Quantitative interactomics in primary T cells unveils TCR signal diversification extent and dynamics

Overview & Synopsis

he activation of T cells by the T cell antigen receptor (TCR) results in the formation of signaling protein complexes (signalo­somes), the composition of which has not been analyzed at a systems level. Here, we isolated primary CD4+ T cells from 15 gene­targeted mice, each expressing one tagged form of a canonical protein of the TCR­signaling pathway. Using affinity puri­fication coupled with mass spectrometry, we analyzed the composition and dynamics of the signalosomes assembling around each of the tagged proteins over 600 s of TCR engagement. We showed that the TCR signal­transduction network comprises at least 277 unique proteins involved in 366 high­confidence interactions, and that TCR signals diversify extensively at the level of the plasma membrane. Integrating the cellular abundance of the interacting proteins and their interaction stoichiometry provided a quantitative and contextual view of each documented interaction, permitting anticipation of whether ablation of a single interacting protein can impinge on the whole TCR signal-transduction network.