Roles of Rab27a and granuphilin in the docking of insulin granules onto the plasma membrane

Abstract

Monomeric small GTPase Rab27a and its effector granuphilin are specifically localized on insulin granules in pancreatic beta cells. Granuphilin is involved in the exocytosis of insulin granules through a direct binding to the plasma membrane-anchored SNARE, syntaxin 1a, and active Rab27a enhances the complex formation. We propose that this interaction, at least in part, mediates the docking of insulin granules to the plasma membrane. Biochemical, physiological, and genetic evidence to support this notion will be presented. [Jpn J Physiol 55 Suppl:S34 (2005)]