Role of Rab27 in synaptic transmission at the squid giant synapse

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 (...

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Published inProceedings of the National Academy of Sciences - PNAS Vol. 105; no. 41; pp. 16003 - 16008
Main Authors Yu, Eunah, Kanno, Eiko, Choi, Soonwook, Sugimori, Mutsuyuki, Moreira, Jorge E, Llinás, Rodolfo R, Fukuda, Mitsunori
Format Journal Article
LanguageEnglish
Published United States National Academy of Sciences 14.10.2008
National Acad Sciences
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Summary: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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Edited by Pasko Rakic, Yale University School of Medicine, New Haven, CT, and approved August 29, 2008
Author contributions: M.S., R.R.L., and M.F. designed research; E.Y., E.K., S.C., M.S., J.E.M., and R.R.L. performed research; E.K. and M.F. contributed new reagents/analytic tools; E.Y., S.C., M.S., J.E.M., R.R.L., and M.F. analyzed data; and M.S., J.E.M., R.R.L., and M.F. wrote the paper.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.0804825105