Quantitative Proteomics Reveals a Unique Wiring of Signaling Pathways that Protects Human Regulatory T Cell Identity

Regulatory CD4+ T cells (Tregs) are functionally distinct from conventional CD4+ T cells (Tconvs). To understand Treg identity, we have compared by proteomics and transcriptomics human naïve (n) and effector (e)Tregs, Tconvs and transitional FOXP3+ cells. Among these CD4+ T cell subsets, we detected differential expression of 421 proteins and 640 mRNAs, with only 48 molecules shared. Fifty proteins discriminated Tregs from Tconvs. This common Treg protein signature indicates altered signaling by TCR-, TNF receptor-, NFkB-, PI3 kinase/mTOR-, NFAT- and STAT pathways and unique cell biological and metabolic features. Another protein signature uniquely identified eTregs and revealed active cell division, apoptosis sensitivity and suppression of NFkB- and STAT signaling. eTreg fate appears consolidated by FOXP3 outnumbering its partner transcription factors. These features explain why eTregs cannot produce inflammatory cytokines, while transitional FOXP3+ cells can. Our collective data reveal that Tregs protect their identity by a unique “wiring” of signalling pathways Overall design: mRNA profiles of 5 CD4+ T cell populations were generated by deep sequencing, in triplicate

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Cuadrado E, van den Biggelaar M, de Kivit S, Chen YY, Slot M, Doubal I, Meijer A, van Lier RAW, Borst J, Amsen D