1
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Khare S, Villalba MI, Canul-Tec JC, Cajiao AB, Kumar A, Backovic M, Rey FA, Pardon E, Steyaert J, Perez C, Reyes N. Receptor-recognition and antiviral mechanisms of retrovirus-derived human proteins. Nat Struct Mol Biol 2024:10.1038/s41594-024-01295-6. [PMID: 38671230 DOI: 10.1038/s41594-024-01295-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Accepted: 03/26/2024] [Indexed: 04/28/2024]
Abstract
Human syncytin-1 and suppressyn are cellular proteins of retroviral origin involved in cell-cell fusion events to establish the maternal-fetal interface in the placenta. In cell culture, they restrict infections from members of the largest interference group of vertebrate retroviruses, and are regarded as host immunity factors expressed during development. At the core of the syncytin-1 and suppressyn functions are poorly understood mechanisms to recognize a common cellular receptor, the membrane transporter ASCT2. Here, we present cryo-electron microscopy structures of human ASCT2 in complexes with the receptor-binding domains of syncytin-1 and suppressyn. Despite their evolutionary divergence, the two placental proteins occupy similar positions in ASCT2, and are stabilized by the formation of a hybrid β-sheet or 'clamp' with the receptor. Structural predictions of the receptor-binding domains of extant retroviruses indicate overlapping binding interfaces and clamping sites with ASCT2, revealing a competition mechanism between the placental proteins and the retroviruses. Our work uncovers a common ASCT2 recognition mechanism by a large group of endogenous and disease-causing retroviruses, and provides high-resolution views on how placental human proteins exert morphological and immunological functions.
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Affiliation(s)
- Shashank Khare
- Fundamental Microbiology and Pathogenicity Unit, CNRS, Université de Bordeaux, IECB, Bordeaux, France
| | - Miryam I Villalba
- Fundamental Microbiology and Pathogenicity Unit, CNRS, Université de Bordeaux, IECB, Bordeaux, France
| | - Juan C Canul-Tec
- Fundamental Microbiology and Pathogenicity Unit, CNRS, Université de Bordeaux, IECB, Bordeaux, France
| | | | - Anand Kumar
- Fundamental Microbiology and Pathogenicity Unit, CNRS, Université de Bordeaux, IECB, Bordeaux, France
| | - Marija Backovic
- Institut Pasteur, Université Paris Cité, CNRS UMR3569, Unité de Virologie Structurale, Paris, France
| | - Felix A Rey
- Institut Pasteur, Université Paris Cité, CNRS UMR3569, Unité de Virologie Structurale, Paris, France
| | - Els Pardon
- Structural Biology Brussels, Vrije Universiteit Brussel, VUB, Brussels, Belgium
- VIB-VUB Center for Structural Biology, VIB, Brussels, Belgium
| | - Jan Steyaert
- Structural Biology Brussels, Vrije Universiteit Brussel, VUB, Brussels, Belgium
- VIB-VUB Center for Structural Biology, VIB, Brussels, Belgium
| | - Camilo Perez
- Biozentrum, University of Basel, Basel, Switzerland.
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, USA.
| | - Nicolas Reyes
- Fundamental Microbiology and Pathogenicity Unit, CNRS, Université de Bordeaux, IECB, Bordeaux, France.
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2
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Kang BK, Jung YT. A Replication-Competent Retroviral Vector Expressing the HERV-W Envelope Glycoprotein is a Potential Tool for Cancer Gene Therapy. J Microbiol Biotechnol 2024; 34:280-288. [PMID: 38247210 PMCID: PMC10940750 DOI: 10.4014/jmb.2309.09022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 11/07/2023] [Accepted: 11/22/2023] [Indexed: 01/23/2024]
Abstract
The fusogenic membrane glycoprotein (FMG) derived from the human endogenous retrovirus-W (HERV-W) exhibits fusogenic properties, making it a promising candidate for cancer gene therapy. When cells are transfected with HERV-W FMG, they can fuse with neighboring cells expressing the receptor, resulting in the formation of syncytia. These syncytia eventually undergo cell death within a few days. In addition, it has been observed that an HERV-W env mutant, which is truncated after amino acid 483, displays increased fusogenicity compared to the wild-type HERV-W env. In this study, we observed syncytium formation upon transfection of HeLa and TE671 human cancer cells with plasmids containing the HERV-W 483 gene. To explore the potential of a semi-replication-competent retroviral (s-RCR) vector encoding HERV-W 483 for FMG-mediated cancer gene therapy, we developed two replication-defective retroviral vectors: a gag-pol vector encoding HERV-W 483 (MoMLV-HERV-W 483) and an env vector encoding VSV-G (pCLXSN-VSV-G-EGFP). When MoMLV-HERV-W 483 and pCLXSN-VSV-G-EGFP were co-transfected into HEK293T cells to produce the s-RCR vector, gradual syncytium formation was observed. However, the titers of the s-RCR virus remained consistently low. To enhance gene transfer efficiency, we constructed an RCR vector encoding HERV-W 483 (MoMLV-10A1-HERV-W 483), which demonstrated replication ability in HEK293T cells. Infection of A549 and HT1080 human cancer cell lines with this RCR vector induced syncytium formation and subsequent cell death. Consequently, both the s-RCR vector and RCR encoding HERV-W 483 hold promise as valuable tools for cancer gene therapy.
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Affiliation(s)
- Byoung Kwon Kang
- Department of Microbiology, Dankook University, Cheonan 31116, Republic of Korea
| | - Yong-Tae Jung
- Department of Microbiology, Dankook University, Cheonan 31116, Republic of Korea
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3
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Noubissi FK, Odubanjo OV, Ogle BM, Tchounwou PB. Mechanisms of Cell Fusion in Cancer. Results Probl Cell Differ 2024; 71:407-432. [PMID: 37996688 PMCID: PMC10893907 DOI: 10.1007/978-3-031-37936-9_19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2023]
Abstract
Cell-cell fusion is a normal physiological mechanism that requires a well-orchestrated regulation of intracellular and extracellular factors. Dysregulation of this process could lead to diseases such as osteoporosis, malformation of muscles, difficulties in pregnancy, and cancer. Extensive literature demonstrates that fusion occurs between cancer cells and other cell types to potentially promote cancer progression and metastasis. However, the mechanisms governing this process in cancer initiation, promotion, and progression are less well-studied. Fusogens involved in normal physiological processes such as syncytins and associated factors such as phosphatidylserine and annexins have been observed to be critical in cancer cell fusion as well. Some of the extracellular factors associated with cancer cell fusion include chronic inflammation and inflammatory cytokines, hypoxia, and viral infection. The interaction between these extracellular factors and cell's intrinsic factors potentially modulates actin dynamics to drive the fusion of cancer cells. In this review, we have discussed the different mechanisms that have been identified or postulated to drive cancer cell fusion.
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Affiliation(s)
- Felicite K Noubissi
- Department of Biology, Jackson State University, Jackson, MS, USA.
- Research Centers in Minority Institutions (RCMI), Center for Health Disparity Research (RCMI-CHDR), Jackson State University, Jackson, MS, USA.
| | - Oluwatoyin V Odubanjo
- Department of Biology, Jackson State University, Jackson, MS, USA
- Research Centers in Minority Institutions (RCMI), Center for Health Disparity Research (RCMI-CHDR), Jackson State University, Jackson, MS, USA
| | - Brenda M Ogle
- Department of Biomedical Engineering, University of Minnesota-Twin Cities, Minneapolis, MN, USA
- Department of Pediatrics, University of Minnesota-Twin Cities, Minneapolis, MN, USA
- Stem Cell Institute, University of Minnesota-Twin Cities, Minneapolis, MN, USA
| | - Paul B Tchounwou
- Department of Biology, Jackson State University, Jackson, MS, USA
- Research Centers in Minority Institutions (RCMI), Center for Health Disparity Research (RCMI-CHDR), Jackson State University, Jackson, MS, USA
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4
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Katoh H, Honda T. Roles of Human Endogenous Retroviruses and Endogenous Virus-Like Elements in Cancer Development and Innate Immunity. Biomolecules 2023; 13:1706. [PMID: 38136578 PMCID: PMC10741599 DOI: 10.3390/biom13121706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2023] [Revised: 11/18/2023] [Accepted: 11/21/2023] [Indexed: 12/24/2023] Open
Abstract
Human endogenous retroviruses (HERVs) are remnants of ancient retroviral infections in the host genome. Although mutations and silencing mechanisms impair their original role in viral replication, HERVs are believed to play roles in various biological processes. Long interspersed nuclear elements (LINEs) are non-LTR retrotransposons that have a lifecycle resembling that of retroviruses. Although LINE expression is typically silenced in somatic cells, it also contributes to various biological processes. The aberrant expression of HERVs and LINEs is closely associated with the development of cancer and/or immunological diseases, suggesting that they are integrated into various pathways related to the diseases. HERVs/LINEs control gene expression depending on the context as promoter/enhancer elements. Some RNAs and proteins derived from HERVs/LINEs have oncogenic potential, whereas others stimulate innate immunity. Non-retroviral endogenous viral elements (nrEVEs) are a novel type of virus-like element in the genome. nrEVEs may also be involved in host immunity. This article provides a current understanding of how these elements impact cellular physiology in cancer development and innate immunity, and provides perspectives for future studies.
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Affiliation(s)
- Hirokazu Katoh
- Department of Virology, Faculty of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama 700-8558, Japan;
| | - Tomoyuki Honda
- Department of Virology, Faculty of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama 700-8558, Japan;
- Department of Virology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8558, Japan
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5
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Shimode S. Acquisition and Exaptation of Endogenous Retroviruses in Mammalian Placenta. Biomolecules 2023; 13:1482. [PMID: 37892164 PMCID: PMC10604696 DOI: 10.3390/biom13101482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 10/02/2023] [Accepted: 10/03/2023] [Indexed: 10/29/2023] Open
Abstract
Endogenous retroviruses (ERVs) are retrovirus-like sequences that were previously integrated into the host genome. Although most ERVs are inactivated by mutations, deletions, or epigenetic regulation, some remain transcriptionally active and impact host physiology. Several ERV-encoded proteins, such as Syncytins and Suppressyn, contribute to placenta acquisition, a crucial adaptation in mammals that protects the fetus from external threats and other risks while enabling the maternal supply of oxygen, nutrients, and antibodies. In primates, Syncytin-1 and Syncytin-2 facilitate cell-cell fusion for placental formation. Suppressyn is the first ERV-derived protein that inhibits cell fusion by binding to ASCT2, the receptor for Syncytin-1. Furthermore, Syncytin-2 likely inserted into the genome of the common ancestor of Anthropoidea, whereas Syncytin-1 and Suppressyn likely inserted into the ancestor of catarrhines; however, they were inactivated in some lineages, suggesting that multiple exaptation events had occurred. This review discusses the role of ERV-encoded proteins, particularly Syncytins and Suppressyn, in placental development and function, focusing on the integration of ERVs into the host genome and their contribution to the genetic mechanisms underlying placentogenesis. This review provides valuable insights into the molecular and genetic aspects of placentation, potentially shedding light on broader evolutionary and physiological processes in mammals.
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Affiliation(s)
- Sayumi Shimode
- Genome Editing Innovation Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-0046, Japan;
- Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526, Japan
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6
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Przybyszewska-Podstawka A, Czapiński J, Kałafut J, Rivero-Müller A. Synthetic circuits based on split Cas9 to detect cellular events. Sci Rep 2023; 13:14988. [PMID: 37696879 PMCID: PMC10495424 DOI: 10.1038/s41598-023-41367-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Accepted: 08/25/2023] [Indexed: 09/13/2023] Open
Abstract
Synthetic biology involves the engineering of logic circuit gates that process different inputs to produce specific outputs, enabling the creation or control of biological functions. While CRISPR has become the tool of choice in molecular biology due to its RNA-guided targetability to other nucleic acids, it has not been frequently applied to logic gates beyond those controlling the guide RNA (gRNA). In this study, we present an adaptation of split Cas9 to generate logic gates capable of sensing biological events, leveraging a Cas9 reporter (EGxxFP) to detect occurrences such as cancer cell origin, epithelial to mesenchymal transition (EMT), and cell-cell fusion. First, we positioned the complementing halves of split Cas9 under different promoters-one specific to cancer cells of epithelial origin (phCEA) and the other a universal promoter. The use of self-assembling inteins facilitated the reconstitution of the Cas9 halves. Consequently, only cancer cells with an epithelial origin activated the reporter, exhibiting green fluorescence. Subsequently, we explored whether this system could detect biological processes such as epithelial to mesenchymal transition (EMT). To achieve this, we designed a logic gate where one half of Cas9 is expressed under the phCEA, while the other is activated by TWIST1. The results showed that cells undergoing EMT effectively activated the reporter. Next, we combined the two inputs (epithelial origin and EMT) to create a new logic gate, where only cancer epithelial cells undergoing EMT activated the reporter. Lastly, we applied the split-Cas9 logic gate as a sensor of cell-cell fusion, both in induced and naturally occurring scenarios. Each cell type expressed one half of split Cas9, and the induction of fusion resulted in the appearance of multinucleated syncytia and the fluorescent reporter. The simplicity of the split Cas9 system presented here allows for its integration into various cellular processes, not only as a sensor but also as an actuator.
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Affiliation(s)
| | - Jakub Czapiński
- Department of Biochemistry and Molecular Biology, Medical University of Lublin, 20-093, Lublin, Poland
| | - Joanna Kałafut
- Department of Biochemistry and Molecular Biology, Medical University of Lublin, 20-093, Lublin, Poland
| | - Adolfo Rivero-Müller
- Department of Biochemistry and Molecular Biology, Medical University of Lublin, 20-093, Lublin, Poland.
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7
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Gholami Barzoki M, Shatizadeh Malekshahi S, Heydarifard Z, Mahmodi MJ, Soltanghoraee H. The important biological roles of Syncytin-1 of human endogenous retrovirus W (HERV-W) and Syncytin-2 of HERV-FRD in the human placenta development. Mol Biol Rep 2023; 50:7901-7907. [PMID: 37421503 DOI: 10.1007/s11033-023-08658-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 06/30/2023] [Indexed: 07/10/2023]
Abstract
BACKGROUND Human endogenous retroviruses (HERVs) entered the germ line by retroviral infection from a distant ancestor over 30 million years ago and constitute 8% of the human genome. The majorities of HERVs are non-protein coding and lack function because of the accumulation of mutations, insertions, deletions, and/or truncations. However, a small number of HERV genes carried ORFs with beneficial functions for the host. METHODS & RESULTS In this review, we summarize the structural and important biological roles of two HERV gene products termed Syncytin-1 and Syncytin-2 in human placenta development. Indeed, two retroviral gene products that have important roles in mammalian development, Syncytin-1 (HERV-W) and Syncytin-2 (HERV-FRD), are prime examples encoded by env genes and expressed in the placental trophoblasts. Several pivotal studies revealed that Syncytins are fundamental genes implicated in regulating trophoblast fusion and placenta morphogenesis. CONCLUSION Interestingly, it has been suggested that syncytins may also be implicated in non-fusogenic activities leading to apoptosis, proliferation, and immunosuppressive activities.
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Affiliation(s)
- Mehdi Gholami Barzoki
- Department of Virology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | | | - Zahra Heydarifard
- Hepatitis Research Center, School of Medicine, Lorestan University of Medical Sciences, Khorramabad, Iran
| | - Mohamad Javad Mahmodi
- Department of Virology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Haleh Soltanghoraee
- Reproductive Biotechnology Research Center, Avicenna Research Institute, ACECR, Tehran, Iran
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8
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Skandorff I, Gille J, Ragonnaud E, Andersson AM, Schrödel S, Thirion C, Wagner R, Holst PJ. The Insertion of an Evolutionary Lost Four-Amino-Acid Cytoplasmic Tail Peptide into a Syncytin-1 Vaccine Increases T- and B-Cell Responses in Mice. Viruses 2023; 15:1686. [PMID: 37632028 PMCID: PMC10458386 DOI: 10.3390/v15081686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 07/30/2023] [Accepted: 07/31/2023] [Indexed: 08/27/2023] Open
Abstract
Human endogenous retrovirus type W (HERV-W) is expressed in various cancers. We previously developed an adenovirus-vectored cancer vaccine targeting HERV-W by encoding an assembled HERV-W group-specific antigen sequence and the HERV-W envelope sequence Syncytin-1. Syncytin-1 is constitutively fusogenic and forms large multinucleated cell fusions when overexpressed. Consequently, immunising humans with a vaccine encoding Syncytin-1 can lead to the formation of extensive syncytia, which is undesirable and poses a potential safety issue. Here, we show experiments in cell lines that restoring an evolutionary lost cleavage site of the fusion inhibitory R-peptide of Syncytin-1 inhibit cell fusion. Interestingly, this modification of the HERV-W vaccine's fusogenicity increased the expression of the vaccine antigens in vitro. It also enhanced Syncytin-1-specific antibody responses and CD8+-mediated T-cell responses compared to the wildtype vaccine in vaccinated mice, with a notable enhancement in responses to subdominant T-cell epitopes but equal responses to dominant epitopes and similar rates of survival following a tumour challenge. The impairment of cell-cell fusion and the enhanced immunogenicity profile of this HERV-W vaccine strengthens the prospects of obtaining a meaningful immune response against HERV-W in patients with HERV-W-overexpressing cancers.
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Affiliation(s)
- Isabella Skandorff
- Department of Immunology and Microbiology, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark;
- InProTher, COBIS, Ole Maaloesvej 3, 2200 Copenhagen, Denmark; (E.R.); (A.-M.A.)
| | - Jasmin Gille
- Institute of Medical Microbiology and Hygiene, Molecular Microbiology, University of Regensburg Germany, 93053 Regensburg, Germany; (J.G.); (R.W.)
| | - Emeline Ragonnaud
- InProTher, COBIS, Ole Maaloesvej 3, 2200 Copenhagen, Denmark; (E.R.); (A.-M.A.)
- Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | | | - Silke Schrödel
- Sirion Biotech GmbH, Am Haag 6, 82166 Graefelfing, Germany; (S.S.); (C.T.)
| | - Christian Thirion
- Sirion Biotech GmbH, Am Haag 6, 82166 Graefelfing, Germany; (S.S.); (C.T.)
| | - Ralf Wagner
- Institute of Medical Microbiology and Hygiene, Molecular Microbiology, University of Regensburg Germany, 93053 Regensburg, Germany; (J.G.); (R.W.)
| | - Peter Johannes Holst
- InProTher, COBIS, Ole Maaloesvej 3, 2200 Copenhagen, Denmark; (E.R.); (A.-M.A.)
- Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
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9
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Xu L, Sun S. Reconstitution of Fusion-Competent Human Placental Fusogen Syncytin-2. J Membr Biol 2022; 255:723-732. [PMID: 35596004 DOI: 10.1007/s00232-022-00242-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 05/02/2022] [Indexed: 12/24/2022]
Abstract
Mammalian placenta formation requires continuous fusion of trophoblasts. Human endogenous retrovirus-derived proteins syncytin-1 and syncytin-2 mediate cell-cell fusion of placental cytotrophoblasts to form syncytiotrophoblasts in primates, which is required for normal placenta function and fetal development. Syncytins are post-translationally cleaved by the endoprotease furin into surface (SU) and transmembrane (TM) subunits for activation. Little is currently known about the molecular mechanisms of syncytin-mediated cell-cell fusion, and their functions have not been well studied in vitro. Here, we express tagged syncytin-2 in mammalian HEK293T cells and demonstrate that the tagging greatly influences the cleavage and fusogenic activity of syncytin-2. By detecting the N-terminal tagged SU, we find that it is released into the extracellular space during the fusion process. Furthermore, when N-linked glycosylation and disulfide bond formation are blocked, the cleavage and fusogenic activity of syncytin-2 are inhibited. Finally, we were able to purify functional syncytin-2 from HEK293T cells and incorporate it into proteoliposomes. These findings lay a solid foundation for interogating the molecular mechanisms of syncytin-2-mediated cell-cell fusion in vitro.
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Affiliation(s)
- Lu Xu
- Department of Genetics and Cell Biology, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Sha Sun
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.
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Imakawa K, Kusama K, Kaneko-Ishino T, Nakagawa S, Kitao K, Miyazawa T, Ishino F. Endogenous Retroviruses and Placental Evolution, Development, and Diversity. Cells 2022; 11:cells11152458. [PMID: 35954303 PMCID: PMC9367772 DOI: 10.3390/cells11152458] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 08/01/2022] [Accepted: 08/03/2022] [Indexed: 11/16/2022] Open
Abstract
The main roles of placentas include physical protection, nutrient and oxygen import, export of gasses and fetal waste products, and endocrinological regulation. In addition to physical protection of the fetus, the placentas must provide immune protection throughout gestation. These basic functions are well-conserved; however, placentas are undoubtedly recent evolving organs with structural and cellular diversities. These differences have been explained for the last two decades through co-opting genes and gene control elements derived from transposable elements, including endogenous retroviruses (ERVs). However, the differences in placental structures have not been explained or characterized. This manuscript addresses the sorting of ERVs and their integration into the mammalian genomes and provides new ways to explain why placental structures have diverged.
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Affiliation(s)
- Kazuhiko Imakawa
- Research Institute of Agriculture, Tokai University, Kumamoto 862-8652, Japan
- Correspondence: ; Tel.: +81-96-386-2652
| | - Kazuya Kusama
- Department of Endocrine Pharmacology, Tokyo University of Pharmacy and Life Sciences, Tokyo 192-0392, Japan
| | | | - So Nakagawa
- Department of Molecular Life Science, Tokai University School of Medicine, Nakagawa 259-1193, Japan
| | - Koichi Kitao
- Laboratory of Virus-Host Coevolution, Institute for Life and Medical Sciences, Kyoto University, Kyoto 606-8507, Japan
| | - Takayuki Miyazawa
- Laboratory of Virus-Host Coevolution, Institute for Life and Medical Sciences, Kyoto University, Kyoto 606-8507, Japan
| | - Fumitoshi Ishino
- Institute of Research, Tokyo Medical and Dental University, Tokyo 113-8510, Japan
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11
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Human endogenous retrovirus-K (HERV-K) reverse transcriptase (RT) structure and biochemistry reveals remarkable similarities to HIV-1 RT and opportunities for HERV-K-specific inhibition. Proc Natl Acad Sci U S A 2022; 119:e2200260119. [PMID: 35771941 PMCID: PMC9271190 DOI: 10.1073/pnas.2200260119] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A large percentage of the human genome is composed of repetitive elements that are relics of past viral infections. Expression of these human endogenous retroviruses (HERVs) is associated with a variety of diseases, including cancer; however, causality remains to be established. A subset of these HERVs express proteins with reverse transcriptase (RT) activity. This has inspired several clinical studies of antiviral RT inhibitors for indications in which HERV expression is associated with disease. We have determined the X-ray structure of an HERV reverse transcriptase. This structure clarifies the reasons for poor inhibition by 3TC (lamivudine) and lack of inhibition by nonnucleoside inhibitors nevirapine and efavirenz. This structure will enable the design of selective HERV-K RT tools for drug target validation. Human endogenous retroviruses (HERVs) comprise nearly 8% of the human genome and are derived from ancient integrations of retroviruses into the germline. The biology of HERVs is poorly defined, but there is accumulating evidence supporting pathological roles in diverse diseases, such as cancer, autoimmune, and neurodegenerative diseases. Functional proteins are produced by HERV-encoded genes, including reverse transcriptases (RTs), which could be a contributor to the pathology attributed to aberrant HERV-K expression. To facilitate the discovery and development of HERV-K RT potent and selective inhibitors, we expressed active HERV-K RT and determined the crystal structure of a ternary complex of this enzyme with a double-stranded DNA substrate. We demonstrate a range of RT inhibition with antiretroviral nucleotide analogs, while classic nonnucleoside analogs do not inhibit HERV-K RT. Detailed comparisons of HERV-K RT with other known RTs demonstrate similarities to diverse RT families and a striking similarity to the HIV-1 RT asymmetric heterodimer. Our analysis further reveals opportunities for selective HERV-K RT inhibition.
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Abstract
Infection with SARS-CoV-2, the causative agent of the COVID-19 pandemic, originated in China and quickly spread across the globe. Despite tremendous economic and healthcare devastation, research on this virus has contributed to a better understanding of numerous molecular pathways, including those involving γ-aminobutyric acid (GABA), that will positively impact medical science, including neuropsychiatry, in the post-pandemic era. SARS-CoV-2 primarily enters the host cells through the renin–angiotensin system’s component named angiotensin-converting enzyme-2 (ACE-2). Among its many functions, this protein upregulates GABA, protecting not only the central nervous system but also the endothelia, the pancreas, and the gut microbiota. SARS-CoV-2 binding to ACE-2 usurps the neuronal and non-neuronal GABAergic systems, contributing to the high comorbidity of neuropsychiatric illness with gut dysbiosis and endothelial and metabolic dysfunctions. In this perspective article, we take a closer look at the pathology emerging from the viral hijacking of non-neuronal GABA and summarize potential interventions for restoring these systems.
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13
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Bu C, Wang Z, Ren Y, Chen D, Jiang SW. Syncytin-1 nonfusogenic activities modulate inflammation and contribute to preeclampsia pathogenesis. Cell Mol Life Sci 2022; 79:290. [PMID: 35536515 PMCID: PMC11073204 DOI: 10.1007/s00018-022-04294-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Revised: 03/23/2022] [Accepted: 04/06/2022] [Indexed: 11/03/2022]
Abstract
Maternal cellular and humoral immune responses to the allogeneic fetoplacental unit are a normal part of pregnancy adaptation. Overactive or dysregulated immune responses that often manifest as inflammation are considered a key element for the development of preeclampsia. Infiltration and activation of macrophages, nature killer cells, and T lymphocytes are frequently observed in the decidua and placenta associated with preeclampsia. In addition to local inflammation, systemic inflammatory changes including increased levels of TNF-α and interleukins (ILs) are detected in the maternal circulation. Syncytin-1 is an endogenous retroviral envelope protein that mediates the fusion of trophoblasts to form syncytiotrophoblasts, a cellular component carrying out most of placental barrier, exchange, and endocrine functions. In addition to these well-defined fusogenic functions that are known for their close association with preeclampsia, multiple studies indicated that syncytin-1 possesses nonfusogenic activities such as those for cell cycle and apoptosis regulation. Moreover, syncytin-1 expressed by trophoblasts and various types of immune cells may participate in regulation of inflammation in preeclamptic placenta and decidua. This review concentrates on the triangular relationship among inflammation, syncytin-1 nonfusogenic functions, and preeclampsia pathogenesis. Data regarding the reciprocal modulations of inflammation and poor vascularization/hypoxia are summarized. The impacts of syncytin-A (the mouse counterpart of human syncytin-1) gene knockout on placental vascularization and their implications for preeclampsia are discussed. Syncytin-1 expression in immune cells and its significance for inflammation are analyzed in the context of preeclampsia development. Finally, the involvements of syncytin-1 nonfusogenic activities in neuroinflammation and multiple sclerosis are compared to findings from preeclampsia.
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Affiliation(s)
- Chaozhi Bu
- Center of Reproductive Medicine, State Key Laboratory of Reproductive Medicine, Research Institute for Reproductive Health and Genetic Diseases, The Affiliated Wuxi Maternity and Child Health Care Hospital of Nanjing Medical University, Wuxi, 214002, China
| | - Zhiwei Wang
- Center of Reproductive Medicine, State Key Laboratory of Reproductive Medicine, Research Institute for Reproductive Health and Genetic Diseases, The Affiliated Wuxi Maternity and Child Health Care Hospital of Nanjing Medical University, Wuxi, 214002, China
- Center of Prenatal Diagnosis, Lianyungang Maternal and Child Health Hospital, Lianyungang, 222000, Jiangsu, China
| | - Yongwei Ren
- Center of Reproductive Medicine, State Key Laboratory of Reproductive Medicine, Research Institute for Reproductive Health and Genetic Diseases, The Affiliated Wuxi Maternity and Child Health Care Hospital of Nanjing Medical University, Wuxi, 214002, China
| | - Daozhen Chen
- Research Institute for Reproductive Health and Genetic Diseases, The Affiliated Wuxi Maternity and Child Health Care Hospital of Nanjing Medical University, Wuxi, 214002, China.
| | - Shi-Wen Jiang
- Center of Reproductive Medicine, State Key Laboratory of Reproductive Medicine, Research Institute for Reproductive Health and Genetic Diseases, The Affiliated Wuxi Maternity and Child Health Care Hospital of Nanjing Medical University, Wuxi, 214002, China.
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14
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Durnaoglu S, Lee SK, Ahnn J. Syncytin, envelope protein of human endogenous retrovirus (HERV): no longer 'fossil' in human genome. Anim Cells Syst (Seoul) 2022; 25:358-368. [PMID: 35059135 PMCID: PMC8765258 DOI: 10.1080/19768354.2021.2019109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Accepted: 12/07/2021] [Indexed: 12/17/2022] Open
Abstract
Human endogenous retroviruses (HERVs) are 'fossil viruses' that resulted from stable integrations of exogenous retroviruses throughout evolution. HERVs are defective and do not produce infectious viral particles. However, some HERVs retain a limited coding capacity and produce retroviral transcripts and proteins, which function in human developmental process and various pathologies, including many cancers and neurological diseases. Recently, it has been reported that HERVs are differently expressed in COVID-19 disease caused by infection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this review, we discuss the molecular structure and function of HERV ENV proteins, particularly syncytins, and their conventional roles in human development and diseases, and potential involvement in COVID-19 regarding the newly reported mental symptoms. We also address COVID-19 vaccine-related infertility concerns arising from the similarity of syncytin with the spike protein of SARS-CoV-2, which have been proved invalid.
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Affiliation(s)
- Serpen Durnaoglu
- College of Natural Sciences, Hanyang University, Seoul, Republic of Korea
- Research Institute for Natural Sciences, College of Natural Sciences, Hanyang University, Seoul, Republic of Korea
| | - Sun-Kyung Lee
- College of Natural Sciences, Hanyang University, Seoul, Republic of Korea
- Research Institute for Natural Sciences, College of Natural Sciences, Hanyang University, Seoul, Republic of Korea
| | - Joohong Ahnn
- College of Natural Sciences, Hanyang University, Seoul, Republic of Korea
- Research Institute for Natural Sciences, College of Natural Sciences, Hanyang University, Seoul, Republic of Korea
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15
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Markert UR, Szekeres-Bartho J, Schleußner E. Adverse effects on female fertility from vaccination against COVID-19 unlikely. J Reprod Immunol 2021; 148:103428. [PMID: 34601377 PMCID: PMC8453778 DOI: 10.1016/j.jri.2021.103428] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 09/16/2021] [Accepted: 09/20/2021] [Indexed: 10/26/2022]
Abstract
This opinion paper briefly presents arguments that support the unlikelihood of an impact on female fertility from current covid-19 vaccines.
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Affiliation(s)
- Udo R Markert
- Department of Obstetrics, Jena University Hospital, Am Klinikum 1, 07747, Jena, Germany.
| | | | - Ekkehard Schleußner
- Department of Obstetrics, Jena University Hospital, Am Klinikum 1, 07747, Jena, Germany
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16
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Morris RS. SARS-CoV-2 spike protein seropositivity from vaccination or infection does not cause sterility. F S Rep 2021; 2:253-255. [PMID: 34095871 PMCID: PMC8169568 DOI: 10.1016/j.xfre.2021.05.010] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 05/24/2021] [Accepted: 05/28/2021] [Indexed: 02/02/2023] Open
Abstract
Several reports claim that the purported similarity between syncytin-1 and the SARS-CoV-2 spike protein may induce immune cross-reactivity resulting in female sterility. We used frozen embryo transfer as a model for comparing the implantation rates between SARS-CoV-2 vaccine seropositive, infection seropositive, and seronegative women. No difference was found in serum hCG documented implantation rates or sustained implantation rates between the three groups. Reports claiming that COVID-19 vaccines or illness cause female sterility are unfounded.
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Abstract
The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has had a massive impact on human lives worldwide. While the airborne SARS-CoV-2 primarily affects the lungs, viremia is not uncommon. As placental trophoblasts are directly bathed in maternal blood, they are vulnerable to SARS-CoV-2. Intriguingly, the human fetus is largely spared from SARS-CoV-2 infection. We tested whether the human placenta expresses the main SARS-CoV-2 entry factors angiotensin-converting enzyme 2 (ACE2), transmembrane protease serine 2 (TMPRSS2), and furin and showed that ACE2 and TMPRSS2 are expressed in the trophoblast rather than in other placental villous cells. While furin is expressed in the main placental villous cell types, we surveyed, trophoblasts exhibit the highest expression. In line with the expression of these entry factors, we demonstrated that a SARS-CoV-2 pseudovirus could enter primary human trophoblasts. Mechanisms underlying placental defense against SARS-CoV-2 infection likely involve postentry processing, which may be germane for mitigating interventions against SARS-CoV-2. IMPORTANCE Pregnant women worldwide have been affected by COVID-19. As the virus is commonly spread to various organs via the bloodstream and because human placental trophoblasts are directly bathed in maternal blood, feto-placental infection by SARS-CoV-2 seems likely. However, despite the heightened risk to pregnant women, thus far the transmission risk of COVID-19 to the feto-placental unit seems extremely low. This has been recently attributed to a negligible expression of SARS-CoV-2 entry factors in the human placenta. We therefore sought to explore the expression of the entry factors ACE2 and TMPRSS2 in the different cell types of human placental villi. Using a combination of transcriptome sequencing (RNA-seq), real-time quantitative PCR (RT-qPCR), in situ hybridization, and immunofluorescence, we found that trophoblasts, but not the other main villous cell types, express ACE2 and TMPRSS2, with a broad expression of furin. Correspondingly, we also showed that primary human trophoblasts are permissive to entry of SARS-CoV-2 pseudovirus particles.
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18
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Tang Y, Woodward BO, Pastor L, George AM, Petrechko O, Nouvet FJ, Haas DW, Jiang G, Hildreth JEK. Endogenous Retroviral Envelope Syncytin Induces HIV-1 Spreading and Establishes HIV Reservoirs in Placenta. Cell Rep 2021; 30:4528-4539.e4. [PMID: 32234485 DOI: 10.1016/j.celrep.2020.03.016] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Revised: 01/16/2020] [Accepted: 03/05/2020] [Indexed: 02/08/2023] Open
Abstract
Radical cure of HIV-1 (HIV) is hampered by the establishment of HIV reservoirs and persistent infection in deep tissues despite suppressive antiretroviral therapy (ART). Here, we show that among HIV-positive women receiving suppressive ART, cells from placental tissues including trophoblasts contain HIV RNA and DNA. These viruses can be reactivated by latency reversal agents. We find that syncytin, the envelope glycoprotein of human endogenous retrovirus family W1 expressed on placental trophoblasts, triggers cell fusion with HIV-infected T cells. This results in cell-to-cell spread of HIV to placental trophoblasts. Such cell-to-cell spread of HIV is less sensitive to ART than free virus. Replication in syncytin-expressing cells can also produce syncytin-pseudotyped HIV, further expanding its ability to infect non-CD4 cells. These previously unrecognized mechanisms of HIV entry enable the virus to bypass receptor restriction to infect host barrier cells, thereby facilitating viral transmission and persistent infection in deep tissues.
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Affiliation(s)
- Yuyang Tang
- University of North Carolina at Chapel Hill, HIV Cure Center and Institute of Global Health & Infectious Diseases, Chapel Hill, NC 27599, USA; Department of Medical Microbiology and Immunology, University of California, Davis, Davis, CA 95616, USA
| | - Beverly O Woodward
- Department of Medicine, Division of Infectious Diseases, Vanderbilt University School of Medicine, Nashville, TN 37240, USA
| | - Lorena Pastor
- Department of Medical Microbiology and Immunology, University of California, Davis, Davis, CA 95616, USA
| | - Alvin M George
- Department of Internal Medicine, Meharry Medical College, Nashville, TN 37208, USA
| | - Oksana Petrechko
- Department of Medical Microbiology and Immunology, University of California, Davis, Davis, CA 95616, USA
| | - Franklin J Nouvet
- Department of Internal Medicine, Meharry Medical College, Nashville, TN 37208, USA
| | - David W Haas
- Department of Medicine, Division of Infectious Diseases, Vanderbilt University School of Medicine, Nashville, TN 37240, USA; Department of Internal Medicine, Meharry Medical College, Nashville, TN 37208, USA
| | - Guochun Jiang
- University of North Carolina at Chapel Hill, HIV Cure Center and Institute of Global Health & Infectious Diseases, Chapel Hill, NC 27599, USA; Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
| | - James E K Hildreth
- Department of Medical Microbiology and Immunology, University of California, Davis, Davis, CA 95616, USA; Department of Internal Medicine, Meharry Medical College, Nashville, TN 37208, USA.
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19
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Syncytin 1 dependent horizontal transfer of marker genes from retrovirally transduced cells. Sci Rep 2019; 9:17637. [PMID: 31776415 PMCID: PMC6881383 DOI: 10.1038/s41598-019-54178-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Accepted: 09/29/2019] [Indexed: 12/18/2022] Open
Abstract
Retroviral transduction is routinely used to generate cell lines expressing exogenous non-viral genes. Here, we show that human cells transduced to stably express GFP transfer GFP gene to non-transduced cells. This horizontal gene transfer was mediated by a fraction of extracellular membrane vesicles that were released by the transduced cells. These vesicles carried endogenous retroviral envelope protein syncytin 1 and essentially acted as replication-competent retroviruses. The ability to transfer the GFP gene correlated with the levels of syncytin 1 expression in the transduced cells and depended on the fusogenic activity of this protein, substantiating the hypothesis that endogenous syncytin 1 mediates fusion stage in the delivery of extracellular vesicle cargo into target cells. Our findings suggest that testing for replication-competent retroviruses, a routine safety test for transduced cell products in clinical studies, should be also carried out for cell lines generated by retroviral vectors in in vitro studies.
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20
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Fei F, Li C, Wang X, Du J, Liu K, Li B, Yao P, Li Y, Zhang S. Syncytin 1, CD9, and CD47 regulating cell fusion to form PGCCs associated with cAMP/PKA and JNK signaling pathway. Cancer Med 2019; 8:3047-3058. [PMID: 31025548 PMCID: PMC6558479 DOI: 10.1002/cam4.2173] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2018] [Accepted: 03/28/2019] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND We have previously reported the formation of polyploid giant cancer cells (PGCCs) through endoreduplication or cell fusion after cobalt chloride (CoCl2 ) induction. Cell fusion plays an important role in development and disease. However, the underlying molecular mechanism concerning cell fusion in PGCCs formation and clinicopathological significances remains unclear. METHODS We treat HCT116 and LoVo cell with CoCl2 and observed the cell fusion via fluorescent markers of different colors. Western blot and immunocytochemical staining were used to compare the expression and subcellular location of the fusion-related proteins syncytin 1, CD9, and CD47 along with PKA RIα, JNK1, and c-Jun between PGCCs and control cells from the HCT116 and LoVo cell lines. Moreover, 173 cases of colorectal tumor tissue samples were analyzed, including 47 cases of well-differentiated primary colorectal cancer (group I) and 5 cases of corresponding metastatic tumors (group II), 38 cases of moderately differentiated primary colorectal cancer (group III) and 14 cases of corresponding metastatic tumors (group IV), and 42 cases of poorly differentiated primary colorectal cancer (group V) and 27 cases of corresponding metastatic tumors (group VI). RESULTS The expression of syncytin 1, CD9, and CD47 is higher in PGCCs than in control cells and they are located in the cytoplasm. The expression of PKA RIα and JNK1 decreased, and that of c-Jun increased in PGCCs. The syncytin 1 expression was significantly different between groups I and II (P = 0.000), groups III and IV (P = 0.000), groups V and VI (P = 0.029), groups I and III (P = 0.001), groups III and V (P = 0.000), and groups I, III, and V (P = 0.000). CONCLUSIONS These data indicate that the cell fusion-related proteins syncytin 1, CD9, and CD47 may be involved in PGCC formation, and that cAMP/PKA and JNK signaling is likely to promote PGCC formation via the regulation of cell fusion processes.
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Affiliation(s)
- Fei Fei
- School of Medicine, Nankai University, Tianjin, P.R. China.,Department of Pathology, Tianjin Union Medical Center, Tianjin, P.R. China
| | - Chunyuan Li
- School of Medicine, Nankai University, Tianjin, P.R. China.,Department of Pathology, Tianjin Union Medical Center, Tianjin, P.R. China
| | - Xinlu Wang
- Graduate School, Tianjin University of Traditional Chinese Medicine, Tianjin, P.R. China
| | - Jiaxing Du
- Graduate School, Tianjin University of Traditional Chinese Medicine, Tianjin, P.R. China
| | - Kai Liu
- Tianjin Medical University, Tianjin, P.R. China
| | - Bo Li
- Graduate School, Tianjin University of Traditional Chinese Medicine, Tianjin, P.R. China
| | - Peiyu Yao
- Department of Pathology, Tianjin Union Medical Center, Tianjin, P.R. China
| | - Yuwei Li
- Department of colorectal surgery, Tianjin Union Medical Center, Tianjin, P.R. China
| | - Shiwu Zhang
- School of Medicine, Nankai University, Tianjin, P.R. China.,Department of Pathology, Tianjin Union Medical Center, Tianjin, P.R. China
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21
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Uygur B, Leikina E, Melikov K, Villasmil R, Verma SK, Vary CPH, Chernomordik LV. Interactions with Muscle Cells Boost Fusion, Stemness, and Drug Resistance of Prostate Cancer Cells. Mol Cancer Res 2019; 17:806-820. [PMID: 30587522 PMCID: PMC8312562 DOI: 10.1158/1541-7786.mcr-18-0500] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 08/31/2018] [Accepted: 12/05/2018] [Indexed: 12/22/2022]
Abstract
Poorly understood interactions with nonmalignant cells within the tumor microenvironment play an important role in cancer progression. Here, we explored interactions between prostate cancer and muscle cells that surround the prostate. We found that coculturing of prostate cancer cells with skeletal or smooth muscle cells expands the subpopulations of cancer cells with features characteristic of cancer stem-like cells, including anchorage-independent growth, elevated CD133 expression, and drug resistance. These changes in the properties of cancer cells depend on: (i) the muscle cell-induced increases in the concentrations of interleukins 4 and 13; (ii) the cytokine-induced upregulation of the expression of syncytin 1 and annexin A5; and (iii) cancer cell fusion. In human prostate cancer tissues, expression of syncytin 1 and annexin A5, proteins that we found to be required for the cell fusion, positively correlated with the cancer development suggesting that these proteins can be used as biomarkers to evaluate cancer progression and potential therapeutic targets. IMPLICATIONS: The discovered effects of muscle cells on prostate cancer cells reveal a novel and specific pathway by which muscle cells in the microenvironment of prostate cancer cells promote cell fusion and cancer progression.
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Affiliation(s)
- Berna Uygur
- Section on Membrane Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, Maryland
| | - Evgenia Leikina
- Section on Membrane Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, Maryland
| | - Kamran Melikov
- Section on Membrane Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, Maryland
| | | | - Santosh K Verma
- Section on Membrane Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, Maryland
| | - Calvin P H Vary
- Center for Molecular Medicine, Maine Medical Center Research Institute, Scarborough, Maine
| | - Leonid V Chernomordik
- Section on Membrane Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, Maryland.
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22
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Verma SK, Leikina E, Melikov K, Gebert C, Kram V, Young MF, Uygur B, Chernomordik LV. Cell-surface phosphatidylserine regulates osteoclast precursor fusion. J Biol Chem 2017; 293:254-270. [PMID: 29101233 DOI: 10.1074/jbc.m117.809681] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 11/02/2017] [Indexed: 12/17/2022] Open
Abstract
Bone-resorbing multinucleated osteoclasts that play a central role in the maintenance and repair of our bones are formed from bone marrow myeloid progenitor cells by a complex differentiation process that culminates in fusion of mononuclear osteoclast precursors. In this study, we uncoupled the cell fusion step from both pre-fusion stages of osteoclastogenic differentiation and the post-fusion expansion of the nascent fusion connections. We accumulated ready-to-fuse cells in the presence of the fusion inhibitor lysophosphatidylcholine and then removed the inhibitor to study synchronized cell fusion. We found that osteoclast fusion required the dendrocyte-expressed seven transmembrane protein (DC-STAMP)-dependent non-apoptotic exposure of phosphatidylserine at the surface of fusion-committed cells. Fusion also depended on extracellular annexins, phosphatidylserine-binding proteins, which, along with annexin-binding protein S100A4, regulated fusogenic activity of syncytin 1. Thus, in contrast to fusion processes mediated by a single protein, such as epithelial cell fusion in Caenorhabditis elegans, the cell fusion step in osteoclastogenesis is controlled by phosphatidylserine-regulated activity of several proteins.
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Affiliation(s)
- Santosh K Verma
- Sections on Membrane Biology, National Institutes of Health, Bethesda, Maryland 20892
| | - Evgenia Leikina
- Sections on Membrane Biology, National Institutes of Health, Bethesda, Maryland 20892
| | - Kamran Melikov
- Sections on Membrane Biology, National Institutes of Health, Bethesda, Maryland 20892
| | - Claudia Gebert
- Genomic Imprinting, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892
| | - Vardit Kram
- Craniofacial and Skeletal Diseases Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892
| | - Marian F Young
- Craniofacial and Skeletal Diseases Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892
| | - Berna Uygur
- Sections on Membrane Biology, National Institutes of Health, Bethesda, Maryland 20892
| | - Leonid V Chernomordik
- Sections on Membrane Biology, National Institutes of Health, Bethesda, Maryland 20892.
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23
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Imakawa K, Nakagawa S. The Phylogeny of Placental Evolution Through Dynamic Integrations of Retrotransposons. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2017; 145:89-109. [PMID: 28110755 DOI: 10.1016/bs.pmbts.2016.12.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Trophoblasts, a major constituent of the placenta, are known to express genes derived from various endogenous retroviruses (ERVs) as well as LTR retrotransposons. However, the evolutionary significance of ERV-derived genes involved in placental development has not been well characterized. In this review, we catalog the diverse morphology of placental structure among mammalian species with note of counterintuitive developments. We then detail the history of ancient placenta development with paternally expressed gene 10 (Peg10/Sirh1), Peg11/Sirh2, and Sirh7/Ldoc1 as LTR retrotransposons, followed by independent captures of ERV-env-related genes such as Syncytin-1, -2, -A, -B, -Rum1, and Fematrin-1 responsible for trophoblast cell fusion, resulting in multinucleate syncytiotrophoblast formation, and possibly morphological diversification of placentas. Because the endogenization of retroviral infections has occurred multiple times independently in different mammalian lineages, and some use the same molecules in their transcriptional activation, we speculate that ERV gene variants integrated into mammalian genomes in a locus-specific manner have replaced the genes previously responsible for cell fusion. Moreover, ERVs also work as transcriptional regulators of various genes such as interferon (IFN)-stimulated genes. The "baton pass" hypothesis suggests that evolutionary events caused by multiple successive retrotransposon integrations, possibly resulting in effective fusogenic activity, downstream gene transcription in a temporal and spatial manner, and/or increased diversity of placental structures.
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Affiliation(s)
- K Imakawa
- Animal Resource Science Center, Graduate School of Agricultural and Life Science, The University of Tokyo, Kasama, Japan.
| | - S Nakagawa
- Biomedical Informatics Laboratory, Tokai University School of Medicine, Isehara, Japan
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24
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Møller AMJ, Delaissé JM, Søe K. Osteoclast Fusion: Time-Lapse Reveals Involvement of CD47 and Syncytin-1 at Different Stages of Nuclearity. J Cell Physiol 2016; 232:1396-1403. [PMID: 27714815 PMCID: PMC6221100 DOI: 10.1002/jcp.25633] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Accepted: 10/05/2016] [Indexed: 12/13/2022]
Abstract
Investigations addressing the molecular keys of osteoclast fusion are primarily based on end-point analyses. No matter if investigations are performed in vivo or in vitro the impact of a given factor is predominantly analyzed by counting the number of multi-nucleated cells, the number of nuclei per multinucleated cell or TRAcP activity. But end-point analyses do not show how the fusion came about. This would not be a problem if fusion of osteoclasts was a random process and occurred by the same molecular mechanism from beginning to end. However, we and others have in the recent period published data suggesting that fusion partners may specifically select each other and that heterogeneity between the partners seems to play a role. Therefore, we set out to directly test the hypothesis that fusion factors have a heterogenic involvement at different stages of nuclearity. Therefore, we have analyzed individual fusion events using time-lapse and antagonists of CD47 and syncytin-1. All time-lapse recordings have been studied by two independent observers. A total of 1808 fusion events were analyzed. The present study shows that CD47 and syncytin-1 have different roles in osteoclast fusion depending on the nuclearity of fusion partners. While CD47 promotes cell fusions involving mono-nucleated pre-osteoclasts, syncytin-1 promotes fusion of two multi-nucleated osteoclasts, but also reduces the number of fusions between mono-nucleated pre-osteoclasts. Furthermore, CD47 seems to mediate fusion mostly through broad contact surfaces between the partners' cell membrane while syncytin-1 mediate fusion through phagocytic-cup like structure. J. Cell. Physiol. 232: 1396-1403, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Anaïs Marie Julie Møller
- Department of Clinical Cell Biology, Vejle Hospital/Lillebaelt Hospital, Institute of Regional Health Research, University of Southern Denmark, Vejle, Denmark
| | - Jean-Marie Delaissé
- Department of Clinical Cell Biology, Vejle Hospital/Lillebaelt Hospital, Institute of Regional Health Research, University of Southern Denmark, Vejle, Denmark
| | - Kent Søe
- Department of Clinical Cell Biology, Vejle Hospital/Lillebaelt Hospital, Institute of Regional Health Research, University of Southern Denmark, Vejle, Denmark
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25
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Bastida-Ruiz D, Van Hoesen K, Cohen M. The Dark Side of Cell Fusion. Int J Mol Sci 2016; 17:E638. [PMID: 27136533 PMCID: PMC4881464 DOI: 10.3390/ijms17050638] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Revised: 04/14/2016] [Accepted: 04/22/2016] [Indexed: 12/17/2022] Open
Abstract
Cell fusion is a physiological cellular process essential for fertilization, viral entry, muscle differentiation and placental development, among others. In this review, we will highlight the different cancer cell-cell fusions and the advantages obtained by these fusions. We will specially focus on the acquisition of metastatic features by cancer cells after fusion with bone marrow-derived cells. The mechanism by which cancer cells fuse with other cells has been poorly studied thus far, but the presence in several cancer cells of syncytin, a trophoblastic fusogen, leads us to a cancer cell fusion mechanism similar to the one used by the trophoblasts. The mechanism by which cancer cells perform the cell fusion could be an interesting target for cancer therapy.
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Affiliation(s)
- Daniel Bastida-Ruiz
- Department of Gynecology Obstetrics, Faculty of Medicine, University of Geneva, Geneva 1211, Switzerland.
| | - Kylie Van Hoesen
- Department of Gynecology Obstetrics, Faculty of Medicine, University of Geneva, Geneva 1211, Switzerland.
| | - Marie Cohen
- Department of Gynecology Obstetrics, Faculty of Medicine, University of Geneva, Geneva 1211, Switzerland.
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26
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Cui L, Wang H, Lu X, Wang R, Zheng R, Li Y, Yang X, Jia WT, Zhao Y, Wang Y, Wang H, Wang YL, Zhu C, Lin HY, Wang H. Effects of individually silenced N-glycosylation sites and non-synonymous single-nucleotide polymorphisms on the fusogenic function of human syncytin-2. Cell Adh Migr 2016; 10:39-55. [PMID: 26853155 PMCID: PMC4853038 DOI: 10.1080/19336918.2015.1093720] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The placental syncytiotrophoblast, which is formed by the fusion of cytotrophoblast cells, is indispensable for the establishment and maintenance of normal pregnancy. The human endogenous retrovirus envelope glycoprotein syncytin-2 is the most important player in mediating trophoblast cell-cell fusion as a fusogen. We constructed expression plasmids of wild-type and 21 single-amino-acid substitution mutants of syncytin-2, including 10 N-glycosylation sites individually silenced by mutagenizing N to Q, 1 naturally occurring single-nucleotide polymorphism (SNP) N118S that introduced an N-glycosylation site, and another 10 non-synonymous SNPs located within important functional domains. We observed that syncytin-2 was highly fusogenic and that the mutants had different capacities in merging 293T cells. Of the 21 mutants, N133Q, N312Q, N443Q, C46R (in the CXXC motif) and R417H (in the heptad repeat region and immunosuppressive domain) lost their fusogenicity, whereas N332Q, N118S, T367M (in the fusion peptide), V483I (in the transmembrane domain) and T522M (in the cytoplasmic domain) enhanced the fusogenic activity. We also proved that N133, N146, N177, N220, N241, N247, N312, N332 and N443 were all glycosylated in 293T cells. A co-immunoprecipitation assay showed compromised interaction between mutants N443Q, C46R, T367M, R417H and the receptor MFSD2A, whereas N118S was associated with more receptors. We also sequenced the coding sequence of syncytin-2 in 125 severe pre-eclamptic patients and 272 normal pregnant Chinese women. Surprisingly, only 1 non-synonymous SNP T522M was found and the frequencies of heterozygous carriers were not significantly different. Taken together, our results suggest that N-glycans at residues 133, 312, 332 and 443 of syncytin-2 are required for optimal fusion induction, and that SNPs C46R, N118S, T367M, R417H, V483I and T522M can alter the fusogenic function of syncytin-2.
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Affiliation(s)
- Lina Cui
- a State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences , Beijing , China.,b Graduate School of Chinese Academy of Sciences , Beijing , China
| | - Huiying Wang
- c Department of Obstetrics and Gynecology , Beijing Shijitan Hospital , Beijing , China
| | - Xiaoyin Lu
- a State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences , Beijing , China.,b Graduate School of Chinese Academy of Sciences , Beijing , China
| | - Rui Wang
- a State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences , Beijing , China.,b Graduate School of Chinese Academy of Sciences , Beijing , China
| | - Ru Zheng
- a State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences , Beijing , China.,b Graduate School of Chinese Academy of Sciences , Beijing , China
| | - Yue Li
- a State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences , Beijing , China
| | - Xiaokui Yang
- d Beijing Obstetrics and Gynecology Hospital, Capital Medical University , Beijing , China
| | - Wen-Tong Jia
- a State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences , Beijing , China.,b Graduate School of Chinese Academy of Sciences , Beijing , China
| | - Yangyu Zhao
- e Department of Obstetrics and Gynecology , Peking University Third Hospital , Beijing , China
| | - Yongqing Wang
- e Department of Obstetrics and Gynecology , Peking University Third Hospital , Beijing , China
| | - Haibin Wang
- a State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences , Beijing , China
| | - Yan-Ling Wang
- a State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences , Beijing , China
| | - Cheng Zhu
- a State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences , Beijing , China
| | - Hai-Yan Lin
- a State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences , Beijing , China
| | - Hongmei Wang
- a State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences , Beijing , China
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Abstract
Mammalian life begins with a cell-cell fusion event, i.e. the fusion of the spermatozoid with the oocyte and needs further cell-cell fusion processes for the development, growth, and maintenance of tissues and organs over the whole life span. Furthermore, cellular fusion plays a role in infection, cancer, and stem cell-dependent regeneration as well as including an expanded meaning of partial cellular fusion, nanotube formation, and microparticle-cell fusion. The cellular fusion process is highly regulated by proteins which carry the information to organize and regulate membranes allowing the merge of two separate lipid bilayers into one. The regulation of this genetically and epigenetically controlled process is achieved by different kinds of signals leading to communication of fusing cells. The local cellular and extracellular environment additionally initiates specific cell signaling necessary for the induction of the cell-cell fusion process. Common motifs exist in distinct cell-cell fusion processes and their regulation. However, there is specific regulation of different cell-cell fusion processes, e.g. myoblast, placental, osteoclast, and stem cell fusion. Hence, specialized fusion events vary between cell types and species. Molecular mechanisms remain largely unknown, especially limited knowledge is present for cancer and stem cell fusion mechanisms and regulation. More research is necessary for the understanding of cellular fusion processes which can lead to development of new therapeutic strategies grounding on cellular fusion regulation.
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Affiliation(s)
- Lena Willkomm
- Department of Molecular and Cellular Sport Medicine, Institute of Cardiovascular Research and Sport Medicine, German Sport University Cologne, Am Sportpark Müngersdorf 6, 50933, Cologne, Germany
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Abstract
A placenta as we know now is a relatively new invention in mammals. Data accumulated indicates that a major cell type of the placenta is trophoblast, in which elevated expression of genes derived from various endogenous retroviruses (ERVs) as well as LTR retrotransposons is seen. However, evolutionally significance of ERV expression in placental development has not been well characterized or sorted out. In this review, we describe diversity of placental structures among mammalian species, of which morphological and cells types are far more diverse than those expected from the lines of mammalian orders. We then describe paternally expressed gene 10 (Peg10/Sirh1) and Peg11/Sirh2 as ERVs associated with ancient placenta development, followed by env-related genes such as Syncytin-1, -2, -A, -B, -Rum1, and Fematrin-1 responsible for trophoblast cells fusion, resulting in multinucleate syncytiotrophoblast formation. Because the endogenization of retroviral infections has occurred multiple times in different mammalian lineages, and some of them use similar molecules in their transcriptional activation, we speculate that ERV gene variants integrated into mammalian genomes in a locus specific manner have replaced the genes previously responsible for cell fusion. The role of cell fusion achieved by multiple successive ERV integrations is now called ''baton pass'' hypothesis, possibly resulting in increased trophoblast cell fusion, morphological diversity in placental structures, and survivability of fetuses and/or reproductive advantage in placental mammals.
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Affiliation(s)
| | - So Nakagawa
- Department of Molecular Life Science, Tokai University School of Medicine
| | - Kazuya Kusama
- Animal Resource Science Center, The University of Tokyo
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Imakawa K, Nakagawa S, Miyazawa T. Baton pass hypothesis: successive incorporation of unconserved endogenous retroviral genes for placentation during mammalian evolution. Genes Cells 2015; 20:771-88. [PMID: 26442811 DOI: 10.1111/gtc.12278] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 07/14/2015] [Indexed: 12/23/2022]
Abstract
It is well accepted that numerous RNAs derived from endogenous retroviruses (ERVs) are expressed in mammalian reproductive structures, particularly in the uterus, trophoblast, and placenta. Syncytin 1 and syncytin 2 in humans and syncytin A and syncytin B in mice are membrane proteins originating from Env genes of ERVs. These ERVs are involved in the fusion of trophoblast cells, resulting in multinucleated syncytiotrophoblast formation. Evidence accumulated indicates that syncytin-like fusogenic proteins are expressed in the placenta of rabbits, dogs/cats, ruminant ungulates, tenrecs, and opossums. The syncytin genes so far characterized are known to be endogenized to the host genome only within the past 12-80 million years, more recently than the appearance of mammalian placentas, estimated to be 160-180 million years ago. We speculate that ERVs including syncytin-like gene variants integrated into mammalian genomes in a locus-specific manner have replaced the genes previously responsible for cell fusion. We therefore propose the 'baton pass' hypothesis, in which multiple successive ERV variants 'take over' cell-fusion roles, resulting in increased trophoblast cell fusion, morphological variations in placental structures, and enhanced reproductive success in placental mammals.
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Affiliation(s)
- Kazuhiko Imakawa
- Laboratory of Theriogenology and Animal Breeding, Graduate School of Agricultural and Life Science, The University of Tokyo, Tokyo, 113-8657, Japan
| | - So Nakagawa
- Biomedical Informatics Laboratory, Department of Molecular Life Science, Tokai University School of Medicine, Isehara, Kanagawa, 259-1193, Japan
| | - Takayuki Miyazawa
- Laboratory of Signal Transduction, Department of Cell Biology, Institute for Virus Research, Kyoto University, Kyoto, 606-8507, Japan
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Formaldehyde Crosses the Human Placenta and Affects Human Trophoblast Differentiation and Hormonal Functions. PLoS One 2015; 10:e0133506. [PMID: 26186596 PMCID: PMC4506020 DOI: 10.1371/journal.pone.0133506] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 06/29/2015] [Indexed: 11/19/2022] Open
Abstract
The chorionic villus of the human placenta is the source of specific endocrine functions and nutrient exchanges. These activities are ensured by the syncytiotrophobast (ST), which bathes in maternal blood. The ST arises and regenerates throughout pregnancy by fusion of underlying cytotrophoblasts (CT). Any anomaly of ST formation or regeneration can affect pregnancy outcome and fetal growth. Because of its direct interaction with maternal blood, the ST is sensitive to drugs, pollutants and xenohormones. Ex vivo assays of perfused cotyledon show that formaldehyde, a common pollutant present in furniture, paint and plastics, can accumulate in the human placenta and cross to the fetal compartment. By means of RT-qPCR, immunoblot and immunocytochemistry experiments, we demonstrate in vitro that formaldehyde exerts endocrine toxicity on human trophoblasts, including a decrease in the production of protein hormones of pregnancy. In addition, formaldehyde exposure triggered human trophoblast fusion by upregulating syncitin-1 receptor expression (ASC-type amino-acid transporter 2: ASCT2). Moreover, we show that formaldehyde-exposed trophoblasts present an altered redox status associated with oxidative stress, and an increase in ASCT2 expression intended to compensate for this stress. Finally, we demonstrate that the adverse effects of formaldehyde on trophoblast differentiation and fusion are reversed by N-acetyl-L-cysteine (Nac), an antioxidant.
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Nakaya Y, Miyazawa T. The Roles of Syncytin-Like Proteins in Ruminant Placentation. Viruses 2015; 7:2928-42. [PMID: 26057168 PMCID: PMC4488720 DOI: 10.3390/v7062753] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2015] [Revised: 03/20/2015] [Accepted: 05/29/2015] [Indexed: 01/02/2023] Open
Abstract
Recent developments in genome sequencing techniques have led to the identification of huge numbers of endogenous retroviruses (ERV) in various mammals. ERVs, which occupy 8%–13% of mammalian genomes, are believed to affect mammalian evolution and biological diversity. Although the functional significance of most ERVs remains to be elucidated, several ERVs are thought to have pivotal roles in host physiology. We and other groups recently identified ERV envelope proteins (e.g., Fematrin-1, Syncytin-Rum1, endogenous Jaagsiekte sheep retrovirus Env) that may determine the morphogenesis of the unique fused trophoblast cells, termed trinucleate cells and syncytial plaques, found in ruminant placentas; however, there are still a number of outstanding issues with regard to the role of ERVs that remain to be resolved. Here, we review what is known about how these ERVs have contributed to the development of ruminant-specific trophoblast cells.
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Affiliation(s)
- Yuki Nakaya
- Department of Infectious Diseases, Kyoto Prefectural University of Medicine, 465 Kawaramachi-hirokoji-Kajiicho, Kamigyo-ku, Kyoto 602-8566, Japan.
- Laboratory of Signal Transduction, Department of Cell Biology, Institute for Virus Research, Kyoto University, 53 Shogoin-Kawaharacho, Sakyo-ku, Kyoto 606-8507, Japan.
| | - Takayuki Miyazawa
- Laboratory of Signal Transduction, Department of Cell Biology, Institute for Virus Research, Kyoto University, 53 Shogoin-Kawaharacho, Sakyo-ku, Kyoto 606-8507, Japan.
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Dysfunction of bovine endogenous retrovirus K2 envelope glycoprotein is related to unsuccessful intracellular trafficking. J Virol 2014; 88:6896-905. [PMID: 24696495 DOI: 10.1128/jvi.00288-14] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
UNLABELLED Endogenous retroviruses (ERVs) are the remnants of retroviral infection of ancestral germ cells. Mutations introduced into ERVs halt the production of infectious agents, but their effects on the function of retroviral proteins are not fully understood. Retroviral envelope glycoproteins (Envs) are utilized in membrane fusion during viral entry, and we recently identified intact coding sequences for bovine endogenous retrovirus K1 (BERV-K1) and BERV-K2 Envs. Amino acid sequences of BERV-K1 Env (also called Fematrin-1) and BERV-K2 Env are similar, and both viruses are classified in the genus Betaretrovirus. While Fematrin-1 plays an important role in cell-to-cell fusion in bovine placenta, the BERV-K2 envelope gene is marginally expressed in vivo, and its recombinant Env protein is defective in membrane fusion due to inefficient cleavage of surface (SU) and transmembrane subunits. Here, we conducted chimeric analyses of Fematrin-1 and BERV-K2 Envs and revealed that defective maturation of BERV-K2 Env contributed to failed intracellular trafficking. Fluorescence microscopy and flow cytometric analysis suggested that in contrast to Fematrin-1 Env, BERV-K2 Env could not be transported from the endoplasmic reticulum to the trans-Golgi network, where cellular proteases required for processing retroviral Envs are localized. We also identified that one of the responsive regions of this phenomenon resided within a 65-amino-acid region of BERV-K2 SU. This is the first report to identify that retroviral Env SU is involved in the regulation of intracellular trafficking, and it may help to elucidate the maturation process of Fematrin-1 and other related Envs. IMPORTANCE Retroviruses utilize envelope glycoproteins (Envs) to enter host target cells. Mature retroviral Env is a heterodimer, which consists of surface (SU) and transmembrane (TM) subunits that are generated by the cleavage of an Env precursor protein in the trans-Golgi network. SU and TM mediate the recognition of the entry receptor and virus-host membrane fusion, respectively. However, unexplained issues remain for the maturation process of retroviral Env. We previously reported that bovine endogenous retrovirus K2 (BERV-K2) Env lost fusogenicity due to a defect in the cleavage of SU and TM. In this study, we identified that mutations residing in BERV-K2 SU disturbed intracellular trafficking of BERV-K2 Env and resulted its inefficient cleavage. Because SU is not known to play an important role in this process, our study may provide novel insights into the maturation mechanism of retroviral Envs.
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A novel human endogenous retroviral protein inhibits cell-cell fusion. Sci Rep 2013; 3:1462. [PMID: 23492904 PMCID: PMC3598002 DOI: 10.1038/srep01462] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Accepted: 02/28/2013] [Indexed: 11/30/2022] Open
Abstract
While common in viral infections and neoplasia, spontaneous cell-cell fusion, or syncytialization, is quite restricted in healthy tissues. Such fusion is essential to human placental development, where interactions between trophoblast-specific human endogenous retroviral (HERV) envelope proteins, called syncytins, and their widely-distributed cell surface receptors are centrally involved. We have identified the first host cell-encoded protein that inhibits cell fusion in mammals. Like the syncytins, this protein, called suppressyn, is HERV-derived, placenta-specific and well-conserved over simian evolution. In vitro, suppressyn binds to the syn1 receptor and inhibits syn1-, but not syn2-mediated trophoblast syncytialization. Suppressyn knock-down promotes cell-cell fusion in trophoblast cells and cell-associated and secreted suppressyn binds to the syn1 receptor, ASCT2. Identification of the first host cell-encoded inhibitor of mammalian cell fusion may encourage improved understanding of cell fusion mechanisms, of placental morphogenesis and of diseases resulting from abnormal cell fusion.
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Nakagawa S, Bai H, Sakurai T, Nakaya Y, Konno T, Miyazawa T, Gojobori T, Imakawa K. Dynamic evolution of endogenous retrovirus-derived genes expressed in bovine conceptuses during the period of placentation. Genome Biol Evol 2013; 5:296-306. [PMID: 23335121 PMCID: PMC3590765 DOI: 10.1093/gbe/evt007] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
In evolution of mammals, some of essential genes for placental development are known to be of retroviral origin, as syncytin-1 derived from an envelope (env) gene of an endogenous retrovirus (ERV) aids in the cell fusion of placenta in humans. Although the placenta serves the same function in all placental mammals, env-derived genes responsible for trophoblast cell fusion and maternal immune tolerance differ among species and remain largely unidentified in the bovine species. To examine env-derived genes playing a role in the bovine placental development comprehensively, we determined the transcriptomic profiles of bovine conceptuses during three crucial windows of implantation periods using a high-throughput sequencer. The sequence reads were mapped into the bovine genome, in which ERV candidates were annotated using RetroTector© (7,624 and 1,542 for ERV-derived and env-derived genes, respectively). The mapped reads showed that approximately 18% (284 genes) of env-derived genes in the genome were expressed during placenta formation, and approximately 4% (63 genes) were detected for all days examined. We verified three env-derived genes that are expressed in trophoblast cells by polymerase chain reaction. Out of these three, the sequence of env-derived gene with the longest open reading frame (named BERV-P env) was found to show high expression levels in trophoblast cell lines and to be similar to those of syncytin-Car1 genes found in dogs and cats, despite their disparate origins. These results suggest that placentation depends on various retrovirus-derived genes that could have replaced endogenous predecessors during evolution.
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Affiliation(s)
- So Nakagawa
- Center for Information Biology, National Institute of Genetics, Japan
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Wang LJ, Cheong ML, Lee YS, Lee MT, Chen H. High-temperature requirement protein A4 (HtrA4) suppresses the fusogenic activity of syncytin-1 and promotes trophoblast invasion. Mol Cell Biol 2012; 32:3707-17. [PMID: 22778138 PMCID: PMC3430202 DOI: 10.1128/mcb.00223-12] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Accepted: 07/03/2012] [Indexed: 11/20/2022] Open
Abstract
Cell-cell fusion and cell invasion are essential for placental development. Human cytotrophoblasts in the chorionic villi may undergo cell-cell fusion to form syncytiotrophoblasts to facilitate nutrient-gas exchange or differentiate into extravillous trophoblasts (EVTs) to facilitate maternal-fetal circulation. The placental transcription factor glial cells missing 1 (GCM1) regulates syncytin-1 and -2 expression to mediate trophoblast fusion. Interestingly, GCM1 and syncytin-1 are also expressed in EVTs with unknown physiological functions. In this study, we performed chromatin immunoprecipitation-on-chip (ChIP-chip) analysis and identified the gene for high-temperature requirement protein A4 (HtrA4) as a GCM1 target gene, which encodes a serine protease facilitating cleavage of fibronectin and invasion of placental cells. Importantly, HtrA4 is immunolocalized in EVTs at the maternal-fetal interface, and its expression is decreased by hypoxia and in preeclampsia, a pregnancy complication associated with placental hypoxia and shallow trophoblast invasion. We further demonstrate that HtrA4 interacts with syncytin-1 and suppresses cell-cell fusion. Therefore, HtrA4 may be crucial for EVT differentiation by playing a dual role in prevention of cell-cell fusion of EVTs and promotion of their invasion into the uterus. Our study reveals a novel function of GCM1 and HtrA4 in regulation of trophoblast invasion and that abnormal HrtA4 expression may contribute to shallow trophoblast invasion in preeclampsia.
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Affiliation(s)
- Liang-Jie Wang
- Graduate Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan
| | - Mei-Leng Cheong
- Graduate Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan
- Department of Obstetrics and Gynecology, Cathay General Hospital, Taipei, Taiwan
| | - Yun-Shien Lee
- Department of Biotechnology, Ming Chuan University, Tao-Yuan, Taiwan
| | - Ming-Ting Lee
- Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei, Taiwan
| | - Hungwen Chen
- Graduate Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan
- Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei, Taiwan
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Avinoam O, Podbilewicz B. Eukaryotic cell-cell fusion families. CURRENT TOPICS IN MEMBRANES 2012; 68:209-34. [PMID: 21771501 DOI: 10.1016/b978-0-12-385891-7.00009-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Ori Avinoam
- Department of Biology, Technion, Israel Institute of Technology, Haifa, Israel
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Søe K, Andersen TL, Hobolt-Pedersen AS, Bjerregaard B, Larsson LI, Delaissé JM. Involvement of human endogenous retroviral syncytin-1 in human osteoclast fusion. Bone 2011; 48:837-46. [PMID: 21111077 DOI: 10.1016/j.bone.2010.11.011] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2010] [Revised: 11/08/2010] [Accepted: 11/13/2010] [Indexed: 10/18/2022]
Abstract
Generation of osteoclasts through fusion of mono-nucleated precursors is a key event of bone physiology and bone resorption is inefficient without osteoclast fusion. Several factors playing a critical role in the fusion process have already been recognized, but the factors involved in the actual fusion of the lipid bilayers of their cell membranes are still unknown. Syncytin-1 is a protein encoded by a human endogenous retroviral gene which was stably integrated into the human ancestor genome more than 24 million years ago. Upon activation, syncytin-1 is able to destabilize the lipid bilayer of the target cell and to force the merging of plasma membranes. This protein is a key player in the fusion of cytotrophoblasts. In the present study, syncytin-1 as well as its putative receptor ASCT2 was found to be expressed in differentiating osteoclasts in vitro, both on mRNA and protein level. This was documented through Q-PCR, Western blot and immunofluorescence analyses. These in vitro findings were confirmed by immunohistochemical stainings in human iliac crest biopsies. A syncytin-1 inhibitory peptide reduced the number of nuclei per osteoclast by 30%, as well as TRACP activity. From a mechanistic point of view, it is interesting that the distribution of syncytin-1 immunoreactivity on the cell surface parallels that of actin, another important player in cell fusion, and that cell-cell proximity induces particular patterns of distribution of syncytin-1 and actin in the respective cells. These complementary observations support a critical role of syncytin-1 in osteoclast fusion, which is of special interest in view of its well-known ability to force the merging of plasma membranes.
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Affiliation(s)
- Kent Søe
- Department of Clinical Cell Biology, Vejle Hospital, IRS/CSFU, University of Southern Denmark, Kabbeltoft 25, 7100 Vejle, Denmark.
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New Insights into the Mechanisms and Roles of Cell–Cell Fusion. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2011; 289:149-209. [DOI: 10.1016/b978-0-12-386039-2.00005-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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Benaitreau D, Santos ED, Leneveu MC, De Mazancourt P, Pecquery R, Dieudonné MN. Adiponectin promotes syncytialisation of BeWo cell line and primary trophoblast cells. Reprod Biol Endocrinol 2010; 8:128. [PMID: 21034435 PMCID: PMC2987948 DOI: 10.1186/1477-7827-8-128] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Accepted: 10/29/2010] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND In human pregnancy, a correct placentation depends on trophoblast proliferation, differentiation, migration and invasion. These processes are highly regulated by placental hormones, growth factors and cytokines. Recently, we have shown that adiponectin, an adipokine, has anti-proliferative effects on trophoblastic cells. Here, we complete this study by demonstrating that adiponectin modulates BeWo and human villous cytotrophoblast cell differentiation. RESULTS We showed that hCG secretion was up-regulated by adiponectin treatment in both BeWo cells and human cytotrophoblasts from very early placentas (5-6 weeks). The expression of two trophoblast differentiation markers, leptin and syncytin 2, was also up-regulated by adiponectin in BeWo cells. Moreover, adiponectin treatment induced a loss of E-cadherin staining in these cells. In parallel, we demonstrated that AdipoR1 and AdipoR2 are up-regulated during forskolin induced BeWo cell differentiation, reinforcing the role of adiponectin in trophoblast syncytialization. SiRNA mediated down-regulation of AdipoR1 and AdipoR2 was used to demonstrate that adiponectin effects on differentiation were essentially mediated by these receptors. Finally, using a specific inhibitor, we demonstrated that the PKA signalling pathway could be one pathway involved in adiponectin effects on trophoblast differentiation. CONCLUSION Adiponectin enhances the differentiation process of trophoblast cells and could thus be involved in functional syncytiotrophoblast formation.
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Affiliation(s)
- Delphine Benaitreau
- Université de Versailles-St Quentin, Service de Biochimie et Biologie Moléculaire, UPRES-EA 2493, Faculté de Médecine Paris-Ile de France Ouest, PRES Universud Paris, Centre Hospitalier de Poissy-Saint Germain, 78303 Poissy Cedex, France
| | - Esther Dos Santos
- Université de Versailles-St Quentin, Service de Biochimie et Biologie Moléculaire, UPRES-EA 2493, Faculté de Médecine Paris-Ile de France Ouest, PRES Universud Paris, Centre Hospitalier de Poissy-Saint Germain, 78303 Poissy Cedex, France
| | - Marie-Christine Leneveu
- Université de Versailles-St Quentin, Service de Biochimie et Biologie Moléculaire, UPRES-EA 2493, Faculté de Médecine Paris-Ile de France Ouest, PRES Universud Paris, Centre Hospitalier de Poissy-Saint Germain, 78303 Poissy Cedex, France
| | - Philippe De Mazancourt
- Université de Versailles-St Quentin, Service de Biochimie et Biologie Moléculaire, UPRES-EA 2493, Faculté de Médecine Paris-Ile de France Ouest, PRES Universud Paris, Centre Hospitalier de Poissy-Saint Germain, 78303 Poissy Cedex, France
| | - René Pecquery
- Université de Versailles-St Quentin, Service de Biochimie et Biologie Moléculaire, UPRES-EA 2493, Faculté de Médecine Paris-Ile de France Ouest, PRES Universud Paris, Centre Hospitalier de Poissy-Saint Germain, 78303 Poissy Cedex, France
| | - Marie-Noëlle Dieudonné
- Université de Versailles-St Quentin, Service de Biochimie et Biologie Moléculaire, UPRES-EA 2493, Faculté de Médecine Paris-Ile de France Ouest, PRES Universud Paris, Centre Hospitalier de Poissy-Saint Germain, 78303 Poissy Cedex, France
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Liang CY, Wang LJ, Chen CP, Chen LF, Chen YH, Chen H. GCM1 Regulation of the Expression of Syncytin 2 and Its Cognate Receptor MFSD2A in Human Placenta1. Biol Reprod 2010; 83:387-95. [DOI: 10.1095/biolreprod.110.083915] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
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Role of HERV-W syncytin-1 in placentation and maintenance of human pregnancy. Appl Immunohistochem Mol Morphol 2009; 17:319-28. [PMID: 19407656 DOI: 10.1097/pai.0b013e31819640f9] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Over half of human genome contains retroelements, including retrotransposons, retroviruses, and other elements. Human endogenous retroviruses (HERVs) comprise about 8% of human genome. The products of 2 of 16 identified genes of HERV-W seem to play a pivotal role in the placentation. These 2 genes are HERV-W env glycoprotein (syncytin-1) and HERV-FRD env glycoprotein (syncytin-2). It has been shown previously that syncytin-1 mediates cell-cell fusions of cytotrophoblasts into syncytiotrophoblasts. In addition, HERV-W env contains an immunosuppressive region that may prevent rejection of a semiallogenic fetus from the mother's immune system. We analyzed 40 full-term placental tissues to localize the expression of syncytin-1-ISR by immunohistochemical staining and by reverse trancscriptase (RT) in situ polymerase chain reaction (PCR). Both the immunostaining and in situ RT-PCR showed strong expression of syncytin-1 in the syncytiotrophoblast layer from the full-term placental tissues. To further analyze the mechanism of early embryo HERV-W env activation, we utilized a HTR-8/SVneo cell line developed from first trimester human trophoblasts and subjected them to various physiologic concentrations of maternal hormones. Quantitative RT-PCR analyses demonstrated that exposure to progesterone significantly upregulated the HERV-W env expression, whereas several other hormones apparently played lesser roles. In conclusion, our findings suggest that expression of syncytin-1 (HERV-W env) in utero is expressed exclusively in the syncytiotrophoblast layer and is upregulated by progesterone.
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Ahn K, Kim HS. Structural and quantitative expression analyses of HERV gene family in human tissues. Mol Cells 2009; 28:99-103. [PMID: 19669627 DOI: 10.1007/s10059-009-0107-y] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2009] [Revised: 06/11/2009] [Accepted: 06/24/2009] [Indexed: 10/20/2022] Open
Abstract
Human endogenous retroviruses (HERVs) have been implicated in the pathogenesis of several human diseases as multi-copy members in the human genome. Their gene expression profiling could provide us with important insights into the pathogenic relationship between HERVs and cancer. In this study, we have evaluated the genomic structure and quantitatively determined the expression patterns in the env gene of a variety of HERV family members located on six specific loci by the RetroTector 10 program, as well as real-time RT-PCR amplification. The env gene transcripts evidenced significant differences in the human tumor/normal adjacent tissues (colon, liver, uterus, lung and testis). As compared to the adjacent normal tissues, high levels of expression were noted in testis tumor tissues for HERV-K, in liver and lung tumor tissues for HERV-R, in liver, lung, and testis tumor tissues for HERV-H, and in colon and liver tumor tissues for HERV-P. These data warrant further studies with larger groups of patients to develop biomarkers for specific human cancers.
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MESH Headings
- Chromosome Mapping
- Chromosomes, Human, Pair 12/genetics
- Chromosomes, Human, Pair 14/genetics
- Chromosomes, Human, Pair 2/genetics
- Chromosomes, Human, Pair 7/genetics
- Colon/virology
- Endogenous Retroviruses/classification
- Endogenous Retroviruses/genetics
- Female
- Gene Expression Profiling
- Gene Expression Regulation, Viral
- Genome, Human/genetics
- Genome, Viral/genetics
- Humans
- Liver/virology
- Lung/virology
- Male
- Neoplasms/genetics
- Neoplasms/pathology
- Neoplasms/virology
- Reverse Transcriptase Polymerase Chain Reaction
- Species Specificity
- Testis/virology
- Uterus/virology
- Viral Envelope Proteins/genetics
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Affiliation(s)
- Kung Ahn
- Department of Biological Sciences, College of Natural Sciences, Pusan National University, Busan, 609-735, Korea
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Chen CP, Chen LF, Yang SR, Chen CY, Ko CC, Chang GD, Chen H. Functional characterization of the human placental fusogenic membrane protein syncytin 2. Biol Reprod 2008; 79:815-23. [PMID: 18650494 DOI: 10.1095/biolreprod.108.069765] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Fusion of cytotrophoblasts into the multinucleated syncytiotrophoblast layer is essential for the development of a functional placenta. The envelope protein of a human endogenous retrovirus W (HERV-W) family member, syncytin 1, has been shown to mediate placental cell fusion. Recently, the envelope protein of another HERV family member (HERV-FRD), syncytin 2, has been identified and shown to be highly expressed in the placenta. To better understand the biology of syncytin 2, in this study we first investigated syncytin 2 gene expression in normal and preeclamptic placentas and then characterized the functions of syncytin 2. The expression of syncytin 2 gene was decreased in preeclamptic placentas and could be stimulated by the cAMP stimulant forskolin. The endoprotease furin was found to be involved in the posttranslational cleavage of syncytin 1 and 2 polypeptides into surface and transmembrane subunits. In addition, proper association of the subunits of syncytins 1 and 2 is probably required for the functional integrity of each protein, because subunit swapping of syncytins 1 and 2 failed to generate fusogenic chimeras. Finally, we demonstrated that the disulfide bridge-forming CX(2)C and CX(7)C motifs found in syncytins 1 and 2 are essential for their fusogenic activities, because mutations in the CX(2)C motif not only abolished fusogenesis but also functioned as dominant-negative mutants. Our results suggest that syncytin 2 may function as a second fusogenic protein for placental cell fusion.
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Affiliation(s)
- Chie-Pein Chen
- Division of High Risk Pregnancy and Department of Medical Research, Mackay Memorial Hospital, Taipei 104, Taiwan
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44
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Abstract
Cell fusions are important to fertilization, placentation, development of skeletal muscle and bone, calcium homeostasis and the immune defense system. Additionally, cell fusions participate in tissue repair and may be important to cancer development and progression. A large number of factors appear to regulate cell fusions, including receptors and ligands, membrane domain organizing proteins, proteases, signaling molecules and fusogenic proteins forming alpha-helical bundles that bring membranes close together. The syncytin family of proteins represent true fusogens and the founding member, syncytin-1, has been documented to be involved in fusions between placental trophoblasts, between cancer cells and between cancer cells and host cells. We review the literature with emphasis on the syncytin family and propose that syncytins may represent universal fusogens in primates and rodents, which work together with a number of other proteins to regulate the cell fusion machinery.
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Abstract
It has been known for more than 150 years that syncytial fusion is a normal feature in biological systems. In humans there are two larger syncytial tissues: skeletal muscles fibers and placental syncytiotrophoblast. Other fusion events take place as well from fertilization of the oocyte to infection of human cells by enveloped viruses (however, the latter does not necessarily lead to syncytium formation).Although knowledge of the fusion process is incomplete, it is clear that membranes do not fuse easily; specific proteins and other factors are required and are selectively activated. In this chapter, we describe the classic proteins, such as the syncytins, assumed to be involved in the fusion process. We also describe other factors that may play roles in the fusion process or in the preparation of the cells to fuse, such as charged phospholipids, divalent cations, and intracellular proteases. Finally, we speculate on why trophoblast cells fuse in vitro and deal with in vitro models of trophoblast fusion and how their fusion rates can be quantified.
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Affiliation(s)
- Berthold Huppertz
- Institute of Cell Biology, Histology and Embryology, Center of Molecular Medicine, Medical University of Graz, Graz, Austria
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46
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Abstract
A healthy syncytium in the placenta is vital to a successful pregnancy. The trophoblast builds up the natural barrier between the mother and the developing fetus and is the site of gas, nutrition, and waste exchange. An inadequate formation of this tissue leads to several pathologies of pregnancy, which may result in fetal death during the second trimester or iatrogenic preterm delivery due to intrauterine growth restriction, preeclampsia, or abruption.Cytotrophoblastic cells fuse constantly with the overlying syncytiotrophoblast/syncytium to maintain the function of the trophoblast. Syncytin-1 is the only molecule known to directly induce fusion in the placental trophoblast. Many other proteins, such as gap junctions (e.g., connexin 40) and transcription factors, play a role in the molecular pathways directing the trophoblast turn over. Despite the significance of this process for successful placentation, the mechanisms regulating its activity remain poorly understood.In this chapter we present several different model systems that can be utilized to investigate the regulation of the cell fusion process in the trophoblast. We describe cell-based assays as well as tissue-related protocols. We show how fusion can be monitored in (1) BeWo cells as a trophoblast cell line model, (2) HEK239 using syncytin-1 as a fusion molecule, and (3) a floating villi explant model. Furthermore, we will present strategies to inhibit fusion in the different models. These techniques represent powerful tools to study the molecular mediators of cell fusion in the trophoblast.
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Affiliation(s)
- Sascha Drewlo
- Womens and Infants Health, Samuel Lunenfeld Research Institute, Department of Obstetrics and Gynaecology, Mount Sinai Hospital, University of Toronto, Ontario, Canada
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47
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Chou CC, Chang C, Liu JH, Chen LF, Hsiao CD, Chen H. Small ubiquitin-like modifier modification regulates the DNA binding activity of glial cell missing Drosophila homolog a. J Biol Chem 2007; 282:27239-27249. [PMID: 17646165 DOI: 10.1074/jbc.m700351200] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glial cell missing Drosophila homolog a (GCMa) is an essential transcription factor for placental development, which controls the differentiation of the syncytiotrophoblast layer. Although the activity of GCMa can be post-translationally regulated by protein phosphorylation, ubiquitination, and acetylation, it is unknown whether GCMa activity can be regulated by sumoylation. In this report, we investigated the role of sumoylation in the regulation of GCMa activity. We demonstrated that Ubc9, the E2 component of the sumoylation machinery, specifically interacts with the N-terminal domain of GCMa and promotes GCMa sumoylation on lysine 156. Moreover, GCMa-mediated transcriptional activation was repressed by sumoylation but was enhanced in the presence of the SUMO-specific protease, SENP1. The repressive effect of sumoylation on GCMa transcriptional activity was attributed to decreased DNA binding activity of GCMa. Furthermore, structural analysis revealed a steric clash between the SUMO1 moiety of sumoylated GCMa and the DNA-binding surfaces of GCMa, which may destabilize the interaction between GCMa and its cognate DNA sequence. Our study demonstrates that GCMa is a new sumoylation substrate and its activity is down-regulated by sumoylation.
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Affiliation(s)
- Chih-Chine Chou
- Graduate Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan, the
| | - Chingwen Chang
- Graduate Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan, the
| | - Jyung-Hurng Liu
- Institute of Molecular Biology, Academia Sinica, Nankang, Taipei 115, Taiwan, and the
| | - Liang-Fu Chen
- Graduate Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan, the
| | - Chwan-Deng Hsiao
- Institute of Molecular Biology, Academia Sinica, Nankang, Taipei 115, Taiwan, and the
| | - Hungwen Chen
- Graduate Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan, the; Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei 115, Taiwan.
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Peng X, Pan J, Gong R, Liu Y, Kang S, Feng H, Qiu G, Guo D, Tien P, Xiao G. Functional Characterization of Syncytin-A, a Newly Murine Endogenous Virus Envelope Protein. J Biol Chem 2007; 282:381-9. [PMID: 17105734 DOI: 10.1074/jbc.m606353200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Trophoblast fusion in placenta is an important event for preservation of a healthy pregnancy. This process takes place throughout the pregnancy and is crucial for the formation of syncytiotrophoblast layer. Syncytin-1 and syncytin-2 are strong candidate regulators of fusion from retroviral origin. Syncytin-A and syncytin-B are other candidates from retroviral origin in Muridae. The active role of syncytin in driving fusion of trophoblast has been identified, but its fusion mechanism is still unclear. As an intact retroviral envelope protein, syncytin-A shares similar structure profiling with other viral envelope fusion proteins, especially in the regions of N- and C-terminal heptad repeats (NHR and CHR, respectively). In this paper, we showed that SynA 1 + 2 of syncytin-A (residues 445-536, including predicted NHR, CHR, and a natural linker) could form trimer and exhibited significant alpha-helix structure and high thermo-stability. Limited proteolysis result identified a stable protease-resistant core of SynA 1 + 2, which was in good agreement with computational modeling data. NHR and CHR could interact with each other in vitro, too. Different from the previous studies, the disulfide-bonded linker was apparently vital to the stability of fusion core structure. By biological assays, NHR was shown to be inhibitive to cell-cell fusion, with IC(50) value about 5.4 microm, but CHR seemed to have no inhibitory activity even at 50 microm. From both biochemical and functional data, we first gave an explanation how syncytin-A mediated cell fusion. The insight into the mechanism of syncytin-A-mediated cell-cell fusion may provide a crucial clue to placental cytotrophoblast morphogenesis.
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Affiliation(s)
- Xiaoxue Peng
- State Key Laboratory of Virology and Modern Virology Research Centre, College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China
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Drewlo S, Leyting S, Kokozidou M, Mallet F, Pötgens AJG. C-Terminal truncations of syncytin-1 (ERVWE1 envelope) that increase its fusogenicity. Biol Chem 2006; 387:1113-20. [PMID: 16895482 DOI: 10.1515/bc.2006.137] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Syncytin-1, the envelope protein of ERVWE1, an endogenous retrovirus of the HERV-W family, plays an important role in regulating fusion of the placental trophoblast. At least one of its receptors is expressed on a variety of human cell types. Its ability to fuse cells makes it an attractive candidate molecule in gene therapy against cancer. We studied the relevance of sequences in the cytoplasmic tail of syncytin-1 for inducing cell-cell fusion. We generated a series of C-terminally truncated syncytin-1 variants. Sequences immediately adjacent to the transmembrane region of syncytin-1 were necessary for inducing optimal fusion, whereas the extreme C-terminus of syncytin-1 partially inhibited its fusogenicity. Two variants of syncytin-1, truncated after residues 483 and 515, were significantly hyperfusogenic compared to wild-type syncytin-1. Cellular and cell-surface expression levels of these two variant proteins were similar to those of wild-type syncytin-1. In testing the latter we found that only a very minor portion of recombinantly expressed cellular syncytin-1 was fully mature and expressed on the cell surface. Our results contribute to the understanding of the structure-function relationship of syncytin-1, and might have implications for the use of this molecule in gene therapy.
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Affiliation(s)
- Sascha Drewlo
- Institute of Anatomy II, University Hospital, Wendlingweg 2, RWTH Aachen, D-52057 Aachen, Germany.
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50
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Cheynet V, Oriol G, Mallet F. Identification of the hASCT2-binding domain of the Env ERVWE1/syncytin-1 fusogenic glycoprotein. Retrovirology 2006; 3:41. [PMID: 16820059 PMCID: PMC1524976 DOI: 10.1186/1742-4690-3-41] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2006] [Accepted: 07/04/2006] [Indexed: 12/26/2022] Open
Abstract
The cellular HERV-W envelope/syncytin-1 protein, encoded by the envelope gene of the ERVWE1 proviral locus is a fusogenic glycoprotein probably involved in the formation of the placental syncytiotrophoblast layer. Syncytin-1-induced in vitro cell-cell fusion is dependent on the interaction with hASCT2. As no receptor binding domain has been clearly defined in the SU of neither the HERV-W Env nor the retroviruses of the same interference group, we designed an in vitro binding assay to evaluate the interaction of the HERV-W envelope with the hASCT2 receptor. Using truncated HERV-W SU subunits, a region consisting of the N-terminal 124 amino acids of the mature SU glycoprotein was determined as the minimal receptor-binding domain. This domain contains several sub-domains which are poorly conserved among retroviruses of this interference group but a region of 18 residus containing the SDGGGX2DX2R conserved motif was proved to be essential for syncytin-1-hASCT2 interaction.
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Affiliation(s)
- Valérie Cheynet
- UMR 2714 CNRS-bioMérieux, IFR128 BioSciences Lyon-Gerland, Ecole Normale Supérieure de Lyon, 69364 Lyon Cedex 07, France
| | - Guy Oriol
- UMR 2714 CNRS-bioMérieux, IFR128 BioSciences Lyon-Gerland, Ecole Normale Supérieure de Lyon, 69364 Lyon Cedex 07, France
| | - François Mallet
- UMR 2714 CNRS-bioMérieux, IFR128 BioSciences Lyon-Gerland, Ecole Normale Supérieure de Lyon, 69364 Lyon Cedex 07, France
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