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Mitochondrial calcium uniporter complex controls T-cell-mediated immune responses

ABSTRACT: T-cell receptor-induced Ca2+ signals are essential for proper T-cell activation and function. In this context, mitochondria play an important role and take up Ca2+ to support elevated bioenergetic demands. The protein machinery that regulates mitochondrial Ca2+ (mCa2+) uptake; the mitochondrial calcium uniporter (MCU) complex, could be thus implicated in T-cell immunity. However, the exact role of MCU in T-cells is not understood. Here, we show that upon activation of naïve T-cells, the MCU complex undergoes a compositional rearrangement that causes elevated mCa2+ uptake and increased bioenergetic output. Transcriptome and proteome analyses reveal molecular determinants involved in mitochondrial functional reprograming and identify signaling pathways controlled by MCU. MCUa knockdown diminishes mCa2+ uptake, mitochondrial respiration and ATP production as well as T-cell invasion and cytokine secretion. In vivo, downregulation of MCUa in rat CD4+ T-cells suppresses autoimmune responses in a multiple sclerosis model of inflammatory experimental autoimmune encephalomyelitis. In summary, Ca2+ uptake through MCU is essential for proper T-cell function and is involved in autoimmunity. T-cell specific MCU inhibition is a potential tool for treating autoimmune disorders.

ORGANISM(S): Homo sapiens

PROVIDER: GSE253049 | GEO | 2024/10/23

REPOSITORIES: GEO

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Project description:Chronic low-grade inflammation is a hallmark of aging, but its etiology is not well understood. Mitochondrial dysfunction has been linked to both cellular senescence and age-related inflammation or inflammaging but fundamental mechanisms underlying these links are unclear. We analyzed age-related gene expression in different human tissues and discovered that in blood, the mRNA expression of Mitochondrial Calcium Uniporter (MCU) and its regulatory subunit MICU1 correlated inversely with age. MCU is the pore-forming subunit of a Ca2+-selective ion channel complex residing in the mitochondrial inner membrane and is the main conduit for Ca2+-influx into the mitochondrial matrix. Based on these findings we tested the simple hypothesis that mitochondrial Ca2+ uptake capacity of macrophages decreases with age. We found a significant reduction in the mitochondrial Ca2+-uptake capacity of macrophages derived from aged (80-90 weeks) mice. Notably, these macrophages display amplified cytosolic Ca2+ elevations and increased inflammatory output. To test the salience of mitochondrial calcium uptake in regulating macrophage inflammatory output, we deleted Mcu selectively in macrophages. The Mcu-/- macrophages of young mice (<25 weeks) express more inflammatory genes at baseline and show a hyper-inflammatory response when stimulated. We show that reduced mitochondrial Ca2+ amplifies cytosolic Ca2+ oscillations and potentiates downstream NFkB activation, which is central to inflammation. The regulation of inflammatory response by mitochondrial Ca2+ uptake is also seen readily in human macrophages. The siRNA-mediated knockdown of MCU in human blood derived macrophages recapitulates the phenomenon – the mitochondrial Ca2+-uptake is greatly reduced, cytosolic Ca2+ elevations are more pronounced, and the macrophages are hyper-inflammatory. Our findings pinpoint the MCU complex as a keystone molecular apparatus that links age-related changes in mitochondrial physiology to macrophage-mediated inflammation. Resident macrophages are intrinsic to every organ system and the steady erosion of their mitochondrial Ca2+-uptake capacity may play a germinal or exacerbating role in many age-related neurodegenerative, cardiometabolic, renal and musculoskeletal diseases that afflict us.

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Mitochondrial calcium uniporter complex controls T-cell-mediated immune responses

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