The Experts below are selected from a list of 12357 Experts worldwide ranked by ideXlab platform
Mark Marsh - One of the best experts on this subject based on the ideXlab platform.
-
A biophysical perspective on receptor-mediated Virus Entry with a focus on HIV.
Biochimica et Biophysica Acta, 2019Co-Authors: Isabel Llorente García, Mark MarshAbstract:Abstract As part of their Entry and infection strategy, Viruses interact with specific receptor molecules expressed on the surface of target cells. The efficiency and kinetics of the Virus-receptor interactions required for a Virus to productively infect a cell is determined by the biophysical properties of the receptors, which are in turn influenced by the receptors' plasma membrane (PM) environments. Currently, little is known about the biophysical properties of these receptor molecules or their engagement during Virus binding and Entry. Here we review Virus-receptor interactions focusing on the human immunodeficiency Virus type 1 (HIV), the etiological agent of acquired immunodeficiency syndrome (AIDS), as a model system. HIV is one of the best characterised enveloped Viruses, with the identity, roles and structure of the key molecules required for infection well established. We review current knowledge of receptor-mediated HIV Entry, addressing the properties of the HIV cell-surface receptors, the techniques used to measure these properties, and the macromolecular interactions and events required for Virus Entry. We discuss some of the key biophysical principles underlying receptor-mediated Virus Entry and attempt to interpret the available data in the context of biophysical mechanisms. We also highlight crucial outstanding questions and consider how new tools might be applied to advance understanding of the biophysical properties of viral receptors and the dynamic events leading to Virus Entry.
-
Mining of Ebola Virus Entry inhibitors identifies approved drugs as two-pore channel pore blockers.
Biochimica et Biophysica Acta, 2018Co-Authors: Christopher J. Penny, Michela Mazzon, Kristin Vassileva, Yu Yuan, Xavier Chee, Elizabeth Yates, Bethan S. Kilpatrick, Shmuel Muallem, Mark MarshAbstract:Abstract Two-pore channels (TPCs) are Ca2+-permeable ion channels localised to the endo-lysosomal system where they regulate trafficking of various cargoes including Viruses. As a result, TPCs are emerging as important drug targets. However, their pharmacology is ill-defined. There are no approved drugs to target them. And their mechanism of ligand activation is largely unknown. Here, we identify a number of FDA-approved drugs as TPC pore blockers. Using a model of the pore of human TPC2 based on recent structures of mammalian TPCs, we virtually screened a database of ~1500 approved drugs. Because TPCs have recently emerged as novel host factors for Ebola Virus Entry, we reasoned that Ebola Virus Entry inhibitors may exert their effects through inhibition of TPCs. Cross-referencing hits from the TPC virtual screen with two recent high throughput anti-Ebola screens yielded approved drugs targeting dopamine and estrogen receptors as common hits. These compounds inhibited endogenous NAADP-evoked Ca2+ release from sea urchin egg homogenates, NAADP-mediated channel activity of TPC2 re-routed to the plasma membrane, and PI(3,5)P2-mediated channel activity of TPC2 expressed in enlarged lysosomes. Mechanistically, single channel analyses showed that the drugs reduced mean open time consistent with a direct action on the pore. Functionally, drug potency in blocking TPC2 activity correlated with inhibition of Ebola Virus-like particle Entry. Our results expand TPC pharmacology through the identification of approved drugs as novel blockers, support a role for TPCs in Ebola Virus Entry, and provide insight into the mechanisms underlying channel regulation. This article is part of a Special Issue entitled: ECS Meeting edited by Claus Heizmann, Joachim Krebs and Jacques Haiech.
-
the cell biology of receptor mediated Virus Entry
Journal of Cell Biology, 2011Co-Authors: Joe Grove, Mark MarshAbstract:The cell imposes multiple barriers to Virus Entry. However, Viruses exploit fundamental cellular processes to gain Entry to cells and deliver their genetic cargo. Virus Entry pathways are largely defined by the interactions between Virus particles and their receptors at the cell surface. These interactions determine the mechanisms of Virus attachment, uptake, intracellular trafficking, and, ultimately, penetration to the cytosol. Elucidating the complex interplay between Viruses and their receptors is necessary for a full understanding of how these remarkable agents invade their cellular hosts.
-
Host–pathogen interactions: The cell biology of receptor-mediated Virus Entry
Journal of Cell Biology, 2011Co-Authors: Joe Grove, Mark MarshAbstract:The cell imposes multiple barriers to Virus Entry. However, Viruses exploit fundamental cellular processes to gain Entry to cells and deliver their genetic cargo. Virus Entry pathways are largely defined by the interactions between Virus particles and their receptors at the cell surface. These interactions determine the mechanisms of Virus attachment, uptake, intracellular trafficking, and, ultimately, penetration to the cytosol. Elucidating the complex interplay between Viruses and their receptors is necessary for a full understanding of how these remarkable agents invade their cellular hosts.
-
Mechanisms of enveloped Virus Entry into animal cells.
Advanced Drug Delivery Reviews, 1998Co-Authors: Per Johan Klasse, Romke Bron, Mark MarshAbstract:Abstract The ability of Viruses to transfer macromolecules between cells makes them attractive starting points for the design of biological delivery vehicles. Virus-based vectors and sub-viral systems are already finding biotechnological and medical applications for gene, peptide, vaccine and drug delivery. Progress has been made in understanding the cellular and molecular mechanisms underlying Virus Entry, particularly in identifying Virus receptors. However, receptor binding is only a first step and we now have to understand how these molecules facilitate Entry, how enveloped Viruses fuse with cells or non-enveloped Viruses penetrate the cell membrane, and what happens following penetration. Only through these detailed analyses will the full potential of Viruses as vectors and delivery vehicles be realised. Here we discuss aspects of the Entry mechanisms for several well-characterised viral systems. We do not attempt to provide a fully comprehensive review of Virus Entry but focus primarily on enveloped Viruses.
Roselyn J. Eisenberg - One of the best experts on this subject based on the ideXlab platform.
-
structure of unliganded hsv gd reveals a mechanism for receptor mediated activation of Virus Entry
The EMBO Journal, 2005Co-Authors: Claude Krummenacher, Gary H. Cohen, Roselyn J. Eisenberg, Vinit M Supekar, Charles J Whitbeck, Eric Lazear, Sarah A Connolly, Don C Wiley, Andrea CarfiAbstract:Herpes simplex Virus (HSV) Entry into cells requires binding of the envelope glycoprotein D (gD) to one of several cell surface receptors. The 50 C-terminal residues of the gD ectodomain are essential for Virus Entry, but not for receptor binding. We have determined the structure of an unliganded gD molecule that includes these C-terminal residues. The structure reveals that the C-terminus is anchored near the N-terminal region and masks receptor-binding sites. Locking the C-terminus in the position observed in the crystals by an intramolecular disulfide bond abolished receptor binding and Virus Entry, demonstrating that this region of gD moves upon receptor binding. Similarly, a point mutant that would destabilize the C-terminus structure was nonfunctional for Entry, despite increased affinity for receptors. We propose that a controlled displacement of the gD C-terminus upon receptor binding is an essential feature of HSV Entry, ensuring the timely activation of membrane fusion.
-
Function of herpes simplex Virus type 1 gD mutants with different receptor-binding affinities in Virus Entry and fusion.
Journal of Virology, 2003Co-Authors: Richard S. B. Milne, Sheri L. Hanna, Sharon H. Willis, Gary H. Cohen, Roselyn J. EisenbergAbstract:We have studied the receptor-specific function of four linker-insertion mutants of herpes simplex Virus type 1 glycoprotein D (gD) representing each of the functional regions of gD. We used biosensor analysis to measure binding of the gD mutants to the receptors HVEM (HveA) and nectin-1 (HveC). One of the mutants, gD(34t), failed to bind HVEMt but showed essentially wild-type (WT) affinity for nectin-1t. The receptor-binding kinetics and affinities of the other three gD mutants varied over a 1,000-fold range, but each mutant had the same affinity for both receptors. All of the mutants were functionally impaired in Virus Entry and cell fusion, and the levels of activity were strikingly similar in these two assays. gD(34)-containing Virus was defective on HVEM-expressing cells but did enter nectin-1-expressing cells to about 60% of WT levels. This showed that the defect of this form of gD on HVEM-expressing cells was primarily one of binding and that this was separable from its later function in Virus Entry. gD(243t) showed WT binding affinity for both receptors, but Virus containing this form of gD had a markedly reduced rate of Entry, suggesting that gD(243) is impaired in a postbinding step in the Entry process. There was no correlation between gD mutant activity in fusion or Virus Entry and receptor-binding affinity. We conclude that gD functions in Virus Entry and cell fusion regardless of its receptor-binding kinetics and that as long as binding to a functional receptor occurs, Entry will progress.
Deepak Shukla - One of the best experts on this subject based on the ideXlab platform.
-
Exploiting Herpes Simplex Virus Entry for Novel Therapeutics
Viruses, 2013Co-Authors: Satvik Hadigal, Deepak ShuklaAbstract:Herpes Simplex Virus (HSV) is associated with a variety of diseases such as genital herpes and numerous ocular diseases. At the global level, high prevalence of individuals who are seropositive for HSV, combined with its inconspicuous infection, remains a cause for major concern. At the molecular level, HSV Entry into a host cell involves multiple steps, primarily the interaction of viral glycoproteins with various cell surface receptors, many of which have alternate substitutes. The molecular complexity of the Virus to enter a cell is also enhanced by the existence of different modes of viral Entry. The availability of many Entry receptors, along with a variety of Entry mechanisms, has resulted in a Virus that is capable of infecting virtually all cell types. While HSV uses a wide repertoire of viral and host factors in establishing infection, current therapeutics aimed against the Virus are not as diversified. In this particular review, we will focus on the initial Entry of the Virus into the cell, while highlighting potential novel therapeutics that can control this process. Virus Entry is a decisive step and effective therapeutics can translate to less Virus replication, reduced cell death, and detrimental symptoms.
-
viral Entry mechanisms cellular and viral mediators of herpes simplex Virus Entry
FEBS Journal, 2009Co-Authors: Jihan Akhtar, Deepak ShuklaAbstract:Herpes simplex Virus type-1 and type-2 are highly prevalent human pathogens causing life-long infections. The process of infection begins when the virions bind heparan sulfate moieties present on host cell surfaces. This initial attachment then triggers a cascade of molecular interactions involving multiple viral and host cell proteins and receptors, leading to penetration of the viral nucleocapsid and tegument proteins into the cytoplasm. The nucleocapsid is then transported to the nuclear membrane and the viral DNA is released for replication in the nucleus. Recent studies have revealed that herpes simplex Virus Entry or penetration into cells may be a highly complex process and the mechanism of Entry may demonstrate unique cell-type specificities. Although specificities clearly exist, past and ongoing studies demonstrate that herpes simplex Virus may share certain common receptors and pathways that are also used by many other human Viruses. This minireview helps to shed light on recent revelations on the herpes simplex Virus Entry process.
Joe Grove - One of the best experts on this subject based on the ideXlab platform.
-
the cell biology of receptor mediated Virus Entry
Journal of Cell Biology, 2011Co-Authors: Joe Grove, Mark MarshAbstract:The cell imposes multiple barriers to Virus Entry. However, Viruses exploit fundamental cellular processes to gain Entry to cells and deliver their genetic cargo. Virus Entry pathways are largely defined by the interactions between Virus particles and their receptors at the cell surface. These interactions determine the mechanisms of Virus attachment, uptake, intracellular trafficking, and, ultimately, penetration to the cytosol. Elucidating the complex interplay between Viruses and their receptors is necessary for a full understanding of how these remarkable agents invade their cellular hosts.
-
Host–pathogen interactions: The cell biology of receptor-mediated Virus Entry
Journal of Cell Biology, 2011Co-Authors: Joe Grove, Mark MarshAbstract:The cell imposes multiple barriers to Virus Entry. However, Viruses exploit fundamental cellular processes to gain Entry to cells and deliver their genetic cargo. Virus Entry pathways are largely defined by the interactions between Virus particles and their receptors at the cell surface. These interactions determine the mechanisms of Virus attachment, uptake, intracellular trafficking, and, ultimately, penetration to the cytosol. Elucidating the complex interplay between Viruses and their receptors is necessary for a full understanding of how these remarkable agents invade their cellular hosts.
Bernard Moss - One of the best experts on this subject based on the ideXlab platform.
-
Virus Entry — an unwilling collaboration by the cell
Current Opinion in Virology, 2013Co-Authors: Ari Helenius, Bernard MossAbstract:How simple, lifeless particles such as Viruses cause devastating diseases and epidemics that affect the everyday lives of most people remain incompletely understood despite intense research efforts. We have determined the genomic sequences of hundreds of Viruses, analyzed their structures and composition, and probed their replication mechanisms. Yet, aside for vaccination, we have few means by which we can inhibit their spread and cure diseases that they cause. The success of Viruses can be attributed to coevolution with their hosts to which they are optimally adapted. Moreover, the apparent simplicity of Viruses is deceptive as they extensively exploit cellular processes. Indeed, the dependence on cell functions provides a form of camouflage because it is difficult to inhibit Viruses without hurting the cells and thereby damaging the hosts. Clearly, the ideal time to halt a Virus infection is at the Entry stage. The life cycle of horizontally transmitted Viruses begins with the attachment and Entry of infectious Virus particles into susceptible cells. Viruses have solved the Entry problem in a myriad of ways. Some are encased in a lipoprotein membrane that fuses with cellular membranes to deliver the internal contents including genomic material and associated proteins into the cytosol. Others, lacking an outer membrane, penetrate cellular membranes by lysis or by forming pores. It follows that a full understanding of the Entry process requires knowledge of the structure of the Virus particle as well as the cellular components to which it binds, the steps following the initial interaction, the penetration mechanisms and the release or uncoating of the genetic material. From an era dominated almost entirely by electron microscopy, the field of Virus Entry has developed into a dynamic, highly interdisciplinary enterprise. As illustrated by the collection of chapters in this volume, the effort now comprises structural biology, biophysics, biochemistry, molecular and cell biology, physiology, systems biology, immunology, and medicine. Although some Viruses enter through the plasma membrane of host cells, many interact with cellular receptors thereby activating signaling pathways that trigger endocytosis of the Virus followed by transport into a complex network of functionally interconnected endosomal organelles. At some point, the Virus activates its membrane penetration machinery. While a few Viruses only deliver their genetic material into the cytosol, most of them enter the cytosol either in intact form or devoid of their lipid envelope. The penetration step involves conformational changes in structurally metastable viral capsids or surface proteins that are triggered by low pH, interactions with receptors, proteolytic cleavages, or other cues. The journey may continue to the nucleus or to specific locations within the cytoplasm. Entry is generally a stepwise process in which the dismantling of the Virus particle occurs in parallel with the movement of the incoming Virus deeper into the cell. The reviews in this issue focus on a variety of Viruses and Virus families and describe individual steps in their Entry program. Although Viruses of the same family tend to use the same general pathways, the detailed mechanisms of binding, signaling, penetration, and uncoating differ. Fusion between the viral envelope and a cellular membrane constitutes a key step in the Entry of enveloped Viruses. The viral glycoproteins responsible for mediating fusion have been extensively studied in several Virus families. For many of them, X-ray crystal structures in different conformations are available. Theodore C. Pierson and Margaret Kielian discuss the Entry pathways taken by flaviViruses, small single-stranded RNA Viruses that are responsible for diseases such as encephalitis and Dengue fever. The authors describe in detail the fusion step, which is accompanied by a dramatic rearrangement of the surface glycoprotein of these acid-activated Viruses. The herpesViruses comprise a large, successful family of DNA Viruses, some of which cause life-long infections of humans. HerpesViruses differ from some simpler Viruses in that the receptor binding and fusogenic functions are distributed among several proteins. Samuel D. Stampfer and Ekaterina E. Heldwein describe how structural studies have illuminated the fusion process. In particular they focus on the gH/gL complex, which they propose acts as an adaptor that transmits the triggering signal from Virus-specific proteins to the highly conserved gB fusion protein. Two of the reviews describe Entry of non-enveloped Viruses. Max Nibert and Yuko Takagi discuss differences in Entry of several closely related double-stranded RNA Viruses. Surprisingly, these Viruses employ a variety of Entry mechanisms despite similarities in capsid structures. Maarit Suomalainen’s and Urs Greber’s contribution concerns membrane penetration mechanisms evolved by three non-enveloped Virus families that employ different strategies: one has a positive single-stranded RNA genome (picornaVirus) and two have double-stranded DNA genomes (polyomaVirus and adenoVirus). Advances in technology have greatly contributed to progress in understanding Virus Entry. Eileen Sun et al. discuss the adaptation of high-end, live cell imaging methods to study Virus Entry. As Viruses are too small to be resolved by light microscopy, the use of fluorescence microscopy in different modalities has opened the way to elegant studies in which the progress of single Virus particles during Entry can be tracked. Live cell imaging has expanded the toolbox importantly, and is now the main technology used in many Entry studies. The authors also discuss potential problems and limitations of the technology. Pathways of cell-to-cell transmission that do not involve free Virus particles are reviewed by Peng Zhong et al. Results from their group and others have demonstrated that Viruses have different ways by which they can make use of the host cell for transmission. Such transmission can rely on inter-cellular adhesion, cell-to-cell fusion, cellular polarity and intra-cellular trafficking without release of Viruses as freely diffusible particles. These mechanisms are clearly important during the transmission of Viruses in tissues and organisms. In many of the chapters, the possibility of using Entry inhibitors as antivirals is raised and current efforts in this direction are discussed. The review by Timothy J. Henrich and Daniel R. Kuritzkes focuses on this issue explicitly, describing antivirals that target Entry of HIV-1. Whereas some drugs interact with the Virus itself, others target cellular proteins. There is optimism that drug-resistant mutants will be less likely to arise when the latter class of antivirals is used.
-
interaction between the g3 and l5 proteins of the vaccinia Virus Entry fusion complex
Virology, 2011Co-Authors: Cindy L Wolfe, Bernard MossAbstract:The vaccinia Virus Entry-fusion complex (EFC) consists of 10 to 12 proteins that are embedded in the viral membrane and individually required for fusion with the cell and Entry of the core into the cytoplasm. The architecture of the EFC is unknown except for information regarding two pair-wise interactions: A28 with H2 and A16 with G9. Here we used a technique to destabilize the EFC by repressing the expression of individual components and identified a third pair-wise interaction: G3 with L5. These two proteins remained associated under several different EFC destabilization conditions and in each case were immunopurified together as demonstrated by Western blotting. Further evidence for the specific interaction of G3 and L5 was obtained by mass spectrometry. This interaction also occurred when G3 and L5 were expressed in uninfected cells, indicating that no other viral proteins were required. Thus, the present study extends our knowledge of the protein interactions important for EFC assembly and stability.
-
Expression of the A56 and K2 Proteins Is Sufficient To Inhibit Vaccinia Virus Entry and Cell Fusion
Journal of Virology, 2008Co-Authors: Timothy R. Wagenaar, Bernard MossAbstract:Many animal Viruses induce cells to fuse and form syncytia. For vaccinia Virus, this phenomenon is associated with mutations affecting the A56 and K2 proteins, which form a multimer (A56/K2) on the surface of infected cells. Recent evidence that A56/K2 interacts with the Entry/fusion complex (EFC) and that the EFC is necessary for syncytium formation furnishes a strong connection between Virus Entry and cell fusion. Among the important remaining questions are whether A56/K2 can prevent Virus Entry as well as cell-cell fusion and whether these two viral proteins are sufficient as well as necessary for this. To answer these questions, we transiently and stably expressed A56 and K2 in uninfected cells. Uninfected cells expressing A56 and K2 exhibited resistance to fusing with A56 mutant Virus-infected cells, whereas expression of A56 or K2 alone induced little or no resistance, which fits with the need for both proteins to bind the EFC. Furthermore, transient or stable expression of A56/K2 interfered with Virus Entry and replication as determined by inhibition of early expression of a luciferase reporter gene, Virus production, and plaque formation. The specificity of this effect was demonstrated by restoring Entry after enzymatically removing a chimeric glycophosphatidylinositol-anchored A56/K2 or by binding a monoclonal antibody to A56. Importantly, the antibody disrupted the interaction between A56/K2 and the EFC without disrupting the A56-K2 interaction itself. Thus, we have shown that A56/K2 is sufficient to prevent Virus Entry and fusion as well as formation of syncytia through interaction with the EFC.