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Padarath K, Deroubaix A, Naicker P, Stoychev S, Kramvis A. Comparison of the Proteome of Huh7 Cells Transfected with Hepatitis B Virus Subgenotype A1, with or without G1862T. Curr Issues Mol Biol 2024; 46:7032-7047. [PMID: 39057060 PMCID: PMC11275860 DOI: 10.3390/cimb46070419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2024] [Revised: 07/01/2024] [Accepted: 07/03/2024] [Indexed: 07/28/2024] Open
Abstract
HBeAg is a non-structural, secreted protein of hepatitis B virus (HBV). Its p25 precursor is post-translationally modified in the endoplasmic reticulum. The G1862T precore mutation leads to the accumulation of P25 in the endoplasmic reticulum and activation of unfolded protein response. Using mass spectrometry, comparative proteome profiling of Huh-7 cells transfected with wildtype (WT) or G1862T revealed significantly differentially expressed proteins resulting in 12 dysregulated pathways unique to WT-transfected cells and 7 shared between cells transfected with either WT or G1862T. Except for the p38 MAPK signalling pathway, WT showed a higher number of DEPs than G1862T-transfected cells in all remaining six shared pathways. Two signalling pathways: oxidative stress and cell cycle signalling were differentially expressed only in cells transfected with G1862T. Fifteen pathways were dysregulated in G1862T-transfected cells compared to WT. The 15 dysregulated pathways were involved in the following processes: MAPK signalling, DNA synthesis and methylation, and extracellular matrix organization. Moreover, proteins involved in DNA synthesis signalling (replication protein A (RPA) and DNA primase (PRIM2)) were significantly upregulated in G1862T compared to WT. This upregulation was confirmed by mRNA quantification of both genes and immunofluorescent confocal microscopy for RPA only. The dysregulation of the pathways involved in these processes may lead to immune evasion, persistence, and uncontrolled proliferation, which are hallmarks of cancer.
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Affiliation(s)
- Kiyasha Padarath
- Hepatitis Virus Diversity Unit, Department of Internal Medicine, School of Clinical Medicine, Faculty of Health Science, University of Witwatersrand, 7 York Road, Johannesburg 2193, South Africa
| | - Aurélie Deroubaix
- Hepatitis Virus Diversity Unit, Department of Internal Medicine, School of Clinical Medicine, Faculty of Health Science, University of Witwatersrand, 7 York Road, Johannesburg 2193, South Africa
- Life Sciences Imaging Facility, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Johannesburg 2193, South Africa
| | - Previn Naicker
- Future Production Chemicals, Council for Scientific and Industrial Research, Pretoria 0001, South Africa;
| | - Stoyan Stoychev
- ReSyn Biosciences, Johannesburg 2194, South Africa;
- Evosep Biosystems, 5230 Odense, Denmark
| | - Anna Kramvis
- Hepatitis Virus Diversity Unit, Department of Internal Medicine, School of Clinical Medicine, Faculty of Health Science, University of Witwatersrand, 7 York Road, Johannesburg 2193, South Africa
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Padarath K, Deroubaix A, Kramvis A. The Complex Role of HBeAg and Its Precursors in the Pathway to Hepatocellular Carcinoma. Viruses 2023; 15:v15040857. [PMID: 37112837 PMCID: PMC10144019 DOI: 10.3390/v15040857] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 03/23/2023] [Accepted: 03/24/2023] [Indexed: 03/30/2023] Open
Abstract
Hepatitis B virus (HBV) is one of the seven known human oncogenic viruses and has adapted to coexist with a single host for prolonged periods, requiring continuous manipulation of immunity and cell fate decisions. The persistence of HBV infection is associated with the pathogenesis of hepatocellular carcinoma, and various HBV proteins have been implicated in promoting this persistence. The precursor of hepatitis e antigen (HBeAg), is translated from the precore/core region and is post-translationally modified to yield HBeAg, which is secreted in the serum. HBeAg is a non-particulate protein of HBV and can act as both a tolerogen and an immunogen. HBeAg can protect hepatocytes from apoptosis by interfering with host signalling pathways and acting as a decoy to the immune response. By evading the immune response and interfering with apoptosis, HBeAg has the potential to contribute to the hepatocarcinogenic potential of HBV. In particular, this review summarises the various signalling pathways through which HBeAg and its precursors can promote hepatocarcinogenesis via the various hallmarks of cancer.
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Characterization of Intracellular Precore-Derived Proteins and Their Functions in Hepatitis B Virus-Infected Human Hepatocytes. mBio 2023; 14:e0350122. [PMID: 36715515 PMCID: PMC9973328 DOI: 10.1128/mbio.03501-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Hepatitis B virus (HBV) precore protein is not essential for viral replication but is thought to facilitate chronic infection. In addition to the secreted precore products, including the hepatitis B e antigen (HBeAg) and PreC protein, intracellular precore-derived proteins in HBV-infected human hepatocytes remain poorly characterized, and their roles, if any, remain largely unknown. Here, we detected multiple precore derivatives, including the nonprocessed precursor p25 and the processing intermediate p22, in HBV-infected human hepatocytes as well as human hepatoma cells overexpressing the HBV precore protein. Both p25 and p22 showed phosphorylated and unphosphorylated forms, which were located in different intracellular compartments. Interestingly, precore expression was associated with decreases in intracellular HBV core protein (HBc) and secreted DNA-containing virions but was also associated with an increase in secreted empty virions. The decrease in HBc by precore could be attributed to cytosolic p22, which caused HBc degradation, at least in part by the proteasome, and consequently decreased HBV pregenomic RNA packaging and DNA synthesis. In addition, cytosolic p22 formed chimeric capsids with HBc in the cell, which were further secreted in virions. In contrast, the PreC antigen, like HBeAg, was secreted via the endoplasmic reticulum (ER)-Golgi secretory pathway and was thus unable to form capsids in the cell or be secreted in virions. Furthermore, p25, as well as p22, were secreted in virions from HBV-infected human hepatocytes and were detected in the sera of HBV-infected chimpanzees. In summary, we have detected multiple intracellular precore-derived proteins in HBV-infected human hepatocytes and revealed novel precore functions in the viral life cycle. IMPORTANCE Chronic hepatitis B remains a worldwide public health issue. The hepatitis B virus (HBV) precore protein is not essential for HBV replication but may facilitate viral persistence. In this study, we have detected multiple precore protein species in HBV-infected human hepatocytes and studied their functions in the HBV life cycle. We found that the HBV precore proteins decreased intracellular HBV core protein and reduced secretion of complete virions but enhanced secretion of empty virions. Interestingly, the cytosolic precore protein species formed chimeric capsids with the core protein and were secreted in virions. Our results shed new light on the functions of intracellular precore protein species in the HBV life cycle and have implications for the roles of precore proteins in HBV persistence and pathogenesis.
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Maepa MB, Ely A, Kramvis A, Bloom K, Naidoo K, Simani OE, Maponga TG, Arbuthnot P. Hepatitis B Virus Research in South Africa. Viruses 2022; 14:v14091939. [PMID: 36146747 PMCID: PMC9503375 DOI: 10.3390/v14091939] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 08/11/2022] [Accepted: 08/26/2022] [Indexed: 11/18/2022] Open
Abstract
Despite being vaccine-preventable, hepatitis B virus (HBV) infection remains the seventh leading cause of mortality in the world. In South Africa (SA), over 1.9 million people are chronically infected with HBV, and 70% of all Black chronic carriers are infected with HBV subgenotype A1. The virus remains a significant burden on public health in SA despite the introduction of an infant immunization program implemented in 1995 and the availability of effective treatment for chronic HBV infection. In addition, the high prevalence of HIV infection amplifies HBV replication, predisposes patients to chronicity, and complicates management of the infection. HBV research has made significant progress leading to better understanding of HBV epidemiology and management challenges in the SA context. This has led to recent revision of the national HBV infection management guidelines. Research on developing new vaccines and therapies is underway and progress has been made with designing potentially curative gene therapies against HBV. This review summarizes research carried out in SA on HBV molecular biology, epidemiology, treatment, and vaccination strategies.
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Affiliation(s)
- Mohube B. Maepa
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Faculty of Health Sciences, Infectious Diseases and Oncology Research Institute (IDORI), University of the Witwatersrand, Johannesburg 2000, South Africa
- Correspondence:
| | - Abdullah Ely
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Faculty of Health Sciences, Infectious Diseases and Oncology Research Institute (IDORI), University of the Witwatersrand, Johannesburg 2000, South Africa
| | - Anna Kramvis
- Hepatitis Diversity Research Unit, Department of Internal Medicine, Faculty of Health Sciences, School of Clinical Medicine, University of the Witwatersrand, Johannesburg 2000, South Africa
| | - Kristie Bloom
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Faculty of Health Sciences, Infectious Diseases and Oncology Research Institute (IDORI), University of the Witwatersrand, Johannesburg 2000, South Africa
| | - Kubendran Naidoo
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Faculty of Health Sciences, Infectious Diseases and Oncology Research Institute (IDORI), University of the Witwatersrand, Johannesburg 2000, South Africa
- National Health Laboratory Service, Johannesburg 2000, South Africa
| | - Omphile E. Simani
- HIV and Hepatitis Research Unit, Department of Virology, Sefako Makgatho Health Sciences University, Pretoria 0204, South Africa
| | - Tongai G. Maponga
- Division of Medical Virology, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town 7602, South Africa
| | - Patrick Arbuthnot
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Faculty of Health Sciences, Infectious Diseases and Oncology Research Institute (IDORI), University of the Witwatersrand, Johannesburg 2000, South Africa
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Zábranská H, Zábranský A, Lubyová B, Hodek J, Křenková A, Hubálek M, Weber J, Pichová I. Biogenesis of hepatitis B virus e antigen is driven by translocon-associated protein complex and regulated by conserved cysteine residues within its signal peptide sequence. FEBS J 2021; 289:2895-2914. [PMID: 34839586 PMCID: PMC9300162 DOI: 10.1111/febs.16304] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 10/27/2021] [Accepted: 11/26/2021] [Indexed: 11/28/2022]
Abstract
Hepatitis B virus uses e antigen (HBe), which is dispensable for virus infectivity, to modulate host immune responses and achieve viral persistence in human hepatocytes. The HBe precursor (p25) is directed to the endoplasmic reticulum (ER), where cleavage of the signal peptide (sp) gives rise to the first processing product, p22. P22 can be retro-translocated back to the cytosol or enter the secretory pathway and undergo a second cleavage event, resulting in secreted p17 (HBe). Here, we report that translocation of p25 to the ER is promoted by translocon-associated protein complex. We have found that p25 is not completely translocated into the ER; a fraction of p25 is phosphorylated and remains in the cytoplasm and nucleus. Within the p25 sp sequence, we have identified three cysteine residues that control the efficiency of sp cleavage and contribute to proper subcellular distribution of the precore pool.
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Affiliation(s)
- Helena Zábranská
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague, Czech Republic
| | - Aleš Zábranský
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague, Czech Republic
| | - Barbora Lubyová
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague, Czech Republic
| | - Jan Hodek
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague, Czech Republic
| | - Alena Křenková
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague, Czech Republic
| | - Martin Hubálek
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague, Czech Republic
| | - Jan Weber
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague, Czech Republic
| | - Iva Pichová
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague, Czech Republic
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