Expression of dominant negative mutant SHPTP2 attenuates phosphatidylinositol 3'-kinase activity via modulation of phosphorylation of insulin receptor substrate-1.
To clarify the role of protein-tyrosine phosphatase (PTPase) containing Src homology 2 regions (SHPTP2) in insulin signaling, either wild-type or mutant SHPTP2 (delta PTP; lacking full PTPase domain) was expressed in Rat 1 fibroblasts overexpressing human insulin receptors. In response to insulin, phosphorylation of insulin receptor substrate 1 (IRS-1), IRS-1-associated PTPase activities and phosphatidylinositol (PI) 3'-kinase activities were slightly enhanced in wild-type cells when compared with those in the parent cells transfected with hygromycin-resistant gene alone. In contrast, introduction of delta PTP inhibited insulin-induced association of IRS-1 with endogenous SHPTP2 and impaired both insulin-stimulated phosphorylation of IRS-1 and activation of PI 3'-kinase. Furthermore, decreased content of p85 subunit of PI 3'-kinase was also found in mutant cells. Consistently, the insulin-stimulated mitogen-activated protein kinase activities and DNA synthesis were also enhanced in wild-type cells, but impaired in mutant cells. Thus, the interaction of SHPTP2 with IRS-1 may be associated with modulation of phosphorylation levels of IRS-1, resulting in the changes of PI 3'-kinase and mitogen-activated protein kinase activity. Furthermore, an impaired insulin signaling in mutant cells may be partly reflected in a decreased content of p85 protein of PI 3'-kinase.
Ugi
S
S
Third Department of Medicine, Shiga University Science, Japan.
Maegawa
H
H
Kashiwagi
A
A
Adachi
M
M
Olefsky
J M
JM
Kikkawa
R
R
D000818:Animals; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
C526292:IRS1 protein, human; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; C526296:Irs1 protein, rat; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; D014443:Tyrosine; D005982:Glutathione Transferase; D011494:Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); 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