Regulatory T cells require the phosphatase PTEN to restrain type 1 and follicular helper T-cell responses
ABSTRACT: The interplay between effector and regulatory T (Treg) cells is crucial for adaptive immunity, but how Treg control effector cell flexibility is elusive. We found that the phosphatase PTEN links Treg stability to the repression of TH1 and TFH (follicular helper) responses. Depletion of PTEN in Treg resulted in excessive TFH and germinal center responses and spontaneous inflammatory disease. These defects are considerably blocked by deletion of Interferon-γ, indicating coordinated control of TH1 and TFH responses. Mechanistically, PTEN maintains Treg stability and proper metabolic balance between glycolysis and mitochondrial fitness. Moreover, PTEN deficiency markedly upregulates mTORC2-Akt activity, and loss of this activity restores PTEN-deficient Treg function. Our studies establish a PTEN-mTORC2 axis that actively maintains Treg stability and coordinates Treg-mediated control of effector cell flexibility. We used microarrays to explore the gene expression profiles differentially expressed in CD4+CD25+Foxp3-YFP+ Treg cells from wild-type (WT; C57BL/6 crossed with Foxp3-Cre) and Ptenfl/flFoxp3-Cre (Ptenfl/fl mice crossed with Foxp3-Cre) mice
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:Regulatory T (Treg) cells harbor immune suppressive capacity and are crucial for the maintenance of peripheral tolerance. Treg cells are considered to be heterogenic, where compromised FOXP3 expression results in the generation of exTreg cells. Here we report that the E3 deubiquitinase USP21 prevents the depletion of FOXP3 protein and restricts tissue-resident exTreg cell generation. Mice lacking USP21 in Treg cells display immune disorders characterized by spontaneous T cell activation and excessive T helper type 1 (Th1) skewing. USP21 stabilizes FOXP3 protein by mediating its deubiquitination and therefore helps to maintain the expression of Treg signature genes. Moreover, at inflamed loci, tissue-resident USP21-deficient Treg cells display a Th1-like effector phenotype. Therefore, we demonstrate how USP21 controls the identity of tissue-resident Treg cells by preventing FOXP3 loss. Overall design: We purified CD4+CD25hiYFP+ Treg cells from spleens and LNs of Foxp3-YFP-Cre mice or FOXP3-YFP-Cre/USP21-floxp/floxp mice and performed RNA-seq experiments subsequently. mRNA profiles were further analyzed and compared according to standard protocols.
Project description:Foxp3-expressing regulatory (Treg) T cells are essential for immunological tolerance, where loss of this transcription factor leads to uncontrolled T cell responses and their associated clinical presentation of systemic autoimmunity in mice and humans. Importantly, Foxp3+ Tregs result from different origins and are either generated in the thymus (tTreg) or from conventional CD4+ T cells in the periphery (pTreg). In addition, Treg cells may adopt specific effector Treg phenotypes, reflecting the diversity of functional demands in the different tissues of the body. Here, we report that Foxp3+ T cells expressing the Th17 master transcription factor, RORγt, represent a stable effector Treg lineage that is specifically enriched in intestinal organs and gut-associated lymphoid tissues in mice possessing a complex microbial microflora. Simultaneous expression of Foxp3 and RORγt promotes the transcription of both Treg- and Th17-associated genes in Foxp3+RORγt+ T cells; however, epigenetic profiling of the Treg-specific demethylated region (TSDR) and other Treg-associated genes revealed a high degree of similarity between conventional Tregs and Foxp3+RORγt+ T cells, indicating that these cells have a stable regulatory, rather than inflammatory, function. Indeed, adoptive transfer of Foxp3+RORγt+ T cells in the context of T cell transfer colitis not only confirmed their Treg function and lineage stability in vivo, it also revealed a significantly enhanced regulatory capacity as compared to RORγt+ Treg cells. Thus, our data suggest that RORγt expression in Tregs is essential for optimal regulation of gut-specific immune responses, which renders them an important effector Treg lineage in the intestinal system. Overall design: To study the global relationship in their gene expression profiles, we sorted Foxp3-RORγt- CD4+ T cells, Foxp3+(RORγt-) Treg cells, RORγt+(Foxp3-) and Foxp3+RORγt+ T cells from splenocytes, peripheral LN and mesenteric LN cells pooled together in order to avoid bias due to a specific tissue location.
Project description:Regulatory T (Treg) cells respond to immune and inflammatory signals to mediate immunosuppression, but how the functional integrity of Treg cells is maintained under activating environments is unclear. Here we show that autophagy is active in Treg cells and supports their lineage stability and survival fitness. Treg cell–specific deletion of Atg7 or Atg5, both essential genes in autophagy, leads to loss of Treg cells, greater tumor resistance and development of inflammatory disorders. Atg7-deficient Treg cells show increased apoptosis and readily lose expression of the transcription factor Foxp3, especially after activation. Mechanistically, autophagy deficiency upregulates mTORC1 and c-Myc and glycolytic metabolism, which contributes to defective Treg function. Therefore, autophagy couples environmental signals and metabolic homeostasis to protect lineage and survival integrity of Treg cells in activating contexts. Overall design: We used microarrays to explore the gene expression profiles differentially expressed in CD4+Foxp3-YFP+ Treg cells from untreated and rapamycin-treated Atg7+/- (Atg7-het; Atg7 +/fl crossed with Foxp3-Cre) and Atg7-/- (Atg7-KO; Atg7 fl/fl mice crossed with Foxp3-Cre) mice
Project description:Foxp3+ regulatory T (Treg) cells restrict immune pathology in inflamed tissues; however, an inflammatory environment presents a threat to Treg cell identity and function. We here establish a transcriptional signature of central nervous system (CNS) Treg cells that accumulate during experimental autoimmune encephalitis (EAE) and identify a pathway that maintains Treg cell function and identity during severe inflammation. This pathway was dependent on the transcriptional regulator Blimp1, which prevented dismantling of Foxp3 expression and "toxic" gain-of-function of Treg cells in the inflamed CNS. Blimp1 negatively regulated IL-6- and STAT3-mediated methylation of Treg cell-specific conserved non-coding sequence 2 (CNS2) in the Foxp3 locus. Consequently, CNS2 was heavily methylated when Blimp1 was ablated, leading to loss of Foxp3 expression and severe disease. These findings identify a Blimp1-dependent epigenetic pathway that preserves Treg cell stability in inflamed non-lymphoid tissues. Overall design: Comparison of DNA accessibility by Omni-ATAC-seq in conventional T cells (Tconv) and regulatory T cells (Treg) of wild-type vs Treg conditional Blimp1 deficient mice isolated from the CNS and spleen at the peak of experimental autoimmune encephalitis (EAE). All samples were FACS sorted ex vivo according to CD4+Foxp3(GFP)- = Tconv and CD4+Foxp3(GFP)+ = Treg from mixed bone morrow chimeras with congenically marked wild-type (CD45.1) and Treg conditional Blimp1 KO compartments (CD45.2).
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:Roquin proteins are required to preclude spontaneous T cell activation and aberrant T follicular helper (Tfh) or T helper 17 (Th17) differentiation. Here, we show that deletion of Roquin encoding alleles in regulatory T cells (Tregs) also caused the activation of conventional T cells. These Tregs exhibited a follicular Treg phenotype, CD25 downregulation and could not protect from colitis. Mechanistically, Roquin was required for full expression and activity of Pten and Foxo1, two essential signaling molecules in Tregs and effector T cells. Roquin upregulated Pten by interfering with miR-17~92 binding to an overlapping cis-element in the Pten 3' UTR and downregulated the Foxo1-specific E3 ubiquitin ligase Itch. Loss of Roquin enhanced mTOR signaling and global protein synthesis, while inhibition of PI3K or mTOR in Roquin-deficient CD4+ T cells corrected increased Tfh and Th17 differentiation. Thereby, the control of PI3K-mTOR signaling by Roquin prevents autoimmunity through T cell-intrinsic and Treg-mediated regulation. Overall design: Examination of transcriptome and ribosome occupancy in MEF and T cells upon Roquin expression and inhibition. Examination of Roquin binding sites in the mouse transcriptome of MEF cells. Examination of transcriptome in CD25+ and CD25- Treg cells from WT and Roquin DKO mice.
Project description:The transcription factor Thpok is required for intrathymic CD4+ T cell differentiation and, together with its homolog LRF, supports CD4+ T cell helper effector responses, However, it is not known if these factors are needed for the T regulatory arm of MHC-II responses. We inactivated the genes encoding both factors in differentiated Treg cells, to see whether how they are redundantly required to maintain the size and function of the post-thymic Treg pool and for immune homeostasis. Overall design: We compared YFP+ LRF and Thpok-deficient Treg cells with two distinct controls: (i) CD25+ YFP– cells (Thpok and LRF-sufficient ‘animal control’ cells, expressing the Foxp3+ allele) obtained from the same female mice as the YFP+ Treg cells, and (ii) YFP+ Treg cells from Foxp3+/ YFP Cre Thpok+/+ Lrf+/+ female mice (‘genetic controls’ which express the Foxp3YFP Cre allele).
Project description:T follicular helper cells (TFH) are critical for the development and maintenance of germinal centers (GC) and humoral immune responses. During chronic HIV/SIV infection TFH accumulate, possibly as a result of antigen persistence. The HIV/SIV-associated TFH expansion may also reflect lack of regulation by suppressive follicular regulatory CD4+ T-cells (TFR). TFR are natural regulatory T-cells (TREG) that migrate into the follicle and, similarly to TFH, up-regulate CXCR5, Bcl-6, and PD1. Here we identified TFR as CD4+CD25+FoxP3+CXCR5+PD1hiBcl-6+ within lymph nodes of rhesus macaques (RM) and confirmed their localization within the GC by immunohistochemistry. RNA sequencing showed that TFR exhibit a distinct transcriptional profile with shared features of both TFH and TREG, including intermediate expression of FoxP3, Bcl-6, PRDM1, IL-10, and IL-21. In healthy, SIV-uninfected RM, we observed a negative correlation between frequencies of TFR and both TFH and GC B-cells as well as levels of CD4+ T-cell proliferation. Following SIV infection, the TFR/TFH ratio was reduced with no change in the frequency of TREG or TFR within the total CD4+ T-cell pool. Finally, we examined whether higher levels of direct virus infection of TFR were responsible for their relative depletion post-SIV infection. We found that TFH, TFR and TREG sorted from SIV- infected RM harbor comparable levels of cell-associated viral DNA. Our data suggests that TFR may contribute to the regulation and proliferation of TFH and GC B-cells in vivo and that a decreased TFR/TFH ratio in chronic SIV infection may lead to unchecked expansion of both TFH and GC B-cells. TFR, TFH, TREG and bulk CD4 cells were sorted from spleens of 5 uninfected and 5 infected RM.
Project description:Sirtuin-1 (Sirt1), a class III histone/protein deacetylase is central to cellular metabolism, stress responses and aging, but its contributions to various host immune functions have been little investigated. To study the role of Sirt1 in T-cell functions, we undertook targeted deletions by mating mice with a floxed Sirt1 gene to mice expressing CD4-cre or Foxp3-cre recombinase, respectively. We found that Sirt1 deletion left conventional T-effector cell activation, proliferation and cytokine production largely unaltered. However, Sirt1 targeting promoted the expression and acetylation of Foxp3, a key transcription factor in T-regulatory (Treg) cells, and increased Treg suppressive functions in vitro and in vivo. Consistent with these data, mice with targeted deletions of Sirt1 in either CD4+ T-cells or Foxp3+ Treg cells exhibited prolonged survival of MHC-mismatched cardiac allografts. Allografts in Sirt1 targeted recipients showed long-term preservation of myocardial histology and infiltration by Foxp3+ Treg cells. Comparable results were seen in wild-type allograft recipients treated with Sirt1 inhibitors, such as EX-527 and splitomicin. Hence, Sirt1 may inhibit Treg functions and its targeting may have therapeutic value in autoimmunity and transplantation. Overall design: RNA from three independent samples from magnetically separated CD4+CD25+ Treg of Sirt1 knock out, compared to wild type (C57BL6) control