Acidity perturbs IL-2 responsiveness, mTORC1 and c-Myc in CD8+ T cells

CD8+T cells play a critical role in tumor control but a range of barriers in the microenvironment including low pH can suppress their function.Here, we demonstrate that acidity dampens T-cell expansion mainly due to impaired IL-2 responsiveness, blunts cytokine secretion upon re-activation, and lowers the cytolytic capacity ofCD8+T cells expressing weak affinity TCR. We further reveal decreases in both mTORC1 signaling and c-Myc levels at low pH.Mechanistically, concomitantly to nuclear/cytoplasmic acidification, mTORC1 was disrupted in a Rheb-, Akt/TSC2/PRAS40-, GATOR1- and Lkb1/AMPK -independent manner, and c-Myc levels dropped due to both decreased transcription and higher proteasome-mediated degradation. In addition, lower intracellular levels of glutamine/glutamate/aspartate and elevated proline were observed with no apparent impact on mTORC1 or c-Myc. Overall, we conclude that, due to the broad disruption caused by acidity, multiple interventions will be required to restore T-cell function unless intracellular pH can be effectively restored. To investigate the impact of low pH on the CTL transcriptome, OT-I CTLs from 5 biological replicates were cultured at pH7.4, pH7 or pH6.6 in the presence, or absence, of 200IU/mL mIL-2 for 24 hours.