Identification of two human WAVE/SCAR homologues as general actin regulatory molecules which associate with the Arp2/3 complex.

WAVE/SCAR protein was identified as a protein which has similarity to WASP and N-WASP, especially in its C terminal. Recently, WAVE/SCAR protein has been shown to cooperate with the Arp2/3 complex, a nucleation core for actin polymerization in vitro. However, in spite of its general function, WAVE/SCAR expression is mainly restricted to the brain, suggesting the existence of related molecule(s). We here identified two human WAVE/SCAR homologues, which cover other organs. We named the original WAVE1 and newly identified ones WAVE2 and WAVE3. WAVE2 had a very wide distribution with strong expression in peripheral blood leukocytes and mapped on chromosome Xp11.21, next to the WASP locus. WAVE3 and WAVE1 had similar distributions. WAVE3 was strongly expressed in brain and mapped on chromosome 13q12. WAVE1 was mapped on chromosome 6q21-22. Ectopically expressed WAVE2 and WAVE3 induced actin filament clusters in a similar manner with WAVE1. These actin cluster formations were suppressed by deletion of their C-terminal VPH (verproline homology)/WH2 (WASP homology 2) domain. Further, WAVE2 and WAVE3 associate with the Arp2/3 complex as does WAVE1. Our identification of WAVE homologues suggests that WAVE family proteins have general function for regulating the actin cytoskeleton in many tissues.