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Membrane Fusion 2.0

A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Biochemistry".

Deadline for manuscript submissions: closed (31 December 2020) | Viewed by 20398

Special Issue Editor


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Guest Editor
Department of Biochemistry, Iowa State University, Ames, IA, USA
Interests: mechanism of fast synaptic vesicle fusion; spin labeling electron paramagnetic resonance (EPR); single molecule fluorescence
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Membrane fusion is imperative for a wide variety of important biological events such as fertilization, viral infection to host cells, neurotransmitter release, muscle fiber formation, and trafficking in cells. Membrane fusion is a rather simple physics problem in that two separate bilayers merge to form a continuous single bilayer. However, there is wide variation in the sequence and the structure of proteins mediating specific membrane fusion. Extensive structural investigations have now revealed some structural regularities shared by many of these proteins. Moreover, some principles underlying protein conformational changes, necessary to provide the free energy for membrane fusion, have been uncovered. Meanwhile, although it is established that for virus–cell membrane fusion, it transits through hemifusion—a state in which two bilayers are half-fused—there is still controversy as to whether hemifusion is an on-pathway intermediate or not in synaptic vesicle fusion. Furthermore, the functional role that the transmembrane domains of the fusion protein play remains to be fully understood. Yet, the emergence of revolutionary biophysical tools such as single molecule fluorescence and cryo-electron microscopy has opened up tremendous possibilities of visualizing the major intermediates and characterizing the transitions along the fusion pathway. Importantly, these methods are not limited to the in vitro environments but can be applied directly to the membrane fusion event as it happens in cells. Thus, the time is right to publish a dedicated Special Issue that will include comprehensive reviews, provocative ideas, and insightful new results, which will collectively define the roadmap for the research in membrane fusion. We cordially invite the submission of review or original research papers for the Special Issue.

Prof. Dr. Yeon-Kyun Shin
Guest Editor

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Keywords

  • Hemagglutinin
  • HIV gp41
  • SNARE
  • Bilayer
  • Hemifusion
  • Fusion pore
  • Membrane remodeling
  • Coiled coil

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Published Papers (5 papers)

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Research

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22 pages, 5213 KiB  
Article
Ectodomain Pulling Combines with Fusion Peptide Inserting to Provide Cooperative Fusion for Influenza Virus and HIV
by Sergey A. Akimov, Oleg V. Kondrashov, Joshua Zimmerberg and Oleg V. Batishchev
Int. J. Mol. Sci. 2020, 21(15), 5411; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21155411 - 29 Jul 2020
Cited by 6 | Viewed by 2063
Abstract
Enveloped viruses include the most dangerous human and animal pathogens, in particular coronavirus, influenza virus, and human immunodeficiency virus (HIV). For these viruses, receptor binding and entry are accomplished by a single viral envelope protein (termed the fusion protein), the structural changes of [...] Read more.
Enveloped viruses include the most dangerous human and animal pathogens, in particular coronavirus, influenza virus, and human immunodeficiency virus (HIV). For these viruses, receptor binding and entry are accomplished by a single viral envelope protein (termed the fusion protein), the structural changes of which trigger the remodeling and merger of the viral and target cellular membranes. The number of fusion proteins required for fusion activity is still under debate, and several studies report this value to range from 1 to 9 for type I fusion proteins. Here, we consider the earliest stage of viral fusion based on the continuum theory of membrane elasticity. We demonstrate that membrane deformations induced by the oblique insertion of amphipathic fusion peptides mediate the lateral interaction of these peptides and drive them to form into a symmetric fusion rosette. The pulling force produced by the structural rearrangements of the fusion protein ectodomains gives additional torque, which deforms the membrane and additionally stabilizes the symmetric fusion rosette, thus allowing a reduction in the number of fusion peptides needed for fusion. These findings can resolve the large range of published cooperativity indices for HIV, influenza, and other type I fusion proteins. Full article
(This article belongs to the Special Issue Membrane Fusion 2.0)
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17 pages, 1937 KiB  
Article
Proton Leakage Is Sensed by IM30 and Activates IM30-Triggered Membrane Fusion
by Carmen Siebenaller, Benedikt Junglas, Annika Lehmann, Nadja Hellmann and Dirk Schneider
Int. J. Mol. Sci. 2020, 21(12), 4530; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21124530 - 25 Jun 2020
Cited by 7 | Viewed by 2895
Abstract
The inner membrane-associated protein of 30 kDa (IM30) is crucial for the development and maintenance of the thylakoid membrane system in chloroplasts and cyanobacteria. While its exact physiological function still is under debate, it has recently been suggested that IM30 has (at least) [...] Read more.
The inner membrane-associated protein of 30 kDa (IM30) is crucial for the development and maintenance of the thylakoid membrane system in chloroplasts and cyanobacteria. While its exact physiological function still is under debate, it has recently been suggested that IM30 has (at least) a dual function, and the protein is involved in stabilization of the thylakoid membrane as well as in Mg2+-dependent membrane fusion. IM30 binds to negatively charged membrane lipids, preferentially at stressed membrane regions where protons potentially leak out from the thylakoid lumen into the chloroplast stroma or the cyanobacterial cytoplasm, respectively. Here we show in vitro that IM30 membrane binding, as well as membrane fusion, is strongly increased in acidic environments. This enhanced activity involves a rearrangement of the protein structure. We suggest that this acid-induced transition is part of a mechanism that allows IM30 to (i) sense sites of proton leakage at the thylakoid membrane, to (ii) preferentially bind there, and to (iii) seal leaky membrane regions via membrane fusion processes. Full article
(This article belongs to the Special Issue Membrane Fusion 2.0)
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18 pages, 3621 KiB  
Article
Complex Size and Surface Charge Determine Nucleic Acid Transfer by Fusogenic Liposomes
by Marco Hoffmann, Nils Hersch, Sven Gerlach, Georg Dreissen, Ronald Springer, Rudolf Merkel, Agnes Csiszár and Bernd Hoffmann
Int. J. Mol. Sci. 2020, 21(6), 2244; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21062244 - 24 Mar 2020
Cited by 19 | Viewed by 4125
Abstract
Highly efficient, biocompatible, and fast nucleic acid delivery methods are essential for biomedical applications and research. At present, two main strategies are used to this end. In non-viral transfection liposome- or polymer-based formulations are used to transfer cargo into cells via endocytosis, whereas [...] Read more.
Highly efficient, biocompatible, and fast nucleic acid delivery methods are essential for biomedical applications and research. At present, two main strategies are used to this end. In non-viral transfection liposome- or polymer-based formulations are used to transfer cargo into cells via endocytosis, whereas viral carriers enable direct nucleic acid delivery into the cell cytoplasm. Here, we introduce a new generation of liposomes for nucleic acid delivery, which immediately fuse with the cellular plasma membrane upon contact to transfer the functional nucleic acid directly into the cell cytoplasm. For maximum fusion efficiency combined with high cargo transfer, nucleic acids had to be complexed and partially neutralized before incorporation into fusogenic liposomes. Among the various neutralization agents tested, small, linear, and positively charged polymers yielded the best complex properties. Systematic variation of liposomal composition and nucleic acid complexation identified surface charge as well as particle size as essential parameters for cargo-liposome interaction and subsequent fusion induction. Optimized protocols were tested for the efficient transfer of different kinds of nucleic acids like plasmid DNA, messenger RNA, and short-interfering RNA into various mammalian cells in culture and into primary tissues. Full article
(This article belongs to the Special Issue Membrane Fusion 2.0)
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Review

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36 pages, 4061 KiB  
Review
Continuum Models of Membrane Fusion: Evolution of the Theory
by Sergey A. Akimov, Rodion J. Molotkovsky, Peter I. Kuzmin, Timur R. Galimzyanov and Oleg V. Batishchev
Int. J. Mol. Sci. 2020, 21(11), 3875; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21113875 - 29 May 2020
Cited by 31 | Viewed by 4042
Abstract
Starting from fertilization, through tissue growth, hormone secretion, synaptic transmission, and sometimes morbid events of carcinogenesis and viral infections, membrane fusion regulates the whole life of high organisms. Despite that, a lot of fusion processes still lack well-established models and even a list [...] Read more.
Starting from fertilization, through tissue growth, hormone secretion, synaptic transmission, and sometimes morbid events of carcinogenesis and viral infections, membrane fusion regulates the whole life of high organisms. Despite that, a lot of fusion processes still lack well-established models and even a list of main actors. A merger of membranes requires their topological rearrangements controlled by elastic properties of a lipid bilayer. That is why continuum models based on theories of membrane elasticity are actively applied for the construction of physical models of membrane fusion. Started from the view on the membrane as a structureless film with postulated geometry of fusion intermediates, they developed along with experimental and computational techniques to a powerful tool for prediction of the whole process with molecular accuracy. In the present review, focusing on fusion processes occurring in eukaryotic cells, we scrutinize the history of these models, their evolution and complication, as well as open questions and remaining theoretical problems. We show that modern approaches in this field allow continuum models of membrane fusion to stand shoulder to shoulder with molecular dynamics simulations, and provide the deepest understanding of this process in multiple biological systems. Full article
(This article belongs to the Special Issue Membrane Fusion 2.0)
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17 pages, 1166 KiB  
Review
Broad-Spectrum Coronavirus Fusion Inhibitors to Combat COVID-19 and Other Emerging Coronavirus Diseases
by Xinling Wang, Shuai Xia, Qian Wang, Wei Xu, Weihua Li, Lu Lu and Shibo Jiang
Int. J. Mol. Sci. 2020, 21(11), 3843; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21113843 - 28 May 2020
Cited by 31 | Viewed by 6821
Abstract
In the past 17 years, three novel coronaviruses have caused severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and the coronavirus disease 2019 (COVID-19). As emerging infectious diseases, they were characterized by their novel pathogens and transmissibility without available clinical drugs [...] Read more.
In the past 17 years, three novel coronaviruses have caused severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and the coronavirus disease 2019 (COVID-19). As emerging infectious diseases, they were characterized by their novel pathogens and transmissibility without available clinical drugs or vaccines. This is especially true for the newly identified COVID-19 caused by SARS coronavirus 2 (SARS-CoV-2) for which, to date, no specific antiviral drugs or vaccines have been approved. Similar to SARS and MERS, the lag time in the development of therapeutics is likely to take months to years. These facts call for the development of broad-spectrum anti-coronavirus drugs targeting a conserved target site. This review will systematically describe potential broad-spectrum coronavirus fusion inhibitors, including antibodies, protease inhibitors, and peptide fusion inhibitors, along with a discussion of their advantages and disadvantages. Full article
(This article belongs to the Special Issue Membrane Fusion 2.0)
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