The Critical Cytoplasmic Regions of the αL/β2 Integrin in Rap1-induced Adhesion and Migration

• DOI: 10.1091/mbc.e02-09-0615
• Publication Date: 2003-03-11T02:38:53Z
• Authors: Yumi Tohyama; Koko Katagiri; Ruggero Pardi; Chafen Lu; Timothy A. Springer; Tatsuo Kinashi
• Keywords: Mice; 0303 health sciences; 03 medical and health sciences; Cell Movement; Mutation; Cell Adhesion; Animals; Humans; rap1 GTP-Binding Proteins; Lymphocyte Function-Associated Antigen-1; Protein Structure, Tertiary

Rap1 is a potent inside-out signal that increases LFA-1 adhesive activity. In this study, we have defined the cytoplasmic region of the αL and β2 integrin that are required for Rap1-stimulated adhesion and subsequent migration on ICAM-1. Human LFA-1 bearing truncated and point-mutated αL and β2 cytoplasmic regions were reconstituted in mouse IL-3-dependent proB cells, BAF/3. Truncation of the αL, but not β2 subunit cytoplasmic region, abolished Rap1V12-dependent adhesion to ICAM-1. The alanine substitution of two lysine residues (K1097/K1099) in the αL 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 β2 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.