Scar/WAVE-1, a Wiskott-Aldrich syndrome protein, assembles an actin-associated multi-kinase scaffold

Abstract

WAVE proteins are members of the Wiskott–Aldrich syndrome protein (WASP) family of scaffolding proteins that coordinate actin reorganization by coupling Rho‐related small molecular weight GTPases to the mobilization of the Arp2/3 complex. We identified WAVE‐1 in a screen for rat brain A kinase‐anchoring proteins (AKAPs), which bind to the SH3 domain of the Abelson tyrosine kinase (Abl). Recombinant WAVE‐1 interacts with cAMP‐dependent protein kinase (PKA) and Abl kinases when expressed in HEK‐293 cells, and both enzymes co‐purify with endogenous WAVE from brain extracts. Mapping studies have defined binding sites for each kinase. Competition experiments suggest that the PKA–WAVE‐1 interaction may be regulated by actin as the kinase binds to a site overlapping a verprolin homology region, which has been shown to interact with actin. Immunocytochemical analyses in Swiss 3T3 fibroblasts suggest that the WAVE‐1 kinase scaffold is assembled dynamically as WAVE, PKA and Abl translocate to sites of actin reorganization in response to platelet‐derived growth factor treatment. Thus, we propose a previously unrecognized function for WAVE‐1 as an actin‐associated scaffolding protein that recruits PKA and Abl.