Project description:Regulatory T cells (Treg cells) are important to maintain self-tolerance. In tissues, Treg cells can perform non-classical functions, for example, they are implicated in regulating metabolic processes in the adipose tissue. Their function in the liver is less well understood. We found here that Treg cells are important to secure the peripheral hepatic circadian rhythm of core-clock regulators and clock-controlled genes. Undisturbed metabolism in the liver required the presence of Treg cells and was especially important in the early postnatal phase, a distinct time period at around day 10, when the liver had not fully matured and Treg cells proliferated and accumulated in the liver-tissue. Our findings highlight a critical role for Treg cells to establish and maintain liver homeostasis.
Project description:The mechanistic target of rapamycin (mTOR) pathway integrates diverse environmental inputs, including immune signals and metabolic cues, to direct T cell fate decisions1. Activation of mTOR, comprised of mTORC1 and mTORC2 complexes, delivers an obligatory signal for proper activation and differentiation of effector CD4+ T cells2,3, whereas in the regulatory T cell (Treg) compartment, the Akt-mTOR axis is widely acknowledged as a crucial negative regulator of Treg de novo differentiation4-8 and population expansion9. However, whether mTOR signaling affects the homeostasis and function of Tregs remains largely unexplored. Here we show that mTORC1 signaling is a pivotal positive determinant of Treg function. Tregs have elevated steady-state mTORC1 activity compared to naïve T cells. Signals via T cell receptor (TCR) and IL-2 provide major inputs for mTORC1 activation, which in turn programs suppressive function of Tregs. Disruption of mTORC1 through Treg-specific deletion of the essential component Raptor leads to a profound loss of Treg suppressive activity in vivo and development of a fatal early-onset inflammatory disorder. Mechanistically, Raptor/mTORC1 signaling in Tregs promotes cholesterol/lipid metabolism, with the mevalonate pathway particularly important for coordinating Treg proliferation and upregulation of suppressive molecules CTLA-4 and ICOS to establish Treg functional competency. In contrast, mTORC1 does not directly impact the expression of Foxp3 or anti- and pro-inflammatory cytokines in Tregs, suggesting a non-conventional mechanism for Treg functional regulation. Lastly, we provide evidence that mTORC1 maintains Treg function partly through inhibiting the mTORC2 pathway. Our results demonstrate that mTORC1 acts as a fundamental ‘rheostat’ in Tregs to link immunological signals from TCR and IL-2 to lipogenic pathways and functional fitness, and highlight a central role of metabolic programming of Treg suppressive activity in immune homeostasis and tolerance. We used microarrays to explore the gene expression profiles differentially expressed in regulatory T-cells from wild-type and CD4(cre) x Raptor(fl/fl) mice
Project description:Project abstract: Foxp3+ T regulatory (Treg) cells have important functions in suppressing immune cell activation and establishing normal immune homeostasis. How Treg cells maintain their identity is not completely understood. Here we show that Ndfip1, a co-activator of Nedd4-family E3 ubiquitin ligases, is required for Treg cell stability and function. Ndfip1 deletion in Treg cells disrupts immune homeostasis and results in autoinflammatory disease. Ndfip1-deficient Treg cells are highly proliferative and are more likely to lose Foxp3 expression to become IL-4-producing TH2 effector cells. Proteomic analyses indicate that Ndfip1 deficiency alters the metabolic signature of Treg cells. Metabolic profiling reveals elevated glycolysis and increased mTORC1 signalling. Additional data suggest that Ndfip1 restricts Treg cell metabolic capacity and IL-4 production via distinct mechanisms. Thus, Ndfip1 preserves Treg lineage stability by preventing the expansion of highly proliferative and metabolically active cells that can cause immunopathology via secretion of IL-4.
Project description:Regulatory T (Treg) cells are highly enriched in the visceral adipose tissue (VAT) to maintain metabolic homeostasis, but they are lost during obesity. Currently, how VAT Treg cells rewire cellular metabolism to support their homeostatic clonal expansion, and whether this process is disrupted in obesity, is unclear. Here, we found that cholesterol metabolism was uniquely upregulated in VAT-, but not other non-lymphoid-tissue Treg cells. Disrupting cholesterol homeostasis (CH) by Treg-specific deletion of Srebf2 led to a specific loss of VAT Treg cells and enhanced obesity-induced systemic metabolic dysfunction. Mechanistically, Srebf2-mediated CH potentiated strong TCR signaling, which specifically promoted the clonal expansion of ST2hi, but not other, VAT Treg subsets. However, long-term high-fat-diet feeding disrupted VAT Treg CH and impaired ST2hi VAT Treg clonal expansion. Restoring Treg CH rescued VAT Treg accumulation in obese mice, suggesting CH modulation could be a potential option for Treg-targeted therapies in obesity-associated metabolic diseases.
Project description:Foxp3+ regulatory T (Treg) cells are a subset of CD4 T cells that play a potent and indispensable role in regulating immunity and tolerance. The precise mechanisms by which Treg cells mediate such functions have extensively been explored, and there are many cellular and molecular factors that are instrumental for adequate Treg cell functions. miRNAs, small non-coding RNA molecules, are one of the factors capable of modulating Treg cell functions. In this study, we report that miR-342 is essential for Treg cells to mitigate autoimmune inflammation in the central nervous system. Utilizing novel mouse models with Treg cell-specific miR-342 deficiency or overexpression, we demonstrate that miR-342 expression in Treg cells, while dispensable for immune homeostasis at steady-state conditions, is necessary for Treg cells to control inflammatory responses. Mechanistically, we found that Treg cells deficient in miR-342 display dysregulated metabolic programming, elevated glycolysis and decreased oxidative phosphorylation, a metabolic phenotype associated with functionally defective Treg cells. Collectively, our findings uncover that miR-342 may serve a master regulator of Treg cell metabolism and functions.