Figure 4.

IRS-1 is the main docking protein for PI 3-kinase in human adipocytes. Adipocytes from healthy control subjects were incubated for 10 min with different concentrations of insulin. Cell lysates were immunoprecipitated with anti-IRS-1 C-terminal antibodies (A) or anti-IRS-2 antibodies (B) separated on 7.5% SDS-PAGE and immunoblotted with the indicated antibodies. (C) PI 3-kinase activity was assayed on immunoprecipitates produced by the indicated antibodies as described in Fig. 3. (D) Quantification of the PI 3-kinase activity using a PhosphorImager (Molecular Dynamics).