title: Cytoplasmic tails of beta 1, beta 2, and beta 7 integrins differentially regulate LFA-1 function in K562 cells.
abstract: The beta 2 integrin lymphocyte function-associated antigen 1 (LFA-1) mediates activation-dependent adhesion of lymphocytes. To investigate whether lymphocyte-specific elements are essential for LFA-1 function, we expressed LFA-1 in the erythroleukemic cell line K562, which expresses only the integrin very late antigen 5. We observed that LFA-1-expressing K562 cannot bind to intercellular adhesion molecule 1-coated surfaces when stimulated by phorbol 12-myristate 13-acetate (PMA), whereas the LFA-1-activating antibody KIM185 markedly enhanced adhesion. Because the endogenously expressed beta 1 integrin very late antigen 5 is readily activated by PMA, we investigated the role of the cytoplasmic domain of distinct beta subunits in regulating LFA-1 function. Transfection of chimeric LFA-1 receptors in K562 cells reveals that replacement of the beta 2 cytoplasmic tail with the beta 1 but not the beta 7 cytoplasmic tail completely restores PMA responsiveness of LFA-1, whereas a beta 2 cytoplasmic deletion mutant of LFA-1 is constitutively active. Both deletion of the beta 2 cytoplasmic tail or replacement by the beta 1 cytoplasmic tail alters the localization of LFA-1 into clusters, thereby regulating LFA-1 activation and LFA-1-mediated adhesion to intercellular adhesion molecule 1. These data demonstrate that distinct signaling routes activate beta 1 and beta 2 integrins through the beta-chain and hint at the involvement of lymphocyte-specific signal transduction elements in beta 2 and beta 7 integrin activation that are absent in the nonlymphocytic cell line K562.
authors.affiliation: Department of Tumor Immunology, University Hospital Nijmegen St. Radboud, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Lub
authors.forename: S J
authors.initials: SJ
authors.lastname: van Vliet
authors.forename: S P
authors.initials: SP
authors.lastname: Oomen
authors.forename: R A
authors.initials: RA
authors.lastname: Pieters
authors.forename: M
authors.initials: M
authors.lastname: Robinson
authors.forename: C G
authors.initials: CG
authors.lastname: Figdor
authors.forename: Y
authors.initials: Y
authors.lastname: van Kooyk
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D018821:CD18 Antigens / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D002448:Cell Adhesion / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism; D006801:Humans; D039641:Integrin beta Chains; D019012:Integrin beta1 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D016023:Integrins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D004915:Leukemia, Erythroblastic, Acute / Q000188:drug therapy / Q000378:metabolism*; D007942:Leukemia, Experimental; D016169:Lymphocyte Function-Associated Antigen-1 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D008214:Lymphocytes / Q000502:physiology; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D018821:CD18 Antigens; D005353:Fibronectins; D039641:Integrin beta Chains; D019012:Integrin beta1; D016023:Integrins; D016169:Lymphocyte Function-Associated Antigen-1; D011994:Recombinant Proteins; C091368:integrin beta7; D018799:Intercellular Adhesion Molecule-1; D013755:Tetradecanoylphorbol Acetate