Molecular mechanism of insulin-induced degradation of insulin receptor substrate 1

Mol Cell Biol. 2002 Feb;22(4):1016-26. doi: 10.1128/mcb.22.4.1016-1026.2002.

Abstract

Insulin receptor substrate 1 (IRS-1) plays an important role in the insulin signaling cascade. In vitro and in vivo studies from many investigators have suggested that lowering of IRS-1 cellular levels may be a mechanism of disordered insulin action (so-called insulin resistance). We previously reported that the protein levels of IRS-1 were selectively regulated by a proteasome degradation pathway in CHO/IR/IRS-1 cells and 3T3-L1 adipocytes during prolonged insulin exposure, whereas IRS-2 was unaffected. We have now studied the signaling events that are involved in activation of the IRS-1 proteasome degradation pathway. Additionally, we have addressed structural elements in IRS-1 versus IRS-2 that are required for its specific proteasome degradation. Using ts20 cells, which express a temperature-sensitive mutant of ubiquitin-activating enzyme E1, ubiquitination of IRS-1 was shown to be a prerequisite for insulin-induced IRS-1 proteasome degradation. Using IRS-1/IRS-2 chimeric proteins, the N-terminal region of IRS-1 including the PH and PTB domains was identified as essential for targeting IRS-1 to the ubiquitin-proteasome degradation pathway. Activation of phosphatidylinositol 3-kinase is necessary but not sufficient for activating and sustaining the IRS-1 ubiquitin-proteasome degradation pathway. In contrast, activation of mTOR is not required for IRS-1 degradation in CHO/IR cells. Thus, our data provide insight into the molecular mechanism of insulin-induced activation of the IRS-1 ubiquitin-proteasome degradation pathway.

Publication types

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

MeSH terms

  • Animals
  • Antibiotics, Antineoplastic / pharmacology
  • CHO Cells
  • Chromones / pharmacology
  • Cricetinae
  • Cysteine Endopeptidases / metabolism*
  • Enzyme Activation
  • Enzyme Inhibitors / pharmacology
  • Humans
  • Immunoblotting
  • Insulin / metabolism*
  • Insulin / pharmacology
  • Insulin Receptor Substrate Proteins
  • Morpholines / pharmacology
  • Multienzyme Complexes / metabolism*
  • Oligopeptides / pharmacology
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphoproteins / genetics
  • Phosphoproteins / metabolism*
  • Phosphorylation
  • Proteasome Endopeptidase Complex
  • Protein Structure, Tertiary
  • Protein-Serine-Threonine Kinases*
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-akt
  • Receptor, Insulin / genetics
  • Receptor, Insulin / metabolism
  • Recombinant Fusion Proteins / metabolism
  • Signal Transduction* / drug effects
  • Sirolimus / pharmacology
  • Ubiquitin / metabolism

Substances

  • Antibiotics, Antineoplastic
  • Chromones
  • Enzyme Inhibitors
  • IRS1 protein, human
  • Insulin
  • Insulin Receptor Substrate Proteins
  • Morpholines
  • Multienzyme Complexes
  • Oligopeptides
  • Phosphoproteins
  • Proto-Oncogene Proteins
  • Recombinant Fusion Proteins
  • Ubiquitin
  • 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
  • Phosphatidylinositol 3-Kinases
  • Receptor, Insulin
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Cysteine Endopeptidases
  • Proteasome Endopeptidase Complex
  • Sirolimus
  • epoxomicin