Project description:Regulatory T cells (Treg) have been shown to adopt a catabolic metabolic programme with increased capacity for fatty acid oxidation fuelled oxidative phosphorylation (OXPHOS). The role of Foxp3 in this metabolic shift is poorly understood. Here we show that Foxp3 was sufficient to induce a significant increase in the spare respiratory capacity of the cell, the extra OXPHOS capacity available to a cell to meet increased demands on energy in response to work. Foxp3-expressing cells were enhanced in their ability to utilise palmitate for respiration and, in addition, the activity of electron transport complexes I, II and IV were enhanced following Foxp3 expression. Foxp3 also imparts a selective advantage in ATP generation capacity, one that might be exploited as a source of adenosine for functional immunomodulation. In order to explore possible mechanisms for these differences in metabolism we conducted a quantitative proteomics study to compare the contribution of TGFβ and the transcription factor Foxp3 to the Treg proteome. We used quantitative mass spectrometry to examine differences between proteomes of nuclear and cytoplasmic Foxp3-containing CD4+ T cells from various sources with Foxp3- activated CD4 T cells, as well as Treg from human peripheral blood. Gene set enrichment analysis of our proteomic datasets demonstrated that Foxp3 expression is associated with a significant up regulation of several members of the mitochondrial electron transport chain. Not only does Foxp3 influence genes directly concerned with immune function, but also with the energy generating functions of Treg.
Project description:The Foxp3 transcription factor is a crucial determinant of both regulatory T (TREG) cell development and their functional maintenance. Appropriate modulation of tolerogenic immune responses therefore requires tight regulation of Foxp3 transcriptional output, and this involves both transcriptional and post-translational regulation. Here, we show that during T cell activation, phosphorylation of Foxp3 in TREG cells can be regulated by a TGFβ Activated Kinase 1 (TAK1)-Nemo Like Kinase (NLK) signaling pathway. NLK interacts with Foxp3 in TREG cells and directly phosphorylates Foxp3 on multiple serine residues. This phosphorylation results in stabilization of Foxp3 protein levels by preventing association with the STUB1 E3-ubiquitin protein ligase, resulting in both reduced ubiquitination and proteasome-mediated degradation. Conditional TREG cell NLK-knockout (NLKTREG) results in decreased TREG cell-mediated immunosuppression in vivo and NLK-deficient TREG cell animals develop more severe experimental autoimmune encephalomyelitis. Our data suggest a molecular mechanism, in which stimulation of TCR-mediated signaling can induce a TAK1-NLK pathway to sustain Foxp3 transcriptional activity through stabilization of protein levels, thereby maintaining TREG cell suppressive function. Pharmacological manipulation of this phosphorylation-ubiquitination axis may provide therapeutic opportunities for regulating TREG cell function, for example during cancer immunotherapy.
Project description:The transcription factor Foxp3 is indispensable for the ability of regulatory T (Treg) cells to suppress fatal inflammation. Here, we characterized the role of Foxp3 in chromatin remodeling and regulation of gene expression in actively suppressing Treg cells in an inflammatory setting. Although genome-wide Foxp3 occupancy of DNA regulatory elements was similar in resting and in vivo activated Treg cells, Foxp3-bound enhancers were poised for repression only in activated Treg cells. Following activation, Foxp3-bound sites showed reduced chromatin accessibility and selective H3K27 tri-methylation, which was associated with Ezh2 recruitment and downregulation of nearby gene expression. Thus, Foxp3 poises its targets for repression by facilitating formation of repressive chromatin in regulatory T cells upon their activation in response to inflammatory cues. The supplementary file foxp3_rest_act_table.txt includes Foxp3 ChIP data that is co-normalized with data from Foxp3 ChIP data from GSE40684. Foxp3 ChIP-seq, H3K27me3 ChIP-seq, and DNase-seq, were integrated with array expression data to find that Foxp3 is required for formation of repressive chromatin
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, whose identity and function are defined by the transcription factor Foxp3, are indispensable for immune homeostasis. It is unclear whether Foxp3 exerts its Treg lineage specification function through active modification of the chromatin landscape and establishment of new enhancers or by exploiting a pre-existing enhancer landscape. Analysis of the chromatin accessibility of Foxp3-bound enhancers in Treg and Foxp3-negative T cells showed that Foxp3 was bound overwhelmingly to pre-accessible enhancers occupied by its cofactors in precursor cells or a structurally related predecessor. Furthermore, the bulk of Foxp3-bound Treg cell enhancers lacking in Foxp3- CD4+ cells became accessible upon T cell receptor activation prior to Foxp3 expression with only a small subset associated with several functionally important genes being exclusively Treg cell-specific. Thus, in a late cellular differentiation process Foxp3 defines Treg cell functionality in an “opportunistic” manner by largely exploiting the preformed enhancer network instead of establishing a new enhancer landscape. Four transcription factors (Foxp3, Ets1, Elf1, and Cbfb) were immunoprecipated while crosslinked to chromatin. These experiments were then combined with DNase-seq data (being uploaded separately as part of ENCODE project) to find that Foxp3 binds exclusively to open chromatin. Data was also leveraged from GSE40657 and GSE33653.