title: Cdc42/Rac1-mediated activation primes PAK2 for superactivation by tyrosine phosphorylation.
abstract: The involvement of p21-activated kinases (PAKs) in important cellular processes such as regulation of the actin skeleton morphology, transduction of signals controlling gene expression, and execution of programmed cell death has directed attention to the regulation of the activity of these kinases. Here we report that activation of PAK2 by p21 GTPases can be strongly potentiated by cellular tyrosine kinases. PAK2 became tyrosine phosphorylated in its N-terminal regulatory domain, where Y130 was identified as the major phosphoacceptor site. Tyrosine phosphorylation-mediated superactivation of PAK2 could be induced by overexpression of different Src kinases or by inhibiting cellular tyrosine phosphatases with pervanadate and could be blocked by the Src kinase inhibitor PP1 or by mutating the Y130 residue. Analysis of PAK2 mutants activated by amino acid changes in the autoinhibitory domain or the catalytic domain indicated that GTPase-induced conformational changes, rather than catalytic activation per se, rendered PAK2 a target for tyrosine phosphorylation. Thus, PAK activation represents a potentially important point of convergence of tyrosine kinase- and p21 GTPase-dependent signaling pathways.
authors.affiliation: Institute of Medical Technology, FIN-33014 University of Tampere, Finland.
authors.forename: G Herma
authors.initials: GH
authors.lastname: Renkema
authors.forename: Kati
authors.initials: K
authors.lastname: Pulkkinen
authors.forename: Kalle
authors.initials: K
authors.lastname: Saksela
mesh_terms: D001665:Binding Sites / Q000502:physiology; D002384:Catalysis; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D011487:Protein Conformation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000502:physiology; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors; D015398:Signal Transduction / Q000502:physiology; D014443:Tyrosine / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*; D054462:p21-Activated Kinases; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D014443:Tyrosine; D019061:src-Family Kinases; C515907:PAK2 protein, human; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D017027:Protein Tyrosine Phosphatases; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein