Early signaling events triggered by peroxovanadium [bpV(phen)] are insulin receptor kinase (IRK)-dependent: specificity of inhibition of IRK-associated protein tyrosine phosphatase(s) by bpV(phen).
Peroxovanadiums (pVs) are potent protein tyrosine phosphatase (PTP) inhibitors with insulin-mimetic properties in vivo and in vitro. We have established the existence of an insulin receptor kinase (IRK)-associated PTP whose inhibition by pVs correlates closely with IRK tyrosine phosphorylation, activation, and downstream signaling. pVs have also been shown to activate various tyrosine kinases (TKs) that could participate in activation of the insulin-signaling pathway. In the present study we have sought to determine whether pV-induced IRK tyrosine phosphorylation requires the intrinsic kinase activity of the IRK, and whether IRK activation is necessary to realize the early steps in the insulin-signaling cascade. To address this we evaluated the effect of a pure pV compound, bis peroxovanadium 1,10-phenanthroline [bpV(phen)], in HTC rat hepatoma cells overexpressing normal (HTC-IR) or kinase-deficient (HTC-M1030) mutant IRKs. We showed that at a dose of 0.1 mM, but not 1 mM, bpV(phen) induced IRK-dependent events. Thus, 0.1 mM bpV(phen) increased tyrosine phosphorylation and IRK activity in HTC-IR but not HTC-M1030 cells. Tyrosine phosphorylation of insulin signal-transducing molecules was promoted in HTC-IR but not HTC-M1030 cells by bpV(phen). The association of p185 and p60 with the src homology-2 (SH2) domains of Syp and the p85-regulatory subunit of phosphatidylinositol 3'-kinase was induced by bpV(phen) in HTC-IR, but not in HTC-M1030 cells, as was insulin receptor substrate-1-associated phosphatidylinositol 3'-kinase activity. Thus autophosphorylation and activation of the IRK by bpV(phen) is effected by the IRK itself, and the early events in the insulin- signaling cascade follow from this activation event. This establishes a critical role for PTP(s) in the regulation of IRK activity. bpV(phen) could be distinguished from insulin only in its ability to activate ERK1 in HTC-M1030 cells, thus indicating that this event is IRK independent, consistent with our previous hypothesis that bpV(phen) inhibits a PTP involved in the negative regulation of mitogen-activated protein kinases.
Band
C J
CJ
Department of Medicine, McGill University, Montreal, Quebec, Canada.
Posner
B I
BI
Dumas
V
V
Contreres
J O
JO
D000818:Animals; D006528:Carcinoma, Hepatocellular; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008113:Liver Neoplasms; D009942:Organometallic Compounds / Q000494:pharmacology*; D010618:Phenanthrolines / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000187:drug effects / Q000378:metabolism; D010750:Phosphoproteins / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011233:Precipitin Tests; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors* / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011972:Receptor, Insulin / Q000037:antagonists & inhibitors* / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D011993:Recombinant Fusion Proteins; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases; D015398:Signal Transduction / Q000187:drug effects*; D013379:Substrate Specificity / Q000187:drug effects; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000378:metabolism; D018909:src Homology Domains / Q000187:drug effects / Q000502:physiology
C526292:IRS1 protein, human; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; C526296:Irs1 protein, rat; D009942:Organometallic Compounds; D010618:Phenanthrolines; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; D014443:Tyrosine; C102120:bisperoxo(1,10-phenanthroline)oxovanadate(1-); D019869:Phosphatidylinositol 3-Kinases; D011972:Receptor, Insulin; C516724:PTPN11 protein, human; C509249:PTPN6 protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; C516727:Ptpn11 protein, rat; C509250:Ptpn6 protein, rat; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases