Rab3A GTPase-activating protein-inhibiting activity of rabphilin-3A, a putative Rab3A target protein

Shosei Kishida, Hiromichi Shirataki, Takuya Sasaki, Masaki Kato, Kozo Kaibuchi, Yoshimi Takai

Research output: Contribution to journalArticlepeer-review

62 Citations (Scopus)

Abstract

Rabphilin-3A is a putative target protein for Rab3A, a member of the small G protein superfamily that is implicated in regulated secretion, particularly in neuro-transmitter release. Rabphilin-3A contains at least two functionally different domains: the N-terminal Rab3A-binding domain and the C-terminal C2 domain, which interacts with both Ca2+ and phospholipid. Because Rabphilin-3A interacts preferentially with GTP-Rab3A rather than with GDP-Rab3A, we have examined here whether Rabphilin-3A affects the GTPase activity of Rab3A. Rabphilin-3A and its N-terminal fragment, but not its C-terminal fragment, very weakly stimulated the basal GTPase activity of Rab3A. However, Rabphilin-3A and its N-terminal fragment strongly inhibited the Rab3A GAP-stimulated GTPase activity of Rab3A. Ca2+ and phospholipid showed no effect on these activities of Rabphilin-3A. The physiological significance of the GAP activity of Rabphilin-3A is obscure, but it is likely that Rabphilin-3A inhibits Rab3A GAP activity and keeps Rab3A in the GTP-bound active form during its action as a target molecule for Rab3A.

Original languageEnglish
Pages (from-to)22259-22261
Number of pages3
JournalJournal of Biological Chemistry
Volume268
Issue number30
Publication statusPublished - Oct 25 1993
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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