Regulation of Actin Polymerization and Adhesion-Dependent Cell Edge Protrusion by the Abl-Related Gene (Arg) Tyrosine Kinase and N-WASp

摘要

Extracellular cues stimulate the Abl family nonreceptor tyrosine kinase Arg to promote actin-nbased cell edge protrusions. Several Arg-interacting proteins are potential links to the actin cytoskeleton, butnexactly how Arg stimulates actin polymerization and cellular protrusion has not yet been fully elucidated.Wenused affinity purification to identifyN-WASp as a novel binding partner of Arg.N-WASp activates the Arp2/3ncomplex and is an effector of Abl. We find that the Arg SH3 domain binds directly to N-WASp. Argnphosphorylates N-WASp on Y256, modestly increasing the affinity of Arg for N-WASp, an interaction thatndoes not require the Arg SH2 domain. The Arg SH3 domain stimulates N-WASp-dependent actinnpolymerization in vitro, and Arg phosphorylation of N-WASp weakly stimulates this effect. Arg andnN-WASp colocalize to adhesion-dependent cell edge protrusions in vivo. The cell edge protrusion defects ofnarg-/-fibroblasts can be complemented by re-expression of anArg-yellow fluorescent protein (YFP) fusion,nbut not by an N-WASp binding-deficient Arg SH3 domain point mutant. These results suggest that Argnpromotes actin-based protrusions in response to extracellular stimuli through phosphorylation of andnphysical interactions with N-WASp.