A20 intrinsically influences human effector T‐cell survival and function by regulating both NF‐κB and JNK signaling

Abstract

A20 is a dual‐function ubiquitin‐editing enzyme that maintains immune homeostasis by restraining inflammation. Although A20 serves a similar negative feedback function for T‐cell receptor (TCR) signaling, the molecular mechanisms utilized and their ultimate impact on human T‐cell function remain unclear. TCR engagement triggers the assembly of the CARD11‐BCL10‐MALT1 (CBM) protein complex, a signaling platform that governs the activation of downstream transcription factors including NF‐κB and c‐Jun/AP‐1. Utilizing WT and A20 knockout Jurkat T cells, we found that A20 is required to negatively regulate NF‐κB and JNK. Utilizing a novel set of A20 mutants in NF‐κB and AP‐1‐driven reporter systems, we discovered the ZnF7 domain is crucial for negative regulatory capacity, while deubiquitinase activity is dispensable. Successful inactivation of A20 in human primary effector T cells congruently conferred sustained NF‐κB and JNK signaling, including enhanced upregulation of activation markers, and increased secretion of several cytokines including IL‐9. Finally, loss of A20 in primary human T cells resulted in decreased sensitivity to restimulation‐induced cell death and increased sensitivity to cytokine withdrawal‐induced death. These findings demonstrate the importance of A20 in maintaining T‐cell homeostasis via negative regulation of both NF‐κB and JNK signaling.