Fig. 2. Polypeptide growth factor stimulation of SCLC cell lines induces the recruitment of p85 to phosphotyrosine-containing signalling complexes. (A–D) SCLC cells were treated with SCF (10 ng/ml), HGF (10 ng/ml), insulin (3 µg/ml) or FGF-2 (1 ng/ml) for 5 min at 37°C. Anti-phosphotyrosine immunoprecipitates were analysed by western blotting with antibodies specific for the proteins indicated. In some cases lysates of the respective SCLC cell lines were analysed in parallel as positive controls (lys). (E) Lysates from SCLC cells prepared as in (A) were immunoprecipitated with antibodies against different receptors, and samples analysed by western blotting with anti-p85 antibodies. (F) SCLC cells (as indicated) were treated with SCF (10 ng/ml) for 5 min at 37°C. Anti-phosphotyrosine immunoprecipitates were assayed for in vitro PI3K activity. Radioactive phospholipids were separated by thin layer chromatography, and spots visualized by autoradiography.