Rab3-interacting molecule γ isoforms lacking the rab3-binding domain induce long lasting currents but block neurotransmitter vesicle anchoring in voltage-dependent P/Q-type Ca2+ channels

Yoshitsugu Uriu, Shigeki Kiyonaka, Takafumi Miki, Masakuni Yagi, Satoshi Akiyama, Emiko Mori, Akito Nakao, Aaron M. Beedle, Kevin P. Campbell, Minoru Wakamori, Yasuo Mori

Research output: Contribution to journalArticle

37 Citations (Scopus)

Abstract

Assembly of voltage-dependent Ca2+ channels (VDCCs) with their associated proteins regulates the coupling of VDCCs with upstream and downstream cellular events. Among the four isoforms of the Rab3-interacting molecule (RIM1 to -4), we have previously reported that VDCC β-subunits physically interact with the long α isoform of the presynaptic active zone scaffolding protein RIM1 (RIM1α) via its C terminus containing the C 2B domain. This interaction cooperates with RIM1α-Rab3 interaction to support neurotransmitter exocytosis by anchoring vesicles in the vicinity of VDCCs and by maintaining depolarization-triggered Ca2+ influx as a result of marked inhibition of voltage-dependent inactivation of VDCCs. However, physiological functions have not yet been elucidated for RIM3 and RIM4, which exist only as short γ isoforms (γ-RIMs), carrying the C-terminal C2B domain common to RIMs but not the Rab3-binding region and other structural motifs present in the α-RIMs, including RIM1α. Here, we demonstrate that γ-RIMs also exert prominent suppression of VDCC inactivation via direct binding to β-subunits. In the pheochromocytoma PC12 cells, this common functional feature allows native RIMs to enhance acetylcholine secretion, whereas γ-RIMs are uniquely different from α-RIMs in blocking localization of neurotransmitter-containing vesicles near the plasma membrane. γ-RIMs as well as α-RIMs show wide distribution in central neurons, but knockdown of γ-RIMs attenuated glutamate release to a lesser extent than that of α-RIMs in cultured cerebellar neurons. The results suggest that sustained Ca2+ influx through suppression of VDCC inactivation by RIMs is a ubiquitous property of neurons, whereas the extent of vesicle anchoring to VDCCs at the plasma membrane may depend on the competition of α-RIMs with γ-RIMs for VDCC β-subunits.

Original languageEnglish
Pages (from-to)21750-21767
Number of pages18
JournalJournal of Biological Chemistry
Volume285
Issue number28
DOIs
Publication statusPublished - 09-07-2010

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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