Effects of phosphotyrosine phosphatase inhibition on insulin secretion and intracellular signaling events in rat pancreatic islets.
Isolated rat pancreatic islets were incubated at 3.3 (low) and 16.7 (high) mM glucose with different concentrations of the phosphotyrosine phosphatase (PTP) inhibitor, peroxovanadate (pV). At low glucose, pV stimulated insulin secretion 2- to 4-fold, but it inhibited insulin secretion at 16.7 mM. The latter effect was not due to an inhibition of glucose metabolism, nor was it inhibited by pertussis toxin pretreatment. In addition, pV stimulated insulin secretion approximately 3-fold in depolarized cells at both low and high glucose. pV markedly increased the tyrosine phosphorylation of several proteins, including IRS-1 and -2, and also increased the phosphorylation of the downstream kinases PKB/Akt and MAPK. PKB/Akt, but not MAPK, was also phosphorylated in the absence of pV. Intracellular pV-stimulated tyrosine phosphorylation, including that of IRS-2, was generally increased by high glucose suggesting a further inhibition of PTP and/or enhanced tyrosine kinase activity. Thus, these data suggest that intracellular tyrosine and serine (PKB/Akt) phosphorylation are related to insulin secretion but they do not support a unique and direct link between IRS-2 tyrosine phosphorylation and glucose-stimulated insulin secretion.
Gogg
S
S
Lundberg Laboratory for Diabetes Research, Sahlgrenska University Hospital, Goteborg, Sweden.
Chen
J
J
Efendic
S
S
Smith
U
U
Ostenson
C
C
D000818:Animals; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D005947:Glucose / Q000494:pharmacology; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D015151:Immunoblotting; D007328:Insulin / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins; D000078790:Insulin Secretion; D047908:Intracellular Signaling Peptides and Proteins; D007515:Islets of Langerhans / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008297:Male; D037342:Pertussis Toxin; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011233:Precipitin Tests; D017346:Protein Serine-Threonine Kinases; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects*; D013997:Time Factors; D014443:Tyrosine / Q000378:metabolism; D014638:Vanadates / Q000494:pharmacology*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D007004:Hypoglycemic Agents; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; C526296:Irs1 protein, rat; C526299:Irs2 protein, rat; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D010566:Virulence Factors, Bordetella; C069276:peroxovanadate; D014638:Vanadates; D014443:Tyrosine; D037342:Pertussis Toxin; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D017027:Protein Tyrosine Phosphatases; D005947:Glucose