Hippo Pathway Counter-Regulates Innate Immunity in Hepatitis B Virus Infection

Oncolytic Newcastle disease virus induced degradation of YAP through E3 ubiquitin ligase PRKN to exacerbate ferroptosis in tumor cells

Ferroptosis, a form of programmed cell death characterized by iron-dependent lipid peroxidation, has recently gained considerable attention in the field of cancer therapy. There is significant crosstalk between ferroptosis and several classical signaling pathways, such as the Hippo pathway, which suppresses abnormal growth and is frequently aberrant in tumor tissues. Yes-associated protein 1 (YAP), the core effector molecule of the Hippo pathway, is abnormally expressed and activated in a variety of malignant tumor tissues. We previously proved that the oncolytic Newcastle disease virus (NDV) activated ferroptosis to kill tumor cells. NDV has been used in tumor therapy; however, its oncolytic mechanism is not completely understood. In this study, we demonstrated that NDV exacerbated ferroptosis in tumor cells by inducing ubiquitin-mediated degradation of YAP at Lys90 through E3 ubiquitin ligase parkin (PRKN). Blocking YAP degradation suppressed NDV-induced ferroptosis by suppressing the expression of Zrt/Irt-like protein 14 (ZIP14), a metal ion transporter that regulates iron uptake. These findings demonstrate that NDV exacerbated ferroptosis in tumor cells by inducing YAP degradation. Our study provides new insights into the mechanism of NDV-induced ferroptosis and highlights the critical role that oncolytic viruses play in the treatment of drug-resistant cancers.IMPORTANCEThe oncolytic Newcastle disease virus (NDV) is being developed for use in cancer treatment; however, its oncolytic mechanism is still not completely understood. The Hippo pathway, which is a tumor suppressor pathway, is frequently dysregulated in tumor tissues due to aberrant yes-associated protein 1 (YAP) activation. In this study, we have demonstrated that NDV degrades YAP to induce ferroptosis and promote virus replication in tumor cells. Notably, NDV was found to induce ubiquitin-mediated degradation of YAP at Lys90 through E3 ubiquitin ligase parkin (PRKN). Our study reveals a new mechanism by which NDV induces ferroptosis and provides new insights into NDV as an oncolytic agent for cancer treatment.

Neutrophil extracellular traps mediate cardiomyocyte ferroptosis via the Hippo-Yap pathway to exacerbate doxorubicin-induced cardiotoxicity

Doxorubicin-induced cardiotoxicity (DIC), which is a cardiovascular complication, has become the foremost determinant of decreased quality of life and mortality among survivors of malignant tumors, in addition to recurrence and metastasis. The limited ability to accurately predict the occurrence and severity of doxorubicin-induced injury has greatly hindered the prevention of DIC, but reducing the dose to mitigate side effects may compromise the effective treatment of primary malignancies. This has posed a longstanding clinical challenge for oncologists and cardiologists. Ferroptosis in cardiomyocytes has been shown to be a pivotal mechanism underlying cardiac dysfunction in DIC. Ferroptosis is influenced by multiple factors. The innate immune response, as exemplified by neutrophil extracellular traps (NETs), may play a significant role in the regulation of ferroptosis. Therefore, the objective of this study was to investigate the involvement of NETs in doxorubicin-induced cardiomyocyte ferroptosis and elucidate their regulatory role. This study confirmed the presence of NETs in DIC in vivo. Furthermore, we demonstrated that depleting neutrophils effectively reduced the occurrence of doxorubicin-induced ferroptosis and myocardial injury in DIC. Additionally, our findings showed the pivotal role of high mobility group box 1 (HMGB1) as a critical molecule implicated in DIC and emphasized its involvement in the modulation of ferroptosis subsequent to NETs inhibition. Mechanistically, we obtained preliminary evidence suggesting that doxorubicin-induced NETs could modulate yes-associated protein (YAP) activity by releasing HMGB1, which subsequently bound to toll like receptor 4 (TLR4) on the cardiomyocyte membrane, thereby influencing cardiomyocyte ferroptosis in vitro. Our findings suggest that doxorubicin-induced NETs modulate cardiomyocyte ferroptosis via the HMGB1/TLR4/YAP axis, thereby contributing to myocardial injury. This study offers a novel approach for preventing and alleviating DIC by targeting alterations in the immune microenvironment.

Tg1.4HBV-s-rec mice, a crossbred hepatitis B virus-transgenic model, develop mild hepatitis

Hepatitis B virus (HBV)-transgenic mice exhibit competent innate immunity and are therefore an ideal model for considering intrinsic or cell-based mechanisms in HBV pathophysiology. A highly replicative model that has been little used, let alone characterized, is the Tg1.4HBV-s-rec strain derived from cross breeding of HBV-transgenic mouse models that either accumulate (Alb/HBs, Tg[Alb1-HBV]Bri44) or lack (Tg1.4HBV-s-mut) the hepatitis B surface antigen (HBsAg). Tg1.4HBV-s-rec hepatocytes secreted HBsAg, Hepatitis B extracellular antigen (HBeAg) and produced HBV virions. Transmission electron microscopy visualised viral particles (Tg1.4HBV-s-rec), nuclear capsid formations (Tg1.4HBV-s-mut and Tg1.4HBV-s-rec) and endoplasmic reticulum malformations (Alb/HBs). Viral replication in Tg1.4HBV-s-rec and Tg1.4HBV-s-mut differed in HBsAg expression and interestingly in the distribution of HBV core antigen (HBcAg) and HBV × protein. While in Tg1.4HBV-s-mut hepatocytes, the HBcAg was located in the cytoplasm, in Tg1.4HBV-s-rec hepatocytes, the HBcAg appeared in the nuclei, suggesting a more productive replication. Finally, Tg1.4HBV-s-rec mice showed symptoms of mild hepatitis, with reduced liver function and elevated serum transaminases, which appeared to be related to natural killer T cell activation. In conclusion, the study of Alb/HBs, Tg1.4HBV-s-mut and their F1 progeny provides a powerful tool to elucidate HBV pathophysiology, especially in the early HBeAg-positive phases of chronic infection and chronic hepatitis.

Nuclear translocation of YAP drives BMI-associated hepatocarcinogenesis in hepatitis B virus infection

BACKGROUND AND AIMS

Hepatitis B virus (HBV) infection is a major cause of hepatocellular carcinoma (HCC) development and progression. The aim of this study was to mechanistically investigate the involvement of Hippo signalling in HBV surface antigen (HBsAg)-dependent neoplastic transformation.

METHODS

Liver tissue and hepatocytes from HBsAg-transgenic mice were examined for the Hippo cascade and proliferative events. Functional experiments in mouse hepatoma cells included knockdown, overexpression, luciferase reporter assays and chromatin immunoprecipitation. Results were validated in HBV-related HCC biopsies.

RESULTS

Hepatic expression signatures in HBsAg-transgenic mice correlated with YAP responses, cell cycle control, DNA damage and spindle events. Polyploidy and aneuploidy occurred in HBsAg-transgenic hepatocytes. Suppression and inactivation of MST1/2 led to the loss of YAP phosphorylation and the induction of BMI1 expression in vivo and in vitro. Increased BMI1 directly mediated cell proliferation associated with decreased level of p16INK4a , p19ARF , p53 and Caspase 3 as well as increased Cyclin D1 and γ-H2AX expression. Chromatin immunoprecipitation and the analysis of mutated binding sites in dual-luciferase reporter assays confirmed that the YAP/TEAD4 transcription factor complex bound and activated the Bmi1 promoter. In chronic hepatitis B patients, paired liver biopsies of non-tumour and tumour tissue indicated a correlation between YAP expression and the abundance of BMI1. In a proof-of-concept, treatment of HBsAg-transgenic mice with YAP inhibitor verteporfin directly suppressed the BMI1-related cell cycle.

CONCLUSION

HBV-associated proliferative HCC might be related to the HBsAg-YAP-BMI1 axis and offer a potential target for the development of new therapeutic approaches.

Poly(I:C) Induces Distinct Liver Cell Type-Specific Responses in Hepatitis B Virus-Transgenic Mice In Vitro, but Fails to Induce These Signals In Vivo

Immunopathology in hepatitis B virus (HBV) infection is driven by innate and adaptive immunity. Whether the hepatitis B surface antigen (HBsAg) affects hepatic antiviral signalling was investigated in HBV-transgenic mouse models that either accumulate (Alb/HBs, Tg[Alb1HBV]Bri44), lack (Tg1.4HBV-s-mut3) or secrete (Tg1.4HBV-s-rec (F1, Tg1.4HBV-s-mut × Alb/HBs) the HBsAg. Herein, the responsiveness of TLR3 and RIG-I in primary parenchymal and non-parenchymal liver cells was determined in vitro and in vivo. Cell type-specific and mouse strain-dependent interferon, cytokine and chemokine expression were observed by LEGENDplex™ and validated by quantitative PCR. In vitro, the hepatocytes, liver sinusoidal endothelial cells and Kupffer cells of Tg1.4HBV-s-rec mice showed poly(I:C) susceptibilities similar to the wild-type controls, while in the remaining leucocyte fraction the interferon, cytokine and chemokine induction was reduced. On the contrary, poly(I:C)-injected 1.4TgHBV-s-rec mice showed suppressed interferon, cytokine and chemokine levels in hepatocytes but increased levels in the leucocyte fraction. Thus, we concluded that liver cells of Tg1.4HBV-s-rec mice, which produce HBV particles and release the HBsAg, responded to exogenous TLR3/RIG-I stimuli in vitro but exhibited a tolerogenic environment in vivo.

Lnc-AIFM2-1 promotes HBV immune escape by acting as a ceRNA for miR-330-3p to regulate CD244 expression

Chronic hepatitis B (CHB) virus infection is a major risk factor for cirrhosis and hepatocellular carcinoma (HCC). Hepatitis B virus (HBV) immune escape is regulated by the exhaustion of virus-specific CD8+ T cells, which is associated with abnormal expression of negative regulatory molecule CD244. However, the underlying mechanisms are unclear. To investigate the important roles of non-coding RNAs play in CD244 regulating HBV immune escape, we performed microarray analysis to determine the differential expression profiles of long non-coding RNAs (lncRNAs), microRNAs (miRNAs), and mRNAs in patients with CHB and patients with spontaneous clearance of HBV. Competing endogenous RNA (ceRNA) was analyzed by bioinformatics methods and confirmed by the dual-luciferase reporter assay. Furthermore, gene silencing and overexpression experiments were used to further identify the roles of lncRNA and miRNA in HBV immune escape through CD244 regulation. The results showed that the expression of CD244 on the surface of CD8+ T cells was significantly increased in CHB patients and in the co-culture system of T cells and HBV-infected HepAD38 cells, which was accompanied by the reduction of miR-330-3p and the elevation of lnc-AIFM2-1. The down-regulated miR-330-3p induced the apoptosis of T cells by lifting the inhibition of CD244, which was reversed by miR-330-3p mimic or CD244-siRNA. Lnc-AIFM2-1 promotes the accumulation of CD244, which is mediated by decreased miR-330-3p, and then reduced the clearance ability of CD8+ T cells to HBV through regulated CD244 expression. And the injury in the ability of CD8+ T cells to clear HBV can be reversed by lnc-AIFM2-1-siRNA, miR-330-3p mimic, or CD244-siRNA. Collectively, our findings indicate that lnc-AIFM2-1 on CD244 by acting as a ceRNA of miR-330-3p contributes to HBV immune escape, which may provide novel insights into the roles of interaction networks among lncRNA, miRNA, and mRNA in HBV immune escape, highlighting potential applications of lnc-AIFM2-1 and CD244 for diagnosis and treatment in CHB.

Inactivation of Yes-Associated Protein Mediates Trophoblast Dysfunction: A New Mechanism of Pregnancy Loss Associated with Anti-Phospholipid Antibodies?

Pregnancy morbidity induced by anti-phospholipid antibodies (aPL+/PM+) is mainly thought to arise from placental abnormalities. We attempted to investigate the effect of aPL on the activity of Yes-associated protein (YAP) in the trophoblast and how YAP regulated human trophoblasts function. Thus, HTR-8 cells were treated with IgG purified from aPL+/PM+ women or normal controls. We found that aPL+/PM+ IgG impacted YAP activity via abrogating YAP expression. Further investigation of the anti-β2GPI-IgG/β2GPI complex showed an inhibition of nuclear YAP level and translocation in a dose-dependent manner, which might be rescued by progesterone in HTR-8 cells. YAP overexpression or knockdown HTR-8 cells were established for the evaluation of cell function and related gene expression in vitro. Loss of YAP arrested cell cycles in the G2/M phase, accelerated cell apoptosis by increasing the ratio of Bax/Bcl2, and disrupted MMP2/9-mediated cell migration and angiogenesis tube formation by VEGF. These findings support a new mechanism of PM associated with aPL through which YAP inactivation induced by aPL perturbs the trophoblast cell cycle, apoptosis, migration, and angiogenesis, finally developing into pregnancy failure.

TEAD4 as an Oncogene and a Mitochondrial Modulator

TEAD4 (TEA Domain Transcription Factor 4) is well recognized as the DNA-anchor protein of YAP transcription complex, which is modulated by Hippo, a highly conserved pathway in Metazoa that controls organ size through regulating cell proliferation and apoptosis. To acquire full transcriptional activity, TEAD4 requires co-activator, YAP (Yes-associated protein) or its homolog TAZ (transcriptional coactivator with PDZ-binding motif) the signaling hub that relays the extracellular stimuli to the transcription of target genes. Growing evidence suggests that TEAD4 also exerts its function in a YAP-independent manner through other signal pathways. Although TEAD4 plays an essential role in determining that differentiation fate of the blastocyst, it also promotes tumorigenesis by enhancing metastasis, cancer stemness, and drug resistance. Upregulation of TEAD4 has been reported in several cancers, including colon cancer, gastric cancer, breast cancer, and prostate cancer and serves as a valuable prognostic marker. Recent studies show that TEAD4, but not other members of the TEAD family, engages in regulating mitochondrial dynamics and cell metabolism by modulating the expression of mitochondrial- and nuclear-encoded electron transport chain genes. TEAD4’s functions including oncogenic activities are tightly controlled by its subcellular localization. As a predominantly nuclear protein, its cytoplasmic translocation is triggered by several signals, such as osmotic stress, cell confluency, and arginine availability. Intriguingly, TEAD4 is also localized in mitochondria, although the translocation mechanism remains unclear. In this report, we describe the current understanding of TEAD4 as an oncogene, epigenetic regulator and mitochondrial modulator. The contributing mechanisms will be discussed.

Phosphoproteomics Unravel HBV Triggered Rewiring of Host Phosphosignaling Events

Hepatitis B virus (HBV) infection persists as a major global health problem despite the availability of HBV vaccines for disease prevention. However, vaccination rates remains low in some regions of the world, driving the need for novel strategies to minimise infections and prevent disease progression. Thus, understanding of perturbed molecular signaling events during early phases of HBV infection is required. Phosphosignaling is known to be involved in the HBV infection processes, yet systems-level changes in phosphosignaling pathways in the host during infection remain unclear. To this end, we performed phosphoproteome profiling on HBV-infected HepG2-NTCP cells. Our results showed that HBV infection drastically altered the host phosphoproteome and its associated proteins, including kinases. Computational analysis of this phosphoproteome revealed dysregulation of the pathways involved in immune responses, cell cycle processes, and RNA processing during HBV infection. Kinase Substrate Enrichment Analysis (KSEA) identified the dysregulated activities of important kinases, including those from CMGC (CDK, MAPK, GSK, and CLK), AGC (protein kinase A, G, and C), and TK (Tyrosine Kinase) families. Of note, the inhibition of CLKs significantly reduced HBV infection in HepG2-NTCP cells. In all, our study unravelled the aberrated phosphosignaling pathways and the associated kinases, presenting potential entry points for developing novel therapeutic strategies for HBV treatment.

TLR2, as a Pathogen Recognition Receptor, Plays Critical Roles in Hepatitis B Outcome

The immune system of active and inactive chronic hepatitis B, as prolonged forms of hepatitis B, is unable to eradicate hepatitis B virus (HBV) from the infected hepatocytes completely. Toll-like receptors (TLRs) play key roles in the viral recognition and promotion of appropriate immune responses. The molecules also participate in the alteration of the target cell functions and transformation. TLR2 is the unique molecule that makes either homodimer or heterodimer with TLR1 and 6 and shows variable roles against viral infections. Therefore, it has been hypothesized that TLR2 may participate in both immune response against HBV and induction of the virus-related hepatic complications. The studies confirm the hypothesis and revealed that TLR2 is not only one of the main molecules altering the course of HBV infection, but also plays key roles in induction of hepatocellular carcinoma (HCC) and liver cirrhosis. However, recent studies demonstrated that the molecule can fight against HCC and liver cirrhosis. Collectively, it appears that nutrition habits, TLR2 gene polymorphisms, gut microbiome, HBV antigens, and activation of other receptors may play key roles in the determination of TLR2 functions.

The regulatory networks of the Hippo signaling pathway in cancer development

The Hippo signaling pathway is a relatively young tumor-related signaling pathway. Although it was discovered lately, research on it developed rapidly. The Hippo signaling pathway is closely relevant to the occurrence and development of tumors and the maintenance of organ size and other biological processes. This manuscript focuses on YAP, the core molecule of the Hippo signaling pathway, and discussion the upstream and downstream regulatory networks of the Hippo signaling pathway during tumorigenesis and development. It also summarizes the relevant drugs involved in this signaling pathway, which may be helpful to the development of targeted drugs for cancer therapy.