α-Synuclein Membrane Association Is Regulated by the Rab3a Recycling Machinery and Presynaptic Activity

• Published in: The Journal of biological chemistry 2013-03, Vol.288 (11), p.7438-7449
• Main Authors: Chen, Robert H.C., Wislet-Gendebien, Sabine, Samuel, Filsy, Visanji, Naomi P., Zhang, Gang, Marsilio, Diana, Langman, Tammy, Fraser, Paul E., Tandon, Anurag
• Format: Article
• Language: English
• Subjects: alpha-Synuclein - chemistry; alpha-Synuclein - metabolism; Animals; Brain - metabolism; Cell Line, Tumor; Cell Membrane - metabolism; Cytosol - metabolism; Epitopes - chemistry; Glycerol - chemistry; GTPase; Guanosine Triphosphate - metabolism; HSP90 Heat-Shock Proteins - metabolism; Humans; Membrane Proteins; Mice; Mice, Transgenic; Models, Biological; Molecular Bases of Disease; Neurodegeneration; Neurodegenerative Diseases - metabolism; Neurons - metabolism; Protein Complexes; Rab Proteins; rab3A GTP-Binding Protein - metabolism; Subcellular Fractionation; Subcellular Fractions - metabolism; Synapses - metabolism; Synaptosomes; Synaptosomes - metabolism; Synuclein
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M112.439497

α-Synuclein is an abundant presynaptic protein and a primary component of Lewy bodies in Parkinson disease. Although its pathogenic role remains unclear, in healthy nerve terminals α-synuclein undergoes a cycle of membrane binding and dissociation. An α-synuclein binding assay was used to screen for vesicle proteins involved in α-synuclein membrane interactions and showed that antibodies directed to the Ras-related GTPase Rab3a and its chaperone RabGDI abrogated α-synuclein membrane binding. Biochemical analyses, including density gradient sedimentation and co-immunoprecipitation, suggested that α-synuclein interacts with membrane-associated GTP-bound Rab3a but not to cytosolic GDP-Rab3a. Accumulation of membrane-bound α-synuclein was induced by the expression of a GTPase-deficient Rab3a mutant, by a dominant-negative GDP dissociation inhibitor mutant unable to recycle Rab3a off membranes, and by Hsp90 inhibitors, radicicol and geldanamycin, which are known to inhibit Rab3a dissociation from membranes. Thus, all treatments that inhibited Rab3a recycling also increased α-synuclein sequestration on intracellular membranes. Our results suggest that membrane-bound GTP-Rab3a stabilizes α-synuclein on synaptic vesicles and that the GDP dissociation inhibitor·Hsp90 complex that controls Rab3a membrane dissociation also regulates α-synuclein dissociation during synaptic activity. Background: α-Synuclein is known to undergo exchange between membrane and cytosolic compartments. Results: α-Synuclein interacts with GTP-bound Rab3a on synaptic vesicles, and its dissociation is mediated by GDI/Hsp90. Conclusion: α-Synuclein's membrane association and dissociation cycle is linked to synaptic activity by the Rab3a recycling machinery. Significance: Significance: Impairments to α-synuclein interactions with vesicles and with the Rab3a recycling machinery may affect neurodegeneration.