title: Phosphorylation of the LFA-1 integrin beta2-chain on Thr-758 leads to adhesion, Rac-1/Cdc42 activation, and stimulation of CD69 expression in human T cells.
abstract: Phosphorylation of the leukocyte function-associated antigen-1 (LFA-1) integrin beta2-chain on Thr-758 occurs after T cell receptor stimulation and leads to 14-3-3 recruitment to the integrin, actin cytoskeleton reorganization, and increased adhesion. Here, we have investigated the signaling effects of beta2 integrin Thr-758 phosphorylation. A penetratin-coupled phospho-Thr-758-beta2 peptide (mimicking the part of the integrin beta-chain surrounding Thr-758) stimulated adhesion of human T cells to the LFA-1 ligand intercellular adhesion molecule-1 (ICAM-1). Additionally, the peptide activated the small GTPases Rac-1 and Cdc42 in T cells. Constitutively active forms of Rac-1 and Cdc42, but not Rho, could compensate for the reduction of cell adhesion to ICAM-1 caused by the T758A mutation in the beta2 integrin. Additionally, the active GTPases salvaged the cell-spreading defect of T758A integrin-transfected cells on coated ICAM-1. A dominant negative form of Cdc42, on the other hand, significantly reduced wild-type beta2 integrin-mediated cell adhesion and spreading. In a T cell stimulation system, the pThr-758 penetratin peptide acted in a similar manner to coated ICAM-1 to increase T cell receptor-induced CD69 expression. These results show that Thr-758-phosphorylated LFA-1 is upstream of Rac-1/Cdc42, cell adhesion, and costimulatory activation of human T cells, thus identifying phosphorylation of Thr-758 in beta2 as a proximal element in LFA-1 signaling.
authors.affiliation: Division of Biochemistry, Faculty of Biosciences, University of Helsinki, 00014 Helsinki, Finland.
authors.forename: Susanna M
authors.initials: SM
authors.lastname: Nurmi
authors.forename: Matti
authors.initials: M
authors.lastname: Autero
authors.forename: Anna K
authors.initials: AK
authors.lastname: Raunio
authors.forename: Carl G
authors.initials: CG
authors.lastname: Gahmberg
authors.forename: Susanna C
authors.initials: SC
authors.lastname: Fagerholm
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D015703:Antigens, CD / Q000378:metabolism*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000378:metabolism*; D019556:COS Cells; D002352:Carrier Proteins / Q000378:metabolism; D002448:Cell Adhesion / Q000276:immunology; D057846:Cell-Penetrating Peptides; D002522:Chlorocebus aethiops; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D037181:Lectins, C-Type; D008213:Lymphocyte Activation / Q000502:physiology; D016169:Lymphocyte Function-Associated Antigen-1 / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011948:Receptors, Antigen, T-Cell / Q000276:immunology / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology; D013601:T-Lymphocytes / Q000166:cytology / Q000378:metabolism*; D013912:Threonine / Q000378:metabolism; D014162:Transfection; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D000099192:CD69 Antigens
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D002352:Carrier Proteins; D057846:Cell-Penetrating Peptides; D018799:Intercellular Adhesion Molecule-1; D037181:Lectins, C-Type; D016169:Lymphocyte Function-Associated Antigen-1; D011948:Receptors, Antigen, T-Cell; D013912:Threonine; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; D000099192:CD69 Antigens; C107953:RAC1 protein, human; C414409:penetratin