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Elofsson A, Han L, Bianchi E, Wright GJ, Jovine L. Deep learning insights into the architecture of the mammalian egg-sperm fusion synapse. eLife 2024; 13:RP93131. [PMID: 38666763 PMCID: PMC11052572 DOI: 10.7554/elife.93131] [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: 04/28/2024] Open
Abstract
A crucial event in sexual reproduction is when haploid sperm and egg fuse to form a new diploid organism at fertilization. In mammals, direct interaction between egg JUNO and sperm IZUMO1 mediates gamete membrane adhesion, yet their role in fusion remains enigmatic. We used AlphaFold to predict the structure of other extracellular proteins essential for fertilization to determine if they could form a complex that may mediate fusion. We first identified TMEM81, whose gene is expressed by mouse and human spermatids, as a protein having structural homologies with both IZUMO1 and another sperm molecule essential for gamete fusion, SPACA6. Using a set of proteins known to be important for fertilization and TMEM81, we then systematically searched for predicted binary interactions using an unguided approach and identified a pentameric complex involving sperm IZUMO1, SPACA6, TMEM81 and egg JUNO, CD9. This complex is structurally consistent with both the expected topology on opposing gamete membranes and the location of predicted N-glycans not modeled by AlphaFold-Multimer, suggesting that its components could organize into a synapse-like assembly at the point of fusion. Finally, the structural modeling approach described here could be more generally useful to gain insights into transient protein complexes difficult to detect experimentally.
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Affiliation(s)
- Arne Elofsson
- Science for Life Laboratory and Department of Biochemistry and Biophysics, Stockholm UniversitySolnaSweden
| | - Ling Han
- Department of Biosciences and Nutrition, Karolinska InstitutetHuddingeSweden
| | - Enrica Bianchi
- Department of Biology, Hull York Medical School, York Biomedical Research Institute, University of YorkYorkUnited Kingdom
| | - Gavin J Wright
- Department of Biology, Hull York Medical School, York Biomedical Research Institute, University of YorkYorkUnited Kingdom
| | - Luca Jovine
- Department of Biosciences and Nutrition, Karolinska InstitutetHuddingeSweden
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2
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Brukman NG, Valansi C, Podbilewicz B. Sperm induction of somatic cell-cell fusion as a novel functional test. eLife 2024; 13:e94228. [PMID: 38265078 PMCID: PMC10883674 DOI: 10.7554/elife.94228] [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: 11/07/2023] [Accepted: 01/12/2024] [Indexed: 01/25/2024] Open
Abstract
The fusion of mammalian gametes requires the interaction between IZUMO1 on the sperm and JUNO on the oocyte. We have recently shown that ectopic expression of mouse IZUMO1 induces cell-cell fusion and that sperm can fuse to fibroblasts expressing JUNO. Here, we found that the incubation of mouse sperm with hamster fibroblasts or human epithelial cells in culture induces the fusion between these somatic cells and the formation of syncytia, a pattern previously observed with some animal viruses. This sperm-induced cell-cell fusion requires a species-matching JUNO on both fusing cells, can be blocked by an antibody against IZUMO1, and does not rely on the synthesis of new proteins. The fusion is dependent on the sperm's fusogenic capacity, making this a reliable, fast, and simple method for predicting sperm function during the diagnosis of male infertility.
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Affiliation(s)
- Nicolas G Brukman
- Department of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Clari Valansi
- Department of Biology, Technion-Israel Institute of Technology, Haifa, Israel
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3
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Azimi FC, Dean TT, Minari K, Basso LGM, Vance TDR, Serrão VHB. A Frame-by-Frame Glance at Membrane Fusion Mechanisms: From Viral Infections to Fertilization. Biomolecules 2023; 13:1130. [PMID: 37509166 PMCID: PMC10377500 DOI: 10.3390/biom13071130] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 07/09/2023] [Accepted: 07/12/2023] [Indexed: 07/30/2023] Open
Abstract
Viral entry and fertilization are distinct biological processes that share a common mechanism: membrane fusion. In viral entry, enveloped viruses attach to the host cell membrane, triggering a series of conformational changes in the viral fusion proteins. This results in the exposure of a hydrophobic fusion peptide, which inserts into the host membrane and brings the viral and host membranes into close proximity. Subsequent structural rearrangements in opposing membranes lead to their fusion. Similarly, membrane fusion occurs when gametes merge during the fertilization process, though the exact mechanism remains unclear. Structural biology has played a pivotal role in elucidating the molecular mechanisms underlying membrane fusion. High-resolution structures of the viral and fertilization fusion-related proteins have provided valuable insights into the conformational changes that occur during this process. Understanding these mechanisms at a molecular level is essential for the development of antiviral therapeutics and tools to influence fertility. In this review, we will highlight the biological importance of membrane fusion and how protein structures have helped visualize both common elements and subtle divergences in the mechanisms behind fusion; in addition, we will examine the new tools that recent advances in structural biology provide researchers interested in a frame-by-frame understanding of membrane fusion.
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Affiliation(s)
- Farshad C. Azimi
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada;
| | - Trevor T. Dean
- Pharmaceutical Sciences, University of Illinois Chicago, Chicago, IL 60612, USA;
| | - Karine Minari
- Biomolecular Cryo-Electron Microscopy Facility, University of California-Santa Cruz, Santa Cruz, CA 95064, USA;
| | - Luis G. M. Basso
- Laboratório de Ciências Físicas, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Rio de Janeiro 28013-602, Brazil;
| | - Tyler D. R. Vance
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada;
| | - Vitor Hugo B. Serrão
- Biomolecular Cryo-Electron Microscopy Facility, University of California-Santa Cruz, Santa Cruz, CA 95064, USA;
- Department of Chemistry and Biochemistry, University of California-Santa Cruz, Santa Cruz, CA 95064, USA
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4
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Gert KRB, Panser K, Surm J, Steinmetz BS, Schleiffer A, Jovine L, Moran Y, Kondrashov F, Pauli A. Divergent molecular signatures in fish Bouncer proteins define cross-fertilization boundaries. Nat Commun 2023; 14:3506. [PMID: 37316475 DOI: 10.1038/s41467-023-39317-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Accepted: 06/05/2023] [Indexed: 06/16/2023] Open
Abstract
Molecular compatibility between gametes is a prerequisite for successful fertilization. As long as a sperm and egg can recognize and bind each other via their surface proteins, gamete fusion may occur even between members of separate species, resulting in hybrids that can impact speciation. The egg membrane protein Bouncer confers species specificity to gamete interactions between medaka and zebrafish, preventing their cross-fertilization. Here, we leverage this specificity to uncover distinct amino acid residues and N-glycosylation patterns that differentially influence the function of medaka and zebrafish Bouncer and contribute to cross-species incompatibility. Curiously, in contrast to the specificity observed for medaka and zebrafish Bouncer, seahorse and fugu Bouncer are compatible with both zebrafish and medaka sperm, in line with the pervasive purifying selection that dominates Bouncer's evolution. The Bouncer-sperm interaction is therefore the product of seemingly opposing evolutionary forces that, for some species, restrict fertilization to closely related fish, and for others, allow broad gamete compatibility that enables hybridization.
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Affiliation(s)
- Krista R B Gert
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, 1030, Vienna, Austria
- Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, 1030, Vienna, Austria
| | - Karin Panser
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, 1030, Vienna, Austria
| | - Joachim Surm
- Department of Ecology, Evolution and Behavior, Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, 9190401, Jerusalem, Israel
| | - Benjamin S Steinmetz
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, 1030, Vienna, Austria
- Institute of Molecular Systems Biology, Department of Biology, ETH Zürich, 8093, Zürich, Switzerland
| | - Alexander Schleiffer
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, 1030, Vienna, Austria
| | - Luca Jovine
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden
| | - Yehu Moran
- Department of Ecology, Evolution and Behavior, Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, 9190401, Jerusalem, Israel
| | - Fyodor Kondrashov
- Institute of Science and Technology Austria, Klosterneuburg, Austria
- Evolutionary and Synthetic Biology Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Andrea Pauli
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, 1030, Vienna, Austria.
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5
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Dittmar T, Hass R. Intrinsic signalling factors associated with cancer cell-cell fusion. Cell Commun Signal 2023; 21:68. [PMID: 37016404 PMCID: PMC10071245 DOI: 10.1186/s12964-023-01085-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Accepted: 02/21/2023] [Indexed: 04/06/2023] Open
Abstract
Cellular fusion e.g. between cancer cells and normal cells represents a stepwise process that is tightly regulated. During a pre-hybrid preparation program somatic cells and/or cancer cells are promoted to a pro-fusogenic state as a prerequisite to prepare a fusion process. A pro-fusogenic state requires significant changes including restructure of the cytoskeleton, e.g., by the formation of F-actin. Moreover, distinct plasma membrane lipids such as phosphatidylserine play an important role during cell fusion. In addition, the expression of distinct fusogenic factors such as syncytins and corresponding receptors are of fundamental importance to enable cellular mergers. Subsequent hybrid formation and fusion are followed by a post-hybrid selection process. Fusion among normal cells is important and often required during organismal development. Cancer cells fusion appears more rarely and is associated with the generation of new cancer hybrid cell populations. These cancer hybrid cells contribute to an elevated tumour plasticity by altered metastatic behaviour, changes in therapeutic and apoptotic responses, and even in the formation of cancer stem/ initiating cells. While many parts within this multi-step cascade are still poorly understood, this review article predominantly focusses on the intracellular necessities for fusion among cancer cells or with other cell populations of the tumour microenvironment. Video Abstract.
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Affiliation(s)
- Thomas Dittmar
- Institute of Immunology, Centre for Biomedical Education and Research (ZBAF), Witten/Herdecke University, Stockumer Str. 10, 58448, Witten, Germany.
| | - Ralf Hass
- Biochemistry and Tumor Biology Laboratory, Department of Obstetrics and Gynaecology, Hannover Medical School, 30625, Hannover, Germany.
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6
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Brukman NG, Nakajima KP, Valansi C, Flyak K, Li X, Higashiyama T, Podbilewicz B. A novel function for the sperm adhesion protein IZUMO1 in cell-cell fusion. J Cell Biol 2022; 222:213693. [PMID: 36394541 PMCID: PMC9671554 DOI: 10.1083/jcb.202207147] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 10/11/2022] [Accepted: 11/07/2022] [Indexed: 11/18/2022] Open
Abstract
Mammalian sperm-egg adhesion depends on the trans-interaction between the sperm-specific type I glycoprotein IZUMO1 and its oocyte-specific GPI-anchored receptor JUNO. However, the mechanisms and proteins (fusogens) that mediate the following step of gamete fusion remain unknown. Using live imaging and content mixing assays in a heterologous system and structure-guided mutagenesis, we unveil an unexpected function for IZUMO1 in cell-to-cell fusion. We show that IZUMO1 alone is sufficient to induce fusion, and that this ability is retained in a mutant unable to bind JUNO. On the other hand, a triple mutation in exposed aromatic residues prevents this fusogenic activity without impairing JUNO interaction. Our findings suggest a second function for IZUMO1 as a unilateral mouse gamete fusogen.
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Affiliation(s)
- Nicolas G. Brukman
- Department of Biology, Technion - Israel Institute of Technology, Haifa, Israel
| | - Kohdai P. Nakajima
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Aichi, Japan
| | - Clari Valansi
- Department of Biology, Technion - Israel Institute of Technology, Haifa, Israel
| | - Kateryna Flyak
- Department of Biology, Technion - Israel Institute of Technology, Haifa, Israel
| | - Xiaohui Li
- Department of Biology, Technion - Israel Institute of Technology, Haifa, Israel
| | - Tetsuya Higashiyama
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Aichi, Japan,Institute of Transformative Bio-Molecules, Nagoya University, Nagoya, Aichi, Japan,Department of Biological Sciences, Graduate School of Science, University of Tokyo, Tokyo, Japan
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7
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Vance TDR, Yip P, Jiménez E, Li S, Gawol D, Byrnes J, Usón I, Ziyyat A, Lee JE. SPACA6 ectodomain structure reveals a conserved superfamily of gamete fusion-associated proteins. Commun Biol 2022; 5:984. [PMID: 36115925 PMCID: PMC9482655 DOI: 10.1038/s42003-022-03883-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 08/23/2022] [Indexed: 11/22/2022] Open
Abstract
SPACA6 is a sperm-expressed surface protein that is critical for gamete fusion during mammalian sexual reproduction. Despite this fundamental role, little is known about how SPACA6 specifically functions. We elucidated the crystal structure of the SPACA6 ectodomain at 2.2-Å resolution, revealing a two-domain protein containing a four-helix bundle and Ig-like β-sandwich connected via a quasi-flexible linker. This structure is reminiscent of IZUMO1, another gamete fusion-associated protein, making SPACA6 and IZUMO1 founding members of a superfamily of fertilization-associated proteins, herein dubbed the IST superfamily. The IST superfamily is defined structurally by its distorted four-helix bundle and a pair of disulfide-bonded CXXC motifs. A structure-based search of the AlphaFold human proteome identified more protein members to this superfamily; remarkably, many of these proteins are linked to gamete fusion. The SPACA6 structure and its connection to other IST-superfamily members provide a missing link in our knowledge of mammalian gamete fusion.
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Affiliation(s)
- Tyler D R Vance
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Patrick Yip
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Elisabet Jiménez
- Institute of Molecular Biology of Barcelona (IBMB-CSIC), 08028, Barcelona, Spain
| | - Sheng Li
- Department of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Diana Gawol
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - James Byrnes
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, USA
| | - Isabel Usón
- Institute of Molecular Biology of Barcelona (IBMB-CSIC), 08028, Barcelona, Spain
- ICREA, Pg. Lluís Companys 23, 08010, Barcelona, Spain
| | - Ahmed Ziyyat
- Université Paris Cité, CNRS, INSERM, Institut Cochin, F-75014, Paris, France
- Service d'Histologie, d'Embryologie, Biologie de la Reproduction, AP-HP, Hôpital Cochin, F-75014, Paris, France
| | - Jeffrey E Lee
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, Canada.
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8
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Matsumura T, Noda T, Satouh Y, Morohoshi A, Yuri S, Ogawa M, Lu Y, Isotani A, Ikawa M. Sperm IZUMO1 Is Required for Binding Preceding Fusion With Oolemma in Mice and Rats. Front Cell Dev Biol 2022; 9:810118. [PMID: 35096839 PMCID: PMC8790511 DOI: 10.3389/fcell.2021.810118] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2021] [Accepted: 12/21/2021] [Indexed: 01/28/2023] Open
Abstract
Fertilization occurs as the culmination of multi-step complex processes. First, mammalian spermatozoa undergo the acrosome reaction to become fusion-competent. Then, the acrosome-reacted spermatozoa penetrate the zona pellucida and adhere to and finally fuse with the egg plasma membrane. IZUMO1 is the first sperm protein proven to be essential for sperm-egg fusion in mammals, as Izumo1 knockout mouse spermatozoa adhere to but fail to fuse with the oolemma. However, the IZUMO1 function in other species remains largely unknown. Here, we generated Izumo1 knockout rats by CRISPR/Cas9 and found the male rats were infertile. Unlike in mice, Izumo1 knockout rat spermatozoa failed to bind to the oolemma. Further investigation revealed that the acrosome-intact sperm binding conceals a decreased number of the acrosome-reacted sperm bound to the oolemma in Izumo1 knockout mice. Of note, we could not see any apparent defects in the binding of the acrosome-reacted sperm to the oolemma in the mice lacking recently found fusion-indispensable genes, Fimp, Sof1, Spaca6, or Tmem95. Collectively, our data suggest that IZUMO1 is required for the sperm-oolemma binding prior to fusion at least in rat.
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Affiliation(s)
- Takafumi Matsumura
- Department of Experimental Genome Research, Research Institute for Microbial Diseases, Osaka University, Suita, Japan
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan
| | - Taichi Noda
- Department of Experimental Genome Research, Research Institute for Microbial Diseases, Osaka University, Suita, Japan
- Division of Reproductive Biology, Institute of Resource Development and Analysis, Kumamoto University, Kumamoto, Japan
- Priority Organization for Innovation and Excellence, Kumamoto University, Kumamoto, Japan
| | - Yuhkoh Satouh
- Department of Experimental Genome Research, Research Institute for Microbial Diseases, Osaka University, Suita, Japan
| | - Akane Morohoshi
- Department of Experimental Genome Research, Research Institute for Microbial Diseases, Osaka University, Suita, Japan
- Graduate School of Medicine, Osaka University, Suita, Japan
| | - Shunsuke Yuri
- Graduate School of Science and Technology, Nara Institute of Science and Technology, Ikoma, Japan
| | - Masaki Ogawa
- Department of Experimental Genome Research, Research Institute for Microbial Diseases, Osaka University, Suita, Japan
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan
| | - Yonggang Lu
- Department of Experimental Genome Research, Research Institute for Microbial Diseases, Osaka University, Suita, Japan
- Immunology Frontier Research Center, Osaka University, Suita, Japan
| | - Ayako Isotani
- Department of Experimental Genome Research, Research Institute for Microbial Diseases, Osaka University, Suita, Japan
- Graduate School of Science and Technology, Nara Institute of Science and Technology, Ikoma, Japan
- Immunology Frontier Research Center, Osaka University, Suita, Japan
| | - Masahito Ikawa
- Department of Experimental Genome Research, Research Institute for Microbial Diseases, Osaka University, Suita, Japan
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan
- Graduate School of Medicine, Osaka University, Suita, Japan
- Immunology Frontier Research Center, Osaka University, Suita, Japan
- Laboratory of Reproductive Systems Biology, Institute of Medical Science, The University of Tokyo, Tokyo, Japan
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9
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Binner MI, Kogan A, Panser K, Schleiffer A, Deneke VE, Pauli A. The Sperm Protein Spaca6 is Essential for Fertilization in Zebrafish. Front Cell Dev Biol 2022; 9:806982. [PMID: 35047514 PMCID: PMC8762341 DOI: 10.3389/fcell.2021.806982] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 12/07/2021] [Indexed: 12/27/2022] Open
Abstract
Fertilization is a key process in all sexually reproducing species, yet the molecular mechanisms that underlie this event remain unclear. To date, only a few proteins have been shown to be essential for sperm-egg binding and fusion in mice, and only some are conserved across vertebrates. One of these conserved, testis-expressed factors is SPACA6, yet its function has not been investigated outside of mammals. Here we show that zebrafish spaca6 encodes for a sperm membrane protein which is essential for fertilization. Zebrafish spaca6 knockout males are sterile. Furthermore, Spaca6-deficient sperm have normal morphology, are motile, and can approach the egg, but fail to bind to the egg and therefore cannot complete fertilization. Interestingly, sperm lacking Spaca6 have decreased levels of another essential and conserved sperm fertility factor, Dcst2, revealing a previously unknown dependence of Dcst2 expression on Spaca6. Together, our results show that zebrafish Spaca6 regulates Dcst2 levels and is required for binding between the sperm membrane and the oolemma. This is in contrast to murine sperm lacking SPACA6, which was reported to be able to bind but unable to fuse with oocytes. These findings demonstrate that Spaca6 is essential for zebrafish fertilization and is a conserved sperm factor in vertebrate reproduction.
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Affiliation(s)
| | | | | | | | - Victoria E. Deneke
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, Vienna, Austria
| | - Andrea Pauli
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, Vienna, Austria
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10
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Siu KK, Serrão VHB, Ziyyat A, Lee JE. The cell biology of fertilization: Gamete attachment and fusion. J Cell Biol 2021; 220:e202102146. [PMID: 34459848 PMCID: PMC8406655 DOI: 10.1083/jcb.202102146] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 08/13/2021] [Accepted: 08/16/2021] [Indexed: 02/06/2023] Open
Abstract
Fertilization is defined as the union of two gametes. During fertilization, sperm and egg fuse to form a diploid zygote to initiate prenatal development. In mammals, fertilization involves multiple ordered steps, including the acrosome reaction, zona pellucida penetration, sperm-egg attachment, and membrane fusion. Given the success of in vitro fertilization, one would think that the mechanisms of fertilization are understood; however, the precise details for many of the steps in fertilization remain a mystery. Recent studies using genetic knockout mouse models and structural biology are providing valuable insight into the molecular basis of sperm-egg attachment and fusion. Here, we review the cell biology of fertilization, specifically summarizing data from recent structural and functional studies that provide insights into the interactions involved in human gamete attachment and fusion.
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Affiliation(s)
- Karen K. Siu
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Vitor Hugo B. Serrão
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Ahmed Ziyyat
- Université de Paris, Institut Cochin, Institut National de la Santé et de la Recherche Médicale, Centre National de la Recherche Scientifique, Paris, France
- Service d’Histologie, d’Embryologie, Biologie de la Reproduction, Assistance Publique - Hôpitaux de Paris, Hôpital Cochin, Paris, France
| | - Jeffrey E. Lee
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
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11
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Mortazavi B, Allahyari Fard N, Karkhane AA, Shokrpoor S, Heidari F. Evaluation of multi-epitope recombinant protein as a candidate for a contraceptive vaccine. J Reprod Immunol 2021; 145:103325. [PMID: 33930667 DOI: 10.1016/j.jri.2021.103325] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 04/11/2021] [Accepted: 04/13/2021] [Indexed: 10/21/2022]
Abstract
Contraceptive vaccine (CV) is a valuable, non-invasive, and alternative method for purposeful contraception. Sperm antigens are useful targets for producing CVs due to their specialized expression in sperm. In this study, a recombinant protein containing three main sperm epitopes (IZUMO1, SACA3, and PH-20) was designed and evaluated as CV to control fertility in male mice. The chimeric recombinant protein was expressed and purified in E. coli. Male mice were immunized by 100 μg purified protein and sera were collected to assess IgG antibodies. Evaluating the reproductive performance, immunized male mice mated with normal-fertile female mice and mating rate and the number of newborns was studied. Immunized mice were sacrificed and necropsy and histopathology studies were conducted. The results revealed that the designed chimeric protein stimulated the immune system of the mice effectively. The level of IgG antibody was significantly higher in vaccinated mouse rather than control mouse. Eighty percent of the vaccinated mice became infertile and in the remaining ones, the number of children decreased to 4-6 offspring instead of 10-12 in normal mice. Histopathological studies showed that no organs including heart, brain, lung, liver, kidney and intestine were damaged. However, Normal spermatogenesis has been disrupted and necrotic spermatogonia cells were reported in Seminiferous tubules. We concluded that the designed chimeric protein containing IZUMO1, SACA3, and PH-20 epitopes can stimulate the immune system and cause male contraception without any side effects.
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Affiliation(s)
- Behnam Mortazavi
- Department of Animal Biotechnology, Faculty of Agriculture Biotechnology, National Institute of Genetic Engineering and Biotechnology (NIGEB), Tehran, Iran
| | - Najaf Allahyari Fard
- Department of Systems Biotechnology, Faculty of Industrial and Environmental Biotechnology, National Institute of Genetic Engineering and Biotechnology (NIGEB), Tehran, Iran
| | - Ali Asghar Karkhane
- Department of Systems Biotechnology, Faculty of Industrial and Environmental Biotechnology, National Institute of Genetic Engineering and Biotechnology (NIGEB), Tehran, Iran
| | - Sara Shokrpoor
- Department of Pathology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran
| | - Farid Heidari
- Department of Animal Biotechnology, Faculty of Agriculture Biotechnology, National Institute of Genetic Engineering and Biotechnology (NIGEB), Tehran, Iran.
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12
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Abstract
Sexual reproduction is such a successful way of creating progeny with subtle genetic variations that the vast majority of eukaryotic species use it. In mammals, it involves the formation of highly specialised cells: the sperm in males and the egg in females, each carrying the genetic inheritance of an individual. The interaction of sperm and egg culminates with the fusion of their cell membranes, triggering the molecular events that result in the formation of a new genetically distinct organism. Although we have a good cellular description of fertilisation in mammals, many of the molecules involved remain unknown, and especially the identity and role of cell surface proteins that are responsible for sperm–egg recognition, binding, and fusion. Here, we will highlight and discuss these gaps in our knowledge and how the role of some recently discovered sperm cell surface and secreted proteins contribute to our understanding of this fundamental process. Fertilisation is the challenging process whereby cells from two individuals fuse to generate a new, genetically distinct organism of the same species. This Unsolved Mystery article explores the molecular mechanisms underlying sperm–egg interaction and fusion, a fascinating topic that is under increasing investigation.
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Affiliation(s)
- Enrica Bianchi
- Cell Surface Signalling Laboratory, Wellcome Sanger Institute, Cambridge, United Kingdom
- * E-mail:
| | - Gavin J. Wright
- Cell Surface Signalling Laboratory, Wellcome Sanger Institute, Cambridge, United Kingdom
- Department of Biology, Hull York Medical School, York Biomedical Research Institute, University of York, Wentworth Way, York, United Kingdom
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13
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Mei X, Singson AW. The molecular underpinnings of fertility: Genetic approaches in Caenorhabditis elegans. ADVANCED GENETICS (HOBOKEN, N.J.) 2020; 2:e10034. [PMID: 34322672 PMCID: PMC8315475 DOI: 10.1002/ggn2.10034] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The study of mutations that impact fertility has a catch-22. Fertility mutants are often lost since they cannot simply be propagated and maintained. This has hindered progress in understanding the genetics of fertility. In mice, several molecules are found to be required for the interactions between the sperm and egg, with JUNO and IZUMO1 being the only known receptor pair on the egg and sperm surface, respectively. In Caenorhabditis elegans, a total of 12 proteins on the sperm or oocyte have been identified to mediate gamete interactions. Majority of these genes were identified through mutants isolated from genetic screens. In this review, we summarize the several key screening strategies that led to the identification of fertility mutants in C. elegans and provide a perspective about future research using genetic approaches. Recently, advancements in new technologies such as high-throughput sequencing and Crispr-based genome editing tools have accelerated the molecular, cell biological, and mechanistic analysis of fertility genes. We review how these valuable tools advance our understanding of the molecular underpinnings of fertilization. We draw parallels of the molecular mechanisms of fertilization between worms and mammals and argue that our work in C. elegans complements fertility research in humans and other species.
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Affiliation(s)
- Xue Mei
- Department of GeneticsWaksman Institute, Rutgers, The State University of New JerseyPiscatawayNew JerseyUSA
| | - Andrew W. Singson
- Department of GeneticsWaksman Institute, Rutgers, The State University of New JerseyPiscatawayNew JerseyUSA
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Carlisle JA, Swanson WJ. Molecular mechanisms and evolution of fertilization proteins. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2020; 336:652-665. [PMID: 33015976 DOI: 10.1002/jez.b.23004] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 09/04/2020] [Accepted: 09/08/2020] [Indexed: 12/11/2022]
Abstract
Sexual reproduction involves a cascade of molecular interactions between the sperm and the egg culminating in cell-cell fusion. Vital steps mediating fertilization include chemoattraction of the sperm to the egg, induction of the sperm acrosome reaction, dissolution of the egg coat, and sperm-egg plasma membrane binding and fusion. Despite decades of research, only a handful of interacting gamete recognition proteins (GRPs) have been identified across taxa mediating each of these steps, most notably in abalone, sea urchins, and mammals. This review outlines and compares notable GRP pairs mediating sperm-egg recognition in these three significant model systems and discusses the molecular basis of species-specific fertilization driven by GRP function. In addition, we explore the evolutionary theory behind the rapid diversification of GRPs between species. In particular, we focus on how the coevolution between interacting sperm and egg proteins may contribute to the formation of boundaries to hybridization. Finally, we discuss how pairing structural information with evolutionary insights can improve our understanding of mechanisms of fertilization and their origins.
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Affiliation(s)
- Jolie A Carlisle
- Department of Genome Sciences, University of Washington Medical School, Seattle, Washington, USA
| | - Willie J Swanson
- Department of Genome Sciences, University of Washington Medical School, Seattle, Washington, USA
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Spermatozoa lacking Fertilization Influencing Membrane Protein (FIMP) fail to fuse with oocytes in mice. Proc Natl Acad Sci U S A 2020; 117:9393-9400. [PMID: 32295885 PMCID: PMC7196805 DOI: 10.1073/pnas.1917060117] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
As the human body is composed of 60 trillion cells that originate from a fertilized egg, sperm–oocyte fusion is the initial event of our life. Few sperm–oocyte fusion factors have been unveiled to date, and only IZUMO1 has been identified as a sperm-specific fusion-mediating protein. Here, we identified the testis-specific 4930451I11Rik gene important for male fertility, playing a role in sperm–oocyte fusion during fertilization. Based on its functional role, we renamed this gene fertilization influencing membrane protein (Fimp). We discovered a factor responsible for sperm–oocyte fusion in mammals, and this knowledge could be used to develop in vitro and in vivo infertility treatments as well as male contraceptives. Sperm–oocyte fusion is a critical event in mammalian fertilization, categorized by three indispensable proteins. Sperm membrane protein IZUMO1 and its counterpart oocyte membrane protein JUNO make a protein complex allowing sperm to interact with the oocyte, and subsequent sperm–oocyte fusion. Oocyte tetraspanin protein CD9 also contributes to sperm–oocyte fusion. However, the fusion process cannot be explained solely by these three essential factors. In this study, we focused on analyzing a testis-specific gene 4930451I11Rik and generated mutant mice using the CRISPR/Cas9 system. Although IZUMO1 remained in 4930451I11Rik knockout (KO) spermatozoa, the KO spermatozoa were unable to fuse with oocytes and the KO males were severely subfertile. 4930451I11Rik encodes two isoforms: a transmembrane (TM) form and a secreted form. Both CRISPR/Cas9-mediated TM deletion and transgenic (Tg) rescue with the TM form revealed that only the TM form plays a critical role in sperm–oocyte fusion. Thus, we renamed this TM form Fertilization Influencing Membrane Protein (FIMP). The mCherry-tagged FIMP TM form was localized to the sperm equatorial segment where the sperm–oocyte fusion event occurs. Thus, FIMP is a sperm-specific transmembrane protein that is necessary for the sperm–oocyte fusion process.
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Sperm SPACA6 protein is required for mammalian Sperm-Egg Adhesion/Fusion. Sci Rep 2020; 10:5335. [PMID: 32210282 PMCID: PMC7093486 DOI: 10.1038/s41598-020-62091-y] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 03/06/2020] [Indexed: 12/30/2022] Open
Abstract
Three genes are known to be essential for gamete adhesion/fusion (Cd9, Izumo1 and Juno). Here, we confirmed that Spaca6 null males are infertile and showed that their sperm accumulate in the perivitelline space but are unable to fuse with oocyte. Like IZUMO1, SPACA6 which is expressed by human sperm, is remained on the equatorial segment after acrosomal reaction and is involved in human fertilization since an anti-SPACA6 antibody inhibited it. Despite the similarity of the phenotypes caused by Spaca6 and Izumo1 knockouts, these are not redundant and the essential relocation of IZUMO1 is not affected by the lack of SPACA6. We propose a model in which IZUMO1 and SPACA6 would be part of a molecular complex necessary for gamete fusion and that their concomitant presence would be required for the recruitment of another essential molecular actor, such as a fusogen, for the fusion to take place.
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Intracellular protozoan parasites: living probes of the host cell surface molecular repertoire. Curr Opin Microbiol 2019; 52:116-123. [PMID: 31349210 DOI: 10.1016/j.mib.2019.06.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2019] [Revised: 06/16/2019] [Accepted: 06/20/2019] [Indexed: 11/24/2022]
Abstract
Intracellular protozoans co-evolved with their mammalian host cells a range of strategies to cope with the composite and dynamic cell surface features they encounter during migration and infection. Therefore, these single-celled eukaryotic parasites represent a fascinating source of living probes for precisely capturing the dynamic coupling between the membrane and contractile cortex components of the cell surface. Such biomechanical changes drive a constant re-sculpting of the host cell surface, enabling rapid adjustments that contribute to cellular homeostasis. As emphasized in this review, through the design of specific molecular devices and stratagems to interfere with the biomechanics of the mammalian cell surface these parasitic microbes escape from dangerous or unfavourable microenvironments by breaching host cell membranes, directing the membrane repair machinery to wounded membrane areas, or minimizing membrane assault using discretion and speed when invading host cells for sustained residence.
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Alternative splicing of the Izumo1 gene ensures triggering gamete fusion in mice. Sci Rep 2019; 9:3151. [PMID: 30816314 PMCID: PMC6395798 DOI: 10.1038/s41598-019-40130-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Accepted: 02/08/2019] [Indexed: 12/17/2022] Open
Abstract
IZUMO1 is a sperm acrosomal membrane protein that is essential for mammalian fertilization through recognition of JUNO on the oocyte surface and accompanying IZUMO1-JUNO complex formation. Here, we report a new Izumo1 gene splicing variant (IZUMO1_v2) with a unique 52-amino-acid-long signal sequence transcribed from Exon 1b. Although the mRNA amount of Izumo1_v2 is 76 times lower than that of the original Izumo1 (IZUMO1_v1) in the testis, the cell-oocyte assay indicates that IZUMO1_v2-expressing COS-7 cells have the ability to attach to the oocyte equivalent of IZUMO1_v1. To clarify the physiological function of IZUMO1_v2, we produced an IZUMO1_v1-specific knockout mouse line with a nine-base deletion adjacent to the initial methionine codon of IZUMO1_v1 by the CRISPR/Cas9 system. The IZUMO1_v1 knockout male mice carry 0.19-fold lower level of IZUMO1 protein in the spermatozoon; however, reduction in fertility was only minimally affected compared to the wild-type mice, suggesting that only a small fraction of IZUMO1 is sufficient for triggering sperm-egg fusion. We propose that the alternative splicing generating IZUMO1_v2 might function as a fail-safe in mouse for when splicing is disturbed.
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Satouh Y, Ikawa M. New Insights into the Molecular Events of Mammalian Fertilization. Trends Biochem Sci 2018; 43:818-828. [PMID: 30170889 DOI: 10.1016/j.tibs.2018.08.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2018] [Revised: 07/30/2018] [Accepted: 08/04/2018] [Indexed: 12/20/2022]
Abstract
Currently, infertility affects ∼16% of couples worldwide. The causes are reported to involve both male and female factors, including fertilization failure between mature spermatozoa and eggs. However, the molecular mechanisms involved in each step of mammalian fertilization are yet to be fully elucidated. Although some of these steps can be rescued with assisted reproductive technologies, it is important to clarify the molecular mechanisms involved for the treatment and diagnosis of infertile couples. This review illustrates recent findings in mammalian fertilization, discovered by combining gene modification techniques with other new approaches, and aims to show how these findings will guide future research in mammalian fertilization.
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Affiliation(s)
- Yuhkoh Satouh
- Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 5650871, Japan.
| | - Masahito Ikawa
- Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 5650871, Japan; The Institute of Medical Science, The University of Tokyo, Tokyo 1088639, Japan.
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20
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Abstract
All mammalian eggs are surrounded by a highly specialized extracellular matrix (ECM), called the zona pellucida (ZP), that functions before, during, and after fertilization. Unlike somatic cell ECM the mouse ZP is composed of three different proteins, ZP1-3, that are synthesized and secreted by growing oocytes and assembled into long interconnected fibrils. ECM or vitelline envelope (VE) that surrounds fish, reptilian, amphibian, and avian eggs also consists of a limited number of proteins all closely related to ZP1-3. Messenger RNAs encoding ZP1-3 are expressed only by growing oocytes at very high levels from single-copy genes present on different chromosomes. Processing at the amino- and carboxy-termini of nascent ZP1-3 permits secretion of mature proteins into the extracellular space and assembly into fibrils and matrix. Structural features of nascent ZP proteins prevent assembly within secretory vesicles of growing oocytes. Homozygous knockout female mice that fail to synthesize either ZP2 or ZP3 are unable to construct a ZP, ovulate few if any eggs, and are infertile. ZP1-3 have a common structural feature, the ZP domain (ZPD), that has been conserved through 600 million years of evolution and is essential for ZP protein assembly into fibrils. The ZPD consists of two subdomains, each with four conserved cysteine residues present as two intramolecular disulfides, and resembles an immunoglobulin (Ig) domain found in a wide variety of proteins that have diverse functions, from receptors to mechanical transducers. ZP2 and ZP3 function as receptors for acrosome-reacted and acrosome-intact sperm, respectively, during fertilization of ovulated eggs, but are inactivated as sperm receptors as a result of fertilization.
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Affiliation(s)
- Paul M Wassarman
- Department of Cell, Developmental, and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York, NY, United States.
| | - Eveline S Litscher
- Department of Cell, Developmental, and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York, NY, United States
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Abstract
Cell-cell fusion is essential for fertilization and organ development. Dedicated proteins known as fusogens are responsible for mediating membrane fusion. However, until recently, these proteins either remained unidentified or were poorly understood at the mechanistic level. Here, we review how fusogens surmount multiple energy barriers to mediate cell-cell fusion. We describe how early preparatory steps bring membranes to a distance of ∼10 nm, while fusogens act in the final approach between membranes. The mechanical force exerted by cell fusogens and the accompanying lipidic rearrangements constitute the hallmarks of cell-cell fusion. Finally, we discuss the relationship between viral and eukaryotic fusogens, highlight a classification scheme regrouping a superfamily of fusogens called Fusexins, and propose new questions and avenues of enquiry.
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Affiliation(s)
- Javier M Hernández
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, D-44227 Dortmund, Germany
| | - Benjamin Podbilewicz
- Department of Biology, Technion - Israel Institute of Technology, Haifa 32000, Israel
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22
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Guerra AJ, Carruthers VB. Structural Features of Apicomplexan Pore-Forming Proteins and Their Roles in Parasite Cell Traversal and Egress. Toxins (Basel) 2017; 9:toxins9090265. [PMID: 28850082 PMCID: PMC5618198 DOI: 10.3390/toxins9090265] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 08/20/2017] [Accepted: 08/22/2017] [Indexed: 01/18/2023] Open
Abstract
Apicomplexan parasites cause diseases, including malaria and toxoplasmosis, in a range of hosts, including humans. These intracellular parasites utilize pore-forming proteins that disrupt host cell membranes to either traverse host cells while migrating through tissues or egress from the parasite-containing vacuole after replication. This review highlights recent insight gained from the newly available three-dimensional structures of several known or putative apicomplexan pore-forming proteins that contribute to cell traversal or egress. These new structural advances suggest that parasite pore-forming proteins use distinct mechanisms to disrupt host cell membranes at multiple steps in parasite life cycles. How proteolytic processing, secretion, environment, and the accessibility of lipid receptors regulate the membranolytic activities of such proteins is also discussed.
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Affiliation(s)
- Alfredo J Guerra
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI 48109-5620, USA.
| | - Vern B Carruthers
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI 48109-5620, USA.
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Inoue N. Novel insights into the molecular mechanism of sperm-egg fusion via IZUMO1. JOURNAL OF PLANT RESEARCH 2017; 130:475-478. [PMID: 27995377 DOI: 10.1007/s10265-016-0895-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Accepted: 11/24/2016] [Indexed: 06/06/2023]
Abstract
When a spermatozoon fertilizes an oocyte in mammals, there must be an extremely precise regulation system for successful gamete fusion to occur, which is the final step of fertilization. Using gene-modified animals, IZUMO1 on the sperm side and its receptor, JUNO, on the ovum side, have been unveiled as indispensable factors for triggering membrane fusion. We recently analyzed the detailed molecular machinery of the IZUMO1-JUNO recognition system and clarified the tertiary architecture of the IZUMO1-JUNO complex based on the crystal structure. Over the past 2 years, important discoveries have successively emerged, presenting a new perspective on fertilization. In this mini-review, I will initially explain the historical background of the molecular mechanism study of gamete fusion, and go on to describe our latest study data.
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Affiliation(s)
- Naokazu Inoue
- Department of Cell Science, School of Medicine, Institutes for Biomedical Sciences, Fukushima Medical University, Hikarigaoka 1, Fukushima-City, Fukushima, 960-1295, Japan.
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Abstract
Male infertility has become a very serious problem in the human reproduction system, but the molecular mechanism of infertility remains largely unknown.
Fertilization is the phenomenon in which a sperm and oocyte find each other, interact, and fuse. Sperm-oocyte fusion-related factors on the sperm side play
crucial roles in male infertility. For example, IZUMO1 is well-known as a sperm protein essential for fusion of a sperm and oocyte, but its dysfunction or
mutation can result in male infertility. Recent studies showed a novel sperm protein named Bactericidal/permeability-increasing protein (BPI), which takes part
in the sperm-oocyte fusion process. The complexity and expected redundancy of the factors involved makes the process intricate, with a still poorly understood
mechanism, which is difficult to comprehend in full detail. This review summarizes the known molecules involved in the process of sperm-oocyte fusion, mainly
focusing on the relevant factors on the sperm side, whose dysregulation may potentially be associated with male infertility. New insights may come from these
molecules in this review, can facilitate the development of new treatments of male infertility, and may have a diagnostic value in infertility.
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Affiliation(s)
- Lisha Mou
- Shenzhen Xenotransplantation Medical Engineering Research and Development Center, Institute of Translational Medicine, Shenzhen Second People's Hospital, First Affiliated Hospital of Shenzhen University, Shenzhen, China
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Abstract
Fertilization is the culminating event of sexual reproduction, which involves the union of the sperm and egg to form a single, genetically distinct organism. Despite the fundamental role of fertilization, the basic mechanisms involved have remained poorly understood. However, these mechanisms must involve an ordered schedule of cellular recognition events between the sperm and egg to ensure successful fusion. In this article, we review recent progress in our molecular understanding of mammalian fertilization, highlighting the areas in which genetic approaches have been particularly informative and focusing especially on the roles of secreted and cell surface proteins, expressed in a sex-specific manner, that mediate sperm-egg interactions. We discuss how the sperm interacts with the female reproductive tract, zona pellucida, and the oolemma. Finally, we review recent progress made in elucidating the mechanisms that reduce polyspermy and ensure that eggs normally fuse with only a single sperm.
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Affiliation(s)
- Enrica Bianchi
- Cell Surface Signalling Laboratory, Wellcome Trust Sanger Institute, Cambridge CB10 1SA, United Kingdom; ,
| | - Gavin J Wright
- Cell Surface Signalling Laboratory, Wellcome Trust Sanger Institute, Cambridge CB10 1SA, United Kingdom; ,
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