The prominent histopathological feature of the amyotrophic lateral sclerosis (ALS) is the presence of intracellular inclusions in degenerating neurons and their axons. The appearance and localization of these pathological structures depend on an aggregated protein that forms their scaffold. We investigated if γ-synuclein, an aggregation-prone protein highly expressed in healthy motor neurons, and predominantly localized in their axons and synaptic terminals is involved in ALS pathology.

alpha-Synuclein, a protein implicated in neurodegenerative diseases and of elusive physiological function owes its name to an observed presence in presynaptic and nuclear compartments. However, its nuclear localisation has remained controversial. We expressed synuclein-eGFP fusion proteins in organotypic rat hippocampal slice cultures and murine hippocampal primary neurons using a Sindbis virus expression system. Recombinant full-length alpha-synuclein accumulated in presynaptic locations, mimicking its native distribution. Expression of deletion mutant alpha-synuclein revealed that presynaptic targeting depended on the presence of its N-terminal and core region. This domain also causes nuclear exclusion of the alpha-synuclein fusion protein. In contrast, the C-terminal domain of alpha-synuclein directs fusion proteins into the nuclear compartment. The related protein gamma-synuclein contains a similar N-terminal and core domain as alpha-synuclein. However, gamma-synuclein lacks a C-terminal domain that causes nuclear localisation of the fusion protein, suggesting that the two synucleins might have different roles relating to the cell nucleus.

Previous studies have described gamma-synuclein as a protein highly expressed in retinal ganglion cells (RGCs), and a loss of RGCs correlates with a downregulation of gamma-synuclein gene expression in glaucoma. Here we asked whether gamma-synuclein expression in the retina can be considered a specific marker of RGCs.

Gamma synuclein (SNCG) is a neuronal protein that is also aberrantly overexpressed in various types of human cancer. SNCG overexpression promotes cancer invasion and metastasis. However, the mechanisms that drive cancer metastasis upon SNCG expression remain elusive. Elucidation of the mechanisms underlying the promotion of cancer metastasis by SNCG may help discover therapeutic avenues for SNCG-overexpressed cancer. Here, we show that SNCG promotes transforming growth factor-β (TGF-β)-induced p38 mitogen-activated protein kinase (MAPK) phosphorylation. Mechanistically, SNCG promotes p38MAPK phosphorylation by interacting with the MAPK kinase 3/6 (MKK3/6) and prevents their degradation. SNCG knockdown leads to a decrease in TGF-β-induced phosphorylation of MKK3/6; and abrogates the induction of matrix metalloproteinase (MMP)-9 expression by TGF-β and its target gene Twist1. Furthermore, p38MAPK inhibition abrogates the promotion of MMP-9 expression and cancer cell invasion by SNCG. Both p38MAPK and MMP inhibitors can suppress the promotion of cancer cell invasion by SNCG. Finally, overexpression of SNCG in liver cancer cells promotes lung metastasis, which can be suppressed by the p38MAPK inhibitor. Together, our data uncover a previously unknown role of SNCG in promoting TGF-β-MKK3/6-p38MAPK signaling. This study highlights the critical role of p38MAPK in the promotion of cancer metastasis by SNCG, and indicates that p38MAPK inhibitor may serve as a potential therapeutic for SNCG-overexpressed cancer.

BACKGROUND The role of gamma-synuclein (SNCG) has been widely examined in malignant conditions due to its possible role in disease progression, but very little information is available on its theoretical function on endometriosis formation. MATERIAL AND METHODS Between January 2016 and December 2016, we collected peritoneal fluid and plasma samples from 45 consecutive female patients, of which 15 were without endometriosis, 15 had minimal to mild endometriosis, and 15 had moderate to severe endometriosis. The statistical power was 0.98. We evaluated SNCG levels in the peritoneal fluid and plasma of patients diagnosed with endometriosis, and we compared them with the levels obtained from disease-free control subjects by using enzyme-linked immunosorbent assay. RESULTS SNCG levels were statistically significantly (1.2-fold) higher in the peritoneal fluid of patients with endometriosis compared to controls (p=0.04). We did not find a significant difference between SNCG levels in the plasma of our endometriosis patients and the control group (p=0.086). However, despite previous data showing very limited expression of SNCG in healthy tissues, we found SNCG in the peritoneal fluid of all of the patients in our healthy control group. CONCLUSIONS Levels of SNCG were statistically significantly higher in the peritoneal fluid of patients with endometriosis compared to disease-free controls, which may indicate its possible role the formation and progression of the disease. Moreover, its biological function should be further investigated due to the conflicting results concerning its expression in healthy tissues.

The mechanisms of neuronal protein γ-synuclein (SNCG) in the malignancy of oral squamous cell carcinoma (OSCC) are not clear. This study tested the hypothesis that SNCG is involved in nicotine-induced malignant behaviors of OSCC. The effect of nicotine on SNCG expression and epithelial-to-mesenchymal transition (EMT) markers were examined.

Gamma-synuclein (SNCG) has previously been demonstrated to be significantly correlated with metastatic malignancies; however, in-depth investigation of SNCG in prostate cancer is still lacking. In the present study, we evaluated the role of SNCG in prostate cancer progression and explored the underlying mechanisms.

Recently, we characterized tumor suppressor candidate 5 (Tusc5) as an adipocyte-neuron PPARgamma target gene. Our objective herein was to identify additional genes that display distinctly high expression in fat and neurons, because such a pattern could signal previously uncharacterized functional pathways shared in these disparate tissues. gamma-Synuclein, a marker of peripheral and select central nervous system neurons, was strongly expressed in white adipose tissue (WAT) and peripheral nervous system ganglia using bioinformatics and quantitative PCR approaches. Gamma-synuclein expression was determined during adipogenesis and in subcutaneous (SC) and visceral adipose tissue (VAT) from obese and nonobese humans. Gamma-synuclein mRNA increased from trace levels in preadipocytes to high levels in mature 3T3-L1 adipocytes and decreased approximately 50% following treatment with the PPARgamma agonist GW1929 (P < 0.01). Because gamma-synuclein limits growth arrest and is implicated in cancer progression in nonadipocytes, we suspected that expression would be increased in situations where WAT plasticity/adipocyte turnover are engaged. Consistent with this postulate, human WAT gamma-synuclein mRNA levels consistently increased in obesity and were higher in SC than in VAT; i.e. they increased approximately 1.7-fold in obese Pima Indian adipocytes (P = 0.003) and approximately 2-fold in SC and VAT of other obese cohorts relative to nonobese subjects. Expression correlated with leptin transcript levels in human SC and VAT (r = 0.887; P < 0.0001; n = 44). Gamma-synuclein protein was observed in rodent and human WAT but not in negative control liver. These results are consistent with the hypothesis that gamma-synuclein plays an important role in adipocyte physiology.

Dysregulation of intraocular pressure (IOP) is one of the main risk factors for glaucoma. γ-synuclein is a member of the synuclein family of widely expressed synaptic proteins within the central nervous system that are implicated in certain types of neurodegeneration. γ-synuclein expression and localization changes in the retina and optic nerve of patients with glaucoma. However, the mechanisms by which γ-synuclein could contribute to glaucoma are poorly understood. We assessed the presence of autoantibodies to γ-synuclein in the blood serum of patients with primary open-angle glaucoma (POAG) by immunoblotting. A positive reaction was detected for five out of 25 patients (20%) with POAG. Autoantibodies to γ-synuclein were not detected in a group of patients without glaucoma. We studied the dynamics of IOP in response to IOP regulators in knockout mice (γ-KO) to understand a possible link between γ-synuclein dysfunction and glaucoma-related pathophysiological changes. The most prominent decrease of IOP in γ-KO mice was observed after the instillation of 1% phenylephrine and 10% dopamine. The total protein concentration in tear fluid of γ-KO mice was approximately two times higher than that of wild-type mice, and the activity of neurodegeneration-linked protein α2-macroglobulin was reduced. Therefore, γ-synuclein dysfunction contributes to pathological processes in glaucoma, including dysregulation of IOP.

Gamma-synuclein (SNCG) promotes invasive behavior and is reportedly a prognostic factor in a range of cancers. However, its role in biliary tract carcinoma (BTC) remains unknown. Consequently, we investigated the clinicopathological significance and function of SNCG in BTC. Using resected BTC specimens from 147 patients with adenocarcinoma (extrahepatic cholangiocarcinoma [ECC, n = 96]; intrahepatic cholangiocarcinoma [ICC, n = 51]), we immunohistochemically evaluated SNCG expression and investigated its correlation with clinicopathological factors and outcomes. Furthermore, cell lines with high SNCG expression were selected from 16 BTC cell lines and these underwent cell proliferation and migration assays by siRNAs. In the results, SNCG expression was present in 22 of 96 (22.9%) ECC patients and in 10 of 51 (19.6%) ICC patients. SNCG expression was significantly correlated with poorly differentiated tumor in both ECC and ICC (p = 0.01 and 0.03, respectively) and with perineural invasion and lymph node metastases in ECC (p = 0.04 and 0.003, respectively). Multivariate analyses revealed that SNCG expression was an independent poor prognostic factor in both OS and RFS in both ECC and ICC. In vitro analyses showed high SNCG expression in three BTC cell lines (NCC-BD1, NCC-BD3, and NCC-CC6-1). Functional analysis revealed that SNCG silencing could suppress cell migration in NCC-BD1 and NCC-CC6-1 and downregulate cell proliferation in NCC-CC6-1 significantly. In conclusion, SNCG may promote tumor cell activity and is potentially a novel prognostic marker in BTC.

Transforming growth factor β (TGF-β) is critical for embryonic development, adult tissue homeostasis, and tumor progression. TGF-β suppresses tumors at early stage, but promotes metastasis at later stage through oncogenes such as Twist1. Gamma-synuclein (SNCG) is overexpressed in a variety of invasive and metastatic cancer. Here, we show that TGF-β induces SNCG expression by Smad-Twist1 axis, thus promoting TGF-β- and Twist1-induced cancer cell migration and invasion. We identify multiple Twist1-binding sites (E-boxes) in SNCG promoter. Chromatin immunoprecipitation and luciferase assays confirm the binding of Twist1 to the E-boxes of SNCG promoter sequence (-129/-1026 bp). Importantly, the Twist1-binding site close to the transcription initiation site is critical for the upregulation of SNCG expression by TGF-β and Twist1. Mutations of Twist1 motif on the SNCG promoter constructs markedly reduces the promoter activity. We further show that TGF-β induces Twist1 expression through Smad thereby enhancing the binding of Twist1 to SNCG promoter, upregulating SNCG promoter activity and increasing SNCG expression. SNCG knockdown abrogates TGF-β- or Twist1-induced cancer cell migration and invasion. Finally, SNCG knockdown inhibits the promotion of cancer metastasis by Twist1. Together, our data demonstrate that SNCG is a novel target of TGF-β-Smad-Twist1 axis and a mediator of Twist1-induced cancer metastasis.

α-Synuclein (αS) has been well-documented to play a role in human synucleinopathies such as Parkinson's disease (PD) and dementia with Lewy bodies (DLB). First, the lesions found in PD/DLB brains-Lewy bodies and Lewy neurites-are rich in aggregated αS. Second, genetic evidence links missense mutations and increased αS expression to familial forms of PD/DLB. Third, toxicity and cellular stress can be caused by αS under certain experimental conditions. In contrast, the homologs β-synuclein (βS) and γ-synuclein (γS) are not typically found in Lewy bodies/neurites, have not been clearly linked to brain diseases and have been largely non-toxic in experimental settings. In αS, the so-called non-amyloid-β component of plaques (NAC) domain, constituting amino acids 61-95, has been identified to be critical for aggregation in vitro. This domain is partially absent in βS and only incompletely conserved in γS, which could explain why both homologs do not cause disease. However, αS in vitro aggregation and cellular toxicity have not been firmly linked experimentally, and it has been proposed that excess αS membrane binding is sufficient to induce neurotoxicity. Indeed, recent characterizations of Lewy bodies have highlighted the accumulation of lipids and membranous organelles, raising the possibility that βS and γS could also become neurotoxic if they were more prone to membrane/lipid binding. Here, we increased βS and γS membrane affinity by strategic point mutations and demonstrate that these proteins behave like membrane-associated monomers, are cytotoxic and form round cytoplasmic inclusions that can be prevented by inhibiting stearoyl-CoA desaturase.

Amyotrophic lateral sclerosis (ALS) is characterised by substantial loss of both upper and lower motor neuron function, with sensory and cognitive systems less affected. Though heritable forms of the disease have been described, the vast majority of cases are sporadic with poorly defined underlying pathogenic mechanisms. Here we demonstrate that the neurological pathology induced in transgenic mice by overexpression of γ-synuclein, a protein not previously associated with ALS, recapitulates key features of the disease, namely selective damage and loss of discrete populations of upper and lower motor neurons and their axons, contrasted by limited effects upon the sensory system.

Increasing evidence reveals a significant correlation between gamma-synuclein (SNCG) level and tumor invasion and metastasis in various human cancers. Our previous investigation showed that SNCG could secrete into extracellular environment and promoted tumor cell motility, but the mechanism is unknown.

The presynaptic protein alpha-synuclein, associated with Parkinson's Disease (PD), plays a role in dopaminergic neurotransmission and is implicated in impulse control disorders (ICDs) such as drug addiction. In this study we investigated a potential causal relationship between alpha-synuclein and impulsivity, by evaluating differences in motor impulsivity in the 5-choice serial reaction time task (5-CSRTT) in strains of mice that differ in the expression of the alpha-synuclein gene. C57BL/6JOlaHsd mice differ from their C57BL/6J ancestors in possessing a chromosomal deletion resulting in the loss of two genes, snca, encoding alpha-synuclein, and mmrn1, encoding multimerin-1. C57BL/6J mice displayed higher impulsivity (more premature responding) than C57BL/6JOlaHsd mice when the pre-stimulus waiting interval was increased in the 5-CSRTT. In order to ensure that the reduced impulsivity was indeed related to snca, and not adjacent gene deletion, wild type (WT) and mice with targeted deletion of alpha-synuclein (KO) were tested in the 5-CSRTT. Similarly, WT mice were more impulsive than mice with targeted deletion of alpha-synuclein. Interrogation of our ongoing analysis of impulsivity in BXD recombinant inbred mouse lines revealed an association of impulsive responding with levels of alpha-synuclein expression in hippocampus. Expression of beta- and gamma-synuclein, members of the synuclein family that may substitute for alpha-synuclein following its deletion, revealed no differential compensations among the mouse strains. These findings suggest that alpha-synuclein may contribute to impulsivity and potentially, to ICDs which arise in some PD patients treated with dopaminergic medication.

The role of alpha-synuclein in pathogenesis of familial and idiopathic forms of Parkinson's disease, and other human disorders known as alpha-synucleinopathies, is well established. In contrast, the involvement of two other members of the synuclein family, beta-synuclein and gamma-synuclein, in the development and progression of neurodegeneration is poorly studied. However, there is a growing body of evidence that alpha-synuclein and beta-synuclein have opposite neuropathophysiological effects. Unlike alpha-synuclein, overexpressed beta-synuclein does not cause pathological changes in the nervous system of transgenic mice and even ameliorates the pathology caused by overexpressed alpha-synuclein. To assess the consequences of excess expression of the third family member, gamma-synuclein, on the nervous system we generated transgenic mice expressing high levels of mouse gamma-synuclein under control of Thy-1 promoter. These animals develop severe age- and transgene dose-dependent neuropathology, motor deficits and die prematurely. Histopathological changes include aggregation of gamma-synuclein, accumulation of various inclusions in neuronal cell bodies and processes, and astrogliosis. These changes are seen throughout the nervous system but are most prominent in the spinal cord where they lead to loss of spinal motor neurons. Our data suggest that down-regulation of small heat shock protein HSPB1 and disintegration of neurofilament network play a role in motor neurons dysfunction and death. These findings demonstrate that gamma-synuclein can be involved in neuropathophysiological changes and the death of susceptible neurons suggesting the necessity of further investigations of the potential role of this synuclein in disease.

The main objective of this study was to determine if levels of alpha-, beta- and/or gamma-synuclein mRNAs are differentially affected in brains of Lewy body disease (LBD) and Alzheimer's disease (AD) patients, compared to controls. In control cases, highest levels of expression were observed in the neocortex and the lowest in basal ganglia and substantia nigra. beta-Synuclein was the most abundant message (75-80%), followed by gamma-synuclein (10-15%) and alpha-synuclein (8-10%). Analysis of the superior temporal cortex, a region selectively affected in LBD and AD, showed that compared to controls, levels of alpha-synuclein were increased in cases of diffuse LBD (DLBD), levels of beta-synuclein were decreased in AD and DLBD, and levels of gamma-synuclein were increased in AD cases. This study suggests that a critical balance among products of the synuclein gene is important to maintain normal brain function and that alterations in this balance might be associated with neurodegenerative disorders.

Expression of A53T mutant human alpha-synuclein under the mouse prion promoter is among the most successful transgenic models of Parkinson's disease. Accumulation of A53T alpha-synuclein causes adult mice to develop severe motor impairment resulting in early death at 8-12 months of age. In younger, pre-symptomatic animals, altered motor activity and anxiety-like behaviors have also been reported. These behavioral changes, which precede severe neuropathology, may stem from non-pathological functions of alpha-synuclein, including modulation of monoamine neurotransmission. Our analysis over the adult life-span of motor activity, anxiety-like, and depressive-like behaviors identifies perturbations both before and after the onset of disease. Young A53T mice had increased distribution of the dopamine transporter (DAT) to the membrane that was associated with increased striatal re-uptake function. DAT function decreased with aging, and was associated with neurochemical alterations that included increased expression of beta-synuclein and gamma synuclein. Prior to normalization of dopamine uptake, transient activation of Tau kinases and hyperphosphorylation of Tau in the striatum were also observed. Aged A53T mice had reduced neuron counts in the substantia nigra pars compacta, yet striatal medium spiny neuron dendritic spine density was largely maintained. These findings highlight the involvement of the synuclein family of proteins and phosphorylation of Tau in the response to dopaminergic dysfunction of the nigrostriatal pathway.

Despite numerous evidences for neurotoxicity of overexpressed alpha-synuclein, a protective function was suggested for endogenous alpha-synuclein and other members of the synuclein family. This protective role is most important for and evident in presynaptic terminals, where synucleins are normally accumulated. However, mice lacking synucleins display no adverse phenotype. In particular, no significant changes in striatal dopamine metabolism and only subtle deficit of dopaminergic neurons in the substantia nigra were found in juvenile or adult mice. To assess whether aging and synuclein deficiency may have additive detrimental effect on the nigrostriatal system, we studied dopaminergic neurons of the substantia nigra and their striatal synapses in 24-26-month-old alpha-synuclein and gamma-synuclein null mutant mice. Significant approximately 36% reduction of the striatal dopamine was found in aging alpha-synuclein, but not gamma-synuclein null mutant mice when compared to age-matching wild type mice. This was accompanied by the reduction of TH-positive fibers in the striatum and decrease of striatal levels of TH and DAT. However, no progressive loss of TH-positive neurons was revealed in the substantia nigra of synuclein-deficient aging animals. Our results are consistent with a hypothesis that alpha-synuclein is important for normal function and integrity of synapses, and suggest that in the aging nervous system dysfunction of this protein could become a predisposition factor for the development of nigrostriatal pathology.

Aggregation of alpha-synuclein (α-syn) is considered to be the major pathological hallmark and driving force of Multiple System Atrophy (MSA) and Parkinson's disease (PD). Immune dysfunctions have been associated with both MSA and PD and recently we reported that the levels of natural occurring autoantibodies (NAbs) with high-affinity/avidity toward α-synuclein are reduced in MSA and PD patients. Here, we aimed to evaluate the plasma immunoglobulin (Ig) composition binding α-syn and other amyloidogenic neuropathological proteins, and to correlate them with disease severity and duration in MSA and PD patients. All participants were recruited from a single neurological unit and the plasma samples were stored for later research at the Bispebjerg Movement Disorder Biobank. All patients were diagnosed according to current consensus criteria. Using multiple variable linear regression analyses, we observed higher levels of anti-α-syn IgG1 and IgG3 NAbs in MSA vs. PD, higher levels of anti-α-syn IgG2 NAbs in PD compared to controls, whereas anti-α-syn IgG4 NAbs were reduced in PD compared to MSA and controls. Anti-α-syn IgM levels were decreased in both MSA and PD. Further our data supported that MSA patients' immune system was affected with reduced IgG1 and IgM global levels compared to PD and controls, with further reduced global IgG2 levels compared to PD. These results suggest distinct autoimmune patterns in MSA and PD. These findings suggest a specific autoimmune physiological mechanism involving responses toward α-syn, differing in neurodegenerative disease with overlapping α-syn pathology.