Effector protein for Rho-type GTPases, providing a link with the Arp2/3 complex that regulates the structure and dynamics of the actin cytoskeleton. Important for efficient actin polymerization. Possible regulator of lymphocyte and platelet function.
Expressed predominantly in the thymus. Also found, to a much lesser extent, in the spleen.
Defects in WAS are the cause of Wiskott-Aldrich syndrome (WAS) [MIM:301000]; also known as eczema-thrombocytopenia-immunodeficiency syndrome. WAS is an X-linked recessive immunodeficiency characterized by eczema, thrombocytopenia, recurrent infections, and bloody diarrhea. Death usually occurs before age 10. Defects in WAS are the cause of thrombocytopenia type 1 (THC1) [MIM:313900]. Thrombocytopenia is defined by a decrease in the number of platelets in circulating blood, resulting in the potential for increased bleeding and decreased ability for clotting. Defects in WAS are a cause of neutropenia severe congenital X-linked (XLN) [MIM:300299]. XLN is an immunodeficiency syndrome characterized by recurrent major bacterial infections, severe congenital neutropenia, and monocytopenia.
The WH1 (Wasp homology 1) domain may bind a Pro-rich ligand. The CRIB (Cdc42/Rac-interactive-binding) region binds to the C-terminal WH2 domain in the autoinhibited state of the protein. Binding of Rho-type GTPases to the CRIB induces a conformation change and leads to activation.