T cell receptor (TCR) signalling has been an area of intense study for many years. New proteins are being continually discovered each year, making the task of understanding the various pathways evermore challenging. Depicted here are only some of the many TCR-responsive proteins and the mechanisms by which they lead to production of the cytokine interleukin 2 (IL-2).
Upon engagement of the TCR by antigen presented on major histocompatibility complex (MHC) molecules, the Src family kinase Lck is activated and proceeds to phosphorylate immunoreceptor tyrosine-based activation motifs (ITAMs) on the ε, δ, γ and ζ subunits of the TCR. Phosphorylated ITAMs promote the recruitment and subsequent activation of another tyrosine kinase ZAP-70. Two known substrates of ZAP-70 are the adapter molecules LAT and SLP-76. Phosphorylation of tyrosine residues on LAT and SLP-76 results in recruitment of a number of other proteins involved in activation of the Ras pathway, calcium mobilization...
