Themis1-mediated repression of SHP-1 activity promotes regulatory T cell suppressive functions through a Vav1-RelA signaling axis

Regulatory T cells (Tregs) expressing the transcription factor Foxp3 constitute a unique T cell lineage committed to suppressive functions and are crucial for suppressing aberrant immune responses in autoimmunity and allergy. Treg transcriptional landscape is tightly controlled by Foxp3-binding partners, including RelA. Although those DNA-binding complexes have been well characterized, the TCR signaling events that coordinate those dynamic molecular assembly are still poorly understood. Using a combination of genetic models, we show that the suppressive function of Tregs is controlled by a tri-molecular interplay between the signaling proteins Themis1, Vav1 and SHP-1. We identify the tyrosine phosphatase SHP-1 as a central component of an inhibitory circuit, which leads to the dephosphorylation of Vav1, which in turn is associated with a dramatic reduction of RelA activity and Treg suppressive function. Themis1 disconnects this circuit by blocking SHP-1 catalytic activity. Collectively, our results reveal a previously unappreciated pathway, whereby Themis1-mediated repression of SHP-1 activity promotes Tregs suppressive functions through a Vav1-RelA signaling axis. CD4+CD62L+CD25bright Tregs were sorted from Vav1R63W and Vav1R63WThemis1-T-/- mice. RNA was purified by using Rneasy Micro Kit (Qiagen). The RNA-sequencing was performed by Genoscreen company. The quality of the RNA-Seq data was assessed with FastQC. Then the reads were poly-A and adaptor-trimmed with Trim Galore. The reads were aligned to the transcriptome with STAR . MultiQC was used to assess the performance of the preprocessing steps . The genome assembly and annotation for the RNA-Seq data analysis was downloaded from ENSEMBL (version 90). The counts were normalized by the size factor method of DESeq2 . Next, the differential gene expression analysis was done with DESeq2 using SARTools R package with FDR<0.05. All analyses were performed within the R environment and most plots were produced with the ggplot2 package and pheatmap package.