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1.
Viruses ; 13(12)2021 12 06.
Article in English | MEDLINE | ID: covidwho-1555020

ABSTRACT

Porcine deltacoronavirus (PDCoV) is a novel coronavirus that causes diarrhea in nursing piglets. Studies showed that PDCoV uses porcine aminopeptidase N (pAPN) as an entry receptor, but the infection of pAPN-knockout cells or pigs with PDCoV revealed that pAPN might be not a critical functional receptor, implying there exists an unidentified receptor involved in PDCoV infection. Herein, we report that sialic acid (SA) can act as an attachment receptor for PDCoV invasion and facilitate its infection. We first demonstrated that the carbohydrates destroyed on the cell membrane using NaIO4 can alleviate the susceptibility of cells to PDCoV. Further study showed that the removal of SA, a typical cell-surface carbohydrate, could influence the PDCoV infectivity to the cells significantly, suggesting that SA was involved in the infection. The results of plaque assay and Western blotting revealed that SA promoted PDCoV infection by increasing the number of viruses binding to SA on the cell surface during the adsorption phase, which was also confirmed by atomic force microscopy at the microscopic level. In in vivo experiments, we found that the distribution levels of PDCoV and SA were closely relevant in the swine intestine, which contains huge amount of trypsin. We further confirmed that SA-binding capacity to PDCoV is related to the pre-treatment of PDCoV with trypsin. In conclusion, SA is a novel attachment receptor for PDCoV infection to enhance its attachment to cells, which is dependent on the pre-treatment of trypsin on PDCoV. This study paves the way for dissecting the mechanisms of PDCoV-host interactions and provides new strategies to control PDCoV infection.


Subject(s)
Deltacoronavirus/physiology , N-Acetylneuraminic Acid/metabolism , Receptors, Virus/metabolism , Trypsin/metabolism , Virus Attachment , Animals , Carbohydrates , Cell Line , Cell Membrane/metabolism , Cell Membrane/virology , Coronavirus Infections/veterinary , Coronavirus Infections/virology , Deltacoronavirus/drug effects , Host-Pathogen Interactions , Intestines/metabolism , Intestines/virology , Periodic Acid/pharmacology , Swine , Swine Diseases/virology , Trypsin/pharmacology
2.
Nat Commun ; 12(1): 4502, 2021 07 23.
Article in English | MEDLINE | ID: covidwho-1550282

ABSTRACT

Cells in many tissues, such as bone, muscle, and placenta, fuse into syncytia to acquire new functions and transcriptional programs. While it is known that fused cells are specialized, it is unclear whether cell-fusion itself contributes to programmatic-changes that generate the new cellular state. Here, we address this by employing a fusogen-mediated, cell-fusion system to create syncytia from undifferentiated cells. RNA-Seq analysis reveals VSV-G-induced cell fusion precedes transcriptional changes. To gain mechanistic insights, we measure the plasma membrane surface area after cell-fusion and observe it diminishes through increases in endocytosis. Consequently, glucose transporters internalize, and cytoplasmic glucose and ATP transiently decrease. This reduced energetic state activates AMPK, which inhibits YAP1, causing transcriptional-reprogramming and cell-cycle arrest. Impairing either endocytosis or AMPK activity prevents YAP1 inhibition and cell-cycle arrest after fusion. Together, these data demonstrate plasma membrane diminishment upon cell-fusion causes transient nutrient stress that may promote transcriptional-reprogramming independent from extrinsic cues.


Subject(s)
Adaptor Proteins, Signal Transducing/metabolism , Cell Membrane/metabolism , Cell Nucleus/metabolism , Membrane Glycoproteins/metabolism , Transcription Factors/metabolism , Transcription, Genetic/genetics , Viral Envelope Proteins/metabolism , AMP-Activated Protein Kinases/genetics , AMP-Activated Protein Kinases/metabolism , Adaptor Proteins, Signal Transducing/genetics , Animals , Biological Transport , Cell Fusion , Cell Line , Cell Line, Tumor , Cells, Cultured , Giant Cells/metabolism , HEK293 Cells , Humans , Membrane Glycoproteins/genetics , Mice , RNA-Seq/methods , Signal Transduction/genetics , Transcription Factors/genetics , Viral Envelope Proteins/genetics
3.
Pharmacol Res ; 172: 105820, 2021 10.
Article in English | MEDLINE | ID: covidwho-1531713

ABSTRACT

Coronavirus Disease 2019 (COVID-19) is caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), which enter the host cells through the interaction between its receptor binding domain (RBD) of spike glycoprotein with angiotensin-converting enzyme 2 (ACE2) receptor on the plasma membrane of host cell. Neutralizing antibodies and peptide binders of RBD can block viral infection, however, the concern of accessibility and affordability of viral infection inhibitors has been raised. Here, we report the identification of natural compounds as potential SARS-CoV-2 entry inhibitors using the molecular docking-based virtual screening coupled with bilayer interferometry (BLI). From a library of 1871 natural compounds, epigallocatechin gallate (EGCG), 20(R)-ginsenoside Rg3 (RRg3), 20(S)-ginsenoside Rg3 (SRg3), isobavachalcone (Ibvc), isochlorogenic A (IscA) and bakuchiol (Bkc) effectively inhibited pseudovirus entry at concentrations up to 100 µM. Among these compounds, four compounds, EGCG, Ibvc, salvianolic acid A (SalA), and isoliensinine (Isl), were effective in inhibiting SARS-CoV-2-induced cytopathic effect and plaque formation in Vero E6 cells. The EGCG was further validated with no observable animal toxicity and certain antiviral effect against SARS-CoV-2 pseudovirus mutants (D614G, N501Y, N439K & Y453F). Interestingly, EGCG, Bkc and Ibvc bind to ACE2 receptor in BLI assay, suggesting a dual binding to RBD and ACE2. Current findings shed some insight into identifications and validations of SARS-CoV-2 entry inhibitors from natural compounds.


Subject(s)
Angiotensin-Converting Enzyme 2/antagonists & inhibitors , Antiviral Agents/chemistry , Biological Products/chemistry , COVID-19/drug therapy , Enzyme Inhibitors/chemistry , SARS-CoV-2/enzymology , Spike Glycoprotein, Coronavirus/metabolism , Animals , Antiviral Agents/pharmacology , Binding, Competitive , Biological Products/pharmacology , Catechin/analogs & derivatives , Catechin/pharmacology , Cell Membrane/metabolism , Cell Membrane/ultrastructure , Chalcones/pharmacology , Chlorogenic Acid/analogs & derivatives , Chlorogenic Acid/pharmacology , Dose-Response Relationship, Drug , Drug Evaluation, Preclinical , Enzyme Inhibitors/pharmacology , Ginsenosides/pharmacology , Humans , Interferometry , Mice, Inbred C57BL , Molecular Dynamics Simulation , Phenols/pharmacology , Protein Binding
4.
J Virol ; 95(17): e0080721, 2021 08 10.
Article in English | MEDLINE | ID: covidwho-1486516

ABSTRACT

The membrane fusion between the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and host cells is essential for the initial step of infection; therefore, the host cell membrane components, including sphingolipids, influence the viral infection. We assessed several inhibitors of the enzymes pertaining to sphingolipid metabolism, against SARS-CoV-2 spike protein (S)-mediated cell-cell fusion and viral infection. N-(4-Hydroxyphenyl) retinamide (4-HPR), an inhibitor of dihydroceramide Δ4-desaturase 1 (DES1), suppressed cell-cell fusion and viral infection. The analysis of sphingolipid levels revealed that the inhibition efficiencies of cell-cell fusion and viral infection in 4-HPR-treated cells were consistent with an increased ratio of saturated sphinganine-based lipids to total sphingolipids. We investigated the relationship of DES1 with the inhibition efficiencies of cell-cell fusion. The changes in the sphingolipid profile induced by 4-HPR were mitigated by the supplementation with exogenous cell-permeative ceramide; however, the reduced cell-cell fusion could not be reversed. The efficiency of cell-cell fusion in DES1 knockout (KO) cells was at a level comparable to that in wild-type (WT) cells; however, the ratio of saturated sphinganine-based lipids to the total sphingolipids was higher in DES1 KO cells than in WT cells. 4-HPR reduced cell membrane fluidity without any significant effects on the expression or localization of angiotensin-converting enzyme 2, the SARS-CoV-2 receptor. Therefore, 4-HPR suppresses SARS-CoV-2 S-mediated membrane fusion through a DES1-independent mechanism, and this decrease in membrane fluidity induced by 4-HPR could be the major cause for the inhibition of SARS-CoV-2 infection. IMPORTANCE Sphingolipids could play an important role in SARS-CoV-2 S-mediated membrane fusion with host cells. We studied the cell-cell fusion using SARS-CoV-2 S-expressing cells and sphingolipid-manipulated target cells, with an inhibitor of the sphingolipid metabolism. 4-HPR (also known as fenretinide) is an inhibitor of DES1, and it exhibits antitumor activity and suppresses cell-cell fusion and viral infection. 4-HPR suppresses membrane fusion through a decrease in membrane fluidity, which could possibly be the cause for the inhibition of SARS-CoV-2 infection. There is accumulating clinical data on the safety of 4-HPR. Therefore, it could be a potential candidate drug against COVID-19.


Subject(s)
Cell Membrane/metabolism , Fenretinide/pharmacology , Membrane Fluidity/drug effects , Oxidoreductases/metabolism , SARS-CoV-2/metabolism , Spike Glycoprotein, Coronavirus/metabolism , Cell Fusion , Cell Membrane/genetics , Gene Knockout Techniques , HEK293 Cells , Humans , Membrane Fluidity/genetics , Oxidoreductases/deficiency , SARS-CoV-2/genetics , Spike Glycoprotein, Coronavirus/genetics
5.
ACS Chem Biol ; 16(5): 844-856, 2021 05 21.
Article in English | MEDLINE | ID: covidwho-1457790

ABSTRACT

Interferon-induced transmembrane proteins (IFITMs) are S-palmitoylated proteins in vertebrates that restrict a diverse range of viruses. S-palmitoylated IFITM3 in particular engages incoming virus particles, prevents their cytoplasmic entry, and accelerates their lysosomal clearance by host cells. However, how S-palmitoylation modulates the structure and biophysical characteristics of IFITM3 to promote its antiviral activity remains unclear. To investigate how site-specific S-palmitoylation controls IFITM3 antiviral activity, we employed computational, chemical, and biophysical approaches to demonstrate that site-specific lipidation of cysteine 72 enhances the antiviral activity of IFITM3 by modulating its conformation and interaction with lipid membranes. Collectively, our results demonstrate that site-specific S-palmitoylation of IFITM3 directly alters its biophysical properties and activity in cells to prevent virus infection.


Subject(s)
Antiviral Agents/chemistry , Cell Membrane/metabolism , Interferons/chemistry , Lipids/chemistry , Membrane Proteins/metabolism , RNA-Binding Proteins/metabolism , Amino Acid Sequence , Antiviral Agents/pharmacology , Binding Sites , Cell Membrane/ultrastructure , Computational Biology , Drug Design , Humans , Interferons/pharmacology , Lipoylation , Lysosomes/metabolism , Molecular Dynamics Simulation , Protein Binding , Protein Conformation , Signal Transduction
6.
Biochemistry ; 60(40): 2978-2986, 2021 10 12.
Article in English | MEDLINE | ID: covidwho-1440443

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.


Subject(s)
Cell Membrane/metabolism , Membrane Fusion/physiology , Models, Biological , Spike Glycoprotein, Coronavirus/chemistry , Spike Glycoprotein, Coronavirus/metabolism , Amino Acid Sequence , COVID-19/genetics , COVID-19/metabolism , Cell Membrane/genetics , Humans , Protein Binding/physiology , SARS-CoV-2/chemistry , SARS-CoV-2/genetics , SARS-CoV-2/metabolism , Spike Glycoprotein, Coronavirus/genetics
7.
J Med Virol ; 94(1): 342-348, 2022 01.
Article in English | MEDLINE | ID: covidwho-1437056

ABSTRACT

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of the ongoing coronavirus disease 2019 (COVID-19) pandemic. The S protein is the key viral protein for associating with ACE2, the receptor for SARS-CoV-2. There are many kinds of posttranslational modifications in S protein. However, the detailed mechanism of palmitoylation of SARS-CoV-2 S remains to be elucidated. In our current study, we characterized the palmitoylation of SARS-CoV-2 S. Both the C15 and cytoplasmic tail of SARS-CoV-2 S were palmitoylated. Fatty acid synthase inhibitor C75 and zinc finger DHHC domain-containing palmitoyltransferase (ZDHHC) inhibitor 2-BP reduced the palmitoylation of S. Interestingly, palmitoylation of SARS-CoV-2 S was not required for plasma membrane targeting of S but was critical for S-mediated syncytia formation and SARS-CoV-2 pseudovirus particle entry. Overexpression of ZDHHC2, ZDHHC3, ZDHHC4, ZDHHC5, ZDHHC8, ZDHHC9, ZDHHC11, ZDHHC14, ZDHHC16, ZDHHC19, and ZDHHC20 promoted the palmitoylation of S. Furthermore, those ZDHHCs were identified to associate with SARS-CoV-2 S. Our study not only reveals the mechanism of S palmitoylation but also will shed important light into the role of S palmitoylation in syncytia formation and virus entry.


Subject(s)
Cell Membrane/metabolism , Giant Cells/metabolism , Lipoylation/physiology , Spike Glycoprotein, Coronavirus/metabolism , Virus Internalization , 4-Butyrolactone/analogs & derivatives , 4-Butyrolactone/pharmacology , Acyltransferases/antagonists & inhibitors , COVID-19/pathology , Cell Line , HEK293 Cells , Humans , Protein Processing, Post-Translational/physiology
8.
Int J Med Sci ; 18(15): 3533-3543, 2021.
Article in English | MEDLINE | ID: covidwho-1409698

ABSTRACT

Importance: Despite the availability of a vaccine against the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), humans will have to live with this virus and the after-effects of the coronavirus disease 2019 (COVID-19) infection for a long time. Cholesterol plays an important role in the infection and prognosis of SARS-CoV-2, and the study of its mechanism is of great significance not only for the treatment of COVID-19 but also for research on generic antiviral drugs. Observations: Cholesterol promotes the development of atherosclerosis by activating NLR family pyrin domain containing 3 (NLRP3), and the resulting inflammatory environment indirectly contributes to COVID-19 infection and subsequent deterioration. In in vitro studies, membrane cholesterol increased the number of viral entry sites on the host cell membrane and the number of angiotensin-converting enzyme 2 (ACE2) receptors in the membrane fusion site. Previous studies have shown that the fusion protein of the virus interacts with cholesterol, and the spike protein of SARS-CoV-2 also requires cholesterol to enter the host cells. Cholesterol in blood interacts with the spike protein to promote the entry of spike cells, wherein the scavenger receptor class B type 1 (SR-B1) plays an important role. Because of the cardiovascular protective effects of lipid-lowering therapy and the additional anti-inflammatory effects of lipid-lowering drugs, it is currently recommended to continue lipid-lowering therapy for patients with COVID-19, but the safety of extremely low LDL-C is questionable. Conclusions and Relevance: Cholesterol can indirectly increase the susceptibility of patients to SARS-CoV-2 and increase the risk of death from COVID-19, which are mediated by NLRP3 and atherosclerotic plaques, respectively. Cholesterol present in the host cell membrane, virus, and blood may also directly participate in the virus cell entry process, but the specific mechanism still needs further study. Patients with COVID-19 are recommended to continue lipid-lowering therapy.


Subject(s)
COVID-19/complications , Hypercholesterolemia/complications , Angiotensin-Converting Enzyme 2/metabolism , Antiviral Agents/therapeutic use , Atherosclerosis/physiopathology , COVID-19/diagnosis , COVID-19/drug therapy , COVID-19/therapy , Cell Membrane/metabolism , Cholesterol, HDL/metabolism , Cholesterol, LDL/metabolism , Endocytosis , Humans , Hypercholesterolemia/diagnosis , Hypercholesterolemia/therapy , Inflammation , Macrophages/metabolism , NLR Family, Pyrin Domain-Containing 3 Protein/blood , Prognosis , SARS-CoV-2 , Scavenger Receptors, Class B/metabolism
9.
Nat Commun ; 12(1): 5333, 2021 09 09.
Article in English | MEDLINE | ID: covidwho-1402067

ABSTRACT

The Spike (S) protein of SARS-CoV-2 binds ACE2 to direct fusion with host cells. S comprises a large external domain, a transmembrane domain, and a short cytoplasmic tail. Understanding the intracellular trafficking of S is relevant to SARS-CoV-2 infection, and to vaccines expressing full-length S from mRNA or adenovirus vectors. Here we report a proteomic screen for cellular factors that interact with the cytoplasmic tail of S. We confirm interactions with the COPI and COPII vesicle coats, ERM family actin regulators, and the WIPI3 autophagy component. The COPII binding site promotes exit from the endoplasmic reticulum, and although binding to COPI should retain S in the early Golgi where viral budding occurs, there is a suboptimal histidine residue in the recognition motif. As a result, S leaks to the surface where it accumulates and can direct the formation of multinucleate syncytia. Thus, the trafficking signals in the tail of S indicate that syncytia play a role in the SARS-CoV-2 lifecycle.


Subject(s)
COVID-19/metabolism , Cell Membrane/metabolism , Giant Cells/metabolism , SARS-CoV-2/metabolism , Spike Glycoprotein, Coronavirus/metabolism , Angiotensin-Converting Enzyme 2/metabolism , Animals , COP-Coated Vesicles/metabolism , Chlorocebus aethiops , Endoplasmic Reticulum/metabolism , Golgi Apparatus/metabolism , HEK293 Cells , Humans , Protein Binding , Protein Domains , Proteomics , Vero Cells , Virus Assembly/genetics
10.
J Am Chem Soc ; 143(23): 8543-8546, 2021 06 16.
Article in English | MEDLINE | ID: covidwho-1387162

ABSTRACT

The S protein of SARS-CoV-2 is a type I membrane protein that mediates membrane fusion and viral entry. A vast amount of structural information is available for the ectodomain of S, a primary target by the host immune system, but much less is known regarding its transmembrane domain (TMD) and its membrane-proximal regions. Here, we determined the NMR structure of the S protein TMD in bicelles that closely mimic a lipid bilayer. The TMD structure is a transmembrane α-helix (TMH) trimer that assembles spontaneously in a membrane. The trimer structure shows an extensive hydrophobic core along the 3-fold axis that resembles that of a trimeric leucine/isoleucine zipper, but with tetrad, not heptad, repeats. The trimeric core is strong in bicelles, resisting hydrogen-deuterium exchange for weeks. Although highly stable, structural guided mutagenesis identified single mutations that can completely dissociate the TMD trimer. Multiple studies have shown that the membrane anchors of viral fusion proteins can form highly specific oligomers, but the exact function of these oligomers remains unclear. Our findings should guide future experiments to address the above question for SARS coronaviruses.


Subject(s)
Cell Membrane/metabolism , Hydrophobic and Hydrophilic Interactions , Protein Multimerization , Spike Glycoprotein, Coronavirus/chemistry , Models, Molecular , Protein Structure, Quaternary , Spike Glycoprotein, Coronavirus/metabolism
11.
J Mol Biol ; 433(10): 166946, 2021 05 14.
Article in English | MEDLINE | ID: covidwho-1386061

ABSTRACT

Coronaviruses are a major infectious disease threat, and include the zoonotic-origin human pathogens SARS-CoV-2, SARS-CoV, and MERS-CoV (SARS-2, SARS-1, and MERS). Entry of coronaviruses into host cells is mediated by the spike (S) protein. In our previous ESR studies, the local membrane ordering effect of the fusion peptide (FP) of various viral glycoproteins including the S of SARS-1 and MERS has been consistently observed. We previously determined that the sequence immediately downstream from the S2' cleavage site is the bona fide SARS-1 FP. In this study, we used sequence alignment to identify the SARS-2 FP, and studied its membrane ordering effect. Although there are only three residue differences, SARS-2 FP induces even greater membrane ordering than SARS-1 FP, possibly due to its greater hydrophobicity. This may be a reason that SARS-2 is better able to infect host cells. In addition, the membrane binding enthalpy for SARS-2 is greater. Both the membrane ordering of SARS-2 and SARS-1 FPs are dependent on Ca2+, but that of SARS-2 shows a greater response to the presence of Ca2+. Both FPs bind two Ca2+ ions as does SARS-1 FP, but the two Ca2+ binding sites of SARS-2 exhibit greater cooperativity. This Ca2+ dependence by the SARS-2 FP is very ion-specific. These results show that Ca2+ is an important regulator that interacts with the SARS-2 FP and thus plays a significant role in SARS-2 viral entry. This could lead to therapeutic solutions that either target the FP-calcium interaction or block the Ca2+ channel.


Subject(s)
Calcium/metabolism , Cell Membrane/metabolism , SARS Virus/metabolism , SARS-CoV-2/metabolism , Spike Glycoprotein, Coronavirus/metabolism , Viral Fusion Proteins/metabolism , Amino Acid Sequence , Binding Sites , Calcium/pharmacology , Calorimetry , Cell Membrane/drug effects , Cell Membrane/virology , Hydrogen-Ion Concentration , Hydrophobic and Hydrophilic Interactions , SARS Virus/drug effects , SARS-CoV-2/drug effects , Spike Glycoprotein, Coronavirus/chemistry , Spike Glycoprotein, Coronavirus/genetics , Thermodynamics , Viral Fusion Proteins/chemistry , Viral Fusion Proteins/genetics , Virus Internalization/drug effects
13.
Int J Mol Sci ; 21(24)2020 Dec 17.
Article in English | MEDLINE | ID: covidwho-1383876

ABSTRACT

Cell-cell fusion between eukaryotic cells is a general process involved in many physiological and pathological conditions, including infections by bacteria, parasites, and viruses. As obligate intracellular pathogens, viruses use intracellular machineries and pathways for efficient replication in their host target cells. Interestingly, certain viruses, and, more especially, enveloped viruses belonging to different viral families and including human pathogens, can mediate cell-cell fusion between infected cells and neighboring non-infected cells. Depending of the cellular environment and tissue organization, this virus-mediated cell-cell fusion leads to the merge of membrane and cytoplasm contents and formation of multinucleated cells, also called syncytia, that can express high amount of viral antigens in tissues and organs of infected hosts. This ability of some viruses to trigger cell-cell fusion between infected cells as virus-donor cells and surrounding non-infected target cells is mainly related to virus-encoded fusion proteins, known as viral fusogens displaying high fusogenic properties, and expressed at the cell surface of the virus-donor cells. Virus-induced cell-cell fusion is then mediated by interactions of these viral fusion proteins with surface molecules or receptors involved in virus entry and expressed on neighboring non-infected cells. Thus, the goal of this review is to give an overview of the different animal virus families, with a more special focus on human pathogens, that can trigger cell-cell fusion.


Subject(s)
Cell Fusion , Cell Membrane/metabolism , Membrane Fusion , Viral Fusion Proteins/metabolism , Virus Internalization , Viruses/metabolism , Animals , Humans , Viruses/isolation & purification
14.
J Virol ; 95(17): e0080721, 2021 08 10.
Article in English | MEDLINE | ID: covidwho-1381151

ABSTRACT

The membrane fusion between the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and host cells is essential for the initial step of infection; therefore, the host cell membrane components, including sphingolipids, influence the viral infection. We assessed several inhibitors of the enzymes pertaining to sphingolipid metabolism, against SARS-CoV-2 spike protein (S)-mediated cell-cell fusion and viral infection. N-(4-Hydroxyphenyl) retinamide (4-HPR), an inhibitor of dihydroceramide Δ4-desaturase 1 (DES1), suppressed cell-cell fusion and viral infection. The analysis of sphingolipid levels revealed that the inhibition efficiencies of cell-cell fusion and viral infection in 4-HPR-treated cells were consistent with an increased ratio of saturated sphinganine-based lipids to total sphingolipids. We investigated the relationship of DES1 with the inhibition efficiencies of cell-cell fusion. The changes in the sphingolipid profile induced by 4-HPR were mitigated by the supplementation with exogenous cell-permeative ceramide; however, the reduced cell-cell fusion could not be reversed. The efficiency of cell-cell fusion in DES1 knockout (KO) cells was at a level comparable to that in wild-type (WT) cells; however, the ratio of saturated sphinganine-based lipids to the total sphingolipids was higher in DES1 KO cells than in WT cells. 4-HPR reduced cell membrane fluidity without any significant effects on the expression or localization of angiotensin-converting enzyme 2, the SARS-CoV-2 receptor. Therefore, 4-HPR suppresses SARS-CoV-2 S-mediated membrane fusion through a DES1-independent mechanism, and this decrease in membrane fluidity induced by 4-HPR could be the major cause for the inhibition of SARS-CoV-2 infection. IMPORTANCE Sphingolipids could play an important role in SARS-CoV-2 S-mediated membrane fusion with host cells. We studied the cell-cell fusion using SARS-CoV-2 S-expressing cells and sphingolipid-manipulated target cells, with an inhibitor of the sphingolipid metabolism. 4-HPR (also known as fenretinide) is an inhibitor of DES1, and it exhibits antitumor activity and suppresses cell-cell fusion and viral infection. 4-HPR suppresses membrane fusion through a decrease in membrane fluidity, which could possibly be the cause for the inhibition of SARS-CoV-2 infection. There is accumulating clinical data on the safety of 4-HPR. Therefore, it could be a potential candidate drug against COVID-19.


Subject(s)
Cell Membrane/metabolism , Fenretinide/pharmacology , Membrane Fluidity/drug effects , Oxidoreductases/metabolism , SARS-CoV-2/metabolism , Spike Glycoprotein, Coronavirus/metabolism , Cell Fusion , Cell Membrane/genetics , Gene Knockout Techniques , HEK293 Cells , Humans , Membrane Fluidity/genetics , Oxidoreductases/deficiency , SARS-CoV-2/genetics , Spike Glycoprotein, Coronavirus/genetics
15.
J Virol ; 95(17): e0080721, 2021 08 10.
Article in English | MEDLINE | ID: covidwho-1350004

ABSTRACT

The membrane fusion between the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and host cells is essential for the initial step of infection; therefore, the host cell membrane components, including sphingolipids, influence the viral infection. We assessed several inhibitors of the enzymes pertaining to sphingolipid metabolism, against SARS-CoV-2 spike protein (S)-mediated cell-cell fusion and viral infection. N-(4-Hydroxyphenyl) retinamide (4-HPR), an inhibitor of dihydroceramide Δ4-desaturase 1 (DES1), suppressed cell-cell fusion and viral infection. The analysis of sphingolipid levels revealed that the inhibition efficiencies of cell-cell fusion and viral infection in 4-HPR-treated cells were consistent with an increased ratio of saturated sphinganine-based lipids to total sphingolipids. We investigated the relationship of DES1 with the inhibition efficiencies of cell-cell fusion. The changes in the sphingolipid profile induced by 4-HPR were mitigated by the supplementation with exogenous cell-permeative ceramide; however, the reduced cell-cell fusion could not be reversed. The efficiency of cell-cell fusion in DES1 knockout (KO) cells was at a level comparable to that in wild-type (WT) cells; however, the ratio of saturated sphinganine-based lipids to the total sphingolipids was higher in DES1 KO cells than in WT cells. 4-HPR reduced cell membrane fluidity without any significant effects on the expression or localization of angiotensin-converting enzyme 2, the SARS-CoV-2 receptor. Therefore, 4-HPR suppresses SARS-CoV-2 S-mediated membrane fusion through a DES1-independent mechanism, and this decrease in membrane fluidity induced by 4-HPR could be the major cause for the inhibition of SARS-CoV-2 infection. IMPORTANCE Sphingolipids could play an important role in SARS-CoV-2 S-mediated membrane fusion with host cells. We studied the cell-cell fusion using SARS-CoV-2 S-expressing cells and sphingolipid-manipulated target cells, with an inhibitor of the sphingolipid metabolism. 4-HPR (also known as fenretinide) is an inhibitor of DES1, and it exhibits antitumor activity and suppresses cell-cell fusion and viral infection. 4-HPR suppresses membrane fusion through a decrease in membrane fluidity, which could possibly be the cause for the inhibition of SARS-CoV-2 infection. There is accumulating clinical data on the safety of 4-HPR. Therefore, it could be a potential candidate drug against COVID-19.


Subject(s)
Cell Membrane/metabolism , Fenretinide/pharmacology , Membrane Fluidity/drug effects , Oxidoreductases/metabolism , SARS-CoV-2/metabolism , Spike Glycoprotein, Coronavirus/metabolism , Cell Fusion , Cell Membrane/genetics , Gene Knockout Techniques , HEK293 Cells , Humans , Membrane Fluidity/genetics , Oxidoreductases/deficiency , SARS-CoV-2/genetics , Spike Glycoprotein, Coronavirus/genetics
16.
Biochimie ; 179: 229-236, 2020 Dec.
Article in English | MEDLINE | ID: covidwho-1326922

ABSTRACT

The ongoing pandemic of COVID-19 (Coronavirus Disease-2019), a respiratory disease caused by the novel coronavirus strain, SARS-CoV-2, has affected more than 42 million people already, with more than one million deaths worldwide (as of October 25, 2020). We are in urgent need of therapeutic interventions that target the host-virus interface, which requires a molecular understanding of the SARS-CoV-2 life-cycle. Like other positive-sense RNA viruses, coronaviruses remodel intracellular membranes to form specialized viral replication compartments, including double-membrane vesicles (DMVs), where viral RNA genome replication takes place. Here we review the current knowledge of the structure, lipid composition, function, and biogenesis of coronavirus-induced DMVs, highlighting the druggable viral and cellular factors that are involved in the formation and function of DMVs.


Subject(s)
Cell Membrane/metabolism , Coronavirus/physiology , Host Microbial Interactions , Virus Replication , Cell Membrane/virology , Humans , Molecular Targeted Therapy
17.
Nat Cell Biol ; 23(8): 846-858, 2021 08.
Article in English | MEDLINE | ID: covidwho-1309445

ABSTRACT

The integral membrane protein ATG9A plays a key role in autophagy. It displays a broad intracellular distribution and is present in numerous compartments, including the plasma membrane (PM). The reasons for the distribution of ATG9A to the PM and its role at the PM are not understood. Here, we show that ATG9A organizes, in concert with IQGAP1, components of the ESCRT system and uncover cooperation between ATG9A, IQGAP1 and ESCRTs in protection from PM damage. ESCRTs and ATG9A phenocopied each other in protection against PM injury. ATG9A knockouts sensitized the PM to permeabilization by a broad spectrum of microbial and endogenous agents, including gasdermin, MLKL and the MLKL-like action of coronavirus ORF3a. Thus, ATG9A engages IQGAP1 and the ESCRT system to maintain PM integrity.


Subject(s)
Autophagy-Related Proteins/metabolism , Cell Membrane/metabolism , Membrane Proteins/metabolism , Vesicular Transport Proteins/metabolism , Autophagosomes/metabolism , Autophagy-Related Proteins/genetics , HEK293 Cells , HeLa Cells , Humans , Immunoblotting , Immunoprecipitation , Membrane Proteins/genetics , Microscopy, Confocal , Protein Transport/physiology , Vesicular Transport Proteins/genetics
18.
J Biol Chem ; 297(2): 100940, 2021 08.
Article in English | MEDLINE | ID: covidwho-1293905

ABSTRACT

The severe acute respiratory syndrome coronavirus 2 envelope protein (S2-E) is a conserved membrane protein that is important for coronavirus (CoV) assembly and budding. Here, we describe the recombinant expression and purification of S2-E in amphipol-class amphipathic polymer solutions, which solubilize and stabilize membrane proteins, but do not disrupt membranes. We found that amphipol delivery of S2-E to preformed planar bilayers results in spontaneous membrane integration and formation of viroporin cation channels. Amphipol delivery of the S2-E protein to human cells results in plasma membrane integration, followed by retrograde trafficking to the trans-Golgi network and accumulation in swollen perinuclear lysosomal-associated membrane protein 1-positive vesicles, likely lysosomes. CoV envelope proteins have previously been proposed to manipulate the luminal pH of the trans-Golgi network, which serves as an accumulation station for progeny CoV particles prior to cellular egress via lysosomes. Delivery of S2-E to cells will enable chemical biological approaches for future studies of severe acute respiratory syndrome coronavirus 2 pathogenesis and possibly even development of "Trojan horse" antiviral therapies. Finally, this work also establishes a paradigm for amphipol-mediated delivery of membrane proteins to cells.


Subject(s)
Cell Membrane/drug effects , Coronavirus Envelope Proteins/metabolism , Polymers/pharmacology , Propylamines/pharmacology , Surface-Active Agents/pharmacology , trans-Golgi Network/metabolism , Cell Membrane/metabolism , Coronavirus Envelope Proteins/genetics , HeLa Cells , Humans , Lipid Bilayers/chemistry , Lipid Bilayers/metabolism , Lysosomes/metabolism , Polymers/chemistry , Propylamines/chemistry , Protein Transport , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , Surface-Active Agents/chemistry
19.
J Chem Phys ; 154(24): 245101, 2021 Jun 28.
Article in English | MEDLINE | ID: covidwho-1293030

ABSTRACT

Ethanol is highly effective against various enveloped viruses and can disable the virus by disintegrating the protective envelope surrounding it. The interactions between the coronavirus envelope (E) protein and its membrane environment play key roles in the stability and function of the viral envelope. By using molecular dynamics simulation, we explore the underlying mechanism of ethanol-induced disruption of a model coronavirus membrane and, in detail, interactions of the E-protein and lipids. We model the membrane bilayer as N-palmitoyl-sphingomyelin and 1-palmitoyl-2-oleoylphosphatidylcholine lipids and the coronavirus E-protein. The study reveals that ethanol causes an increase in the lateral area of the bilayer along with thinning of the bilayer membrane and orientational disordering of lipid tails. Ethanol resides at the head-tail region of the membrane and enhances bilayer permeability. We found an envelope-protein-mediated increase in the ordering of lipid tails. Our simulations also provide important insights into the orientation of the envelope protein in a model membrane environment. At ∼25 mol. % of ethanol in the surrounding ethanol-water phase, we observe disintegration of the lipid bilayer and dislocation of the E-protein from the membrane environment.


Subject(s)
Cell Membrane/drug effects , Cell Membrane/metabolism , Coronavirus/metabolism , Disinfectants/pharmacology , Ethanol/pharmacology , Viral Envelope Proteins/metabolism , Coronavirus/physiology , Lipid Bilayers/metabolism , Molecular Conformation , Molecular Dynamics Simulation , Permeability
20.
Front Immunol ; 12: 612807, 2021.
Article in English | MEDLINE | ID: covidwho-1282384

ABSTRACT

Since being identified as a key receptor for SARS-CoV-2, Angiotensin converting enzyme 2 (ACE2) has been studied as one of the potential targets for the development of preventative and/or treatment options. Tissue expression of ACE2 and the amino acids interacting with the spike protein of SARS-CoV-2 have been mapped. Furthermore, the recombinant soluble extracellular domain of ACE2 is already in phase 2 trials as a treatment for SARS-CoV-2 infection. Most studies have continued to focus on the ACE2 extracellular domain, which is known to play key roles in the renin angiotensin system and in amino acid uptake. However, few also found ACE2 to have an immune-modulatory function and its intracellular tail may be one of the signaling molecules in regulating cellular activation. The implication of its immune-modulatory role in preventing the cytokine-storm, observed in severe COVID-19 disease outcomes requires further investigation. This review focuses on the regulated proteolytic cleavage of ACE2 upon binding to inducer(s), such as the spike protein of SARS-CoV, the potential of cleaved ACE2 intracellular subdomain in regulating cellular function, and the ACE2's immune-modulatory function. This knowledge is critical for targeting ACE2 levels for developing prophylactic treatment or preventative measures in SARS-CoV infections.


Subject(s)
Angiotensin-Converting Enzyme 2/metabolism , COVID-19/pathology , Cell Membrane/metabolism , SARS-CoV-2/pathogenicity , Angiotensin-Converting Enzyme 2/chemistry , COVID-19/metabolism , COVID-19/virology , Humans , Immunomodulation , Protein Structure, Tertiary , Proteolysis , SARS-CoV-2/metabolism , Spike Glycoprotein, Coronavirus/metabolism
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