A GDP/GTP exchange protein for the Rab3 small G protein family up-regulates a postdocking step of synaptic exocytosis in central synapses

摘要

The Rab3 GDP/GTP exchange protein (Rab3 GEP) activates the Rab3 small GTP-binding protein (G protein) family, including Rab3A that is an important member controlling synaptic vesicle trafficking. Here, we examined the role of Rab3 GEP in regulating neurotrans-mitter release in autapses of mouse hippocampal neurons in culture. The release probability was markedly reduced in Rab3 GEP-/- neurons, whereas the readily releasable pool size was not different between WT and Rab3 GEP-/- neurons, indicating that Rab3 GEP up-regulates a postdocking step of synaptic exocytosis. Because Rab3A reportedly down-regulates Ca~(2+)-triggered fusion of synaptic vesicles, these results provide evidence for a role of Rab3 GEP in the postdocking process distinct from Rab3A activation.