1
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Giudice J, Brauer DD, Zoltek M, Vázquez Maldonado AL, Kelly M, Schepartz A. Requirements for efficient endosomal escape by designed mini-proteins. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.05.588336. [PMID: 38617268 PMCID: PMC11014610 DOI: 10.1101/2024.04.05.588336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/16/2024]
Abstract
ZF5.3 is a compact, rationally designed mini-protein that escapes efficiently from the endosomes of multiple cell types. Despite its small size (27 amino acids), ZF5.3 can be isolated intact from the cytosol of treated cells and guides multiple classes of proteins into the cytosol and/or nucleus. In the best cases, delivery efficiencies reach or exceed 50% to establish nuclear or cytosolic concentrations of 500 nM or higher. But other than the requirement for unfoldable cargo and an intact HOPS complex, there is little known about how ZF5.3 traverses the limiting endocytic membrane. Here we delineate the attributes of ZF5.3 that enable efficient endosomal escape. We confirm that ZF5.3 is stable at pH values between 5.5 and 7.5, with no evidence of unfolding even at temperatures as high as 95 °C. The high-resolution NMR structure of ZF5.3 at pH 5.5, also reported here, shows a canonical p zinc-finger fold with the penta-arg motif integrated seamlessly into the C-terminal α-helix. At lower pH, ZF5.3 unfolds cooperatively as judged by both circular dichroism and high-resolution NMR. Unfolding occurs upon protonation of a single Zn(II)-binding His side chain whose pKa corresponds almost exactly to that of the late endosomal lumen. pH-induced unfolding is essential for endosomal escape, as a ZF5.3 analog that remains folded at pH 4.5 fails to efficiently reach the cytosol, despite high overall uptake. Finally, using reconstituted liposomes, we identify a high-affinity interaction of ZF5.3 with a specific lipid-BMP-that is selectively enriched in the inner leaflet of late endosomal membranes. This interaction is 10-fold stronger at low pH than neutral pH, providing a molecular picture for why escape occurs preferentially and in a HOPS-dependent manner from late endosomal compartments. The requirements for programmed endosomal escape identified here should aid and inform the design of proteins, peptidomimetics, and other macromolecules that reach cytosolic or nuclear targets intact and at therapeutically relevant concentrations.
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Affiliation(s)
- Jonathan Giudice
- Department of Chemistry, University of California, Berkeley, CA 94720
| | - Daniel D. Brauer
- Department of Chemistry, University of California, Berkeley, CA 94720
| | - Madeline Zoltek
- Department of Molecular and Cellular Biology, University of California, Berkeley, CA 94720
| | | | - Mark Kelly
- School of Pharmacy, University of California-San Francisco, San Francisco, CA 94158
| | - Alanna Schepartz
- Department of Chemistry, University of California, Berkeley, CA 94720
- Department of Molecular and Cellular Biology, University of California, Berkeley, CA 94720
- California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720
- Chan Zuckerberg Biohub, San Francisco, CA 94158
- Arc Institute, Palo Alto, CA
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2
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Birtles D, Abbas W, Lee J. Bis(Monoacylglycero)Phosphate Promotes Membrane Fusion Facilitated by the SARS-CoV-2 Fusion Domain. J Phys Chem B 2024; 128:2675-2683. [PMID: 38466655 DOI: 10.1021/acs.jpcb.3c07863] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/13/2024]
Abstract
Membrane fusion is a critical component of the viral lifecycle. For SARS-CoV-2, fusion is facilitated by the spike glycoprotein and can take place via either the plasma membrane or the endocytic pathway. The fusion domain (FD), which is found within the spike glycoprotein, is primarily responsible for the initiation of fusion as it embeds itself within the target cell's membrane. A preference for SARS-CoV-2 to fuse at low pH akin to the environment of the endocytic pathway has already been established; however, the impact of the target cell's lipid composition on the FD has yet to be explored. Here, we have shown that the SARS-CoV-2 FD preferentially initiates fusion at the late endosomal membrane over the plasma membrane, on the basis of lipid composition alone. A positive, fusogenic relationship with anionic lipids from the plasma membrane (POPS: 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-l-serine) and endosomal membrane (BMP: bis(monoacylglycero)phosphate) was established, with a large preference demonstrated for the latter. When comparing the binding affinity and secondary structure of the FD in the presence of different anionic lipids, little deviation was evident while the charge was maintained. However, it was discovered that BMP had a subtle, negative impact on lipid packing in comparison to that of POPS. Furthermore, an inverse relationship between lipid packing and the fusogenecity of the SARS-CoV-2 FD was witnessed. In conclusion, the SARS-CoV-2 FD preferentially initiates fusion at a membrane resembling that of the late endosomal compartment, predominately due to the presence of BMP and its impact on lipid packing.
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Affiliation(s)
- Daniel Birtles
- Department of Chemistry and Biochemistry, University of Maryland, College Park 20742, Maryland, United States
| | - Wafa Abbas
- Department of Chemistry and Biochemistry, University of Maryland, College Park 20742, Maryland, United States
| | - Jinwoo Lee
- Department of Chemistry and Biochemistry, University of Maryland, College Park 20742, Maryland, United States
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3
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Ramirez JM, Calderon-Zavala AC, Balaram A, Heldwein EE. In vitro reconstitution of herpes simplex virus 1 fusion identifies low pH as a fusion co-trigger. mBio 2023; 14:e0208723. [PMID: 37874146 PMCID: PMC10746285 DOI: 10.1128/mbio.02087-23] [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: 09/05/2023] [Accepted: 09/11/2023] [Indexed: 10/25/2023] Open
Abstract
IMPORTANCE HSV-1 causes lifelong, incurable infections and diseases ranging from mucocutaneous lesions to fatal encephalitis. Fusion of viral and host membranes is a critical step in HSV-1 infection of target cells that requires multiple factors on both the viral and host sides. Due to this complexity, many fundamental questions remain unanswered, such as the identity of the viral and host factors that are necessary and sufficient for HSV-1-mediated membrane fusion and the nature of the fusion trigger. Here, we developed a simplified in vitro fusion assay to examine the fusion requirements and identified low pH as a co-trigger for virus-mediated fusion in vitro. We hypothesize that low pH has a critical role in cell entry and, potentially, pathogenesis.
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Affiliation(s)
- J. Martin Ramirez
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
- Graduate Program in Molecular Microbiology, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USA
- Medical Scientist Training Program, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Ariana C. Calderon-Zavala
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
- Graduate Program in Molecular Microbiology, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Ariane Balaram
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
- Graduate Program in Molecular Microbiology, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Ekaterina E. Heldwein
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
- Graduate Program in Molecular Microbiology, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USA
- Medical Scientist Training Program, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USA
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4
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Barrado-Gil L, García-Dorival I, Galindo I, Alonso C, Cuesta-Geijo MÁ. Insights into the function of ESCRT complex and LBPA in ASFV infection. Front Cell Infect Microbiol 2023; 13:1163569. [PMID: 38125905 PMCID: PMC10731053 DOI: 10.3389/fcimb.2023.1163569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 11/13/2023] [Indexed: 12/23/2023] Open
Abstract
The African swine fever virus (ASFV) is strongly dependent on an intact endocytic pathway and a certain cellular membrane remodeling for infection, possibly regulated by the endosomal sorting complexes required for transport (ESCRT). The ESCRT machinery is mainly involved in the coordination of membrane dynamics; hence, several viruses exploit this complex and its accessory proteins VPS4 and ALIX for their own benefit. In this work, we found that shRNA-mediated knockdown of VPS4A decreased ASFV replication and viral titers, and this silencing resulted in an enhanced expression of ESCRT-0 component HRS. ASFV infection slightly increased HRS expression but not under VPS4A depletion conditions. Interestingly, VPS4A silencing did not have an impact on ALIX expression, which was significantly overexpressed upon ASFV infection. Further analysis revealed that ALIX silencing impaired ASFV infection at late stages of the viral cycle, including replication and viral production. In addition to ESCRT, the accessory protein ALIX is involved in endosomal membrane dynamics in a lysobisphosphatydic acid (LBPA) and Ca2+-dependent manner, which is relevant for intraluminal vesicle (ILV) biogenesis and endosomal homeostasis. Moreover, LBPA interacts with NPC2 and/or ALIX to regulate cellular cholesterol traffic, and would affect ASFV infection. Thus, we show that LBPA blocking impacted ASFV infection at both early and late infection, suggesting a function for this unconventional phospholipid in the ASFV viral cycle. Here, we found for the first time that silencing of VPS4A and ALIX affects the infection later on, and blocking LBPA function reduces ASFV infectivity at early and later stages of the viral cycle, while ALIX was overexpressed upon infection. These data suggested the relevance of ESCRT-related proteins in ASFV infection.
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Affiliation(s)
| | | | | | | | - Miguel Ángel Cuesta-Geijo
- Departmento Biotecnología, INIA-CSIC, Centro Nacional Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, Madrid, Spain
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5
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Chen J, Cazenave-Gassiot A, Xu Y, Piroli P, Hwang R, DeFreitas L, Chan RB, Di Paolo G, Nandakumar R, Wenk MR, Marquer C. Lysosomal phospholipase A2 contributes to the biosynthesis of the atypical late endosome lipid bis(monoacylglycero)phosphate. Commun Biol 2023; 6:210. [PMID: 36823305 PMCID: PMC9950130 DOI: 10.1038/s42003-023-04573-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Accepted: 02/09/2023] [Indexed: 02/25/2023] Open
Abstract
The late endosome/lysosome (LE/Lys) lipid bis(monoacylglycero)phosphate (BMP) plays major roles in cargo sorting and degradation, regulation of cholesterol and intercellular communication and has been linked to viral infection and neurodegeneration. Although BMP was initially described over fifty years ago, the enzymes regulating its synthesis remain unknown. The first step in the BMP biosynthetic pathway is the conversion of phosphatidylglycerol (PG) into lysophosphatidylglycerol (LPG) by a phospholipase A2 (PLA2) enzyme. Here we report that this enzyme is lysosomal PLA2 (LPLA2). We show that LPLA2 is sufficient to convert PG into LPG in vitro. We show that modulating LPLA2 levels regulates BMP levels in HeLa cells, and affects downstream pathways such as LE/Lys morphology and cholesterol levels. Finally, we show that in a model of Niemann-Pick disease type C, overexpressing LPLA2 alleviates the LE/Lys cholesterol accumulation phenotype. Altogether, we shed new light on BMP biosynthesis and contribute tools to regulate BMP-dependent pathways.
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Affiliation(s)
- Jacinda Chen
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University Irving Medical Center, New York City, NY, 10032, USA
| | - Amaury Cazenave-Gassiot
- Department of Biochemistry and Precision Medicine Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117597, Singapore
- Singapore Lipidomics Incubator, Life Sciences Institute, National University of Singapore, Singapore, 117456, Singapore
| | - Yimeng Xu
- Biomarkers Core Laboratory, Irving Institute for Clinical and Translational Research, Columbia University Irving Medical Center, New York City, NY, 10032, USA
| | - Paola Piroli
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University Irving Medical Center, New York City, NY, 10032, USA
| | - Robert Hwang
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University Irving Medical Center, New York City, NY, 10032, USA
| | - Laura DeFreitas
- Biomarkers Core Laboratory, Irving Institute for Clinical and Translational Research, Columbia University Irving Medical Center, New York City, NY, 10032, USA
| | - Robin Barry Chan
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York City, NY, 10032, USA
- AliveX Biotech, Shanghai, China
| | - Gilbert Di Paolo
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University Irving Medical Center, New York City, NY, 10032, USA
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York City, NY, 10032, USA
- Denali Therapeutics Inc., South San Francisco, CA, USA
| | - Renu Nandakumar
- Biomarkers Core Laboratory, Irving Institute for Clinical and Translational Research, Columbia University Irving Medical Center, New York City, NY, 10032, USA
| | - Markus R Wenk
- Department of Biochemistry and Precision Medicine Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117597, Singapore
- Singapore Lipidomics Incubator, Life Sciences Institute, National University of Singapore, Singapore, 117456, Singapore
| | - Catherine Marquer
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University Irving Medical Center, New York City, NY, 10032, USA.
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York City, NY, 10032, USA.
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6
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Mannsverk S, Villamil Giraldo AM, Kasson PM. Influenza Virus Membrane Fusion Is Promoted by the Endosome-Resident Phospholipid Bis(monoacylglycero)phosphate. J Phys Chem B 2022; 126:10445-10451. [PMID: 36468619 PMCID: PMC9761668 DOI: 10.1021/acs.jpcb.2c06642] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The phospholipid bis(monoacylglycero)phosphate (BMP) is enriched in late endosomal and endolysosomal membranes and is believed to be involved in membrane deformation and generation of intralumenal vesicles within late endosomes. Previous studies have demonstrated that BMP promotes membrane fusion of several enveloped viruses, but a limited effect has been found on influenza virus. Here, we report the use of single-virus fusion assays to dissect BMP's effect on influenza virus fusion in greater depth. In agreement with prior reports, we found that hemifusion kinetics and efficiency were unaffected by the addition of 10-20 mol % BMP to the target membrane. However, using an assay for fusion pore formation and genome exposure, we found full fusion efficiency to be substantially enhanced by the addition of 10-20 mol % BMP to the target membrane, while the kinetics remained unaffected. By comparing BMP to other negatively charged phospholipids, we found the effect on fusion efficiency mainly attributable to headgroup charge, although we also hypothesize a role for BMP's unusual chemical structure. Our results suggest that BMP function as a permissive factor for a wider range of viruses than previously reported. We hypothesize that BMP may be a general cofactor for endosomal entry of enveloped viruses.
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Affiliation(s)
- Steinar Mannsverk
- Science
for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala 75124, Sweden
| | - Ana M. Villamil Giraldo
- Science
for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala 75124, Sweden
| | - Peter M. Kasson
- Science
for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala 75124, Sweden,Departments
of Molecular Physiology and Biomedical Engineering, University of Virginia, Charlottesville, Virginia 22908, United States,
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7
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Birtles D, Oh AE, Lee J. Exploring the
pH
dependence of the
SARS‐CoV
‐2 complete fusion domain and the role of its unique structural features. Protein Sci 2022. [PMCID: PMC9538437 DOI: 10.1002/pro.4390] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
SARS‐CoV‐2 may enter target cells through the process of membrane fusion at either the plasma (~pH 7.4–7.0) or endosomal (~pH 6.5–5.0) membrane in order to deliver its genetic information. The fusion domain (FD) of the spike glycoprotein is responsible for initiating fusion and is thus integral to the viral life cycle. The FD of SARS‐CoV‐2 is unique in that it consists of two structurally distinctive regions referred to as the fusion peptide (FP) and the fusion loop (FL); yet the molecular mechanisms behind how this FD perturbs the membrane to initiate fusion remains unclear. In this study via solution NMR, we witnessed only a slight conformational change in the FD between pH 7.4 and pH 5.0, resulting in a minor elongation of helix 1. However, we found that the FD's ability to mediate membrane fusion has a large and significant pH dependence, with fusion events being more readily induced at low pH. Interestingly, a biphasic relationship between the environmental pH and fusogenicity was discovered, suggesting a preference for the FD to initiate fusion at the late endosomal membrane. Furthermore, the conserved disulfide bond and hydrophobic motif “LLF” were found to be critical for the function of the complete FD, with minimal activity witnessed when either was perturbed. In conclusion, these findings indicate that the SARS‐CoV‐2 FD preferably initiates fusion at a pH similar to the late endosome through a mechanism that heavily relies on the internal disulfide bond of the FL and hydrophobic LLF motif within the FP.
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Affiliation(s)
- Daniel Birtles
- Department of Chemistry and Biochemistry University of Maryland College Park Maryland USA
| | - Anna E. Oh
- Department of Chemistry and Biochemistry University of Maryland College Park Maryland USA
| | - Jinwoo Lee
- Department of Chemistry and Biochemistry University of Maryland College Park Maryland USA
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8
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Omasta B, Tomaskova J. Cellular Lipids-Hijacked Victims of Viruses. Viruses 2022; 14:1896. [PMID: 36146703 PMCID: PMC9501026 DOI: 10.3390/v14091896] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 08/24/2022] [Accepted: 08/25/2022] [Indexed: 11/29/2022] Open
Abstract
Over the millions of years-long co-evolution with their hosts, viruses have evolved plenty of mechanisms through which they are able to escape cellular anti-viral defenses and utilize cellular pathways and organelles for replication and production of infectious virions. In recent years, it has become clear that lipids play an important role during viral replication. Viruses use cellular lipids in a variety of ways throughout their life cycle. They not only physically interact with cellular membranes but also alter cellular lipid metabolic pathways and lipid composition to create an optimal replication environment. This review focuses on examples of how different viruses exploit cellular lipids in different cellular compartments during their life cycles.
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Affiliation(s)
| | - Jana Tomaskova
- Biomedical Research Center, Institute of Virology, Slovak Academy of Sciences, Dúbravská cesta 9, 845 05 Bratislava, Slovakia
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9
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Cabot M, Kiessling V, White JM, Tamm LK. Endosomes supporting fusion mediated by vesicular stomatitis virus glycoprotein have distinctive motion and acidification. Traffic 2022; 23:221-234. [PMID: 35147273 PMCID: PMC10621750 DOI: 10.1111/tra.12836] [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: 11/05/2021] [Revised: 02/03/2022] [Accepted: 02/07/2022] [Indexed: 11/28/2022]
Abstract
Most enveloped viruses infect cells by binding receptors at the cell surface and undergo trafficking through the endocytic pathway to a compartment with the requisite conditions to trigger fusion with a host endosomal membrane. Broad categories of compartments in the endocytic pathway include early and late endosomes, which can be further categorized into subpopulations with differing rates of maturation and motility characteristics. Endocytic compartments have varying protein and lipid components, luminal ionic conditions and pH that provide uniquely hospitable environments for specific viruses to fuse. In order to characterize compartments that permit fusion, we studied the trafficking and fusion of viral particles pseudotyped with the vesicular stomatitis virus glycoprotein (VSV-G) on their surface and equipped with a novel pH sensor and a fluorescent content marker to measure pH, motion and fusion at the single particle level in live cells. We found that the VSV-G particles fuse predominantly from more acidic and more motile endosomes, and that a significant fraction of particles is trafficked to more static and less acidic endosomes that do not support their fusion. Moreover, the fusion-supporting endosomes undergo directed motion.
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Affiliation(s)
- Maya Cabot
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22903, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22903, USA
| | - Volker Kiessling
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22903, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22903, USA
| | - Judith M. White
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22903, USA
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22903, USA
| | - Lukas K. Tamm
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22903, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22903, USA
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22903, USA
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10
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Birtles D, Lee J. Identifying Distinct Structural Features of the SARS-CoV-2 Spike Protein Fusion Domain Essential for Membrane Interaction. Biochemistry 2021; 60:2978-2986. [PMID: 34570469 PMCID: PMC8491435 DOI: 10.1021/acs.biochem.1c00543] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 09/20/2021] [Indexed: 12/23/2022]
Abstract
The SARS-CoV-2 spike protein is the primary antigenic determinant of the virus and has been studied extensively, yet the process of membrane fusion remains poorly understood. The fusion domain (FD) of viral glycoproteins is well established as facilitating the initiation of membrane fusion. An improved understanding of the structural plasticity associated with these highly conserved regions aids in our knowledge of the molecular mechanisms that drive viral fusion. Within the spike protein, the FD of SARS-CoV-2 exists immediately following S2' cleavage at the N-terminus of the S2 domain. Here we have shown that following the introduction of a membrane at pH 7.4, the FD undergoes a transition from a random coil to a more structurally well-defined postfusion state. Furthermore, we have classified the domain into two distinct regions, a fusion peptide (FP, S816-G838) and a fusion loop (FL, D839-F855). The FP forms a helix-turn-helix motif upon association with a membrane, and the favorable entropy gained during this transition from a random coil is likely the driving force behind membrane insertion. Membrane depth experiments then revealed the FP is found inserted within the membrane below the lipid headgroups, while the interaction of the FL with the membrane is shallower in nature. Thus, we propose a structural model relevant to fusion at the plasma membrane in which the FP inserts itself just below the phospholipid headgroups and the FL lays upon the lipid membrane surface.
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Affiliation(s)
- Daniel Birtles
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, United States
| | - Jinwoo Lee
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, United States
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11
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The late endosome-resident lipid bis(monoacylglycero)phosphate is a cofactor for Lassa virus fusion. PLoS Pathog 2021; 17:e1009488. [PMID: 34492091 PMCID: PMC8448326 DOI: 10.1371/journal.ppat.1009488] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 09/17/2021] [Accepted: 08/25/2021] [Indexed: 11/20/2022] Open
Abstract
Arenavirus entry into host cells occurs through a low pH-dependent fusion with late endosomes that is mediated by the viral glycoprotein complex (GPC). The mechanisms of GPC-mediated membrane fusion and of virus targeting to late endosomes are not well understood. To gain insights into arenavirus fusion, we examined cell-cell fusion induced by the Old World Lassa virus (LASV) GPC complex. LASV GPC-mediated cell fusion is more efficient and occurs at higher pH with target cells expressing human LAMP1 compared to cells lacking this cognate receptor. However, human LAMP1 is not absolutely required for cell-cell fusion or LASV entry. We found that GPC-induced fusion progresses through the same lipid intermediates as fusion mediated by other viral glycoproteins–a lipid curvature-sensitive intermediate upstream of hemifusion and a hemifusion intermediate downstream of acid-dependent steps that can be arrested in the cold. Importantly, GPC-mediated fusion and LASV pseudovirus entry are specifically augmented by an anionic lipid, bis(monoacylglycero)phosphate (BMP), which is highly enriched in late endosomes. This lipid also specifically promotes cell fusion mediated by Junin virus GPC, an unrelated New World arenavirus. We show that BMP promotes late steps of LASV fusion downstream of hemifusion–the formation and enlargement of fusion pores. The BMP-dependence of post-hemifusion stages of arenavirus fusion suggests that these viruses evolved to use this lipid as a cofactor to selectively fuse with late endosomes. Pathogenic arenaviruses pose a serious health threat. The viral envelope glycoprotein GPC mediates attachment to host cells and drives virus entry via endocytosis and low pH-dependent fusion within late endosomes. Understanding the host factors and processes that are essential for arenavirus fusion may identify novel therapeutic targets. To delineate the mechanism of arenavirus entry, we examined cell-cell fusion induced by the Old World Lassa virus GPC proteins at low pH. Lassa GPC-mediated fusion was augmented by the human LAMP1 receptor and progressed through lipid curvature-sensitive intermediates, such as hemifusion (merger of contacting leaflets of viral and cell membrane without the formation of a fusion pore). We found that most GPC-mediated fusion events were off-path hemifusion structures and that the transition from hemifusion to full fusion and fusion pore enlargement were specifically promoted by an anionic lipid, bis(monoacylglycero)phosphate, which is highly enriched in late endosomes. This lipid also specifically promotes fusion of unrelated New World Junin arenavirus. Our results imply that arenaviruses evolved to use bis(monoacylglycero)phosphate to enter cells from late endosomes.
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12
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Exploring interactions between extracellular vesicles and cells for innovative drug delivery system design. Adv Drug Deliv Rev 2021; 173:252-278. [PMID: 33798644 DOI: 10.1016/j.addr.2021.03.017] [Citation(s) in RCA: 54] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 03/15/2021] [Accepted: 03/25/2021] [Indexed: 02/06/2023]
Abstract
Extracellular vesicles (EVs) are submicron cell-secreted structures containing proteins, nucleic acids and lipids. EVs can functionally transfer these cargoes from one cell to another to modulate physiological and pathological processes. Due to their presumed biocompatibility and capacity to circumvent canonical delivery barriers encountered by synthetic drug delivery systems, EVs have attracted considerable interest as drug delivery vehicles. However, it is unclear which mechanisms and molecules orchestrate EV-mediated cargo delivery to recipient cells. Here, we review how EV properties have been exploited to improve the efficacy of small molecule drugs. Furthermore, we explore which EV surface molecules could be directly or indirectly involved in EV-mediated cargo transfer to recipient cells and discuss the cellular reporter systems with which such transfer can be studied. Finally, we elaborate on currently identified cellular processes involved in EV cargo delivery. Through these topics, we provide insights in critical effectors in the EV-cell interface which may be exploited in nature-inspired drug delivery strategies.
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13
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Gruenberg J. Life in the lumen: The multivesicular endosome. Traffic 2021; 21:76-93. [PMID: 31854087 PMCID: PMC7004041 DOI: 10.1111/tra.12715] [Citation(s) in RCA: 110] [Impact Index Per Article: 36.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 10/30/2019] [Accepted: 10/31/2019] [Indexed: 12/12/2022]
Abstract
The late endosomes/endo‐lysosomes of vertebrates contain an atypical phospholipid, lysobisphosphatidic acid (LBPA) (also termed bis[monoacylglycero]phosphate [BMP]), which is not detected elsewhere in the cell. LBPA is abundant in the membrane system present in the lumen of this compartment, including intralumenal vesicles (ILVs). In this review, the current knowledge on LBPA and LBPA‐containing membranes will be summarized, and their role in the control of endosomal cholesterol will be outlined. Some speculations will also be made on how this system may be overwhelmed in the cholesterol storage disorder Niemann‐Pick C. Then, the roles of intralumenal membranes in endo‐lysosomal dynamics and functions will be discussed in broader terms. Likewise, the mechanisms that drive the biogenesis of intralumenal membranes, including ESCRTs, will also be discussed, as well as their diverse composition and fate, including degradation in lysosomes and secretion as exosomes. This review will also discuss how intralumenal membranes are hijacked by pathogenic agents during intoxication and infection, and what is the biochemical composition and function of the intra‐endosomal lumenal milieu. Finally, this review will allude to the size limitations imposed on intralumenal vesicle functions and speculate on the possible role of LBPA as calcium chelator in the acidic calcium stores of endo‐lysosomes.
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Affiliation(s)
- Jean Gruenberg
- Biochemistry Department, University of Geneva, Geneva, Switzerland
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14
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Carrière F, Longhi S, Record M. The endosomal lipid bis(monoacylglycero) phosphate as a potential key player in the mechanism of action of chloroquine against SARS-COV-2 and other enveloped viruses hijacking the endocytic pathway. Biochimie 2020; 179:237-246. [PMID: 32485205 PMCID: PMC7261073 DOI: 10.1016/j.biochi.2020.05.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 05/26/2020] [Accepted: 05/27/2020] [Indexed: 02/06/2023]
Abstract
The anti-malarial drug Chloroquine (CQ) and its derivative hydroxychloroquine have shown antiviral activities in vitro against many viruses, including coronaviruses, dengue virus and the biosafety level 4 Nipah and Hendra paramyxoviruses. The in vivo efficacy of CQ in the treatment of COVID-19 is currently a matter of debate. CQ is a lysosomotrophic compound that accumulates in lysosomes, as well as in food vacuoles of Plasmodium falciparum. In the treatment of malaria, CQ impairs the digestion and growth of the parasite by increasing the pH of the food vacuole. Similarly, it is assumed that the antiviral effects of CQ results from the increase of lysosome pH and the inhibition of acidic proteases involved in the maturation of virus fusion protein. CQ has however other effects, among which phospholipidosis, characterized by the accumulation of multivesicular bodies within the cell. The increase in phospholipid species particularly concerns bis(monoacylglycero)phosphate (BMP), a specific lipid of late endosomes involved in vesicular trafficking and pH-dependent vesicle budding. It was shown previously that drugs like progesterone, the cationic amphiphile U18666A and the phospholipase inhibitor methyl arachidonyl fluoro phosphonate (MAFP) induce the accumulation of BMP in THP-1 cells and decrease cell infection by human immunodeficiency virus. HIV viral particles were found to be retained into large endosomal-type vesicles, preventing virus spreading. Since BMP was also reported to favour virus entry through hijacking of the endocytic pathway, we propose here that BMP could play a dual role in viral infection, with its antiviral effects triggered by lysosomotropic drugs like CQ.
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Affiliation(s)
- Frédéric Carrière
- Aix Marseille Univ, CNRS, BIP, UMR7281, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 9, France.
| | - Sonia Longhi
- Aix Marseille Univ, CNRS, AFMB, UMR7257, 163 Avenue de Luminy, 13288, Marseille cedex 09, France
| | - Michel Record
- UMR INSERM 1037-CRCT (Cancer Research Center of Toulouse), University of Toulouse III Paul Sabatier, Team "Cholesterol Metabolism and Therapeutic Innovations,", 2 Avenue Hubert Curien, 31037, Toulouse cedex 1, France.
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15
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Luquain-Costaz C, Rabia M, Hullin-Matsuda F, Delton I. Bis(monoacylglycero)phosphate, an important actor in the host endocytic machinery hijacked by SARS-CoV-2 and related viruses. Biochimie 2020; 179:247-256. [PMID: 33159981 PMCID: PMC7642752 DOI: 10.1016/j.biochi.2020.10.018] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 10/28/2020] [Accepted: 10/29/2020] [Indexed: 12/12/2022]
Abstract
Viruses, including the novel coronavirus SARS-CoV-2, redirect infected cell metabolism to their own purposes. After binding to its receptor angiotensin-converting enzyme 2 (ACE2) on the cell surface, the SARS-CoV-2 is taken up by receptor-mediated endocytosis ending in the acidic endolysosomal compartment. The virus hijacks the endosomal machinery leading to fusion of viral and endosomal membranes and release of the viral RNA into the cytosol. This mini-review specifically highlights the membrane lipid organization of the endosomal system focusing on the unconventional and late endosome/lysosome-specific phospholipid, bis(monoacylglycero)phosphate (BMP). BMP is enriched in alveolar macrophages of lung, one of the target tissue of SARS-CoV-2. This review details the BMP structure, its unsaturated fatty acid composition and fusogenic properties that are essential for the highly dynamic formation of the intraluminal vesicles inside the endosomes. Interestingly, BMP is necessary for infection and replication of enveloped RNA virus such as SARS-CoV-1 and Dengue virus. We also emphasize the role of BMP in lipid sorting and degradation, especially cholesterol transport in cooperation with Niemann Pick type C proteins (NPC 1 and 2) and with some oxysterol-binding protein (OSBP)-related proteins (ORPs) as well as in sphingolipid degradation. Interestingly, numerous virus infection required NPC1 as well as ORPs along the endocytic pathway. Furthermore, BMP content is increased during pathological endosomal lipid accumulation in various lysosomal storage disorders. This is particularly important knowing the high percentage of patients with metabolic disorders among the SARS-CoV-2 infected patients presenting severe forms of COVID-19.
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Affiliation(s)
- Céline Luquain-Costaz
- Univ-Lyon, CarMeN Laboratory, Inserm U1060, INRAe U1397, INSA Lyon, Villeurbanne, France
| | - Maxence Rabia
- Univ-Lyon, CarMeN Laboratory, Inserm U1060, INRAe U1397, INSA Lyon, Villeurbanne, France
| | | | - Isabelle Delton
- Univ-Lyon, CarMeN Laboratory, Inserm U1060, INRAe U1397, INSA Lyon, Villeurbanne, France.
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16
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Showalter MR, Berg AL, Nagourney A, Heil H, Carraway KL, Fiehn O. The Emerging and Diverse Roles of Bis(monoacylglycero) Phosphate Lipids in Cellular Physiology and Disease. Int J Mol Sci 2020; 21:ijms21218067. [PMID: 33137979 PMCID: PMC7663174 DOI: 10.3390/ijms21218067] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 10/22/2020] [Accepted: 10/26/2020] [Indexed: 02/06/2023] Open
Abstract
Although understudied relative to many phospholipids, accumulating evidence suggests that bis(monoacylglycero)phosphate (BMP) is an important class of regulatory lipid that plays key roles in lysosomal integrity and function. BMPs are rare in most mammalian tissues, comprising only a few percent of total cellular lipid content, but are elevated in cell types such as macrophages that rely heavily on lysosomal function. BMPs are markedly enriched in endosomal and lysosomal vesicles compared to other organelles and membranous structures, and their unique sn-1:sn-1′ stereoconfiguration may confer stability within the hydrolytic lysosomal environment. BMP-enriched vesicles serve in endosomal-lysosomal trafficking and function as docking structures for the activation of lysosomal hydrolytic enzymes, notably those involved in the catabolic breakdown of sphingolipids. BMP levels are dysregulated in lysosomal storage disorders, phospholipidosis, metabolic diseases, liver and kidney diseases and neurodegenerative disorders. However, whether BMP alteration is a mediator or simply a marker of pathological states is unclear. Likewise, although BMP acyl chain composition may be altered with disease states, the functional significance of specific BMP species remains to be resolved. Newly developed tools for untargeted lipidomic analysis, together with a deeper understanding of enzymes mediating BMP synthesis and degradation, will help shed further light on the functional significance of BMPs in cellular physiology and pathology.
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Affiliation(s)
- Megan R. Showalter
- NIH West Coast Metabolomics Center, University of California Davis, Davis, CA 95616, USA; (M.R.S.); (A.N.); (H.H.)
| | - Anastasia L. Berg
- Department of Biochemistry and Molecular Medicine, UC Davis School of Medicine, Sacramento, CA 95817, USA; (A.L.B.); (K.L.C.III)
| | - Alexander Nagourney
- NIH West Coast Metabolomics Center, University of California Davis, Davis, CA 95616, USA; (M.R.S.); (A.N.); (H.H.)
| | - Hailey Heil
- NIH West Coast Metabolomics Center, University of California Davis, Davis, CA 95616, USA; (M.R.S.); (A.N.); (H.H.)
| | - Kermit L. Carraway
- Department of Biochemistry and Molecular Medicine, UC Davis School of Medicine, Sacramento, CA 95817, USA; (A.L.B.); (K.L.C.III)
| | - Oliver Fiehn
- NIH West Coast Metabolomics Center, University of California Davis, Davis, CA 95616, USA; (M.R.S.); (A.N.); (H.H.)
- Correspondence:
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17
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Abstract
Rhabdoviruses are enveloped viruses with a negative-sense single strand RNA genome and are widespread among a great variety of organisms. In their membrane, they have a single glycoprotein (G) that mediates both virus attachment to cellular receptors and fusion between viral and endosomal membranes allowing viral genome release in the cytoplasm. We present structural and cellular aspects of Rhabdovirus entry into their host cell with a focus on vesicular stomatitis virus (VSV) and rabies virus (RABV) for which the early events of the viral cycle have been extensively studied. Recent data have shown that the only VSV receptors are the members of the LDL-R family. This is in contrast with RABV for which multiple receptors belonging to unrelated families have been identified. Despite having different receptors, after attachment, rhabdovirus internalization occurs through clathrin-mediated endocytosis (CME) in an actin-dependent manner. There are still debates about the exact endocytic pathway of VSV in the cell and on RABV transport in the neuronal axon. In any case, fusion is triggered in the endosomal vesicle via a low-pH induced structural rearrangement of G from its pre- to its postfusion conformation. Vesiculovirus G is one of the best characterized fusion glycoproteins as the previously reported crystal structures of the pre- and postfusion states have been recently completed by those of intermediates during the structural transition. Understanding the entry pathway of rhabdoviruses may have strong impact in biotechnologies as, for example, VSV G is used for pseudotyping lentiviruses to promote efficient transduction, and VSV is a promising oncolytic virus.
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18
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Exosomes Exploit the Virus Entry Machinery and Pathway To Transmit Alpha Interferon-Induced Antiviral Activity. J Virol 2018; 92:JVI.01578-18. [PMID: 30282711 DOI: 10.1128/jvi.01578-18] [Citation(s) in RCA: 87] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 09/10/2018] [Indexed: 02/07/2023] Open
Abstract
Alpha interferon (IFN-α) induces the transfer of resistance to hepatitis B virus (HBV) from liver nonparenchymal cells (LNPCs) to hepatocytes via exosomes. However, little is known about the entry machinery and pathway involved in the transmission of IFN-α-induced antiviral activity. In this study, we found that macrophage exosomes uniquely depend on T cell immunoglobulin and mucin receptor 1 (TIM-1), a hepatitis A virus (HAV) receptor, to enter hepatocytes for delivering IFN-α-induced anti-HBV activity. Moreover, two primary endocytic routes for virus infection, clathrin-mediated endocytosis (CME) and macropinocytosis, collaborate to permit exosome entry and anti-HBV activity transfer. Subsequently, lysobisphosphatidic acid (LBPA), an anionic lipid closely related to endosome penetration of virus, facilitates membrane fusion of exosomes in late endosomes/multivesicular bodies (LEs/MVBs) and the accompanying exosomal cargo uncoating. Together, our findings provide comprehensive insights into the transmission route of macrophage exosomes to efficiently deliver IFN-α-induced antiviral substances and highlight the similarities between the entry mechanisms of exosomes and virus.IMPORTANCE Our previous study showed that LNPC-derived exosomes could transmit IFN-α-induced antiviral activity to HBV replicating hepatocytes, but the concrete transmission mechanisms, which include exosome entry and exosomal cargo release, remain unclear. In this study, we found that virus entry machinery and pathway were also applied to exosome-mediated cell-to-cell antiviral activity transfer. Macrophage-derived exosomes distinctively exploit hepatitis A virus receptor for access to hepatocytes. Later, CME and macropinocytosis are utilized by exosomes, followed by exosome-endosome fusion for efficient transfer of IFN-α-induced anti-HBV activity. We believe that understanding the cellular entry pathway of exosomes will be beneficial to designing exosomes as efficient vehicles for antiviral therapy.
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19
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Jedynak M, Worch R, Podsiadła-Białoskórska M, Chroboczek J, Szołajska E. Cholesterol and phosphatidylserine are engaged in adenoviral dodecahedron endocytosis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:2215-2223. [DOI: 10.1016/j.bbamem.2018.09.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 08/14/2018] [Accepted: 09/05/2018] [Indexed: 12/31/2022]
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20
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Salata C, Calistri A, Parolin C, Baritussio A, Palù G. Antiviral activity of cationic amphiphilic drugs. Expert Rev Anti Infect Ther 2017; 15:483-492. [PMID: 28286997 PMCID: PMC7103695 DOI: 10.1080/14787210.2017.1305888] [Citation(s) in RCA: 95] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Introduction: Emerging and reemerging viral infections represent a major concern for human and veterinary public health and there is an urgent need for the development of broad-spectrum antivirals. Areas covered: A recent strategy in antiviral research is based on the identification of molecules targeting host functions required for infection of multiple viruses. A number of FDA-approved drugs used to treat several human diseases are cationic amphiphilic drugs (CADs) that have the ability to accumulate inside cells affecting several structures/functions hijacked by viruses during infection. In this review we summarized the CADs’ chemical properties and effects on the cells and reported the main FDA-approved CADs that have been identified so far as potential antivirals in drug repurposing studies. Expert commentary: Although there have been concerns regarding the efficacy and the possible side effects of the off-label use of CADs as antivirals, they seem to represent a promising starting point for the development of broad-spectrum antiviral strategies. Further knowledge about their mechanism of action is required to improve their antiviral activity and to reduce the risk of side effects.
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Affiliation(s)
- Cristiano Salata
- a Department of Molecular Medicine , University of Padova , Padova , Italy
| | - Arianna Calistri
- a Department of Molecular Medicine , University of Padova , Padova , Italy
| | - Cristina Parolin
- a Department of Molecular Medicine , University of Padova , Padova , Italy
| | - Aldo Baritussio
- b Clinica Medica 1, Department of Medicine , University of Padova , Padova , Italy
| | - Giorgio Palù
- a Department of Molecular Medicine , University of Padova , Padova , Italy
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21
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White JM, Whittaker GR. Fusion of Enveloped Viruses in Endosomes. Traffic 2016; 17:593-614. [PMID: 26935856 PMCID: PMC4866878 DOI: 10.1111/tra.12389] [Citation(s) in RCA: 282] [Impact Index Per Article: 35.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2016] [Revised: 02/25/2016] [Accepted: 02/25/2016] [Indexed: 12/12/2022]
Abstract
Ari Helenius launched the field of enveloped virus fusion in endosomes with a seminal paper in the Journal of Cell Biology in 1980. In the intervening years, a great deal has been learned about the structures and mechanisms of viral membrane fusion proteins as well as about the endosomes in which different enveloped viruses fuse and the endosomal cues that trigger fusion. We now recognize three classes of viral membrane fusion proteins based on structural criteria and four mechanisms of fusion triggering. After reviewing general features of viral membrane fusion proteins and viral fusion in endosomes, we delve into three characterized mechanisms for viral fusion triggering in endosomes: by low pH, by receptor binding plus low pH and by receptor binding plus the action of a protease. We end with a discussion of viruses that may employ novel endosomal fusion‐triggering mechanisms. A key take‐home message is that enveloped viruses that enter cells by fusing in endosomes traverse the endocytic pathway until they reach an endosome that has all of the environmental conditions (pH, proteases, ions, intracellular receptors and lipid composition) to (if needed) prime and (in all cases) trigger the fusion protein and to support membrane fusion.
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Affiliation(s)
- Judith M White
- Department of Cell Biology, University of Virginia, Charlottesville, VA, USA
| | - Gary R Whittaker
- Department of Microbiology & Immunology, Cornell University, Ithaca, NY, USA
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22
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Abstract
Bis(monoacylglycero)phosphate (BMP) is a structural isomer of phosphatidylglycerol (PtdGro) with an unusual sn-1:sn-1' fatty acyl configuration and is found almost exclusively in late endosomes/lysosomes. BMP comprises only about 1-2% of the total phospholipids in most mammalian cells, but accumulates in tissues of humans and animals with lysosomal storage disorders including the gangliosidoses. Total BMP content was significantly greater in cells of macrophage/microglial origin than in cells of macroglial origin. BMP composition was similar in tumorigenic/metastatic macrophages and non-tumorigenic macrophages/microglia. Finally, BMP fatty acid composition differed between cells grown in culture and obtained in vivo suggesting an influence from growth environment.
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Affiliation(s)
- Zeynep Akgoc
- Biology Department, Boston College, 140 Commonwealth Ave, MA, 02467, Chestnut Hill, USA,
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23
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Mazzon M, Mercer J. Lipid interactions during virus entry and infection. Cell Microbiol 2014; 16:1493-502. [PMID: 25131438 PMCID: PMC4265854 DOI: 10.1111/cmi.12340] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Revised: 07/26/2014] [Accepted: 08/01/2014] [Indexed: 12/14/2022]
Abstract
For entry and infection viruses have developed numerous strategies to subjugate indispensable cellular factors and functions. Host cell lipids and cellular lipid synthesis machinery are no exception. Not only do viruses exploit existing lipid signalling and modifications for virus entry and trafficking, they also reprogram lipid synthesis, metabolism, and compartmentalization for assembly and egress. Here we review these various concepts and highlight recent progress in understanding viral interactions with host cell lipids during entry and assembly.
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Affiliation(s)
- Michela Mazzon
- MRC-Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT, UK
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24
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Amini-Bavil-Olyaee S, Choi YJ, Lee JH, Shi M, Huang IC, Farzan M, Jung JU. The antiviral effector IFITM3 disrupts intracellular cholesterol homeostasis to block viral entry. Cell Host Microbe 2014; 13:452-64. [PMID: 23601107 PMCID: PMC3646482 DOI: 10.1016/j.chom.2013.03.006] [Citation(s) in RCA: 267] [Impact Index Per Article: 26.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Revised: 12/04/2012] [Accepted: 03/19/2013] [Indexed: 12/21/2022]
Abstract
Vesicle-membrane-protein-associated protein A (VAPA) and oxysterol-binding protein (OSBP) regulate intracellular cholesterol homeostasis, which is required for many virus infections. During entry, viruses or virus-containing vesicles can fuse with endosomal membranes to mediate the cytosolic release of virions, and alterations in endosomal cholesterol can inhibit this invasion step. We show that the antiviral effector protein interferon-inducible transmembrane protein 3 (IFITM3) interacts with VAPA and prevents its association with OSBP, thereby disrupting intracellular cholesterol homeostasis and inhibiting viral entry. By altering VAPA-OSBP function, IFITM3 induces a marked accumulation of cholesterol in multivesicular bodies and late endosomes, which inhibits the fusion of intraluminal virion-containing vesicles with endosomal membranes and thereby blocks virus release into the cytosol. Consequently, ectopic expression or depletion of the VAPA gene profoundly affects IFITM3-mediated inhibition of viral entry. Thus, IFITM3 disrupts intracellular cholesterol homeostasis to block viral entry, further underscoring the importance of cholesterol in virus infection.
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Affiliation(s)
- Samad Amini-Bavil-Olyaee
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Harlyne J. Norris Cancer Research Tower, 1450 Biggy Street, Los Angeles, CA 90033, USA
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25
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UVRAG is required for virus entry through combinatorial interaction with the class C-Vps complex and SNAREs. Proc Natl Acad Sci U S A 2014; 111:2716-21. [PMID: 24550300 DOI: 10.1073/pnas.1320629111] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Enveloped viruses exploit the endomembrane system to enter host cells. Through a cascade of membrane-trafficking events, virus-bearing vesicles fuse with acidic endosomes and/or lysosomes mediated by SNAREs triggering viral fusion. However, the molecular mechanisms underlying this process remain elusive. Here, we found that UV-radiation resistance-associated gene (UVRAG), an autophagic tumor suppressor, is required for the entry of the prototypic negative-strand RNA virus, including influenza A virus and vesicular stomatitis virus, by a mechanism independent of IFN and autophagy. UVRAG mediates viral endocytic transport and membrane penetration through interactions with the class C vacuolar protein sorting (C-Vps) tethering complex and endosomal glutamine-containing SNAREs [syntaxin 7 (STX7), STX8, and vesicle transport through t-SNARE homolog 1B (Vti1b)], leading to the assembly of a fusogenic trans-SNARE complex involving vesicle-associated membrane protein (VAMP8), but not VAMP7. Indeed, UVRAG stimulates VAMP8 translocation to virus-bearing endosomes. Inhibition of VAMP8, but not VAMP7, significantly reduces viral entry. Our data indicate that UVRAG, in concert with C-Vps, regulates viral entry by assembling a specific fusogenic SNARE complex. Thus, UVRAG governs downstream viral entry, highlighting an important pathway capable of potential antiviral therapeutics.
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26
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Markosyan RM, Cohen FS. The transmembrane domain and acidic lipid flip-flop regulates voltage-dependent fusion mediated by class II and III viral proteins. PLoS One 2013; 8:e76174. [PMID: 24124539 PMCID: PMC3790697 DOI: 10.1371/journal.pone.0076174] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 08/12/2013] [Indexed: 11/18/2022] Open
Abstract
Voltage dependence of fusion induced by class II and class III viral fusion proteins was investigated. Class II proteins from Ross River and Sindbus virus and a mutant class III protein from Epstein Barr virus were found to induce cell-cell fusion that is voltage dependent. Combined with previous studies, in all, four class II and two class III protein have now been shown to exhibit voltage-dependent fusion, demonstrating that this is probably a general phenomenon for these two classes of viral fusion proteins. In the present study, monitoring fusion of pseudovirus expressing Vesicular Stomatitis virus (VSV) G within endosomes shows that here, too, fusion is voltage dependent. This supports the claim that voltage dependence of fusion is biologically relevant and that cell-cell fusion reliably models the voltage dependence. Fusion induced by class I viral proteins is independent of voltage; chimeras expressing the ectodomain of a class I fusion protein and the transmembrane domain of VSV G could therefore be used to explore the location within the protein responsible for voltage dependence. Results showed that the transmembrane domain is the region associated with voltage dependence. Experiments in which cells were enriched with acidic lipids led to the conclusion that it is the flip-flop of acidic lipids that carries the charge responsible for the observed voltage dependence of fusion. This flip-flop occurred downstream of hemifusion, in accord with previous findings that the voltage dependent steps of fusion occur at a stage subsequent to hemifusion.
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Affiliation(s)
- Ruben M. Markosyan
- Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, Illinois, United States of America
| | - Fredric S. Cohen
- Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, Illinois, United States of America
- * E-mail:
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27
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Hastie E, Cataldi M, Marriott I, Grdzelishvili VZ. Understanding and altering cell tropism of vesicular stomatitis virus. Virus Res 2013; 176:16-32. [PMID: 23796410 DOI: 10.1016/j.virusres.2013.06.003] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2013] [Revised: 06/06/2013] [Accepted: 06/07/2013] [Indexed: 12/18/2022]
Abstract
Vesicular stomatitis virus (VSV) is a prototypic nonsegmented negative-strand RNA virus. VSV's broad cell tropism makes it a popular model virus for many basic research applications. In addition, a lack of preexisting human immunity against VSV, inherent oncotropism and other features make VSV a widely used platform for vaccine and oncolytic vectors. However, VSV's neurotropism that can result in viral encephalitis in experimental animals needs to be addressed for the use of the virus as a safe vector. Therefore, it is very important to understand the determinants of VSV tropism and develop strategies to alter it. VSV glycoprotein (G) and matrix (M) protein play major roles in its cell tropism. VSV G protein is responsible for VSV broad cell tropism and is often used for pseudotyping other viruses. VSV M affects cell tropism via evasion of antiviral responses, and M mutants can be used to limit cell tropism to cell types defective in interferon signaling. In addition, other VSV proteins and host proteins may function as determinants of VSV cell tropism. Various approaches have been successfully used to alter VSV tropism to benefit basic research and clinically relevant applications.
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Affiliation(s)
- Eric Hastie
- Department of Biology, University of North Carolina at Charlotte, 9201 University City Boulevard, Charlotte, NC 28223, United States
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28
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Chapuy-Regaud S, Subra C, Requena M, de Medina P, Amara S, Delton-Vandenbroucke I, Payre B, Cazabat M, Carriere F, Izopet J, Poirot M, Record M. Progesterone and a phospholipase inhibitor increase the endosomal bis(monoacylglycero)phosphate content and block HIV viral particle intercellular transmission. Biochimie 2013; 95:1677-88. [PMID: 23774297 DOI: 10.1016/j.biochi.2013.05.019] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 05/27/2013] [Indexed: 10/26/2022]
Abstract
Progesterone, the cationic amphiphile U18666A and a phospholipase inhibitor (Methyl Arachidonyl Fluoro Phosphonate, MAFP) inhibited by 70%-90% HIV production in viral reservoir cells, i.e. human THP-1 monocytes and monocyte-derived macrophages (MDM). These compounds triggered an inhibition of fluid phase endocytosis (macropinocytosis) and modified cellular lipid homeostasis since endosomes accumulated filipin-stained sterols and Bis(Monoacylglycero)Phosphate (BMP). BMP was quantified using a new cytometry procedure and was increased by 1.25 times with MAFP, 1.7 times with U18666A and 2.5 times with progesterone. MAFP but not progesterone or U18666A inhibited the hydrolysis of BMP by the Pancreatic Lipase Related Protein 2 (PLRP2) as shown by in-vitro experiments. The possible role of sterol transporters in steroid-mediated BMP increase is discussed. Electron microscopy showed the accumulation of viral particles either into large intracellular viral-containing compartments or outside the cells, indicating that endosomal accumulation of BMP could block intracellular biogenesis of viral particles while inhibition of macropinocytosis would prevent viral particle uptake. This is the first report linking BMP metabolism with a natural steroid such as progesterone or with involvement of a phospholipase A1 activity. BMP cellular content could be used as a biomarker for efficient anti-viral drugs.
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Affiliation(s)
- Sabine Chapuy-Regaud
- INSERM, U1043, Equipe Infection virales: persistance, réponse de l'hôte et physiopathologie, Toulouse F-31300, France
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29
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Zhou Y, Simmons G. Development of novel entry inhibitors targeting emerging viruses. Expert Rev Anti Infect Ther 2013. [PMID: 23199399 DOI: 10.1586/eri.12.104] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Emerging viral diseases pose a unique risk to public health, and thus there is a need to develop therapies. A current focus of funding agencies, and hence research, is the development of broad-spectrum antivirals, and in particular, those targeting common cellular pathways. The scope of this article is to review screening strategies and recent advances in this area, with a particular emphasis on antivirals targeting the step of viral entry for emerging lipid-enveloped viruses such as Ebola virus and SARS-coronavirus.
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Affiliation(s)
- Yanchen Zhou
- Blood Systems Research Institute and Department of Laboratory Medicine, University of California, San Francisco, 270 Masonic Avenue, San Francisco, CA 94118, USA
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30
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Matos PM, Marin M, Ahn B, Lam W, Santos NC, Melikyan GB. Anionic lipids are required for vesicular stomatitis virus G protein-mediated single particle fusion with supported lipid bilayers. J Biol Chem 2013; 288:12416-25. [PMID: 23493401 DOI: 10.1074/jbc.m113.462028] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Viral glycoproteins mediate fusion between viral and cellular membranes upon binding to cognate receptors and/or experiencing low pH. Although activation of viral glycoproteins is thought to be necessary and sufficient for fusion, accumulating evidence suggests that additional cellular factors, including lipids, can modulate the fusion process. Understanding the role of lipids in virus entry via endocytosis is impeded by poor accessibility and the highly diverse nature of endosomes. Here we imaged fusion of single retroviral particles pseudotyped with the vesicular stomatitis virus (VSV) G protein with dextran-supported lipid bilayers. Incorporation of diffusible fluorescent labels into the viral membrane and the viral interior enabled detection of the lipid mixing (hemifusion) and content transfer (full fusion) steps of VSV G-mediated fusion at low pH. Although single virus fusion with supported bilayers made of zwitterionic lipids could not be detected, inclusion of anionic lipids, phosphatidylserine, and bis(monoacylglycero)phosphate (BMP), greatly enhanced the efficiency of hemifusion and permitted full fusion. Importantly, lipid mixing always preceded the opening of a fusion pore, demonstrating that VSV G-mediated fusion proceeds through a long-lived hemifusion intermediate. Kinetic analysis of lipid and content transfer showed that the lags between lipid and content mixing defining the lifetime of a hemifusion intermediate were significantly shorter for BMP-containing compared with PS-containing bilayers. The strong fusion-enhancing effect of BMP, a late endosome-resident lipid, is consistent with the model that VSV initiates fusion in early endosomes but releases its core into the cytosol after reaching late endosomal compartments.
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Affiliation(s)
- Pedro M Matos
- Emory Children's Center, Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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31
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Vázquez-Calvo A, Saiz JC, McCullough KC, Sobrino F, Martín-Acebes MA. Acid-dependent viral entry. Virus Res 2012; 167:125-37. [PMID: 22683298 DOI: 10.1016/j.virusres.2012.05.024] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Revised: 05/28/2012] [Accepted: 05/29/2012] [Indexed: 12/21/2022]
Abstract
Virus infection of host cells requires that entry into the cell results in efficient genome release leading to translation and replication. These initial steps revolving around the entry and genomic release processes are crucial for viral progeny generation. Despite the variety of receptors used by viruses to initiate entry, evidence from both enveloped and non-enveloped viral infections is highlighting the important role played by intracellular acidic compartments in the entry of many viruses. These compartments provide connecting nodes within the endocytic network, presenting multiple viral internalization pathways. Endosomal compartments employing an internal acidic pH can trigger molecular mechanisms leading to disassembly of viral particles, thus providing appropriate genome delivery. Accordingly, viruses have evolved to select optimal intracellular conditions for promoting efficient genome release, leading to propagation of the infectious agent. This review will address the implications of cellular compartment involvement in virus infectious processes, and the roles played by the viruses' own machinery, including pH sensing mechanisms and the methodologies applied for studying acid-dependent viral entry into host cells.
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Affiliation(s)
- Angela Vázquez-Calvo
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Cantoblanco, 28049 Madrid, Spain.
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32
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Kooijmans SAA, Vader P, van Dommelen SM, van Solinge WW, Schiffelers RM. Exosome mimetics: a novel class of drug delivery systems. Int J Nanomedicine 2012; 7:1525-41. [PMID: 22619510 PMCID: PMC3356169 DOI: 10.2147/ijn.s29661] [Citation(s) in RCA: 219] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The identification of extracellular phospholipid vesicles as conveyors of cellular information has created excitement in the field of drug delivery. Biological therapeutics, including short interfering RNA and recombinant proteins, are prone to degradation, have limited ability to cross biological membranes, and may elicit immune responses. Therefore, delivery systems for such drugs are under intensive investigation. Exploiting extracellular vesicles as carriers for biological therapeutics is a promising strategy to overcome these issues and to achieve efficient delivery to the cytosol of target cells. Exosomes are a well studied class of extracellular vesicles known to carry proteins and nucleic acids, making them especially suitable for such strategies. However, the considerable complexity and the related high chance of off-target effects of these carriers are major barriers for translation to the clinic. Given that it is well possible that not all components of exosomes are required for their proper functioning, an alternative strategy would be to mimic these vesicles synthetically. By assembly of liposomes harboring only crucial components of natural exosomes, functional exosome mimetics may be created. The low complexity and use of well characterized components strongly increase the pharmaceutical acceptability of such systems. However, exosomal components that would be required for the assembly of functional exosome mimetics remain to be identified. This review provides insights into the composition and functional properties of exosomes, and focuses on components which could be used to enhance the drug delivery properties of exosome mimetics.
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Affiliation(s)
- Sander A A Kooijmans
- Department of Clinical Chemistry and Haematology, University Medical Center Utrecht, Utrecht, The Netherlands
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Molecular and cellular aspects of rhabdovirus entry. Viruses 2012; 4:117-39. [PMID: 22355455 PMCID: PMC3280520 DOI: 10.3390/v4010117] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Revised: 01/05/2012] [Accepted: 01/10/2012] [Indexed: 01/13/2023] Open
Abstract
Rhabdoviruses enter the cell via the endocytic pathway and subsequently fuse with a cellular membrane within the acidic environment of the endosome. Both receptor recognition and membrane fusion are mediated by a single transmembrane viral glycoprotein (G). Fusion is triggered via a low-pH induced structural rearrangement. G is an atypical fusion protein as there is a pH-dependent equilibrium between its pre- and post-fusion conformations. The elucidation of the atomic structures of these two conformations for the vesicular stomatitis virus (VSV) G has revealed that it is different from the previously characterized class I and class II fusion proteins. In this review, the pre- and post-fusion VSV G structures are presented in detail demonstrating that G combines the features of the class I and class II fusion proteins. In addition to these similarities, these G structures also reveal some particularities that expand our understanding of the working of fusion machineries. Combined with data from recent studies that revealed the cellular aspects of the initial stages of rhabdovirus infection, all these data give an integrated view of the entry pathway of rhabdoviruses into their host cell.
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