LKB1/STK11-sensing of mitochondrial function controls Th17 cell responses

T helper 17 (Th17) cells are a distinct subset of CD4+ T cells necessary for maintaining gut homeostasis and have prominent roles in autoimmunity and inflammation. Th17 cells have unique metabolic features, including a stem cell-like signature and reliance on mitochondrial respiratory chain function and tricarboxylic acid (TCA) cycle to coordinate metabolic and epigenetic remodeling. Dynamic changes in mitochondrial membrane morphology are key to sustain organelle function. However, it remains unclear whether mitochondrial membrane remodeling orchestrates metabolic and differentiation events in Th17 cells. Here we demonstrate that mitochondrial membrane fusion and tight cristae organization are required for Th17 cell function (i.e. cytokine expression). As a genetic model system we employ Th17 specific deletion of optic atrophy 1 (OPA1), a gene that encodes a protein involved in mitochondrial inner membrane fusion and cristae organization. As a result, we find that Th17 cells rely on mitochondrial fusion (due to their low metabolic activity). Here, we carry out DIA-based differential quantitative proteomic analysis of murine wild-type and OPA1 knock-out Th17 cells. Through Ingenuity pathway analysis and together with transcriptional and metabolomic profiling we identify the serine/threonine kinase liver associated kinase B1 (LKB1/STK11) as an essential node coupling mitochondrial function to IL-17A cytokine expression in T cells.