Paxillin binding to the alpha 4 integrin subunit stimulates LFA-1 (integrin alpha L beta 2)-dependent T cell migration by augmenting the activation of focal adhesion kinase/proline-rich tyrosine kinase-2.
Engagement of very late Ag-4 (integrin alpha(4)beta(1)) by ligands such as VCAM-1 markedly stimulates leukocyte migration mediated by LFA-1 (integrin alpha(L)beta(2)). This form of integrin trans-regulation in T cells requires the binding of paxillin to the alpha(4) integrin cytoplasmic domain. This conclusion is based on the abolition of trans-regulation in Jurkat T cells by an alpha(4) mutation (alpha(4)(Y991A)) that disrupts paxillin binding. Furthermore, cellular expression of an alpha(4)-binding fragment of paxillin that blocks the alpha(4)-paxillin interaction, selectively blocked VCAM-1 stimulation of alpha(L)beta(2)-dependent cell migration. The alpha(4)-paxillin association mediates trans-regulation by enhancing the activation of tyrosine kinases, focal adhesion kinase (FAK) and/or proline-rich tyrosine kinase-2 (Pyk2), based on two lines of evidence. First, disruption of the paxillin-binding site in the alpha(4) tail resulted in much less alpha(4)beta(1)-mediated phosphorylation of Pyk2 and FAK. Second, transfection with cDNAs encoding C-terminal fragments of Pyk2 and FAK, which block the function of the intact kinases, blocked alpha(4)beta(1) stimulation of alpha(L)beta(2)-dependent migration. These results define a proximal protein-protein interaction of an integrin cytoplasmic domain required for trans-regulation between integrins, and establish that augmented activation of Pyk2 and/or FAK is an immediate signaling event required for the trans-regulation of integrin alpha(L)beta(2) by alpha(4)beta(1).
Rose
David M
DM
Division of Rheumatology, Allergy, and Immunology, Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA. drose@vapop.ucsd.edu
Liu
Shouchun
S
Woodside
Darren G
DG
Han
Jaewon
J
Schlaepfer
David D
DD
Ginsberg
Mark H
MH
D019943:Amino Acid Substitution / Q000235:genetics; D001665:Binding Sites / Q000235:genetics; D002465:Cell Movement / Q000235:genetics / Q000276:immunology*; D003593:Cytoplasm / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism* / Q000502:physiology; D004789:Enzyme Activation / Q000235:genetics; D051417:Focal Adhesion Kinase 1; D051418:Focal Adhesion Kinase 2; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D039441:Integrin alpha4 / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D039041:Integrin alpha4beta1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D019169:Jurkat Cells; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism / Q000502:physiology*; D051419:Paxillin; D010446:Peptide Fragments / Q000378:metabolism / Q000502:physiology; D010750:Phosphoproteins / Q000378:metabolism* / Q000502:physiology; D011485:Protein Binding / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D021122:Protein Subunits / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D020239:Receptor Cross-Talk / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology; D013601:T-Lymphocytes / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism*; D014162:Transfection; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism
D003598:Cytoskeletal Proteins; D039041:Integrin alpha4beta1; D016169:Lymphocyte Function-Associated Antigen-1; C496061:PXN protein, human; D051419:Paxillin; D010446:Peptide Fragments; D010750:Phosphoproteins; D021122:Protein Subunits; D019010:Vascular Cell Adhesion Molecule-1; D039441:Integrin alpha4; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051418:Focal Adhesion Kinase 2; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human