Mitochondrial Metabolism is Essential for Invariant Natural Killer T Cell Development and Function

Conventional T cell fate and function are determined by coordination between cellular signaling and metabolism. Invariant natural killer T (iNKT) cells are a subset of “innate-like” pre-activated T cells whose dependence on mitochondrial metabolism remains elusive. Here, we showed that mature iNKT cells have reduced mitochondrial respiratory reserve and iNKT cell development was highly sensitive to perturbation of mitochondrial function. Mice with T cell-specific ablation of Rieske Iron-Sulphur protein (T-Uqcrfs1-/-), an essential subunit of mitochondrial complex III, had a dramatic reduction of iNKT cells in the thymus and periphery, but minimal effects on conventional T cell development. Residual iNKT cells in T-Uqcrfs1-/- mice retained ability to proliferate but exhibited increased apoptosis, decreased TCR signaling and impaired responses to TCR and IL-15 stimulation. Furthermore, knocking down RISP in mature iNKT cells diminished their cytokine production, correlating with reduced NFATC2 activity. Collectively, our data demonstrate a critical role for mitochondrial metabolism in iNKT cell development and activation outside of supporting bioenergetic demands. Thymic cells were obtained from 2 Uqcrfs1fl/fl; CD4-Cre+ mice and 2 heterozygous littermate controls. CD4+/CD8+ DP thymocytes were sorted by FACS BD Aria with a purity more than 98%. RNA was extracted with RNAeasy® Mini Kit according to the protocol of the manufacture (Qiagen). Libraries were generated using the Illumina TruSeq preparation kit and sequenced on HiSeq4000 at Northwestern's NUSeq Core. Reads were analyzed through the Ceto pipeline (https://github.com/ebartom/NGSbartom) using STAR (Dobin et al., 2013) for alignment on mm10 mouse genome, HTSeq (Anders et al., 2015) for read counting, and edgeR (Robinson et al., 2010) for differential expression analysis.