2005 Fiscal Year Final Research Report Summary
Identification of the impaired sites of cAMP pathways in sulfonylurea receptor 1 knockout islets.
| Project/Area Number |
16590891
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Metabolomics
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| Research Institution | Kagoshima University |
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Principal Investigator |
NAKAZAKI Mitsuhiro Kagoshima University, University Hospital Faculty of Medicine and Dentistry, Research Associate, 医学部・歯学部附属病院, 助手 (40363626)
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| Co-Investigator(Kenkyū-buntansha) |
KORIYAMA Nobuyuki Kagoshima University, University Hospital Faculty of Medicine and Dentistry, Research Associate, 医学部・歯学部附属病院, 助手 (50363643)
YADA Toshihiko Jichi Medical University, School of Medicine, Professor, 医学部, 教授 (60166527)
KAKEI Masafumi Akita University, School of Medicine, Associate Professor, 医学部, 助教授 (90214270)
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| Project Period (FY) |
2004 – 2005
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| Keywords | Sulfonylurea receptor / Insulin secretion / Cyclic AMP |
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| Research Abstract |
The dynamic motion of single insulin secretory granules near the plasma membrane was examined in SUR1 knock-out (Sur1KO) β-cells by total internal reflection fluorescence microscopy. Sur1KO β-cells exhibited a marked reduction in the number of fusion events from previously docked granules. However, the number of docked granules declined during stimulation as a consequence of the release of docked granules into the cytoplasm vs. fusion with the plasma membrane. The similar result was observed by the stimulation of Sur1KO β-cells with high concentration of potassium ions. Thus, the impaired docking and fusion resulted in decreased insulin exocytosis from Sur1KO β-cells.
We next studied how cAMP amplified insulin exocytosis. Rat islets were permeabilized with α-toxin to measure insulin exocytosis in the fixed conditions of Ca^<2+> and ATP. The effects of several agents on insulin exocytosis were observed in perifusion experiments. Cyclic AMP enhanced the Ca^<2+>-induced insulin release by
… More
around 30%, independent of Ca^<2+> concentrations between 10 and 3000 nmol/L. A cAMP-GEF selective cAMP analogue, 8-(4-chloro-phenylthio)-2-Omethyladenosine- 3,5-cyclic monophosphate, also amplified insulin release. The effect disappeared in the absence of ATP. Conversely, cAMP-independent gradual increase in insulin release was observed with ATP. These results suggested that the site of action of cAMP-GEF existed proximal to that of ATP. An analogue selective to PKA, N6-Benzoyladenosine-3,5-cyclic monophosphate, had little effect. Also, a PKA-selective inhibitor, N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide, reduced insulin releases induced by 1000 nmol/L Ca^<2+>, but did not influence the relative increase produced by Ca^<2+> and cAMP. Cyclic AMP potentiated Ca^<2+> and ATP-induced exocytosis to a similar relative extent independent of Ca^<2+> concentrations. The process appeared to be mainly mediated by cAMP-GEF. In addition, the cAMP/cAMP-GEF pathway may enhance insulin release by replenishing the readily releasable pool. Less
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Research Products
(7 results)
