scholarly journals pH and Receptor Induced Conformational Changes-Implications Towards S1 Dissociation of SARS-CoV2 Spike Glycoprotein

2020 ◽  
Author(s):  
Jesu E. Castin ◽  
Daniel A. Gideon ◽  
Karthik S. Sudarsha ◽  
Sherlin A. Rosita
Keyword(s):  
Host Cell ◽  
Cell Fusion ◽  
Fusion Proteins ◽  
Proteolytic Enzymes ◽  
Host Cells ◽  
Viral Fusion ◽  
Health Crisis ◽  
S Protein ◽  
Viral Attachment ◽  
Cell Receptors

AbstractViruses, being obligate intracellular parasites, must first attach themselves and gain entry into host cells. Viral fusion machinery is the central player in the viral attachment process in almost every viral disease. Viruses have incorporated an array of efficient fusion proteins on their surfaces to bind efficiently to host cell receptors. They make use of the host proteolytic enzymes to rearrange their surface protein(s) into the form which facilitates their binding to host-cell membrane proteins and subsequently, fusion. This stage of viral entry is very critical and has many therapeutic implications. The current global pandemic of COVID-19 has sparked severe health crisis and economic shutdowns. SARS-CoV2, the etiological agent of the disease has led to millions of deaths and brought the scientific community together in an attempt to understand the mechanisms of SARS-CoV2 pathogenesis and mortality. Like other viral fusion machinery, CoV2 spike (S) glycoprotein- ‘The Demogorgon’ poses the same questions about viral-host cell fusion. The intermediate stages of S protein-mediated viral fusion are unclear owing to the lack of structural insights and concrete biochemical evidence. The mechanism of conformational transition is still unclear. S protein binding and fusion with host cell receptors, Eg., angiotensin-converting enzyme-2 (ACE2) is accompanied by cleavage of S1/S2 subunits. To track the key events of viral-host cell fusion, we have identified (in silico) that low pH-induced conformational change and ACE-2 binding events promote S1 dissociation. Deciphering key mechanistic insights of SARS-CoV2 fusion will further our understanding of other class-I fusion proteins

scholarly journals Development of a Novel High-Throughput Surrogate Assay to Measure HIV Envelope/CCR5/CD4-Mediated Viral/Cell Fusion Using BacMam Baculovirus Technology

2003 ◽  
Vol 8 (4) ◽  
pp. 463-470 ◽  
Author(s):  
Stephen Jenkinson ◽  
David C. Mc Coy ◽  
Sandy A. Kerner ◽  
Robert G. Ferris ◽  
Wendell K. Lawrence ◽  
...  
Keyword(s):  
Host Cell ◽  
Cell Fusion ◽  
High Throughput ◽  
Viral Envelope ◽  
Host Cells ◽  
Luciferase Reporter ◽  
Viral Fusion ◽  
Fusion Event ◽  
Surrogate Assay ◽  
Cell Cell

The initial event by which M-tropic HIV strains gain access to cells is via interaction of the viral envelope protein gp120 with the host cell CCR5 coreceptor and CD4. Inhibition of this event reduces viral fusion and entry into cells in vitro. The authors have employed BacMam baculovirus-mediated gene transduction to develop a cell/cell fusion assay that mimics the HIV viral/cell fusion process and allows high-throughput quantification of this fusion event. The assay design uses human osteosarcoma (HOS) cells stably transfected with cDNAs expressing CCR5, CD4, and long terminal repeat (LTR)-luciferase as the recipient host cell. An HEK-293 cell line transduced with BacMam viral constructs to express the viral proteins gp120, gp41, tat, and rev represents the virus. Interaction of gp120 with CCR5/CD4 results in the fusion of the 2 cells and transfer of tat to the HOS cell cytosol; tat, in turn, binds to the LTR region on the luciferase reporter and activates transcription, resulting in an increase in cellular luciferase activity. In conclusion, the cell/cell fusion assay developed has been demonstrated to be a robust and reproducible high-throughput surrogate assay that can be used to assess the effects of compounds on gp120/CCR5/CD4-mediated viral fusion into host cells.

scholarly journals Reciprocal Regulation of AKT and MAP Kinase Dictates Virus-Host Cell Fusion

2010 ◽  
Vol 84 (9) ◽  
pp. 4366-4382 ◽  
Author(s):  
Nishi R. Sharma ◽  
Prashant Mani ◽  
Neha Nandwani ◽  
Rajakishore Mishra ◽  
Ajay Rana ◽  
...  
Keyword(s):  
Host Cell ◽  
Cell Fusion ◽  
Sendai Virus ◽  
Host Cells ◽  
Mitogen Activated Protein Kinase ◽  
Viral Fusion ◽  
Reciprocal Regulation ◽  
Mapk Cascades ◽  
Mitogen Activated Protein ◽  
Syncytial Virus

ABSTRACT Viruses of the Paramyxoviridae family bind to their host cells by using hemagglutinin-neuraminidase (HN), which enhances fusion protein (F)-mediated membrane fusion. Although respiratory syncytial virus and parainfluenza virus 5 of this family are suggested to trigger host cell signaling during infection, the virus-induced intracellular signals dictating virus-cell fusion await elucidation. Using an F- or HN-F-containing reconstituted envelope of Sendai virus, another paramyxovirus, we revealed the role and regulation of AKT1 and Raf/MEK/ERK cascades during viral fusion with liver cells. Our observation that extracellular signal-regulated kinase (ERK) activation promotes viral fusion via ezrin-mediated cytoskeletal rearrangements, whereas AKT1 attenuates fusion by promoting phosphorylation of F protein, indicates a counteractive regulation of viral fusion by reciprocal activation of AKT1 and mitogen-activated protein kinase (MAPK) cascades, establishing a novel conceptual framework for a therapeutic strategy.

The Use of Lectins as Tools to Combat SARS-CoV-2

2021 ◽  
Vol 27 ◽  
Author(s):  
Daniela Martinez ◽  
Diego Amaral ◽  
David Markovitz ◽  
Luciano Pinto
Keyword(s):  
Viral Infection ◽  
Host Cells ◽  
Viral Fusion ◽  
Cell Receptors ◽  
First Case ◽  
Mannose Binding ◽  
New Treatments ◽  
Viral Surface

Background: in december 2019, china announced the first case of an infection caused by an, until then, unknown virus: sars-cov-2. since then, researchers have been looking for viable alternatives for the treatment and/or cure of viral infection. among the possible complementary solutions are lectins, and proteins that are reversibly bound to different carbohydrates. the spike protein, present on the viral surface, can interact with different cell receptors: ace2, cd147, and dc-signr. since lectins have an affinity for different carbohydrates, the binding with the glycosylated cell receptors represents a possibility of preventing the virus from binding to the receptors of host cells. Objective: in this review we discuss the main lectins that are possible candidates for use in the treatment of covid-19, highlighting those that have already demonstrated antiviral activity in vivo and in vitro, including mannose-binding lectin, griffithsin, banlec, and others. we also aim to discuss the possible mechanism of action of lectins, which appears to occur through the mediation of viral fusion in host cells, by binding of lectins to glycosylated receptors found in human cells and/or binding of these proteins with the spike glycoprotein, present in virus surface.moreover, we also discuss the use of lectins in clinical practice. Conclusion: Even with the development of effective vaccines, new cases of viral infection with the same virus, or new outbreaks with different viruses can occur; so, the development of new treatments should not be discarded. moreover, the discussions made in this work are relevant regarding the anti-viral properties of lectins.

Interfering with Host Proteases in SARS-CoV-2 Entry as a Promising Therapeutic Strategy

2021 ◽  
Vol 28 ◽  
Author(s):  
Patrick Müller ◽  
Hannah Maus ◽  
Stefan Josef Hammerschmidt ◽  
Philip Knaff ◽  
Volker Mailänder ◽  
...  
Keyword(s):  
Cathepsin L ◽  
Cell Entry ◽  
New Drugs ◽  
Host Cells ◽  
S Protein ◽  
Cell Receptors ◽  
Current State ◽  
Causative Drug ◽  
Transmembrane Serine Protease ◽  
Global Threat

: Due to its fast international spread and substantial mortality, the coronavirus disease COVID-19 evolved to a global threat. Since currently, there is no causative drug against this viral infection available, science is striving for new drugs and approaches to treat the new disease. Studies have shown that the cell entry of coronaviruses into host cells takes place through the binding of the viral spike (S) protein to cell receptors. Priming of the S protein occurs via hydrolysis by different host proteases. The inhibition of these proteases could impair the processing of the S protein, thereby affecting the interaction with the host-cell receptors and preventing virus cell entry. Hence, inhibition of these proteases could be a promising strategy for treatment against SARS-CoV-2. In this review, we discuss the current state of the art of developing inhibitors against the entry proteases furin, the transmembrane serine protease type-II (TMPRSS2), trypsin, and cathepsin L.

scholarly journals Suppression of a Fusion Defect by Second Site Mutations in the Ecotropic Murine Leukemia Virus Surface Protein

1999 ◽  
Vol 73 (6) ◽  
pp. 5034-5042 ◽  
Author(s):  
Tatiana Zavorotinskaya ◽  
Lorraine M. Albritton
Keyword(s):  
Host Cell ◽  
Cell Fusion ◽  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Surface Protein ◽  
Host Cells ◽  
Virus Surface ◽  
Fusion Defect ◽  
Murine Leukemia ◽  
Cell Cell

ABSTRACT Entry of ecotropic murine leukemia virus initiates when the envelope surface protein recognizes and binds to the virus receptor on host cells. The envelope transmembrane protein then mediates fusion of viral and host cell membranes and penetration into the cytoplasm. Using a genetic selection, we isolated an infectious retrovirus variant containing three changes in the surface protein—histidine 8 to arginine, glutamine 227 to arginine, and aspartate 243 to tyrosine. Single replacement of histidine 8 with arginine (H8R) resulted in almost complete loss of infectivity, even though the mutant envelope proteins were stable and efficiently incorporated into virions. Virions carrying H8R envelope were proficient at binding cells expressing receptor but failed to induce cell-cell fusion of XC cells, indicating that the histidine at position 8 plays an essential role in fusion during penetration of the host cell membrane. Thus, there is at least one domain in SU that is involved in fusion; the fusion functions do not reside exclusively in TM. In contrast, envelope with all three changes induced cell-cell fusion of XC cells and produced virions that were 10,000-fold more infectious than those containing only the H8R substitution, indicating that changes at positions 227 and 243 can suppress a fusion defect caused by loss of histidine 8 function. Moreover, the other two changes acted synergistically, indicating that both compensate for the loss of the same essential function of histidine 8. The ability of these changes to suppress this fusion defect might provide a means for overcoming postbinding defects found in targeted retroviral vectors for use in human gene therapy.

scholarly journals Molecular dynamics analysis of fast-spreading severe acute respiratory syndrome coronavirus 2 variants and their effects in the interaction with human angiotensin-converting enzyme 2

2021 ◽  
Author(s):  
Anacleto Silva de Souza ◽  
Vitor Martins de Freitas Amorim ◽  
Gabriela D. A. Guardia ◽  
Felipe R C dos Santos ◽  
Filipe F dos Santos ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Severe Acute Respiratory Syndrome ◽  
Host Cell ◽  
Proteolytic Enzymes ◽  
Severe Disease ◽  
Host Cells ◽  
Angiotensin Converting Enzyme 2 ◽  
Fast Spreading ◽  
Host Cell Factors ◽  
Dynamics Simulations

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is evolving with mutations in the Spike protein, especially in the receptor-binding domain (RBD). The failure of public health measures to contain the spread of the disease in many countries has given rise to novel viral variants with increased transmissibility. However, key questions about how quickly the variants can spread and whether they can cause a more severe disease remain unclear. Herein, we performed a structural investigation using molecular dynamics simulations and determined dissociation constant (KD) values using surface plasmon resonance (SPR) assays of three fast-spreading SARS-CoV-2 variants, Alpha, Beta and Gamma ones, as well as genetic factors in the host cells that may be related to the viral infection. Our results suggest that the SARS-CoV-2 variants facilitate their entry into the host cell by moderately increased binding affinities to the human ACE2 receptor, different torsions in hACE2 mediated by RBD variants, and an increased Spike exposure time to proteolytic enzymes. We also found that other host cell aspects, such as gene and isoform expression of key genes for the infection (ACE2, FURIN and TMPRSS2), may have few contributions to the SARS-CoV-2 variants infectivity. In summary, we concluded that a combination of viral and host cell factors allows SARS-CoV-2 variants to increase their abilities to spread faster than wild-type.

scholarly journals Viral Membrane Fusion and the Transmembrane Domain

Viruses ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 693 ◽  
Author(s):  
Chelsea T. Barrett ◽  
Rebecca Ellis Dutch
Keyword(s):  
Membrane Fusion ◽  
Host Cell ◽  
Fusion Proteins ◽  
Transmembrane Domain ◽  
Critical Role ◽  
Viral Fusion ◽  
Transmembrane Region ◽  
Host Cell Membrane ◽  
The Past ◽  
Viral Fusion Proteins

Initiation of host cell infection by an enveloped virus requires a viral-to-host cell membrane fusion event. This event is mediated by at least one viral transmembrane glycoprotein, termed the fusion protein, which is a key therapeutic target. Viral fusion proteins have been studied for decades, and numerous critical insights into their function have been elucidated. However, the transmembrane region remains one of the most poorly understood facets of these proteins. In the past ten years, the field has made significant advances in understanding the role of the membrane-spanning region of viral fusion proteins. We summarize developments made in the past decade that have contributed to the understanding of the transmembrane region of viral fusion proteins, highlighting not only their critical role in the membrane fusion process, but further demonstrating their involvement in several aspects of the viral lifecycle.

scholarly journals Nonprofessional Phagocytic Cell Receptors Involved inStaphylococcus aureusInternalization

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Nayeli Alva-Murillo ◽  
Joel Edmundo López-Meza ◽  
Alejandra Ochoa-Zarzosa
Keyword(s):  
Staphylococcus Aureus ◽  
Host Cell ◽  
Soft Tissues ◽  
Scavenger Receptor ◽  
Host Cells ◽  
Phagocytic Cell ◽  
Phagocytic Cells ◽  
Cell Receptors ◽  
Life Threatening ◽  
Bacterial Effectors

Staphylococcus aureusis a successful human and animal pathogen. The majority of infections caused by this pathogen are life threatening, primarily becauseS. aureushas developed multiple evasion strategies, possesses intracellular persistence for long periods, and targets the skin and soft tissues. Therefore, it is very important to understand the mechanisms employed byS. aureusto colonize and proliferate in these cells. The aim of this review is to describe the recent discoveries concerning the host receptors of nonprofessional phagocytes involved inS. aureusinternalization. Most of the knowledge related to the interaction ofS. aureuswith its host cells has been described in professional phagocytic cells such as macrophages. Here, we showed that in nonprofessional phagocytes theα5β1 integrin host receptor, chaperons, and the scavenger receptor CD36 are the main receptors employed duringS. aureusinternalization. The characterization and identification of new bacterial effectors and the host cell receptors involved will undoubtedly lead to new discoveries with beneficial purposes.

scholarly journals Localization of the Hypothetical Protein Cpn0797 in the Cytoplasm of Chlamydia pneumoniae-Infected Host Cells

2006 ◽  
Vol 74 (11) ◽  
pp. 6479-6486 ◽  
Author(s):  
Feng Dong ◽  
Rhonda Flores ◽  
Ding Chen ◽  
Jianhua Luo ◽  
Youmin Zhong ◽  
...  
Keyword(s):  
Host Cell ◽  
Fusion Proteins ◽  
Chlamydia Pneumoniae ◽  
Hypothetical Protein ◽  
Host Cells ◽  
Infected Host ◽  
Reading Frame ◽  
The Third ◽  
Cell Cytosol ◽  
Host Cell Cytosol

ABSTRACT Using antibodies raised with chlamydial fusion proteins, we have localized a protein encoded by the hypothetical open reading frame Cpn0797 in the cytoplasm of Chlamydia pneumoniae-infected host cells. The anti-Cpn0797 antibodies specifically recognized Cpn0797 protein without cross-reacting with either CPAFcp or Cpn0796, the only two proteins known to be secreted into the host cell cytosol by C. pneumoniae organisms. Thus, Cpn0797 represents the third C. pneumoniae protein secreted into the host cell cytosol experimentally identified so far.

scholarly journals Deletion of ER-retention motif on SARS-CoV-2 spike protein reduces cell hybrid during cell–cell fusion

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Xuening Wang ◽  
Chih-Hsiung Chen ◽  
Saiaditya Badeti ◽  
Jong Hyun Cho ◽  
Alireza Naghizadeh ◽  
...  
Keyword(s):  
Cell Fusion ◽  
Cell Lines ◽  
Cell Hybrid ◽  
Host Cells ◽  
Spike Protein ◽  
Expression Vectors ◽  
S Protein ◽  
Er Retention ◽  
Syncytia Formation ◽  
Cell Cell

Abstract Background The novel SARS-CoV-2 has quickly become a global pandemic since the first reported case in December 2019, with the virus infecting millions of people to date. The spike (S) protein of the SARS-CoV-2 virus plays a key role in binding to angiotensin-converting enzyme 2 (ACE2), a host cell receptor for SARS-CoV-2. S proteins that are expressed on the cell membrane can initiate receptor-dependent syncytia formation that is associated with extensive tissue damage. Formation of syncytia have been previously observed in cells infected with various other viruses (e.g., HIV, Ebola, Influenza, and Herpesviruses). However, this phenomenon is not well documented and the mechanisms regulating the formation of the syncytia by SARS-CoV-2 are not fully understood. Results In this study, we investigated the possibility that cell fusion events mediated by the S protein of SARS-CoV-2 and ACE2 interaction can occur in different human cell lines that mimic different tissue origins. These cell lines were transduced with either wild-type (WT-S) S protein or a mutated variant where the ER-retention motif was removed (Δ19-S), as well as human ACE2 expression vectors. Different co-culture combinations of spike-expressing 293T, A549, K562, and SK-Hep1 cells with hACE2-expressing cells revealed cell hybrid fusion. However, only certain cells expressing S protein can form syncytial structures as this phenomenon cannot be observed in all co-culture combinations. Thus, SARS-CoV-2 mediated cell–cell fusion represents a cell type-dependent process which might rely on a different set of parameters. Recently, the Δ19-S variant is being widely used to increase SARS-CoV-2 pseudovirus production for in vitro assays. Comparison of cell fusion occurring via Δ19-S expressing cells shows defective nuclear fusion and syncytia formation compared to WT-S. Conclusions This distinction between the Δ19-S variant and WT-S protein may have downstream implications for studies that utilize pseudovirus-based entry assays. Additionally, this study suggest that spike protein expressed by vaccines may affect different ACE2-expressing host cells after SARS-CoV-2 vaccine administration. The long-term effects of these vaccines should be monitored carefully. Δ19-S mRNA may represent a safer mRNA vaccine design in the future.

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