International Conference on Immunology and Immunotechnology
November 1-3, 2017 Barcelona, Spain
TCR Cross linking Promotes Crk Adaptor Protein Binding to Tyrosine-Phosphorylated CD3ζ Chain
Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences and the Cancer Research Center, Ben Gurion University of the Negev, Israel
Tcell antigen receptor (TCR) binding of a peptide antigen presented by antigen-presenting cells (APCs) in the context of surface MHC molecules initiates signaling events that regulate T cell activation, proliferation and differentiation. A key event in the activation process is the phosphorylation of the conserved tyrosine residues within the CD3 chain immune receptor tyrosine-based activation motifs (ITAMs), which operate as docking sites for SH2 domain-containing effecter proteins. Phosphorylation of the CD3ζ ITAMs renders the CD3 chain capable of binding the ζ-chain associated protein 70 kDa (ZAP70), a protein tyrosine kinase that is essential for T cell activation.
We found that TCR/CD3 cross linking in Jurkat T cells promotes the association of Crk adaptor proteins with the transiently phosphorylated CD3ζ chain. Pull down assays using bead-immobilized GST fusion proteins revealed that the Crk-SH2 domain mediates binding of phospho-CD3ζ. Phospho-CD3ζ binding is selective and is mediated by the three types of Crk, including CrkI, CrkII, and CrkL, but not by other SH2 domain-containing adaptor proteins, such as Grb2, GRAP and Nck.
Crk interaction with phospho-CD3ζ is rapid and transient, peaking one minute post TCR/CD3 cross linking. The results suggest the involvement of Crk adaptor proteins in the early stages of T cell activation in which Crk might help recruiting effector proteins to the vicinity of the phospho-CD3ζ and contribute to the fine-tuning of the TCR/CD3-coupled signal transduction pathways.