Effect of inhibitors against PI3K, Src family kinases and Btk on the tyrosine phosphorylation of Akt. Zymosan but not S. aureus induce tyrosine phosphorylation of Akt. This phosphorylation was affected by inhibitors against PI3K and Src family kinases. (A and C) Macrophages were stimulated for 30 min with either zymosan or heat killed S.aureus. (B) Macrophages were pretreated for 15 min with either PP2 (5 μM) or wortmannin (W, 100 nM), followed by stimulation with zymosan for 30 min. Cell lysates were processed for immunoblotting with the indicated antibody as described in Methods. The membrane was reprobed with ERK-2 antibody to verify equal loading of proteins. The data are representative of three separate experiments.