The activity of the Wiskott-Aldrich syndrome-related WAVE3 protein is critical for the regulation of the Arp2/3-dependent cytoskeleton organization downstream of Rac-GTPase. The Ableson (Abl) non-receptor tyrosine kinase is also involved in the remolding of actin cytoskeleton in response to extracellular stimuli. Here we show that platelet-derived growth factor stimulation of cultured cells results in WAVE3-Abl interaction and localization to the cell periphery. WAVE3-Abl interaction promotes

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... e tyrosine phosphorylation of WAVE3 by Abl, and STI-571, a specific inhibitor of Abl kinase activity, abrogates the Abl-mediated phosphorylation of WAVE3. We have also shown that Abl targets and phosphorylates four tyrosine residues in WAVE3 and that the Abl-dependent phosphorylation of WAVE3 is critical for the stimulation of lamellipodia formation and cell migration. Our results show that the activation of WAVE3 to promote actin remodeling is enhanced by the c-Ablmediated tyrosine phosphorylation of WAVE3.