FIG. 8.

Reduced levels of RasGRP correlate with reduced activation of p21 Ras following ligation of BCR. (A) WEHI-231 B cells were exposed to 100 nM PMA and lysed after the indicated times, and the lysates were subjected to Western blotting with the indicated antibodies. (B) WEHI-231 cells were treated with 100 nM PMA overnight. The cells were lysed directly in SDS loading buffer, and the lysates were sonicated before analysis of the total expression of RasGRP, PKCδ, and actin by immunoblotting. (C) WEHI-231 cells were exposed to either dimethyl sulfoxide (DMSO) or PMA overnight and subsequently stimulated with 30 or 50 μg of anti-IgM/ml. Levels of activated endogenous p21 Ras were determined by pull-down assays with Raf-1 RBD. Cell lysates were also analyzed for RasGRP and p21 Ras. Similar results were obtained in two additional experiments.