Protein inhibitor of neuronal nitric oxide synthase (PIN) is a new regulator of glucose-induced insulin secretion.
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.
Lajoix
Anne-Dominique
AD
CNRS UMR 5160, Faculté de Pharmacie, 15 Ave. Charles Flahault, BP 14491, 34093 Montpellier Cedex 5, France.
Badiou
Stéphanie
S
Péraldi-Roux
Sylvie
S
Chardès
Thierry
T
Dietz
Samuel
S
Aknin
Cindy
C
Tribillac
Florence
F
Petit
Pierre
P
Gross
René
R
D000818:Animals; D002460:Cell Line; D056445:Cytoplasmic Dyneins; D004398:Dyneins / Q000378:metabolism* / Q000502:physiology; D005947:Glucose / Q000494:pharmacology; D006706:Homeostasis; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000378:metabolism; D024701:Myosin Type V / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D007328:Insulin; C513081:Myo5a protein, rat; D052248:Nitric Oxide Synthase Type I; C486069:Dynll1 protein, rat; D024701:Myosin Type V; D018995:Myosin Heavy Chains; D056445:Cytoplasmic Dyneins; D004398:Dyneins; D005947:Glucose