EPI64 protein functions as a physiological GTPase-activating protein for Rab27 protein and regulates amylase release in rat parotid acinar cells

Akane Imai, Sumio Yoshie, Koutaro Ishibashi, Maiko Haga-Tsujimura, Tomoko Nashida, Hiromi Shimomura, Mitsunori Fukuda

    Research output: Contribution to journalArticlepeer-review

    15 Citations (Scopus)

    Abstract

    Rab27, a small GTPase, is generally recognized as an important regulator of secretion that interacts with Rab27-specific effectors to regulate events in a wide variety of cells, including endocrine and exocrine cells. However, the mechanisms governing the spatio-temporal regulation of GTPase activity of Rab27 are not firmly established, and no GTPase-activating protein (GAP) specific for Rab27 has been identified in secretory cells. We previously showed that expression of EPI64, a Tre-2/Bub2/Cdc16 (TBC)-domain-containing protein, in melanocytes inactivates endogenous Rab27A on melanosomes (Itoh, T., and Fukuda, M. (2006) J. Biol. Chem. 281, 31823-31831), but the EPI64 role in secretory cells has never been investigated. In this study, we investigated the effect of EPI64 on Rab27 in isoproterenol (IPR)-stimulated amylase release from rat parotid acinar cells. Subcellular fractionation and immunohistochemical analyses indicated that EPI64 was enriched on the apical plasma membrane of parotid acinar cells. We found that an antibody against the TBC/Rab-GAP domain of EPI64 inhibited the reduction in levels of the endogenous GTP-Rab27 in streptolysin- O-permeabilized parotid acinar cells and suppressed amylase release in a dose-dependent manner.Wealso found that the levels of EPI64 mRNA and EPI64 protein increased after IPR stimulation, and that treatment with actinomycin D or antisense-EPI64 oligonucleotides suppressed the increase of EPI64 mRNA/EPI64 protein and the amount of amylase released. Our findings indicated that EPI64 acted as a physiological Rab27-GAP that enhanced GTPase activity of Rab27 in response to IPR stimulation, and that this activity is required for IPR-induced amylase release.

    Original languageEnglish
    Pages (from-to)33854-33862
    Number of pages9
    JournalJournal of Biological Chemistry
    Volume286
    Issue number39
    DOIs
    Publication statusPublished - 2011 Oct 30

    ASJC Scopus subject areas

    • Biochemistry
    • Molecular Biology
    • Cell Biology

    Fingerprint Dive into the research topics of 'EPI64 protein functions as a physiological GTPase-activating protein for Rab27 protein and regulates amylase release in rat parotid acinar cells'. Together they form a unique fingerprint.

    Cite this