PAK4, Active

PAK4 is a recently identified member of the p21-activated kinases (PAKs) which have been implicated in the regulation of cell morphology, motility and transformation. These serine/threonine kinases are activated by and are effectors of small GTPases, cdc 42 and Rac. PAK4 belongs to the Group II PAKs which also includes PAK5 and PAK6 while Group I PAKs comprise of PAK1, PAK2 and PAK3. PAK4 differs from other members of the PAK family both in sequence and function. PAK4 has been shown to regulate cell morphology and cytoskeletal organization in mammalian cells. PAK4 regulates the activity of LIM kinase 1 which in turn phosphorylates Cofilin leading to cytoskeletal changes. PAK4 can protect cells from apoptosis in response to several different types of stimuli by inhibiting the pro-apoptotic proteins Bad and Caspase 8. PAK4 has been shown to associate with and mediate the downstream signaling of the keratinocyte growth factor receptor. In addition, PAK4 interacts with the β5 integrins and regulates cell migration during engagement of the αvβ5 integrin receptor.