Regulation of LFA-1 avidity in human B cells. Requirements for dephosphorylation events for high avidity ICAM-1 binding.
Regulation of the avidity of LFA-1 (CD11a/CD18, alpha L beta 2) for its ligand ICAM-1 (CD54) was studied in human B cells by evaluating the effects of a phorbol ester, anti-IgM antibodies, staurosporine, and okadaic acid. We monitored changes in LFA-1 avidity by quantifying binding of cells to an immobilized rICAM-1 fusion protein. In this assay, the protein kinase C-activating phorbol ester PDB and anti-IgM antibodies, as well as the protein kinase inhibitor, staurosporine, were able to induce LFA-1-dependent binding to ICAM-1. This demonstrates that the high avidity state of LFA-1 can be induced by a protein kinase C-dependent and by a protein kinase C-independent pathway. Furthermore, treatment of the cells with the protein phosphatase inhibitor, okadaic acid, inhibited binding to ICAM-1. Treatment with staurosporine before addition of okadaic acid not only induced enhanced binding of cells to ICAM-1, but also dramatically reduced the ability of okadaic acid to inhibit binding. These results suggest a critical role for a protein phosphatase in inducing the high avidity state of LFA-1 as well as a role for a protein kinase in inducing the low avidity state of LFA-1.
Hedman
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Unit for Applied Cell and Molecular Biology, University of Umeå, Sweden.
Lundgren
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D000470:Alkaloids / Q000494:pharmacology; D001402:B-Lymphocytes / Q000378:metabolism*; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002478:Cells, Cultured; D004988:Ethers, Cyclic / Q000494:pharmacology; D006801:Humans; D018799:Intercellular Adhesion Molecule-1; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism*; D019319:Okadaic Acid; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000502:physiology; D019311:Staurosporine
D000470:Alkaloids; D015815:Cell Adhesion Molecules; D004988:Ethers, Cyclic; D016169:Lymphocyte Function-Associated Antigen-1; D018799:Intercellular Adhesion Molecule-1; D019319:Okadaic Acid; D015240:Phorbol 12,13-Dibutyrate; D011493:Protein Kinase C; D019311:Staurosporine