title: PAK4 mediates morphological changes through the regulation of GEF-H1.
abstract: Precise spatial and temporal regulation of Rho GTPases is required in controlling F-actin-based changes in cell morphology. The molecular mechanisms through which microtubules (MTs) modulate the activity of RhoGTPases and regulate the actin cytoskeleton are unclear. Here we show that p21-activated-kinase 4 (PAK4) mediates morphological changes through its association with the Rho-family guanine nucleotide exchange factor (GEF), GEF-H1. We show that this association is dependent upon a novel GEF-H1 interaction domain (GID) within PAK4. Further, we show that PAK4-mediated phosphorylation of Ser810 acts as a switch to block GEF-H1-dependent stress fiber formation while promoting the formation of lamellipodia in NIH-3T3 cells. We found that the endogenous PAK4-GEF-H1 complex associates with MTs and that PAK4 phosphorylation of MT-bound GEF-H1 releases it into the cytoplasm of NIH-3T3 cells, which coincides with the dissolution of stress fibers. Our observations propose a novel role for PAK4 in GEF-H1-dependent crosstalk between MTs and the actin cytoskeleton.
authors.affiliation: SUGEN Incorporated, 230 East Grand Avenue, South San Francisco, CA 94080, USA.
authors.forename: Marinella G
authors.initials: MG
authors.lastname: Callow
authors.forename: Sergey
authors.initials: S
authors.lastname: Zozulya
authors.forename: Mikhail L
authors.initials: ML
authors.lastname: Gishizky
authors.forename: Bahija
authors.initials: B
authors.lastname: Jallal
authors.forename: Tod
authors.initials: T
authors.lastname: Smeal
mesh_terms: D000199:Actins / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D019921:Biotinylation; D002460:Cell Line; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000378:metabolism; D005786:Gene Expression Regulation; D005822:Genetic Vectors; D005982:Glutathione Transferase / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D051379:Mice; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000378:metabolism; D008954:Models, Biological; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D041681:NIH 3T3 Cells; D010455:Peptides / Q000737:chemistry; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D017434:Protein Structure, Tertiary; D064067:Rho Guanine Nucleotide Exchange Factors; D012694:Serine / Q000737:chemistry; D013379:Substrate Specificity; D013997:Time Factors; D014162:Transfection; D054462:p21-Activated Kinases; D020744:rac GTP-Binding Proteins / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000378:metabolism
chemical_list: C577356:ARHGEF2 protein, human; D000199:Actins; D020662:Guanine Nucleotide Exchange Factors; D010455:Peptides; D064067:Rho Guanine Nucleotide Exchange Factors; D012694:Serine; D004247:DNA; D005982:Glutathione Transferase; C116367:PAK4 protein, human; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D020558:GTP Phosphohydrolases; D020744:rac GTP-Binding Proteins; D020741:rho GTP-Binding Proteins