Project description:CD4+CXCR5+Foxp3+ T follicular regulatory (TFR) cells control the germinal center responses. Like follicular helper T-cells, they express high levels of Nuclear Factor of Activated T-cells c1, predominantly its short isoform NFATc1/αA. Ablation of NFATc1 in Tregs prevents upregulation of CXCR5 and migration of TFR cells into B-cell follicles. By contrast, constitutive active NFATc1/αA defines the surface density of CXCR5, whose level determines how deep a TFR migrates into the GC and how effectively it controls antibody production. NFATc1/αA is necessary to overcome TFR-expressed B lymphocyte-induced maturation protein (Blimp-1), which can directly repress Cxcr5. Blimp-1 then reinforces the recruitment of NFATc1 to Cxcr5 by protein-protein interaction and by those means cooperates with NFATc1 for Cxcr5 transactivation. On the contrary, Blimp-1 is necessary to counterbalance NFATc1/αA, which strengthens the follicular development of Tregs, but bears the inherent risk of causing an ex-Treg phenotype.
Project description:Post-translational modification with SUMO is known to regulate the activity of transcription factors, but how SUMOylation of individual proteins might influence immunity is mostly unexplored. The NFAT transcription factors play an essential role in antigen receptor-mediated gene regulation. SUMOylation of NFATc1 represses IL-2 in vitro, but its role in T cell-mediated immune responses in vivo is not clear. To this end, we generated a novel Nfatc1 transgenic mouse, which prevents SUMO modification of NFATc1. Avoidance of NFATc1 SUMOylation ameliorated experimental autoimmune encephalomyelitis as well as graft-versus-host disease. An elevated IL-2 production promoted Treg expansion and suppressed autoreactive or alloreactive T cells. Mechanistically, increased IL-2 secretion counteracted IL-17 and IFN-γ expression through STAT5 and Blimp-1 induction. Then, Blimp-1 repressed IL-2 itself and the as well induced, proliferation-associated survival factor Bcl2A1. Collectively, we demonstrate that prevention of NFATc1 SUMOylation fine-tunes T-cell responses towards lasting tolerance. Thus, targeting NFATc1 SUMOylation presents a novel and promising strategy to treat T cell-mediated inflammatory diseases.
Project description:Post-translational modification with SUMO is known to regulate the activity of transcription factors, but how SUMOylation of individual proteins might influence immunity is mostly unexplored. NFATc1 is a transcription factor of the family of ‘Nuclear Factors of Activated T-cells’ which plays an essential role in antigen receptor-mediated gene regulation. It is expressed in multiple isoforms of which the longer isoforms can be modified by SUMOylation. SUMO modification of NFATc1 represses IL-2 in vitro, but its role in T cell-mediated immune responses in vivo is not clear. To this end, we generated a novel Nfatc1 transgenic mouse with lysine to arginine mutations, which abolish the SUMO modification within NFATc1’s C-terminal domain. Inhibition of NFATc1 SUMOylation ameliorated experimental autoimmune encephalomyelitis as well as graft-versus-host disease. This was due to elevated IL-2 production that promoted Treg expansion and suppressed autoreactive or alloreactive T cells. Mechanistically, increased IL-2 secretion counteracted IL-17 and IFN-γ expression through STAT5 and Blimp-1 induction. Blimp-1 also repressed IL-2 itself and the as well induced survival factor Bcl2A1. Still, lack of NFATc1 sumoylation fine-tunes T-cell responses towards lasting tolerance implying a novel approach to treat inflammatory diseases.
Project description:Antigen-specific effector CD8+ T cells deficient in Blimp-1 (Prdm1) do not acquire maximal effector functions, evade terminal differentiation, and more rapidly acquire some hallmark properties of memory CD8+ T cells. In this study, we compared the gene expression profiles of wildtype and Prdm1-/- LCMV-specific effector CD8+ T cells to better understand the molecular mechanisms underlying this striking phenotype. DNA microarray analysis was performed of DbGP33-41 and DbNP396-404 tetramer-positive effector CD8+ T cells FACS-sorted at day 8 post-LCMV infection from four independent samples of either Blimp-1 conditional knockout mice (CKO; Blimp-1flox/flox x GranzymeB-cre+) or wildtype (WT) littermate controls.
Project description:In lymphocytes, NFATc1 is the most prominent NFAT transcription factor which play a crucial role in the fate and activity of peripheral T and B cells. NFATc1 is synthesized in two prominent isoforms, the inducible short isoform NFATc1/aA and the constitutively expressed long isoform NFATc1/C. Several lines of evidence suggested that both isoforms differ markedly in their function. It was speculated that NFATc1/aA supports the proliferation and survival of lymphocytes, whereas NFATc1/C should support apoptosis and anergy induction. To proof this hypothesis we established WEHI 231 B lymphoma cells that stably (over-) express either NFATc1/aA or NFATc1/C. In preliminary experiments we could should that WEHI cells overexpressing NFATc1/aA were protected against apoptosis induction, while cells overexpressing NFATc1/C should a higher apoptosis rate. Transcriptom analysis of WEHI-231 cells overexpressing either NFATc1/aA or NFATc1/C were performed, along with a control group of WEHI-231 cells overexpressing the E.coli enzyme BirA Ligase (which is also present in all target cell lines since for further molecular assays the NFATc1 proteins were expressed as chimeric protein containing C-terminal bio-tags. The experimental results obtained indicate that the both NFATc1 proteins, NFATc1/aA and NFATc1/C, differ tremendously in their transcriptional properties.
Project description:Expression of Blimp-1 was specifically deleted in dendritic cells (DCs) by breeding Blimp-1 flox and CD11c-CRE mice. MiRNA expression was evaluated and compared from DCs, CD4+ T cells and total B cells from spleens of control and Blimp-1 KO mice. Age-matched (6-10 weeks old) female mice from control and Blimp-1 KO mice were sacrificed and spleens were collected. CD11chi/MHCIIhi DCs, CD4+TCRb+ T cells and B220+ B cells were sorted by FACSaria. MiRNA was measured from the total RNA preparation.
Project description:The goal of this study was to profile Blimp1 binding in E18.5 small intestine using a Blimp-1-eGFP knock-in allele, and to compare Blimp-1-eGFP genomic binding with Irf-1 genomic binding in normal small intestine. Changes in Irf-1 binding between wild type and Prdm1/Blimp-1 mutant small intestine were also assessed. ChIP-seq was performed for Blimp-1-eGFP in duplicate in E18.5 small intestine expressing the fusion protein using anti-GFP antibody. As a negative control a single anti-GFP ChIP was also performed in wild type small intestine. ChIP-seq for Irf-1 was performed in duplicate in both wild type and Prdm1/Blimp-1 mutant E18.5 small intestine using an anti-Irf-1 antibody. Duplicate IgG ChIP control in wild types was performed as a negative control. All samples had an associated input chromatin sample sequenced.
Project description:Differentiation of B cells into antibody secreting cells (ASCs), plasmablasts and plasma cells, is regulated by a network of transcription factors. Within this network factors including PAX5 and BCL6 prevent ASC differentiation and maintain the B cell phenotype whereas BLIMP-1 and high IRF4 expression promote plasmacytic differentiation. BLIMP-1 is thought to induce immunoglobulin secretion. While IRF4 is needed for the survival of ASCs, its role in the regulation of antibody secretion has been controversial. BCL6-deficient DT40 B cell line has upregulated BLIMP-1 expression and secrete antibodies. In order to study the role of IRF4 in regulation of antibody secretion we have created a double knockout (DKO) DT40 B cell line deficient in both IRF4 and BCL6. This DKO cell line did not upregulate PRDM1 (the gene encoding for BLIMP-1) expression or secrete IgM. Even enforced BLIMP-1 expression in DKO cells or IRF4-deficient cells could not induce IgM secretion while it did in WT cells. However, enforced IRF4 expression in DKO cells induced strong IgM secretion. Our findings support a model where IRF4 expression in addition to BLIMP-1 expression is required to induce antibody secretion.
Project description:We performed the newly mapping of genome-wide NFATc1 binding events in VEGF-stimulated primary cultured endothelial cells, by chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq). Combined NFATc1 ChIP-seq profile and the epigenetic histone marks revealed that predominant NFATc1-occupied peaks were overlapped with promoter marking but not silencer marking. DNA microarrays with NFATc1 expression or knockdown indicated the predominant NFATc1 binding targets were correlated with induced patterns. To determine NFATc1-regulated genes, a total of 5 samples were derived from human umbilical vein endothelial cells (HUVECs) stimulated with or without 50ng/mL VEGF (VEGF 60min and 0min, respectively), pretreated with cyclosporine A (VEGF 60min plus CsA) and infected with adenovirus expressing the control or constitutively active NFATc1 (Ad-control and Ad-NFATc1).
Project description:Expression of Blimp-1 was specifically deleted in dendritic cells (DCs) by breeding Blimp-1 flox and CD11c-CRE mice. MiRNA expression was evaluated and compared from DCs, CD4+ T cells and total B cells from spleens of control and Blimp-1 KO mice.