Hepatitis B Virus Subverts the Autophagy Elongation Complex Atg5-12/16L1 and Does Not Require Atg8/LC3 Lipidation for Viral Maturation

Autophagy-related protein 5 (ATG5) interacts with bone marrow stromal cell antigen 2 (BST2) to stimulate HBV replication through antagonizing the antiviral activity of BST2

Hepatitis B virus (HBV) infection is a major global health burden with 820 000 deaths per year. In our previous study, we found that the knockdown of autophagy-related protein 5 (ATG5) significantly upregulated the interferon-stimulated genes (ISGs) expression to exert the anti-HCV effect. However, the regulation of ATG5 on HBV replication and its underlying mechanism remains unclear. In this study, we screened the altered expression of type I interferon (IFN-I) pathway genes using RT² Profiler™ PCR array following ATG5 knock-down and we found the bone marrow stromal cell antigen 2 (BST2) expression was significantly increased. We then verified the upregulation of BST2 by ATG5 knockdown using RT-qPCR and found that the knockdown of ATG5 activated the Janus kinase/signal transducer and activator of transcription (JAK-STAT) signaling pathway. ATG5 knockdown or BST2 overexpression decreased Hepatitis B core Antigen (HBcAg) protein, HBV DNA levels in cells and supernatants of HepAD38 and HBV-infected NTCP-HepG2. Knockdown of BST2 abrogated the anti-HBV effect of ATG5 knockdown. Furthermore, we found that ATG5 interacted with BST2, and further formed a ternary complex together with HBV-X (HBx). In conclusion, our finding indicates that ATG5 promotes HBV replication through decreasing BST2 expression and interacting with it directly to antagonize its antiviral function.

An artificial-restriction fragment length polymorphism (A-RFLP) method for genotyping intronic SNP rs7587633 C/T of ATG16L1

SNPs could either cause a disorder or directly alter the efficacy of a particular treatment and act as biological markers. The SNP rs7587633 C/T present in the intronic region of the ATG16L1 gene has been studied for its role in psoriasis vulgaris and Palmoplantar pustulosis. To genotype rs7587633 C/T using PCR-RFLP no restriction site is present for any of the restriction enzymes at the SNP position. To develop an artificial-RFLP method for genotyping rs7587633 C/T, the forward primer was designed in such a way that it resulted in the creation of an EcoRI restriction site in the amplified product which could further be digested with EcoRI to find the genotype of the individual. The newly developed A-RFLP method was applied to genotype the SNP rs7587633 C/T in DNA samples of 100 healthy control individuals. The allelic and genotypic frequencies of the SNPs were 0.80(C), 0.20(T) and 65%(CC), 31%(CT) and 4%(TT), respectively. In conclusion, we developed an A-RFLP method to genotype the SNP rs7587633 C/T which is not present in any of the natural restriction sites and this method could be applied to genotype this SNP in various populations/diseases to find its role.

Hepatitis B virus core protein as a Rab-GAP suppressor driving liver disease progression

Chronic hepatitis B virus (HBV) infection can lead to advanced liver pathology. Here, we establish a transgenic murine model expressing a basic core promoter (BCP)-mutated HBV genome. Unlike previous studies on the wild-type virus, the BCP-mutated HBV transgenic mice manifest chronic liver injury that culminates in cirrhosis and tumor development with age. Notably, agonistic anti-Fas treatment induces fulminant hepatitis in these mice even at a negligible dose. As the BCP mutant exhibits a striking increase in HBV core protein (HBc) expression, we posit that HBc is actively involved in hepatocellular injury. Accordingly, HBc interferes with Fis1-stimulated mitochondrial recruitment of Tre-2/Bub2/Cdc16 domain family member 15 (TBC1D15). HBc may also inhibit multiple Rab GTPase-activating proteins, including Rab7-specific TBC1D15 and TBC1D5, by binding to their conserved catalytic domain. In cells under mitochondrial stress, HBc thus perturbs mitochondrial dynamics and prevents the recycling of damaged mitochondria. Moreover, sustained HBc expression causes lysosomal consumption via Rab7 hyperactivation, which further hampers late-stage autophagy and substantially increases apoptotic cell death. Finally, we show that adenovirally expressed HBc in a mouse model is directly cytopathic and causes profound liver injury, independent of antigen-specific immune clearance. These findings reveal an unexpected cytopathic role of HBc, making it a pivotal target for HBV-associated liver disease treatment. The BCP-mutated HBV transgenic mice also provide a valuable model for understanding chronic hepatitis B progression and for the assessment of therapeutic strategies.

Association of ATG16L1 and ATG5 gene polymorphisms with susceptibility to hepatitis B virus infection and progression to HCC in central China

Hepatitis B virus (HBV) infection is a severe public health problem worldwide. The relationship between polymorphisms of autophagy-related 16-like 1 gene (ATG16L1) and autophagy-related gene 5 (ATG5) with susceptibility to the stage of HBV infection has been reported in different populations. Nevertheless, this association is not seen in the population of central China. This study recruited 452 participants, including 246 HBV-infected patients (139 chronically infected HBV without hepatocellular carcinoma [HCC] and 107 HBV-related HCC patients) and 206 healthy controls. Genotyping of ATG16L1 rs2241880 and ATG5 rs688810 were performed using Sanger sequencing and polymerase chain reaction-restriction fragment length polymorphism, respectively. Our results indicated that the G allele of ATG16L1 rs2241880 was more frequent in healthy controls than in patients with chronicHBV infection. After adjusting for age and sex, an association between the ATG16L1 rs2241880 polymorphism and HBV infection was significant under the dominant and allele models (p = 0.009 and 0.003, respectively). However, no association between the ATG5 polymorphisms and HBV infection was observed. We also did not find a significant association between ATG16L1 and ATG5 polymorphisms and the progression of HBV-related HCC. Therefore, the genetic polymorphism of ATG16L1 rs2241880 may be associated with susceptibility to HBV infection in the population of central China.

Interconnection of cellular autophagy and endosomal vesicle trafficking and its role in hepatitis B virus replication and release

Hepatitis B virus (HBV) produces and releases various particle types, including complete virions, subviral particles with envelope proteins, and naked capsids. Recent studies demonstrate that HBV exploits distinct intracellular membrane trafficking pathways, including the endosomal vesicle trafficking and autophagy pathway, to assemble and release viral and subviral particles. Herein, we summarize the findings about the distinct roles of autophagy and endosomal membrane trafficking and the interaction of both pathways in HBV replication, assembly, and release.

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.

SCD1 inhibits HBV replication by regulating autophagy under high lipid conditions

Chronic hepatitis B virus (HBV) infection remains a significant public health concern worldwide. Several metabolic processes regulate HBV DNA replication, including autophagy and lipid metabolism. In this study, we clarified the effect of lipids on HBV replication and elucidated possible mechanisms. We discovered that lipid metabolic gene expression levels were negatively correlated with the HBV DNA in plasma. Our data showed that fatty acid stimulation significantly reduced HBV DNA, hepatitis B surface antigen (HBsAg), and hepatitis B e antigen (HBeAg) levels in HepG2.2.15 cells, which are human hepatoma cell cultures transfected with HBV DNA. The Stearoyl coenzyme A desaturase 1 (SCD1)-autophagy pathway has also been implicated in inhibiting HBV replication by fatty acids stimulation. SCD1 knockdown deregulates the inhibitory effect of fatty acids on HBV by enhancing autophagy. When 3 methyladenine (3MA) was added, the inhibitory effects of specific autophagy inhibitors eliminated the positive effects of SCD1 knockdown on HBV replication. Our results indicate that SCD1 participates in the regulation of inhibition of HBV replication by fatty acids stimulation through regulating autophagy.

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.

Canocapavir Is a Novel Capsid Assembly Modulator Inducing a Conformational Change of the Linker Region of HBV Core Protein

Canocapavir is a novel antiviral agent with characteristics of core protein allosteric modulators (CpAMs) that is currently in a phase II clinical trial for treatment of hepatitis B virus (HBV) infection. Herein, we show that Canocapavir prevented the encapsidation of HBV pregenomic RNA and increased the accumulation of cytoplasmic empty capsids, presumably by targeting the hydrophobic pocket at the dimer-dimer interface of HBV core protein (HBc). Canocapavir treatment markedly reduced the egress of naked capsids, which could be reversed by Alix overexpression through a mechanism other than direct association of Alix with HBc. Moreover, Canocapavir interfered with the interaction between HBc and HBV large surface protein, resulting in diminished production of empty virions. Of particular note, Canocapavir induced a conformational change of capsids, with the C-terminus of HBc linker region fully exposed on the exterior of capsids. We posit that the allosteric effect may have great importance in the anti-HBV activity of Canocapavir, given the emerging virological significance of HBc linker region. In support of this notion, the mutation at HBc V124W typically recapitulated the conformational change of the empty capsid with aberrant cytoplasmic accumulation. Collectively, our results indicate Canocapavir as a mechanistically distinct type of CpAMs against HBV infection.

Anticancer effects of the HDAC inhibitor, 3β,6β‑dihydroxyurs‑12‑en‑27‑oic acid, in MCF‑7 breast cancer cells via the inhibition of Akt/mTOR pathways

Astilbe chinensis (A. chinensis) is a perennial herb that is used to treat chronic bronchitis and pain. The anticancer activity of 3β,6β‑dihydroxyurs‑12‑en‑27‑oic acid (ACT‑3), a major component isolated from A. chinensis, has not yet been investigated in detail. The purpose of the present study was to investigate the histone deacetylase (HDAC) inhibitory and anticancer activities of ACT‑3 compared with suberoylanilide hydroxamic acid (SAHA) in MCF‑7 human breast cancer cells. The purity of ACT‑3 was determined using high‑performance liquid chromatography. In the present study, the effects of ACT‑3 on anticancer effects of MCF‑7 cells were determined by measuring the level of apoptotic cell death and cell cycle regulator using flow cytometry analysis and western blot analysis, respectively. The effects of ACT‑3 on HDAC enzyme activity were measured using assay kits. ACT‑3 and SAHA increased the levels of acetylated histone H3 and reduced the levels of HDAC1 and HDAC3 in MCF‑7 cells. ACT‑3 significantly decreased the cell viability in a concentration‑dependent manner and induced different morphological changes at high concentrations. ACT‑3 and SAHA significantly inhibited the colony formation in MCF‑7 cells. ACT‑3 inhibited total HDAC activity in a dose‑dependent manner. ACT‑3 significantly reduced the expression levels of cyclin D1 and cyclin‑dependent kinase 4, and upregulated the expression levels of p21^WAF1 and p53. A significant increase in the G1 phase cell population was observed in MCF‑7 cells and ACT‑3 induced apoptosis by reducing the ratio of B‑cell lymphoma‑2 (Bcl‑2)/Bcl‑2‑associated X (Bax) and releasing cleaved caspase 9. Additionally, ACT‑3 significantly increased autophagic cell death by inhibiting the serine‑threonine kinase/mammalian target of the rapamycin pathway. Autophagy induction was confirmed via acridine orange staining. ACT‑3 significantly increased the pERK1/2 and p21 in MCF‑7 cells. Thus, the activated ERK pathway played an important role in cell cycle arrest and apoptosis via ERK‑dependent induction of p21 in MCF‑7 cells. These data indicated that ACT‑3 can be used as a promising anticancer agent to overcome the limitations and reduce the side effects of conventional anticancer drugs.

Sac1 phosphatidylinositol 4-phosphate phosphatase is a novel host cell factor regulating hepatitis B virus particles assembly and release

The life-cycle of the Hepatitis B Virus (HBV), an enveloped DNA virus affecting the lives of more than 296 million chronicallyinfected people, is tightly dependent on the lipid metabolism of the host cell. Fatty acids and cholesterol are among the lipid factors with documented roles in regulating HBV replication and infection, respectively, but little is known about the phosphoinositide metabolism in these processes. In this study, we investigated the role of Sac1, a highly conserved phosphatidylinositol-4-phosphate (PI4P) phosphatase, with essential functions in phospholipid metabolism, in HBV assembly, and release. PI4P is one of the most abundant cellular phosphoinositide with complex functions at the level of the secretory pathway. Owing to the highly specific phosphatase activity toward PI4P, Sac1 controls the levels and restricts the localization of this lipid particularly at the trans-Golgi network, where it regulates sphingolipid synthesis, proteins sorting, and vesicles budding, by recruiting specific adaptor proteins. As a complete loss of Sac1 function compromises cell viability, in this work, we first developed and characterized several HBV replication-permissive cellular models with a moderate, transient, or stable downregulation of Sac1 expression. Our results show that Sac1 depletion in hepatic cells results in increased levels and redistribution of intracellular PI4P pools and impaired trafficking of the HBV envelope proteins to the endosomal vesicular network. Importantly, virus envelopment and release from these cells are significantly inhibited, revealing novel roles for Sac1, as a key host cell factor regulating morphogenesis of a DNA virus.

Autophagic membranes participate in hepatitis B virus nucleocapsid assembly, precore and core protein trafficking, and viral release

Hepatitis B virus (HBV) DNA replication takes place inside the viral core particle and is dependent on autophagy. Here we show that HBV core particles are associated with autophagosomes and phagophores in cells that productively replicate HBV. These autophagic membrane-associated core particles contain almost entirely the hypophosphorylated core protein and are DNA replication competent. As the hyperphosphorylated core protein can be localized to phagophores and the dephosphorylation of the core protein is associated with the packaging of viral pregenomic RNA (pgRNA), these results are in support of the model that phagophores can serve as the sites for the packaging of pgRNA. In contrast, in cells that replicate HBV, the precore protein derivatives, which are related to the core protein, are associated with autophagosomes but not with phagophores via a pathway that is independent of its signal peptide. Interestingly, when the core protein is expressed by itself, it is associated with phagophores but not with autophagosomes. These observations indicate that autophagic membranes are differentially involved in the trafficking of precore and core proteins. HBV induces the fusion of autophagosomes and multivesicular bodies and the silencing of Rab11, a regulator of this fusion, is associated with the reduction of release of mature HBV particles. Our studies thus indicate that autophagic membranes participate in the assembly of HBV nucleocapsids, the trafficking of HBV precore and core proteins, and likely also the egress of HBV particles.

Region-Specific Hepatitis B Virus Genome Exposure from Nucleocapsid Modulated by Capsid Linker Sequence and Inhibitor: Implications for Uncoating

Hepatitis B virus (HBV) contains a partially double-stranded, relaxed circular (RC) DNA genome synthesized within a nucleocapsid (NC) in the host cell cytoplasm. The release of RC DNA from the NC, in an ill-defined process called uncoating, to the nucleus is required for its conversion to the covalently closed circular (CCC) DNA, the viral episome serving as the transcriptional template for all viral RNAs necessary for replication and, thus, essential for establishing and sustaining viral infection. In efforts to better understand uncoating, we analyzed HBV core (HBc) mutants that show various levels of nuclear CCC DNA but little to no cytoplasmic RC DNA. We found that RC DNA could be synthesized by these mutants outside the cell, but in contrast to the wild type (wt), the mutant NCs were unable to protect RC DNA from digestion by the endogenous nuclease(s) in cellular lysates or exogenous DNase. Subcellular fractionation suggested that the major RC DNA-degrading activity was membrane associated. Digestion with sequence-specific and nonspecific DNases revealed the exposure of specific regions of RC DNA from the mutant NC. Similarly, treatment of wt NCs with a core inhibitor known to increase CCC DNA by affecting uncoating also led to region-specific exposure of RC DNA. Furthermore, a subpopulation of untreated wild type (wt) mature NCs showed site-specific exposure of RC DNA as well. Competition between RC DNA degradation and its conversion to CCC DNA during NC uncoating thus likely plays an important role in the establishment and persistence of HBV infection and has implications for the development of capsid-targeted antivirals. IMPORTANCE Disassembly of the hepatitis B virus (HBV) nucleocapsid (NC) to release its genomic DNA, in an ill-understood process called uncoating, is required to form the viral nuclear episome in the host cell nucleus, a viral DNA essential for establishing and sustaining HBV infection. The elimination of the HBV nuclear episome remains the holy grail for the development of an HBV cure. We report here that the HBV genomic DNA is exposed in a region-specific manner during uncoating, which is enhanced by mutations of the capsid protein and a capsid-targeted antiviral compound. The exposure of the viral genome can result in its rapid degradation or, alternatively, can enhance the formation of the nuclear episome, thus having a major impact on HBV infection and persistence. These results are thus important for understanding fundamental mechanisms of HBV replication and persistence and for the ongoing pursuit of an HBV cure.

Endoplasmic reticulum stress promotes HBV production by enhancing use of the autophagosome/multivesicular body axis

BACKGROUND AND AIMS

HBV infection has been reported to trigger endoplasmic reticulum (ER) stress and initiate autophagy. However, how ER stress and autophagy influence HBV production remains elusive. Here, we studied the effect of tunicamycin (TM), an N-glycosylation inhibitor and ER stress inducer, on HBV replication and secretion and examined the underlying mechanisms.

APPROACH AND RESULTS

Protein disulfide isomerase (an ER marker), microtubule-associated protein 1 light chain 3 beta (an autophagosome [AP] marker), and sequestosome-1 (a typical cargo for autophagic degradation) expression were tested in liver tissues of patients with chronic HBV infection and hepatoma cell lines. The role of TM treatment in HBV production and trafficking was examined in hepatoma cell lines. TM treatment that mimics HBV infection triggered ER stress and increased AP formation, resulting in enhanced HBV replication and secretion of subviral particles (SVPs) and naked capsids. Additionally, TM reduced the number of early endosomes and HBsAg localization in this compartment, causing HBsAg/SVPs to accumulate in the ER. Thus, TM-induced AP formation serves as an alternative pathway for HBsAg/SVP trafficking. Importantly, TM inhibited AP-lysosome fusion, accompanied by enhanced AP/late endosome (LE)/multivesicular body fusion, to release HBsAg/SVPs through, or along with, exosome release. Notably, TM treatment inhibited HBsAg glycosylation, resulting in impairment of HBV virions' envelopment and secretion, but it was not critical for HBsAg/SVP trafficking in our cell systems.

CONCLUSIONS

TM-induced ER stress and autophagic flux promoted HBV replication and the release of SVPs and naked capsids through the AP-LE/MVB axis.

Role of Autophagy Machinery Dysregulation in Bacterial Chondronecrosis with Osteomyelitis (BCO)

Autophagy is a cell survival and homeostasis mechanism involving lysosomal degradation of cellular components and foreign bodies. It plays a role in bone homeostasis, skeletal diseases, and bacterial infections as both a cell-survival or cell-death pathway. This study sought to determine if autophagy played a role in bacterial chondronecrosis with osteomyelitis (BCO). BCO is a prominent cause of lameness in modern broilers and results from bacterial infection of mechanically stressed leg bone growth plates. The protein and gene expression of key autophagy machinery was analyzed in both normal and BCO-affected broilers using real-time qPCR and immunoblot, respectively. Gene expression showed a significant downregulation of key target signatures involved in every stage of autophagy in BCO-affected bone, such as ATG13, SQSTM1 (p62), ATG9B, ATG16L, ATG12, LC3C, and RAB7A. Additionally, protein expression for LC3 was also significantly lower in BCO. An in vitro study using human fetal osteoblast cells challenged with BCO isolate, Staphylococcus agnetis 908, showed a similar dysregulation of autophagy machinery along with a significant decrease in cell viability. When autophagy was inhibited via 3-methyladenine or chloroquine, comparable decreases in cell viability were seen along with dysregulation of autophagy machinery. Together, these results are the first to implicate autophagy machinery dysregulation in the pathology of BCO.

ATG12 is involved in the antiviral immune response in large yellow croaker (Larimichthys crocea)

ATG12, a core autophagy protein, forms a conjugate with ATG5 to promote the formation of autophagosome membrane, and plays an important role in antiviral immunity. However, little is known about the function of ATG12 in fish. Here, we cloned the open reading frame (ORF) of large yellow croaker (Larimichthys crocea) ATG12 (LcATG12), which is 354 nucleotides long and encodes a protein of 117 amino acids. The deduced LcATG12 possesses a conserved APG12 domain (residues 31 to 117), and shares 91.45% identities with ATG12 in orange-spotted grouper (Epinephelus coioides). LcATG12 was constitutively expressed in all examined tissues, with the highest level in intestine. Its transcript was also detected in primary head kidney granulocytes (PKG), primary head kidney macrophages (PKM), primary head kidney lymphocytes (PKL), and large yellow croaker head kidney (LYCK) cell line, and was significantly up-regulated by poly(I:C). LcATG12 was regularly distributed in both cytoplasm and nucleus of LYCK and epithelioma papulosum cyprinid (EPC) cells. Overexpression of LcATG12 in EPC cells significantly inhibited the replication of spring viremia of carp virus (SVCV). Further studies reveled that LcATG12 could induce the occurrence of autophagy in LYCK cells. Furthermore, overexpression of LcATG12 in LYCK cells increased the expression levels of large yellow croaker type I interferons (IFNs, IFNc, IFNd, and IFNh), IFN regulatory factors (IRF3 and IRF7), and IFN-stimulated genes (PKR, Mx, and Viperin). All these data indicated that LcATG12 plays a role in the antiviral immunity possibly by inducing both autophagy and type I IFN response in large yellow croaker.

Emerging roles of autophagy in the development and treatment of urothelial carcinoma of the bladder

INTRODUCTION

High recurrence rates, frequent surveillance strategies, and current multidisciplinary treatment approaches make urothelial carcinoma of bladder (UCB) one of the most expensive cancers to clinically manage. Recent studies have demonstrated a role for autophagy in bladder tumorigenesis. It serves as a tumor suppressor by maintaining genomic integrity and preventing tumor proliferation during initial stages of tumor development. Nevertheless, once established, cancer cells may utilize protective autophagy to endure cellular stress and survive in the adverse environment. Its excessive stimulation supports cancer cells' resistance to therapeutic modalities.

AREAS COVERED

PubMed and Google Scholar electronic databases were searched for recently published studies. This review summarizes emerging roles of autophagy in development/progression of UCB and treatment resistance and explores novel therapeutic targets for prevention of cancer invasion, metastatic spread', and disease relapse.

EXPERT OPINION

The development of novel therapies via targeting of autophagy may augment current treatment regimens and improve clinical outcomes. Synthetic compounds or plant-based metabolites are reported to enhance cancer therapies by modulating autophagic flux. Successful autophagy-focused therapeutic intervention requires a mechanistic understanding of autophagic effects on tumor initiation and progression and the development of efficient biomarkers to monitor it in tumor tissues.

The Hepatitis B Virus Interactome: A Comprehensive Overview

Despite the availability of a prophylactic vaccine, chronic hepatitis B (CHB) caused by the hepatitis B virus (HBV) is a major health problem affecting an estimated 292 million people globally. Current therapeutic goals are to achieve functional cure characterized by HBsAg seroclearance and the absence of HBV-DNA after treatment cessation. However, at present, functional cure is thought to be complicated due to the presence of covalently closed circular DNA (cccDNA) and integrated HBV-DNA. Even if the episomal cccDNA is silenced or eliminated, it remains unclear how important the high level of HBsAg that is expressed from integrated HBV DNA is for the pathology. To identify therapies that could bring about high rates of functional cure, in-depth knowledge of the virus' biology is imperative to pinpoint mechanisms for novel therapeutic targets. The viral proteins and the episomal cccDNA are considered integral for the control and maintenance of the HBV life cycle and through direct interaction with the host proteome they help create the most optimal environment for the virus whilst avoiding immune detection. New HBV-host protein interactions are continuously being identified. Unfortunately, a compendium of the most recent information is lacking and an interactome is unavailable. This article provides a comprehensive review of the virus-host relationship from viral entry to release, as well as an interactome of cccDNA, HBc, and HBx.

Early type 1 diabetes aggravates renal ischemia/reperfusion-induced acute kidney injury

The present study aimed to investigate the interaction between early diabetes and renal IR-induced AKI and to clarify the mechanisms involved. C57BL/6J mice were assigned to the following groups: (1) sham-operated; (2) renal IR; (3) streptozotocin (STZ-55 mg/kg/day) and sham operation; and (4) STZ and renal IR. On the 12th day after treatments, the animals were subjected to bilateral IR for 30 min followed by reperfusion for 48 h, at which time the animals were euthanized. Renal function was assessed by plasma creatinine and urea levels, as well urinary protein contents. Kidney morphology and gene and protein expression were also evaluated. Compared to the sham group, renal IR increased plasma creatinine, urea and albuminuria levels and decreased Nphs1 mRNA expression and nephrin and WT1 protein staining. Tubular injury was observed with increased Havcr1 and Mki67 mRNA expression accompanied by reduced megalin staining. Renal IR also resulted in increased SQSTM1 protein expression and increased proinflammatory and profibrotic factors mRNA expression. Although STZ treatment resulted in hyperglycemia, it did not induce significant changes in renal function. On the other hand, STZ treatment aggravated renal IR-induced AKI by exacerbating renal dysfunction, glomerular and tubular injury, inflammation, and profibrotic responses. Thus, early diabetes constitutes a relevant risk factor for renal IR-induced AKI.

ASPP2 inhibits hepatitis B virus replication by preventing nucleus translocation of HSF1 and attenuating the transactivation of ATG7

Hepatitis B virus (HBV) is a kind of virus with the capability to induce autophagy, thereby facilitating its replication. Reducing hepatocyte autophagy is proved to be a useful way to inhibit HBV replication. Herein, we reported that p53-binding protein 2 (apoptosis-stimulating protein of p53-2, ASPP2) could attenuate HBV-induced hepatocyte autophagy in a p53-independent manner. Mechanistically, overexpressed ASPP2 binds to HSF1 in cytoplasm of HBV-infected cells, which prevents the translocation of HSF1 to nuclei, thereby inhibiting the transactivation of Atg7. By regulating the transcription of Atg7, ASPP2 reduces hepatocyte autophagy, thereby inhibiting HBV replication. Therefore, ASPP2 is a key regulator of cell autophagy, and overexpression of ASPP2 could be a novel method to inhibit HBV replication in hepatocytes.

CCDC88A/GIV promotes HBV replication and progeny secretion via enhancing endosomal trafficking and blocking autophagic degradation

Hepatitis B virus (HBV) particles are thought to be secreted from hepatocytes through multivesicular bodies (MVBs); however, the cellular trafficking mechanisms prior to this process remain elusive. It has been reported that CCDC88A/GIV expression, which is involved in multiple aspects of vesicular trafficking, changes dynamically at different phases of chronic HBV infection. In this study, we focused on the role of CCDC88A/GIV in HBV replication. In the liver tissues of chronically HBV-infected patients, HBV infection significantly enhanced CCDC88A/GIV expression, and increased endoplasmic reticulum (ER) stress and autophagosome formation without changing endosome formation. Additionally, colocalization of SHBsAg with early endosomes (~30.2%) far exceeded that with autophagosomes (~3.2%). In hepatoma cells, CCDC88A/GIV and its downstream proteins, DNM2 (dynamin 2; a CCDC88A/GIV effector), CLTC and RAB5A significantly enhanced HBV replication and endosome formation but inhibited autophagosome formation. Blocking endocytosis disrupted HBsAg trafficking to endosomes and caused its accumulation in the ER lumen, which triggered ER stress to initiate the unfolded protein response (UPR). Therefore, HBsAg trafficking into autophagosomes was increased, and the lysosomal activity and maturation, which was inhibited by HBV infection, were restored. Meanwhile, core particles were prevented from entering MVBs. CCDC88A/GIV and its other effector, GNAI3, decreased autophagic flux by enhancing the insulin-induced AKT-MTOR pathway, thereby inhibiting HBV antigens autophagic degradation. In conclusion, CCDC88A/GIV enhanced HBV replication by increasing endosomal trafficking and reducing autophagic degradation of HBV antigens, suggesting that CCDC88A/GIV-mediated endosomal trafficking plays an important role in HBV replication and progeny secretion.Abbreviations: ACTB: actin beta; AO: acridine orange; ATF6: activating transcription factor 6; CCDC88A/GIV: coiled-coil domain containing 88A; CLTC: clathrin heavy chain; CQ: chloroquine; DAPI: 4ʹ,6-diamidino-2-phenylindole; DNM2: dynamin 2; ER: endoplasmic reticulum; ERN1: endoplasmic reticulum to nucleus signaling 1; EIF2A: eukaryotic translation initiation factor 2A; FBS: fetal bovine serum; GNAI3: G protein subunit alpha i3; HBV: hepatitis B virus; HBV RIs: HBV replication intermediates; HBcAg: HBV core protein; HBsAg: HBV surface antigen; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MVBs: multivesicular bodies; MTOR: mechanistic target of rapamycin kinase; PDI: protein disulfide isomerase; PHH: primary human hepatocyte; pSM2: a HBV replication-competent plasmid; HSPA5/BIP: heat shock protein family A (Hsp70) member 5; SQSTM1/p62: sequestosome 1; siRNA: small interfering RNA; SEM: standard error of the mean; UPR: unfolded protein response

Excess fibronectin 1 participates in pathogenesis of pre-eclampsia by promoting apoptosis and autophagy in vascular endothelial cells

Plasma fibronectin 1 (FN1) levels are elevated in individuals with pre-eclampsia (PE), which may be applied as a possible b marker for vascular endothelial injury during PE. In the present study, the possible role of FN1 in the pathogenesis of PE and regulation of apoptosis and autophagy in vascular endothelial cells was explored. Plasma FN1 levels in 80 patients with PE and 40 healthy pregnant individuals were measured using ELISA to verify its relationship with the severity of PE. pcDNA3.1-FN1 or FN1-small interfering (si) RNA was used to manipulate the expression of FN1 in human umbilical vein endothelial cells (HUVECs) to assess the effects of FN1 on cell apoptosis, autophagy, and the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mechanistic target of rapamycin (mTOR) signaling pathway. It was found that upregulation of FN1 promoted apoptosis and autophagy, in addition to significantly inhibiting the activation of AKT and mTOR in HUVECs. By contrast, downregulation of FN1 expression inhibited cell apoptosis and autophagy, but increased AKT and mTOR phosphorylation in HUVECs that were cultured in serum samples obtained from patients with PE. Rescue experiments found that the PI3K/AKT inhibitor LY294002 reversed the effects of FN1-siRNA on apoptosis and autophagy in HUVECs cultured in serum from patients with PE. Therefore, data from the present study suggest that FN1 participates in the pathogenesis of PE by promoting apoptosis and autophagy in vascular endothelial cells, which is associated with the PI3K/AKT/mTOR signaling pathway.

Transcriptomic and Functional Analyses Indicate Novel Anti-viral Mode of Actions on Tobacco Mosaic Virus of a Microbial Natural Product ε-Poly-l-lysine

Novel anti-viral natural product ε-poly-l-lysine (ε-PL) produced by Streptomyces is a homopolymer of l-lysine, of which the underlying molecular mode of action remains to be further elucidated. In this study, ε-PL induced significant fragmentation of tobacco mosaic virus (TMV) virions and delayed the systemic infection of TMV-GFP as well as wild-type TMV in plants. ε-PL treatment also markedly inhibited RNA accumulation of TMV in tobacco BY-2 protoplasts. The results of RNA-seq indicated that the agent induced significantly differential expression of genes that are associated with defense response, stress response, autophagy, and ubiquitination. Among them, 15 critical differential expressed genes were selected for real-time quantitative PCR validation. We further demonstrated that ε-PL can induce host defense responses by assessing the activity of several defense-related enzymes in plants. Our results provided valuable insights into molecular anti-viral mode of action for ε-PL, which is expected to be applied as a novel microbial natural product against plant virus diseases.

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.

The regulatory factors and pathological roles of autophagy-related protein 4 in diverse diseases: Recent research advances

Macroautophagy (autophagy) is an evolutionarily conserved and dynamic degradation/recycling pathway in which portions of the cytoplasm, such as dysfunctional proteins and surplus organelles, are engulfed by double-membrane bound vesicles through a lysosome-dependent process. As the only proteolytic enzyme of the core mammalian autophagy proteins, autophagy-related protein 4 (ATG4) primes newly synthesized pro-light chain 3 (LC3) to form LC3-I that attaches to phosphatidylethanolamine and delipidates LC3-PE to LC3-I for recycling. Besides autophagy, ATG4 has been shown to be involved in regulating various biological and pathological processes. The roles of ATG4 in cancer therapy, a methodology for ATG4 activity detection, and the discovery of chemical modulators have been well-reviewed. However, a comprehensive summary on how ATG4 is regulated by multiple factors and, thereby, how ATG4 influences autophagy or other pathways remains lacking. In this paper, we summarize multiple processes and molecules that regulate the activity of ATG4, such as micro-RNAs, posttranslational modifications, and small molecules. Additionally, we focus on the relationship between ATG4 and diverse diseases, including cancer, neurodegeneration, microbial infection, and other diseases. It provides insight regarding potential ATG4-targeted therapeutic opportunities, which could be beneficial for future studies and human health.

Endoplasmic reticulum stress and protein degradation in chronic liver disease

Endoplasmic reticulum (ER) stress is easily observed in chronic liver disease, which often causes accumulation of unfolded or misfolded proteins in the ER, leading to unfolded protein response (UPR). Regulating protein degradation is an integral part of UPR to relieve ER stress. The major protein degradation system includes the ubiquitin-proteasome system (UPS) and autophagy. All three arms of UPR triggered in response to ER stress can regulate UPS and autophagy. Accumulated misfolded proteins could activate these arms, and then generate various transcription factors to regulate the expression of UPS-related and autophagy-related genes. The protein degradation process regulated by UPR has great significance in many chronic liver diseases, including non-alcoholic fatty liver disease (NAFLD), alcoholic liver disease (ALD), viral hepatitis, liver fibrosis, and hepatocellular carcinoma(HCC). In most instances, the degradation of excessive proteins protects cells with ER stress survival from apoptosis. According to the specific functions of protein degradation in chronic liver disease, choosing to promote or inhibit this process is promising as a potential method for treating chronic liver disease.

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.

Hepatitis B Virus Exploits ERGIC-53 in Conjunction with COPII to Exit Cells

Several decades after its discovery, the hepatitis B virus (HBV) still displays one of the most successful pathogens in human populations worldwide. The identification and characterization of interactions between cellular and pathogenic components are essential for the development of antiviral treatments. Due to its small-sized genome, HBV highly depends on cellular functions to produce and export progeny particles. Deploying biochemical-silencing methods and molecular interaction studies in HBV-expressing liver cells, we herein identified the cellular ERGIC-53, a high-mannose-specific lectin, and distinct components of the endoplasmic reticulum (ER) export machinery COPII as crucial factors of viral trafficking and egress. Whereas the COPII subunits Sec24A, Sec23B and Sar1 are needed for both viral and subviral HBV particle exit, ERGIC-53 appears as an exclusive element of viral particle propagation, therefore interacting with the N146-glycan of the HBV envelope in a productive manner. Cell-imaging studies pointed to ER-derived, subcellular compartments where HBV assembly initiates. Moreover, our findings provide evidence that HBV exploits the functions of ERGIC-53 and Sec24A after the envelopment of nucleocapsids at these compartments in conjunction with endosomal sorting complexes required for transport (ESCRT) components. These data reveal novel insights into HBV assembly and trafficking, illustrating therapeutic prospects for intervening with the viral life cycle.

Manipulation of autophagy by (+) RNA viruses

Autophagy is an evolutionarily conserved process central to host metabolism. Among its major functions are conservation of energy during starvation, recycling organelles, and turnover of long-lived proteins. Besides, autophagy plays a critical role in removing intracellular pathogens and very likely represents a primordial intrinsic cellular defence mechanism. More recent findings indicate that it has not only retained its ability to degrade intracellular pathogens, but also functions to augment and fine tune antiviral immune responses. Interestingly, viruses have also co-evolved strategies to manipulate this pathway and use it to their advantage. Particularly intriguing is infection-dependent activation of autophagy with positive stranded (+)RNA virus infections, which benefit from the pathway without succumbing to lysosomal degradation. In this review we summarise recent data on viral manipulation of autophagy, with a particular emphasis on +RNA viruses and highlight key unanswered questions in the field that we believe merit further attention.

Virus-Induced Cytoplasmic Aggregates and Inclusions are Critical Cellular Regulatory and Antiviral Factors

RNA granules, aggresomes, and autophagy are key players in the immune response to viral infections. They provide countermeasures that regulate translation and proteostasis in order to rewire cell signaling, prevent viral interference, and maintain cellular homeostasis. The formation of cellular aggregates and inclusions is one of the strategies to minimize viral infections and virus-induced cell damage and to promote cellular survival. However, viruses have developed several strategies to interfere with these cellular processes in order to achieve productive replication within the host cells. A review on how these mechanisms could function as modulators of cell signaling and antiviral factors will be instrumental in refining the current scientific knowledge and proposing means whereby cellular granules and aggregates could be induced or prevented to enhance the antiviral immune response in mammalian cells.

Mitophagy in the Pathogenesis of Liver Diseases

Autophagy is a catabolic process involving vacuolar sequestration of intracellular components and their targeting to lysosomes for degradation, thus supporting nutrient recycling and energy regeneration. Accumulating evidence indicates that in addition to being a bulk, nonselective degradation mechanism, autophagy may selectively eliminate damaged mitochondria to promote mitochondrial turnover, a process termed “mitophagy”. Mitophagy sequesters dysfunctional mitochondria via ubiquitination and cargo receptor recognition and has emerged as an important event in the regulation of liver physiology. Recent studies have shown that mitophagy may participate in the pathogenesis of various liver diseases, such as liver injury, liver steatosis/fatty liver disease, hepatocellular carcinoma, viral hepatitis, and hepatic fibrosis. This review summarizes the current knowledge on the molecular regulations and functions of mitophagy in liver physiology and the roles of mitophagy in the development of liver-related diseases. Furthermore, the therapeutic implications of targeting hepatic mitophagy to design a new strategy to cure liver diseases are discussed.

Autophagy interferes with human cytomegalovirus genome replication, morphogenesis, and progeny release

Viral infections are often accompanied by the induction of autophagy as an intrinsic cellular defense mechanism. Herpesviruses have developed strategies to evade autophagic degradation and to manipulate autophagy of the host cells to their benefit. Here we addressed the role of macroautophagy/autophagy in human cytomegalovirus replication and for particle morphogenesis. We found that proteins of the autophagy machinery localize to cytoplasmic viral assembly compartments and enveloped virions in the cytoplasm. Surprisingly, the autophagy receptor SQSTM1/p62 was also found to colocalize with HCMV capsids in the nucleus of infected cells. This finding indicates that the autophagy machinery interacts with HCMV already at the early nuclear stages of particle morphogenesis. The membrane-bound form of LC3 and several autophagy receptors were packaged into extracellular HCMV virions. This suggested that autophagic membranes were included during secondary envelopment of HCMV virions. To further address the importance of autophagy in HCMV infection, we generated an HCMV mutant that expressed a dominant-negative version of the protease ATG4B (BAD-ATG4B^C74A). The proteolytic activity of ATG4B is required for LC3 cleavage, priming it for membrane conjugation. Surprisingly, both genome replication and virus release were enhanced in cells infected with BAD-ATG4B^C74A, compared to control strains. These results show that autophagy operates as an antiviral process during HCMV infection but is dispensable for secondary HCMV particle envelopment.Abbreviations: ATG: autophagy-related; BAC: bacterial artificial chromosome; BECN1: beclin 1; CPE: cytopathic effect; cVACs: cytoplasmic viral assembly compartments; d.p.i.: days post-infection; DB: dense body; EBV: Epstein-Barr virus; galK: galactokinase; HCMV: human cytomegalovirus; HFF: human foreskin fibroblasts; IE: immediate-early; IRS: internal repeat short; LC3: MAP1LC3A/B; m.o.i.; multiplicity of infection; MCP: major capsid protein; Pp: phosphoprotein; sCP/UL48a: smallest capsid protein; TRS: terminal repeat short; UL: unique long; US: unique short.

Xenophagy in cancer

Macroautophagy (herein autophagy) is an intracellular pathway in which cytoplasmic components are captured by double-membrane vesicles (autophagosomes) that eventually fuse with lysosomes to degrade the cargo. Basal levels of autophagy in all eukaryotic cells maintain cellular homeostasis and under conditions of stress, organelles and proteins not essential for survival are degraded. Apart from these functions, cargoes like aggregated proteins, damaged organelles and intracellular pathogens, which are otherwise harmful to cells, are also selectively captured by autophagy and are destined for degradation. In terms of infectious diseases, pathogens are cleared by a specific form of autophagy known as xenophagy. This lysosomal mediated degradation of pathogens also increases the antigen presentation of cells thereby inducing a further immune response. The process of xenophagy provides a broad spectrum of defense mechanism to capture bacterial, viral and protozoan pathogens. However, pathogens have developed ingenious mechanisms to modulate xenophagy to enhance their intracellular survival. Meanwhile, certain pathogens also induce deleterious effects such as chronic inflammation and overexpression of oncogenes in the host system. This over time can increase the susceptibility of the host for tumorigenesis. Hence targeting tumor through anti-microbial mechanisms like xenophagy could be a novel strategy for combinatorial anti-cancer therapy. The recent developments in understanding the role of xenophagy in combating cancer causing pathogens will be discussed in this review.

Porcine Circovirus Type 2 ORF5 Protein Induces Autophagy to Promote Viral Replication via the PERK-eIF2α-ATF4 and mTOR-ERK1/2-AMPK Signaling Pathways in PK-15 Cells

Porcine circovirus type 2 (PCV2) is the primary causative agent that causing porcine circovirus-associated disease (PCVAD). The open reading frame 5 (ORF5) protein is a newly discovered non-structural protein in PCV2, which the function in viral pathogenesis remains unknown. The aim of this study was to investigate the mechanism of PCV2 ORF5 protein on autophagy and viral replication. The pEGFP-tagged ORF5 gene was ectopic expressed in PK-15 cells and an ORF5-deficient PCV2 mutant strain (PCV2^ΔORF5) were used to infected PK-15 cells. This study demonstrated that the ORF5 is essential for the of PCV2-induced autophagy. The ORF5 protein triggers the phosphorylation of PERK, eIF2α and the expression of downstream transcription factor ATF4. In addition, ORF5 protein activated the AMPK-ERK1/2-mTOR signaling pathways. These findings suggest that ORF5 play essential roles in the induction of autophagy by PCV2. We further revealed that PCV2 ORF5 promotes viral replication through PERK-eIF2α-ATF4 and AMPK-ERK1/2-mTOR pathways. In conclusion, we showed that PCV2 ORF5 induces autophagy to promote virus replication in PK-15 cells.

Hepatitis B subviral envelope particles use the COPII machinery for intracellular transport via selective exploitation of Sec24A and Sec23B

Hepatitis B virus (HBV) is a leading cause of liver disease. Its success as a human pathogen is related to the immense production of subviral envelope particles (SVPs) contributing to viral persistence by interfering with immune functions. To explore cellular pathways involved in SVP formation and egress, we investigated host-pathogen interactions. Yeast-based proteomics revealed Sec24A, a component of the coat protein complex II (COPII), as an interaction partner of the HBV envelope S domain. To understand how HBV co-opts COPII as a proviral machinery, we studied roles of key Sec proteins in HBV-expressing liver cells. Silencing of Sar1, Sec23, and Sec24, which promote COPII assembly concomitant with cargo loading, strongly diminished endoplasmic reticulum (ER) envelope export and SVP secretion. By analysing Sec paralog specificities, we unexpectedly found that the HBV envelope is a selective interaction partner of Sec24A and Sec23B whose functions could not be substituted by their related isoforms. In support, we found that HBV replication upregulated Sec24A and Sec23B transcription. Furthermore, HBV encountered the Sec24A/Sec23B complex via an interaction that involved the N-terminal half of Sec24A and a di-arginine motif of its S domain, mirroring a novel ER export code. Accordingly, an interference with the COPII/HBV cross-talk might display a tool to effectively inhibit SVP release.

Hepatitis Delta Virus Alters the Autophagy Process To Promote Its Genome Replication

A substantial number of viruses have been demonstrated to subvert autophagy to promote their own replication. Recent publications have reported the proviral effect of autophagy induction on hepatitis B virus (HBV) replication. Hepatitis delta virus (HDV) is a defective virus and an occasional obligate satellite of HBV. However, no previous work has studied the relationship between autophagy and HDV. In this article, we analyze the impact of HBV and HDV replication on autophagy as well as the involvement of the autophagy machinery in the HDV life cycle when produced alone and in combination with HBV. We prove that HBxAg and HBsAg can induce early steps of autophagy but ultimately block flux. It is worth noting that the two isoforms of the HDV protein, the small HDAg (S-HDAg) and large HDAg (L-HDAg) isoforms, can also efficiently promote autophagosome accumulation and disturb autophagic flux. Using CRISPR-Cas9 technology to generate specific knockouts, we demonstrate that the autophagy machinery, specifically the proteins implicated in the elongation step (ATG7, ATG5, and LC3), is important for the release of HBV without affecting the level of intracellular HBV genomes. Surprisingly, the knockout of ATG5 and ATG7 decreased the intracellular HDV RNA level in both Huh7 and HepG2.2.15 cells without an additional effect on HDV secretion. Therefore, we conclude that HBV and HDV have evolved to utilize the autophagy machinery so as to assist at different steps of their life cycle.IMPORTANCE Hepatitis delta virus is a defective RNA virus that requires hepatitis B virus envelope proteins (HBsAg) to fulfill its life cycle. Thus, HDV can only infect individuals at the same time as HBV (coinfection) or superinfect individuals who are already chronic carriers of HBV. The presence of HDV in the liver accelerates the progression of infection to fibrosis and to hepatic cancer. Since current treatments against HBV are ineffective against HDV, it is of paramount importance to study the interaction between HBV, HDV, and host factors. This will help unravel new targets whereby a therapy that is capable of simultaneously impeding both viruses could be developed. In this research paper, we evidence that the autophagy machinery promotes the replication of HBV and HDV at different steps of their life cycle. Notwithstanding their contribution to HBV release, autophagy proteins seem to assist HDV intracellular replication but not its secretion.

Autophagy in hepatic adaptation to stress

Autophagy is an evolutionarily ancient process whereby eukaryotic cells eliminate disposable or potentially dangerous cytoplasmic material, to support bioenergetic metabolism and adapt to stress. Accumulating evidence indicates that autophagy operates as a critical quality control mechanism for the maintenance of hepatic homeostasis in both parenchymal (hepatocytes) and non-parenchymal (stellate cells, sinusoidal endothelial cells, Kupffer cells) compartments. In line with this notion, insufficient autophagy has been aetiologically involved in the pathogenesis of multiple liver disorders, including alpha-1-antitrypsin deficiency, Wilson disease, non-alcoholic steatohepatitis, liver fibrosis and hepatocellular carcinoma. Here, we critically discuss the importance of functional autophagy for hepatic physiology, as well as the mechanisms whereby defects in autophagy cause liver disease.

Genetic association of polymorphisms at the intergenic region between PRDM1 and ATG5 with hepatitis B virus infection in Han Chinese patients

Chronic hepatitis B virus (HBV) infection is related to chronic hepatitis, cirrhosis, and hepatocellular carcinoma (HCC), and the interplay between the virus and host immune response leads to different outcomes of the infection. PR domain zinc finger protein 1 (PRDM1) and autophagy-related protein 5 (ATG5) are involved in immune response and HBV infection. An intergenic region between PRDM1 and ATG5 (PRDM1-ATG5 region) has been identified, and single-nucleotide polymorphisms (SNPs) in this region were shown to be involved in immune regulation. This study investigated the functionally relevant rs548234, rs6937876, and rs6568431 polymorphisms at the PRDM1-ATG5 region in a Han Chinese population (403 patients with chronic HBV infection [171 chronic hepatitis, 119 cirrhosis, and 113 HCC], 70 infection resolvers, and 196 healthy controls). The frequencies of the rs6568431 allele A in HBV patients (P = .005) and genotype CA in infection resolvers (P = .005) were significantly higher than in healthy controls. In the dominant model, HCC patients had significantly higher frequencies of rs548234 genotypes CC + TC than cirrhosis patients (P = .009). Rs548234 was an independent factor for HCC in comparison with either cirrhosis (P = .005) or all chronic HBV infection without HCC (P = .018). Functional annotation showed evidence of the role of the SNPs in gene regulation. In conclusion, through this study it is revealed for the first time that rs6568431 may be associated with susceptibility to HBV infection and that rs548234 may be associated with HCC risk in chronic HBV infection, supporting the presence of HBV-related disease-causing regulatory polymorphisms in the PRDM1-ATG5 intergenic region.

Grouper Atg12 negatively regulates the antiviral immune response against Singapore grouper iridovirus (SGIV) infection

Autophagy is an evolutionarily conserved, multi-step lysosomal degradation process used to maintain cell survival and homeostasis. A series of autophagy-related genes (Atgs) are involved in the autophagic pathway. In mammals, a growing number of studies have attributed functions to some Atgs that are distinct from their classical role in autophagosome biogenesis, such as resistance to pathogens. However, little is known about the functions of fish Atgs. In this study, we cloned and characterized an atg12 homolog from orange spotted grouper (Epinephelus coioides) (Ecatg12). Ecatg12 encodes a 117 amino acid protein that shares 94.0% and 76.8% identity with gourami (Anabas_testudineus) and humans (Homo sapiens), respectively. The transcription level of Ecatg12 was lower in cells infected with Singapore grouper iridovirus (SGIV) than in non-infected cells. Fluorescence microscopy revealed that EcAtg12 localized in the cytoplasm and nucleus in grouper spleen cells. Overexpression of EcAtg12 significantly increased the replication of SGIV, as evidenced by increased severity of the cytopathic effect, transcription levels of viral genes, levels of viral proteins, and progeny virus yield. Further studies showed that EcAtg12 overexpression decreased the expression levels of interferon (IFN) related molecules and pro-inflammatory factors and inhibited the promoter activity of IFN-3, interferon-stimulated response element, and nuclear factor-κB. Together, these results demonstrate that EcAtg12 plays crucial roles in SGIV replication by downregulating antiviral immune responses.

Harmonized Autophagy Versus Full-Fledged Hepatitis B Virus: Victorious or Defeated

Autophagy is a finely tuned process in the regulation of innate immunity to avoid excessive inflammatory responses and inflammasome signaling. In contrast, the results of recent studies have shown that autophagy may disease-dependently contribute to the pathogenesis of liver diseases, such as fibrosis, cirrhosis, and hepatocellular carcinoma (HCC) during hepatitis B virus (HBV) infection. HBV has learned to subvert the cell's autophagic machinery to promote its replication. Given the great impact of the autophagy mechanism on the HBV infection and HCC, recognizing these factors may be offered new hope for human intervention and treatment of chronic HBV. This review focuses on recent findings viewing the dual role of autophagy plays in the pathogenesis of HBV infected hepatocytes.

Autophagy modulation in bladder cancer development and treatment (Review)

Bladder cancer (BC) is a potentially life-threatening malignancy. Due to a high recurrence rate, frequent surveillance strategies and intravesical drug therapies, BC is considered one of the most expensive tumors to treat. As a fundamental evolutionary catabolic process, autophagy plays an important role in the maintenance of cellular environmental homeostasis by degrading and recycling damaged cytoplasmic components, including macromolecules and organelles. Scientific studies in the last two decades have shown that autophagy acts as a double-edged sword with regard to the treatment of cancer. On one hand, autophagy inhibition is able to increase the sensitivity of cancer cells to treatment, a process known as protective autophagy. On the other hand, autophagy overactivation may lead to cell death, referred to as autophagic cell death, similar to apoptosis. Therefore, it is essential to identify the role of autophagy in cancer cells in order to develop novel therapeutic agents. In addition, autophagy may potentially become a novel therapeutic target in human diseases. In this review, the current knowledge on autophagy modulation in BC development and treatment is summarized.

Treatment of Chronic Hepatitis B Virus Infection Using Small Molecule Modulators of Nucleocapsid Assembly: Recent Advances and Perspectives

On the basis of the recent advance of basic research on molecular biology of hepatitis B virus (HBV) infection, novel antiviral drugs targeting various steps of the HBV life cycle have been developed in recent years. HBV nucleocapsid assembly is now recognized as a hot target for anti-HBV drug development. Structural and functional analysis of HBV nucleocapsid allowed rational design and improvement of small molecules with the ability to interact with the components of HBV nucleocapsid and modulate the viral nucleocapsid assembly process. Prototypes of small molecule modulators targeting HBV nucleocapsid assembly are being preclinically tested or have moved forward in clinical trials, with promising results. This Review summarizes the recent advances in the approach to develop antiviral drugs based on the modulation of HBV nucleocapsid assembly. The antiviral mechanisms of small molecule modulators beyond the capsid formation and the potential implications will be discussed.

Autophagy-Related 5 Gene rs510432 Polymorphism Is Associated with Hepatocellular Carcinoma in Patients with Chronic Hepatitis B Virus Infection

BACKGROUND

Despite the identification of autophagy-related protein 5 (ATG5) as a molecule involved in the activated autophagy machinery during hepatitis B virus (HBV) infection and hepatocarcinogenesis, the consequences of ATG5 mutation carriage for patients with chronic HBV infection remain unclear. This study examined the association of ATG5 polymorphisms with HBV-related diseases including hepatocellular carcinoma (HCC).

PATIENTS AND METHODS

Two functionally relevant polymorphisms ATG5 rs573775 and rs510432 were genotyped by ligase detection reaction-polymerase chain reaction in 403 patients with chronic HBV infection (171 chronic hepatitis, 119 cirrhosis and 113 HCC) and 196 healthy controls. Univariate and multivariate logistic regression was performed to evaluate factors associated with HCC.

RESULTS

The rs573775 genotype and allele frequencies had no significant differences between patients with different clinical diseases. However, HCC patients had significantly higher frequency of rs510432 genotype AA (odds ratio [OR] 2.185, 95% confidence interval [CI] 1.042-4.581, P = 0.037, P value by Bonferroni correction [P_c] = 0.074) and allele A (OR 1.435, 95% CI 1.023-2.013, P_c = 0.036) than chronic hepatitis patients. In multivariate analyses, rs510432 allele A-containing genotypes (AA+GA) were independently associated with cirrhosis in comparison to chronic hepatitis (OR 1.927, 95%CI 1.011-3.017, P = 0.032). The rs510432 genotypes AA+GA were also independently associated with HCC in comparison to chronic hepatitis (OR 2.583, 95% CI 1.025-3.911, P = 0.006) or chronic HBV infection without HCC (OR 2.632, 95% CI 1.067-3.482, P = 0.032).

CONCLUSION

These results indicate that rs510432 genotypes AA+GA are associated with disease progression and HCC risk in chronic HBV infection, providing novel evidence for a role of ATG5 in the pathogenesis of HBV-related HCC.

ABBREVIATIONS

HBV: hepatitis B virus; HCC hepatocellular carcinoma; TNFSF10: tumor necrosis factor superfamily member 10; ATG5: autophagy-related protein 5; DNA: deoxyribonucleic acid; LDR-PCR: ligase detection reactions-polymerase chain reaction; PCR: polymerase chain reaction; SLE: systemic lupus erythematosus; BD: Behçet's disease; IL-10: interlukin-10; LPS: lipopolysaccharide; PBMC: peripheral blood mononuclear cells; CWP: coal workers' pneumoconiosis; TNF-α: tumor necrosis factor-α.