Activation of Rac-1 stimulated by hemopoietic growth factors acting through receptor tyrosine kinases.

(A) MC/9 cells were stimulated with SLF (50 ng/mL), (B) BMMCs from BDF1 mice were stimulated with SLF (50 ng/mL), or (C) WEHI 274.3 cells were stimulated with CSF-1 (200 ng/mL) for the indicated number of minutes or with PBS for 5 minutes (con). Following stimulation, lysates were assayed for GTP-bound/activated endogenous Rac-1 (Rac-1 GTP) as specified earlier. Immunoblots were performed using a Rac-1–specific monoclonal antibody. One half of the total GTP-bound Rac-1 precipitated was run in immunoblots for cells described in panels A, B, and C. The WCLs corresponded to 1.9%, 2.6%, and 2.1% of the total Rac-1 available for precipitation from cells in panels A, B, and C, respectively.