Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 105, Issue 41, Pages 16003-16008Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0804825105
Keywords
Griscelli syndrome; rabphilin; small GTPase; total internal reflection fluorescence microscopy; vesicle exocytosis
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Funding
- Ministry of Education, Culture, Sports, and Technology of Japan [18207015, 19044003, 20022004, 20054001]
- Brain Science Foundation
- Naito Foundation
- Takeda Science Foundation
- Gushinkai Foundation
- Uehara Memorial Foundation
- Cooperacao Interinstitucional de Apoio a Pesquisa sobre o Cerebro Program FAPESP, Brasil [05-56447-7]
- National Institutes of Health [NS 13742-30]
- Grants-in-Aid for Scientific Research [19044003, 20022004, 20054001, 18207015, 20113006] Funding Source: KAKEN
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Small GTPase Rab is a member of a large family of Ras-related proteins, highly conserved in eukaryotic cells, and thought to regulate specific type(s) and/or specific step(s) in intracellular membrane trafficking. Given our interest in synaptic transmission, we addressed the possibility that Rab27 (a close isoform of Rab3) could be involved in cytosolic synaptic vesicle mobilization. Indeed, preterminal injection of a specific antibody against squid Rab27 (anti-sqRab27 antibody) combined with confocal microscopy demonstrated that Rab27 is present on squid synaptic vesicles. Electrophysiological study of injected synapses showed that the anti-sqRab27 antibody inhibited synaptic release in a stimulation-dependent manner without affecting presynaptic action potentials or inward Ca2+ current. This result was confirmed in in vitro synaptosomes by using total internal reflection fluorescence microscopy. Thus, synaptosomal Ca2+-stimulated release of FM1-43 dye was greatly impaired by intraterminal anti-sqRab27 antibody. Ultrastructural analysis of the injected giant preterminal further showed a reduced number of docked synaptic vesicles and an increase in nondocked vesicular profiles distant from the active zone. These results, taken together, indicate that Rab27 is primarily involved in the maturation of recycled vesicles and/or their transport to the presynaptic active zone in the squid giant synapse.
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