The timing of differentiation and potency of CD8 effector function is set by RNA binding proteins

Abstract

CD8+ T cell differentiation into effector cells is initiated early after antigen encounter by signals from the T cell antigen receptor and costimulatory molecules. The molecular mechanisms that establish the timing and rate of differentiation however are not defined. Here we show that the RNA binding proteins (RBP) ZFP36 and ZFP36L1 limit the rate of differentiation of activated naïve CD8+ T cells and the potency of the resulting cytotoxic lymphocytes. The RBP function in an early and short temporal window to enforce dependency on costimulation via CD28 for full T cell activation and effector differentiation by directly binding mRNA of NF-κB, Irf8 and Notch1 transcription factors and cytokines, including Il2. Their absence in T cells, or the adoptive transfer of small numbers of CD8+ T cells lacking the RBP, promotes resilience to influenza A virus infection without immunopathology. These findings highlight ZFP36 and ZFP36L1 as nodes for the integration of the early T cell activation signals controlling the speed and quality of the CD8+ T cell response.

Multiomics analysis couples mRNA turnover and translational control of glutamine metabolism to the differentiation of the activated CD4+ T cell

“…For Tnf , this is consistent with data from CD4 + T cells in a single KO of Zfp36 , whilst in that context, Il2 expression was not increased 46 . The results for Il2 in CD4 + T cells are also in contrast to CD8 + T cells early following activation, in which a substantial increase in mRNA abundance within dKO cells was driven by increased transcript stability 51 . Furthermore, the same transcript, e.g., Tnf , can be regulated in distinct ways depending on the cellular context, as highlighted by Kovarik 81 .…”

“…S1 b). To establish whether the redundancy between ZFP36 and ZFP36L1 observed in CD8 + T cells 51 was also apparent in CD4 + T cells, we first performed RNA-seq to measure mRNA abundance in the dKO compared with control, and analysed this data together with RNA-seq from single KO models ( Zfp36 fl/fl Cd4 cre and Zfp36l1 fl/fl Cd2 cre , each compared with corresponding floxed controls). Whilst the Zfp36l1 single KO utilises CD2- rather than CD4-Cre, we expect this to have minimal impact on our results, since in both cases deletion occurs during thymic development, and should be complete within the isolated population of naïve CD4 + T cells.…”

“…7 g). Given our previous identification of transcription factors regulated by the ZFP36 family during CD8 + T cell differentiation 51 , we also examined these transcripts in CD4 + T cells. Both Notch1 and Irf8 showed increased mRNA abundance and translation, accompanied by ZFP36-family binding in their 3’UTR, whilst Nfkb2 was bound and increased in stability and translation of its mRNA (Fig.…”

“…Their data suggested that ZFP36 negatively regulates both mRNA abundance and translation of its target genes, and additionally identified genes involved in activation, proliferation and effector function as direct ZFP36 targets 46 . Although these studies show roles for Zfp36 in T cell activation, the contribution of the other paralogs is mostly unknown, and some roles of the ZFP36 family may have been masked by redundancy between ZFP36 and ZFP36L1 51 . Roles for the ZFP36 family in the metabolism of immune cells have not yet been identified.…”

Divide and Conquer: Phenotypic and Temporal Heterogeneity Within CD8+ T Cell Responses

“…Finally, as alluded to in multiple sections above, cytokine and costimulatory signals can feed into and amplify signaling networks initiated by the TCR, effectively enhancing the strength of stimulation a T cell experiences. Indeed, naïve cells are programmed to rely on these additional signals, as recently demonstrated by a study in which deletion of the RNA binding proteins ZFP36 and ZFP36L1 reduced dependence on CD28 signaling during early activation and enhanced effector differentiation (115). Investigations of signaling nodes responsible for conveying cytokine and costimulatory signals into the TCR activation network have identified elements of metabolic programming pathways, including PI3K/AKT and MYC (57,60,64,(116)(117)(118)(119), consistent with extensive work showing that CD28 costimulation and IL2 signaling promote glycolytic metabolism (120).…”