FIGURE 8.

Distinct p110 isoforms mediate basal versus growth factor-stimulated PI3K activity. PC3 (A) or LNCaP (C) cells in 24-well plates were transfected with siRNAs for each p110 isoform. After serum starvation for 1–2 days, cells were lysed, and 10 μg of cell lysates were subjected to immunoblotting for each p110 isoform, pAkt, total Akt, or β-tubulin. Results are quantified in bar graphs and are representative of 2–3 independent experiments for each cell type (in addition to results in E and F). PC3 (B) or LNCaP (D) transfected with siRNAs for each p110 isoform were serum-starved for 1–2 days, followed by HRG-β1 stimulation (100 ng/ml, 15 min). Cell lysates were then subjected to immunoblotting as indicated. E and F, PC3 or LNCaP cells, respectively, were transfected with siRNAs for each p110 isoform or with both p110β and -δ siRNA and were then analyzed by immunoblotting after serum starvation for 2 days.