The Gly-->Arg972 amino acid polymorphism in insulin receptor substrate-1 affects glucose metabolism in skeletal muscle cells

J Clin Endocrinol Metab. 2000 May;85(5):2004-13. doi: 10.1210/jcem.85.5.6608.

Abstract

Molecular scanning of insulin receptor substrate-1 (IRS-1) revealed several amino acid substitutions. The most common IRS-1 variant, a Gly to Arg972 change, is more prevalent among type 2 diabetic patients. In this study we overexpressed wild-type and Arg972IRS-1 variant in L6 skeletal muscle cells and examined the functional consequences of this polymorphism on insulin metabolic signaling. L6 cells expressing Arg972-IRS-1 (L6-Arg972) showed a decrease in insulin-stimulated IRS-1-associated phosphatidylinositol 3-kinase (PI 3-kinase) activity compared with L6 cells expressing wild-type IRS-1 (L6-WT) as a consequence of decreased binding of p85 subunit of PI 3-kinase to IRS-1. L6-Arg972 exhibited a decrease in both basal and insulin-stimulated glucose transport due to a reduction in the amount of both GLUT1 and GLUT4 translocated to the plasma membrane. Both basal and insulin-stimulated Akt phosphorylations were decreased in L6-Arg972 compared with L6-WT. Basal glycogen synthase kinase-3 (GSK-3) activity was increased in L6-Arg972 compared with L6-WT, and insulin-induced inactivation of GSK-3 was also reduced in L6-Arg972. This change was associated with a significant decrease in insulin-stimulated glucose incorporation into glycogen and glycogen synthase activity in L6-Arg972 compared with L6-WT. These results indicate that the Arg972-IRS-1 polymorphism impairs the ability of insulin to stimulate glucose transport, glucose transporter translocation, and glycogen synthesis by affecting the PI 3-kinase/Akt/GSK-3 signaling pathway. The present data indicate that the polymorphism at codon 972 of IRS-1 may contribute to the in vivo insulin resistance observed in carriers of this variant.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Substitution
  • Animals
  • Arginine
  • Cell Line
  • Cell Membrane / metabolism
  • Genetic Variation*
  • Glucose / metabolism*
  • Glucose Transporter Type 1
  • Glucose Transporter Type 4
  • Glycine
  • Glycogen / biosynthesis
  • Humans
  • Insulin / metabolism*
  • Insulin / pharmacology
  • Insulin Receptor Substrate Proteins
  • Kinetics
  • Monosaccharide Transport Proteins / metabolism
  • Muscle Proteins*
  • Muscle, Skeletal / drug effects
  • Muscle, Skeletal / metabolism*
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphoproteins / genetics*
  • Phosphorylation
  • Polymorphism, Genetic*
  • Protein-Serine-Threonine Kinases*
  • Protein-Tyrosine Kinases / metabolism
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-akt
  • Receptor, Insulin / metabolism
  • Recombinant Proteins / metabolism
  • Transfection

Substances

  • Glucose Transporter Type 1
  • Glucose Transporter Type 4
  • IRS1 protein, human
  • Insulin
  • Insulin Receptor Substrate Proteins
  • Monosaccharide Transport Proteins
  • Muscle Proteins
  • Phosphoproteins
  • Proto-Oncogene Proteins
  • Recombinant Proteins
  • SLC2A1 protein, human
  • SLC2A4 protein, human
  • Glycogen
  • Arginine
  • Phosphatidylinositol 3-Kinases
  • Protein-Tyrosine Kinases
  • Receptor, Insulin
  • AKT1 protein, human
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Glucose
  • Glycine