Calcium signaling through the beta(2)-cytoplasmic domain of LFA-1 requiresintracellular elements of the T cell receptor complex

The beta (2) integrin LFA-1 is an important cell-cell adhesion receptor of the immune system. Evidence suggests that the molecule also participates in signaling and costimulatory function. We show here that clustering of the intracellular domain of the beta (2) chain but not of the alpha (L)- or bet a (1)-cytoplasmic domains, respectively, triggers intracellular Ca2+ mobili zation in Jurkat cells. A beta (2)-specific NPXF motif, located in the C-te rminal portion of the beta (2) tail, is required for Ca2+ signaling, and we show that this motif is important for the induction of allospecific target cell lysis by cytotoxic T cells in vitro. Significantly, the Ca2+-signalin g capacity of the beta (2) integrin is abrogated in T cells that do not exp ress the T cell receptor but may be reconstituted by co-expression of the T cell receptor-zeta chain. Our data suggest a specific function of the cyto plasmic domain of the beta (2) integrin chain in T cell signaling.