FIGURE 4.

Rac activity is required for PI3K activation. A, YT cells were preincubated with EHT 1864 or control. YT cells were stimulated with C. neoformans for the indicated times. The levels of pAkt and Akt2 were determined by immunoblots. The immunoblot is representative of two experiments. B, YT cells were preincubated with Rac inhibitor II. YT cells were then stimulated with Cryptococcus, and levels of pAkt and Akt2 were determined by immunoblots. Densitometry is the mean of four experiments ± S.E. C, YT cells were transfected with Rac siRNA. Transfected YT cells were stimulated with Cryptococcus, and the levels of pAkt were determined by immunoblots. The immunoblot is representative of three experiments. Densitometry is the mean of three experiments ± S.E. D and E, YT cells were preincubated with 50 μm Ly294002 or DMSO control. D, levels of active Rac bound to GTP were measured by Rac-GTP pulldown assay and Rac1 immunoblotting. Aliquots of whole cell lysate were immunoblotted to determine the total amount of Rac1. The immunoblot is representative of three experiments. E, levels of phosphorylated Akt and Akt 2 were determined by immunoblots. The immunoblot is representative of two experiments. YT, unstimulated YT cells alone; C+YT, YT cells stimulated with Cryptococcus; ns, no significant difference. *, p < 0.05; **, p < 0.01.