Abstact

As the antigen receptor, the T cell receptor (TCR)-CD3 complex contains a panel of immunoreceptor tyrosine-based activation motifs (ITAMs) in the CD3 subunits to transduce diverse antigen signals, but the mechanism underlying TCR signaling versatility remains poorly understood. Here, we unraveled the structural and functional heterogeneity of the major CD3ζ signaling component. Using nuclear magnetic resonance spectroscopy, we characterized the membrane-bound structure of the dynamic CD3ζ cytoplasmic domain. ITAM 1 to 3 displayed a gradual increase of membrane insertion, leading to a sequential phosphorylation order from N to C terminus and the generation of partial- and full-phosphorylation species upon physiological triggering. Under chronic TCR stimulation, a scenario relevant to cancer and chronic infection, the C-terminal ITAM displayed faster decay kinetics of phosphorylation than the N-terminal one, causing insufficient TCR signaling. Our study thus reveals a new mechanism of ITAM heterogeneity in TCR signaling that is relevant to physiological and pathological contexts.