Src and FAK kinases cooperate to phosphorylate paxillin kinase linker, stimulate its focal adhesion localization, and regulate cell spreading and protrusiveness.
The ArfGAP paxillin kinase linker (PKL)/G protein-coupled receptor kinase-interacting protein (GIT)2 has been implicated in regulating cell spreading and motility through its transient recruitment of the p21-activated kinase (PAK) to focal adhesions. The Nck-PAK-PIX-PKL protein complex is recruited to focal adhesions by paxillin upon integrin engagement and Rac activation. In this report, we identify tyrosine-phosphorylated PKL as a protein that associates with the SH3-SH2 adaptor Nck, in a Src-dependent manner, after cell adhesion to fibronectin. Both cell adhesion and Rac activation stimulated PKL tyrosine phosphorylation. PKL is phosphorylated on tyrosine residues 286/392/592 by Src and/or FAK and these sites are required for PKL localization to focal adhesions and for paxillin binding. The absence of either FAK or Src-family kinases prevents PKL phosphorylation and suppresses localization of PKL but not GIT1 to focal adhesions after Rac activation. Expression of an activated FAK mutant in the absence of Src-family kinases partially restores PKL localization, suggesting that Src activation of FAK is required for PKL phosphorylation and localization. Overexpression of the nonphosphorylated GFP-PKL Triple YF mutant stimulates cell spreading and protrusiveness, similar to overexpression of a paxillin mutant that does not bind PKL, suggesting that failure to recruit PKL to focal adhesions interferes with normal cell spreading and motility.
Department of Cell and Developmental Biology, College of Medicine, State University of New York Upstate Medical University, Syracuse, NY 13210, USA.
Michael C
MC
Brown
Leslie A
LA
Cary
Jennifer S
JS
Jamieson
Jonathan A
JA
Cooper
Christopher E
CE
Turner
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002460:Cell Line; D002465:Cell Movement / Q000502:physiology*; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000502:physiology*; D022001:Focal Adhesions / Q000201:enzymology* / Q000378:metabolism; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D017930:Genes, Reporter; D036341:Intercellular Signaling Peptides and Proteins; D051379:Mice; D015513:Oncogene Proteins / Q000378:metabolism; D051419:Paxillin / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship; D014443:Tyrosine / Q000378:metabolism; D019061:src-Family Kinases / Q000235:genetics / Q000502:physiology*
D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; D020690:GTPase-Activating Proteins; C120767:Git2 protein, mouse; D036341:Intercellular Signaling Peptides and Proteins; C078332:Nck protein; D015513:Oncogene Proteins; D051419:Paxillin; D010750:Phosphoproteins; C496062:Pxn protein, mouse; D011993:Recombinant Fusion Proteins; D014443:Tyrosine; D051416:Focal Adhesion Protein-Tyrosine Kinases; D019061:src-Family Kinases