Histones facilitate α-synuclein aggregation during neuronal apoptosis

Parkinson's disease models and death signaling: what do we know until now?

Parkinson's disease (PD) is the second neurodegenerative disorder most prevalent in the world, characterized by the loss of dopaminergic neurons in the Substantia Nigra (SN). It is well known for its motor and non-motor symptoms including bradykinesia, resting tremor, psychiatric, cardiorespiratory, and other dysfunctions. Pathological apoptosis contributes to a wide variety of diseases including PD. Various insults and/or cellular phenotypes have been shown to trigger distinct signaling events leading to cell death in neurons affected by PD. The intrinsic or mitochondrial pathway, inflammatory or oxidative stress-induced extrinsic pathways are the main events associated with apoptosis in PD-related neuronal loss. Although SN is the main brain area studied so far, other brain nuclei are also affected by the disease leading to non-classical motor symptoms as well as non-motor symptoms. Among these, the respiratory symptoms are often overlooked, yet they can cause discomfort and may contribute to patients shortened lifespan after disease diagnosis. While animal and in vitro models are frequently used to investigate the mechanisms involved in the pathogenesis of PD in both the SN and other brain regions, these models provide only a limited understanding of the disease's actual progression. This review offers a comprehensive overview of some of the most studied forms of cell death, including recent research on potential treatment targets for these pathways. It highlights key findings and milestones in the field, shedding light on the potential role of understanding cell death in the prevention and treatment of the PD. Therefore, unraveling the connection between these pathways and the notable pathological mechanisms observed during PD progression could enhance our comprehension of the disease's origin and provide valuable insights into potential molecular targets for the developing therapeutic interventions.

Cerebral Microvascular Injury Induced by Lag3-Dependent α-Synuclein Fibril Endocytosis Exacerbates Cognitive Impairment in a Mouse Model of α-Synucleinopathies

The pathological accumulation of α-synuclein (α-Syn) and the transmission of misfolded α-Syn underlie α-synucleinopathies. Increased plasma α-Syn levels are associated with cognitive impairment in Parkinson's disease, multiple system atrophy, and dementia with Lewy bodies, but it is still unknown whether the cognitive deficits in α-synucleinopathies have a common vascular pathological origin. Here, it is reported that combined injection of α-Syn preformed fibrils (PFFs) in the unilateral substantia nigra pars compacta, hippocampus, and cerebral cortex results in impaired spatial learning and memory abilities at 6 months post-injection and that this cognitive decline is related to cerebral microvascular injury. Moreover, insoluble α-Syn inclusions are found to form in primary mouse brain microvascular endothelial cells (BMVECs) through lymphocyte-activation gene 3 (Lag3)-dependent α-Syn PFFs endocytosis, causing poly(ADP-ribose)-driven cell death and reducing the expression of tight junction proteins in BMVECs. Knockout of Lag3 in vitro prevents α-Syn PFFs from entering BMVECs, thereby reducing the abovementioned response induced by α-Syn PFFs. Deletion of endothelial cell-specific Lag3 in vivo reverses the negative effects of α-Syn PFFs on cerebral microvessels and cognitive function. In short, this study reveals the effectiveness of targeting Lag3 to block the spread of α-Syn fibrils to endothelial cells in order to improve cognition.

Unraveling the Complex Interplay between Alpha-Synuclein and Epigenetic Modification

Alpha-synuclein (αS) is a small, presynaptic neuronal protein encoded by the SNCA gene. Point mutations and gene multiplication of SNCA cause rare familial forms of Parkinson’s disease (PD). Misfolded αS is cytotoxic and is a component of Lewy bodies, which are a pathological hallmark of PD. Because SNCA multiplication is sufficient to cause full-blown PD, gene dosage likely has a strong impact on pathogenesis. In sporadic PD, increased SNCA expression resulting from a minor genetic background and various environmental factors may contribute to pathogenesis in a complementary manner. With respect to genetic background, several risk loci neighboring the SNCA gene have been identified, and epigenetic alterations, such as CpG methylation and regulatory histone marks, are considered important factors. These alterations synergistically upregulate αS expression and some post-translational modifications of αS facilitate its translocation to the nucleus. Nuclear αS interacts with DNA, histones, and their modifiers to alter epigenetic status; thereby, influencing the stability of neuronal function. Epigenetic changes do not affect the gene itself but can provide an appropriate transcriptional response for neuronal survival through DNA methylation or histone modifications. As a new approach, publicly available RNA sequencing datasets from human midbrain-like organoids may be used to compare transcriptional responses through epigenetic alterations. This informatic approach combined with the vast amount of transcriptomics data will lead to the discovery of novel pathways for the development of disease-modifying therapies for PD.

Novel insights into the role of circular RNAs in Parkinson disease: An emerging renaissance in the management of neurodegenerative diseases

Parkinson's disease (PD), as a debilitating neurodegenerative disease, particularly affects the elderly population, and is clinically identified by resting tremor, rigidity, and bradykinesia. Pathophysiologically, PD is characterized by an early loss of dopaminergic neurons in the Substantia nigra pars compacta, accompanied by the extensive aggregation of alpha-synuclein (α-Syn) in the form of Lewy bodies. The onset of PD has been reported to be influenced by multiple biological molecules. In this context, circular RNAs (circRNAs), as tissue-specific noncoding RNAs with closed structures, have been recently demonstrated to involve in a set of PD's pathogenic processes. These RNA molecules can either up- or downregulate the expression of α-Syn, as well as moderating its accumulation through different regulatory mechanisms, in which targeting microRNAs (miRNAs) is considered the most common pathway. Since circRNAs have prominent structural and biological characteristics, they could also be considered as promising candidates for PD diagnosis and treatment. Unfortunately, PD has become a global health concern, and a large number of its pathogenic processes are still unclear; thus, it is crucial to elucidate the ambiguous aspects of PD pathophysiology to improve the efficiency of diagnostic and therapeutic strategies. In line with this fact, the current review aims to highlight the interplay between circRNAs and PD pathogenesis, and then discusses the diagnostic and therapeutic potential of circRNAs in PD progression. This study will thus be the first of its kind reviewing the relationship between circRNAs and PD.

Constitutive nuclear accumulation of endogenous alpha-synuclein in mice causes motor impairment and cortical dysfunction, independent of protein aggregation

A growing body of evidence suggests that nuclear alpha-synuclein (αSyn) plays a role in the pathogenesis of Parkinson’s disease (PD). However, this question has been difficult to address as controlling the localization of αSyn in experimental systems often requires protein overexpression, which affects its aggregation propensity. To overcome this, we engineered Snca^NLS mice, which localize endogenous αSyn to the nucleus. We characterized these mice on a behavioral, histological and biochemical level to determine whether the increase of nuclear αSyn is sufficient to elicit PD-like phenotypes. Snca^NLS mice exhibit age-dependent motor deficits and altered gastrointestinal function. We found that these phenotypes were not linked to αSyn aggregation or phosphorylation. Through histological analyses, we observed motor cortex atrophy in the absence of midbrain dopaminergic neurodegeneration. We sampled cortical proteomes of Snca^NLS mice and controls to determine the molecular underpinnings of these pathologies. Interestingly, we found several dysregulated proteins involved in dopaminergic signaling, including Darpp32, Pde10a and Gng7, which we further confirmed was decreased in cortical samples of the Snca^NLS mice compared with controls. These results suggest that chronic endogenous nuclear αSyn can elicit toxic phenotypes in mice, independent of its aggregation. This model raises key questions related to the mechanism of αSyn toxicity in PD and provides a new model to study an underappreciated aspect of PD pathogenesis.

Neuropathology and molecular diagnosis of Synucleinopathies

Synucleinopathies are clinically and pathologically heterogeneous disorders characterized by pathologic aggregates of α-synuclein in neurons and glia, in the form of Lewy bodies, Lewy neurites, neuronal cytoplasmic inclusions, and glial cytoplasmic inclusions. Synucleinopathies can be divided into two major disease entities: Lewy body disease and multiple system atrophy (MSA). Common clinical presentations of Lewy body disease are Parkinson's disease (PD), PD with dementia, and dementia with Lewy bodies (DLB), while MSA has two major clinical subtypes, MSA with predominant cerebellar ataxia and MSA with predominant parkinsonism. There are currently no disease-modifying therapies for the synucleinopathies, but information obtained from molecular genetics and models that explore mechanisms of α-synuclein conversion to pathologic oligomers and insoluble fibrils offer hope for eventual therapies. It remains unclear how α-synuclein can be associated with distinct cellular pathologies (e.g., Lewy bodies and glial cytoplasmic inclusions) and what factors determine neuroanatomical and cell type vulnerability. Accumulating evidence from in vitro and in vivo experiments suggests that α-synuclein species derived from Lewy body disease and MSA are distinct "strains" having different seeding properties. Recent advancements in in vitro seeding assays, such as real-time quaking-induced conversion (RT-QuIC) and protein misfolding cyclic amplification (PMCA), not only demonstrate distinct seeding activity in the synucleinopathies, but also offer exciting opportunities for molecular diagnosis using readily accessible peripheral tissue samples. Cryogenic electron microscopy (cryo-EM) structural studies of α-synuclein derived from recombinant or brain-derived filaments provide new insight into mechanisms of seeding in synucleinopathies. In this review, we describe clinical, genetic and neuropathologic features of synucleinopathies, including a discussion of the evolution of classification and staging of Lewy body disease. We also provide a brief discussion on proposed mechanisms of Lewy body formation, as well as evidence supporting the existence of distinct α-synuclein strains in Lewy body disease and MSA.

Differences in Neuronal Numbers, Morphology, and Developmental Apoptosis in Mice Nigra Provide Experimental Evidence of Ontogenic Origin of Vulnerability to Parkinson's Disease

Parkinson disease (PD) prevalence varies by ethnicity. In an earlier study, we replicated the reduced vulnerability to PD in an admixed population, using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-susceptible C57BL/6 J, MPTP-resistant CD-1 and their F1 crossbreds. In the present study, we investigated if the differences have a developmental origin. Substantia nigra was evaluated at postnatal days 2 (P2), P6, P10, P14, P18, and P22. C57BL/6 J mice had smaller nigra and fewer dopaminergic neurons than the CD-1 and crossbreds at P2, which persisted through development. A significant increase in numbers and nigral volume was observed across strains until P14. A drastic decline thereafter was specific to C57BL/6 J. CD-1 and crossbreds retained their numbers from P14 to stabilize with supernumerary neurons at adulthood. The neuronal size increased gradually to attain adult morphology at P10 in the resistant strains, vis-à-vis at P22 in C57BL/6 J. Accordingly, in comparison to C57BL/6 J, the nigra of CD-1 and reciprocal crossbreds possessed cytomorphological features of resilience, since birth. The considerably lesser dopaminergic neuronal loss in the CD-1 and crossbreds was seen at P2 and P14 and thereafter was complemented by attenuated developmental cell death. The differences in programmed cell death were confirmed by reduced TUNEL labelling, AIF, and caspase-3 expression. GDNF expression aligned with the cell death pattern at P2 and P14 in both nigra and striatum. Earlier maturity of nigra and its neurons appears to be better features that reflect as MPTP resistance at adulthood. Thus, variable MPTP vulnerability in mice and also differential susceptibility to PD in humans may arise early during nigral development.

Roles for α-Synuclein in Gene Expression

α-Synuclein (α-Syn) is a small cytosolic protein associated with a range of cellular compartments, including synaptic vesicles, the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, and lysosomes. In addition to its physiological role in regulating presynaptic function, the protein plays a central role in both sporadic and familial Parkinson’s disease (PD) via a gain-of-function mechanism. Because of this, several recent strategies propose to decrease α-Syn levels in PD patients. While these therapies may offer breakthroughs in PD management, the normal functions of α-Syn and potential side effects of its depletion require careful evaluation. Here, we review recent evidence on physiological and pathological roles of α-Syn in regulating activity-dependent signal transduction and gene expression pathways that play fundamental role in synaptic plasticity.

Regulation of Mitochondrial Dynamics in Parkinson's Disease-Is 2-Methoxyestradiol a Missing Piece?

Mitochondria, as "power house of the cell", are crucial players in cell pathophysiology. Beyond adenosine triphosphate (ATP) production, they take part in a generation of reactive oxygen species (ROS), regulation of cell signaling and cell death. Dysregulation of mitochondrial dynamics may lead to cancers and neurodegeneration; however, the fusion/fission cycle allows mitochondria to adapt to metabolic needs of the cell. There are multiple data suggesting that disturbed mitochondrial homeostasis can lead to Parkinson's disease (PD) development. 2-methoxyestradiol (2-ME), metabolite of 17β-estradiol (E2) and potential anticancer agent, was demonstrated to inhibit cell growth of hippocampal HT22 cells by means of nitric oxide synthase (NOS) production and oxidative stress at both pharmacologically and also physiologically relevant concentrations. Moreover, 2-ME was suggested to inhibit mitochondrial biogenesis and to be a dynamic regulator. This review is a comprehensive discussion, from both scientific and clinical point of view, about the influence of 2-ME on mitochondria and its plausible role as a modulator of neuron survival.

Apoptotic Neuron-Derived Histone Amyloid Fibrils Induce α-Synuclein Aggregation

Cell-to-cell transfer of α-synuclein (αS) is increasingly thought to play an important role in propagation of αS pathology, but mechanisms responsible for formation of initial αS seeds and factors facilitating their propagation remain unclear. We previously demonstrated that αS aggregates are formed rapidly in apoptotic neurons and that interaction between cytoplasmic αS and proaggregant nuclear factors generates seed-competent αS. We also provided initial evidence that histones have proaggregant properties. Since histones are released from cells undergoing apoptosis or cell stress, we hypothesized that internalization of histones into αS expressing cells could lead to intracellular αS aggregation. Here using mCherry-tagged histone, we show that nuclear extracts from apoptotic cells can induce intracellular αS inclusions after uptake into susceptible cells, while extracts from non-apoptotic cells did not. We also demonstrate that nuclear extracts from apoptotic cells contained histone-immunoreactive amyloid fibrils. Moreover, recombinant histone-derived amyloid fibrils are able to induce αS aggregation in cellular and animal models. Induction of αS aggregation by histone amyloid fibrils is associated with endocytosis-mediated rupture of lysosomes, and this effect can be enhanced in cells with chemically induced lysosomal membrane defects. These studies provide initial descriptions of the contribution of histone amyloid fibrils to αS aggregation.

LRRK2 kinase inhibitors reduce alpha-synuclein in human neuronal cell lines with the G2019S mutation

Kinase activating missense mutations in leucine-rich repeat kinase 2 (LRRK2) predispose to Parkinson's disease. Consequently, there is much interest in delineating LRRK2 biology, both in terms of gaining further insight into disease causes, and also determining whether or not LRRK2 is a potential Parkinson's disease therapeutic target. Indeed, many potent and selective small molecule inhibitors of LRRK2 have been developed and are currently being used for pre-clinical testing in cell and animal models. In the current study, we have obtained fibroblasts from four subjects with the common LRRK2 mutation, G2019S. Fibroblasts were reprogrammed to induced pluripotent stem cells and then to neural stem cells and ultimately neurons. Two clones for each of the human neural cell lines were then chronically treated with and without either of two distinct inhibitors of LRRK2 and effects on toxicity and Parkinson's disease related phenotypes were assessed. Cells with the G2019S mutation had a propensity to accumulate the pathological Parkinson's disease protein α-synuclein. Moreover, α-synuclein accumulation in the G2019S cells was significantly reduced with both LRRK2 inhibitors in seven of the eight cell lines studied. LRRK2 inhibitors also improved the nuclear morphology of G2019S cells and impacted on measures of autophagy and endoplasmic reticulum stress. Lastly, we did not find evidence of inhibitor toxicity under the chronic treatment conditions. These results add to evidence that LRRK2 inhibitors may have utility in the treatment of Parkinson's disease via reducing α-synuclein.

SUMOylation in α-Synuclein Homeostasis and Pathology

The accumulation and aggregation of α-synuclein are central to Parkinson’s disease (PD), yet the molecular mechanisms responsible for these events are not fully understood. Post-translational modifications of α-synuclein regulate several of its properties, including degradation, interaction with proteins and membranes, aggregation and toxicity. SUMOylation is a post-translational modification involved in various nuclear and extranuclear processes, such as subcellular protein targeting, mitochondrial fission and synaptic plasticity. Protein SUMOylation increases in response to several stressful situations, from viral infections to trauma. In this framework, an increasing amount of evidence has implicated SUMOylation in several neurodegenerative diseases, including PD. This review will discuss recent findings in the role of SUMOylation as a regulator of α-synuclein accumulation, aggregation and toxicity, and its possible implication in neurodegeneration that underlies PD.

A robust strategy for proteomic identification of biomarkers of invasive phenotype complexed with extracellular heat shock proteins

As an extension of their orchestration of intracellular pathways, secretion of extracellular heat shock proteins (HSPs) is an emerging paradigm of homeostasis imperative to multicellular organization. Extracellular HSP is axiomatic to the survival of cells during tumorigenesis; proportional representation of specific HSP family members is indicative of invasive potential and prognosis. Further significance has been added by the knowledge that all cancer-derived exosomes have surface-exposed HSPs that reflect the membrane topology of cells that secrete them. Extracellular HSPs are also characteristic of chronic inflammation and sepsis. Accordingly, interrogation of extracellular HSPs secreted from cell culture models may represent a facile means of identifying translational biomarker signatures for targeting in situ. In the current study, we evaluated a simple peptide-based multivalent HSP affinity approach using the Vn96 peptide for low speed pelleting of HSP complexes from bioreactor cultures of cell lines with varying invasive phenotype in xenotransplant models: U87 (glioblastoma multiforme; invasive); HELA (choriocarcinoma; minimally invasive); HEK293T (virally transformed immortalized; embryonic). Proteomic profiling by bottom-up mass spectrometry revealed a comprehensive range of candidate biomarkers including primary HSP ligands. HSP complexes were associated with additional chaperones of prognostic significance such as protein disulfide isomerases, as well as pleiotropic metabolic enzymes, established as proportionally reflective of invasive phenotype. Biomarkers of inflammatory and mechanotransductive phenotype were restricted to the most invasive cell model U87, including chitinase CHI3L1, lamin C, amyloid derivatives, and histone isoforms.

CircSNCA downregulation by pramipexole treatment mediates cell apoptosis and autophagy in Parkinson's disease by targeting miR-7

We aimed to explore the mechanism of pramipexole (PPX) actions in the treatment of Parkinson’s disease (PD). Genes related to PD and PPX were screened through bioinformatics retrieval. The PD model was constructed by applying 1-methyl-4-phenylpyridinium (MMP+). The RNA expression levels of circSNCA, SNCA, apoptosis-related genes (BCL2, CASP3, BAX, PTEN and P53) and miR-7 were detected by qRT-PCR. Protein expression was determined by western blot. The interactions between circSNCA-miR-7-SNCA were verified by dual luciferase assay and immunofluorescence localization. Cell viability was determined by MTT assay. SNCA and circSNCA expression levels in PD were downregulated after PPX treatment, consistent with the levels of pro-apoptotic genes. CircSNCA increased SNCA expression by downregulating miR-7 in PD as a competitive endogenous RNA (ceRNA). Lower circSNCA expression was associated with the reduced expression of pro-apoptotic (CASP3, BAX, PTEN and P53) proteins. CircSNCA downregulation could decrease apoptosis and induce autophagy in PD. In conclusion, the downregulation of circSNCA by PPX treatment reduced cell apoptosis and promoted cell autophagy in PD via a mechanism that served as a miR-7 sponge to upregulate SNCA.

SNCA, a novel biomarker for Group 4 medulloblastomas, can inhibit tumor invasion and induce apoptosis

Medulloblastoma (MB) is the most common malignant brain tumor in childhood. It contains at least four distinct molecular subgroups. The aim of this study is to explore novel diagnostic and potential therapeutic markers within each subgroup of MB, in particular within Group 4, the largest subgroup, to facilitate diagnosis together with gene therapy. One hundred and six MB samples were examined. Tumor subtype was evaluated with the NanoString assay. Several novel tumor related genes were shown to have high subgroup sensitivity and specificity, including PDGFRA,FGFR1, and ALK in the WNT group, CCND1 in the SHH group, and α‐synuclein (SNCA) in Group 4. Knockdown and overexpression assays of SNCA revealed the ability of this gene to inhibit tumor invasion and induce apoptosis. Methylation‐specific PCR and pyrosequencing analysis showed that epigenetic mechanisms, rather than DNA hypermethylation, might play the key role in the regulation of SNCA expression in MB tumors. In conclusion, we identify SNCA as a novel diagnostic biomarker for Group 4 MB. Some other subgroup signature genes have also been found as candidate therapeutic targets for this tumor.

LncRNA SNHG1 promotes α-synuclein aggregation and toxicity by targeting miR-15b-5p to activate SIAH1 in human neuroblastoma SH-SY5Y cells

Numerous long non-coding RNAs (lncRNAs) have been identified as aberrantly expressed in Parkinson's disease (PD). However, limited knowledge is available concerning the roles of dysregulated lncRNAs and the underlying molecular regulatory mechanism in the pathological process of PD. In this study, we found that lncRNA small nucleolar RNA host gene 1 (SNHG1) and seven in absentia homolog 1 (SIAH1) were upregulated, but microRNA-15b-5p (miR-15b-5p) was downregulated in SH-SY5Y cells pretreated with MPP+, as well as in MPTP-induced mouse model of PD. Overexpression of SIAH1 enhanced cellular toxicity of α-synuclein in SH-SY5Y cells, as indicated by the reduction of cell viability and elevation of LDH release. The percentage of α-synuclein aggregate-positive cells and the number of α-synuclein aggregates per cell were increased in SH-SY5Y cells transfected with pcDNA-SIAH1, while decreased after transfection with short interfering RNA specific for SIAH1 (si-SIAH1). Bioinformatics and luciferase reporter assay revealed that SIAH1 was a direct target of miR-15b-5p. We also found that SNHG1 could directly bind to miR-15-5p and repress miR-15-5p expression. Upregulation of miR-15b-5p alleviated α-synuclein aggregation and apoptosis by targeting SIAH1 in SH-SY5Y cells overexpressing α-synuclein. Overexpression of SNHG1 enhanced, whereas SNHG1 knockdown inhibited α-synuclein aggregation and α-synuclein-induced apoptosis. Moreover, the neuroprotective effect of si-SNHG1 was abrogated by downregulation of miR-15b-5p. In summary, our data suggest that SNHG1, as a pathogenic factor, promotes α-synuclein aggregation and toxicity by targeting the miR-15b-5p/SIAH1 axis, contributing to a better understanding of the mechanisms of Lewy body formation and loss of dopaminergic neurons in PD.

Neuropathology of Parkinson disease

INTRODUCTION

Parkinson's disease (PD) is characterized by bradykinesia, rigidity, postural instability and tremor. Several pathologic processes can produce this syndrome, but neurodegeneration accompanied by neuronal inclusions composed of α-synuclein (Lewy bodies) is considered the typical pathologic correlate of PD.

METHODS

The neuropathologic features of PD are reviewed based upon personal experience and review of the literature. Molecular pathology of PD is summarized from cell biological and animal studies.

RESULTS

The pathologic feature that correlates with signs and symptoms of PD is neuronal loss in the substantia nigra with dopaminergic denervation of the striatum. Neuronal degeneration in the substantia nigra preferentially affects the ventrolateral cell group that projects to posterolateral putamen and is accompanied by formation of Lewy bodies composed of aggregated α-synuclein. Some patients with PD are found at autopsy to have other pathologic processes, such as multiple system atrophy, progressive supranuclear palsy and cerebrovascular disease (vascular Parkinsonism). The peripheral autonomic nervous system is also affected. The triggering event in PD is unknown, but recent studies suggest a role for loss of nuclear membrane integrity. Once α-synuclein aggregates forms, evidence supports cell-to-cell propagation.

CONCLUSION

PD is a multisystem synucleinopathy caused by poorly characterized genetic and environmental factors that produces degeneration in selectively vulnerable neuronal populations.

Synucleins and Gene Expression: Ramblers in a Crowd or Cops Regulating Traffic?

Synuclein family consists of three members, α, β, and γ-synuclein. Due to their involvement in human diseases, they have been thoroughly investigated for the last 30 years. Since the first synuclein identification and description, members of this family are found in all vertebrates. Sequencing of their genes indicates high evolutionary conservation suggesting important function(s) of these proteins. They are small naturally unfolded proteins prone to aggregate, easily change their conformation, and bind to the membranes. The genes for α, β, and γ-synuclein have different chromosomal localization and a well preserved general organization composed of five coding exons of similar size. Three genes encoding synucleins are present in the majority of vertebrates, however, a variable number of synuclein genes are described in fishes of different species. An important question concerns their normal function in cells and tissues. α-Synuclein is implicated in the regulation of synaptic activity through regulation of synaptic vesicle release, while the physiological functions of two other members of the family is understood less clearly. Here we discuss recent results describing their role in the regulation of gene expression.