The major cytosolic substrate of the insulin receptor is a 185-kDa phosphoprotein (IRS-1) that contains multiple putative attachment sites for the p85α regulatory subunit of phosphatidylinositol 3'-kinase (PI3K). To examine the possible interaction of pp185 with p85α in vivo, we injected insulin or insulinomimetic agents (a combination of H2O2 and vanadate (H/V)) into the portal vein of anesthetized rats. In this model system, H/V treatment and, to a lesser extent, injection of insulin resulted in rapid and sustained tyrosine phosphorylation of multiple cellular proteins, including pp185/IRS-1. The latter was found to undergo specific association with the p85α regulatory subunit of PI3K but not with two other proteins that contain src homology domains. As p85α was not detectably phosphorylated on tyrosine residues and did not appear to interact directly with the insulin receptor, we conclude that tyrosine phosphorylation of pp185 promotes its association with p85α and the catalytic subunit of PI3K. The recruitment of the holoenzyme may also involve its enzymatic activation and thus constitute an important step in the transduction of insulin signals.
|Original language||English (US)|
|Number of pages||4|
|Journal||Journal of Biological Chemistry|
|State||Published - 1992|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology