Insulin receptor substrate-2-dependent interleukin-4 signaling in macrophages is impaired in two models of type 2 diabetes mellitus

J Biol Chem. 2004 Jul 2;279(27):28045-50. doi: 10.1074/jbc.M404368200. Epub 2004 Apr 27.


We have shown previously that hyperinsulinemia inhibits interferon-alpha-dependent activation of phosphatidylinositol 3-kinase (PI3-kinase) through mammalian target of rapamycin (mTOR)-induced serine phosphorylation of insulin receptor substrate (IRS)-1. Here we report that chronic insulin and high glucose synergistically inhibit interleukin (IL)-4-dependent activation of PI3-kinase in macrophages via the mTOR pathway. Resident peritoneal macrophages (PerMPhis) from diabetic (db/db) mice showed a 44% reduction in IRS-2-associated PI3-kinase activity stimulated by IL-4 compared with PerMPhis from heterozygote (db/+) control mice. IRS-2 from db/db mouse PerMPhis also showed a 78% increase in Ser/Thr-Pro motif phosphorylation without a difference in IRS-2 mass. To investigate the mechanism of this PI3-kinase inhibition, 12-O-tetradecanoylphorbol-13-acetate-matured U937 cells were treated chronically with insulin (1 nm, 18 h) and high glucose (4.5 g/liter, 48 h). In these cells, IL-4-stimulated IRS-2-associated PI3-kinase activity was reduced by 37.5%. Importantly, chronic insulin or high glucose alone did not impact IL-4-activated IRS-2-associated PI3-kinase. Chronic insulin + high glucose did reduce IL-4-dependent IRS-2 tyrosine phosphorylation and p85 association by 54 and 37%, respectively, but did not effect IL-4-activated JAK/STAT signaling. When IRS-2 Ser/Thr-Pro motif phosphorylation was examined, chronic insulin + high glucose resulted in a 92% increase in IRS-2 Ser/Thr-Pro motif phosphorylation without a change in IRS-2 mass. Pretreatment of matured U937 cells with rapamycin blocked chronic insulin + high glucose-dependent IRS-2 Ser/Thr-Pro motif phosphorylation and restored IL-4-dependent IRS-2-associated PI3-kinase activity. Taken together these results indicate that IRS-2-dependent IL-4 signaling in macrophages is impaired in models of type 2 diabetes mellitus through a mechanism that relies on insulin/glucose-dependent Ser/Thr-Pro motif serine phosphorylation mediated by the mTOR pathway.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Motifs
  • Animals
  • Blood Glucose / metabolism
  • Blotting, Western
  • Cell Line
  • Diabetes Mellitus, Type 2 / metabolism*
  • Glucose / metabolism
  • Heterozygote
  • Humans
  • Insulin / blood
  • Insulin / metabolism
  • Insulin Receptor Substrate Proteins
  • Interleukin-4 / metabolism*
  • Intracellular Signaling Peptides and Proteins
  • Macrophages / metabolism*
  • Macrophages, Peritoneal / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphoproteins / metabolism*
  • Phosphorylation
  • Serine / chemistry
  • Signal Transduction*
  • Sirolimus / pharmacology
  • Tetradecanoylphorbol Acetate
  • Time Factors
  • Tyrosine / metabolism
  • U937 Cells


  • Blood Glucose
  • IRS2 protein, human
  • Insulin
  • Insulin Receptor Substrate Proteins
  • Intracellular Signaling Peptides and Proteins
  • Irs2 protein, mouse
  • Phosphoproteins
  • Interleukin-4
  • Tyrosine
  • Serine
  • Phosphatidylinositol 3-Kinases
  • Glucose
  • Tetradecanoylphorbol Acetate
  • Sirolimus