NLRX1 Regulates Effector and Metabolic Functions of CD4+ T Cells

Nucleotide oligomerization domain-like receptor X1 (NLRX1) has been implicated in viral response, cancer progression, and inflammatory disorders; however, its role as a dual modulator of CD4+ T cell function and metabolism has not been defined. The loss of NLRX1 results in increased disease severity, populations of Th1 and Th17 cells, and inflammatory markers (IFN-gamma, TNF-alpha, and IL-17) in mice with dextran sodium sulfate-induced colitis. To further characterize this phenotype, we used in vitro CD4+ T cell-differentiation assays and show that NLRX1-deficient T cells have a greater ability to differentiate into an inflammatory phenotype and possess greater proliferation rates. Further, NLRX1(-/-) cells have a decreased responsiveness to immune checkpoint pathways and greater rates of lactate dehydrogenase activity. When metabolic effects of the knockout are impaired, NLRX1-deficient cells do not display significant differences in differentiation or proliferation. To confirm the role of NLRX1 specifically in T cells, we used an adoptive-transfer model of colitis. Rag2(-/-) mice receiving NLRX1(-/-) naive or effector T cells experienced increased disease activity and effector T cell populations, whereas no differences were observed between groups receiving wildtype or NLRX1(-/-) regulatory T cells. Metabolic effects of NLRX1 deficiency are observed in a CD4-specific knockout of NLRX1 within a Citrobacter rodentium model of colitis. The aerobic glycolytic preference in NLRX1(-/-) effector T cells is combined with a decreased sensitivity to immunosuppressive checkpoint pathways to provide greater proliferative capabilities and an inflammatory phenotype bias leading to increased disease severity.