Regulation of Adhesion to ICAM-1 by the Cytoplasmic Domain of LFA-1 Integrin β Subunit

Interactions between cytotoxic lymphocytes and their targets require the T cell antigen receptor (TCR) and the integrin lymphocyte function-associated molecule-1 (LFA-1, CD11a/CD18). LFA-1 is not constitutively avid for its counter-receptors, intercellular adhesion molecules (ICAMs)-1 and -2. Cross-linking of the TCR transiently converts LFA-1 to a high avidity state and thus provides a mechanism for regulating cellular adhesion and de-adhesion in an antigen-specific manner. Truncation of the cytoplasmic domain of the beta, but not the alpha, subunit of LFA-1 eliminated binding to ICAM-1 and sensitivity to phorbol esters. Thus, LFA-1 binding to ICAM-1 was found to be regulated by the cytoplasmic domain of the beta subunit of LFA-1.