CROSS-LINKING OF ICAM-1 ON T-CELLS INDUCES TRANSIENT TYROSINE PHOSPHORYLATION AND INACTIVATION OF CDC2 KINASE

Intercellular adhesion molecules (ICAM)-1 and -3 co-exist on T lymphoc ytes and are counter-receptors for the integrin LFA-1. Signaling throu gh ICAM-3 stimulates a number of T cell functions and involves phospho rylation of Fyn, Lck, CD45, and other proteins, In contrast, this type of specific signaling event has not been described for signaling thro ugh ICAM-1, Here, tyrosine phosphorylation of cellular proteins was ex amined after cross-linking of ICAM-1. Tyrosine phosphorylation of the 34-kDa cdc2 protein kinase was induced transiently after stimulation o f the leukemic T cell line, Molt-3, or peripheral blood T cells, Stimu lation through ICAM-1 had no effect on constitutive presence of cdc2 o r phosphorylation of cdc2 on threonine, cdc2 kinase activity was const itutive in peripheral blood T cells, and transient inhibition of kinas e activity after ICAM-1 stimulation correlated kinetically with phosph orylation of cdc2 on tyrosine.