Wortmannin and LY294002 inhibit the insulin-induced down-regulation of IRS-1 in 3T3-L1 adipocytes

L. Keith Smith, Chris J. Vlahos, K. Kishta Reddy, J R Falck, Charles W. Garner

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

The insulin receptor substrate-1 (IRS-1) is expressed in 3T3-L1 adipocytes and is involved in at least some insulin responses, notably mitogenesis. Chronic exposure to insulin down regulates IRS-1 in these cells by stimulating its degradation (Rice, K.M., Turnbow, M.A. and Garner, C.W. (1993) Biochem. Biophys. Res. Commun. 190, 961-967). This insulin response was completely inhibited by wortmannin and LY294002 (2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one), two inhibitors of phosphatidylinositol 3-kinase (PI 3-kinase). Neither wortmannin nor LY294002 had any effect on the calcium-dependent degradation of IRS-1 in vitro nor did they inhibit the phosphorylation of IRS-1 on tyrosine in response to insulin in intact cells. Dioctanoyl phosphatidylinositol 3,4,5-trisphosphate (C8-PIP3), a synthetic dioctanoyl analog of the major product of PI 3-kinase, stimulated the calcium-dependent degradation of IRS-1 in vitro. In addition, neomycin, a cationic aminoglycoside antibiotic that binds to phosphoinositides, inhibited the insulin-induced down-regulation of IRS-1 in 3T3-L1 adipocytes and, also, the C8-PIP3-stimulated degradation of IRS-1 in vitro. These results suggest that PI 3-kinase and its 3-phosphoinositide products mediate the insulin-induced down-regulation of IRS-1 in 3T3-L1 adipocytes.

Original languageEnglish (US)
Pages (from-to)73-81
Number of pages9
JournalMolecular and Cellular Endocrinology
Volume113
Issue number1
DOIs
StatePublished - Aug 30 1995

Keywords

  • Calcium-dependent protease
  • IRS-1
  • LY294002
  • Phosphatidylinositol 3,4,5-trisphosphate
  • Phosphatidylinositol 3-kinase
  • Wortmannin

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Endocrinology

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