Hepatitis B virus X protein sensitizes cells to starvation-induced autophagy via up-regulation of beclin 1 expression

Autophagy machinery as exploited by viruses

Viruses adapt and modulate cellular pathways to allow their replication in host cells. The catabolic pathway of macroautophagy, for simplicity referred to as autophagy, is no exception. In this review, we discuss anti-viral functions of both autophagy and select components of the autophagy machinery, and how viruses have evaded them. Some viruses use the membrane remodeling ability of the autophagy machinery to build their replication compartments in the cytosol or efficiently egress from cells in a non-lytic fashion. Some of the autophagy machinery components and their remodeled membranes can even be found in viral particles as envelopes or single membranes around virus packages that protect them during spreading and transmission. Therefore, studies on autophagy regulation by viral infections can reveal functions of the autophagy machinery beyond lysosomal degradation of cytosolic constituents. Furthermore, they can also pinpoint molecular interactions with which the autophagy machinery can most efficiently be manipulated, and this may be relevant to develop effective disease treatments based on autophagy modulation.

ALR inhibits HBV replication and autophagosome formation by ameliorating HBV-induced ROS production in hepatic cells

HBV has a small genome and thrives in the infected hepatocytes by hijacking the cellular machinery and cellular pathways. HBV induces incomplete autophagy for its replication and survival. This study showed that HBV replication induces Reactive oxygen species (ROS) production, which in turn augments the formation of autophagosomes. Augmenter of liver regeneration (ALR) is a sufhydryl oxidase and has an anti-oxidative property. We sought to determine the interplay between HBV and antioxidant protein ALR. We showed that HBV downregulated ALR expression in hepatic cells. There was increased ROS production in HBV-infected cells while ALR downregulated ROS levels and expression of NADPH oxidase NOX4. N-acetyl cysteine, a ROS scavenger, downregulated ROS level and autophagosome formation in HBV-expressing cells. ALR overexpression in HBV-expressing cells downregulated the expression of autophagy marker proteins while upregulated the expression of p-MTOR. ALR overexpression decreased the expression of HBx, HBsAg, and total HBV load. This study showed that HBx relieved ALR-mediated inhibition by upregulating the miR-181a expression in HBV-infected cells, which in turn downregulated ALR expression.

The Interplay Between Viral Infection and Cell Death: A Ping-Pong Effect

Programmed cell death (PCD) is a well-studied cellular mechanism that plays a critical role in immune responses, developmental processes, and the maintenance of tissue homeostasis. However, viruses have developed diverse strategies to bypass or manipulate the host apoptotic machinery to enhance their replication and survival. As a result, the interaction between PCD pathways and viruses has garnered increased interest, leading to many studies being published in recent years. This study aims to provide an overview of the current understanding of PCD pathways and their significance in viral infections. We will discuss various forms of cell death pathways, including apoptosis, autophagy, necroptosis, and pyroptosis, as well as their corresponding molecular mechanisms. In addition, we will show how viruses manipulate host PCD pathways to prevent or delay cell death or facilitate viral replication. This study emphasizes the importance of investigating the mechanisms by which viruses control the host's PCD machinery to gain insight into the evolutionary dynamics of host-pathogen interactions and to develop new approaches for predicting and managing viral threats. Overall, we aimed to highlight new research areas in PCD and viruses, including introduction of new targets for the development of new antiviral drugs to modulate the cellular apoptotic machinery and novel inhibitors of host cell death pathways.

Hepatitis B virus entry, assembly, and egress

SUMMARYHepatitis B virus (HBV) is an important human pathogen that chronically infects approximately 250 million people in the world, resulting in ~1 million deaths annually. This virus is a hepatotropic virus and can cause severe liver diseases including cirrhosis and hepatocellular carcinoma. The entry of HBV into hepatocytes is initiated by the interaction of its envelope proteins with its receptors. This is followed by the delivery of the viral nucleocapsid to the nucleus for the release of its genomic DNA and the transcription of viral RNAs. The assembly of the viral capsid particles may then take place in the nucleus or the cytoplasm and may involve cellular membranes. This is followed by the egress of the virus from infected cells. In recent years, significant research progresses had been made toward understanding the entry, the assembly, and the egress of HBV particles. In this review, we discuss the molecular pathways of these processes and compare them with those used by hepatitis delta virus and hepatitis C virus , two other hepatotropic viruses that are also enveloped. The understanding of these processes will help us to understand how HBV replicates and causes diseases, which will help to improve the treatments for HBV patients.

Autophagy and cancer therapy

Autophagy is an intracellular degradation process that sequesters cytoplasmic components in double-membrane vesicles known as autophagosomes, which are degraded upon fusion with lysosomes. This pathway maintains the integrity of proteins and organelles while providing energy and nutrients to cells, particularly under nutrient deprivation. Deregulation of autophagy can cause genomic instability, low protein quality, and DNA damage, all of which can contribute to cancer. Autophagy can also be overactivated in cancer cells to aid in cancer cell survival and drug resistance. Emerging evidence indicates that autophagy has functions beyond cargo degradation, including roles in tumor immunity and cancer stem cell survival. Additionally, autophagy can also influence the tumor microenvironment. This feature warrants further investigation of the role of autophagy in cancer, in which autophagy manipulation can improve cancer therapies, including cancer immunotherapy. This review discusses recent findings on the regulation of autophagy and its role in cancer therapy and drug resistance.

ANXA4 restricts HBV replication by inhibiting autophagic degradation of MCM2 in chronic hepatitis B

BACKGROUND

Hepatitis B virus (HBV) is an enveloped DNA virus that causes chronic hepatitis B (CHB) infection. Annexin, a Ca2+-activated protein, is widely expressed in various organs and tissues and has potential utility in disease diagnosis and treatment. However, the relationship between the annexin family and CHB remains unclear.

METHODS

Clinical samples from hepatitis patients and donors or healthy individuals were collected. Transcriptome sequencing in CHB liver tissues and HBV-infected cells were performed. HepG2.2.15 cells with the full-length HBV genome and HBV-infected HepG2-NTCP cell models were established. HBV-infected mouse model was constructed and adeno-associated virus was utilized.

RESULTS

ANXA4 expression was elevated during CHB infection. ANXA4 knockdown promoted HBV replication and aggravated liver injury, while ANXA4 overexpression alleviated that. Mechanistically, autophagy pathway was activated by ANXA4 deficiency, promoting autophagic degradation of minichromosome maintenance complex component 2 (MCM2). MCM2 inhibition activated HBV replication, while MCM2 overexpression attenuated ANXA4 deficiency-induced HBV replication and liver injury. Clinically, the expression of hepatitis B viral protein was negatively correlated with the ANXA4 levels, and CHB patients with high ANXA4 levels (> 8 ng/ml) showed higher sensitivity to interferon therapy.

CONCLUSIONS

ANXA4 functions as a protective factor during HBV infection. ANXA4 expression is elevated under HBV attack to restrict HBV replication by inhibiting autophagic degradation of MCM2, thereby alleviating liver injury and suppressing the CHB infection process. ANXA4 also enhances the sensitivity of CHB patients to interferon therapy. Therefore, ANXA4 is expected to be a new target for CHB treatment and prognostic evaluation.

Autophagy Gene BECN1 Intronic Variant rs9890617 Predisposes Individuals to Hepatitis B Virus Infection

Beclin 1 protein encoded by the BECN1 gene plays a critical role in the autophagy pathway which is utilized by the Hepatitis B virus (HBV) for its replication. HBV is known for the subversion of the host's autophagy process for its multiplication. The aim of this study was to determine the role of BECN1 intronic variants in HBV susceptibility. Intronic region variant rs9890617 was analyzed using Human splicing finder v3.1 and was found to alter splicing signals. A total of 712 individuals (494 HBV infected and 218 healthy controls) were recruited in the study and genotyped by applying Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP). Statistical analysis revealed that the mutant allele T of rs9890617 was significantly associated with the overall disease risk in the allelic model (OR 1.41; 95%CI 1.00-1.99, p = 0.04). On stratifying the data based on the different stages of HBV infection, the mutant genotype showed a significant association with the chronic group in allelic (OR 1.62; 95%CI 1.11-2.39, p = 0.01), dominant (OR 1.64; 95%CI 1.07-2.52, p = 0.02), and co-dominant (OR 1.55; 95%CI 1.00-2.40, p = 0.04) models. Overall, this is the first study regarding beclin 1 variant rs9890617 and we found a significant association of the mutant T allele with the genetic predisposition to HBV infection.

HBx promotes tumorigenicity through RRM2-mediated autophagy in hepatocellular carcinoma

BACKGROUND

Hepatitis B virus (HBV) infection can exacerbate liver disease progression through multiple mechanisms, eventually leading to hepatocellular carcinoma (HCC). HBV-encoded oncogene X protein (HBx), a key regulatory protein of HBV infection, serves as a positive regulator of hepatocarcinogenesis. The indispensability of the M2 subunit of ribonucleotide-diphosphate reductase (RRM2) lies in its role in facilitating DNA replication and repair processes. In our previous investigation, it was postulated that the gene RRM2 exhibits elevated expression levels in several categories of malignant tumors, particularly in HBV-related HCC. Additionally, it was observed that RRM2 is present within protein complexes that are centered on HBx. In the present investigation, the objective of this work was to investigate the potential relationship between the elevated expression of RRM2 in HBV-related HCC and the influence of HBx on this expression. The study attempted to determine the specific mechanism by which RRM2 is implicated in the promotion of hepatocarcinogenesis by HBx. There have been multiple scholarly proposals suggesting that the induction of autophagy by HBx is a significant intermediary factor in the development of HCC. However, the precise carcinogenic function of HBx-induced autophagy remains a subject of debate.

RESULTS

This work initially investigated the impact of suppressing cellular autophagy on the malignant biological behaviors of HBx-promoted cells using an in vitro cellular model. The findings revealed that the suppression of cellular autophagy partially disrupted the oncogenic effects of HBx. In light of this, we proceeded to conduct more investigations into the regulatory association between RRM2 and HBx-induced autophagy in the upstream-downstream context. Our data indicate that HBx proteins increase the expression of RRM2. Suppression of RRM2 expression not only hinders HBx-induced autophagy, but also worsens the cellular G1/S blockage and reduces the HBx-induced malignant growth of hepatocellular carcinoma tumors, while stimulating apoptosis.

CONCLUSIONS

Therefore, we hypothesised that RRM2 is a potential downstream target of HBx-induced hepatocarcinogenesis, and mining the oncogenic mechanism of RRM2 is significant in exploring the preventive treatment of HBV-related HCC.

Genome-wide identification of ATG genes and their expression profiles under biotic and abiotic stresses in Fenneropenaeus chinensis

BACKGROUND

Autophagy is a conserved catabolic process in eukaryotes that contributes to cell survival in response to multiple stresses and is important for organism fitness. Extensive research has shown that autophagy plays a pivotal role in both viral infection and replication processes. Despite the increasing research dedicated to autophagy, investigations into shrimp autophagy are relatively scarce.

RESULTS

Based on three different methods, a total of 20 members of the ATGs were identified from F. chinensis, all of which contained an autophagy domain. These genes were divided into 18 subfamilies based on their different C-terminal domains, and were found to be located on 16 chromosomes. Quantitative real-time PCR (qRT-PCR) results showed that ATG genes were extensively distributed in all the tested tissues, with the highest expression levels were detected in muscle and eyestalk. To clarify the comprehensive roles of ATG genes upon biotic and abiotic stresses, we examined their expression patterns. The expression levels of multiple ATGs showed an initial increase followed by a decrease, with the highest expression levels observed at 6 h and/or 24 h after WSSV injection. The expression levels of three genes (ATG1, ATG3, and ATG4B) gradually increased until 60 h after injection. Under low-salt conditions, 12 ATG genes were significantly induced, and their transcription abundance peaked at 96 h after treatment.

CONCLUSIONS

These results suggested that ATG genes may have significant roles in responding to various environmental stressors. Overall, this study provides a thorough characterization and expression analysis of ATG genes in F. chinensis, laying a strong foundation for further functional studies and promising potential in innate immunity.

Biological Functions and Potential Therapeutic Significance of O-GlcNAcylation in Hepatic Cellular Stress and Liver Diseases

O-linked-β-D-N-acetylglucosamine (O-GlcNAc) glycosylation (O-GlcNAcylation), which is dynamically regulated by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), is a post-translational modification involved in multiple cellular processes. O-GlcNAcylation of proteins can regulate their biological functions via crosstalk with other post-translational modifications, such as phosphorylation, ubiquitination, acetylation, and methylation. Liver diseases are a major cause of death worldwide; yet, key pathological features of the disease, such as inflammation, fibrosis, steatosis, and tumorigenesis, are not fully understood. The dysregulation of O-GlcNAcylation has been shown to be involved in some severe hepatic cellular stress, viral hepatitis, liver fibrosis, nonalcoholic fatty acid liver disease (NAFLD), malignant progression, and drug resistance of hepatocellular carcinoma (HCC) through multiple molecular signaling pathways. Here, we summarize the emerging link between O-GlcNAcylation and hepatic pathological processes and provide information about the development of therapeutic strategies for liver diseases.

The N-linked glycosylation modifications in the hepatitis B surface protein impact cellular autophagy, HBV replication, and HBV secretion

N-linked glycosylation is a pivotal post-translational modification that significantly influences various aspects of protein biology. Autophagy, a critical cellular process, is instrumental in cell survival and maintenance. The hepatitis B virus (HBV) has evolved mechanisms to manipulate this process to ensure its survival within host cells. Significantly, post-translational N-linked glycosylation in the large surface protein of HBV (LHBs) influences virion assembly, infectivity, and immune evasion. This study investigated the role of N-linked glycosylation of LHBs in autophagy, and its subsequent effects on HBV replication and secretion. LHBs plasmids were constructed by incorporating single-, double-, and triple-mutated N-linked glycosylation sites through amino acid substitutions at N4, N112, and N309. In comparison to the wild-type LHBs, N-glycan mutants, including N309Q, N4-309Q, N112-309Q, and N4-112-309Q, induced autophagy gene expression and led to autophagosome accumulation in hepatoma cells. Acridine orange staining of cells expressing LHBs mutations revealed impaired lysosomal acidification, suggesting potential blockage of autophagic flux at later stages. Furthermore, N-glycan mutants increased the mRNA expression of HBV surface antigen (HBsAg). Notably, N309Q significantly elevated HBx oncogene level. The LHBs mutants, particularly N309Q and N112-309Q, significantly enhanced HBV replication, whereas N309Q, N4-309Q, and N4-112-309Q markedly increased HBV progeny secretion. Remarkably, our findings demonstrated that autophagy is indispensable for the impact of N-linked glycosylation mutations in LHBs on HBV secretion, as evidenced by experiments with a 3-methyladenine (3-MA) inhibitor. Our study provides pioneering insights into the interplay between N-linked glycosylation mutations in LHBs, host autophagy, and the HBV life cycle. Additionally, we offer a new clue for further investigation into carcinogenesis of hepatocellular carcinoma (HCC). These findings underscore the potential of targeting either N-linked glycosylation modifications or the autophagic pathway for the development of innovative therapies against HBV and/or HCC.

An Overview of the Unfolded Protein Response (UPR) and Autophagy Pathways in Human Viral Oncogenesis

Autophagy and Unfolded Protein Response (UPR) can be regarded as the safe keepers of cells exposed to intense stress. Autophagy maintains cellular homeostasis, ensuring the removal of foreign particles and misfolded macromolecules from the cytoplasm and facilitating the return of the building blocks into the system. On the other hand, UPR serves as a shock response to prolonged stress, especially Endoplasmic Reticulum Stress (ERS), which also includes the accumulation of misfolded proteins in the ER. Since one of the many effects of viral infection on the host cell machinery is the hijacking of the host translational system, which leaves in its wake a plethora of misfolded proteins in the ER, it is perhaps not surprising that UPR and autophagy are common occurrences in infected cells, tissues, and patient samples. In this book chapter, we try to emphasize how UPR, and autophagy are significant in infections caused by six major oncolytic viruses-Epstein-Barr (EBV), Human Papilloma Virus (HPV), Human Immunodeficiency Virus (HIV), Human Herpesvirus-8 (HHV-8), Human T-cell Lymphotropic Virus (HTLV-1), and Hepatitis B Virus (HBV). Here, we document how whole-virus infection or overexpression of individual viral proteins in vitro and in vivo models can regulate the different branches of UPR and the various stages of macro autophagy. As is true with other viral infections, the relationship is complicated because the same virus (or the viral protein) exerts different effects on UPR and Autophagy. The nature of this response is determined by the cell types, or in some cases, the presence of diverse extracellular stimuli. The vice versa is equally valid, i.e., UPR and autophagy exhibit both anti-tumor and pro-tumor properties based on the cell type and other factors like concentrations of different metabolites. Thus, we have tried to coherently summarize the existing knowledge, the crux of which can hopefully be harnessed to design vaccines and therapies targeted at viral carcinogenesis.

Autophagy-related genes polymorphism in hepatitis B virus-associated hepatocellular carcinoma: A systematic review

BACKGROUND

Chronic hepatitis B (CHB) virus is the most common risk factor for developing liver malignancy. Autophagy is an essential element in human cell maintenance. Several studies have demonstrated that autophagy plays a vital role in liver cancer at different stages. In this systematic review, we intend to investigate the role of polymorphism and mutations of autophagy-related genes (ATGs) in the pathogenesis and carcinogenesis of the hepatitis B virus (HBV).

MATERIALS AND METHODS

The search was conducted in online databases (Web of Science, PubMed, and Scopus) using Viruses, Infections, Polymorphism, Autophagy, and ATG. The study was conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria.

RESULTS

The primary search results led to 422 studies. By screening and eligibility evaluation, only four studies were relevant. The most important polymorphisms in hepatocellular carcinoma were rs2241880 in ATG16L1, rs77859116, rs510432, and rs548234 in ATG5. Furthermore, some polymorphisms are associated with an increased risk of HBV infection including, rs2241880 in ATG16L1 and rs6568431 in ATG5.

CONCLUSION

The current study highlights the importance of rs2241880 in ATG16L1 and rs77859116, rs510432, and rs548234 in ATG5 for HBV-induced HCC. Additionally, some mutations in ATG16L1 and ATG5 were important in risk of HBV infection. The study highlights the gap of knowledge in the field of ATG polymorphisms in HBV infection and HBV-induced HCC.

Targeted Mevalonate Pathway and Autophagy in Antitumor Immunotherapy

Tumors of the digestive system are currently one of the leading causes of cancer-related death worldwide. Despite considerable progress in tumor immunotherapy, the prognosis for most patients remains poor. In the tumor microenvironment (TME), tumor cells attain immune escape through immune editing and acquire immune tolerance. The mevalonate pathway and autophagy play important roles in cancer biology, antitumor immunity, and regulation of the TME. In addition, there is metabolic crosstalk between the two pathways. However, their role in promoting immune tolerance in digestive system tumors has not previously been summarized. Therefore, this review focuses on the cancer biology of the mevalonate pathway and autophagy, the regulation of the TME, metabolic crosstalk between the pathways, and the evaluation of their efficacy as targeted inhibitors in clinical tumor immunotherapy.

NDP52 mediates an antiviral response to hepatitis B virus infection through Rab9-dependent lysosomal degradation pathway

Autophagy receptor NDP52 triggers bacterial autophagy against infection. However, the ability of NDP52 to protect against viral infection has not been established. We show that NDP52 binds to envelope proteins of hepatitis B virus (HBV) and triggers a degradation process that promotes HBV clearance. Inactivating NDP52 in hepatocytes results in decreased targeting of viral envelopes in the lysosome and increased levels of viral replication. NDP52 inhibits HBV at both viral entry and late replication stages. In contrast to NDP52-mediated bacterial autophagy, lysosomal degradation of HBV envelopes is independent of galectin 8 and ATG5. NDP52 forms complex with Rab9 and viral envelope proteins and links HBV to Rab9-dependent lysosomal degradation pathway. These findings reveal that NDP52 acts as a sensor for HBV infection, which mediates a unique antiviral response to eliminate the virus. This work also suggests direct roles for autophagy receptors in other lysosomal degradation pathways than canonical autophagy.

Hepatitis B virus promotes its own replication by enhancing RAB5A-mediated dual activation of endosomal and autophagic vesicle pathways

Chronic hepatitis B virus (HBV) infection remains one of the major global public health concerns, and it develop into liver fibrosis, cirrhosis, and hepatocellular carcinoma. Recent evidence suggests that endosomal and autophagic vesicles are beneficial for HBV replication. However, it has not been well elucidated how HBV exploits such intracellular vesicle systems for its replication. RAB5A, a member of small GTPase family, plays crucial roles in early endosome biogenesis and autophagy initiation. We observed that RAB5A mRNA and protein levels were significantly increased in HBV-expressing hepatoma cell lines as well as in liver tissue samples from chronic HBV-infected patients. Moreover, RAB5A silencing inhibited HBV replication and subviral particle (SVP) expression significantly in HBV-transfected and -infected hepatoma cells, whereas RAB5A overexpression increased them. Mechanistically, RAB5A increases HBV replication through enhancement of early endosome (EE) - late endosome (LE) activation by interacting with EEA1, as well as enhancing autophagy induction by interacting with VPS34. Additionally, HBV infection enhances RAB5A-mediated dual activation of EE-LE system and autophagy. Collectively, our findings highlight that HBV utilizes RAB5A-mediated dual activation of endosomal and autophagic vesicle pathways for its own replication and persistence. Therefore, RAB5A is a potential target for chronic HBV infection treatment.

Subversion strategies of lysosomal killing by intracellular pathogens

Many pathogenic organisms need to reach either an intracellular compartment or the cytoplasm of a target cell for their survival, replication or immune system evasion. Intracellular pathogens frequently penetrate into the cell through the endocytic and phagocytic pathways (clathrin-mediated endocytosis, phagocytosis and macropinocytosis) that culminates in fusion with lysosomes. However, several mechanisms are triggered by pathogenic microorganisms - protozoan, bacteria, virus and fungus - to avoid destruction by lysosome fusion, such as rupture of the phagosome and thereby release into the cytoplasm, avoidance of autophagy, delaying in both phagolysosome biogenesis and phagosomal maturation and survival/replication inside the phagolysosome. Here we reviewed the main data dealing with phagosome maturation and evasion from lysosomal killing by different bacteria, protozoa, fungi and virus.

Grouper Atg14 promotes Singapore grouper iridovirus (SGIV) replication by inhibiting the host innate immune response

As one of the important members of the autophagy-related protein family, Atg14 plays a key role in the formation and maturation of autophagosomes. However, little is known about the potential roles of fish Atg14 and its roles in virus infection. In the present study, the homolog of Atg14 (EcAtg14) from the orange-spotted grouper (Epinephelus coioides) was cloned and characterized. The open reading frame (ORF) of EcAtg14 consists of 1530 nucleotides, encoding 509 amino acids, with a predicted molecular weight of 56.9 kDa. EcAtg14 was distributed in all tested tissues, with higher expression in liver, blood and spleen. The expression of EcAtg14 was increased in grouper spleen (GS) cells after Singapore grouper iridovirus (SGIV) infection. EcAtg14 was distributed in the cytoplasm of GS cells. Overexpression of EcAtg14 promoted SGIV replication in GS cells and inhibited IFN3, ISRE and NF-κB promoter activities. Co-immunoprecipitation results showed that there was an interaction between EcAtg14 and EcBeclin. EcAtg14 also promoted the synthesis of LC3-II in GS cells. These findings provide a basis for understanding the innate immune mechanism of grouper against viral infection.

METTL14 inhibits malignant progression of oral squamous cell carcinoma by targeting the autophagy-related gene RB1CC1 in an m6A-IGF2BP2-dependent manner

N6-methyladenosine (m6A) plays crucial roles in tumorigenesis and autophagy. However, the underlying mechanisms mediated by m6A and autophagy in the malignant progression of oral squamous cell carcinoma (OSCC) remain unclear. In the present study, we revealed that down-regulated expression of METTL14 was correlated with advanced clinicopathological characteristics and poor prognosis in OSCC. METTL14 knockdown significantly inhibited autophagy and facilitated malignant progression in vitro, and promoted tumor growth and metastasis in vivo. A cell model of rapamycin-induced autophagy was established to identify RB1CC1 as a potential target gene involved in m6A-regulated autophagy in OSCC, through RNA sequencing and methylated RNA immunoprecipitation sequencing (meRIP-seq) analysis. Mechanistically, we confirmed that METTL14 posttranscriptionally enhanced RB1CC1 expression in an m6A-IGF2BP2-dependent manner, thereby affecting autophagy and progression in OSCC, through methylated RNA immunoprecipitation qRT-PCR (meRIP-qPCR), RNA stability assays, mutagenesis assays and dual-luciferase reporter. Collectively, our findings demonstrated that METTL14 serves as an OSCC suppressor by regulating the autophagy-related gene RB1CC1 through m6A modification, which may provide a new insight for the diagnosis and therapy of OSCC.

Unravelling the complexity of lncRNAs in autophagy to improve potential cancer therapy

Autophagy is well-known as an internal catabolic process that is evolutionarily conserved and performs the key biological function in maintaining cellular homeostasis. It is tightly controlled by several autophagy-related (ATG) proteins, which are closely associated with many types of human cancers. However, what has remained controversial is the janus roles of autophagy in cancer progression. Interestingly, the biological function of long non-coding RNAs (lncRNAs) in autophagy has been gradually understood in different types of human cancers. More recently, numerous studies have demonstrated that several lncRNAs may regulate some ATG proteins and autophagy-related signaling pathways to either activate or inhibit the autophagic process in cancer. Thus, in this review, we summarize the latest advance in the knowledge of the complicated relationships between lncRNAs and autophagy in cancer. Also, the in-depth dissection of the lncRNAs-autophagy-cancers axis involved in this review would shed new light on discovery of more potential cancer biomarkers and therapeutic targets in the future.

The hepatitis B virus promotes the progression of non-alcoholic fatty liver disease through incomplete autophagy

Hepatitis B virus (HBV) infection is still a serious public health problem. In recent years, with the increasing incidence of chronic hepatitis B (CHB) combined with nonalcoholic fatty liver disease (NAFLD), a more in-depth exploration of the pathogenesis of CHB combined with NAFLD is required. HBV can induce autophagy and use to increase replication. The removal of fat by autophagy, also known as lipophagy, is also currently considered an alternative pathway for lipid metabolism in liver cells. This degradation of autophagy prevents hepatotoxicity and steatosis. However, it is not known whether there is a correlation between HBV-related autophagy and the progression of NAFLD. We explored how HBV affects disease progression in NAFLD should be " and determined whether it is associated with HBV-associated autophagy. In this study, we constructed HBV-TG mouse high-fat diet (HFD) models and controls, and the results showed that the presence of HBV promoted the occurrence of NAFLD. We also demonstrated that HBV promotes lipid droplet accumulation in hepatocytes using HBV-stable expression cell lines HepG2.2.15 and AML12-HBV. In addition, this study also found that exogenous OA supplementation reduced HBV replication. We further studied the mechanism and found that HBV-related autophagy can promote the absorption of liver cells to lipid droplets. It can reduce the decomposition of lipid droplets by inhibiting the function of autophagolysosome, and eventually lead to the accumulation of lipid droplets in hepatocytes. In a word, HBV promotes the progression of NAFLD by increasing lipid accumulation in hepatocytes through incomplete autophagy.

Pathogenesis of Hepatocellular Carcinoma: The Interplay of Apoptosis and Autophagy

The pathogenesis of hepatocellular carcinoma (HCC) is a multifactorial process that has not yet been fully investigated. Autophagy and apoptosis are two important cellular pathways that are critical for cell survival or death. The balance between apoptosis and autophagy regulates liver cell turnover and maintains intracellular homeostasis. However, the balance is often dysregulated in many cancers, including HCC. Autophagy and apoptosis pathways may be either independent or parallel or one may influence the other. Autophagy may either inhibit or promote apoptosis, thus regulating the fate of the liver cancer cells. In this review, a concise overview of the pathogenesis of HCC is presented, with emphasis on new developments, including the role of endoplasmic reticulum stress, the implication of microRNAs and the role of gut microbiota. The characteristics of HCC associated with a specific liver disease are also described and a brief description of autophagy and apoptosis is provided. The role of autophagy and apoptosis in the initiation, progress and metastatic potential is reviewed and the experimental evidence indicating an interplay between the two is extensively analyzed. The role of ferroptosis, a recently described specific pathway of regulated cell death, is presented. Finally, the potential therapeutic implications of autophagy and apoptosis in drug resistance are examined.

Molecular mechanisms of autophagy and implications in liver diseases

Autophagy is a highly conserved process in which cytosolic contents are degraded by the lysosome, which plays an important role in energy and nutrient balance, and protein or organelle quality control. The liver is the most important organ for metabolism. Studies to date have revealed a significant role of autophagy in the maintenance of liver homeostasis under basal and stressed conditions, and the impairment of autophagy has been closely linked to various liver diseases. Therefore, a comprehensive understanding of the roles of autophagy in liver diseases may help in the development of therapeutic strategies via targeting autophagy. In this review, we will summarize the latest understanding of the molecular mechanisms of autophagy and systematically discuss its implications in various liver diseases, including alcohol-related liver disease, non-alcoholic fatty liver disease, viral hepatitis, hepatocellular carcinoma, and acetaminophen-induced liver injury.

Transcription of Autophagy Associated Gene Expression as Possible Predictors of a Colorectal Cancer Prognosis

(1) Background: Autophagy plays a dual role in oncogenesis-it contributes to the growth of the tumor and can inhibit its development. The aim of this study was to assess changes in the transcriptional activity of LAMP-2, BECN1, PINK1, and FOXO1 genes involved in the autophagy process in histopathologically confirmed adenocarcinoma sections of colorectal cancer: (2) Methods: A gene expression profile analysis was performed using HG-U133A and the RT-qPCR reaction. The transcriptional activity of genes was compared in sections of colorectal cancer in the four clinical stages (CSI-CSIV) concerning the control group; (3) Results: In CSI, the transcriptional activity of the PINK1 gene is highest; in CS II, the LAMP-2 gene is highest, while FOXO1 increases gradually from CSI reaching a maximum in CSIII. There is no BECN1 gene expression in colorectal cancer cells; (4) Conclusions: The observed differences in the mRNA concentration profile of autophagy-related genes in colon cancer specimens may indicate the role of autophagy in the pathogenesis of this cancer. Genes involved in autophagy may be diagnostic tools for colorectal cancer screening and personalized therapy in the future.

Molecular characterization and expression of the autophagy-related gene Atg14 in WSSV-infected Procambarus clarkii

Atg14 (autophagy-related gene 14), also known as Atg14L or Barkor (Beclin-1 associated autophagy-related key regulator), plays an important role in a variety of biological processes including immunity, development, tumor inhibition, longevity, and protection against some cardiac and neurodegenerative diseases. However, very few studies have characterized Atg14 expression in invertebrates, particularly crustaceans. Here, a novel Atg14 gene from Procambarus clarkii (named PcAtg14) was characterized via RACE technology. Bioinformatics analysis showed that the total length of the PcAtg14 gene sequence was 2,880 bp, and it was predicted to encode 488 amino acids. The results of homology comparison showed that PcAtg14 exhibited the highest homology with crustacean the American lobster (Homarus americanus). Quantitative real-time PCR expression analysis showed that PcAtg14 was expressed in all tissues of P. clarkii, with the hepatopancreas having the highest expression and the eyestalk exhibiting the lowest expression. Upon white spot syndrome virus (WSSV) infection, the relative expression of PcAtg14 in the hepatopancreas, muscle, hemocyte, gill, heart and epidermis were significantly up-regulated at different time periods. After PcAtg14 gene silencing via RNA interference (RNAi), the proliferation of WSSV in P. clarkii was significantly inhibited, which coincided with a significant increase in P. clarkii mortality and an increase in the expression of autophagy-related genes (ATGs). Transmission electron microscopy analysis demonstrated an increase in the number of autophagosomes in the hepatopancreas of the PcAtg14 gene silencing group compared to the control group after WSSV infection. Collectively, these results indicated that PcAtg14 suppressed autophagy by reduce the fusion of autophagosomes and lysosomes, thereby promoting WSSV replication in P. clarkii. The findings here therefore provide novel insights into the immune mechanisms through which P. clarkii responds to WSSV infection.

The Interplay between Autophagy and Virus Pathogenesis-The Significance of Autophagy in Viral Hepatitis and Viral Hemorrhagic Fevers

Autophagy is a process focused on maintaining the homeostasis of organisms; nevertheless, the role of this process has also been widely documented in viral infections. Thus, xenophagy is a selective form of autophagy targeting viruses. However, the relation between autophagy and viruses is ambiguous-this process may be used as a strategy to fight with a virus, but is also in favor of the virus's replication. In this paper, we have gathered data on autophagy in viral hepatitis and viral hemorrhagic fevers and the relations impacting its viral pathogenesis. Thus, autophagy is a potential therapeutic target, but research is needed to fully understand the mechanisms by which the virus interacts with the autophagic machinery. These studies must be performed in specific research models other than the natural host for many reasons. In this paper, we also indicate Lagovirus europaeus virus as a potentially good research model for acute liver failure and viral hemorrhagic disease.

Genetic Variations of ALDH (rs671) Are Associated With the Persistence of HBV Infection Among the Chinese Han Population

Alcohol dehydrogenase 1B (ADH1B) and aldehyde dehydrogenase 2 (ALDH2), members of the alcohol dehydrogenase family, have important roles in liver diseases. The roles of the polymorphisms of ADH1B rs1229984 and ALDH2 rs671 in hepatitis B virus (HBV) susceptibility and persistent infection were investigated in the present study. Total 1,034 patients with hepatitis B [99 acute hepatitis B (AHB), 521 chronic hepatitis B (CHB), 158 acute-on-chronic liver failure (ACLF), 159 liver cirrhosis (LC), and 97 hepatocellular carcinoma (HCC)] and 1,262 healthy controls (HCs) of the Chinese Han population were recruited, and single nucleotide polymorphisms (SNPs) of rs671 and rs1229984 were genotyped. Independent and joint roles of rs671 and rs1229984 in HBV infection were analyzed. The results showed that rs671 genotypes had a significantly different distribution among different subgroups. Compared with HCs, the frequency of rs671-AA genotype was higher in hepatitis B individuals, especially in the CHB group [adjusted OR (95%CI) = 1.899 (1.232–2.928), p = 0.003, in the co-dominant model], which showed a significant positive association. It was further confirmed that CHB individuals who carried ALDH2 rs671-AA genotype had a higher risk of persistent HBV infection and higher HBV-DNA quantitation compared with those with GG/GA genotype. In addition, the rs671-AA genotype might predict HCC incidence in patients with CHB. There were no different distributions of alleles or genotypes in rs671 mutant among AHB, ACLF, LC, or HCC groups compared with HCs. These data suggested the possible hazardous role of rs671-AA variant in HBV infection and persistence.

Studies Progression on the Function of Autophagy in Viral Infection

Autophagy is a conservative lysosomal catabolic pathway commonly seen in eukaryotic cells. It breaks down proteins and organelles by forming a two-layer membrane structure of autophagosomes and circulating substances and maintaining homeostasis. Autophagy can play a dual role in viral infection and serve either as a pro-viral factor or an antiviral defense element dependent on the virus replication cycle. Recent studies have suggested the complicated and multidirectional role of autophagy in the process of virus infection. On the one hand, autophagy can orchestrate immunity to curtail infection. On the other hand, some viruses have evolved strategies to evade autophagy degradation, facilitating their replication. In this review, we summarize recent progress of the interaction between autophagy and viral infection. Furthermore, we highlight the link between autophagy and SARS-CoV-2, which is expected to guide the development of effective antiviral treatments against infectious diseases.

Hepatitis B virus X Protein Promotes Liver Cancer Progression through Autophagy Induction in Response to TLR4 Stimulation

Hepatitis B virus X (HBx) protein has been reported as a key protein regulating the pathogenesis of HBV-induced hepatocellular carcinoma (HCC). Recent evidence has shown that HBx is implicated in the activation of autophagy in hepatic cells. Nevertheless, the precise molecular and cellular mechanism by which HBx induces autophagy is still controversial. Herein, we investigated the molecular and cellular mechanism by which HBx is involved in the TRAF6-BECN1-Bcl-2 signaling for the regulation of autophagy in response to TLR4 stimulation, therefore influencing the HCC progression. HBx interacts with BECN1 (Beclin 1) and inhibits the association of the BECN1-Bcl-2 complex, which is known to prevent the assembly of the pre-autophagosomal structure. Furthermore, HBx enhances the interaction between VPS34 and TRAF6-BECN1 complex, increases the ubiquitination of BECN1, and subsequently enhances autophagy induction in response to LPS stimulation. To verify the functional role of HBx in liver cancer progression, we utilized different HCC cell lines, HepG2, SK-Hep-1, and SNU-761. HBx-expressing HepG2 cells exhibited enhanced cell migration, invasion, and cell mobility in response to LPS stimulation compared to those of control HepG2 cells. These results were consistently observed in HBx-expressed SK-Hep-1 and HBx-expressed SNU-761 cells. Taken together, our findings suggest that HBx positively regulates the induction of autophagy through the inhibition of the BECN1-Bcl-2 complex and enhancement of the TRAF6-BECN1-VPS34 complex, leading to enhance liver cancer migration and invasion.

A Decade of Mighty Lipophagy: What We Know and What Facts We Need to Know?

Lipids are integral cellular components that act as substrates for energy provision, signaling molecules, and essential constituents of biological membranes along with a variety of other biological functions. Despite their significance, lipid accumulation may result in lipotoxicity, impair autophagy, and lysosomal function that may lead to certain diseases and metabolic syndromes like obesity and even cell death. Therefore, these lipids are continuously recycled and redistributed by the process of selective autophagy specifically termed as lipophagy. This selective form of autophagy employs lysosomes for the maintenance of cellular lipid homeostasis. In this review, we have reviewed the current literature about how lipid droplets (LDs) are recruited towards lysosomes, cross-talk between a variety of autophagy receptors present on LD surface and lysosomes, and lipid hydrolysis by lysosomal enzymes. In addition to it, we have tried to answer most of the possible questions related to lipophagy regulation at different levels. Moreover, in the last part of this review, we have discussed some of the pathological states due to the accumulation of these LDs and their possible treatments under the light of currently available findings.

Molecular characterization and role in virus infection of Beclin-1 in large yellow croaker (Larimichthys crocea)

Beclin-1, the ortholog of yeast autophagy-related gene 6 (Atg6), has a central role in autophagy, which has been linked to diverse biological processes including immunity, development, tumor suppression, and lifespan extension. However, understanding of function of fish Beclin-1 is limited now. In this study, the complete Beclin-1 cDNA of large yellow croaker Larimichthys crocea (LcBeclin-1) was cloned, whose open reading frame (ORF) is 1344 bp long and encodes a protein of 447 amino acids (aa). The deduced LcBeclin-1 possesses a typical Bcl-2 homology domain 3(BH3) and an APG6 domain that contains a central coiled-coil domain (CCD, residues 174 to 231) and a C-terminal evolutionarily conserved domain (ECD, residues 241 to 334). LcBeclin-1 shared a high amino acid identity of 81.66-98.66% with reported Beclin-1 molecules from other vertebrate species. LcBeclin-1 gene was constitutively expressed in all tissues tested, with the highest levels in heart. LcBeclin-1 transcripts were also detected in primary head kidney granulocytes (PKGs), primary head kidney macrophages (PKMs), primary head kidney leukocytes (PKLs), and large yellow croaker head kidney cell line (LYCK), and were significantly upregulated by poly (I:C) in PKMs and LYCK cells. Subcellular localization showed that LcBeclin-1 was evenly distributed in the cytoplasm and nucleus of LYCK cells. Overexpression of LcBeclin-1 significantly increased the replication of SVCV, as evidenced by increased severity of the cytopathic effects, enhanced viral titre, and upregulated transcriptional levels of viral genes. Further studies showed that LcBeclin-1 induced the occurrence of autophagy in LYCK cells. Additionally, LcBeclin-1 also decreased the expression levels of large yellow croaker interferons (IFNs; IFNc, IFNd, and IFNh), interferon regulatory factor 3 (IRF3) and IRF7, IFN-stimulated genes (ISGs; Mx, PKR, and Viperin) in LYCK cells. All these data suggest that LcBeclin-1 promoted the viral replication possibly by inducing autophagy or negatively modulating IFN response, which will help us to further understand the function of fish Beclin-1.

The Functions of Hepatitis B Virus Encoding Proteins: Viral Persistence and Liver Pathogenesis

About 250 million people worldwide are chronically infected with Hepatitis B virus (HBV), contributing to a large burden on public health. Despite the existence of vaccines and antiviral drugs to prevent infection and suppress viral replication respectively, chronic hepatitis B (CHB) cure remains a remote treatment goal. The viral persistence caused by HBV is account for the chronic infection which increases the risk for developing liver cirrhosis and hepatocellular carcinoma (HCC). HBV virion utilizes various strategies to escape surveillance of host immune system therefore enhancing its replication, while the precise mechanisms involved remain elusive. Accumulating evidence suggests that the proteins encoded by HBV (hepatitis B surface antigen, hepatitis B core antigen, hepatitis B envelope antigen, HBx and polymerase) play an important role in viral persistence and liver pathogenesis. This review summarizes the major findings in functions of HBV encoding proteins, illustrating how these proteins affect hepatocytes and the immune system, which may open new venues for CHB therapies.

Human Coronaviruses: Counteracting the Damage by Storm

Over the past 18 years, three highly pathogenic human (h) coronaviruses (CoVs) have caused severe outbreaks, the most recent causative agent, SARS-CoV-2, being the first to cause a pandemic. Although much progress has been made since the COVID-19 pandemic started, much about SARS-CoV-2 and its disease, COVID-19, is still poorly understood. The highly pathogenic hCoVs differ in some respects, but also share some similarities in clinical presentation, the risk factors associated with severe disease, and the characteristic immunopathology associated with the progression to severe disease. This review aims to highlight these overlapping aspects of the highly pathogenic hCoVs-SARS-CoV, MERS-CoV, and SARS-CoV-2-briefly discussing the importance of an appropriately regulated immune response; how the immune response to these highly pathogenic hCoVs might be dysregulated through interferon (IFN) inhibition, antibody-dependent enhancement (ADE), and long non-coding RNA (lncRNA); and how these could link to the ensuing cytokine storm. The treatment approaches to highly pathogenic hCoV infections are discussed and it is suggested that a greater focus be placed on T-cell vaccines that elicit a cell-mediated immune response, using rapamycin as a potential agent to improve vaccine responses in the elderly and obese, and the potential of stapled peptides as antiviral agents.

PTH1-34 promotes osteoblast formation through Beclin1-dependent autophagic activation

INTRODUCTION

PTH1-34 can stimulate osteoblast formation, which contributes to the improvement of bone loss. PTH1-34 can activate autophagy, and autophagy plays a key role in osteoblast formation. This study aimed to explore the role of autophagy in PTH1-34-regulated osteoblastogenesis.

MATERIALS AND METHODS

In this study, the mice treated with ovariectomy (OVX mice) were used to observe the effect of PTH1-34 on the formation and autophagy of osteoblasts in trabecular bone in vivo. Osteoblast precursor cell line MC3T3-E1 was treated with PTH1-34, and then the autophagic parameters of osteoblast precursors (including autophagic proteins and autophagosome formation) were detected using Western Blotting and Transmission Electron Microscopy. Next, after using autophagic pharmacological inhibitor (3-MA) and silencing vectors of autophagic molecule Beclin1 to downregulate autophagic activity, the parameters related to osteogenesis (including ALP staining intensity, ALP activity, cell proliferation and osteoblastic protein expression) were evaluated using corresponding assays.

RESULTS

In vivo results showed that PTH1-34 not only improved bone loss caused by OVX but also restored Beclin1 expression and autophagic activity of immature osteoblasts in bone tissues. In vitro assays also showed that treatment of PTH1-34 enhanced the autophagy in osteoblast precursors. Moreover, under PTH1-34 intervention, the upregulated osteogenic parameters were reversed by autophagic inhibition with 3-MA. Of note, Beclin1 silencing can recover the osteogenic activity enhanced by PTH1-34.

CONCLUSION

PTH1-34 can enhance the autophagic activity of osteoblast precursors, which is involved in PTH1-34-regulated osteoblast formation. Furthermore, Beclin1, as a key autophagic regulator, plays a pivotal role in PTH1-34-regulated osteoblast precursor autophagy and osteoblastogenesis.

Autophagy in liver diseases: A review

The liver is a highly dynamic metabolic organ that plays critical roles in plasma protein synthesis, gluconeogenesis and glycogen storage, cholesterol metabolism and bile acid synthesis as well as drug/xenobiotic metabolism and detoxification. Research from the past decades indicate that autophagy, the cellular catabolic process mediated by lysosomes, plays an important role in maintaining cellular and metabolic homeostasis in the liver. Hepatic autophagy fluctuates with hormonal cues and the availability of nutrients that respond to fed and fasting states as well as circadian activities. Dysfunction of autophagy in liver parenchymal and non-parenchymal cells can lead to various liver diseases including non-alcoholic fatty liver diseases, alcohol associated liver disease, drug-induced liver injury, cholestasis, viral hepatitis and hepatocellular carcinoma. Therefore, targeting autophagy may be a potential strategy for treating these various liver diseases. In this review, we will discuss the current progress on the understanding of autophagy in liver physiology. We will also discuss several forms of selective autophagy in the liver and the molecular signaling pathways in regulating autophagy of different cell types and their implications in various liver diseases.

Autophagy, Unfolded Protein Response, and Neuropilin-1 Cross-Talk in SARS-CoV-2 Infection: What Can Be Learned from Other Coronaviruses

The COVID-19 pandemic is caused by the 2019-nCoV/SARS-CoV-2 virus. This severe acute respiratory syndrome is currently a global health emergency and needs much effort to generate an urgent practical treatment to reduce COVID-19 complications and mortality in humans. Viral infection activates various cellular responses in infected cells, including cellular stress responses such as unfolded protein response (UPR) and autophagy, following the inhibition of mTOR. Both UPR and autophagy mechanisms are involved in cellular and tissue homeostasis, apoptosis, innate immunity modulation, and clearance of pathogens such as viral particles. However, during an evolutionary arms race, viruses gain the ability to subvert autophagy and UPR for their benefit. SARS-CoV-2 can enter host cells through binding to cell surface receptors, including angiotensin-converting enzyme 2 (ACE2) and neuropilin-1 (NRP1). ACE2 blockage increases autophagy through mTOR inhibition, leading to gastrointestinal complications during SARS-CoV-2 virus infection. NRP1 is also regulated by the mTOR pathway. An increased NRP1 can enhance the susceptibility of immune system dendritic cells (DCs) to SARS-CoV-2 and induce cytokine storm, which is related to high COVID-19 mortality. Therefore, signaling pathways such as mTOR, UPR, and autophagy may be potential therapeutic targets for COVID-19. Hence, extensive investigations are required to confirm these potentials. Since there is currently no specific treatment for COVID-19 infection, we sought to review and discuss the important roles of autophagy, UPR, and mTOR mechanisms in the regulation of cellular responses to coronavirus infection to help identify new antiviral modalities against SARS-CoV-2 virus.

HBx induces hepatocellular carcinogenesis through ARRB1-mediated autophagy to drive the G1/S cycle

The hepatitis B virus X protein (HBx) is involved in the process of hepatocellular carcinoma via the activation of various oncogenes. Our previous study indicated that ARBB1 (arrestin beta 1) promotes hepatocellular carcinogenesis (HCC). However, the role of ARRB1 in HBx-related HCC remains unclear. Herein, we identified that ARRB1 was upregulated by HBx in vivo and in vitro. Arrb1 deficiency suppressed HBx-induced hepatocellular carcinogenesis in several mouse models. Furthermore, knockdown of ARRB1 blocked HBx-induced macroautophagic/autophagic flux and disrupted the formation of autophagosomes. ARRB1 interacted with HBx, and the autophagic core protein MAP1LC3/LC3, a scaffolding protein, was essential for complete autophagy. Inhibition of autophagy by 3-methyladenine or interference of ATG5 or ATG7 attenuated HBx-induced cell cycle acceleration and the subsequent proliferative response via the induction of G₁/S arrest. The absence of autophagy abolished the phosphorylation of CDK2 and the activity of the CDK2-CCNE1 complex. Our results demonstrate that ARRB1 plays a critical role in HBV-related HCC via modulating autophagy and the CDKN1B-CDK2-CCNE1-E2F1 axis and indicate that ARRB1 may be a potential therapeutic target for HCC.

Autophagy in Viral Development and Progression of Cancer

Autophagy is a complex degradative process by which eukaryotic cells capture cytoplasmic components for subsequent degradation through lysosomal hydrolases. Although this catabolic process can be triggered by a great variety of stimuli, action in cells varies according to cellular context. Autophagy has been previously linked to disease development modulation, including cancer. Autophagy helps suppress cancer cell advancement in tumor transformation early stages, while promoting proliferation and metastasis in advanced settings. Oncoviruses are a particular type of virus that directly contribute to cell transformation and tumor development. Extensive molecular studies have revealed complex ways in which autophagy can suppress or improve oncovirus fitness while still regulating viral replication and determining host cell fate. This review includes recent advances in autophagic cellular function and emphasizes its antagonistic role in cancer cells.

Autophagy in Viral Development and Progression of Cancer

Autophagy is a complex degradative process by which eukaryotic cells capture cytoplasmic components for subsequent degradation through lysosomal hydrolases. Although this catabolic process can be triggered by a great variety of stimuli, action in cells varies according to cellular context. Autophagy has been previously linked to disease development modulation, including cancer. Autophagy helps suppress cancer cell advancement in tumor transformation early stages, while promoting proliferation and metastasis in advanced settings. Oncoviruses are a particular type of virus that directly contribute to cell transformation and tumor development. Extensive molecular studies have revealed complex ways in which autophagy can suppress or improve oncovirus fitness while still regulating viral replication and determining host cell fate. This review includes recent advances in autophagic cellular function and emphasizes its antagonistic role in cancer cells.

Hepatitis B Surface Antigen Suppresses the Activation of Nuclear Factor Kappa B Pathway via Interaction With the TAK1-TAB2 Complex

Chronic hepatitis B is a major health problem worldwide, with more than 250 million chronic carriers. Hepatitis B virus interferes with the host innate immune system so as to evade elimination via almost all of its constituent proteins; nevertheless, the function of HBsAg with respect to immune escape remains unclear. This study aimed to determine the role HBsAg plays in assisting HBV to escape from immune responses. We found that HBsAg suppressed the activation of the nuclear factor kappa B (NF-кB) pathway, leading to downregulation of innate immune responses. HBsAg interacted with TAK1 and TAB2 specifically, inhibiting the phosphorylation and polyubiquitination of TAK1 and the K63-linked polyubiquitination of TAB2. Autophagy is a major catabolic process participating in many cellular processes, including the life cycle of HBV. We found that HBsAg promoted the autophagic degradation of TAK1 and TAB2 via the formation of complexes with TAK1 and TAB2, resulting in suppression of the NF-κB pathway. The expression of TAK1, TAB2, and the translocation of NF-κB inversely correlated with HBsAg levels in clinical liver tissues. Taken together, our findings suggest a novel mechanism by which HBsAg interacts with TAK1-TAB2 complex and suppresses the activation of NF-κB signaling pathway via reduction of the post-translational modifications and autophagic degradation.

Autophagy in liver diseases

Autophagy is the liver cell energy recycling system regulating a variety of homeostatic mechanisms. Damaged organelles, lipids and proteins are degraded in the lysosomes and their elements are re-used by the cell. Investigations on autophagy have led to the award of two Nobel Prizes and a health of important reports. In this review we describe the fundamental functions of autophagy in the liver including new data on the regulation of autophagy. Moreover we emphasize the fact that autophagy acts like a two edge sword in many occasions with the most prominent paradigm being its involvement in the initiation and progress of hepatocellular carcinoma. We also focused to the implication of autophagy and its specialized forms of lipophagy and mitophagy in the pathogenesis of various liver diseases. We analyzed autophagy not only in well studied diseases, like alcoholic and nonalcoholic fatty liver and liver fibrosis but also in viral hepatitis, biliary diseases, autoimmune hepatitis and rare diseases including inherited metabolic diseases and also acetaminophene hepatotoxicity. We also stressed the different consequences that activation or impairment of autophagy may have in hepatocytes as opposed to Kupffer cells, sinusoidal endothelial cells or hepatic stellate cells. Finally, we analyzed the limited clinical data compared to the extensive experimental evidence and the possible future therapeutic interventions based on autophagy manipulation.

Autophagy related protein 9A increase in hepatitis B virus-associated hepatocellular carcinoma and the role in apoptosis

The majority of hepatocellular carcinoma (HCC) cases are associated with the hepatitis B virus (HBV) infection. Autophagy related protein 9A (ATG9A) is a transmembrane protein required for autophagosome formation. In order to investigate the role of ATG9A in HBV-associated HCC, ATG9A protein expression was determined in tumor liver tissues and compared with adjacent nontumor tissues from HCC patients with or without HBV infection. In HBV-associated HCC tissues, ATG9A protein level was increased in tumor liver tissues, but not in cases of non-HBV HCC. Our findings suggested that ATG9A might be involved in HBV and cancer cell survival. Therefore, we aimed to analyze the function of ATG9A in HBV replication using RNA interference to evaluate the HBV DNA level using real-time PCR. In the present study, there were no significant differences between shATG9A-transfected HepG2.2.15 cells and the mock control. However, we found that silencing ATG9A affected apoptosis in HepG2.2.15 and HepG2 cell lines. Our results indicated that ATG9A might be partly involved in the survival of HCC. Thus, the inhibition of ATG9A together with other targets might be a potential drug target for HCC treatment.

S6K1 inhibits HBV replication through inhibiting AMPK-ULK1 pathway and disrupting acetylation modification of H3K27

AIMS

To investigated the effect of S6K1 on the replication and transcription of HBV DNA using multiple cell models.

MAIN METHODS

The pgRNA, total HBV RNA and HBV DNA level were detected by Real-time PCR. The HBcAg expression by Western blot and the activity of four HBV promoters, such as preS1, preS2/S, core, and X promoters by using dual luciferase reporter assay. Moreover, we determined S6K1 interacted with HBcAg in both cytoplasm and nucleus through Immunofluorescence, co-immunoprecipitation (CoIP) and Western blot.

KEY FINDINGS

S6K1 inhibited HBV DNA replication and cccDNA-dependent transcription in HBV-expressing stable cell lines. The mechanistic study revealed that S6K1 suppressed HBV DNA replication by inhibiting AMPK-ULK1 autophagy pathway, and the nuclear S6K1 suppressed HBV cccDNA-dependent transcription by inhibiting the acetylation modification of H3K27. In addition, HBV capsid protein (HBcAg) suppressed the phosphorylation level of S6K1Thr389 by interacting with S6K1, indicating a viral antagonism of S6K1-mediated antiviral mechanism.

SIGNIFICANCE

The p70 ribosomal S6 kinase (S6K1) is a serine/threonine protein kinase, and it plays a significant role in different cellular processes. It has been previously reported that S6K1 affects hepatitis B virus (HBV) replication but the underlying mechanism remains unclear. In this study, our data suggested that the activation of S6K1 restricts HBV replication through inhibiting AMPK-ULK1 autophagy pathway and H3K27 acetylation. These findings indicated that S6K1 might be a potential therapeutic target for HBV infection.

Gap Junction Intercellular Communication Negatively Regulates Cadmium-Induced Autophagy and Inhibition of Autophagic Flux in Buffalo Rat Liver 3A Cells

Cadmium is an important environmental pollutant that poses a serious threat to the health of humans and animals. A large number of studies have shown that the liver is one of the important target organs of cadmium. Stimulation of cells can lead to rapid changes in gap junction intercellular communication (GJIC) and autophagy. Previous studies have shown that cadmium can inhibit GJIC and induce autophagy. In order to understand the dynamic changes of GJIC and autophagy in the process of cadmium-induced hepatotoxic injury and the effects of GJIC on autophagy, a time-gradient model of cadmium cytotoxicity was established. The results showed that within 24 h of cadmium exposure, 5 μmol/L cadmium inhibited GJIC by down regulating the expression levels of connexin 43 (Cx43) and disturbing the localization of Cx43 in Buffalo rat liver 3A (BRL 3A) cells. In addition, cadmium induced autophagy and then inhibited autophagic flux in the later stage. During this process, inhibiting of GJIC could exacerbate the cytotoxic damage of cadmium and induce autophagy, but further blocked autophagic flux, promoting GJIC in order to obtain the opposite results.

Targeting Autophagy in Breast Cancer

Breast cancer is a heterogeneous disease consisting of different biological subtypes, with differences in terms of incidence, response to diverse treatments, risk of disease progression, and sites of metastases. In the last years, several molecular targets have emerged and new drugs, targeting PI3K/Akt/mTOR and cyclinD/CDK/pRb pathways and tumor microenvironment have been integrated into clinical practice. However, it is clear now that breast cancer is able to develop resistance to these drugs and the identification of the underlying molecular mechanisms is paramount to drive further drug development. Autophagy is a highly conserved homeostatic process that can be activated in response to antineoplastic agents as a cytoprotective mechanism. Inhibition of autophagy could enhance tumor cell death by diverse anti-cancer therapies, representing an attractive approach to control mechanisms of drug resistance. In this manuscript, we present a review of autophagy focusing on its interplay with targeted drugs used for breast cancer treatment.

The hypothesis that SARS-CoV-2 affects male reproductive ability by regulating autophagy

The outbreak of CoronaVirus Disease19 (COVID19) in December 2019 posed a serious threat to public safety, and its rapid spread caused a global health emergency. Clinical data show that in addition to respiratory system damage, some male patients with COVID-19 are also accompanied by abnormal renal function and even renal damage. As the main receptor of syndrome coronavirus 2 (SARS-CoV-2), angiotensin converting enzyme 2 (ACE2) is also found to be highly expressed not only in respiratory mucosa and alveolar epithelial cells, but also in renal tubule cells, testicular Leydig cells and seminiferous tubule cells. This suggests that SARS-CoV-2 has the possibility of infecting the male reproductive system, and the recent detection of SARS-CoV-2 in the patient's semen further confirms this theory. In previous studies, it has been found that ACE2 has the ability to regulate autophagy. Not only that, recent studies have also found that SARS-CoV-2 infection can also lead to a reduction in autophagy. All of these associate SARS-CoV-2 with autophagy. Furthermore, autophagy has been shown to have an effect on male reproduction in many studies. Based on these, we propose the hypothesis that SARS-CoV-2 affects male reproductive function by regulating autophagy. This hypothesis may provide a new idea for future treatment of COVID-19 male patients with reproductive function injury, and it can also prompt medical staff and patients to consciously check their reproductive function.

Interplay between Cellular Autophagy and Hepatitis B Virus Replication: A Systematic Review

Autophagy, a conserved process in which cells break down and destroy old, damaged, or abnormal proteins and other substances in the cytoplasm through lysosomal degradation, occurs via autophagosome formation and aids in the maintenance of intracellular homeostasis. Autophagy is closely associated with hepatitis B virus (HBV) replication and assembly. Currently, HBV infection is still one of the most serious public health issues worldwide. The unavailability of satisfactory therapeutic strategies for chronic HBV infection indicates an urgent need to elucidate the mechanisms underlying the pathogenesis of HBV infection. Increasing evidence has shown that HBV not only possesses the ability to induce incomplete autophagy but also evades autophagic degradation, indicating that HBV utilizes or hijacks the autophagy machinery for its own replication. Therefore, autophagy might be a crucial target pathway for controlling HBV infection. The definite molecular mechanisms underlying the association between cellular autophagy and HBV replication require further clarification. In this review, we have summarized and discussed the latest findings on the interplay between autophagy and HBV replication.