Activation of PAK by Rac1 and Rac1 S71E.

<p>The effect of Rac1 and Rac1 S71E on PAK phosphorylation was shown in HEp2 cells stably expressing either GTPase. A) A brief characterization of these stable transfected cell lines was done by scanning electron microscopy showing surface topology of the cells. B) Immunoblot analysis revealed comparable ectopic expression of HA-tagged Rac1 and Rac1 S71E and concomitant Ser-144 phosphorylation of PAK1 and Thr-402 phosphorylation of PAK2. C) densitometrical evaluation of three separate Immunoblots showing phosphorylation of PAK 1/2. Shown are mean values ± SD. D) Propidium iodide staining of stable cell lines indicates populations of cells with 2n (G1 phase) or 4n (G2/M phase) set of chromosomes. Shown are percentages of cells within different cell cycle phases (mean values of five separate experiments).