title: Phosphorylation of Pak1 by the p35/Cdk5 kinase affects neuronal morphology.
abstract: The small GTPase Rac and its effectors, the Pak1 and p35/Cdk5 kinases, have been assigned important roles in regulating cytoskeletal dynamics in neurons. Our previous work revealed that the neuronal p35/Cdk5 kinase associates with Pak1 in a RacGTP-dependent manner, causing hyperphosphorylation and down-regulation of Pak1 kinase activity. We have now demonstrated direct phosphorylation of Pak1 on threonine 212 by the p35/Cdk5 kinase. In neuronal growth cones, Pak1 phosphorylated on Thr-212 localized to actin and tubulin-rich areas, suggesting a role in regulating growth cone dynamics. The expression of a non-phosphorylatable Pak1 mutant (Pak1A212) induced dramatic neurite disorganization. We also observed a strong association between p35/Cdk5 and the Pak1 C-terminal kinase domain. Overall, our data show that in neurons, membrane-associated, active Pak1 is regulated by the p35/Cdk5 kinase both by association and phosphorylation, which is essential for the proper regulation of the cytoskeleton during neurite outgrowth and remodeling.
authors.affiliation: Molecular and Developmental Neurobiology Medical Research Council Centre, New Hunt's House, King's College London, London, SE1 1UL, United Kingdom.
authors.forename: T
authors.initials: T
authors.lastname: Rashid
authors.forename: M
authors.initials: M
authors.lastname: Banerjee
authors.forename: M
authors.initials: M
authors.lastname: Nikolic
mesh_terms: D000818:Animals; D048429:Cell Size; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D051360:Cyclin-Dependent Kinase 5; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism*; D020439:Growth Cones / Q000378:metabolism*; D007150:Immunohistochemistry; D051379:Mice; D008954:Models, Biological; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D054462:p21-Activated Kinases; D020744:rac GTP-Binding Proteins / Q000378:metabolism
chemical_list: D011993:Recombinant Fusion Proteins; D051360:Cyclin-Dependent Kinase 5; C515905:Pak1 protein, mouse; C515906:Pak1 protein, rat; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; C495906:Cdk5 protein, mouse; C495907:Cdk5 protein, rat; D018844:Cyclin-Dependent Kinases; D020744:rac GTP-Binding Proteins