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Title: Protein inhibitor of neuronal nitric oxide synthase (PIN) is a new regulator of glucose-induced insulin secretion. Author: Lajoix AD, Badiou S, Péraldi-Roux S, Chardès T, Dietz S, Aknin C, Tribillac F, Petit P, Gross R. Journal: Diabetes; 2006 Dec; 55(12):3279-88. PubMed ID: 17130471. Abstract: We previously showed that pancreatic beta-cells express neuronal nitric oxide synthase (nNOS) that controls insulin secretion through two catalytic activities: nitric oxide (NO) production and cytochrome c reductase activity. We now provide evidence that the endogenous protein inhibitor of nNOS (PIN) is expressed in rat pancreatic islets and INS-1 cells. Double-immunofluorescence studies showed a colocalization of PIN with both nNOS and myosin Va in insulin-secreting beta-cells. Electron microscopy studies confirmed that PIN is mainly associated with insulin secretory granules and colocated with nNOS in the latter. In addition, PIN overexpression in INS-1 cells enhanced glucose-induced insulin secretion, which is only partly reversed by addition of an NO donor, sodium nitroprusside (SNP), and unaffected by the inhibitor of cytochrome c reductase activity, miconazole. In contrast, the pharmacological inhibitor of nNOS, Nomega-nitro-l-arginine methyl ester, amplified glucose-induced insulin secretion, an effect insensitive to SNP but completely normalized by the addition of miconazole. Thus, PIN insulinotropic effect could be related to its colocalization with the actin-based molecular motor myosin Va and as such be implicated in the physiological regulation of glucose-induced insulin secretion at the level of the exocytotic machinery.[Abstract] [Full Text] [Related] [New Search]