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:Regulatory T (Treg) cells characterized by expression of the transcription factor forkhead box P3 (Foxp3) maintain immune homeostasis by suppressing self-destructive immune responses1-4. Foxp3 operates as a late acting differentiation factor controlling Treg cell homeostasis and function5, whereas the early Treg cell lineage commitment is regulated by the Akt kinase and the forkhead box O (Foxo) family of transcription factors6-10. However, whether Foxo proteins act beyond the Treg cell commitment stage to control Treg cell homeostasis and function remains largely unexplored. Here we show that Foxo1 is a pivotal regulator of Treg cell function. Treg cells express high amounts of Foxo1, and display reduced T-cell receptor-induced Akt activation, Foxo1 phosphorylation, and Foxo1 nuclear exclusion. Mice with Treg cell-specific deletion of Foxo1 develop a fatal inflammatory disorder similar in severity to Foxp3-deficient mice, but without the loss of Treg cells. Genome-wide analysis of Foxo1 binding sites reveals ~300 Foxo1-bound target genes, including the proinflammatory cytokine Ifng, that do not appear to be directly regulated by Foxp3. These findings demonstrate that the evolutionarily ancient Akt-Foxo1 signaling module controls a novel genetic program indispensable for Treg cell function. Treg cells were isolated from wild-type B6 mice or Foxo1tagBirA mice in which foxo1 is endogenously biotinylated. Foxo1 binding targets in Treg cells were identified by using Foxo1 antibody- and Streptavidin- ChIP-Seq approaches.
Project description:Foxp3+ regulatory T cells (Treg cells) maintain immunological tolerance and their deficiency results in fatal multi-organ autoimmunity. Although heightened T cell receptor (TCR) signaling is critical for the differentiation of Treg cells, the role of TCR signaling in Treg cell function remains largely unknown. Here we demonstrate inducible ablation of the TCR results in Treg cell dysfunction which cannot be attributed to impaired Foxp3 expression, decreased expression of Treg cell signature genes or altered ability to sense and consume interleukin 2. Rather, TCR signaling was required for maintaining the expression of a limited subset of genes comprising 25% of the activated Treg cell transcriptional signature. Our results reveal a critical role for the TCR in Treg cell suppressor capacity. Array expression of Foxp3-CreERT2 CalphaFL/WT mice
Project description:Regulatory T (Treg) cells characterized by expression of the transcription factor forkhead box P3 (Foxp3) maintain immune homeostasis by suppressing self-destructive immune responses1-4. Foxp3 operates as a late acting differentiation factor controlling Treg cell homeostasis and function5, whereas the early Treg cell lineage commitment is regulated by the Akt kinase and the forkhead box O (Foxo) family of transcription factors6-10. However, whether Foxo proteins act beyond the Treg cell commitment stage to control Treg cell homeostasis and function remains largely unexplored. Here we show that Foxo1 is a pivotal regulator of Treg cell function. Treg cells express high amounts of Foxo1, and display reduced T-cell receptor-induced Akt activation, Foxo1 phosphorylation, and Foxo1 nuclear exclusion. Mice with Treg cell-specific deletion of Foxo1 develop a fatal inflammatory disorder similar in severity to Foxp3-deficient mice, but without the loss of Treg cells. Genome-wide analysis of Foxo1 binding sites reveals ~300 Foxo1-bound target genes, including the proinflammatory cytokine Ifng, that do not appear to be directly regulated by Foxp3. These findings demonstrate that the evolutionarily ancient Akt-Foxo1 signaling module controls a novel genetic program indispensable for Treg cell function. Regulatory T cells were FACS sorted in WT mice (2 reps), Foxo1 KO mice (2 reps), mice expressing a constitutively active form of Foxo1 (1 rep), and Foxo1 KO mice expressing constitutively active Foxo1. We identified genes differentially expressed in WT vs. KO mice and assessed whether expression was recovered in the KO in presence of constitutively active Foxo1
Project description:Foxp3+Tregcells are essential modulators of immune responses but under specific conditions can acquire inflammatory properties and potentially contribute to disease pathogenesis. Here we show that the transcription factor Blimp1 is a critical regulator of Foxp3+Treg functional plasticity. The intrinsic expression of Blimp1 was required to prevent Treg from producing Th17-associated cytokines and acquiring an inflammatory phenotype while preserving Foxp3 expression. Mechanistically, Blimp1 acts as a direct repressor of the Il17a/Il17f genes in Foxp3+Treg and binding of Blimp1 at this locus is associated with altered chromatin status, reduced binding the co-activator p300, unaltered binding of the Th17-asssociated transcription factor RORt and more abundant binding of IRF4, which was required for the production of IL17A in Blimp1-deficient Foxp3+Tregcells, as shown by IRF4 siRNA-mediated knockdown. Consistent with their capacity to produce inflammatory cytokines, Blimp1-deficient Foxp3+Treg exacerbate Th17-mediated inflammation in vivo indicating that Blimp1 is required to prevent Treg cells from acquiring pathogenic properties
Project description:Regulatory T (Treg) cells play crucial roles in suppressing deleterious immune response. Here, we investigate how mechanistically Treg cells are induced and stabilized via transcriptional regulation of Treg lineage–specifying factor Foxp3. Acetylation of histone tails in the Foxp3 locus is induced during Treg cell development and required in cis for the initiation of Foxp3 transcription. Upon induction, histone acetylation signal largely acts in trans to sustain Foxp3 transcription via multiple factors. Subsequently, Tet-mediated DNA demethylation of Foxp3 cis-regulatory elements particularly enhancer CNS2 increases chromatin accessibility and protein binding, drastically stabilizing Foxp3 transcription, although histone acetylation still regulates global gene expression. These processes transform stochastic Treg cell induction into a stable cell fate, with the former sensitive and latter resistant to genetic and environmental perturbations. Thus, our study reveals distinct roles of histone acetylation in Foxp3 induction and maintenance, reflecting sequential mechanical switches governing Treg cell lineage specification.
Project description:Regulatory T (Treg) cells play crucial roles in suppressing deleterious immune response. Here, we investigate how mechanistically Treg cells are induced and stabilized via transcriptional regulation of Treg lineage–specifying factor Foxp3. Acetylation of histone tails in the Foxp3 locus is induced during Treg cell development and required in cis for the initiation of Foxp3 transcription. Upon induction, histone acetylation signal largely acts in trans to sustain Foxp3 transcription via multiple factors. Subsequently, Tet-mediated DNA demethylation of Foxp3 cis-regulatory elements particularly enhancer CNS2 increases chromatin accessibility and protein binding, drastically stabilizing Foxp3 transcription, although histone acetylation still regulates global gene expression. These processes transform stochastic Treg cell induction into a stable cell fate, with the former sensitive and latter resistant to genetic and environmental perturbations. Thus, our study reveals distinct roles of histone acetylation in Foxp3 induction and maintenance, reflecting sequential mechanical switches governing Treg cell lineage specification.
Project description:Regulatory T (Treg) cells play crucial roles in suppressing deleterious immune response. Here, we investigate how mechanistically Treg cells are induced and stabilized via transcriptional regulation of Treg lineage–specifying factor Foxp3. Acetylation of histone tails in the Foxp3 locus is induced during Treg cell development and required in cis for the initiation of Foxp3 transcription. Upon induction, histone acetylation signal largely acts in trans to sustain Foxp3 transcription via multiple factors. Subsequently, Tet-mediated DNA demethylation of Foxp3 cis-regulatory elements particularly enhancer CNS2 increases chromatin accessibility and protein binding, drastically stabilizing Foxp3 transcription, although histone acetylation still regulates global gene expression. These processes transform stochastic Treg cell induction into a stable cell fate, with the former sensitive and latter resistant to genetic and environmental perturbations. Thus, our study reveals distinct roles of histone acetylation in Foxp3 induction and maintenance, reflecting sequential mechanical switches governing Treg cell lineage specification.
Project description:Regulatory T (Treg) cells play crucial roles in suppressing deleterious immune response. Here, we investigate how mechanistically Treg cells are induced and stabilized via transcriptional regulation of Treg lineage–specifying factor Foxp3. Acetylation of histone tails in the Foxp3 locus is induced during Treg cell development and required in cis for the initiation of Foxp3 transcription. Upon induction, histone acetylation signal largely acts in trans to sustain Foxp3 transcription via multiple factors. Subsequently, Tet-mediated DNA demethylation of Foxp3 cis-regulatory elements particularly enhancer CNS2 increases chromatin accessibility and protein binding, drastically stabilizing Foxp3 transcription, although histone acetylation still regulates global gene expression. These processes transform stochastic Treg cell induction into a stable cell fate, with the former sensitive and latter resistant to genetic and environmental perturbations. Thus, our study reveals distinct roles of histone acetylation in Foxp3 induction and maintenance, reflecting sequential mechanical switches governing Treg cell lineage specification.