Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 38
Filter
1.
Proc Natl Acad Sci U S A ; 120(44): e2310174120, 2023 Oct 31.
Article in English | MEDLINE | ID: mdl-37883437

ABSTRACT

α-synuclein (α-Syn) is a presynaptic protein that is involved in Parkinson's and other neurodegenerative diseases and binds to negatively charged phospholipids. Previously, we reported that α-Syn clusters synthetic proteoliposomes that mimic synaptic vesicles. This vesicle-clustering activity depends on a specific interaction of α-Syn with anionic phospholipids. Here, we report that α-Syn surprisingly also interacts with the neutral phospholipid lysophosphatidylcholine (lysoPC). Even in the absence of anionic lipids, lysoPC facilitates α-Syn-induced vesicle clustering but has no effect on Ca2+-triggered fusion in a single vesicle-vesicle fusion assay. The A30P mutant of α-Syn that causes familial Parkinson disease has a reduced affinity to lysoPC and does not induce vesicle clustering. Taken together, the α-Syn-lysoPC interaction may play a role in α-Syn function.


Subject(s)
Parkinson Disease , alpha-Synuclein , Humans , alpha-Synuclein/genetics , alpha-Synuclein/metabolism , Synaptic Vesicles/metabolism , Lysophosphatidylcholines/metabolism , Parkinson Disease/genetics , Parkinson Disease/metabolism , Phospholipids/metabolism
2.
Brain ; 147(6): 2185-2202, 2024 Jun 03.
Article in English | MEDLINE | ID: mdl-38242640

ABSTRACT

Heterozygous de novo mutations in the neuronal protein Munc18-1/STXBP1 cause syndromic neurological symptoms, including severe epilepsy, intellectual disability, developmental delay, ataxia and tremor, summarized as STXBP1 encephalopathies. Although haploinsufficiency is the prevailing disease mechanism, it remains unclear how the reduction in Munc18-1 levels causes synaptic dysfunction in disease as well as how haploinsufficiency alone can account for the significant heterogeneity among patients in terms of the presence, onset and severity of different symptoms. Using biochemical and cell biological readouts on mouse brains, cultured mouse neurons and heterologous cells, we found that the synaptic Munc18-1 interactors Doc2A and Doc2B are unstable in the absence of Munc18-1 and aggregate in the presence of disease-causing Munc18-1 mutants. In haploinsufficiency-mimicking heterozygous knockout neurons, we found a reduction in Doc2A/B levels that is further aggravated by the presence of the disease-causing Munc18-1 mutation G544D as well as an impairment in Doc2A/B synaptic targeting in both genotypes. We also demonstrated that overexpression of Doc2A/B partially rescues synaptic dysfunction in heterozygous knockout neurons but not heterozygous knockout neurons expressing G544D Munc18-1. Our data demonstrate that STXBP1 encephalopathies are not only characterized by the dysfunction of Munc18-1 but also by the dysfunction of the Munc18-1 binding partners Doc2A and Doc2B, and that this dysfunction is exacerbated by the presence of a Munc18-1 missense mutant. These findings may offer a novel explanation for the significant heterogeneity in symptoms observed among STXBP1 encephalopathy patients.


Subject(s)
Calcium-Binding Proteins , Munc18 Proteins , Mutation , Nerve Tissue Proteins , Neurons , Synapses , Animals , Humans , Mice , Calcium-Binding Proteins/metabolism , Calcium-Binding Proteins/genetics , Cells, Cultured , Mice, Inbred C57BL , Mice, Knockout , Munc18 Proteins/genetics , Munc18 Proteins/metabolism , Mutation/genetics , Nerve Tissue Proteins/genetics , Nerve Tissue Proteins/metabolism , Neurons/metabolism , Synapses/metabolism , Synapses/genetics
3.
Mov Disord ; 2024 Jun 30.
Article in English | MEDLINE | ID: mdl-38946200

ABSTRACT

Various forms of Parkinson's disease, including its common sporadic form, are characterized by prominent α-synuclein (αSyn) aggregation in affected brain regions. However, the role of αSyn in the pathogenesis and evolution of the disease remains unclear, despite vast research efforts of more than a quarter century. A better understanding of the role of αSyn, either primary or secondary, is critical for developing disease-modifying therapies. Previous attempts to hone this research have been challenged by experimental limitations, but recent technological advances may facilitate progress. The Scientific Issues Committee of the International Parkinson and Movement Disorder Society (MDS) charged a panel of experts in the field to discuss current scientific priorities and identify research strategies with potential for a breakthrough. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

4.
J Neurochem ; 157(2): 165-178, 2021 04.
Article in English | MEDLINE | ID: mdl-32643187

ABSTRACT

Mutations in Munc18-1/STXBP1 (syntaxin-binding protein 1) are linked to various severe early epileptic encephalopathies and neurodevelopmental disorders. Heterozygous mutations in the STXBP1 gene include missense, nonsense, frameshift, and splice site mutations, as well as intragenic deletions and duplications and whole-gene deletions. No genotype-phenotype correlation has been identified so far, and patients are treated by anti-epileptic drugs because of the lack of a specific disease-modifying therapy. The molecular disease mechanisms underlying STXBP1-linked disorders are yet to be fully understood, but both haploinsufficiency and dominant-negative mechanisms have been proposed. This review focuses on the current understanding of the phenotypic spectrum of STXBP1-linked disorders, as well as discusses disease mechanisms in the context of the numerous pathways in which STXBP1 functions in the brain. We additionally evaluate the available animal models to study these disorders and highlight potential therapeutic approaches for treating these devastating diseases.


Subject(s)
Anticonvulsants/therapeutic use , Brain Diseases/metabolism , Munc18 Proteins/metabolism , Neurodevelopmental Disorders/drug therapy , Animals , Brain/metabolism , Brain Diseases/genetics , Humans , Munc18 Proteins/genetics , Mutation/genetics , Neurodevelopmental Disorders/genetics
5.
PLoS Biol ; 13(10): e1002267, 2015 Oct.
Article in English | MEDLINE | ID: mdl-26437117

ABSTRACT

In forebrain neurons, Ca(2+) triggers exocytosis of readily releasable vesicles by binding to synaptotagmin-1 and -7, thereby inducing fast and slow vesicle exocytosis, respectively. Loss-of-function of synaptotagmin-1 or -7 selectively impairs the fast and slow phase of release, respectively, but does not change the size of the readily-releasable pool (RRP) of vesicles as measured by stimulation of release with hypertonic sucrose, or alter the rate of vesicle priming into the RRP. Here we show, however, that simultaneous loss-of-function of both synaptotagmin-1 and -7 dramatically decreased the capacity of the RRP, again without altering the rate of vesicle priming into the RRP. Either synaptotagmin-1 or -7 was sufficient to rescue the RRP size in neurons lacking both synaptotagmin-1 and -7. Although maintenance of RRP size was Ca(2+)-independent, mutations in Ca(2+)-binding sequences of synaptotagmin-1 or synaptotagmin-7--which are contained in flexible top-loop sequences of their C2 domains--blocked the ability of these synaptotagmins to maintain the RRP size. Both synaptotagmins bound to SNARE complexes; SNARE complex binding was reduced by the top-loop mutations that impaired RRP maintenance. Thus, synaptotagmin-1 and -7 perform redundant functions in maintaining the capacity of the RRP in addition to nonredundant functions in the Ca(2+) triggering of different phases of release.


Subject(s)
Calcium Signaling , Hippocampus/metabolism , Nerve Tissue Proteins/metabolism , Neurons/metabolism , Synaptic Vesicles/metabolism , Synaptotagmin I/metabolism , Synaptotagmins/metabolism , Animals , Animals, Newborn , Binding Sites , Cells, Cultured , Excitatory Postsynaptic Potentials , HEK293 Cells , Hippocampus/cytology , Hippocampus/ultrastructure , Humans , Inhibitory Postsynaptic Potentials , Mice, Knockout , Mutation , Nerve Tissue Proteins/antagonists & inhibitors , Nerve Tissue Proteins/chemistry , Nerve Tissue Proteins/genetics , Neurons/cytology , Neurons/ultrastructure , RNA Interference , Recombinant Proteins/chemistry , Recombinant Proteins/metabolism , SNARE Proteins/metabolism , Synaptic Vesicles/ultrastructure , Synaptotagmin I/chemistry , Synaptotagmin I/genetics , Synaptotagmins/antagonists & inhibitors , Synaptotagmins/chemistry , Synaptotagmins/genetics
6.
Proc Natl Acad Sci U S A ; 111(40): E4274-83, 2014 Oct 07.
Article in English | MEDLINE | ID: mdl-25246573

ABSTRACT

Physiologically, α-synuclein chaperones soluble NSF attachment protein receptor (SNARE) complex assembly and may also perform other functions; pathologically, in contrast, α-synuclein misfolds into neurotoxic aggregates that mediate neurodegeneration and propagate between neurons. In neurons, α-synuclein exists in an equilibrium between cytosolic and membrane-bound states. Cytosolic α-synuclein appears to be natively unfolded, whereas membrane-bound α-synuclein adopts an α-helical conformation. Although the majority of studies showed that cytosolic α-synuclein is monomeric, it is unknown whether membrane-bound α-synuclein is also monomeric, and whether chaperoning of SNARE complex assembly by α-synuclein involves its cytosolic or membrane-bound state. Here, we show using chemical cross-linking and fluorescence resonance energy transfer (FRET) that α-synuclein multimerizes into large homomeric complexes upon membrane binding. The FRET experiments indicated that the multimers of membrane-bound α-synuclein exhibit defined intermolecular contacts, suggesting an ordered array. Moreover, we demonstrate that α-synuclein promotes SNARE complex assembly at the presynaptic plasma membrane in its multimeric membrane-bound state, but not in its monomeric cytosolic state. Our data delineate a folding pathway for α-synuclein that ranges from a monomeric, natively unfolded form in cytosol to a physiologically functional, multimeric form upon membrane binding, and show that only the latter but not the former acts as a SNARE complex chaperone at the presynaptic terminal, and may protect against neurodegeneration.


Subject(s)
Cell Membrane/metabolism , Protein Multimerization , SNARE Proteins/metabolism , alpha-Synuclein/chemistry , alpha-Synuclein/metabolism , Animals , Cell Membrane/chemistry , Fluorescence Resonance Energy Transfer , Humans , Immunoblotting , Liposomes/metabolism , Mice , Multiprotein Complexes/metabolism , Phospholipids/metabolism , Presynaptic Terminals/metabolism , Protein Binding , Synaptic Vesicles/metabolism , Vesicle-Associated Membrane Protein 2/metabolism
7.
J Neurosci ; 35(13): 5221-32, 2015 Apr 01.
Article in English | MEDLINE | ID: mdl-25834048

ABSTRACT

α-Synuclein physiologically chaperones SNARE-complex assembly at the synapse but pathologically misfolds into neurotoxic aggregates that are characteristic for neurodegenerative disorders, such as Parkinson's disease, and that may spread from one neuron to the next throughout the brain during Parkinson's disease pathogenesis. In normal nerve terminals, α-synuclein is present in an equilibrium between a cytosolic form that is natively unfolded and monomeric and a membrane-bound form that is composed of an α-helical multimeric species that chaperones SNARE-complex assembly. Although the neurotoxicity of α-synuclein is well established, the relationship between the native conformations of α-synuclein and its pathological aggregation remain incompletely understood; most importantly, it is unclear whether α-synuclein aggregation originates from its monomeric cytosolic or oligomeric membrane-bound form. Here, we address this question by introducing into α-synuclein point mutations that block membrane binding and by then assessing the effect of blocking membrane binding on α-synuclein aggregation and neurotoxicity. We show that membrane binding inhibits α-synuclein aggregation; conversely, blocking membrane binding enhances α-synuclein aggregation. Stereotactic viral expression of wild-type and mutant α-synuclein in the substantia nigra of mice demonstrated that blocking α-synuclein membrane binding significantly enhanced its neurotoxicity in vivo. Our data delineate a folding pathway for α-synuclein that ranges from a physiological multimeric, α-helical, and membrane-bound species that acts as a SNARE-complex chaperone over a monomeric, natively unfolded form to an amyloid-like aggregate that is neurotoxic in vivo.


Subject(s)
Neurotoxicity Syndromes/metabolism , Protein Aggregation, Pathological/metabolism , alpha-Synuclein/toxicity , Animals , HEK293 Cells , Humans , Liposomes/metabolism , Male , Mice , Neurons/drug effects , Neurons/metabolism , Neurotoxicity Syndromes/genetics , Point Mutation , Postural Balance/genetics , Protein Aggregation, Pathological/genetics , Protein Binding , Substantia Nigra/cytology , Substantia Nigra/metabolism , alpha-Synuclein/genetics
8.
EMBO J ; 31(4): 829-41, 2012 Feb 15.
Article in English | MEDLINE | ID: mdl-22187053

ABSTRACT

At a synapse, the synaptic vesicle protein cysteine-string protein-α (CSPα) functions as a co-chaperone for the SNARE protein SNAP-25. Knockout (KO) of CSPα causes fulminant neurodegeneration that is rescued by α-synuclein overexpression. The CSPα KO decreases SNAP-25 levels and impairs SNARE-complex assembly; only the latter but not the former is reversed by α-synuclein. Thus, the question arises whether the CSPα KO phenotype is due to decreased SNAP-25 function that then causes neurodegeneration, or due to the dysfunction of multiple as-yet uncharacterized CSPα targets. Here, we demonstrate that decreasing SNAP-25 levels in CSPα KO mice by either KO or knockdown of SNAP-25 aggravated their phenotype. Conversely, increasing SNAP-25 levels by overexpression rescued their phenotype. Inactive SNAP-25 mutants were unable to rescue, showing that the rescue was specific. Under all conditions, the neurodegenerative phenotype precisely correlated with SNARE-complex assembly, indicating that impaired SNARE-complex assembly due to decreased SNAP-25 levels is the ultimate correlate of neurodegeneration. Our findings suggest that the neurodegeneration in CSPα KO mice is primarily produced by defective SNAP-25 function, which causes neurodegeneration by impairing SNARE-complex assembly.


Subject(s)
HSP40 Heat-Shock Proteins/physiology , Membrane Proteins/physiology , Synaptosomal-Associated Protein 25/physiology , Animals , HSP40 Heat-Shock Proteins/genetics , Membrane Proteins/genetics , Mice , Mice, Knockout , Phenotype , Synaptic Transmission , Synaptosomal-Associated Protein 25/genetics
11.
Article in English | MEDLINE | ID: mdl-38772708

ABSTRACT

Parkinson's disease (PD) involves both the central nervous system (CNS) and enteric nervous system (ENS), and their interaction is important for understanding both the clinical manifestations of the disease and the underlying disease pathophysiology. Although the neuroanatomical distribution of pathology strongly suggests that the ENS is involved in disease pathophysiology, there are significant gaps in knowledge about the underlying mechanisms. In this article, we review the clinical presentation and management of gastrointestinal dysfunction in PD. In addition, we discuss the current understanding of disease pathophysiology in the gut, including controversies about early involvement of the gut in disease pathogenesis. We also review current knowledge about gut α-synuclein and the microbiome, discuss experimental models of PD-linked gastrointestinal pathophysiology, and highlight areas for further research. Finally, we discuss opportunities to use the gut-brain axis for the development of biomarkers and disease-modifying treatments.

12.
bioRxiv ; 2024 Mar 06.
Article in English | MEDLINE | ID: mdl-38496494

ABSTRACT

Post-translational modifications (PTMs) of α-synuclein (α-syn) such as acetylation and phosphorylation play important yet distinct roles in regulating α-syn conformation, membrane binding, and amyloid aggregation. However, how PTMs regulate α-syn function in presynaptic terminals remains unclear. Previously, we reported that α-syn clusters synaptic vesicles (SV) 1, and neutral phospholipid lysophosphatidylcholine (LPC) can mediate this clustering 2. Here, based on our previous findings, we further demonstrate that N-terminal acetylation, which occurs under physiological condition and is irreversible in mammalian cells, significantly enhances the functional activity of α-syn in clustering SVs. Mechanistic studies reveal that this enhancement is caused by the N-acetylation-promoted insertion of α-syn's N-terminus and increased intermolecular interactions on the LPC-containing membrane. Our work demonstrates that N-acetylation fine-tunes α-syn-LPC interaction for mediating α-syn's function in SV clustering.

13.
Nat Cell Biol ; 2024 Jul 01.
Article in English | MEDLINE | ID: mdl-38951706

ABSTRACT

α-Synuclein (α-Syn) aggregation is closely associated with Parkinson's disease neuropathology. Physiologically, α-Syn promotes synaptic vesicle (SV) clustering and soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex assembly. However, the underlying structural and molecular mechanisms are uncertain and it is not known whether this function affects the pathological aggregation of α-Syn. Here we show that the juxtamembrane region of vesicle-associated membrane protein 2 (VAMP2)-a component of the SNARE complex that resides on SVs-directly interacts with the carboxy-terminal region of α-Syn through charged residues to regulate α-Syn's function in clustering SVs and promoting SNARE complex assembly by inducing a multi-component condensed phase of SVs, α-Syn and other components. Moreover, VAMP2 binding protects α-Syn against forming aggregation-prone oligomers and fibrils in these condensates. Our results suggest a molecular mechanism that maintains α-Syn's function and prevents its pathological amyloid aggregation, the failure of which may lead to Parkinson's disease.

14.
Cell Rep ; 43(8): 114531, 2024 Jul 25.
Article in English | MEDLINE | ID: mdl-39058591

ABSTRACT

Spontaneous and sensory-evoked activity sculpts developing circuits. Yet, how these activity patterns intersect with cellular programs regulating the differentiation of neuronal subtypes is not well understood. Through electrophysiological and in vivo longitudinal analyses, we show that C-X-C motif chemokine ligand 14 (Cxcl14), a gene previously characterized for its association with tumor invasion, is expressed by single-bouquet cells (SBCs) in layer I (LI) of the somatosensory cortex during development. Sensory deprivation at neonatal stages markedly decreases Cxcl14 expression. Additionally, we report that loss of function of this gene leads to increased intrinsic excitability of SBCs-but not LI neurogliaform cells-and augments neuronal complexity. Furthermore, Cxcl14 loss impairs sensory map formation and compromises the in vivo recruitment of superficial interneurons by sensory inputs. These results indicate that Cxcl14 is required for LI differentiation and demonstrate the emergent role of chemokines as key players in cortical network development.

15.
J Neurosci ; 32(43): 15227-42, 2012 Oct 24.
Article in English | MEDLINE | ID: mdl-23100443

ABSTRACT

α-Synuclein is an abundant presynaptic protein that binds to phospholipids and synaptic vesicles. Physiologically, α-synuclein functions as a SNARE-protein chaperone that promotes SNARE-complex assembly for neurotransmitter release. Pathologically, α-synuclein mutations and α-synuclein overexpression cause Parkinson's disease, and aggregates of α-synuclein are found as Lewy bodies in multiple neurodegenerative disorders ("synucleinopathies"). The relation of the physiological functions to the pathological effects of α-synuclein remains unclear. As an initial avenue of addressing this question, we here systematically examined the effect of α-synuclein mutations on its physiological and pathological activities. We generated 26 α-synuclein mutants spanning the entire molecule, and analyzed them compared with wild-type α-synuclein in seven assays that range from biochemical studies with purified α-synuclein, to analyses of α-synuclein expression in cultured neurons, to examinations of the effects of virally expressed α-synuclein introduced into the mouse substantia nigra by stereotactic injections. We found that both the N-terminal and C-terminal sequences of α-synuclein were required for its physiological function as SNARE-complex chaperone, but that these sequences were not essential for its neuropathological effects. In contrast, point mutations in the central region of α-synuclein, referred to as nonamyloid ß component (residues 61-95), as well as point mutations linked to Parkinson's disease (A30P, E46K, and A53T) increased the neurotoxicity of α-synuclein but did not affect its physiological function in SNARE-complex assembly. Thus, our data show that the physiological function of α-synuclein, although protective of neurodegeneration in some contexts, is fundamentally distinct from its neuropathological effects, thereby dissociating the two activities of α-synuclein.


Subject(s)
Mutagenesis/genetics , Mutation/genetics , Parkinson Disease , Synucleins/genetics , Animals , Cells, Cultured , Disease Models, Animal , Gene Expression Regulation/genetics , Green Fluorescent Proteins/genetics , Hippocampus/cytology , Humans , Lipid Metabolism/genetics , Mice , Mice, Inbred C57BL , Mice, Knockout , Movement Disorders/genetics , Neurons , Parkinson Disease/genetics , Parkinson Disease/metabolism , Parkinson Disease/pathology , Phosphopyruvate Hydratase/metabolism , Psychomotor Performance/physiology , SNARE Proteins/metabolism , Substantia Nigra/metabolism , Substantia Nigra/pathology , Synaptosomal-Associated Protein 25/metabolism , Syntaxin 1/metabolism , Synucleins/chemistry , Synucleins/deficiency , Synucleins/metabolism , Transduction, Genetic , Transfection , Tyrosine 3-Monooxygenase/metabolism , Vesicle-Associated Membrane Protein 2/deficiency , Vesicle-Associated Membrane Protein 2/metabolism
16.
Trends Neurosci ; 46(2): 153-166, 2023 02.
Article in English | MEDLINE | ID: mdl-36567199

ABSTRACT

α-Synuclein is a neuronal protein that is enriched in presynaptic terminals. Under physiological conditions, it binds to synaptic vesicle membranes and functions in neurotransmitter release, although the molecular details remain unclear, and it is controversial whether α-synuclein inhibits or facilitates neurotransmitter release. Pathologically, in synucleinopathies including Parkinson's disease (PD), α-synuclein forms aggregates that recruit monomeric α-synuclein and spread throughout the brain, which triggers neuronal dysfunction at molecular, cellular, and organ levels. Here, we present an overview of the effects of α-synuclein on SNARE-complex assembly, neurotransmitter release, and synaptic vesicle pool homeostasis, and discuss how the observed divergent effects of α-synuclein on neurotransmitter release can be reconciled. We also discuss how gain-of-function versus loss-of-function of α-synuclein may contribute to pathogenesis in synucleinopathies.


Subject(s)
Parkinson Disease , Synucleinopathies , Humans , alpha-Synuclein/metabolism , Synucleinopathies/metabolism , Parkinson Disease/metabolism , Synaptic Vesicles/metabolism , Neurotransmitter Agents/metabolism
17.
J Mol Biol ; 435(1): 167714, 2023 01 15.
Article in English | MEDLINE | ID: mdl-35787839

ABSTRACT

α-Synuclein is an abundant protein at the neuronal synapse that has been implicated in Parkinson's disease for over 25 years and characterizes the hallmark pathology of a group of neurodegenerative diseases now known as the synucleinopathies. Physiologically, α-synuclein exists in an equilibrium between a synaptic vesicle membrane-bound α-helical multimer and a cytosolic largely unstructured monomer. Through its membrane-bound state, α-synuclein functions in neurotransmitter release by modulating several steps in the synaptic vesicle cycle, including synaptic vesicle clustering and docking, SNARE complex assembly, and homeostasis of synaptic vesicle pools. These functions have been ascribed to α-synuclein's interactions with the synaptic vesicle SNARE protein VAMP2/synaptobrevin-2, the synaptic vesicle-attached synapsins, and the synaptic vesicle membrane itself. How α-synuclein affects these processes, and whether disease is due to loss-of-function or gain-of-toxic-function of α-synuclein remains unclear. In this review, we provide an in-depth summary of the existing literature, discuss possible reasons for the discrepancies in the field, and propose a working model that reconciles the findings in the literature.


Subject(s)
Parkinson Disease , SNARE Proteins , Synapses , alpha-Synuclein , Humans , alpha-Synuclein/metabolism , Parkinson Disease/metabolism , SNARE Proteins/metabolism , Synapses/metabolism , Synaptic Vesicles/metabolism , Vesicle-Associated Membrane Protein 2/metabolism
18.
Nat Commun ; 13(1): 4918, 2022 08 22.
Article in English | MEDLINE | ID: mdl-35995799

ABSTRACT

Considerable evidence supports the release of pathogenic aggregates of the neuronal protein α-Synuclein (αSyn) into the extracellular space. While this release is proposed to instigate the neuron-to-neuron transmission and spread of αSyn pathology in synucleinopathies including Parkinson's disease, the molecular-cellular mechanism(s) remain unclear. To study this, we generated a new mouse model to specifically immunoisolate neuronal lysosomes, and established a long-term culture model where αSyn aggregates are produced within neurons without the addition of exogenous fibrils. We show that neuronally generated pathogenic species of αSyn accumulate within neuronal lysosomes in mouse brains and primary neurons. We then find that neurons release these pathogenic αSyn species via SNARE-dependent lysosomal exocytosis. The released aggregates are non-membrane enveloped and seeding-competent. Additionally, we find that this release is dependent on neuronal activity and cytosolic Ca2+. These results propose lysosomal exocytosis as a central mechanism for the release of aggregated and degradation-resistant proteins from neurons.


Subject(s)
Synucleinopathies , alpha-Synuclein , Animals , Exocytosis , Lysosomes/metabolism , Mice , Neurons/metabolism , alpha-Synuclein/metabolism
19.
Cell Rep ; 39(2): 110675, 2022 04 12.
Article in English | MEDLINE | ID: mdl-35417693

ABSTRACT

α-synuclein, ß-synuclein, and γ-synuclein are abundantly expressed proteins in the vertebrate nervous system. α-synuclein functions in neurotransmitter release by binding to and clustering synaptic vesicles and chaperoning SNARE-complex assembly. Pathologically, aggregates originating from soluble pools of α-synuclein are deposited into Lewy bodies in Parkinson's disease and related synucleinopathies. The functions of ß-synuclein and γ-synuclein in presynaptic terminals remain poorly studied. Using in vitro liposome binding studies, circular dichroism spectroscopy, immunoprecipitation, and fluorescence resonance energy transfer (FRET) experiments on isolated synaptic vesicles in combination with subcellular fractionation of brains from synuclein mouse models, we show that ß-synuclein and γ-synuclein have a reduced affinity toward synaptic vesicles compared with α-synuclein, and that heteromerization of ß-synuclein or γ-synuclein with α-synuclein results in reduced synaptic vesicle binding of α-synuclein in a concentration-dependent manner. Our data suggest that ß-synuclein and γ-synuclein are modulators of synaptic vesicle binding of α-synuclein and thereby reduce α-synuclein's physiological activity at the neuronal synapse.


Subject(s)
Synaptic Vesicles , alpha-Synuclein , Animals , Mice , Presynaptic Terminals/metabolism , Synaptic Vesicles/metabolism , alpha-Synuclein/metabolism , beta-Synuclein/metabolism , gamma-Synuclein/metabolism
20.
EMBO Mol Med ; 13(1): e12354, 2021 01 11.
Article in English | MEDLINE | ID: mdl-33332765

ABSTRACT

Heterozygous de novo mutations in the neuronal protein Munc18-1 cause syndromic neurological symptoms, including severe epilepsy, intellectual disability, developmental delay, ataxia, and tremor. No disease-modifying therapy exists to treat these disorders, and while chemical chaperones have been shown to alleviate neuronal dysfunction caused by missense mutations in Munc18-1, their required high concentrations and potential toxicity necessitate a Munc18-1-targeted therapy. Munc18-1 is essential for neurotransmitter release, and mutations in Munc18-1 have been shown to cause neuronal dysfunction via aggregation and co-aggregation of the wild-type protein, reducing functional Munc18-1 levels well below hemizygous levels. Here, we identify two pharmacological chaperones via structure-based drug design, that bind to wild-type and mutant Munc18-1, and revert Munc18-1 aggregation and neuronal dysfunction in vitro and in vivo, providing the first targeted treatment strategy for these severe pediatric encephalopathies.


Subject(s)
Brain Diseases , Epilepsy , Ataxia/drug therapy , Ataxia/genetics , Child , Heterozygote , Humans , Munc18 Proteins/genetics
SELECTION OF CITATIONS
SEARCH DETAIL