Cell-surface-expressed T-cell antigen-receptor ζ chain is associated with the cytoskeleton

The T-cell antigen receptor ζ chain plays an important role in coupling antigen recognition to several intracellular signal-transduction pathways. ζ chain can associate with certain protein tyrosine kinases and retains the capacity to transduce signals independently of the other receptor subunits. Thus, ζ chain could couple cell-surface-expressed T-cell antigen receptors to the intracellular signal-transduction apparatus by its association with various intracellular molecules in addition to tyrosine kinases. In the process of searching for ζ chain-associated molecules we observed that after lysis of resting T cells with Triton X-100, ζ chain is localized in the detergent-insoluble fraction, in addition to its presence in the detergent- soluble fraction. Treatment of T cells with cytochalasin B, an actin- depolymerizing agent, leads to the complete dissociation of ζ chain from the Triton-insoluble fraction, suggesting a linkage between ζ chain and the cytoskeletal matrix. We have also determined that cytoskeletal-associated ζ chain is expressed on the cell surface. Furthermore, a tyrosine- phosphorylated 16-kDa ζ chain was detected only in the Triton-insoluble cytoskeletal fraction of resting T cells. ζ chain also maintains its association with the cytoskeleton when expressed in COS cells, inferring that the cytoskeletal elements involved in this linkage may be ubiquitous. Finally, we have localized a 42-amino acid region in the intracytoplasmic domain of ζ chain, which is crucial for maximal interaction between chain and the cytoskeleton. Anchorage of cell-surface-expressed ζ chain to the cytoskeleton in resting T cells may facilitate recycling of receptor complexes and/or allow the transduction of external stimuli into the cell.