Rac1 is signaling protein part of the Rho GTPase family it is involved in cell motility, cell growth and cytoskeletal reorganization. Rac1 activity is regulated by guanine nucleotide exchange factors (GEFs). GEFs cause the release of GDP, allowing GDP to bind and Rac1 to become activated. GTPase-activated proteins (GAPs) down regulate the activity of GEFs be stimulating the inactivation via binding of GDP to Rac1. Active Rac1 stimulates proteins (ie. Wiskott–Aldrich syndrome) leading to actin polymerization. Actin polymerization is also regulated by cofilin. PAK proteins are critical effectors to cytoskeleton reorganization. PAK1 phosphorylates and activates LIM kinase. LIM kinase then phosphorylates cofilin, inactivating it leading to reduced actin filament severing and depolymerization, therby increasing polymerized actin. Rac1 stimulates lamellipodia and filopodia formation which are involved in cell movement and sensing the environment. It is proposed that PAK1 is involved in the phosphorylation of myosin light chain affecting myosin light chain phosphorylation.

Rac 1 cell motility signaling pathway References