T helper 17 (TH17) cells are heterogeneous and able to adopt pathogenic and non-pathogenic phenotypes. Identifying factors controlling pathogenic TH17 cells is of importance for their vital role in inflammation and immune-pathology. Here, we demonstrated that HMGCS1, a cholesterol biosynthesis precursor enzyme, was highly induced by inflammatory cytokines and preferentially expressed by pathogenic TH17 cells in vitro and in vivo. HMGCS1 specifically dictated pathogenic TH17 cell differentiation and augmented autoimmune diseases, yet it has no discernible effect on nonpathogenic TH17 cells. Unexpectedly, this role is independent of its canonical function in cholesterol metabolism but requires its catalytic Cys129 residue. Notably, HMGCS1 governs pTH17 cell generation and pathogenicity by leveraging an IRE1α-XBP1s–dependent ER stress response, which in turn transcriptionally activates the lineage-defining factor RORγt (encoded by Rorc). Mechanistically, HMGCS1 is located to the ER membrane, where it bound and stabilized IRE1α protein. This stabilization is achieved by preventing IRE1α’s interaction with the E3 ubiquitin ligase MARCH5, thereby inhibiting its K48-linked ubiquitination and subsequent degradation. Moreover, interfering with HMGCS1 or the ER stress response in T cells impedes pTH17 immunity and mitigates autoimmune disease in vivo. Therefore, our work unveils a noncanonical axis in which HMGCS1 sustains ER stress to license pTH17 differentiation during autoimmune responses.
Jie Sun, Ya-Li Lei, Huan-Huan Yang et al.· Science Advances· 0 citations
Type I immunity, mediated by IFN-γ, is essential for combating intracellular pathogens but also drives inflammatory diseases. How the immune system balances protective type I responses with pathological inflammation is elusive. While the IL-12-STAT4 pathway that promotes IFN-γ production is well-established, the intrinsic negative regulators remain unclear. We establish that RASA3 serves as a permissive checkpoint for type I immune responses. T cell-specific ablation of RASA3 amplified Th1/Tc1 immunity and IFN-γ expression, enhancing the clearance of Listeria monocytogenes but exacerbating allergic contact dermatitis. We further identify the hematopoietic cell kinase (HCK) as a direct kinase for STAT4, which binds to and phosphorylates it at the Tyr693 residue to elicit IFN-γ production. Mechanistically, RASA3 represses the translation of HCK via constraining ribosomal protein RPL36A expression. Additionally, the RASA3-HCK axis is conserved in human Th1 cells. Thus, we define a critical role of the RASA3-HCK-STAT4 axis in fine-tuning type I immunity and offer promising targets for intervening in Th1/Tc1-driven pathologies. IFN-γ-mediated type I immunity is important for clearing intracellular pathogens yet promotes inflammatory diseases. However, T cell-intrinsic negative regulators controlling IFN-γ expression remain poorly characterized. The authors here identify a role of the RASA3-HCK-STAT4 axis in tempering type I immunity.
Jiayu Song, Xiaoyu Liu, Jie Sun et al.· Nature Communications· 0 citations
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