Dynamic actin polymerization drives T cell receptor-induced spreading: A role for the signal transduction adaptor LAT

T cell activation induces functional changes in cell shape and cytoskeletal architecture. To facilitate the collection of dynamic, high-resolution ima ges of activated T cells, we plated T cells on coverslips coated with antib odies to the T cell receptor (TCR). Using these images, we were able to qua ntitate the morphological responses of individual cells over time. Here, we show that TCR engagement triggers the formation and expansion of contacts bounded by continuously remodeled actin-rich rings, These processes are ass ociated with the extension of lamellipodia and require actin polymerization , tyrosine kinase activation, cytoplasmic calcium increases, and LAT, an im portant hematopoietic adaptor. In addition, the maintenance of the resultin g contact requires sustained calcium influxes, an intact microtubule cytosk eleton, and functional LAT.