FIG. 3.
Serine/threonine phosphorylation of IRS-1 and IRS-CAAX. 32DIR cell lines matched for IR and IRS isoform expression were starved for 4 h and then incubated for 5 min in the presence or absence of TPA (1 μg/ml) or 100 nM insulin. The cells were lysed, and lysates were immunoprecipitated (IP) with anti-IRS-1. Immunoprecipitated proteins were resolved by SDS-PAGE, transferred to nitrocellulose, and immunoblotted with anti-IRS-1 (top panel) or antiphosphoserine/antiphosphothreonine (bottom panel). The results shown are typical of multiple independent experiments. Molecular weights are given on the left in thousands.