title: Interaction of ATP sensor, cAMP sensor, Ca2+ sensor, and voltage-dependent Ca2+ channel in insulin granule exocytosis.
abstract: ATP, cAMP, and Ca(2+) are the major signals in the regulation of insulin granule exocytosis in pancreatic beta cells. The sensors and regulators of these signals have been characterized individually. The ATP-sensitive K(+) channel, acting as the ATP sensor, couples cell metabolism to membrane potential. cAMP-GEFII, acting as a cAMP sensor, mediates cAMP-dependent, protein kinase A-independent exocytosis, which requires interaction with both Piccolo as a Ca(2+) sensor and Rim2 as a Rab3 effector. l-type voltage-dependent Ca(2+) channels (VDCCs) regulate Ca(2+) influx. In the present study, we demonstrate interactions of these molecules. Sulfonylurea receptor 1, a subunit of ATP-sensitive K(+) channels, interacts specifically with cAMP-GEFII through nucleotide-binding fold 1, and the interaction is decreased by a high concentration of cAMP. Localization of cAMP-GEFII overlaps with that of Rim2 in plasma membrane of insulin-secreting MIN6 cells. Localization of Rab3 co-incides with that of Rim2. Rim2 mutant lacking the Rab3 binding region, when overexpressed in MIN6 cells, is localized exclusively in cytoplasm, and impairs cAMP-dependent exocytosis in MIN6 cells. In addition, Rim2 and Piccolo bind directly to the alpha(1)1.2-subunit of VDCC. These results indicate that ATP sensor, cAMP sensor, Ca(2+) sensor, and VDCC interact with each other, which further suggests that ATP, cAMP, and Ca(2+) signals in insulin granule exocytosis are integrated in a specialized domain of pancreatic beta cells to facilitate stimulus-secretion coupling.
authors.affiliation: Division of Cellular and Molecular Medicine, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan.
authors.forename: Tadao
authors.initials: T
authors.lastname: Shibasaki
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Sunaga
authors.forename: Kei
authors.initials: K
authors.lastname: Fujimoto
authors.forename: Yasushige
authors.initials: Y
authors.lastname: Kashima
authors.forename: Susumu
authors.initials: S
authors.lastname: Seino
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry; D000242:Cyclic AMP / Q000378:metabolism* / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003594:Cytoplasmic Granules / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000502:physiology; D005089:Exocytosis / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005982:Glutathione Transferase / Q000235:genetics; D020662:Guanine Nucleotide Exchange Factors; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007340:Insulinoma; D058619:Maltose-Binding Proteins; D008564:Membrane Potentials; D051379:Mice; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009479:Neuropeptides / Q000235:genetics / Q000502:physiology; D010190:Pancreatic Neoplasms; D015221:Potassium Channels / Q000502:physiology; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011993:Recombinant Fusion Proteins; D015398:Signal Transduction; D014407:Tumor Cells, Cultured
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D015220:Calcium Channels; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D020662:Guanine Nucleotide Exchange Factors; D007328:Insulin; D058619:Maltose-Binding Proteins; D009419:Nerve Tissue Proteins; D009479:Neuropeptides; C498630:PCLO protein, human; C498631:Pclo protein, mouse; C405514:Pclo protein, rat; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; C491492:RIMS1 protein, human; D011993:Recombinant Fusion Proteins; C107293:Rim protein, mammalian; C491490:Rims1 protein, mouse; C491489:Rims1 protein, rat; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D005982:Glutathione Transferase; D017868:Cyclic AMP-Dependent Protein Kinases; D019204:GTP-Binding Proteins; D002118:Calcium