title: The critical cytoplasmic regions of the alphaL/beta2 integrin in Rap1-induced adhesion and migration.
abstract: Rap1 is a potent inside-out signal that increases LFA-1 adhesive activity. In this study, we have defined the cytoplasmic region of the alphaL and beta2 integrin that are required for Rap1-stimulated adhesion and subsequent migration on ICAM-1. Human LFA-1 bearing truncated and point-mutated alphaL and beta2 cytoplasmic regions were reconstituted in mouse IL-3-dependent proB cells, BAF/3. Truncation of the alphaL, but not beta2 subunit cytoplasmic region, abolished Rap1V12-dependent adhesion to ICAM-1. The alanine substitution of two lysine residues (K1097/K1099) in the alphaL subunit was found to be critical in adhesion induced by Rap1V12, but not PMA. This mutation suppressed Rap1V12-induced LFA-1 conformation changes and ligand-binding affinity. The K1097/K1099 mutation also impaired binding to ICAM-1 induced by TCR cross-linking or SDF-1. In contrast, the alanine substitution for tyrosine in the beta2 subunit endocytosis motif inhibited internalization of LFA-1, and severely impaired detachment at the cell rear, which resulted in long-elongated cell shapes. This result demonstrates that internalization of LFA-1 is a critical step in the deadhesion process. Our study revealed novel requirements of amino acid residues of the LFA-1 cytoplasmic region in the response to the inside-out signaling and the subsequent deadhesion process.
authors.affiliation: Department of Molecular Immunology and Allergy, Graduate School of Medicine, Kyoto University, Japan.
authors.forename: Yumi
authors.initials: Y
authors.lastname: Tohyama
authors.forename: Koko
authors.initials: K
authors.lastname: Katagiri
authors.forename: Ruggero
authors.initials: R
authors.lastname: Pardi
authors.forename: Chafen
authors.initials: C
authors.lastname: Lu
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Springer
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Kinashi
mesh_terms: D000818:Animals; D002448:Cell Adhesion / Q000502:physiology; D002465:Cell Movement / Q000502:physiology*; D006801:Humans; D016169:Lymphocyte Function-Associated Antigen-1 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009154:Mutation; D017434:Protein Structure, Tertiary; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D016169:Lymphocyte Function-Associated Antigen-1; D020827:rap1 GTP-Binding Proteins