar 12

Literature context:


Abstract:

Lesions of the cerebellar dentate nucleus (DN) reduce the after-discharge duration induced by repetitive kindling stimulation and decrease seizures to a lower rank according to Racine's scale. The DN sends cholinergic and glutamatergic fibers to the red nucleus (RN), which is composed of glutamatergic and GABAergic cells. To test the participation of these neurotransmitters in seizures, we compared the levels of glutamate and gamma-aminobutyric acid (GABA) at the RN in a control condition, a kindled stage, and a kindled stage followed by DN lesions. We found that the kindled stage was associated with significant reductions in glutamate and GABA in the RN and that the lesions of the DN in kindled rats reversed the severity of seizures and restored the GABA levels. GAD65 , a GABA-synthesizing enzyme, was increased in kindled rats and decreased after DN lesions. GAD65 commonly appears localized at nerve terminals and synapses, and it is only activated when GABA neurotransmission occurs. Thus, it is possible that the increased expression of GAD65 found in kindled rats could be due to an exacerbated demand for GABA due to kindled seizures. It is known that GABA maintains the inhibitory tone that counterbalances neuronal excitation. The decreased expression of GAD65 found after the DN lesions indicated that the GABA-synthesizing enzyme was no longer required once it eliminated the excitatory glutamate input to the RN. We thus conclude that DN lesions and their consequent biochemical changes are capable of decreasing the generalized seizures induced by kindling stimulation. © 2016 Wiley Periodicals, Inc.

Funding information:
  • NINDS NIH HHS - T32 NS007220(United States)

LRRTM1 underlies synaptic convergence in visual thalamus.

  • Monavarfeshani A
  • Elife
  • 2018 Feb 9

Literature context:


Abstract:

It has long been thought that the mammalian visual system is organized into parallel pathways, with incoming visual signals being parsed in the retina based on feature (e.g. color, contrast and motion) and then transmitted to the brain in unmixed, feature-specific channels. To faithfully convey feature-specific information from retina to cortex, thalamic relay cells must receive inputs from only a small number of functionally similar retinal ganglion cells. However, recent studies challenged this by revealing substantial levels of retinal convergence onto relay cells. Here, we sought to identify mechanisms responsible for the assembly of such convergence. Using an unbiased transcriptomics approach and targeted mutant mice, we discovered a critical role for the synaptic adhesion molecule Leucine Rich Repeat Transmembrane Neuronal 1 (LRRTM1) in the emergence of retinothalamic convergence. Importantly, LRRTM1 mutant mice display impairment in visual behaviors, suggesting a functional role of retinothalamic convergence in vision.

Funding information:
  • National Eye Institute - EY021222()
  • National Eye Institute - EY024712()
  • NIGMS NIH HHS - R01 GM059507-09(United States)
  • Virginia Tech Carilion Research Institute - Medical Research Scholars Program()

Radial Glial Fibers Promote Neuronal Migration and Functional Recovery after Neonatal Brain Injury.

  • Jinnou H
  • Cell Stem Cell
  • 2018 Jan 4

Literature context:


Abstract:

Radial glia (RG) are embryonic neural stem cells (NSCs) that produce neuroblasts and provide fibers that act as a scaffold for neuroblast migration during embryonic development. Although they normally disappear soon after birth, here we found that RG fibers can persist in injured neonatal mouse brains and act as a scaffold for postnatal ventricular-subventricular zone (V-SVZ)-derived neuroblasts that migrate to the lesion site. This injury-induced maintenance of RG fibers has a limited time window during post-natal development and promotes directional saltatory movement of neuroblasts via N-cadherin-mediated cell-cell contacts that promote RhoA activation. Transplanting an N-cadherin-containing scaffold into injured neonatal brains likewise promotes migration and maturation of V-SVZ-derived neuroblasts, leading to functional improvements in impaired gait behaviors. Together these results suggest that RG fibers enable postnatal V-SVZ-derived neuroblasts to migrate toward sites of injury, thereby enhancing neuronal regeneration and functional recovery from neonatal brain injuries.

Funding information:
  • NIDDK NIH HHS - R01 DK082659(United States)

Endosomal Rab cycles regulate Parkin-mediated mitophagy.

  • Yamano K
  • Elife
  • 2018 Jan 23

Literature context:


Abstract:

Damaged mitochondria are selectively eliminated by mitophagy. Parkin and PINK1, gene products mutated in familial Parkinson's disease, play essential roles in mitophagy through ubiquitination of mitochondria. Cargo ubiquitination by E3 ubiquitin ligase Parkin is important to trigger selective autophagy. Although autophagy receptors recruit LC3-labeled autophagic membranes onto damaged mitochondria, how other essential autophagy units such as ATG9A-integrated vesicles are recruited remains unclear. Here, using mammalian cultured cells, we demonstrate that RABGEF1, the upstream factor of the endosomal Rab GTPase cascade, is recruited to damaged mitochondria via ubiquitin binding downstream of Parkin. RABGEF1 directs the downstream Rab proteins, RAB5 and RAB7A, to damaged mitochondria, whose associations are further regulated by mitochondrial Rab-GAPs. Furthermore, depletion of RAB7A inhibited ATG9A vesicle assembly and subsequent encapsulation of the mitochondria by autophagic membranes. These results strongly suggest that endosomal Rab cycles on damaged mitochondria are a crucial regulator of mitophagy through assembling ATG9A vesicles.

Funding information:
  • Japan Science and Technology Agency - JPMJCR13M7(International)
  • Japan Society for the Promotion of Science - 16K15095(International)
  • Japan Society for the Promotion of Science - JP15H01196(International)
  • Japan Society for the Promotion of Science - JP16K18545(International)
  • Japan Society for the Promotion of Science - JP26000014(International)
  • Japan Society for the Promotion of Science - JP26111729(International)
  • Japan Society for the Promotion of Science - JP26840033(International)
  • NIDCR NIH HHS - R03 DE018415-02(United States)
  • NINDS NIH HHS - Intramural program(United States)

Enhanced Transmission at the Calyx of Held Synapse in a Mouse Model for Angelman Syndrome.

  • Wang T
  • Front Cell Neurosci
  • 2018 Jan 23

Literature context:


Abstract:

The neurodevelopmental disorder Angelman syndrome (AS) is characterized by intellectual disability, motor dysfunction, distinct behavioral aspects, and epilepsy. AS is caused by a loss of the maternally expressed UBE3A gene, and many of the symptoms are recapitulated in a Ube3a mouse model of this syndrome. At the cellular level, changes in the axon initial segment (AIS) have been reported, and changes in vesicle cycling have indicated the presence of presynaptic deficits. Here we studied the role of UBE3A in the auditory system by recording synaptic transmission at the calyx of Held synapse in the medial nucleus of the trapezoid body (MNTB) through in vivo whole cell and juxtacellular recordings. We show that MNTB principal neurons in Ube3a mice exhibit a hyperpolarized resting membrane potential, an increased action potential (AP) amplitude and a decreased AP half width. Moreover, both the pre- and postsynaptic AP in the calyx of Held synapse of Ube3a mice showed significantly faster recovery from spike depression. An increase in AIS length was observed in the principal MNTB neurons of Ube3a mice, providing a possible substrate for these gain-of-function changes. Apart from the effect on APs, we also observed that EPSPs showed decreased short-term synaptic depression (STD) during long sound stimulations in AS mice, and faster recovery from STD following these tones, which is suggestive of a presynaptic gain-of-function. Our findings thus provide in vivo evidence that UBE3A plays a critical role in controlling synaptic transmission and excitability at excitatory synapses.

Funding information:
  • NIGMS NIH HHS - GM069593(United States)

A novel selective MAO-B inhibitor with neuroprotective and anti-Parkinsonian properties.

  • Chan HH
  • Eur. J. Pharmacol.
  • 2018 Jan 5

Literature context:


Abstract:

We previously reported that 1,3-bisbenzylimidazolium (DBZIM) bromide was neuroprotective for the dopaminergic system in Parkinson's disease (PD) models of rodent, however the underlying mechanism was unclear. We currently further confirmed that DBZIM ameliorated the Parkinsonian motor deficit and protected the nigrostriatal tract from the neurotoxicity of 1-methyl-4-(2'-methylphenyl)-1,2,3,6-tetrahydropyridine (2'-CH3-MPTP) in C57Bl/6 mice. The dopaminergic degeneration in the substantia nigra par compacta (SNc) and striatum was analyzed by immunohistochemistry while the monoamine oxidase B (MAO-B) inhibition effect of DBZIM was determined by enzyme kinetics. DBZIM was at least as effective as the clinically approved anti-PD drug, l-deprenyl (Selegiline), for both neuroprotection and correction of motor deficits. Mechanistically, DBZIM inhibited the specific activity of MAO-B in the striatum and C6 cells without affecting the protein expression. DBZIM directly inhibited the enzymatic activity of a purified MAO-B protein with an estimated Ki value from 780 to 940nM, in par with that of l-deprenyl (970nM). The physical interaction between DBZIM and MAO-B was proven by NMR analysis, with Kd around 21.5-46.8μM. Our binding and modelling data further illustrated that DBZIM is a mixed inhibitor with its binding to active site partially hindering the substrate binding. Therefore, inhibiting MAO-B is a major mechanism through which DBZIM confers neuroprotection for the dopaminergic neurons against 2'-CH3-MPTP toxicity. Remarkably, the post-lesion treatment with DBZIM provided greater anti-parkinsonian and neuroprotective effects than the l-deprenyl. The current study, together with our previous findings in a 6-OHDA PD model, demonstrated that DBZIM is a promising neuroprotectant for PD with anti-MAO-B property.

Novel role for the testis-enriched HSPA2 protein in regulating epidermal keratinocyte differentiation.

  • Gogler-Pigłowska A
  • J. Cell. Physiol.
  • 2017 Dec 12

Literature context:


Abstract:

HSPA2, a poorly characterized member of the HSPA (HSP70) chaperone family, is a testis-enriched protein involved in male germ cell differentiation. Previously, we revealed that HSPA2 is present in human stratified epithelia, including epidermis, however the contribution of this protein to epithelial biology remained unknown. Here, we show for the first time that HSPA2 is expressed in basal epidermal keratinocytes, albeit not in keratinocytes exhibiting features attributed to primitive undifferentiated progenitors, and participates in the keratinocyte differentiation process. We found that HSPA2 is dispensable for protection of HaCaT keratinocytes against heat shock-induced cytotoxicity. We also shown that lentiviral-mediated shRNA silencing of HSPA2 expression in HaCaT cells caused a set of phenotypic changes characteristic for keratinocytes committed to terminal differentiation such as reduced clonogenic potential, impaired adhesiveness and increased basal and confluency-induced expression of differentiation markers. Moreover, the fraction of undifferentiated cells that rapidly adhered to collagen IV was less numerous in HSPA2-deficient cells than in the control. In a 3D reconstructed human epidermis model, HSPA2 deficiency resulted in accelerated development of a filaggrin-positive layer. Collectively, our results clearly show a link between HSPA2 expression and maintenance of keratinocytes in an undifferentiated state in the basal layer of the epidermis. It seems that HSPA2 could retain keratinocytes from premature entry into the terminal differentiation process. Overall, HSPA2 appears to be necessary for controlling development of properly stratified epidermis and thus for maintenance of skin homeostasis.

Munc18-1 haploinsufficiency impairs learning and memory by reduced synaptic vesicular release in a model of Ohtahara syndrome.

  • Orock A
  • Mol. Cell. Neurosci.
  • 2017 Dec 9

Literature context:


Abstract:

Ohtahara syndrome, also known as type 4 of Early Infantile Epileptic Encephalopathy with suppression bursts (EIEE-4) is currently an untreatable disorder that presents with seizures and impaired cognition. EIEE-4 patients have mutations most frequently in the STXBP1 gene encoding a Sec protein, munc18-1. The exact molecular mechanism of how these munc18-1 mutations cause impaired cognition, remains elusive. The leading haploinsufficiency hypothesis posits that mutations in munc18-1 render the protein unstable leading to its degradation. Expression driven by the healthy allele is not sufficient to maintain the physiological function resulting in haploinsufficiency. The aim of this study has been to understand how munc18-1 haploinsufficiency causes cognitive impairment seen in EIEE-4. Here we present results from behavioral to cellular effects from a mouse model of munc18-1 haploinsufficiency. Munc18-1 heterozygous knock-out mice showed impaired spatial learning and memory in behavior tests as well as reduced synaptic plasticity in hippocampal CA1 long-term potentiation. Cultured munc18-1 heterozygous hippocampal neurons had significantly slower rate of synaptic vesicle release and decreased readily releasable vesicle pool compared to wild-type control neurons in fluorescent FM dye assays. These results demonstrate that reduced munc18-1 levels are sufficient to impair learning and memory by reducing neurotransmitter release. Therefore, our study implicates munc18-1 haploinsufficiency as a primary cause of cognitive impairment seen in EIEE-4 patients.

Funding information:
  • Medical Research Council - G0800346(United Kingdom)
  • NIA NIH HHS - T32 AG052363()
  • NIGMS NIH HHS - P20 GM104934()

Cellular Differentiation of Human Monocytes Is Regulated by Time-Dependent Interleukin-4 Signaling and the Transcriptional Regulator NCOR2.

  • Sander J
  • Immunity
  • 2017 Dec 19

Literature context:


Abstract:

Human in vitro generated monocyte-derived dendritic cells (moDCs) and macrophages are used clinically, e.g., to induce immunity against cancer. However, their physiological counterparts, ontogeny, transcriptional regulation, and heterogeneity remains largely unknown, hampering their clinical use. High-dimensional techniques were used to elucidate transcriptional, phenotypic, and functional differences between human in vivo and in vitro generated mononuclear phagocytes to facilitate their full potential in the clinic. We demonstrate that monocytes differentiated by macrophage colony-stimulating factor (M-CSF) or granulocyte macrophage colony-stimulating factor (GM-CSF) resembled in vivo inflammatory macrophages, while moDCs resembled in vivo inflammatory DCs. Moreover, differentiated monocytes presented with profound transcriptomic, phenotypic, and functional differences. Monocytes integrated GM-CSF and IL-4 stimulation combinatorically and temporally, resulting in a mode- and time-dependent differentiation relying on NCOR2. Finally, moDCs are phenotypically heterogeneous and therefore necessitate the use of high-dimensional phenotyping to open new possibilities for better clinical tailoring of these cellular therapies.

Funding information:
  • NCI NIH HHS - U54CA119338(United States)

Paxillin facilitates timely neurite initiation on soft-substrate environments by interacting with the endocytic machinery.

  • Chang TY
  • Elife
  • 2017 Dec 22

Literature context:


Abstract:

Neurite initiation is the first step in neuronal development and occurs spontaneously in soft tissue environments. Although the mechanisms regulating the morphology of migratory cells on rigid substrates in cell culture are widely known, how soft environments modulate neurite initiation remains elusive. Using hydrogel cultures, pharmacologic inhibition, and genetic approaches, we reveal that paxillin-linked endocytosis and adhesion are components of a bistable switch controlling neurite initiation in a substrate modulus-dependent manner. On soft substrates, most paxillin binds to endocytic factors and facilitates vesicle invagination, elevating neuritogenic Rac1 activity and expression of genes encoding the endocytic machinery. By contrast, on rigid substrates, cells develop extensive adhesions, increase RhoA activity and sequester paxillin from the endocytic machinery, thereby delaying neurite initiation. Our results highlight paxillin as a core molecule in substrate modulus-controlled morphogenesis and define a mechanism whereby neuronal cells respond to environments exhibiting varying mechanical properties.

Funding information:
  • NIAID NIH HHS - R01 AI030914(United States)

Crosstalk between different family members: IL27 recapitulates IFNγ responses in HCC cells, but is inhibited by IL6-type cytokines.

  • Rolvering C
  • Biochim. Biophys. Acta
  • 2017 Dec 12

Literature context:


Abstract:

Interleukin-27 (IL27) is a type-I-cytokine of the IL6/IL12 family predominantly secreted by activated macrophages and dendritic cells. In the liver, IL27 expression was observed to be upregulated in patients with hepatitis B, and sera of hepatocellular carcinoma (HCC) patients contain significantly elevated levels of IL27 compared to healthy controls or patients with hepatitis and/or liver cirrhosis. In this study, we show that IL27 induces STAT1 and STAT3 phosphorylation in 5 HCC lines and 3 different types of non-transformed liver cells. We were especially interested in the relevance of the IL27-induced STAT3 activation in liver cells. Thus, we compared the IL27 responses with those induced by IFNγ (STAT1-dominated response) or IL6-type cytokines (IL6, hyper-IL6 (hy-IL6) or OSM) (STAT3-dominated response) by microarray analysis and find that in HCC cells, IL27 induces an IFNγ-like, STAT1-dependent transcriptional response, but we do not find an effective STAT3-dependent response. Validation experiments corroborate the finding from the microarray evaluation. Interestingly, the availability of STAT1 seems critical in the shaping of the IL27 response, as the siRNA knock-down of STAT1 revealed the ability of IL27 to induce the acute-phase protein γ-fibrinogen, a typical IL6 family characteristic. Moreover, we describe a crosstalk between the signaling of IL6-type cytokines and IL27: responses to the gp130-engaging cytokine IL27 (but not those to IFNs) can be inhibited by IL6-type cytokine pre-stimulation, likely by a SOCS3-mediated mechanism. Thus, IL27 recapitulates IFNγ responses in liver cells, but differs from IFNγ by its sensitivity to SOCS3 inhibition.

Funding information:
  • NIGMS NIH HHS - T32 GM007104(United States)
  • NIMH NIH HHS - T32 MH096678(United States)

The Glia-Neuron Lactate Shuttle and Elevated ROS Promote Lipid Synthesis in Neurons and Lipid Droplet Accumulation in Glia via APOE/D.

  • Liu L
  • Cell Metab.
  • 2017 Nov 7

Literature context:


Abstract:

Elevated reactive oxygen species (ROS) induce the formation of lipids in neurons that are transferred to glia, where they form lipid droplets (LDs). We show that glial and neuronal monocarboxylate transporters (MCTs), fatty acid transport proteins (FATPs), and apolipoproteins are critical for glial LD formation. MCTs enable glia to secrete and neurons to absorb lactate, which is converted to pyruvate and acetyl-CoA in neurons. Lactate metabolites provide a substrate for synthesis of fatty acids, which are processed and transferred to glia by FATP and apolipoproteins. In the presence of high ROS, inhibiting lactate transfer or lowering FATP or apolipoprotein levels decreases glial LD accumulation in flies and in primary mouse glial-neuronal cultures. We show that human APOE can substitute for a fly glial apolipoprotein and that APOE4, an Alzheimer's disease susceptibility allele, is impaired in lipid transport and promotes neurodegeneration, providing insights into disease mechanisms.

Funding information:
  • NIAID NIH HHS - P30 AI036211()
  • NIGMS NIH HHS - R01 GM067858()
  • NIGMS NIH HHS - R01 GM084947()
  • NIGMS NIH HHS - R01 GM120033()

Prion-like transmission of α-synuclein pathology in the context of an NFL null background.

  • Rutherford NJ
  • Neurosci. Lett.
  • 2017 Nov 20

Literature context:


Abstract:

Neurofilaments are a major component of the axonal cytoskeleton in neurons and have been implicated in a number of neurodegenerative diseases due to their presence within characteristic pathological inclusions. Their contributions to these diseases are not yet fully understood, but previous studies investigated the effects of ablating the obligate subunit of neurofilaments, low molecular mass neurofilament subunit (NFL), on disease phenotypes in transgenic mouse models of Alzheimer's disease and tauopathy. Here, we tested the effects of ablating NFL in α-synuclein M83 transgenic mice expressing the human pathogenic A53T mutation, by breeding them onto an NFL null background. The induction and spread of α-synuclein inclusion pathology was triggered by the injection of preformed α-synuclein fibrils into the gastrocnemius muscle or hippocampus in M83 versus M83/NFL null mice. We observed no difference in the post-injection time to motor-impairment and paralysis endpoint or amount and distribution of α-synuclein inclusion pathology in the muscle injected M83 and M83/NFL null mice. Hippocampal injected M83/NFL null mice displayed subtle region-specific differences in the amount of α-synuclein inclusions however, pathology was observed in the same regions as the M83 mice. Overall, we observed only minor differences in the induction and transmission of α-synuclein pathology in these induced models of synucleinopathy in the presence or absence of NFL. This suggests that NFL and neurofilaments do not play a major role in influencing the induction and transmission of α-synuclein aggregation.

Pioneer Factors FOXA1 and FOXA2 Assist Selective Glucocorticoid Receptor Signaling in Human Endometrial Cells.

  • Whirledge S
  • Endocrinology
  • 2017 Nov 1

Literature context:


Abstract:

Successful pregnancy relies on dynamic control of cell signaling to achieve uterine receptivity and the necessary biological changes required for endometrial decidualization, embryo implantation, and fetal development. Glucocorticoids are master regulators of intracellular signaling and can directly regulate embryo implantation and endometrial remodeling during murine pregnancy. In immortalized human uterine cells, we have shown that glucocorticoids and estradiol (E2) coregulate thousands of genes. Recently, glucocorticoids and E2 were shown to coregulate the expression of Left-right determination factor 1 (LEFTY1), previously implicated in the regulation of decidualization. To elucidate the molecular mechanism by which glucocorticoids and E2 regulate the expression of LEFTY1, immortalized and primary human endometrial cells were evaluated for gene expression and receptor recruitment to regulatory regions of the LEFTY1 gene. Glucocorticoid administration induced expression of LEFTY1 messenger RNA and protein and recruitment of the glucocorticoid receptor (GR) and activated polymerase 2 to the promoter of LEFTY1. Glucocorticoid-mediated recruitment of GR was dependent on pioneer factors FOXA1 and FOXA2. E2 was found to antagonize glucocorticoid-mediated induction of LEFTY1 by reducing recruitment of GR, FOXA1, FOXA2, and activated polymerase 2 to the LEFTY1 promoter. Gene expression analysis identified several genes whose glucocorticoid-dependent induction required FOXA1 and FOXA2 in endometrial cells. These results suggest a molecular mechanism by which E2 antagonizes GR-dependent induction of specific genes by preventing the recruitment of the pioneer factors FOXA1 and FOXA2 in a physiologically relevant model.

Funding information:
  • NIMH NIH HHS - R01 MH084989(United States)

Long-Chain Omega-3 Fatty Acids Supplementation Accelerates Nerve Regeneration and Prevents Neuropathic Pain Behavior in Mice.

  • Silva RV
  • Front Pharmacol
  • 2017 Nov 2

Literature context:


Abstract:

Fish oil (FO) is the main source of long chain omega-3 polyunsaturated fatty acids (ω-3 PUFAs), which display relevant analgesic and anti-inflammatory properties. Peripheral nerve injury is driven by degeneration, neuroinflammation, and neuronal plasticity which results in neuropathic pain (NP) symptoms such as allodynia and hyperalgesia. We tested the preventive effect of an EPA/DHA-concentrate fish oil (CFO) on NP development and regenerative features. Swiss mice received daily oral treatment with CFO 4.6 or 2.3 g/kg for 10 days after NP was induced by partial sciatic nerve ligation. Mechanical allodynia and thermal hypernociception were assessed 5 days after injury. CFO 2.3 g/kg significantly prevented mechanical and thermal sensitization, reduced TNF levels in the spinal cord, sciatic MPO activity, and ATF-3 expression on DRG cells. CFO improved Sciatic Functional Index (SFI) as well as electrophysiological recordings, corroborating the increased GAP43 expression and total number of myelinated fibers observed in sciatic nerve. No locomotor activity impairment was observed in CFO treated groups. These results point to the regenerative and possibly protective properties of a combined EPA and DHA oral administration after peripheral nerve injury, as well as its anti-neuroinflammatory activity, evidencing ω-3 PUFAs promising therapeutic outcomes for NP treatment.

The conserved RNA helicase YTHDC2 regulates the transition from proliferation to differentiation in the germline.

  • Bailey AS
  • Elife
  • 2017 Oct 31

Literature context:


Abstract:

The switch from mitosis to meiosis is the key event marking onset of differentiation in the germline stem cell lineage. In Drosophila, the translational repressor Bgcn is required for spermatogonia to stop mitosis and transition to meiotic prophase and the spermatocyte state. Here we show that the mammalian Bgcn homolog YTHDC2 facilitates a clean switch from mitosis to meiosis in mouse germ cells, revealing a conserved role for YTHDC2 in this critical cell fate transition. YTHDC2-deficient male germ cells enter meiosis but have a mixed identity, maintaining expression of Cyclin A2 and failing to properly express many meiotic markers. Instead of continuing through meiotic prophase, the cells attempt an abnormal mitotic-like division and die. YTHDC2 binds multiple transcripts including Ccna2 and other mitotic transcripts, binds specific piRNA precursors, and interacts with RNA granule components, suggesting that proper progression of germ cells through meiosis is licensed by YTHDC2 through post-transcriptional regulation.

Ubiquitin Linkage-Specific Affimers Reveal Insights into K6-Linked Ubiquitin Signaling.

  • Michel MA
  • Mol. Cell
  • 2017 Oct 5

Literature context:


Abstract:

Several ubiquitin chain types have remained unstudied, mainly because tools and techniques to detect these posttranslational modifications are scarce. Linkage-specific antibodies have shaped our understanding of the roles and dynamics of polyubiquitin signals but are available for only five out of eight linkage types. We here characterize K6- and K33-linkage-specific "affimer" reagents as high-affinity ubiquitin interactors. Crystal structures of affimers bound to their cognate chain types reveal mechanisms of specificity and a K11 cross-reactivity in the K33 affimer. Structure-guided improvements yield superior affinity reagents suitable for western blotting, confocal fluorescence microscopy and pull-down applications. This allowed us to identify RNF144A and RNF144B as E3 ligases that assemble K6-, K11-, and K48-linked polyubiquitin in vitro. A protocol to enrich K6-ubiquitinated proteins from cells identifies HUWE1 as a main E3 ligase for this chain type, and we show that mitofusin-2 is modified with K6-linked polyubiquitin in a HUWE1-dependent manner.

Funding information:
  • European Research Council - 309756()

Structural Basis of Mec1-Ddc2-RPA Assembly and Activation on Single-Stranded DNA at Sites of Damage.

  • Deshpande I
  • Mol. Cell
  • 2017 Oct 19

Literature context:


Abstract:

Mec1-Ddc2 (ATR-ATRIP) is a key DNA-damage-sensing kinase that is recruited through the single-stranded (ss) DNA-binding replication protein A (RPA) to initiate the DNA damage checkpoint response. Activation of ATR-ATRIP in the absence of DNA damage is lethal. Therefore, it is important that damage-specific recruitment precedes kinase activation, which is achieved at least in part by Mec1-Ddc2 homodimerization. Here, we report a structural, biochemical, and functional characterization of the yeast Mec1-Ddc2-RPA assembly. High-resolution co-crystal structures of Ddc2-Rfa1 and Ddc2-Rfa1-t11 (K45E mutant) N termini and of the Ddc2 coiled-coil domain (CCD) provide insight into Mec1-Ddc2 homodimerization and damage-site targeting. Based on our structural and functional findings, we present a Mec1-Ddc2-RPA-ssDNA composite structural model. By way of validation, we show that RPA-dependent recruitment of Mec1-Ddc2 is crucial for maintaining its homodimeric state at ssDNA and that Ddc2's recruitment domain and CCD are important for Mec1-dependent survival of UV-light-induced DNA damage.

Reck and Gpr124 Are Essential Receptor Cofactors for Wnt7a/Wnt7b-Specific Signaling in Mammalian CNS Angiogenesis and Blood-Brain Barrier Regulation.

  • Cho C
  • Neuron
  • 2017 Aug 30

Literature context:


Abstract:

Reck, a GPI-anchored membrane protein, and Gpr124, an orphan GPCR, have been implicated in Wnt7a/Wnt7b signaling in the CNS vasculature. We show here that vascular endothelial cell (EC)-specific reduction in Reck impairs CNS angiogenesis and that EC-specific postnatal loss of Reck, combined with loss of Norrin, impairs blood-brain barrier (BBB) maintenance. The most N-terminal domain of Reck binds to the leucine-rich repeat (LRR) and immunoglobulin (Ig) domains of Gpr124, and weakening this interaction by targeted mutagenesis reduces Reck/Gpr124 stimulation of Wnt7a signaling in cell culture and impairs CNS angiogenesis. Finally, a soluble Gpr124(LRR-Ig) probe binds to cells expressing Frizzled, Wnt7a or Wnt7b, and Reck, and a soluble Reck(CC1-5) probe binds to cells expressing Frizzled, Wnt7a or Wnt7b, and Gpr124. These experiments indicate that Reck and Gpr124 are part of the cell surface protein complex that transduces Wnt7a- and Wnt7b-specific signals in mammalian CNS ECs to promote angiogenesis and regulate the BBB.

Amplification of F-Actin Disassembly and Cellular Repulsion by Growth Factor Signaling.

  • Yoon J
  • Dev. Cell
  • 2017 Jul 24

Literature context:


Abstract:

Extracellular cues that regulate cellular shape, motility, and navigation are generally classified as growth promoting (i.e., growth factors/chemoattractants and attractive guidance cues) or growth preventing (i.e., repellents and inhibitors). Yet, these designations are often based on complex assays and undefined signaling pathways and thus may misrepresent direct roles of specific cues. Here, we find that a recognized growth-promoting signaling pathway amplifies the F-actin disassembly and repulsive effects of a growth-preventing pathway. Focusing on Semaphorin/Plexin repulsion, we identified an interaction between the F-actin-disassembly enzyme Mical and the Abl tyrosine kinase. Biochemical assays revealed Abl phosphorylates Mical to directly amplify Mical Redox-mediated F-actin disassembly. Genetic assays revealed that Abl allows growth factors and Semaphorin/Plexin repellents to combinatorially increase Mical-mediated F-actin disassembly, cellular remodeling, and repulsive axon guidance. Similar roles for Mical in growth factor/Abl-related cancer cell behaviors further revealed contexts in which characterized positive effectors of growth/guidance stimulate such negative cellular effects as F-actin disassembly/repulsion.

Funding information:
  • NIMH NIH HHS - R01 MH085923()

Epidermal growth factor signals attenuate phenotypic and functional development of neocortical GABA neurons.

  • Namba H
  • J. Neurochem.
  • 2017 Jun 13

Literature context:


Abstract:

Phenotypic development of neocortical GABA neurons is highly plastic and promoted by various neurotrophic factors such as neuregulin-1. A subpopulation of GABA neurons expresses not only neuregulin receptor (ErbB4) but also epidermal growth factor (EGF) receptor (ErbB1) during development, but the neurobiological action of EGF on this cell population is less understood than that of neuregulin-1. Here, we examined the effects of exogenous EGF on immature GABA neurons both in culture and in vivo and also explored physiological consequences in adults. We prepared low density cultures from the neocortex of rat embryos and treated neocortical neurons with EGF. EGF decreased protein levels of glutamic acid decarboxylases (GAD65 and GAD67), and EGF influences on neuronal survival and glial proliferation were negligible or limited. The EGF treatment also diminished the frequency of miniature inhibitory postsynaptic currents (mIPSCs). In vivo administration of EGF to mouse pups reproduced the above GABAergic phenomena in neocortical culture. In EGF-injected postnatal mice, GAD- and parvalbumin-immunoreactivities were reduced in the frontal cortex. In addition, postnatal EGF treatment decreased mIPSC frequency in, and the density of, GABAergic terminals on pyramidal cells. Although these phenotypic influences on GABA neurons became less marked during development, it later resulted in the reduced β- and γ-powers of sound-evoked electroencephalogram in adults, which is regulated by parvalbumin-positive GABA neurons and implicated in the schizophrenia pathophysiology. These findings suggest that, in contrast to the ErbB4 ligand of neuregulin-1, the ErbB1 ligand of EGF exerts unique maturation-attenuating influences on developing cortical GABAergic neurons.

Funding information:
  • Wellcome Trust - 090108/Z/09/Z(United Kingdom)

Dynamic Palmitoylation Targets MAP6 to the Axon to Promote Microtubule Stabilization during Neuronal Polarization.

  • Tortosa E
  • Neuron
  • 2017 May 17

Literature context:


Abstract:

Microtubule-associated proteins (MAPs) are main candidates to stabilize neuronal microtubules, playing an important role in establishing axon-dendrite polarity. However, how MAPs are selectively targeted to specific neuronal compartments remains poorly understood. Here, we show specific localization of microtubule-associated protein 6 (MAP6)/stable tubule-only polypeptide (STOP) throughout neuronal maturation and its role in axonal development. In unpolarized neurons, MAP6 is present at the Golgi complex and in secretory vesicles. As neurons mature, MAP6 is translocated to the proximal axon, where it binds and stabilizes microtubules. Further, we demonstrate that dynamic palmitoylation, mediated by the family of α/β Hydrolase domain-containing protein 17 (ABHD17A-C) depalmitoylating enzymes, controls shuttling of MAP6 between membranes and microtubules and is required for MAP6 retention in axons. We propose a model in which MAP6's palmitoylation mediates microtubule stabilization, allows efficient organelle trafficking, and controls axon maturation in vitro and in situ.

Elucidation of the anti-autophagy mechanism of the Legionella effector RavZ using semisynthetic LC3 proteins.

  • Yang A
  • Elife
  • 2017 Apr 11

Literature context:


Abstract:

Autophagy is a conserved cellular process involved in the elimination of proteins and organelles. It is also used to combat infection with pathogenic microbes. The intracellular pathogen Legionella pneumophila manipulates autophagy by delivering the effector protein RavZ to deconjugate Atg8/LC3 proteins coupled to phosphatidylethanolamine (PE) on autophagosomal membranes. To understand how RavZ recognizes and deconjugates LC3-PE, we prepared semisynthetic LC3 proteins and elucidated the structures of the RavZ:LC3 interaction. Semisynthetic LC3 proteins allowed the analysis of structure-function relationships. RavZ extracts LC3-PE from the membrane before deconjugation. RavZ initially recognizes the LC3 molecule on membranes via its N-terminal LC3-interacting region (LIR) motif. The RavZ α3 helix is involved in extraction of the PE moiety and docking of the acyl chains into the lipid-binding site of RavZ that is related in structure to that of the phospholipid transfer protein Sec14. Thus, Legionella has evolved a novel mechanism to specifically evade host autophagy.

Ubiquitin Ligase RNF138 Promotes Episodic Ataxia Type 2-Associated Aberrant Degradation of Human Cav2.1 (P/Q-Type) Calcium Channels.

  • Fu SJ
  • J. Neurosci.
  • 2017 Mar 1

Literature context:


Abstract:

Voltage-gated CaV2.1 channels comprise a pore-forming α1A subunit with auxiliary α2δ and β subunits. CaV2.1 channels play an essential role in regulating synaptic signaling. Mutations in the human gene encoding the CaV2.1 subunit are associated with the cerebellar disease episodic ataxia type 2 (EA2). Several EA2-causing mutants exhibit impaired protein stability and exert dominant-negative suppression of CaV2.1 wild-type (WT) protein expression via aberrant proteasomal degradation. Here, we set out to delineate the protein degradation mechanism of human CaV2.1 subunit by identifying RNF138, an E3 ubiquitin ligase, as a novel CaV2.1-binding partner. In neurons, RNF138 and CaV2.1 coexist in the same protein complex and display notable subcellular colocalization at presynaptic and postsynaptic regions. Overexpression of RNF138 promotes polyubiquitination and accelerates protein turnover of CaV2.1. Disrupting endogenous RNF138 function with a mutant (RNF138-H36E) or shRNA infection significantly upregulates the CaV2.1 protein level and enhances CaV2.1 protein stability. Disrupting endogenous RNF138 function also effectively rescues the defective protein expression of EA2 mutants, as well as fully reversing EA2 mutant-induced excessive proteasomal degradation of CaV2.1 WT subunits. RNF138-H36E coexpression only partially restores the dominant-negative effect of EA2 mutants on CaV2.1 WT functional expression, which can be attributed to defective membrane trafficking of CaV2.1 WT in the presence of EA2 mutants. We propose that RNF138 plays a critical role in the homeostatic regulation of CaV2.1 protein level and functional expression and that RNF138 serves as the primary E3 ubiquitin ligase promoting EA2-associated aberrant degradation of human CaV2.1 subunits.SIGNIFICANCE STATEMENT Loss-of-function mutations in the human CaV2.1 subunit are linked to episodic ataxia type 2 (EA2), a dominantly inherited disease characterized by paroxysmal attacks of ataxia and nystagmus. EA2-causing mutants may exert dominant-negative effects on the CaV2.1 wild-type subunit via aberrant proteasomal degradation. The molecular nature of the CaV2.1 ubiquitin-proteasome degradation pathway is currently unknown. The present study reports the first identification of an E3 ubiquitin ligase for CaV2.1, RNF138. CaV2.1 protein stability is dynamically regulated by RNF138 and auxiliary α2δ and β subunits. We provide a proof of concept that protecting the human CaV2.1 subunit from excessive proteasomal degradation with specific interruption of endogenous RNF138 function may partially contribute to the future development of a novel therapeutic strategy for EA2 patients.

Selective Chemical Inhibition of PGC-1α Gluconeogenic Activity Ameliorates Type 2 Diabetes.

  • Sharabi K
  • Cell
  • 2017 Mar 23

Literature context:


Abstract:

Type 2 diabetes (T2D) is a worldwide epidemic with a medical need for additional targeted therapies. Suppression of hepatic glucose production (HGP) effectively ameliorates diabetes and can be exploited for its treatment. We hypothesized that targeting PGC-1α acetylation in the liver, a chemical modification known to inhibit hepatic gluconeogenesis, could be potentially used for treatment of T2D. Thus, we designed a high-throughput chemical screen platform to quantify PGC-1α acetylation in cells and identified small molecules that increase PGC-1α acetylation, suppress gluconeogenic gene expression, and reduce glucose production in hepatocytes. On the basis of potency and bioavailability, we selected a small molecule, SR-18292, that reduces blood glucose, strongly increases hepatic insulin sensitivity, and improves glucose homeostasis in dietary and genetic mouse models of T2D. These studies have important implications for understanding the regulatory mechanisms of glucose metabolism and treatment of T2D.

Funding information:
  • NHGRI NIH HHS - U54 HG005032()
  • NIDA NIH HHS - R03 DA032468()
  • NIDDK NIH HHS - F32 DK102293()
  • NIDDK NIH HHS - R01 DK040936()
  • NIDDK NIH HHS - R01 DK069966()
  • NIDDK NIH HHS - R24 DK080261()
  • NIDDK NIH HHS - U2C DK059635()

GARLH Family Proteins Stabilize GABAA Receptors at Synapses.

  • Yamasaki T
  • Neuron
  • 2017 Mar 8

Literature context:


Abstract:

Ionotropic neurotransmitter receptors mediate fast synaptic transmission by functioning as ligand-gated ion channels. Fast inhibitory transmission in the brain is mediated mostly by ionotropic GABAA receptors (GABAARs), but their essential components for synaptic localization remain unknown. Here, we identify putative auxiliary subunits of GABAARs, which we term GARLHs, consisting of LH4 and LH3 proteins. LH4 forms a stable tripartite complex with GABAARs and neuroligin-2 in the brain. Moreover, LH4 is required for the synaptic localization of GABAARs and inhibitory synaptic transmission in the hippocampus. Our findings propose GARLHs as the first identified auxiliary subunits for anion channels. These findings provide new insights into the regulation of inhibitory transmission and the molecular constituents of native anion channels in vivo.

Funding information:
  • NCATS NIH HHS - UL1 TR001863()
  • NIGMS NIH HHS - T32 GM007205()
  • NIMH NIH HHS - F30 MH099742()
  • NIMH NIH HHS - U01 MH104984()
  • NINDS NIH HHS - U24 NS050606()

LIN41 Post-transcriptionally Silences mRNAs by Two Distinct and Position-Dependent Mechanisms.

  • Aeschimann F
  • Mol. Cell
  • 2017 Feb 2

Literature context:


Abstract:

The RNA-binding protein (RBP) LIN41, also known as LIN-41 or TRIM71, is a key regulator of animal development, but its physiological targets and molecular mechanism of action are largely elusive. Here we find that this RBP has two distinct mRNA-silencing activities. Using genome-wide ribosome profiling, RNA immunoprecipitation, and in vitro-binding experiments, we identify four mRNAs, each encoding a transcription factor or cofactor, as direct physiological targets of C. elegans LIN41. LIN41 silences three of these targets through their 3' UTRs, but it achieves isoform-specific silencing of one target, lin-29A, through its unique 5' UTR. Whereas the 3' UTR targets mab-10, mab-3, and dmd-3 undergo transcript degradation, lin-29A experiences translational repression. Through binding site transplantation experiments, we demonstrate that it is the location of the LIN41-binding site that specifies the silencing mechanism. Such position-dependent dual activity may, when studied more systematically, emerge as a feature shared by other RBPs.

FGF13 Selectively Regulates Heat Nociception by Interacting with Nav1.7.

  • Yang L
  • Neuron
  • 2017 Feb 22

Literature context:


Abstract:

The current knowledge about heat nociception is mainly confined to the thermosensors, including the transient receptor potential cation channel V1 expressed in the nociceptive neurons of dorsal root ganglion (DRG). However, the loss of thermosensors only partially impairs heat nociception, suggesting the existence of undiscovered mechanisms. We found that the loss of an intracellular fibroblast growth factor (FGF), FGF13, in the mouse DRG neurons selectively abolished heat nociception. The noxious heat stimuli could not evoke the sustained action potential firing in FGF13-deficient DRG neurons. Furthermore, FGF13 interacted with the sodium channel Nav1.7 in a heat-facilitated manner. FGF13 increased Nav1.7 sodium currents and maintained the membrane localization of Nav1.7 during noxious heat stimulation, enabling the sustained firing of action potentials. Disrupting the FGF13/Nav1.7 interaction reduced the heat-evoked action potential firing and nociceptive behavior. Thus, beyond the thermosensors, the FGF13/Nav1.7 complex is essential for sustaining the transmission of noxious heat signals.

Elimination of paternal mitochondria in mouse embryos occurs through autophagic degradation dependent on PARKIN and MUL1.

  • Rojansky R
  • Elife
  • 2016 Nov 17

Literature context:


Abstract:

A defining feature of mitochondria is their maternal mode of inheritance. However, little is understood about the cellular mechanism through which paternal mitochondria, delivered from sperm, are eliminated from early mammalian embryos. Autophagy has been implicated in nematodes, but whether this mechanism is conserved in mammals has been disputed. Here, we show that cultured mouse fibroblasts and pre-implantation embryos use a common pathway for elimination of mitochondria. Both situations utilize mitophagy, in which mitochondria are sequestered by autophagosomes and delivered to lysosomes for degradation. The E3 ubiquitin ligases PARKIN and MUL1 play redundant roles in elimination of paternal mitochondria. The process is associated with depolarization of paternal mitochondria and additionally requires the mitochondrial outer membrane protein FIS1, the autophagy adaptor P62, and PINK1 kinase. Our results indicate that strict maternal transmission of mitochondria relies on mitophagy and uncover a collaboration between MUL1 and PARKIN in this process.

Soluble Conformers of Aβ and Tau Alter Selective Proteins Governing Axonal Transport.

  • Sherman MA
  • J. Neurosci.
  • 2016 Sep 14

Literature context:


Abstract:

Despite the demonstration that amyloid-β (Aβ) can trigger increased tau phosphorylation and neurofibrillary tangle (NFT) formation in vivo, the molecular link associating Aβ and tau pathologies remains ill defined. Here, we observed that exposure of cultured primary neurons to Aβ trimers isolated from brain tissue of subjects with Alzheimer's disease led to a specific conformational change of tau detected by the antibody Alz50. A similar association was supported by postmortem human brain analyses. To study the role of Aβ trimers in vivo, we created a novel bigenic Tg-Aβ+Tau mouse line by crossing Tg2576 (Tg-Aβ) and rTg4510 (Tg-Tau) mice. Before neurodegeneration and amyloidosis, apparent Aβ trimers were increased by ∼2-fold in 3-month-old Tg-Aβ and Tg-Aβ+Tau mice compared with younger mice, whereas soluble monomeric Aβ levels were unchanged. Under these conditions, the expression of soluble Alz50-tau conformers rose by ∼2.2-fold in the forebrains of Tg-Aβ+Tau mice compared with nontransgenic littermates. In parallel, APP accumulated intracellularly, suggestive of a putative dysfunction of anterograde axonal transport. We found that the protein abundance of the kinesin-1 light chain (KLC1) was reduced selectively in vivo and in vitro when soluble Aβ trimers/Alz50-tau were present. Importantly, the reduction in KLC1 was prevented by the intraneuronal delivery of Alz50 antibodies. Collectively, our findings reveal that specific soluble conformers of Aβ and tau cooperatively disrupt axonal transport independently from plaques and tangles. Finally, these results suggest that not all endogenous Aβ oligomers trigger the same deleterious changes and that the role of each assembly should be considered separately. SIGNIFICANCE STATEMENT: The mechanistic link between amyloid-β (Aβ) and tau, the two major proteins composing the neuropathological lesions detected in brain tissue of Alzheimer's disease subjects, remains unclear. Here, we report that the trimeric Aβ species induce a pathological modification of tau in cultured neurons and in bigenic mice expressing Aβ and human tau. This linkage was also observed in postmortem brain tissue from subjects with mild cognitive impairment, when Aβ trimers are abundant. Further, this modification of tau was associated with the intracellular accumulation of the precursor protein of Aβ, APP, as a result of the selective decrease in kinesin light chain 1 expression. Our findings suggest that Aβ trimers might cause axonal transport deficits in AD.

Muscle cell identity requires Pax7-mediated lineage-specific DNA demethylation.

  • Carrió E
  • BMC Biol.
  • 2016 Apr 13

Literature context:


Abstract:

BACKGROUND: Skeletal muscle stem cells enable the formation, growth, maintenance, and regeneration of skeletal muscle throughout life. The regeneration process is compromised in several pathological conditions, and muscle progenitors derived from pluripotent stem cells have been suggested as a potential therapeutic source for tissue replacement. DNA methylation is an important epigenetic mechanism in the setting and maintenance of cellular identity, but its role in stem cell determination towards the myogenic lineage is unknown. Here we addressed the DNA methylation dynamics of the major genes orchestrating the myogenic determination and differentiation programs in embryonic stem (ES) cells, their Pax7-induced myogenic derivatives, and muscle stem cells in proliferating and differentiating conditions. RESULTS: Our data showed a common muscle-specific DNA demethylation signature required to acquire and maintain the muscle-cell identity. This specific-DNA demethylation is Pax7-mediated, and it is a prime event in muscle stem cells gene activation. Notably, downregulation of the demethylation-related enzyme Apobec2 in ES-derived myogenic precursors reduced myogenin-associated DNA demethylation and dramatically impaired the expression of differentiation markers and, ultimately, muscle differentiation. CONCLUSIONS: Our results underscore DNA demethylation as a key mechanism driving myogenesis and identify specific Pax7-mediated DNA demethylation signatures to acquire and maintain the muscle-cell identity. Additionally, we provide a panel of epigenetic markers for the efficient and safe generation of ES- and induced pluripotent stem cell (iPS)-derived myogenic progenitors for therapeutic applications.

Funding information:
  • NCI NIH HHS - U54 CA143874(United States)

Long-Acting PASylated Leptin Ameliorates Obesity by Promoting Satiety and Preventing Hypometabolism in Leptin-Deficient Lep(ob/ob) Mice.

  • Bolze F
  • Endocrinology
  • 2016 Jan 31

Literature context:


Abstract:

Body weight loss of Lep(ob/ob) mice in response to leptin is larger than expected from the reduction in energy intake alone, suggesting a thermogenic action of unknown magnitude. We exploited the superior pharmacological properties of a novel long-acting leptin prepared via PASylation to study the contribution of its anorexigenic and thermogenic effects. PASylation, the genetic fusion of leptin with a conformationally disordered polypeptide comprising 600 Pro/Ala/Ser (PAS) residues, provides a superior way to increase the hydrodynamic volume of the fusion protein, thus retarding kidney filtration and extending plasma half-life. Here a single PAS(600)-leptin injection (300 pmol/g) resulted in a maximal weight reduction of 21% 6 days after application. The negative energy balance of 300 kJ/(4 d) was driven by a decrease in energy intake, whereas energy expenditure remained stable. Mice that were food restricted to the same extent showed an energy deficit of only 220 kJ/(4 d) owing to recurring torpor bouts. Therefore, the anorexigenic effect of PAS(600)-leptin contributes 75% to weight loss, whereas the thermogenic action accounts for 25% by preventing hypometabolism. In a second experiment, just four injections of PAS(600)-leptin (100 pmol/g) administered in 5- to 6-day intervals rectified the Lep(ob/ob) phenotype. In total, 16 nmol of PAS(600)-leptin per mouse triggered a weight loss of 43% within 20 days and normalized hypothermia and glucose homeostasis as well as hepatic steatosis. The beneficial properties of PAS(600)-leptin are substantiated by a comparison with previous studies in which approximately 400 nmol (∼25-fold) unmodified leptin was mandatory to achieve similar improvements.

Funding information:
  • Biotechnology and Biological Sciences Research Council - R01 DK080339(United Kingdom)
  • NHLBI NIH HHS - R01 HL077681(United States)

Anti-Müllerian Hormone Is a Marker for Chemotherapy-Induced Testicular Toxicity.

  • Levi M
  • Endocrinology
  • 2015 Oct 19

Literature context:


Abstract:

Due to increased numbers of young cancer patients and improved survival, the impact of anticancer treatments on fertility has become a major health concern. Despite mounting research on ovarian toxicity, there is paucity of data regarding reliable biomarkers of testicular toxicity. Our aim was to evaluate anti-Müllerian hormone (AMH) as a marker for chemotherapy-induced testicular toxicity. Serum AMH and a panel of gonadal hormones were measured in male cancer patients at baseline and after chemotherapy. In the preclinical setting, mice were injected with diverse chemotherapies and were killed 1 week or 1, 3, or 6 months later. We evaluated spermatogenesis by AMH as well as qualitative and quantitative sperm parameters. Nineteen patients were enrolled, the median age was 38 years (21-44 y). Serum AMH was correlated with increased FSH and T and decreased inhibin-B in gonadotoxic protocols (cisplatin or busulfan) and remained unchanged in nongonadotoxic protocols (capecitabine). AMH expression had the same pattern in mice serum and testes; it was negatively correlated with testicular/epididymal weight and sperm motility. The increase in testicular AMH expression was also correlated with elevated apoptosis (terminal transferase-mediated deoxyuridine 5-triphosphate nick-end labeling) and reduced proliferation (Ki67, proliferating cell nuclear antigen; all seminiferous tubules cells were analyzed). Severely damaged mice testes demonstrated a marked costaining of AMH and GATA-4, a Sertoli cell marker; staining that resembled the pattern of the Sertoli cell-only condition. Our study indicates that the pattern of serum AMH expression, in combination with other hormones, can delineate testicular damage, as determined in both experimental settings. Future large-scale clinical studies are warranted to further define the role of AMH as a biomarker for testicular toxicity.

Funding information:
  • NIDDK NIH HHS - R01 DK075618(United States)
  • NIGMS NIH HHS - R01 GM117090(United States)

Differential contributions of microglial and neuronal IKKβ to synaptic plasticity and associative learning in alert behaving mice.

  • Kyrargyri V
  • Glia
  • 2015 Apr 16

Literature context:


Abstract:

Microglia are CNS resident immune cells and a rich source of neuroactive mediators, but their contribution to physiological brain processes such as synaptic plasticity, learning, and memory is not fully understood. In this study, we used mice with partial depletion of IκB kinase β, the main activating kinase in the inducible NF-κB pathway, selectively in myeloid lineage cells (mIKKβKO) or excitatory neurons (nIKKβKO) to measure synaptic strength at hippocampal Schaffer collaterals during long-term potentiation (LTP) and instrumental conditioning in alert behaving individuals. Resting microglial cells in mIKKβKO mice showed less Iba1-immunoreactivity, and brain IL-1β mRNA levels were selectively reduced compared with controls. Measurement of field excitatory postsynaptic potentials (fEPSPs) evoked by stimulation of the CA3-CA1 synapse in mIKKβKO mice showed higher facilitation in response to paired pulses and enhanced LTP following high frequency stimulation. In contrast, nIKKβKO mice showed normal basic synaptic transmission and LTP induction but impairments in late LTP. To understand the consequences of such impairments in synaptic plasticity for learning and memory, we measured CA1 fEPSPs in behaving mice during instrumental conditioning. IKKβ was not necessary in either microglia or neurons for mice to learn lever-pressing (appetitive behavior) to obtain food (consummatory behavior) but was required in both for modification of their hippocampus-dependent appetitive, not consummatory behavior. Our results show that microglia, through IKKβ and therefore NF-κB activity, regulate hippocampal synaptic plasticity and that both microglia and neurons, through IKKβ, are necessary for animals to modify hippocampus-driven behavior during associative learning.

PAT1 inversely regulates the surface Amyloid Precursor Protein level in mouse primary neurons.

  • Dilsizoglu Senol A
  • BMC Neurosci
  • 2015 Mar 7

Literature context:


Abstract:

BACKGROUND: The amyloid precursor protein (APP) is a key molecule in Alzheimer disease. Its localization at the cell surface can trigger downstream signaling and APP cleavages. APP trafficking to the cell surface in neurons is not clearly understood and may be related to the interactions with its partners. In this respect, by having homologies with kinesin light chain domains and because of its capacity to bind APP, PAT1 represents a good candidate. RESULTS: We observed that PAT1 binds poorly APP at the cell surface of primary cortical neurons contrary to cytoplasmic APP. Using down and up-regulation of PAT1, we observed respectively an increase and decrease of APP at the cell surface. The increase of APP at the cell surface induced by low levels of PAT1 did not trigger cell death signaling. CONCLUSIONS: These data suggest that PAT1 slows down APP trafficking to the cell surface in primary cortical neurons. Our results contribute to the elucidation of mechanisms involved in APP trafficking in Alzheimer disease.

Funding information:
  • NEI NIH HHS - 5-T32EY013360-13(United States)
  • NIDCD NIH HHS - F32 DC000210(United States)

Cadherin-8 expression, synaptic localization, and molecular control of neuronal form in prefrontal corticostriatal circuits.

  • Friedman LG
  • J. Comp. Neurol.
  • 2015 Jan 1

Literature context:


Abstract:

Neocortical interactions with the dorsal striatum support many motor and executive functions, and such underlying functional networks are particularly vulnerable to a variety of developmental, neurological, and psychiatric brain disorders, including autism spectrum disorders, Parkinson's disease, and Huntington's disease. Relatively little is known about the development of functional corticostriatal interactions, and in particular, virtually nothing is known of the molecular mechanisms that control generation of prefrontal cortex-striatal circuits. Here, we used regional and cellular in situ hybridization techniques coupled with neuronal tract tracing to show that Cadherin-8 (Cdh8), a homophilic adhesion protein encoded by a gene associated with autism spectrum disorders and learning disability susceptibility, is enriched within striatal projection neurons in the medial prefrontal cortex and in striatal medium spiny neurons forming the direct or indirect pathways. Developmental analysis of quantitative real-time polymerase chain reaction and western blot data show that Cdh8 expression peaks in the prefrontal cortex and striatum at P10, when cortical projections start to form synapses in the striatum. High-resolution immunoelectron microscopy shows that Cdh8 is concentrated at excitatory synapses in the dorsal striatum, and Cdh8 knockdown in cortical neurons impairs dendritic arborization and dendrite self-avoidance. Taken together, our findings indicate that Cdh8 delineates developing corticostriatal circuits where it is a strong candidate for regulating the generation of normal cortical projections, neuronal morphology, and corticostriatal synapses.

Social interaction rescues memory deficit in an animal model of Alzheimer's disease by increasing BDNF-dependent hippocampal neurogenesis.

  • Hsiao YH
  • J. Neurosci.
  • 2014 Dec 3

Literature context:


Abstract:

It has been recognized that the risk of cognitive decline during aging can be reduced if one maintains strong social connections, yet the neural events underlying this beneficial effect have not been rigorously studied. Here, we show that amyloid precursor protein (APP) and presenilin 1 (PS1) double-transgenic (APP/PS1) mice demonstrate improvement in memory after they are cohoused with wild-type mice. The improvement was associated with increased protein and mRNA levels of BDNF in the hippocampus. Concomitantly, the number of BrdU(+)/NeuN(+) cells in the hippocampal dentate gyrus was significantly elevated after cohousing. Methylazoxymethanol acetate, a cell proliferation blocker, markedly reduced BrdU(+) and BrdU/NeuN(+) cells and abolished the effect of social interaction. Selective ablation of mitotic neurons using diphtheria toxin (DT) and a retrovirus vector encoding DT receptor abolished the beneficial effect of cohousing. Knockdown of BDNF by shRNA transfection blocked, whereas overexpression of BDNF mimicked the memory-improving effect. A tropomyosin-related kinase B agonist, 7,8-dihydroxyflavone, occluded the effect of social interaction. These results demonstrate that increased BDNF expression and neurogenesis in the hippocampus after cohousing underlie the reversal of memory deficit in APP/PS1 mice.

Funding information:
  • NEI NIH HHS - R01 EY020578(United States)
  • NIDCR NIH HHS - R01 DE023090(United States)

Clarin-1 acts as a modulator of mechanotransduction activity and presynaptic ribbon assembly.

  • Ogun O
  • J. Cell Biol.
  • 2014 Nov 10

Literature context:


Abstract:

Clarin-1 is a four-transmembrane protein expressed by hair cells and photoreceptors. Mutations in its corresponding gene are associated with Usher syndrome type 3, characterized by late-onset and progressive hearing and vision loss in humans. Mice carrying mutations in the clarin-1 gene have hair bundle dysmorphology and a delay in synapse maturation. In this paper, we examined the expression and function of clarin-1 in zebrafish hair cells. We observed protein expression as early as 1 d postfertilization. Knockdown of clarin-1 resulted in inhibition of FM1-43 incorporation, shortening of the kinocilia, and mislocalization of ribeye b clusters. These phenotypes were fully prevented by co-injection with clarin-1 transcript, requiring its C-terminal tail. We also observed an in vivo interaction between clarin-1 and Pcdh15a. Altogether, our results suggest that clarin-1 is functionally important for mechanotransduction channel activity and for proper localization of synaptic components, establishing a critical role for clarin-1 at the apical and basal poles of hair cells.

Inhibition of adenylyl cyclase type 5 prevents L-DOPA-induced dyskinesia in an animal model of Parkinson's disease.

  • Park HY
  • J. Neurosci.
  • 2014 Aug 27

Literature context:


Abstract:

The dopamine precursor L-3,4-dihydroxyphenylalanine (L-DOPA) is widely used as a therapeutic choice for the treatment of patients with Parkinson's disease. However, the long-term use of L-DOPA leads to the development of debilitating involuntary movements, called L-DOPA-induced dyskinesia (LID). The cAMP/protein kinase A (PKA) signaling in the striatum is known to play a role in LID. However, from among the nine known adenylyl cyclases (ACs) present in the striatum, the AC that mediates LID remains unknown. To address this issue, we prepared an animal model with unilateral 6-hydroxydopamine lesions in the substantia nigra in wild-type and AC5-knock-out (KO) mice, and examined behavioral responses to short-term or long-term treatment with L-DOPA. Compared with the behavioral responses of wild-type mice, LID was profoundly reduced in AC5-KO mice. The behavioral protection of long-term treatment with L-DOPA in AC5-KO mice was preceded by a decrease in the phosphorylation levels of PKA substrates ERK (extracellular signal-regulated kinase) 1/2, MSK1 (mitogen- and stress-activated protein kinase 1), and histone H3, levels of which were all increased in the lesioned striatum of wild-type mice. Consistently, FosB/ΔFosB expression, which was induced by long-term L-DOPA treatment in the lesioned striatum, was also decreased in AC5-KO mice. Moreover, suppression of AC5 in the dorsal striatum with lentivirus-shRNA-AC5 was sufficient to attenuate LID, suggesting that the AC5-regulated signaling cascade in the striatum mediates LID. These results identify the AC5/cAMP system in the dorsal striatum as a therapeutic target for the treatment of LID in patients with Parkinson's disease.

TCTP is essential for β-cell proliferation and mass expansion during development and β-cell adaptation in response to insulin resistance.

  • Tsai MJ
  • Endocrinology
  • 2014 Feb 22

Literature context:


Abstract:

The perinatal period is critical for β-cell mass establishment, which is characterized by a transient burst in proliferation to increase β-cell mass in response to the need for glucose homeostasis throughout life. In adulthood, the ability of β-cells to grow, proliferate, and expand their mass is also characteristic of pathological states of insulin resistance. Translationally controlled tumor-associated protein (TCTP), an evolutionarily highly conserved protein that is implicated in cell growth and proliferation, has been identified as a novel glucose-regulated survival-supporting protein in pancreatic β-cells. In this study, the enhanced β-cell proliferation detected both during the perinatal developmental period and in insulin-resistant states in high-fat diet-fed mice was found to parallel the expression of TCTP in pancreatic β-cells. Specific knockout of TCTP in β-cells led to increased expression of total and nuclear Forkhead box protein O1 and tumor suppressor protein 53, and decreased expression of p70S6 kinase phosphorylation and cyclin D2 and cyclin-dependent kinase 2. This resulted in decreased β-cell proliferation and growth, reduced β-cell mass, and insulin secretion. Together, these effects led to hyperglycemia. These observations suggest that TCTP is essential for β-cell mass expansion during development and β-cell adaptation in response to insulin resistance.

Funding information:
  • NIDDK NIH HHS - T32 DK007418(United States)
  • NINDS NIH HHS - R01 NS036715(United States)

Novel variant of neuronal intranuclear rodlet immunoreactive for 40 kDa huntingtin associated protein and ubiquitin in the mouse brain.

  • Milman P
  • J. Comp. Neurol.
  • 2013 Nov 30

Literature context:


Abstract:

Intranuclear rodlets (INRs), also known as rodlets of Roncoroni, are poorly understood intranuclear bodies originally identified within neuronal nuclei on the basis of their unique morphology. The mechanisms of their formation, their biochemical composition and their physiological significance remain unknown. Using double immunofluorescence staining of mouse brain sections, we identified a novel variant of INR that is immunoreactive for the 40 kDa huntingtin associated protein (Hap40) and ubiquitin, and provide evidence for the existence of additional INR subtypes sharing ubiquitin immunoreactivity as a common feature. We describe a selective association of these INRs with melanin concentrating hormone (MCH) and tyrosine hydroxylase immunoreactive neurons of the hypothalamus and the locus coeruleus, respectively. We also demonstrate for the first time that biochemically distinct INR subtypes can coexist within a single nucleus where they engage in nonrandom spatial interactions. Our findings highlight the biochemical diversity and cell type-specific expression of these enigmatic intranuclear structures.

Funding information:
  • NIA NIH HHS - P01AG009973-18(United States)
  • NIAID NIH HHS - 1R21AI085376(United States)

Constitutive somatostatin receptor subtype 2 activity attenuates GH synthesis.

  • Ben-Shlomo A
  • Endocrinology
  • 2013 Jul 24

Literature context:


Abstract:

Somatostatin signals predominantly through somatostatin receptor (SSTR) subtype 2 to attenuate GH release. However, the independent role of the receptor in regulating GH synthesis is unclear. Because we had previously demonstrated constitutive SSTR2 activity in mouse corticotrophs, we now analyzed GH regulation in rat pituitary somatotroph (GC) tumor cells, which express SSTR2 exclusively and are devoid of endogenous somatostatin ligand. We demonstrate that moderately stable SSTR2 overexpression (GpSSTR2(WT) cells) was associated with decreased GH promoter activity, GH mRNA, and hormone levels compared with those of control transfectants (GpCon cells). In contrast, levels of GH mRNA and peptide and GH promoter activity were unchanged in GpSSTR2(DRY) stable transfectants moderately expressing DRY motif mutated SSTR2 (R140A). GpSSTR(2DRY) did not exhibit an enhanced octreotide response as did GpSSTR2(WT) cells; however, both SSTR2(WT)-enhanced yellow fluorescent protein (eYFP) and SSTR2(DRY)-eYFP internalized on octreotide treatment. Suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor, increased GH synthesis in wild-type GC cells and primary pituitary cultures. GpSSTR2(WT) cells induced GH synthesis more strongly on SAHA treatment, evident by both higher GH peptide and mRNA levels compared with the moderate but similar GH increase observed in GpCon and GpSSTR2(DRY) cells. In vivo SAHA also increased GH release from GpSSTR2(WT) but not from control xenografts. Endogenous rat GH promoter chromatin immunoprecipitation showed decreased baseline acetylation of the GH promoter with exacerbated acetylation after SAHA treatment in GpSSTR2(WT) compared with that of either GpSSTR(2DRY) or control cells, the latter 2 transfectants exhibiting similar GH promoter acetylation levels. In conclusion, modestly increased SSTR2 expression constitutively decreases GH synthesis, an effect partially mediated by GH promoter histone deacetylation.

Funding information:
  • NICHD NIH HHS - R37 HD081168(United States)

Axon regeneration in the absence of growth cones: acceleration by cyclic AMP.

  • Jin LQ
  • J. Comp. Neurol.
  • 2009 Jul 20

Literature context:


Abstract:

Regenerative failure of spinal axons is commonly ascribed to signaling of F-actin depolymerization and growth cone collapse by molecules such as the myelin-associated growth inhibitors. cAMP is thought to promote regeneration at least in part by neutralizing this effect, either by direct action in the growth cone or indirectly by transcriptional mechanisms. In vivo evidence for this is based mainly on partial lesion studies in which it is sometimes difficult to distinguish regeneration of injured axons from collateral sprouting by uninjured axons. Moreover, previous observations on fixed lamprey central nervous system (CNS) suggested that regeneration may not involve growth cones. To distinguish actively growing axons from static or retracting ones, fluorescently labeled large reticulospinal axons were imaged in the living, transected lamprey cord with and without application of cAMP analogs and then studied by 2-photon microscopy. Axon tip movements over 2-48-hour intervals indicated: 1) regeneration was intermittent; 2) cAMP decreased initial axon retraction and increased subsequent regeneration up to 11-fold; 3) the increase in regeneration was due to an increase in velocity of axon growth, but not in the time spent in forward movement; 4) tips of actively regenerating axons were more sharply contoured than static tips but no filopodia or lamellipodia were observed, even in db-cAMP; and 5) during active growth, axon tips contained vesicle-like inclusions and were highly immunoreactive for neurofilaments. Staining for F-actin and microtubules was variable and F-actin was not concentrated at the leading edge. Thus, cAMP accelerates regeneration of lamprey spinal axons without inducing formation of growth cones.

Localization of the transcriptional coactivator PGC-1alpha to GABAergic neurons during maturation of the rat brain.

  • Cowell RM
  • J. Comp. Neurol.
  • 2007 May 1

Literature context:


Abstract:

The transcriptional coactivator peroxisome proliferator activated receptor gamma coactivator 1alpha (PGC-1alpha) can activate a number of transcription factors to regulate mitochondrial biogenesis and cell-specific responses to cold, fasting, and exercise. Recent studies indicate that PGC-1alpha knockout mice exhibit behavioral abnormalities and progressive vacuolization in various brain regions. To investigate the roles for PGC-1alpha in the nervous system, we evaluated the temporal and cell-specific expression of PGC-1alpha in the normal developing rat brain. Western blot of whole brain homogenates with a PGC-1alpha-specific antibody revealed that PGC-1alpha protein was most abundant in the embryonic and early postnatal forebrain and cerebellum. Using quantitative reverse-transcriptase polymerase chain reaction (RT-PCR), we determined that PGC-1alpha mRNA expression increased most markedly between postnatal days 3 (P3) and 14 in the cortex, striatum, and hippocampus. Immunohistochemical and immunofluorescence analyses of brain tissue indicated that while PGC-1alpha was found in most neuronal populations from embryonic day 15 to P3, it was specifically concentrated in GABAergic populations from P3 to adulthood. Interestingly, PGC-1alpha colocalized with the developmentally regulated chemoattractant reelin in the cortex and hippocampus, and the survival-promoting transcription factor myocyte enhancing factor 2 was highly concentrated in GABAergic populations in the striatum and cerebellum at times of PGC-1alpha expression. These results implicate PGC-1alpha as a regulator of metabolism and/or survival in GABAergic neurons during a phase of mitochondrial and synaptic changes in the developing brain and suggest that PGC-1alpha may be a good target for increasing metabolism in GABAergic populations in neurodevelopmental and neurodegenerative disorders.

Funding information:
  • NINDS NIH HHS - R15 NS087606(United States)