Figure 3.

Overexpression of the p85 subunit of PI 3-kinase inhibits Src-induced tyrosine phosphorylation of ITK. ITK immunoprecipitates from COS-7 cells transfected with HA-tagged wild-type ITK in the presence or absence of c-Src and the p85 subunit of PI 3-kinase as indicated, were analyzed for phosphotyrosine (Top). Lanes: 1, ITK without c-Src; 2 and 3, ITK with c-Src; 3, ITK with c-Src and p85. (Upper Middle) Anti-HA immunoblot of the first panel demonstrating expression of ITK. (Lower Middle) Whole cell lysates probed for Src. (Bottom) Whole cell lysates probed for p85. Arrows indicate ITK, Src, and p85, respectively.