The mechanism of PAK activation. Autophosphorylation events in both regulatory and kinase domains control activity.
The p21-activated kinases (PAKs), in common with many kinases, undergo multiple autophosphorylation events upon interaction with appropriate activators. The Cdc42-induced phosphorylation of PAK serves in part to dissociate the kinase from its partners PIX and Nck. Here we investigate in detail how autophosphorylation events affect the catalytic activity of PAK by altering the autophosphorylation sites in both alpha- and betaPAK. Both in vivo and in vitro analyses demonstrate that, although most phosphorylation events in the PAK N-terminal regulatory domain play no direct role in activation, a phosphorylation of alphaPAK serine 144 or betaPAK serine 139, which lie in the kinase inhibitory domain, significantly contribute to activation. By contrast, sphingosine-mediated activation is independent of this residue, indicating a different mode of activation. Thus two autophosphorylation sites direct activation while three others control association with focal complexes via PIX and Nck.
Glaxo-IMCB Group, Institute of Molecular and Cell Biology, 30 Medical Dr., Singapore 117609.
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D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001665:Binding Sites; D002384:Catalysis; D017124:Conserved Sequence; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011487:Protein Conformation; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012694:Serine; D013912:Threonine; D014162:Transfection; D020764:cdc42 GTP-Binding Protein; D054462:p21-Activated Kinases
D011994:Recombinant Proteins; D013912:Threonine; D012694:Serine; C515903:PAK1 protein, human; C515907:PAK2 protein, human; C515911:PAK3 protein, human; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D020764:cdc42 GTP-Binding Protein