Systemic lupus erythematosus (SLE) is characterized by uncontrolled secretion of autoantibodies by plasma cells. Although the functional importance of plasma cells and autoantibodies in SLE has been well established, the underlying molecular mechanisms of controlling autoantibody production remain poorly understood. Here we show that Peli1 has a B cell-intrinsic function to protect against lupus-like autoimmunity in mice. Peli1 deficiency in B cells induces autoantibody production via noncanonical NF-κB signaling. Mechanically, Peli1 functions as an E3 ligase to associate with NF-κB inducing kinase (NIK) and mediates NIK Lys48 ubiquitination and degradation. Overexpression of Peli1 inhibits noncanonical NF-κB activation and alleviates lupus-like disease. In humans, PELI1 levels negatively correlate with disease severity in SLE patients. Our findings establish Peli1 as a negative regulator of the noncanonical NF-κB pathway in the context of restraining the pathogenesis of lupus-like disease.

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Ubiquitination is an essential mechanism in the control of antiviral immunity upon virus infection. Here, we identify a series of ubiquitination-modulating enzymes that are modulated by vesicular stomatitis virus (VSV). Notably, TRIM24 is down-regulated through direct transcriptional suppression induced by VSV-activated IRF3. Reducing or ablating TRIM24 compromises type I IFN (IFN-I) induction upon RNA virus infection and thus renders mice more sensitive to VSV infection. Mechanistically, VSV infection induces abundant TRIM24 translocation to mitochondria, where TRIM24 binds with TRAF3 and directly mediates K63-linked TRAF3 ubiquitination at K429/K436. This modification of TRAF3 enables its association with MAVS and TBK1, which consequently activates downstream antiviral signaling. Together, these findings establish TRIM24 as a critical positive regulator in controlling the activation of antiviral signaling and describe a previously unknown mechanism of TRIM24 function.

Increased IFN-γ levels have been associated with systemic lupus erythematosus (SLE). However, the relationships among IFN-γ, type I interferons (IFNs) and clinical features have not been extensively studied. Peripheral blood samples from 44 SLE patients and 36 healthy donors (HDs) were collected. Quantitative real-time PCR was used to assess the mRNA expression of IFNG, type II IFN-inducible genes (IRF1, GBP1, CXCL9, CXCL10, and SERPING1, which are used for the type II IFN score), type I IFN-inducible genes (IRF7, MX1, ISG15, and ISG20, which are used for the type I IFN score), TBX21, and EOMES in peripheral blood mononuclear cells. Flow cytometry was used to measure the IFN-γ levels in lymphocytes. The mRNA levels of type II IFN-inducible genes, IFNG, TBX21, and EOMES were significantly higher in SLE patients than those in HDs. Similarly, the percentages of IFN-γ-producing cells in lymphocytes and their subsets in SLE patients were significantly increased. Linear regression indicated that IFNG expression levels and type II IFN scores were positively correlated with anti-double-stranded DNA autoantibody levels and Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) scores. Compared with patients with low type I IFN scores, patients with high type I IFN scores showed increased type II IFN scores and SLEDAI scores. Type II IFN scores were positively associated with type I IFN scores. The IFN-γ signaling pathway is activated in SLE patients and may be considered an index of disease activity. IFN-γ, together with type I IFNs, promotes the pathogenesis of SLE.

TGFβ is essential for the generation of anti-tumor Th9 cells; on the other hand, it causes resistance against anti-tumor immunity. Despite recent progress, the underlying mechanism reconciling the double-edged effect of TGFβ signaling in Th9-mediated cancer immunotherapy remains elusive. Here, we find that TGFβ-induced down-regulation of bifunctional apoptosis regulator (BFAR) represents the key mechanism preventing the sustained activation of TGFβ signaling and thus impairing Th9 inducibility. Mechanistically, BFAR mediates K63-linked ubiquitination of TGFβR1 at K268, which is critical to activate TGFβ signaling. Thus, BFAR deficiency or K268R knock-in mutation suppresses TGFβR1 ubiquitination and Th9 differentiation, thereby inhibiting Th9-mediated cancer immunotherapy. More interestingly, BFAR-overexpressed Th9 cells exhibit promising therapeutic efficacy to curtail tumor growth and metastasis and promote the sensitivity of anti–PD-1–mediated checkpoint immunotherapy. Thus, our findings establish BFAR as a key TGFβ-regulated gene to fine-tune TGFβ signaling that causes Th9 induction insensitivity, and they highlight the translational potential of BFAR in promoting Th9-mediated cancer immunotherapy.

T follicular helper (Tfh) cells are crucial for regulating autoimmune inflammation and protective immunity against viral infection. However, the molecular mechanism controlling Tfh cell differentiation is poorly understood. Here, through two mixed bone marrow chimeric experiments, we identified Peli1, a T cell-enriched E3 ubiquitin ligase, as an intrinsic regulator that inhibits Tfh cell differentiation. Peli1 deficiency significantly promoted c-Rel-mediated inducible T-cell costimulator (ICOS) expression, and PELI1 mRNA expression was negatively associated with ICOS expression on human CD4+ T cells. Mechanistically, increased ICOS expression on Peli1-KO CD4+ T cells enhanced the activation of PI3K-AKT signaling and thus suppressed the expression of Klf2, a transcription factor that inhibits Tfh differentiation. Therefore, reconstitution of Klf2 abolished the differences in Tfh differentiation and germinal center reaction between WT and Peli1-KO cells. As a consequence, Peli1-deficient CD4+ T cells promoted lupus-like autoimmunity but protected against H1N1 influenza virus infection in mouse models. Collectively, our findings established Peli1 as a critical negative regulator of Tfh differentiation and indicated that targeting Peli1 may have beneficial therapeutic effects in Tfh-related autoimmunity or infectious diseases.

Obesity is associated with metabolic disorders and chronic inflammation. However, the obesity-associated metabolic contribution to inflammatory induction remains elusive. Here, we show that, compared with lean mice, CD4 + T cells from obese mice exhibit elevated basal levels of fatty acid b-oxidation (FAO), which promote T cell glycolysis and thus hyperactivation, leading to enhanced induction of inflammation. Mechanistically, the FAO rate-limiting enzyme carnitine palmitoyltransferase 1a (Cpt1a) stabilizes the mitochondrial E3 ubiquitin ligase Goliath, which mediates deubiquitination of calcineurin and thus enhances activation of NF-AT signaling, thereby promoting glycolysis and hyperactivation of CD4 + T cells in obesity. We also report the specific GOLIATH inhibitor DC-Gonib32, which blocks this FAO-glycolysis metabolic axis in CD4 + T cells of obese mice and reduces the induction of inflammation. Overall, these findings establish a role of a Goliath-bridged FAO-glycolysis axis in mediating CD4 + T cell hyperactivation and thus inflammation in obese mice.

DNA accumulation is associated with the development of autoimmune inflammatory diseases. However, the pathological role and underlying mechanism of cytoplasmic DNA accumulation in CD4 + T cells has not been well established. Here, we show that Trex1 deficiency-induced endogenous DNA accumulation in CD4 + T cells greatly promoted their induction of autoimmune inflammation in a lupus-like mouse model. Mechanistically, the accumulated DNA in CD4 + T cells was sensed by KU complex, then triggered the activation of DNA-PKcs and ZAK and further facilitated the activation of AKT, which exacerbated glycolysis, thereby promoting the inflammatory responses. Accordingly, blocking DNA sensing pathway in CD4 + T cells by genetic knockout of Zak or using our newly developed ZAK inhibitor iZAK2 attenuated all pathogenic characteristics in a lupus-like inflammation mouse model induced with Trex1-deficient CD4 + T cells. Overall, our study demonstrated a causal link between DNA-sensing and metabolic reprogramming in CD4 + T cells for inflammatory induction and suggested inhibition of DNA sensing pathway may be a potential therapy for the treatment of inflammatory diseases.