pp125FAK-dependent tyrosine phosphorylation of paxillin creates a high-affinity binding site for Crk.
Paxillin, a focal-adhesion-associated protein, becomes phosphorylated in response to a number of stimuli which also induce the tyrosine phosphorylation of the focal-adhesion-associated protein tyrosine kinase pp125FAK. On the basis of their colocalization and coordinate phosphorylation, paxillin is a candidate for a substrate of pp125FAK. We describe here conditions under which the phosphorylation of paxillin on tyrosine is pp125FAK dependent, supporting the hypothesis that paxillin phosphorylation is regulated by pp125FAK. pp125FAK must localize to focal adhesions and become autophosphorylated to induce paxillin phosphorylation. Phosphorylation of paxillin on tyrosine creates binding sites for the SH2 domains of Crk, Csk, and Src. We identify two sites of phosphorylation as tyrosine residues 31 and 118, each of which conforms to the Crk SH2 domain binding motif, (P)YXXP. These observations suggest that paxillin serves as an adapter protein, similar to insulin receptor substrate 1, and that pp125FAK may regulate the formation of signaling complexes by directing the phosphorylation of paxillin on tyrosine.
Schaller
M D
MD
Department of Microbiology, University of Virginia, Charlottesville 22908, USA.
Parsons
J T
JT
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D015815:Cell Adhesion Molecules / Q000737:chemistry / Q000378:metabolism*; D002642:Chick Embryo; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D008958:Models, Molecular; D008969:Molecular Sequence Data; D050736:Oncogene Protein v-crk; D051419:Paxillin; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000737:chemistry / Q000378:metabolism; D015682:Retroviridae Proteins, Oncogenic / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity; D014443:Tyrosine / Q000378:metabolism
D015815:Cell Adhesion Molecules; D003598:Cytoskeletal Proteins; D050736:Oncogene Protein v-crk; D051419:Paxillin; D010455:Peptides; D010750:Phosphoproteins; D015682:Retroviridae Proteins, Oncogenic; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D016392:Proto-Oncogene Proteins pp60(c-src)