Project description: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 inflammation1. Th17 cells have unique metabolic features, including a stem cell-like signature2,3 and reliance on mitochondrial respiratory chain function and tricarboxylic acid (TCA) cycle to coordinate metabolic and epigenetic remodeling4,5. Dynamic changes in mitochondrial membrane morphology are key to sustain organelle function6. 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) but dispensable in other T cell subsets. We find that Th17 cells rely on mitochondrial fusion as a result of their low metabolic activity. Thus, lowering metabolic activity in other T cell subsets by nutrient restriction was sufficient to increase reliance on mitochondrial fusion for effector function. Transcriptional, proteomic, and metabolomic profiling identified the serine/threonine kinase liver associated kinase B1 (LKB1) as an essential node coupling mitochondrial function to cytokine expression in T cells. By genetic and metabolomic approaches, we demonstrate that LKB1 regulates IL-17A expression by controlling TCA cycle metabolites and transcriptional remodeling. Th-17 cell-specific deletion of optic atrophy 1 (OPA1), a protein involved in mitochondrial inner membrane fusion and cristae organization, reduced autoimmune pathogenesis in a mouse model of multiple sclerosis, while additional deletion of LKB1 restored disease. Our findings highlight distinct mitochondrial requirements in CD4+ T cells, identify mitochondrial membrane fusion as a major determinant of Th17 responses, and reveal LKB1 as a sensor of mitochondrial integrity that links mitochondrial cues to effector programs in Th17 cells.
Project description: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 inflammation1. Th17 cells have unique metabolic features, including a stem cell-like signature2,3 and reliance on mitochondrial respiratory chain function and tricarboxylic acid (TCA) cycle to coordinate metabolic and epigenetic remodeling4,5. Dynamic changes in mitochondrial membrane morphology are key to sustain organelle function6. 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) but dispensable in other T cell subsets. We find that Th17 cells rely on mitochondrial fusion as a result of their low metabolic activity. Thus, lowering metabolic activity in other T cell subsets by nutrient restriction was sufficient to increase reliance on mitochondrial fusion for effector function. Transcriptional, proteomic, and metabolomic profiling identified the serine/threonine kinase liver associated kinase B1 (LKB1) as an essential node coupling mitochondrial function to cytokine expression in T cells. By genetic and metabolomic approaches, we demonstrate that LKB1 regulates IL-17A expression by controlling TCA cycle metabolites and transcriptional remodeling. Th-17 cell-specific deletion of optic atrophy 1 (OPA1), a protein involved in mitochondrial inner membrane fusion and cristae organization, reduced autoimmune pathogenesis in a mouse model of multiple sclerosis, while additional deletion of LKB1 restored disease. Our findings highlight distinct mitochondrial requirements in CD4+ T cells, identify mitochondrial membrane fusion as a major determinant of Th17 responses, and reveal LKB1 as a sensor of mitochondrial integrity that links mitochondrial cues to effector programs in Th17 cells.
Project description: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 inflammation1. Th17 cells have unique metabolic features, including a stem cell-like signature2,3 and reliance on mitochondrial respiratory chain function and tricarboxylic acid (TCA) cycle to coordinate metabolic and epigenetic remodeling4,5. Dynamic changes in mitochondrial membrane morphology are key to sustain organelle function6. 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) but dispensable in other T cell subsets. We find that Th17 cells rely on mitochondrial fusion as a result of their low metabolic activity. Thus, lowering metabolic activity in other T cell subsets by nutrient restriction was sufficient to increase reliance on mitochondrial fusion for effector function. Transcriptional, proteomic, and metabolomic profiling identified the serine/threonine kinase liver associated kinase B1 (LKB1) as an essential node coupling mitochondrial function to cytokine expression in T cells. By genetic and metabolomic approaches, we demonstrate that LKB1 regulates IL-17A expression by controlling TCA cycle metabolites and transcriptional remodeling. Th-17 cell-specific deletion of optic atrophy 1 (OPA1), a protein involved in mitochondrial inner membrane fusion and cristae organization, reduced autoimmune pathogenesis in a mouse model of multiple sclerosis, while additional deletion of LKB1 restored disease. Our findings highlight distinct mitochondrial requirements in CD4+ T cells, identify mitochondrial membrane fusion as a major determinant of Th17 responses, and reveal LKB1 as a sensor of mitochondrial integrity that links mitochondrial cues to effector programs in Th17 cells.
Project description: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.
Project description:CD4+ T cell differentiation requires metabolic reprogramming to fulfil the bioenergetic demands of proliferation and effector function, and enforce specific transcriptional programmes1-3. Mitochondrial membrane dynamics sustains mitochondrial processes4, including respiration and tricarboxylic acid (TCA) cycle metabolism5, but whether mitochondrial membrane remodelling orchestrates CD4+ T cell differentiation remains unclear. Here we show that unlike other CD4+ T cell subsets, T helper 17 (TH17) cells have fused mitochondria with tight cristae. T cell-specific deletion of optic atrophy 1 (OPA1), which regulates inner mitochondrial membrane fusion and cristae morphology6, revealed that TH17 cells require OPA1 for its control of the TCA cycle, rather than respiration. OPA1 deletion amplifies glutamine oxidation, leading to impaired NADH/NAD+ balance and accumulation of TCA cycle metabolites and 2-hydroxyglutarate-a metabolite that influences the epigenetic landscape5,7. Our multi-omics approach revealed that the serine/threonine kinase liver-associated kinase B1 (LKB1) couples mitochondrial function to cytokine expression in TH17 cells by regulating TCA cycle metabolism and transcriptional remodelling. Mitochondrial membrane disruption activates LKB1, which restrains IL-17 expression. LKB1 deletion restores IL-17 expression in TH17 cells with disrupted mitochondrial membranes, rectifying aberrant TCA cycle glutamine flux, balancing NADH/NAD+ and preventing 2-hydroxyglutarate production from the promiscuous activity of the serine biosynthesis enzyme phosphoglycerate dehydrogenase (PHGDH). These findings identify OPA1 as a major determinant of TH17 cell function, and uncover LKB1 as a sensor linking mitochondrial cues to effector programmes in TH17 cells.
Project description:RORgt is known to instruct the differentiation of Th17 cells that mediate the pathogenesis of autoimmune diseases. However, it remains unknown whether RORgt plays a distinct role in the differentiation and effector function of Th17 cells. Here we show that mutation of RORgt lysine 256, a ubiquitination site, to arginine (K256R) separates the RORgt role in these two functions. Preventing ubiquitination at K256 via arginine substitution does not affect RORgt-dependent thymocyte development and Th17 differentiation in vitro and in vivo, however, greatly impaired the pathogenesis of Th17 cell-mediated experimental autoimmune encephalomyelitis (EAE). Mechanistically, K256R mutation impairs RORgt to bind to and activate Runx1 expression critical for Th17-mediated EAE. Thus, RORgt regulates the effector function of Th17 cells in addition to Th17 differentiation. This work informs the development of RORgt-based therapies that specifically target the effector function of Th17 cells responsible for autoimmunity.