A novel T608R missense mutation in insulin receptor substrate-1 identified in a subject with type 2 diabetes impairs metabolic insulin signaling

J Clin Endocrinol Metab. 2003 Apr;88(4):1468-75. doi: 10.1210/jc.2002-020933.


Naturally occurring mutations in insulin receptor substrate-1 (IRS-1) have previously been implicated in impaired insulin action. We now report a novel mutation in IRS-1 with substitution of Arg for Thr(608) that was identified in a patient with type 2 diabetes mellitus. We detected the T608R mutation in 1 of 136 chromosomes from diabetic patients and in 0 of 120 chromosomes from nondiabetic controls, suggesting that this is a rare IRS-1 variant. Conservation of Thr(608) in human, monkey, rat, mouse, and chicken IRS-1 sequences is consistent with a crucial function for this residue. Moreover, Thr(608) is located near the YMXM motif containing Tyr(612) that is important for binding and activation of phosphoinositol 3-kinase (PI 3-kinase). To investigate whether the T608R mutation impairs insulin signaling, we transiently transfected NIH-3T3(IR) cells with hemagglutinin-tagged wild-type or T608R mutant IRS-1 constructs. Recombinant IRS-1 immunoprecipitated from transfected cells treated with or without insulin was subjected to immunoblotting for the p85 regulatory subunit of PI 3-kinase as well as a PI 3-kinase assay. As expected, in control cells transfected with wild-type IRS-1, insulin stimulation caused an increase in p85 coimmunoprecipitated with IRS-1 as well as a 10-fold increase in IRS-1-associated PI 3-kinase activity. Interestingly, when cells transfected with IRS1-T608R were stimulated with insulin, both the amount of p85 coimmunoprecipitated with IRS1-T608R as well as the associated PI 3-kinase activity were approximately 50% less than those observed with wild-type IRS-1. Moreover, in rat adipose cells, overexpression of IRS1-T608R resulted in significantly less translocation of GLUT4 to the cell surface than comparable overexpression of wild-type IRS-1. We conclude that a naturally occurring substitution of Arg for Thr(608) in IRS-1 is a rare human mutation that may contribute to insulin resistance by impairing metabolic signaling through PI 3-kinase-dependent pathways.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3 Cells
  • Adipocytes / metabolism
  • Amino Acid Sequence
  • Animals
  • Diabetes Mellitus, Type 2 / genetics*
  • Glucose Transporter Type 4
  • Humans
  • Immunosorbent Techniques
  • Insulin / metabolism*
  • Insulin / pharmacology
  • Insulin Receptor Substrate Proteins
  • Insulin Resistance / genetics
  • Male
  • Mice
  • Middle Aged
  • Monosaccharide Transport Proteins / metabolism
  • Muscle Proteins*
  • Mutation, Missense*
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphoproteins / chemistry
  • Phosphoproteins / genetics*
  • Polymorphism, Single-Stranded Conformational
  • Rats
  • Signal Transduction*
  • Transfection


  • 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