title: Paxillin enables attachment-independent tyrosine phosphorylation of focal adhesion kinase and transformation by RAS.
abstract: Paxillin and HIC5 are closely related adapter proteins that regulate cell migration and are tyrosine-phosphorylated by focal adhesion kinase (FAK). Paxillin, HIC5, and FAK tyrosine phosphorylation increase upon cell attachment and decrease upon detachment from extracellular matrix. Unexpectedly, we found that although FAK tyrosine phosphorylation in attached cells did not require paxillin, in detached fibroblasts there was remaining FAK tyrosine phosphorylation that required expression of paxillin and was not supported by HIC5. The support of attachment-independent FAK tyrosine phosphorylation required the paxillin LIM domains and suggested that paxillin might facilitate oncogenic transformation. Paxillin but not HIC5 augmented anchorage-independent cell proliferation induced by RAS. Both anchorage-independent FAK tyrosine phosphorylation and RAS-induced colony formation required multiple docking sites on paxillin, including LD4 (docking sites for FAK-Src and GIT1/2-PIX-NCK-PAK complex), LD5, and all four carboxyl-terminal LIM domains (that bind tubulin and PTP-PEST). Analysis using paxillin mutants dissociated domains of paxillin that are required for regulation of cell migration from domains that are required for anchorage-independent cell proliferation and demonstrated essential functions of the paxillin LIM domains that are not found in HIC5 LIM domains. These results highlight the role of paxillin in facilitating attachment-independent signal transduction implicated in cancer.
authors: Department of Pathology, University of Virginia, Charlottesville, Virginia 22908.
authors: Ramon
authors: R
authors: Wade
authors: Department of Pathology, University of Virginia, Charlottesville, Virginia 22908.
authors: Nicole
authors: N
authors: Brimer
authors: Department of Pathology, University of Virginia, Charlottesville, Virginia 22908.
authors: Charles
authors: C
authors: Lyons
authors: Department of Pathology, University of Virginia, Charlottesville, Virginia 22908. Electronic address: vandepol@virginia.edu.
authors: Scott Vande
authors: SV
authors: Pol
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D002448:Cell Adhesion; D049109:Cell Proliferation; D003598:Cytoskeletal Proteins / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation; D005347:Fibroblasts / Q000166:cytology; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D060588:LIM Domain Proteins / Q000378:metabolism; D051379:Mice; D009154:Mutation; D051419:Paxillin / Q000378:metabolism*; D010766:Phosphorylation; D015398:Signal Transduction; D014443:Tyrosine / Q000737:chemistry; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D000199:Actins; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D060588:LIM Domain Proteins; D051419:Paxillin; C490351:TGFB1I1 protein, human; C090090:Tgfb1i1 protein, mouse; D014443:Tyrosine; D051416:Focal Adhesion Protein-Tyrosine Kinases; D018631:ras Proteins