p-PAK4 (93.Ser 474) Antibody: sc-135775

p-PAK4 Background Information
Three recently identified isoforms of serine/threonine kinases, designated åPAK p68, ∫PAK p65 and ©PAK p62, have been shown to exhibit a high degree of sequence homology with the S. cerevisiae kinase STE20, involved in pheromone signaling. The å, ∫ and ©PAK isoforms complex specifically with Rac1 and Cdc42 in their active GTP bound state, inhibiting their intrinsic GTPase activity leading to their autophosphorylation. Once phosphorylated and their affinity for Rac/Cdc42 reduced, the PAK isoforms disassociate from the complex to seek downstream substrates. One such putative substrate is MEK kinase, an upstream effector of MEK4 which is involved in the JNK signaling pathway. While the PAK isoforms interact in a GTP-dependent manner with Rac1 and Cdc42, they do not interact with Rho. PAK4 is highly expressed in prostate, testis and colon. PAK4 interacts tightly with GTP-bound but not GDP-bound CDC42 and weakly with RAC. PAK4 phosphorylates and autophosphorylates and also activates the JNK pathway. Coexpression of PAK4 and activated CDC42 induces the sustained formation of actin-enriched filopodia protrusions and causes PAK4 to colocalize with polymerized actin clusters and with beta coat protein in the Golgi. The gene which encodes PAK4 maps to human chromosome 19.