title: Rab27a in pancreatic beta-cells, a busy protein in membrane trafficking.
abstract: The small GTPases have the 'active' GTP-bound and 'inactive' GDP-bound states, and thereby act as a molecular switch in cells. Rab27a is a member of this family and exists in T-lymphocytes, melanocytes and pancreatic beta-cells. Rab27a regulates secretion of cytolytic granules from cytotoxic T-lymphocytes and intracellular transport of melanosomes in melanocytes. In pancreatic beta-cells, Rab27a controls pre-exocytotic stages of insulin secretion. A few GTP-dependent Rab27a effectors are known to mediate these cellular functions. We recently found that Rab27a also possesses the GDP-dependent effector coronin 3. Coronin 3 regulates endocytosis in pancreatic beta-cells through its interaction with GDP-Rab27a. These results imply that GTP- and GDP-Rab27a actively regulate distinct stages in the insulin secretory pathway. In this review, we provide an overview of the roles of both GTP- and GDP-Rab27a in pancreatic beta-cells.
authors.affiliation: Department of Pharmacology, Oita University Faculty of Medicine, 1-1 Idaigaoka, Hasama, Yufu, Oita 8795593, Japan.
authors.forename: Toshihide
authors.initials: T
authors.lastname: Kimura
authors.forename: Ichiro
authors.initials: I
authors.lastname: Niki
mesh_terms: D000818:Animals; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000378:metabolism; D006801:Humans; D050417:Insulin-Secreting Cells / Q000166:cytology* / Q000378:metabolism; D008840:Microfilament Proteins / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D008840:Microfilament Proteins; D006153:Guanosine Diphosphate; D020691:rab GTP-Binding Proteins