Ubiquitin E3 ligase SPOP is a host negative regulator of enterovirus 71-encoded 2A protease.

IMPORTANCE: EV71 poses a significant health threat to children aged 5 and below. The process of EV71 infection and replication is predominantly influenced by ubiquitination modifications. Our previous findings indicate that EV71 prompts the activation of host deubiquitinating enzymes, thereby impeding the host interferon signaling pathway as a means of evading the immune response. Nevertheless, the precise mechanisms by which the host employs ubiquitination modifications to hinder EV71 infection remain unclear. The present study demonstrated that the nonstructural protein 2Apro, which is encoded by EV71, exhibits ubiquitination and degradation mediated by the host E3 ubiquitin ligase SPOP. In addition, it is the first report, to our knowledge, that SPOP is involved in the host antiviral response.

[Imbalance of lymphoid cells in peripheral blood maintains the immunosuppression and promotes the development of lung adenocarcinoma].

Objectives Objectives To investigate how the imbalance of innate lymphoid cells (ILCs)in the peripheral blood of patients with lung adenocarcinoma affects the balance of downstream mononuclear macrophages and T helper (Th) cells, and to identify the impact of the imbalance of ILCs on the immune status and prognosis of lung adenocarcinoma. Methods The peripheral blood of 20 patients with lung adenocarcinoma and normal controls were collected. The percentage of ILCs, mononuclear macrophages and T lymphocyte in peripheral blood were analyzed by flow cytometry. The characteristic cytokine secretion levels of various types of immune cells in peripheral blood were detected by real-time fluorescence quantitative PCR. Results Compared with the normal controls, the proportion of M2 mononuclear macrophages, ILC1 and ILC2 in patients with lung adenocarcinoma was up-regulated, while the proportion of M1 mononuclear macrophages, CD4+ T and CD8+ T was down-regulated. The mRNA expression of related cytokines of M1 mononuclear macrophages and ILC1 were decreased; while the mRNA expression of related cytokines of M2 mononuclear macrophages and ILC2 were increased. Along with the decreased CD4+T cells-associated cytokine T-bet mRNA expression, and the increased GATA3 mRNA expression. Moreover, the expression of PD-1 in CD8+ T cells was also up-regulated. Conclusion The imbalance of ILCs in peripheral blood of patients with lung adenocarcinoma promotes the imbalance of mononuclear macrophages and Th cells, which altogether maintains the immunosuppression in patients with lung adenocarcinoma, and promotes the development of lung adenocarcinoma.

Vitamin C promotes ACE2 degradation and protects against SARS-CoV-2 infection.

ACE2 is a major receptor for cellular entry of SARS-CoV-2. Despite advances in targeting ACE2 to inhibit SARS-CoV-2 binding, strategies to flexibly and sufficiently reduce ACE2 levels for the prevention of SARS-CoV-2 infection have not been explored. Here, we reveal vitamin C (VitC) administration as a potent strategy to prevent SARS-CoV-2 infection. VitC reduces ACE2 protein levels in a dose-dependent manner, while even a partial reduction in ACE2 levels can greatly inhibit SARS-CoV-2 infection. Further studies reveal that USP50 is a crucial regulator of ACE2 levels. VitC blocks the USP50-ACE2 interaction, thus promoting K48-linked polyubiquitination of ACE2 at Lys788 and subsequent degradation of ACE2 without affecting its transcriptional expression. Importantly, VitC administration reduces host ACE2 levels and greatly blocks SARS-CoV-2 infection in mice. This study reveals that ACE2 protein levels are down-regulated by an essential nutrient, VitC, thereby enhancing protection against infection of SARS-CoV-2 and its variants.

Methotrexate and Triptolide regulate Notch signaling pathway by targeting the Nedd4-Numb axis.

Methotrexate (MTX) is used to treat rheumatoid arthritis, acute leukemia, and psoriasis. MTX can cause certain side effects, such as myelosuppression, while the exact mechanism of myelosuppression caused by MTX is unknown. Notch signaling pathway has been considered to be essential to regulate hematopoietic stem cell (HSC) regeneration and homeostasis, thus contributing to bone marrow hematopoiesis. However, whether MTX affects Notch signaling remains unexplored. Here, our study provides evidence that MTX strongly suppresses the Notch signaling pathway. We found that MTX inhibited the interaction between Nedd4 with Numb, thus restricting K48-linked polyubiquitination of Numb and stabilizing Numb proteins. This in turn inhibited the Notch signaling pathway by reducing Notch1 protein levels. Interestingly, we found that a monomeric drug, Triptolide, is capable of alleviating the inhibitory effect of MTX on Notch signaling pathway. This study promotes our understanding of MTX-mediated regulation of Notch signaling and could provide ideas to alleviate MTX-induced myelosuppression.

Ubiquitin-specific protease 24 promotes EV71 infection by restricting K63-linked polyubiquitination of TBK1.

TANK-binding kinase 1 (TBK1) is an essential protein kinase for activation of interferon regulatory factor 3 (IRF3) and induction of the type I interferons (IFN-I). Although the biochemical regulation of TBK1 activation has been studied, little is known about how enterovirus 71 (EV71) employs the deubiquitinases (DUBs) to regulate TBK1 activation for viral immune evasion. Here, we found that EV71 infection upregulated the expression of ubiquitin-specific protease 24 (USP24). Further studies revealed that USP24 physically interacted with TBK1, and can reduce K63-linked polyubiquitination of TBK1. Knockdown of USP24 upregulated TBK1 K63-linked polyubiquitination, promoted the phosphorylation and nuclear translocation of IRF3, and in turn improved IFN-I production during EV71 infection. As a consequence, USP24 knockdown dramatically inhibited EV71 infection. This study revealed USP24 as a novel regulator of TBK1 activation, which promotes the understanding of immune evasion mechanisms of EV71 and could provide a potential strategy for treatment of EV71 infection.

LATS1 is a central signal transmitter for achieving full type-I interferon activity.

Interferons (IFNs) have broad-spectrum antiviral activity to resist virus epidemic. However, IFN antiviral efficacy needs to be greatly improved. Here, we reveal that LATS1 is a vital signal transmitter governing full type-I IFN (IFN-I) signaling activity. LATS1 constitutively binds with the IFN-I receptor IFNAR2 and is rapidly tyro-phosphorylated by Tyk2 upon IFN-I engagement. Tyro-phosphorylation of LATS1 promotes LATS1 activation and YAP degradation, thereby promoting IFN-mediated antiproliferation activity. Moreover, activated LATS1 translocates into the nucleus and induces CDK8-Ser62 phosphorylation, which in turn phosphorylates STAT1 at Ser727 and induces full IFN-I antiviral activity. LATS1 deficiency restricts in vivo IFN-I signaling and attenuates host antiviral immune response. Our study identifies IFN-I as a previously unidentified extracellular diffusible ligand signal for activation of the Hippo core LATS1 pathway and reveals Tyk2-LATS1-CDK8 as a complete signaling cascade controlling full IFN-I activity.