Glucose-induced translocation of protein kinase C in rat pancreatic islets.
The role of protein kinase C (PKC) as a mediator of glucose-induced insulin secretion has been a subject of controversy. Glucose-induced translocation of PKC has not been reported, and the relevant PKC isoenzymes in islets have not been identified. To address these issues, we developed specific antibodies to the alpha, beta, and gamma isoenzymes of PKC. Western blots of homogenates of freshly isolated rat islets probed with these antibodies revealed that the major isoenzyme present is alpha-PKC. Islets were perifused for 15 min with either 2.75 mM glucose, 20 mM glucose, 20 mM glucose plus 30 mM mannoheptulose, 15 mM alpha-ketoisocaproate, or alpha-ketoisocaproate plus mannoheptulose. Quantitative immunoblotting of membrane and cytosol fractions showed that alpha-PKC translocated from the cytosol to the membrane in freshly isolated rat islets stimulated with either 20 mM glucose or 15 mM alpha-ketoisocaproate. Both the secretory response and the translocation of alpha-PKC were blocked by the addition of mannoheptulose, an inhibitor of glucose metabolism, in islets stimulated with glucose but not in islets stimulated with alpha-ketoisocaproate. These results support a role for alpha-PKC in mediating glucose-induced insulin secretion in pancreatic islets.
Ganesan
S
S
Department of Cell Biology, Yale University School of Medicine, New Haven, CT.
Calle
R
R
Zawalich
K
K
Smallwood
J I
JI
Zawalich
W S
WS
Rasmussen
H
H
D000595:Amino Acid Sequence; D000818:Animals; D005947:Glucose / Q000494:pharmacology*; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D007527:Isoenzymes / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009842:Oligopeptides / Q000138:chemical synthesis; D011493:Protein Kinase C / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D007328:Insulin; D007527:Isoenzymes; D009842:Oligopeptides; D011493:Protein Kinase C; D005947:Glucose; D013755:Tetradecanoylphorbol Acetate