c-Abl Interacts with the WAVE2 Signaling Complex to Induce Membrane Ruffling and Cell Spreading

Abstract

The Wiskott-Aldrich syndrome-related protein WAVE2 promotes Arp2/3-dependent actin polymerization downstream of Rho-GTPase activation. The Abelson-interacting protein-1 (Abi-1) forms the core of the WAVE2 complex and is necessary for proper stimulation of WAVE2 activity. Here we have shown that the Abl-tyrosine kinase interacts with the WAVE2 complex and that Abl kinase activity facilitates interaction between Abl and WAVE2 complex members. We have characterized various interactions between Abl and members of the WAVE2 complex and revealed that Abi-1 promotes interaction between Abl and WAVE2 members. We have demonstrated that Abl-dependent phosphorylation of WAVE2 is necessary for its activation in vivo, which is highlighted by the findings that RNA interference of WAVE2 expression in Abl/Arg ؊/؊ cells has no additive effect on the amount of membrane ruffling. Furthermore, Abl phosphorylates WAVE2 on tyrosine 150, and WAVE2-deficient cells rescued with a Y150F mutant fail to regain their ability to ruffle and form microspikes, unlike cells rescued with wild-type WAVE2. Together, these data show that c-Abl activates WAVE2 via tyrosine phosphorylation to promote actin remodeling in vivo and that Abi-1 forms the crucial link between these two factors.

c-Abl-mediated Phosphorylation of WAVE3 Is Required for Lamellipodia Formation and Cell Migration

“…Leng and colleagues (30) reported that Tyr-150 is the only tyrosine residue to be phosphorylated in WAVE2 by c-Abl. Phosphorylation of WAVE2 by c-Abl was also shown to stimulate membrane ruffling and cell spreading, suggesting that WAVE2 might be an effector of the c-Abl kinase to regulate cytoskeletal remodeling in vivo (25). Here we show that the c-Abl-mediated phosphorylation of WAVE3 also results in the stimulation of lamellipodia formation and cell migration, which clearly supports the hypothesis that WAVE3 is also a downstream effector of c-Abl.…”

“…Treatment of MDA-MB-231 cells with STI-571, a specific inhibitor of c-Abl kinase activity, or expression of a kinase-dead Abl, inhibited the c-Abl-mediated phosphorylation of WAVE3, without abrogating their interaction, but resulted in a significant decrease in cell migration, clearly suggesting that the c-Abl-mediated phosphorylation of WAVE3 might be critical for the activity of WAVE3 in promoting cell migration. The interaction between c-Abl and the other members of the WAVE family of proteins has already been reported to involve the SH3 domain of c-Abl and the proline-rich domain of the WAVE proteins (25,32,35). The WAVE3-Abl interaction is more likely to involve the same region in WAVE3, because the proline-rich domain is very conserved among the WAVE proteins (5).…”

“…Ectopic expression of Abi1 showed that Abi1 might be required for the Abl activity to promote Abl-mediated phosphorylation of WAVE2 (30), which was shown to be necessary to link WAVE2 with actin polymerization and cytoskeleton remodeling at the cell periphery (25). Abi1 is also present in the macromolecular complex that includes WAVE3, a protein complex that is believed to regulate the activity of the WAVE proteins (14,36).…”

“…Phosphorylation of N-WASP/WASP proteins by non-receptor tyrosine kinases, such as ACK1 enhances the ability of WASP to stimulate actin polymerization (22), whereas growth factor stimulation of cultured cells results in hyper-phosphorylation of the WAVE proteins as well as a delay in their mobility in SDS-PAGE (23). WAVE1 was shown to be phosphorylated by the cyclindependent kinase 5 (24), whereas phosphorylation of WAVE2 has recently been shown to involve the non-receptor tyrosine kinase c-Abl (25), resulting in both cases in the stimulation of membrane ruffling and cell spreading. Whether the activity of WAVE3 is regulated in a similar manner is not known.…”

Regulation of cell migration and morphogenesis by Abl-family kinases: emerging mechanisms and physiological contexts

“…The inhibitory-complex component Abi1 plays a central role in WAVE2 phosphorylation (Innocenti et al, 2004), because it acts as a bridge between WAVE2 and Abl (Leng et al, 2005;Stuart et al, 2006), allowing Abl to phosphorylate WAVE2 in response to PDGF or to adhesion to fibronectin (Fig. 3A).…”