Tyr(612) and Tyr(632) in Human Insulin Receptor substrate-1 Are Important for Full Activation of Insulin-Stimulated Phosphatidylinositol 3-kinase Activity and Translocation of GLUT4 in Adipose Cells

Endocrinology. 2001 Jul;142(7):2833-40. doi: 10.1210/endo.142.7.8283.

Abstract

To examine contributions of specific YXXM motifs in human insulin receptor substrate-1 (IRS-1) to mediating the metabolic actions of insulin, we studied IRS-1 mutants containing various substitutions of Phe for Tyr. In transfected NIH-3T3(IR) cells, insulin stimulation caused a 5-fold increase in phosphatidylinositol 3-kinase (PI3K) activity coimmunoprecipitated with wild-type IRS-1. No PI3K activity was associated with IRS1-F6 (Phe substituted for Tyr at positions 465, 612, 632, 662, 941, and 989). Adding back both Tyr(612) and Tyr(632) fully restored IRS-1-associated PI3K activity, whereas adding back either Tyr(612) or Tyr(632) alone was associated with intermediate PI3K activity. In rat adipose cells transfected with epitope-tagged GLUT4, insulin stimulation caused a 2-fold increase in cell surface GLUT4-HA. Cotransfection of cells with GLUT4-HA and either wild-type IRS-1 or IRS1-Y612/Y632 increased basal cell surface GLUT4-HA (in the absence of insulin) to approximately 80% of the levels seen in insulin-stimulated control cells, whereas overexpression of IRS1-F6 had no effect on the insulin dose-response curve. Overexpression of IRS1-Y612 or IRS1-Y632 caused intermediate effects. Thus, both Tyr(612) and Tyr(632) are important for IRS-1 to fully activate PI3K and mediate translocation of GLUT4 in response to insulin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3 Cells
  • Adipocytes / metabolism*
  • Amino Acid Sequence
  • Animals
  • Biological Transport / physiology
  • Enzyme Activation
  • Glucose Transporter Type 4
  • Humans
  • Insulin / pharmacology*
  • Insulin Receptor Substrate Proteins
  • Male
  • Mice
  • Monosaccharide Transport Proteins / metabolism*
  • Muscle Proteins*
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Phosphoproteins / genetics*
  • Phosphoproteins / physiology*
  • Rats

Substances

  • Glucose Transporter Type 4
  • IRS1 protein, human
  • Insulin
  • Insulin Receptor Substrate Proteins
  • Irs1 protein, mouse
  • Irs1 protein, rat
  • Monosaccharide Transport Proteins
  • Muscle Proteins
  • Phosphoproteins
  • SLC2A4 protein, human
  • Slc2a4 protein, mouse
  • Slc2a4 protein, rat
  • Phosphatidylinositol 3-Kinases