FIG. 5.

Rac1 expression and activity are upregulated in Rac2-deficient mast cells. BMMCs from wild-type (WT) and Rac2^−/− C57BL/6 mice were stimulated with 10 ng of SCF per ml for 5 min. Mast cell lysates from 4 × 10⁶ cells were used in the GST-PAK effector pulldown assay. Levels of GTP-bound Rac1 protein were examined by immunoblot with antibody specific for Rac1 (upper panel). Immunoblot analysis of total Rac1 protein and total p38 MAPK (as a loading control) in wild-type and Rac2^−/− C57BL/6 BMMCs is shown in the middle and lower panels. Similar results were seen in three experiments.