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Foam cell formation by intimal smooth muscle cells (SMCs) inhibits the elaboration of extracellular matrix, which is detrimental to plaque stabilization. In the present study, we examined the lipoproteins and receptors involved in human SMC foam cell formation and investigated the ability of 24(S),25-epoxycholesterol [24(S),25-EC], an oxysterol agonist of the liver X receptor, to attenuate SMC foam cell formation.
Asthma is characterized by a chronic inflammatory process involving high numbers of inflammatory cells and mediators which have multiple inflammatory effects on the airway. Interferon (IFN)-alpha, which is used widely for treating chronic hepatitis C, is reported to have an effect on patients with Churg-Strauss syndrome. Therefore, it may also be suitable for patients with severe asthma.
The adoption of ACT as the first line treatment for uncomplicated malaria in Nigeria has concentrated attention on the role of testing in appropriate malaria treatment. There are calls at both national and global level for malaria treatment to be based on test result, but it is still unclear how testing can be incorporated into treatment-seeking and practices of health providers. This study explored community members and health providers' perceptions and experiences with malaria tests in south east Nigeria.
The PIM serine/threonine kinases and the mTOR/AKT pathway integrate growth factor signaling and promote cell proliferation and survival. They both share phosphorylation targets and have overlapping functions, which can partially substitute for each other. In cancer cells PIM kinases have been reported to produce resistance to mTOR inhibition by rapamycin. Tumor growth depends highly on blood vessel infiltration into the malignant tissue and therefore on endothelial cell proliferation. We therefore investigated how the PIM1 kinase modulates growth inhibitory effects of rapamycin in mouse aortic endothelial cells (MAEC). We found that proliferation of MAEC lacking Pim1 was significantly more sensitive to rapamycin inhibition, compared to wildtype cells. Inhibition of mTOR and AKT in normal MAEC resulted in significantly elevated PIM1 protein levels in the cytosol and in the nucleus. We observed that truncation of the C-terminal part of Pim1 beyond Ser 276 resulted in almost exclusive nuclear localization of the protein. Re-expression of this Pim1 deletion mutant significantly increased the proliferation of Pim1(-/-) cells when compared to expression of the wildtype Pim1 cDNA. Finally, overexpression of the nuclear localization mutant and the wildtype Pim1 resulted in complete resistance to growth inhibition by rapamycin. Thus, mTOR inhibition-induced nuclear accumulation of PIM1 or expression of a nuclear C-terminal PIM1 truncation mutant is sufficient to increase endothelial cell proliferation, suggesting that nuclear localization of PIM1 is important for resistance of MAEC to rapamycin-mediated inhibition of proliferation.
Central to NF-κB signaling pathways is IKKγ/NEMO, a regulatory subunit of the cytoplasmic IκB kinase (IKK) complex, which undergoes various posttranslational modifications, specifically phosphorylation, to regulate its function. Furthermore, Kaposi's sarcoma-associated herpesvirus (KSHV) FADD-like interleukin-1β (IL-1β) converting enzyme (FLICE) inhibitory protein (vFLIP) activates the NF-κB signaling pathway by directly interacting with IKKγ/NEMO. However, the exact functions of IKKγ/NEMO phosphorylation and its KvFLIP interaction in NF-κB activation remain elusive. Here, we report two novel phosphorylation sites of IKKγ/NEMO and their negative effect on the IKKγ/NEMO-mediated NF-κB signaling pathway. First, the Src family protein tyrosine kinases (SF-PTKs), including Src, Fyn, Lyn, and Fgr, interact with and phosphorylate tyrosine residue 374 (Y374) of IKKγ/NEMO. Mutation of the Y374 residue to phenylalanine (Y374F) specifically abolished SF-PTK-mediated tyrosine phosphorylation, leading to increased tumor necrosis factor alpha (TNF-α)-induced NF-κB activity. Moreover, our mass spectrometry analysis found that the serine 377 residue (S377) of IKKγ/NEMO underwent robust phosphorylation upon KvFLIP expression. Replacement of the IKKγ/NEMO S377 residue by alanine (S377A) or glutamic acid (S377E) resulted in a significant increase or decrease of NF-κB activity and TNF-α-mediated IL-6 cytokine production, respectively. Our study thus demonstrates that the Y374 or S377 residue located at the C-terminal proline-rich domain of human IKKγ/NEMO undergoes phosphorylation upon TNF-α treatment or KvFLIP expression, respectively, resulting in the suppression of IKKγ/NEMO activity to induce NF-κB activation. This study suggests the potential phosphorylation-mediated feedback negative regulation of IKKγ/NEMO activity in the NF-κB signaling pathway. IMPORTANCE Since unchecked regulation of NF-κB has been linked to uncontrolled proliferation and cell death, the downregulation of the NF-κB signaling pathway is as important as its activation. Specifically, the phosphorylation-mediated modification of IKKγ/NEMO is a critical regulatory mechanism of NF-κB activity. Here, we report two novel phosphorylations of IKKγ/NEMO and their negative effects on the NF-κB signaling pathway. First, the Src family protein tyrosine kinase interacts with and phosphorylates tyrosine residue 374 of IKKγ/NEMO, suppressing tumor necrosis factor alpha (TNF-α)-induced NF-κB activity. Additionally, Kaposi's sarcoma-associated herpesvirus (KSHV) FADD-like interleukin-1β (IL-1β) converting enzyme (FLICE) inhibitory protein (KvFLIP) expression induces a robust phosphorylation of the serine 377 residue of IKKγ/NEMO, resulting in a significant decrease of NF-κB activity. Our study thus demonstrates that the Y374 or S377 residue of IKKγ/NEMO undergoes phosphorylation upon TNF-α treatment or KvFLIP expression, respectively, resulting in the suppression of IKKγ/NEMO activity to induce NF-κB activation. This also suggests the potential phosphorylation-mediated feedback negative regulation of IKKγ/NEMO activity in the NF-κB signaling pathway.
The accumulation of mutations is a contributing factor in the initiation of premalignant mammary lesions and their progression to malignancy and metastasis. We have used a mouse model in which the carcinogen is the mouse mammary tumor virus (MMTV) which induces clonal premalignant mammary lesions and malignant mammary tumors by insertional mutagenesis. Identification of the genes and signaling pathways affected in MMTV-induced mouse mammary lesions provides a rationale for determining whether genetic alteration of the human orthologues of these genes/pathways may contribute to human breast carcinogenesis. A high-throughput platform for inverse PCR to identify MMTV-host junction fragments and their nucleotide sequences in a large panel of MMTV-induced lesions was developed. Validation of the genes affected by MMTV-insertion was carried out by microarray analysis. Common integration site (CIS) means that the gene was altered by an MMTV proviral insertion in at least two independent lesions arising in different hosts. Three of the new genes identified as CIS for MMTV were assayed for their capability to confer on HC11 mouse mammary epithelial cells the ability for invasion, anchorage independent growth and tumor development in nude mice. Analysis of MMTV induced mammary premalignant hyperplastic outgrowth (HOG) lines and mammary tumors led to the identification of CIS restricted to 35 loci. Within these loci members of the Wnt, Fgf and Rspo gene families plus two linked genes (Npm3 and Ddn) were frequently activated in tumors induced by MMTV. A second group of 15 CIS occur at a low frequency (2-5 observations) in mammary HOGs or tumors. In this latter group the expression of either Phf19 or Sdc2 was shown to increase HC11 cells invasion capability. Foxl1 expression conferred on HC11 cells the capability for anchorage-independent colony formation in soft agar and tumor development in nude mice. The published transcriptome and nucleotide sequence analysis of gene expression in primary human breast tumors was interrogated. Twenty of the human orthologues of MMTV CIS associated genes are deregulated and/or mutated in human breast tumors.
A series of twelve amides was synthesized via aminolysis of substituted pyrazinecarboxylic acid chlorides with substituted benzylamines. Compounds were characterized with analytical data and assayed in vitro for their antimycobacterial, antifungal, antibacterial and photosynthesis-inhibiting activity. 5-tert-Butyl-6-chloro-N-(4-methoxybenzyl)pyrazine-2-carboxamide (12) has shown the highest antimycobacterial activity against Mycobacterium tuberculosis (MIC = 6.25 µg/mL), as well as against other mycobacterial strains. The highest antifungal activity against Trichophyton mentagrophytes, the most susceptible fungal strain tested, was found for 5-chloro-N-(3-trifluoromethylbenzyl)-pyrazine-2-carboxamide (2, MIC = 15.62 µmol/L). None of the studied compounds exhibited any activity against the tested bacterial strains. Except for 5-tert-butyl-6-chloro-N-benzylpyrazine-2-carboxamide (9, IC(50) = 7.4 µmol/L) and 5-tert-butyl-6-chloro-N-(4-chlorobenzyl)pyrazine-2-carboxamide (11, IC(50) = 13.4 µmol/L), only moderate or weak photosynthesis-inhibiting activity in spinach chloroplasts (Spinacia oleracea L.) was detected.
Notch and Wnt are highly conserved signalling pathways that are used repeatedly throughout animal development to generate a diverse array of cell types. However, they often have opposing effects on cell-fate decisions with each pathway promoting an alternate outcome. Commonly, a cell receiving both signals exhibits only Wnt pathway activity. This suggests that Wnt inhibits Notch activity to promote a Wnt-ON/Notch-OFF output; but what might underpin this Notch regulation is not understood. Here, we show that Wnt acts via Dishevelled to inhibit Notch signalling, and that this crosstalk regulates cell-fate specification in vivo during Xenopus development. Mechanistically, Dishevelled binds and directly inhibits CSL transcription factors downstream of Notch receptors, reducing their activity. Furthermore, our data suggest that this crosstalk mechanism is conserved between vertebrate and invertebrate homologues. Thus, we identify a dual function for Dishevelled as an inhibitor of Notch signalling and an activator of the Wnt pathway that sharpens the distinction between opposing Wnt and Notch responses, allowing for robust cell-fate decisions.
A prominent feature of inflammatory diseases is endothelial dysfunction. Factors associated with endothelial dysfunction include proinflammatory cytokines, adhesion molecules, and matrix degrading enzymes. At the transcriptional level, they are regulated by the histone deacetylase sirtuin (SIRT) 1 via its actions on the proinflammatory transcription factor nuclear factor-κB (NF-κB). The role of SIRT6, also a histone deacetylase, in regulating inflammation in endothelial cells is not known. The aim of this study was to determine the effect of SIRT6 knockdown on inflammatory markers in human umbilical vein endothelial cells (HUVECs) in the presence of lipopolysaccharide (LPS). LPS decreased expression of SIRT6 in HUVECs. Knockdown of SIRT6 increased the expression of proinflammatory cytokines (IL-1β, IL-6, IL-8), COX-prostaglandin system, ECM remodelling enzymes (MMP-2, MMP-9 and PAI-1), the adhesion molecule ICAM-1, and proangiogenic growth factors VEGF and FGF-2; cell migration; cell adhesion to leukocytes. Loss of SIRT6 increased the expression of NF-κB, whereas overexpression of SIRT6 was associated with decreased NF-κB transcriptional activity. Taken together, these results demonstrate that the loss of SIRT6 in endothelial cells is associated with upregulation of genes involved in inflammation, vascular remodelling, and angiogenesis. SIRT6 may be a potential pharmacological target for inflammatory vascular diseases.
While the static magnitude of thermal pain perception has been shown to follow a power-law function of the temperature, its dynamical features have been largely overlooked. Due to the slow temporal experience of pain, multiple studies now show that the time evolution of its magnitude can be captured with continuous online ratings. Here we use such ratings to model quantitatively the temporal dynamics of thermal pain perception. We show that a differential equation captures the details of the temporal evolution in pain ratings in individual subjects for different stimulus pattern complexities, and also demonstrates strong predictive power to infer pain ratings, including readouts based only on brain functional images.
The acid-base behavior of amino acids is an important subject of study due to their prominent role in enzyme catalysis, substrate binding and protein structure. Due to interactions with the protein environment, their pK(a)s can be shifted from their solution values and, if a protein has two stable conformations, it is possible for a residue to have different "microscopic", conformation-dependent pK(a) values. In those cases, interpretation of experimental measurements of the pK(a) is complicated by the coupling between pH, protonation state and protein conformation. We explored these issues using Nitrophorin 4 (NP4), a protein that releases NO in a pH sensitive manner. At pH 5.5 NP4 is in a closed conformation where NO is tightly bound, while at pH 7.5 Asp30 becomes deprotonated, causing the conformation to change to an open state from which NO can easily escape. Using constant pH molecular dynamics we found two distinct microscopic Asp30 pK(a)s: 8.5 in the closed structure and 4.3 in the open structure. Using a four-state model, we then related the obtained microscopic values to the experimentally observed "apparent" pK(a), obtaining a value of 6.5, in excellent agreement with experimental data. This value must be interpreted as the pH at which the closed to open population transition takes place. More generally, our results show that it is possible to relate microscopic structure dependent pKa values to experimentally observed ensemble dependent apparent pK(a)s and that the insight gained in the relatively simple case of NP4 can be useful in several more complex cases involving a pH dependent transition, of great biochemical interest.
Alternaria brassicicola is a successful saprophyte and necrotrophic plant pathogen. Several A. brassicicola genes have been characterized as affecting pathogenesis of Brassica species. To study regulatory mechanisms of pathogenesis, we mined 421 genes in silico encoding putative transcription factors in a machine-annotated, draft genome sequence of A. brassicicola. In this study, targeted gene disruption mutants for 117 of the transcription factor genes were produced and screened. Three of these genes were associated with pathogenesis. Disruption mutants of one gene (AbPacC) were nonpathogenic and another gene (AbVf8) caused lesions less than half the diameter of wild-type lesions. Unexpectedly, mutants of the third gene, Amr1, caused lesions with a two-fold larger diameter than the wild type and complementation mutants. Amr1 is a homolog of Cmr1, a transcription factor that regulates melanin biosynthesis in several fungi. We created gene deletion mutants of Δamr1 and characterized their phenotypes. The Δamr1 mutants used pectin as a carbon source more efficiently than the wild type, were melanin-deficient, and more sensitive to UV light and glucanase digestion. The AMR1 protein was localized in the nuclei of hyphae and in highly melanized conidia during the late stage of plant pathogenesis. RNA-seq analysis revealed that three genes in the melanin biosynthesis pathway, along with the deleted Amr1 gene, were expressed at low levels in the mutants. In contrast, many hydrolytic enzyme-coding genes were expressed at higher levels in the mutants than in the wild type during pathogenesis. The results of this study suggested that a gene important for survival in nature negatively affected virulence, probably by a less efficient use of plant cell-wall materials. We speculate that the functions of the Amr1 gene are important to the success of A. brassicicola as a competitive saprophyte and plant parasite.
Herpes viruses persist in the infected host and are transmitted between hosts in the presence of a fully functional humoral immune response, suggesting that they can evade neutralization by antiviral antibodies. Human cytomegalovirus (HCMV) encodes a number of polymorphic highly glycosylated virion glycoproteins (g), including the essential envelope glycoprotein, gN. We have tested the hypothesis that glycosylation of gN contributes to resistance of the virus to neutralizing antibodies. Recombinant viruses carrying deletions in serine/threonine rich sequences within the glycosylated surface domain of gN were constructed in the genetic background of HCMV strain AD169. The deletions had no influence on the formation of the gM/gN complex and in vitro replication of the respective viruses compared to the parent virus. The gN-truncated viruses were significantly more susceptible to neutralization by a gN-specific monoclonal antibody and in addition by a number of gB- and gH-specific monoclonal antibodies. Sera from individuals previously infected with HCMV also more efficiently neutralized gN-truncated viruses. Immunization of mice with viruses that expressed the truncated forms of gN resulted in significantly higher serum neutralizing antibody titers against the homologous strain that was accompanied by increased antibody titers against known neutralizing epitopes on gB and gH. Importantly, neutralization activity of sera from animals immunized with gN-truncated virus did not exhibit enhanced neutralizing activity against the parental wild type virus carrying the fully glycosylated wild type gN. Our results indicate that the extensive glycosylation of gN could represent a potentially important mechanism by which HCMV neutralization by a number of different antibody reactivities can be inhibited.
Genomic DNA replication is a universal and essential process for all herpesvirus including human cytomegalovirus (HCMV). HCMV UL70 protein, which is believed to encode the primase activity of the viral DNA replication machinery and is highly conserved among herpesviruses, needs to be localized in the nucleus, the site of viral DNA synthesis. No host factors that facilitate the nuclear import of UL70 have been reported. In this study, we provided the first direct evidence that UL70 specifically interacts with a highly conserved and ubiquitously expressed member of the heat shock protein Hsp40/DNAJ family, DNAJB6, which is expressed as two isoforms, a and b, as a result of alternative splicing. The interaction of UL70 with a common region of DNAJB6a and b was identified by both a two hybrid screen in yeast and coimmunoprecipitation in human cells. In transfected cells, UL70 was primarily co-localized with DNAJB6a in the nuclei and with DNAJB6b in the cytoplasm, respectively. The nuclear import of UL70 was increased in cells in which DNAJB6a was up-regulated or DNAJB6b was down-regulated, and was reduced in cells in which DNAJB6a was down-regulated or DNAJB6b was up-regulated. Furthermore, the level of viral DNA synthesis and progeny production was increased in cells in which DNAJB6a was up-regulated or DNAJB6b was down-regulated, and was reduced in cells in which DNAJB6a was down-regulated or DNAJB6b was up-regulated. Thus, DNAJB6a and b appear to enhance the nuclear import and cytoplasmic accumulation of UL70, respectively. Our results also suggest that the relative expression levels of DNAJB6 isoforms may play a key role in regulating the cellular localization of UL70, leading to modulation of HCMV DNA synthesis and lytic infection.
Prions cause neurodegeneration in vivo, yet prion-infected cultured cells do not show cytotoxicity. This has hampered mechanistic studies of prion-induced neurodegeneration. Here we report that prion-infected cultured organotypic cerebellar slices (COCS) experienced progressive spongiform neurodegeneration closely reproducing prion disease, with three different prion strains giving rise to three distinct patterns of prion protein deposition. Neurodegeneration did not occur when PrP was genetically removed from neurons, and a comprehensive pharmacological screen indicated that neurodegeneration was abrogated by compounds known to antagonize prion replication. Prion infection of COCS and mice led to enhanced fodrin cleavage, suggesting the involvement of calpains or caspases in pathogenesis. Accordingly, neurotoxicity and fodrin cleavage were prevented by calpain inhibitors but not by caspase inhibitors, whereas prion replication proceeded unimpeded. Hence calpain inhibition can uncouple prion replication from its neurotoxic sequelae. These data validate COCS as a powerful model system that faithfully reproduces most morphological hallmarks of prion infections. The exquisite accessibility of COCS to pharmacological manipulations was instrumental in recognizing the role of calpains in neurotoxicity, and significantly extends the collection of tools necessary for rigorously dissecting prion pathogenesis.
Some monoaminergic neurons can release neurotransmitters by exocytosis from their cell bodies. The amount of monoamine released by somatic exocytosis can be comparable to that released by synaptic exocytosis, though neither the underlying mechanisms nor the functional significance of somatic exocytosis are well understood. A detailed examination of these characteristics may provide new routes for therapeutic intervention in mood disorders, substance addiction, and neurodegenerative diseases. The relatively large size of the cell body provides a unique opportunity to understand the mechanism of this mode of neuronal exocytosis in microscopic detail. Here we used three photon and total internal reflection fluorescence microscopy to focus on the dynamics of the pre-exocytotic events and explore the nature of somatic vesicle storage, transport, and docking at the membrane of serotonergic neurons from raphe nuclei of the rat brain. We find that the vesicles (or unresolved vesicular clusters) are quiescent (mean square displacement, MSD ∼0.04 μm(2)/s) before depolarization, and they move minimally (<1 μm) from their locations over a time-scale of minutes. However, within minutes of depolarization, the vesicles become more dynamic (MSD ∼0.3 μm(2)/s), and display larger range (several μm) motions, though without any clear directionality. Docking and subsequent exocytosis at the membrane happen at a timescale (∼25 ms) that is slower than most synaptic exocytosis processes, but faster than almost all somatic exocytosis processes observed in endocrine cells. We conclude that, (A) depolarization causes de-tethering of the neurotransmitter vesicles from their storage locations, and this constitutes a critical event in somatic exocytosis; (B) their subsequent transport kinetics can be described by a process of constrained diffusion, and (C) the pre-exocytosis kinetics at the membrane is faster than most other somatic exocytosis processes reported so far.
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