Active Translation Control of CD4 T Cell Activation by Regulatory T Cells

Increased protein synthesis is a hallmark of lymphocyte activation. Regulatory T cells (Tregs) suppress the activation and subsequent effector functions of CD4 effector T cells (Teff). Molecular mechanisms that enforce suppression on CD4 Teff cell function are unclear. Control of CD4 Teff cell activation by Tregs has largely been defined at the transcriptional level, which does not reflect changes in post-transcriptional control. We found that Tregs suppressed activation-induced global protein synthesis in CD4 Teff cells prior to cell division. We analyzed genome-wide changes in the transcriptome and translatome of activated CD4 Teff cells using two independent approaches. We show that mRNAs encoding for the protein synthesis machinery are regulated at the level of translation in activated Teff cells. Strikingly, Tregs suppressed global protein synthesis of CD4 Teff cells by specifically inhibiting mRNAs of the translation machinery at the level of mTORC1-mediated translation control. Lastly, we found that the RNA helicase eIF4A inhibitor rocaglamide A (RocA) can suppress CD4 Teff activation in vitro to alleviate inflammatory CD4 Teff activation caused by acute Treg depletion in vivo . These data provide evidence that peripheral tolerance is enforced by Tregs, mediated by IL-10, through mRNA translational control in CD4 Teff cells. Therefore, therapeutic targeting of the protein synthesis machinery can mitigate inflammatory responses invoked by Treg loss of function. ### Competing Interest Statement The authors have declared no competing interest.