p38α regulates cytokine‐induced IFNγ secretion via the Mnk1/eIF4E pathway in Th1 cells

Abstract

The p38 mitogen-activated protein kinase (MAPK) pathway is involved in the regulation of immune and inflammatory processes. We used p38α-conditional, p38β-deficient and p38α/β double-null mouse models to address the role of these two p38 MAPK in CD4 T cells, and found that p38α deficiency causes these cells to hyperproliferate. Our studies indicate that both p38α and p38β are dispensable for T helper cell type 1 (Th1) differentiation but, by controlling interferon (IFN)γ and tumor necrosis factor (TNF)α production, are critical for normal Th1 effector function. We found that both p38α and p38β modulate T-cell receptor-induced IFNγ and TNFα production, whereas only p38α regulates cytokine-induced IFNγ production. The lack of p38α and p38β did not affect transcription and mRNA stability of Ifng. However, the absence of p38α in Th1 cells resulted in a decreased MNK1 phosphorylation after cytokine activation, and MNK1 inhibition blocked IFNγ production. Our results indicate that p38α regulates IFNγ secretion through the activation of the MNK1/eIF4E pathway of translation initiation and identify specific functions for p38α and p38β in T-cell proliferation.

Translational control in the tumor microenvironment promotes lung metastasis: Phosphorylation of eIF4E in neutrophils

“…The case of T cells is interesting, as our data do not preclude a role for phospho-eIF4E in these cells when relieved from neutrophil suppression in the eIF4E S209A setting. Translational regulation of various cytokines by T cells reported in other contexts (37,39), as well as data of Webster et al (40) using the MNK inhibitor eFT508, support this notion. In contrast, work with T cells lacking MNKs has indicated that these kinases, and eIF4E phosphorylation, are dispensable for normal T-cell function, but indirectly affect their differentiation and activity, using an in vivo model of autoimmune encephalomyelitis (37,41), mirroring our own findings in the TME.…”

“…Several cell types, in addition to neutrophils, may be playing important roles that we did not observe in our mouse model. Possibilities include macrophages, in which eIF4E phosphorylation has been linked to cytokine production (36,37); regulatory T cells, where eIF4E levels have been implicated (38); and IFN-γ production by Th1 cells, which has recently been linked to the p38-MNK-eIF4E axis (39). The case of T cells is interesting, as our data do not preclude a role for phospho-eIF4E in these cells when relieved from neutrophil suppression in the eIF4E S209A setting.…”

Translational Control in Cancer

“…The above-cited studies notwithstanding, little is known regarding translation regulatory events specific to the many different immune cell populations, particularly in the cancer-stroma context. eIF4E phos-phorylation appears to be important for the synthesis of cancer-relevant cytokines and chemokines, such as tumor necrosis factor α (TNF-α) and interferon γ (IFN-γ) (Andersson and Sundler 2006;Rowlett et al 2008;Herdy et al 2012;Salvador-Bernáldez et al 2017), and for the development of experimental autoimmune encephalomyelitis (Gorentla et al 2013). In neutrophils, eIF4E phosphorylation promotes survival and metastatic dissemination in a mouse model of breast cancer (Robichaud et al 2018).…”

Nitrogen starvation reveals the mitotic potential of mutants in the S/MAPK pathways

“…In human and mouse muscles, p38/Sty1 inhibition promotes the proliferation of quiescent satellite cells 46 . In activated lymphocytes, p38/Sty1 deficiency causes hyperproliferation, correlating with a decrease in eIF4E activity 47 . Thus, the S/MAPK mutants can successfully exit from the quiescent state at a lower threshold of environmental or physiological cues.…”