title: Involvement of Rab27b in the regulated secretion of pituitary hormones.
abstract: We recently identified a novel set of Rab and its effector, Rab27a/granuphilin, that possibly regulates the exocytosis of insulin-containing, dense core granules in pancreatic beta-cells. In the present study we characterized another isoform, Rab27b, to further investigate the function of the Rab27 subfamily. Among the tissues examined, Rab27b is most abundantly expressed in pituitary tissue, where Rab27a is preferentially expressed. It is also significantly expressed in brain and spleen, where Rab27a is minimally expressed. Rab27a and Rab27b are differentially expressed in pituitary cell types that secrete different peptide hormones. Rab27b associates with secretory granules and granuphilin in the pituitary endocrine cell line AtT20. Furthermore, overexpression of its inactive mutant, Rab27b N133I, significantly inhibits basal and forskolin-induced ACTH secretion in AtT20 cells. These findings indicate that Rab27b is involved in pituitary hormone secretion, which further supports the idea that members of the Rab27 subfamily regulate the exocytosis of dense core granules containing peptide hormones in endocrine cells.
authors.affiliation: Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi, Gunma 371-8512, Japan.
authors.forename: Shengli
authors.initials: S
authors.lastname: Zhao
authors.forename: Seiji
authors.initials: S
authors.lastname: Torii
authors.forename: Hiromi
authors.initials: H
authors.lastname: Yokota-Hashimoto
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Takeuchi
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Izumi
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000324:Adrenocorticotropic Hormone / Q000378:metabolism; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D003594:Cytoplasmic Granules / Q000378:metabolism; D004247:DNA / Q000235:genetics; D005089:Exocytosis / Q000235:genetics / Q000502:physiology; D005786:Gene Expression Regulation / Q000502:physiology; D005982:Glutathione Transferase / Q000096:biosynthesis / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D016297:Mutagenesis, Site-Directed; D010902:Pituitary Gland / Q000166:cytology / Q000378:metabolism; D010907:Pituitary Hormones / Q000378:metabolism*; D011233:Precipitin Tests; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000378:metabolism; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins / Q000502:physiology*; D000075745:rab27 GTP-Binding Proteins
chemical_list: D002352:Carrier Proteins; D010907:Pituitary Hormones; D011993:Recombinant Fusion Proteins; C512779:SYTL4 protein, human; C122015:Sytl4 protein, mouse; D033921:Vesicular Transport Proteins; D000075745:rab27 GTP-Binding Proteins; D000324:Adrenocorticotropic Hormone; D004247:DNA; D005982:Glutathione Transferase; C512958:Rab27b protein, mouse; C512962:Rab27a protein, mouse; D020691:rab GTP-Binding Proteins