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Su PY, Yen SCB, Yang CC, Chang CH, Lin WC, Shih C. Hepatitis B virus virion secretion is a CRM1-spike-mediated late event. J Biomed Sci 2022; 29:44. [PMID: 35729569 PMCID: PMC9210616 DOI: 10.1186/s12929-022-00827-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2022] [Accepted: 06/16/2022] [Indexed: 11/10/2022] Open
Abstract
Background Hepatitis B virus (HBV) is a major human pathogen worldwide. To date, there is no curative treatment for chronic hepatitis B. The mechanism of virion secretion remains to be investigated. Previously, we found that nuclear export of HBc particles can be facilitated via two CRM1-specific nuclear export signals (NES) at the spike tip. Methods In this study, we used site-directed mutagenesis at the CRM1 NES, as well as treatment with CRM1 inhibitors at a low concentration, or CRM1-specific shRNA knockdown, in HBV-producing cell culture, and measured the secretion of various HBV viral and subviral particles via a native agarose gel electrophoresis assay. Separated HBV particles were characterized by Western blot analysis, and their genomic DNA contents were measured by Southern blot analysis. Secreted extracellular particles were compared with intracellular HBc capsids for DNA synthesis and capsid formation. Virion secretion and the in vivo interactions among HBc capsids, CRM1 and microtubules, were examined by proximity ligation assay, immunofluorescence microscopy, and nocodazole treatment. Results We report here that the tip of spike of HBV core (HBc) particles (capsids) contains a complex sensor for secretion of both HBV virions and naked capsids. HBV virion secretion is closely associated with HBc nuclear export in a CRM1-dependent manner. At the conformationally flexible spike tips of HBc particles, NES motifs overlap extensively with motifs important for secretion of HBV virions and naked capsids. Conclusions We provided experimental evidence that virions and naked capsids can egress via two distinct, yet overlapping, pathways. Unlike the secretion of naked capsids, HBV virion secretion is highly CRM1- and microtubule-dependent. CRM1 is well known for its involvement in nuclear transport in literature. To our knowledge, this is the first report that CRM1 is required for virion secretion. CRM1 inhibitors could be a promising therapeutic candidate for chronic HBV patients in clinical medicine. Supplementary Information The online version contains supplementary material available at 10.1186/s12929-022-00827-w.
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Affiliation(s)
- Pei-Yi Su
- Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, No.100, Shih-Chuan 1st Road, Sanmin, 80708, Kaohsiung, Taiwan.,Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Shin-Chwen Bruce Yen
- Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, No.100, Shih-Chuan 1st Road, Sanmin, 80708, Kaohsiung, Taiwan.,Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Ching-Chun Yang
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Chih-Hsu Chang
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.,Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Wen-Chang Lin
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Chiaho Shih
- Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, No.100, Shih-Chuan 1st Road, Sanmin, 80708, Kaohsiung, Taiwan. .,Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
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Chang CH, Chou SF, Shih C. A nuanced role of the small loop of hepatitis B virus small envelope protein in virion morphogenesis and secretion. J Biomed Sci 2021; 28:82. [PMID: 34852809 PMCID: PMC8638367 DOI: 10.1186/s12929-021-00780-0] [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: 07/13/2021] [Accepted: 11/23/2021] [Indexed: 01/16/2023] Open
Abstract
BACKGROUND The virion secretion mechanism of human hepatitis B virus (HBV) remains to be investigated. In our current study, we characterized a reverse transcriptase mutant, which changed from the YMDD motif to YMHA. We noted that this mutant YMHA secreted no virions in the medium. Because of the overlapping open reading frame (ORF) between the polymerase and the envelope genes, the lack of virion secretion is likely due to corresponding concurrent mutations in a small loop of the envelope protein (HBsAg, HBV surface antigen). In literature, small loop mutations are thought to affect virion secretion of hepatitis delta virus (HDV), but not HBV. METHODS Here, we revisited the relationship between the small loop and virion secretion by site-directed mutagenesis and native agarose gel electrophoresis. RESULTS A proline substitution at residue 196 or 198 in the small loop blocked both HBV genome-containing and genome-free virion secretion, but not the secretion of 22-nm HBsAg subviral particles. Surprisingly, a leucine substitution at residue 196 enhanced genome-containing virion secretion. It is also intriguing that a proline-197, sandwiched by residue 196 and 198, exhibited no apparent defect in secreted virions, with or without containing an HBV genome. By complementation assay, we demonstrated that the wild type small envelope protein alone is sufficient to rescue the virion secretion defect of a small loop mutant M198P. CONCLUSIONS The effect of the small loop mutation of HBV small envelope protein on virion secretion is position-dependent. It warrants further investigation how the small loop of HBsAg plays a subtle role in HBV morphogenesis and secretion of virions with or without containing an HBV genome.
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Affiliation(s)
- Chih-Hsu Chang
- Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan.,Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Shu-Fan Chou
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
| | - Chiaho Shih
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan. .,Graduate Institute of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
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Honda T, Yamada N, Murayama A, Shiina M, Aly HH, Kato A, Ito T, Ishizu Y, Kuzuya T, Ishigami M, Murakami Y, Tanaka T, Moriishi K, Nishitsuji H, Shimotohno K, Ishikawa T, Fujishiro M, Muramatsu M, Wakita T, Kato T. Amino Acid Polymorphism in Hepatitis B Virus Associated With Functional Cure. Cell Mol Gastroenterol Hepatol 2021; 12:1583-1598. [PMID: 34352407 PMCID: PMC8536788 DOI: 10.1016/j.jcmgh.2021.07.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 07/23/2021] [Accepted: 07/26/2021] [Indexed: 12/12/2022]
Abstract
BACKGROUND & AIMS To provide an adequate treatment strategy for chronic hepatitis B, it is essential to know which patients are expected to have a good prognosis and which patients do not require therapeutic intervention. Previously, we identified the substitution of isoleucine to leucine at amino acid 97 (I97L) in the hepatitis B core region as a key predictor among patients with stable hepatitis. In this study, we attempted to identify the point at which I97L affects the hepatitis B virus (HBV) life cycle and to elucidate the underlying mechanisms governing the stabilization of hepatitis. METHODS To confirm the clinical features of I97L, we used a cohort of hepatitis B e antigen-negative patients with chronic hepatitis B infected with HBV-I97 wild-type (wt) or HBV-I97L. The effects of I97L on viral characteristics were evaluated by in vitro HBV production and infection systems with the HBV reporter virus and cell culture-generated HBV. RESULTS The ratios of reduction in hepatitis B surface antigen and HBV DNA were higher in patients with HBV-I97L than in those with HBV-I97wt. HBV-I97L exhibited lower infectivity than HBV-I97wt in both infection systems with reporter HBV and cell culture-generated HBV. HBV-I97L virions exhibiting low infectivity primarily contained a single-stranded HBV genome. The lower efficiency of cccDNA synthesis was demonstrated after infection of HBV-I97L or transfection of the molecular clone of HBV-I97L. CONCLUSIONS The I97L substitution reduces the level of cccDNA through the generation of immature virions with single-stranded genomes. This I97L-associated low efficiency of cccDNA synthesis may be involved in the stabilization of hepatitis.
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Affiliation(s)
- Takashi Honda
- Department of Gastroenterology and Hepatology, Nagoya University Graduate School of Medicine, Nagoya
| | - Norie Yamada
- Department of Virology II, National Institute of Infectious Diseases, Tokyo
| | - Asako Murayama
- Department of Virology II, National Institute of Infectious Diseases, Tokyo
| | - Masaaki Shiina
- Department of Virology II, National Institute of Infectious Diseases, Tokyo
| | - Hussein Hassan Aly
- Department of Virology II, National Institute of Infectious Diseases, Tokyo
| | - Asuka Kato
- Department of Gastroenterology and Hepatology, Nagoya University Graduate School of Medicine, Nagoya
| | - Takanori Ito
- Department of Gastroenterology and Hepatology, Nagoya University Graduate School of Medicine, Nagoya
| | - Yoji Ishizu
- Department of Gastroenterology and Hepatology, Nagoya University Graduate School of Medicine, Nagoya
| | - Teiji Kuzuya
- Department of Gastroenterology and Hepatology, Nagoya University Graduate School of Medicine, Nagoya
| | - Masatoshi Ishigami
- Department of Gastroenterology and Hepatology, Nagoya University Graduate School of Medicine, Nagoya
| | - Yoshiki Murakami
- Department of Molecular Pathology, Tokyo Medical University, Tokyo
| | - Tomohisa Tanaka
- Department of Microbiology, Graduate School of Medicine, University of Yamanashi, Yamanashi
| | - Kohji Moriishi
- Department of Microbiology, Graduate School of Medicine, University of Yamanashi, Yamanashi
| | - Hironori Nishitsuji
- Genome Medical Sciences Project, National Center for Global Health and Medicine, Ichikawa, Japan
| | - Kunitada Shimotohno
- Genome Medical Sciences Project, National Center for Global Health and Medicine, Ichikawa, Japan
| | - Tetsuya Ishikawa
- Department of Gastroenterology and Hepatology, Nagoya University Graduate School of Medicine, Nagoya
| | - Mitsuhiro Fujishiro
- Department of Gastroenterology and Hepatology, Nagoya University Graduate School of Medicine, Nagoya
| | | | - Takaji Wakita
- Department of Virology II, National Institute of Infectious Diseases, Tokyo
| | - Takanobu Kato
- Department of Virology II, National Institute of Infectious Diseases, Tokyo,Correspondence Address correspondence to: Takanobu Kato, MD, PhD, Toyama 1-23-1, Shinjuku-ku, Tokyo 162-8640, Japan. fax: +81-3-5285-1161.
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Shih C, Wu SY, Chou SF, Yuan TTT. Virion Secretion of Hepatitis B Virus Naturally Occurring Core Antigen Variants. Cells 2020; 10:cells10010043. [PMID: 33396864 PMCID: PMC7823318 DOI: 10.3390/cells10010043] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2020] [Revised: 12/21/2020] [Accepted: 12/28/2020] [Indexed: 02/07/2023] Open
Abstract
In natural infection, hepatitis B virus (HBV) core protein (HBc) accumulates frequent mutations. The most frequent HBc variant in chronic hepatitis B patients is mutant 97L, changing from an isoleucine or phenylalanine to a leucine (L) at HBc amino acid 97. One dogma in the HBV research field is that wild type HBV secretes predominantly virions containing mature double-stranded DNA genomes. Immature genomes, containing single-stranded RNA or DNA, do not get efficiently secreted until reaching genome maturity. Interestingly, HBc variant 97L does not follow this dogma in virion secretion. Instead, it exhibits an immature secretion phenotype, which preferentially secretes virions containing immature genomes. Other aberrant behaviors in virion secretion were also observed in different naturally occurring HBc variants. A hydrophobic pocket around amino acid 97 was identified by bioinformatics, genetic analysis, and cryo-EM. We postulated that this hydrophobic pocket could mediate the transduction of the genome maturation signal for envelopment from the capsid interior to its surface. Virion morphogenesis must involve interactions between HBc, envelope proteins (HBsAg) and host factors, such as components of ESCRT (endosomal sorting complex required for transport). Immature secretion can be offset by compensatory mutations, occurring at other positions in HBc or HBsAg. Recently, we demonstrated in mice that the persistence of intrahepatic HBV DNA is related to virion secretion regulated by HBV genome maturity. HBV virion secretion could be an antiviral drug target.
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Affiliation(s)
- Chiaho Shih
- Graduate Institute of Medicine, Kaohsiung Medical University, Kaohsiung 80708, Taiwan
- Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan
- Correspondence: (C.S.); (T.-T.T.Y.)
| | - Szu-Yao Wu
- Chimera Bioscience Inc., No. 18 Siyuan St., Zhongzheng Dist., Taipei 10087, Taiwan;
| | - Shu-Fan Chou
- Department of Microbiology, Harvard Medical School, Boston, MA 02115, USA;
| | - Ta-Tung Thomas Yuan
- TFBS Bioscience, Inc. 3F, No. 103, Ln 169, Kangning St., Xizhi Dist., New Taipei City 221, Taiwan
- Correspondence: (C.S.); (T.-T.T.Y.)
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In silico Analysis of Genetic Diversity of Human Hepatitis B Virus in Southeast Asia, Australia and New Zealand. Viruses 2020; 12:v12040427. [PMID: 32283837 PMCID: PMC7232418 DOI: 10.3390/v12040427] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 04/06/2020] [Accepted: 04/08/2020] [Indexed: 02/08/2023] Open
Abstract
The extent of whole genome diversity amongst hepatitis B virus (HBV) genotypes is not well described. This study aimed to update the current distribution of HBV types and to investigate mutation rates and nucleotide diversity between genotypes in Southeast Asia, Australia and New Zealand. We retrieved 930 human HBV complete genomes from these regions from the NCBI nucleotide database for genotyping, detection of potential recombination, serotype prediction, mutation identification and comparative genome analyses. Overall, HBV genotypes B (44.1%) and C (46.2%) together with predicted serotypes adr (36%), adw2 (29%) and ayw1 (19.9%) were the most commonly circulating HBV types in the studied region. The three HBV variants identified most frequently were p.V5L, c.1896G>A and double mutation c.1762A>T/c.1764G>A, while genotypes B and C had the widest range of mutation types. The study also highlighted the distinct nucleotide diversity of HBV genotypes for whole genome and along the genome length. Therefore, this study provided a robust update to HBV currently circulating in Southeast Asia, Australia and New Zealand as well as an insight into the association of HBV genetic hypervariability and prevalence of well reported mutations.
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