p21-activated kinases

(= PAK-1, 2, 3)

Serine/threonine protein kinases of the STE20 subfamily. Form an activated complex with GTP-bound ras-like proteins (p21, cdc2 and rac1). Activated, autophosphorylated PAK acts on a variety of targets, shows highly specific binding to the SH3 domains of phospholipase C g and of adapter protein nck, and regulates various morphological and cytoskeletal changes. Caspase-mediated cleavage of 62 kD PAK2 generates a constitutively-active catalytic fragment (34 kD) and induces apoptosis in Jurkat cells. Its activity is apparently essential for the formation of apoptotic bodies.