TRIM6 facilitates SARS-CoV-2 proliferation by catalyzing the K29-typed ubiquitination of NP to enhance the ability to bind viral genomes.

The Nucleocapsid Protein (NP) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is not only the core structural protein required for viral packaging, but also participates in the regulation of viral replication, and its post-translational modifications such as phosphorylation have been shown to be an important strategy for regulating virus proliferation. Our previous work identified NP could be ubiquitinated, as confirmed by two independent studies. But the function of NP ubiquitination is currently unknown. In this study, we first pinpointed TRIM6 as the E3 ubiquitin ligase responsible for NP ubiquitination, binding to NP's CTD via its RING and B-box-CCD domains. TRIM6 promotes the K29-typed polyubiquitination of NP at K102, K347, and K361 residues, increasing its binding to viral genomic RNA. Consistently, functional experiments such as the use of the reverse genetic tool trVLP model and gene knockout of TRIM6 further confirmed that blocking the ubiquitination of NP by TRIM6 significantly inhibited the proliferation of SARS-CoV-2. Notably, the NP of coronavirus is relatively conserved, and the NP of SARS-CoV can also be ubiquitinated by TRIM6, indicating that NP could be a broad-spectrum anti-coronavirus target. These findings shed light on the intricate interaction between SARS-CoV-2 and the host, potentially opening new opportunities for COVID-19 therapeutic development.

The E3 ligase TRIM22 restricts SARS-CoV-2 replication by promoting proteasomal degradation of NSP8.

Replication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genome is mediated by a complex of non-structural proteins (NSPs), of which NSP7 and NSP8 serve as subunits and play a key role in promoting the activity of RNA-dependent RNA polymerase (RdRp) of NSP12. However, the stability of subunits of the RdRp complex has rarely been reported. Here, we found that NSP8 was degraded by the proteasome in host cells, and identified tripartite motif containing 22 (TRIM22) as its E3 ligase. The interferon (IFN) signaling pathway was activated upon viral invasion into host cells, and TRIM22 expression increased. TRIM22 interacted with NSP8 and ubiquitinated it at Lys97 via K48-type ubiquitination. TRIM22 overexpression significantly reduced viral RNA and protein levels. Knockdown of TRIM22 enhanced viral replication. This study provides a new explanation for treating patients suffering from SARS-CoV-2 with IFNs and new possibilities for drug development targeting the interaction between NSP8 and TRIM22.IMPORTANCENon-structural proteins (NSPs) play a crucial role in the replication of severe acute respiratory syndrome coronavirus 2, facilitating virus amplification and propagation. In this study, we conducted a comprehensive investigation into the stability of all subunits comprising the RNA-dependent RNA polymerase complex. Notably, our results reveal for the first time that NSP8 is a relatively unstable protein, which is found to be readily recognized and degraded by the proteasome. This degradation process is mediated by the host E3 ligase tripartite motif containing 22 (TRIM22), which is also a member of the interferon stimulated gene (ISG) family. Our study elucidates a novel mechanism of antiviral effect of TRIM22, which utilizes its own E3 ubiquitin ligase activity to hinder viral replication by inducing ubiquitination and subsequent degradation of NSP8. These findings provide new ideas for the development of novel therapeutic strategies. In addition, the conserved property of NSP8 raises the possibility of developing broad antiviral drugs targeting the TRIM22-NSP8 interaction.

Retracted: Cucurbitacin B Inhibits the Hippo-YAP Signaling Pathway and Exerts Anticancer Activity in Colorectal Cancer Cells.

This publication has been retracted by the Editor due to concerns regarding the originality of the figure images. Reference: Yanting Chai, Ke Xiang, Yezi Wu, Te Zhang, Ying Liu, Xuewen Liu, Weiguo Zhen, Yuan Si. Cucurbitacin B Inhibits the Hippo-YAP Signaling Pathway and Exerts Anticancer Activity in Colorectal Cancer Cells. Med Sci Monit, 2018; 24: LBR9251-9258. DOI: 10.12659/MSM.911594.

Multiomics approach reveals the ubiquitination-specific processes hijacked by SARS-CoV-2.

The Coronavirus Disease 2019 (COVID-19) caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is a global pandemic that seriously threatens health and socioeconomic development, but the existed antiviral drugs and vaccines still cannot yet halt the spread of the epidemic. Therefore, a comprehensive and profound understanding of the pathogenesis of SARS-CoV-2 is urgently needed to explore effective therapeutic targets. Here, we conducted a multiomics study of SARS-CoV-2-infected lung epithelial cells, including transcriptomic, proteomic, and ubiquitinomic. Multiomics analysis showed that SARS-CoV-2-infected lung epithelial cells activated strong innate immune response, including interferon and inflammatory responses. Ubiquitinomic further reveals the underlying mechanism of SARS-CoV-2 disrupting the host innate immune response. In addition, SARS-CoV-2 proteins were found to be ubiquitinated during infection despite the fact that SARS-CoV-2 itself didn't code any E3 ligase, and that ubiquitination at three sites on the Spike protein could significantly enhance viral infection. Further screening of the E3 ubiquitin ligases and deubiquitinating enzymes (DUBs) library revealed four E3 ligases influencing SARS-CoV-2 infection, thus providing several new antiviral targets. This multiomics combined with high-throughput screening study reveals that SARS-CoV-2 not only modulates innate immunity, but also promotes viral infection, by hijacking ubiquitination-specific processes, highlighting potential antiviral and anti-inflammation targets.

Polyphyllin I activates AMPK to suppress the growth of non-small-cell lung cancer via induction of autophagy.

Polyphyllin I (PPI), a bioactive constituent extracted from the rhizomes of Paris polyphylla, is cytotoxic to several cancer types. This study was designed to explore whether PPI prevents non-small-cell lung cancer (NSCLC) growth and to investigate the molecular mechanism. AMP-activated protein kinase (AMPK) has been implicated in the activation of autophagy in distinct tissues. In cultured human NSCLC cell lines, PPI induces autophagy by activating AMPK and then inhibiting mTOR signaling in a concentration-dependent manner. Furthermore, the activation of autophagy induced by PPI was reversed by the AMPK inhibitor compound C. Computational docking showed that PPI directly interacted with the allosteric drug and metabolite site of AMPK to stabilize its activation. Microscale thermophoresis and Drug Affinity Responsive Targeting Stability (DARTS) assay further confirmed the high affinity between PPI and AMPK. In vivo studies indicated that PPI suppressed the growth of NSCLC and increased the levels of LC3-II and phosphorylated AMPK in tumors isolated from a xenograft model of NSCLC in mice. Moreover, PPI exhibited favorable pharmacokinetics in rats. In summary, PPI conclusively acts as a direct AMPK activator to induce cell autophagy which inhibits the growth of NSCLC cells. In the future, PPI therapy should be applied to treat patients with NSCLC.

Cucurbitacin B induces inhibitory effects via the CIP2A/PP2A/C-KIT signaling axis in t(8;21) acute myeloid leukemia.

Acute myeloid leukemia (AML) is the most common subtype of hematological malignancy in humans, and its incidence increases with age. The treatment of AML still faces challenges. Therefore, there is an urgent need to develop more effective targeted therapies. The receptor tyrosine kinase C-KIT confers critical proliferative signals to AML. Cancerous inhibitor of protein phosphatase 2A (CIP2A) is an endogenous inhibitor of protein phosphatase 2A (PP2A), which promotes the growth and transformation of various solid tumors. These actions make CIP2A a promising target for tumor treatment. Here, we reported the effects and underlying mechanisms of a natural compound, cucurbitacin B (CuB), on AML. We reported that CuB suppressed growth and induced apoptosis in AML cells. The inhibition of growth and activation of apoptosis were mediated through CuB-induced downregulation of the CIP2A/PP2A/C-KIT signal pathway. Furthermore, CuB inactivated the JAK2 and STAT3 molecules downstream of C-KIT via the downregulation of CIP2A. These results advance our understanding of CuB-induced growth inhibition and apoptosis and support further investigation of CuB as a CIP2A inhibitor for AML therapies.

Cucurbitacin B Inhibits the Hippo-YAP Signaling Pathway and Exerts Anticancer Activity in Colorectal Cancer Cells.

BACKGROUND Colorectal carcinoma (CRC) is one of the most frequently diagnosed malignancies. Cucurbitacin B (CuB) is a natural compound isolated from herbs and shows anticancer activity in several cancers. MATERIAL AND METHODS Here, we analyzed the effects of different CuB concentrations on the proliferative and invasive behaviors of CRC cells using MTT, clonogenic assay, Transwell invasion, and wound healing assays. Flow cytometry was performed to measure the apoptotic effects of CuB on CRC cells. Western blot and real-time PCR were used to investigate the expression of apoptosis and Hippo-YAP signaling pathway proteins. RESULTS CuB inhibited the proliferation and invasion of CRC cells while promoting apoptosis. In addition, the Western blot and real-time PCR results indicated that CuB suppressed YAP expression and its downstream target genes Cyr 61 and c-Myc in CRC cells. To assess the underlying mechanism, we investigated the upstream regulating factor LATS1, and the results revealed that CuB upregulated LATS1 expression in CRC cells. CONCLUSIONS In conclusion, our findings uncovered a novel therapeutic mechanism of CuB and suggest that there is therapeutic potential and feasibility in developing novel YAP inhibitors for cancer treatment.

Polyphyllin I inhibits growth and invasion of cisplatin-resistant gastric cancer cells by partially inhibiting CIP2A/PP2A/Akt signaling axis.

The aberrant expression of cancerous inhibitor of protein phosphatase 2A (CIP2A) indicates poor prognosis and promotes EMT and metastasis. EMT, a crucial cellular process that occurs during cancer progression and metastasis, has been reported to promote drug resistance in several previous studies. Consequently, ongoing research has been focused on exploring therapeutic options for preventing EMT to delay or reverse drug resistance. Polyphyllin I (PPI) is a natural component extracted from Paris polyphylla that displays anti-cancer properties. In the present study, we investigated whether PPI can be used in the cisplatin (DDP)-resistant human gastric cancer cell line SGC7901/DDP. The results demonstrated that PPI treatment significantly inhibited cell proliferation, invasion and EMT. TGF-ß1 is known to promote EMT-induced metastasis in numerous tumor types. PPI inhibited the invasion of TGFß1-induced SGC7901/DDP cells in vitro. PPI also increased the mRNA and protein expression levels of E-cadherin but decreased the expression levels of vimentin. Further examination of the mechanism revealed that the CIP2A/PP2A/Akt pathway is partially involved in this regulation of EMT-related biomarkers and invasion. Furthermore, xenograft tests also confirmed the antitumor effects of PPI in vivo. We propose that PPI could be developed as a candidate drug for treating cancer invasion and migration.