Different pathways of postreceptor desensitization following chronic insulin treatment and in cells overexpressing constitutively active insulin receptors.
We have reported previously that substitution of the transmembrane domain of the insulin receptor with that of the erbB-2 oncogene (IRerbV-->E) results in constitutive activation of the insulin receptor kinase. Compared to NIH3T3 cells overexpressing wild-type insulin receptors (IRwt), cells overexpressing IRerbV-->E displayed a decrease in IRS-1 protein content by 55%, but basal tyrosine phosphorylation of IRS-1 was increased. This resulted in an increased association of IRS-1 with the p85 subunit of phosphatidylinositol 3-kinase, increased phosphatidylinositol 3-kinase activity in anti-IRS-1 immunoprecipitates, constitutive activation of p70 S6 protein kinase, and an increased association of Grb2 with Shc in the absence of ligand. However, Grb2 association with IRS-1 could not be detected in the basal or insulin-stimulated states, and mitogen-activated protein kinase (MAPK) activity could not be stimulated by insulin, epidermal growth factor, or platelet-derived growth factor. In contrast to IRerbV-->E, the insulin receptor content and its tyrosine phosphorylation were significantly decreased in IRwt cells chronically stimulated (>24 h) with insulin. With decreased IRS-1 content, tyrosine phosphorylation of IRS-1 was decreased by over 75%, leading to decreased IRS-1-associated PI 3-kinase and Grb2. In addition, Grb2 association with Shc and activation of MAPK and the p70 S6 kinase were insensitive to insulin stimulation. By contrast, association of Grb2 with Shc and activation of MAPK, but not the p70 S6 kinase, could be stimulated by epidermal growth factor or platelet-derived growth factor. These data suggest that there are multiple levels of postreceptor desensitization to insulin action. These are used somewhat differently in these two different models, probably due in part to the difference in receptor down-regulation.
Inoue
G
G
Research Division, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, and Harvard Medical School, Boston, Massachusetts 02215, USA.
Cheatham
B
B
Kahn
C R
CR
D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000378:metabolism; D051380:GRB2 Adaptor Protein; D007328:Insulin / Q000494:pharmacology*; D055504:Insulin Receptor Substrate Proteins; D051379:Mice; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D011972:Receptor, Insulin / Q000378:metabolism*; D019893:Ribosomal Protein S6 Kinases; D055765:Shc Signaling Adaptor Proteins; D015398:Signal Transduction; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D051380:GRB2 Adaptor Protein; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D017853:Phosphotransferases (Alcohol Group Acceptor); D010982:Platelet-Derived Growth Factor; D017346:Protein Serine-Threonine Kinases; D011506:Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; D011972:Receptor, Insulin; D019893:Ribosomal Protein S6 Kinases; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; C495949:Grb2 protein, mouse; C526295:Irs1 protein, mouse; C528034:Shc1 protein, mouse