Abstract
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).
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Substitution / genetics
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Binding Sites / genetics
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Cell Movement / genetics
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Cell Movement / immunology*
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Cytoplasm / metabolism
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Cytoskeletal Proteins / metabolism*
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Cytoskeletal Proteins / physiology
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Enzyme Activation / genetics
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Focal Adhesion Kinase 1
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Focal Adhesion Kinase 2
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Focal Adhesion Protein-Tyrosine Kinases
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Humans
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Integrin alpha4 / genetics
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Integrin alpha4 / metabolism*
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Integrin alpha4 / physiology
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Integrin alpha4beta1 / antagonists & inhibitors
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Integrin alpha4beta1 / genetics
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Integrin alpha4beta1 / metabolism
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Integrin alpha4beta1 / physiology
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Jurkat Cells
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Lymphocyte Function-Associated Antigen-1 / metabolism
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Lymphocyte Function-Associated Antigen-1 / physiology*
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Paxillin
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Peptide Fragments / metabolism
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Peptide Fragments / physiology
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Phosphoproteins / metabolism*
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Phosphoproteins / physiology
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Protein Binding / genetics
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Protein Structure, Tertiary / genetics
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Protein Subunits / antagonists & inhibitors
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Protein Subunits / genetics
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Protein Subunits / metabolism
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Protein Subunits / physiology
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Protein-Tyrosine Kinases / antagonists & inhibitors
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Protein-Tyrosine Kinases / genetics
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Protein-Tyrosine Kinases / metabolism*
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Protein-Tyrosine Kinases / physiology
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Receptor Cross-Talk / physiology
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Signal Transduction / genetics
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Signal Transduction / immunology
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T-Lymphocytes / cytology*
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T-Lymphocytes / enzymology
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T-Lymphocytes / metabolism*
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Transfection
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Vascular Cell Adhesion Molecule-1 / metabolism
Substances
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Cytoskeletal Proteins
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Integrin alpha4beta1
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Lymphocyte Function-Associated Antigen-1
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PXN protein, human
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Paxillin
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Peptide Fragments
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Phosphoproteins
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Protein Subunits
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Vascular Cell Adhesion Molecule-1
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Integrin alpha4
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Protein-Tyrosine Kinases
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Focal Adhesion Kinase 1
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Focal Adhesion Kinase 2
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Focal Adhesion Protein-Tyrosine Kinases
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PTK2 protein, human