title: PAK4 is activated via PI3K in HGF-stimulated epithelial cells.
abstract: The p21-activated kinases (PAKs) are divided into two subgroups based on sequence homology. Group 1 PAKs (PAK1-3) are involved in cell migration, and are activated by pro-migratory stimuli and by Cdc42/Rac GTPases. In contrast, little is known about the regulation of the recently identified group II PAKs (PAK4-6). Here we report that PAK4 is activated by HGF, a migratory stimulus for epithelial cells. In unstimulated MDCK cells, activated PAK4 induces a decrease in stress fibres, and when cells are stimulated with HGF, it induces a loss of focal complexes and cell rounding. This response is dependent on PAK4 kinase activity but does not require Cdc42 interaction. Activated PAK4 localises to the cell periphery but not specifically in lamellipodia, and HGF induces localisation of wild-type PAK4 to the cell periphery. LY294002, a phosphoinositide 3-kinase (PI3K) inhibitor, inhibits HGF-induced PAK4 kinase activation, relocalisation, and cell rounding. However, the isolated C-terminal kinase domain of PAK4 can induce cell rounding in the presence of LY294002, suggesting that the N-terminal region acts as a negative regulator of PAK4 activity. These results indicate that HGF stimulates PAK4 through PI3K, and that PAK4 could contribute to HGF-induced changes in actin organisation and cell-substratum adhesion.
authors.affiliation: Ludwig Institute for Cancer Research, Royal Free and University College Medical School Branch, 91 Riding House Street, London WIW 7BS, UK.
authors.forename: Claire M
authors.initials: CM
authors.lastname: Wells
authors.forename: Arie
authors.initials: A
authors.lastname: Abo
authors.forename: Anne J
authors.initials: AJ
authors.lastname: Ridley
mesh_terms: D000199:Actins / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects; D002460:Cell Line; D048429:Cell Size / Q000187:drug effects; D002867:Chromones / Q000494:pharmacology; D004285:Dogs; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D017228:Hepatocyte Growth Factor / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism; D007668:Kidney / Q000166:cytology; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000187:drug effects / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012697:Serine Endopeptidases / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D000199:Actins; D002867:Chromones; D004791:Enzyme Inhibitors; D017228:Hepatocyte Growth Factor; D007527:Isoenzymes; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D012697:Serine Endopeptidases; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C081092:HGF activator