Effect of PF4 on the activation of small GTPases Rac2 and RhoA. Neutrophils were stimulated for the indicated time periods, and activated (GTP-bound) GTPases Rac2 (A) and RhoA (B) were precipitated using PAK-1 binding domain or Rhotekin binding domain, respectively, and were detected by Western blot analysis using anti-Rac2 (A) or anti-RhoA (B) antibodies. Bands were visualized by Odyssey infrared imaging system. An aliquot of the same lysates was tested to confirm equal protein loading (bottom blots of each panel). Data from 1 of 3 representative experiments are given.