Sustained Exposure to High Glucose Concentrations Modifies Glucose Signaling and the Mechanics of Secretory Vesicle Fusion in Primary Rat Pancreatic β-Cells

  • Takashi Tsuboi
    From the Department of Biochemistry, Henry Wellcome Laboratories for Integrated Cell Signalling, School of Medical Sciences, University Walk, University of Bristol, Bristol, U.K
  • Magalie A. Ravier
    From the Department of Biochemistry, Henry Wellcome Laboratories for Integrated Cell Signalling, School of Medical Sciences, University Walk, University of Bristol, Bristol, U.K
  • Laura E. Parton
    From the Department of Biochemistry, Henry Wellcome Laboratories for Integrated Cell Signalling, School of Medical Sciences, University Walk, University of Bristol, Bristol, U.K
  • Guy A. Rutter
    From the Department of Biochemistry, Henry Wellcome Laboratories for Integrated Cell Signalling, School of Medical Sciences, University Walk, University of Bristol, Bristol, U.K

抄録

<jats:p>The mechanism(s) by which chronic hyperglycemia impairs glucose-stimulated insulin secretion is poorly defined. Here, we compare the “nanomechanics” of single exocytotic events in primary rat pancreatic β-cells cultured for 48 h at optimal (10 mmol/l) or elevated (30 mmol/l) glucose concentrations. Cargo release was imaged by total internal reflection fluorescence microscopy of lumen-targeted probes (neuropeptide Y [NPY]-pH–insensitive yellow fluorescent protein [NPY-Venus] or NPY–monomeric red fluorescent protein), while the fate of the vesicle membrane was reported simultaneously with phosphatase-on-the-granule-of-insulinoma–enhanced green fluorescent protein. Under all conditions studied, exocytosis proceeded via a “cavity recapture” mechanism in which the vesicle and plasma membranes fused transiently. While essentially complete release of NPY-Venus was observed in 24 ± 1% of glucose-stimulated exocytotic events in cells maintained at 10 mmol/l glucose, this value was reduced reversibly to 5 ± 2% of events by culture at 30 mmol/l glucose, in line with decreases in Glut2 and glucokinase gene expression, and attenuated glucose-stimulated increases in NADPH and intracellular [Ca2+]. Since vesicle release in response to cell depolarization with KCl was not affected by culture at 30 mmol/l glucose, we conclude that hyperglycemia causes the abnormal termination of individual insulin release events principally by inhibiting glucose signaling.</jats:p>

収録刊行物

  • Diabetes

    Diabetes 55 (4), 1057-1065, 2006-04-01

    American Diabetes Association

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