Tyrosine-phosphorylated T cell receptor zeta chain associates with the actin cytoskeleton upon activation of mature T lymphocytes.

The multichain T cell antigen receptor (TCR) is composed of an antigen binding (alpha/beta) domain and associated signal-transducing complexes, the CD3 (gamma, delta, and epsilon) and the zeta chains. The zeta chain (TCR zeta) plays a key role in signal transduction. We show here that TCR ligation induces association of tyrosine-phosphorylated TCR zeta with the detergent-insoluble cell fraction. The microfilament poison, cytochalasin D, disrupts this association and enhances the coprecipitation of actin with TCR zeta after receptor ligation. This microfilament association is specific to TCR-associated polypeptides containing at least one intact immunoreceptor tyrosine-based activation motif (ITAM). Mapping studies using transfectants and chimeric TCR zeta chain constructs suggest that the third ITAM is necessary and sufficient for association, if the distal tyrosine is intact. This cytoskeletal association is directly correlated with IL-2 production, and ligation of TCR on immature thymocytes does not induce TCR zeta-cytoskeleton association. These data thus provide direct evidence of a developmentally regulated activation-dependent interaction between a lymphocyte antigen receptor and the actin cytoskeleton.