scholarly journals TMPRSS2 promotes SARS-CoV-2 evasion from NCOA7-mediated restriction

2021 ◽  
Author(s):  
Hataf Khan ◽  
Helena Winstone ◽  
Jose Jimenez-Guardeño ◽  
Carl Graham ◽  
Katie Doores ◽  
...  
Keyword(s):  
Gene Knockout ◽  
Critical Role ◽  
Ectopic Expression ◽  
Lung Epithelial Cells ◽  
Furin Cleavage ◽  
Nuclear Receptor Coactivator ◽  
Host Immune Responses ◽  
Lysosomal Protease ◽  
Furin Cleavage Site ◽  
Endosomal Acidification

Interferons play a critical role in regulating host immune responses to SARS-CoV-2, but the interferon (IFN)-stimulated gene (ISG) effectors that inhibit SARS-CoV-2 are not well characterized. The IFN-inducible short isoform of human nuclear receptor coactivator 7 (NCOA7) inhibits endocytic virus entry, interacts with the vacuolar ATPase, and promotes endo-lysosomal vesicle acidification and lysosomal protease activity. Here, we used ectopic expression and gene knockout to demonstrate that NCOA7 inhibits infection by SARS-CoV-2 as well as by lentivirus particles pseudotyped with SARS-CoV-2 Spike in lung epithelial cells. Infection with the highly pathogenic, SARS-CoV-1 and MERS-CoV, or seasonal, HCoV-229E and HCoV-NL63, coronavirus Spike-pseudotyped viruses was also inhibited by NCOA7. Importantly, either overexpression of TMPRSS2, which promotes plasma membrane fusion versus endosomal fusion of SARS-CoV-2, or removal of Spike’s polybasic furin cleavage site rendered SARS-CoV-2 less sensitive to NCOA7 restriction. Collectively, our data indicate that furin cleavage sensitizes SARS-CoV-2 Spike to the antiviral consequences of endosomal acidification by NCOA7, and suggest that the acquisition of furin cleavage may have favoured the co-option of cell surface TMPRSS proteases as a strategy to evade the suppressive effects of IFN-induced endo-lysosomal dysregulation on virus infection.

scholarly journals TMPRSS2 promotes SARS-CoV-2 evasion from NCOA7-mediated restriction

2021 ◽  
Vol 17 (11) ◽  
pp. e1009820
Author(s):  
Hataf Khan ◽  
Helena Winstone ◽  
Jose M. Jimenez-Guardeño ◽  
Carl Graham ◽  
Katie J. Doores ◽  
...  
Keyword(s):  
Gene Knockout ◽  
Critical Role ◽  
Ectopic Expression ◽  
Lung Epithelial Cells ◽  
Furin Cleavage ◽  
Nuclear Receptor Coactivator ◽  
Host Immune Responses ◽  
Lysosomal Protease ◽  
Furin Cleavage Site ◽  
Endosomal Acidification

Interferons play a critical role in regulating host immune responses to SARS-CoV-2, but the interferon (IFN)-stimulated gene (ISG) effectors that inhibit SARS-CoV-2 are not well characterized. The IFN-inducible short isoform of human nuclear receptor coactivator 7 (NCOA7) inhibits endocytic virus entry, interacts with the vacuolar ATPase, and promotes endo-lysosomal vesicle acidification and lysosomal protease activity. Here, we used ectopic expression and gene knockout to demonstrate that NCOA7 inhibits infection by SARS-CoV-2 as well as by lentivirus particles pseudotyped with SARS-CoV-2 Spike in lung epithelial cells. Infection with the highly pathogenic, SARS-CoV-1 and MERS-CoV, or seasonal, HCoV-229E and HCoV-NL63, coronavirus Spike-pseudotyped viruses was also inhibited by NCOA7. Importantly, either overexpression of TMPRSS2, which promotes plasma membrane fusion versus endosomal fusion of SARS-CoV-2, or removal of Spike’s polybasic furin cleavage site rendered SARS-CoV-2 less sensitive to NCOA7 restriction. Collectively, our data indicate that furin cleavage sensitizes SARS-CoV-2 Spike to the antiviral consequences of endosomal acidification by NCOA7, and suggest that the acquisition of furin cleavage may have favoured the co-option of cell surface TMPRSS proteases as a strategy to evade the suppressive effects of IFN-induced endo-lysosomal dysregulation on virus infection.

scholarly journals Alpha-Defensin HD5 Inhibits Furin Cleavage of Human Papillomavirus 16 L2 To Block Infection

2014 ◽  
Vol 89 (5) ◽  
pp. 2866-2874 ◽  
Author(s):  
Mayim E. Wiens ◽  
Jason G. Smith
Keyword(s):  
Human Papillomavirus ◽  
Cell Surface ◽  
Critical Role ◽  
Hpv Infection ◽  
Innate Immune ◽  
Furin Cleavage ◽  
Immune Effector ◽  
Cyclophilin B ◽  
Human Papillomavirus 16 ◽  
Furin Cleavage Site

ABSTRACTHuman papillomavirus (HPV) is a significant oncogenic virus, but the innate immune response to HPV is poorly understood. Human α-defensin 5 (HD5) is an innate immune effector peptide secreted by epithelial cells in the genitourinary tract. HD5 is broadly antimicrobial, exhibiting potent antiviral activity against HPV at physiologic concentrations; however, the specific mechanism of HD5-mediated inhibition against HPV is unknown. During infection, the HPV capsid undergoes several critical cell-mediated viral protein processing steps, including unfolding and cleavage of the minor capsid protein L2 by host cyclophilin B and furin. Using HPV16 pseudovirus, we show that HD5 interacts directly with the virus and inhibits the furin-mediated cleavage of L2 at the cell surface during infection at a step downstream of the cyclophilin B-mediated unfolding of L2. Importantly, HD5 does not affect the enzymatic activity of furin directly. Thus, our data support a model in which HD5 prevents furin from accessing L2 by occluding the furin cleavage site via direct binding to the viral capsid.IMPORTANCEOur study elucidates a new antiviral action for α-defensins against nonenveloped viruses in which HD5 directly interferes with a critical host-mediated viral processing step, furin cleavage of L2, at the cell surface. Blocking this key event has deleterious effects on the intracellular steps of virus infection. Thus, in addition to informing the antiviral mechanisms of α-defensins, our studies highlight the critical role of furin cleavage in HPV entry. Innate immune control, mediated in part by α-defensins expressed in the genital mucosa, may influence susceptibility to HPV infections that lead to cervical cancer. Moreover, understanding the mechanism of these natural antivirals may inform the design of therapeutics to limit HPV infection.

Network analysis outlines strengths and weaknesses of emerging SARS-CoV-2 Spike variants

2021 ◽  
Author(s):  
Pedro D Manrique ◽  
Srirupa Chakraborty ◽  
Kien Nguyen ◽  
Rachael Mansbach ◽  
Bette Korber ◽  
...  
Keyword(s):  
Graph Theory ◽  
Neutralizing Antibodies ◽  
Critical Role ◽  
Weighted Graph ◽  
Host Cells ◽  
Graph Representation ◽  
Furin Cleavage ◽  
Furin Cleavage Site ◽  
Critical Residues ◽  
Dynamics Simulations

The COVID-19 pandemic, caused by the SARS-CoV-2 virus, has triggered myriad efforts to dissect and understand the structure and dynamics of this complex pathogen. The Spike glycoprotein of SARS-CoV-2 has received special attention as it is the means by which the virus enters the human host cells. The N-terminal domain (NTD) is one of the targeted regions of the Spike protein for therapeutics and neutralizing antibodies against COVID-19. Though its function is not well-understood, the NTD is reported to acquire mutations and deletions that can accelerate the evolutionary adaptation of the virus driving antibody escape. Cellular processes are known to be regulated by complex interactions at the molecular level, which can be characterized by means of a graph representation facilitating the identification of key residues and critical communication pathways within the molecular complex. From extensive all-atom molecular dynamics simulations of the entire Spike for the wild-type and the dominant variant, we derive a weighted graph representation of the protein in two dominant conformations of the receptor-binding-domain; all-down and one-up. We implement graph theory techniques to characterize the relevance of specific residues at facilitating roles of communication and control, while uncovering key implications for fitness and adaptation. We find that many of the reported high-frequency mutations tend to occur away from the critical residues highlighted by our graph theory analysis, implying that these mutations tend to avoid targeting residues that are most critical for protein allosteric communication. We propose that these critical residues could be candidate targets for novel antibody therapeutics. In addition, our analysis provides quantitative insights of the critical role of the NTD and furin cleavage site and their wide-reaching influence over the protein at large. Many of our conclusions are supported by empirical evidence while others point the way towards crucial simulation-guided experiments.

scholarly journals Hydroxychloroquine-mediated inhibition of SARS-CoV-2 entry is attenuated by TMPRSS2

2021 ◽  
Vol 17 (1) ◽  
pp. e1009212 ◽  
Author(s):  
Tianling Ou ◽  
Huihui Mou ◽  
Lizhou Zhang ◽  
Amrita Ojha ◽  
Hyeryun Choe ◽  
...  
Keyword(s):  
Viral Entry ◽  
Cathepsin L ◽  
Mechanistic Explanation ◽  
Furin Cleavage ◽  
Culture Studies ◽  
S Protein ◽  
Furin Cleavage Site ◽  
Endosomal Acidification ◽  
S Proteins

Hydroxychloroquine, used to treat malaria and some autoimmune disorders, potently inhibits viral infection of SARS coronavirus (SARS-CoV-1) and SARS-CoV-2 in cell-culture studies. However, human clinical trials of hydroxychloroquine failed to establish its usefulness as treatment for COVID-19. This compound is known to interfere with endosomal acidification necessary to the proteolytic activity of cathepsins. Following receptor binding and endocytosis, cathepsin L can cleave the SARS-CoV-1 and SARS-CoV-2 spike (S) proteins, thereby activating membrane fusion for cell entry. The plasma membrane-associated protease TMPRSS2 can similarly cleave these S proteins and activate viral entry at the cell surface. Here we show that the SARS-CoV-2 entry process is more dependent than that of SARS-CoV-1 on TMPRSS2 expression. This difference can be reversed when the furin-cleavage site of the SARS-CoV-2 S protein is ablated or when it is introduced into the SARS-CoV-1 S protein. We also show that hydroxychloroquine efficiently blocks viral entry mediated by cathepsin L, but not by TMPRSS2, and that a combination of hydroxychloroquine and a clinically-tested TMPRSS2 inhibitor prevents SARS-CoV-2 infection more potently than either drug alone. These studies identify functional differences between SARS-CoV-1 and -2 entry processes, and provide a mechanistic explanation for the limited in vivo utility of hydroxychloroquine as a treatment for COVID-19.

scholarly journals Furin Cleavage Site Is Key to SARS-CoV-2 Pathogenesis

2020 ◽  
Author(s):  
Bryan A. Johnson ◽  
Xuping Xie ◽  
Birte Kalveram ◽  
Kumari G. Lokugamage ◽  
Antonio Muruato ◽  
...  
Keyword(s):  
Cleavage Site ◽  
Critical Role ◽  
Vero Cells ◽  
Mutant Virus ◽  
Spike Protein ◽  
Furin Cleavage ◽  
Furin Cleavage Site ◽  
Wide Range ◽  
The World

AbstractSARS-CoV-2 has resulted in a global pandemic and shutdown economies around the world. Sequence analysis indicates that the novel coronavirus (CoV) has an insertion of a furin cleavage site (PRRAR) in its spike protein. Absent in other group 2B CoVs, the insertion may be a key factor in the replication and virulence of SARS-CoV-2. To explore this question, we generated a SARS-CoV-2 mutant lacking the furin cleavage site (ΔPRRA) in the spike protein. This mutant virus replicated with faster kinetics and improved fitness in Vero E6 cells. The mutant virus also had reduced spike protein processing as compared to wild-type SARS-CoV-2. In contrast, the ΔPRRA had reduced replication in Calu3 cells, a human respiratory cell line, and had attenuated disease in a hamster pathogenesis model. Despite the reduced disease, the ΔPRRA mutant offered robust protection from SARS-CoV-2 rechallenge. Importantly, plaque reduction neutralization tests (PRNT50) with COVID-19 patient sera and monoclonal antibodies against the receptor-binding domain found a shift, with the mutant virus resulting in consistently reduced PRNT50 titers. Together, these results demonstrate a critical role for the furin cleavage site insertion in SARS-CoV-2 replication and pathogenesis. In addition, these findings illustrate the importance of this insertion in evaluating neutralization and other downstream SARS-CoV-2 assays.ImportanceAs COVID-19 has impacted the world, understanding how SARS-CoV-2 replicates and causes virulence offers potential pathways to disrupt its disease. By removing the furin cleavage site, we demonstrate the importance of this insertion to SARS-CoV-2 replication and pathogenesis. In addition, the findings with Vero cells indicate the likelihood of cell culture adaptations in virus stocks that can influence reagent generation and interpretation of a wide range of data including neutralization and drug efficacy. Overall, our work highlights the importance of this key motif in SARS-CoV-2 infection and pathogenesis.Article SummaryA deletion of the furin cleavage site in SARS-CoV-2 amplifies replication in Vero cells, but attenuates replication in respiratory cells and pathogenesis in vivo. Loss of the furin site also reduces susceptibility to neutralization in vitro.

scholarly journals Delta spike P681R mutation enhances SARS-CoV-2 fitness over Alpha variant

2021 ◽  
Author(s):  
Yang Liu ◽  
Jianying Liu ◽  
Bryan A. Johnson ◽  
Hongjie Xia ◽  
Zhiqiang Ku ◽  
...  
Keyword(s):  
Human Lung ◽  
Lung Epithelial Cells ◽  
Wild Type ◽  
Competition Assay ◽  
Furin Cleavage ◽  
Cleavage Efficiency ◽  
Furin Cleavage Site ◽  
Lung Epithelial ◽  
The World ◽  
Alpha Variant

SARS-CoV-2 Delta variant has rapidly replaced the Alpha variant around the world. The mechanism that drives this global replacement has not been defined. Here we report that Delta spike mutation P681R plays a key role in the Alpha-to-Delta variant replacement. In a replication competition assay, Delta SARS-CoV-2 efficiently outcompeted the Alpha variant in human lung epithelial cells and primary human airway tissues. Delta SARS-CoV-2 bearing the Alpha-spike glycoprotein replicated less efficiently than the wild-type Delta variant, suggesting the importance of Delta spike in enhancing viral replication. The Delta spike has accumulated mutation P681R located at a furin cleavage site that separates the spike 1 (S1) and S2 subunits. Reverting the P681R mutation to wild-type P681 significantly reduced the replication of Delta variant, to a level lower than the Alpha variant. Mechanistically, the Delta P681R mutation enhanced the cleavage of the full-length spike to S1 and S2, leading to increased infection via cell surface entry. In contrast, the Alpha spike also has a mutation at the same amino acid (P681H), but the spike cleavage from purified Alpha virions was reduced compared to the Delta spike. Collectively, our results indicate P681R as a key mutation in enhancing Delta variant replication via increased S1/S2 cleavage. Spike mutations that potentially affect furin cleavage efficiency must be closely monitored for future variant surveillance.

Ectopic expression of IL-5 identifies an additional CD4+T cell mechanism of airway eosinophil recruitment

2002 ◽  
Vol 282 (1) ◽  
pp. L99-L108 ◽  
Author(s):  
Jeffrey R. Crosby ◽  
H. H. Shen ◽  
M. T. Borchers ◽  
J. P. Justice ◽  
T. Ansay ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Inflammatory Responses ◽  
Gene Knockout ◽  
Critical Role ◽  
Ectopic Expression ◽  
Constitutive Expression ◽  
Lung Epithelium ◽  
Eosinophil Recruitment ◽  
Airway Lumen

CD4+T cells have a critical role in the development of allergic pulmonary inflammation, including the recruitment of eosinophils to the airway lumen and interstitium. The expression of interleukin (IL)-5 by CD4+cells has, in particular, often been lionized as the central link between allergic inflammation and the concomitant expansion or recruitment of eosinophils. The mechanism(s) by which CD4+T cells mediates eosinophil recruitment was assessed with gene knockout mice deficient for T cells or T cell subtypes and a unique IL-5 transgenic mouse (line NJ.1726) that constitutively overexpresses this cytokine in the lung epithelium. Pulmonary IL-5 expression is significantly attenuated in T cell- and CD4+but not CD8+cell-deficient animals, suggesting an obvious explanation for the lack of eosinophils in the lungs of T cell-deficient and CD4(−/−) mice. However, although the constitutive expression of IL-5 in the lung epithelium of NJ.1726 mice elicited an eosinophilia in the airway lumen of both naive and ovalbumin-treated mice, in the absence of CD4+cells, allergen-mediated eosinophil recruitment to the bronchoalveolar lavage fluid was abolished. Moreover, intranasal instillation of the potent eosinophil-specific chemokine eotaxin-2 was incapable of eliciting eosinophil recruitment in naive and ovalbumin-treated NJ.1726 CD4(−/−) mice, suggesting that eosinophil trafficking during allergic inflammatory responses is a consequence of a CD4+cell-mediated event(s) in addition to IL-5 expression and the establishment of a pulmonary chemokine gradient.

scholarly journals The Functional Consequences of the Novel Ribosomal Pausing Site in SARS-CoV-2 Spike Glycoprotein RNA

2021 ◽  
Vol 22 (12) ◽  
pp. 6490
Author(s):  
Olga A. Postnikova ◽  
Sheetal Uppal ◽  
Weiliang Huang ◽  
Maureen A. Kane ◽  
Rafael Villasmil ◽  
...  
Keyword(s):  
Amino Acid ◽  
Insertion Sequence ◽  
Experimental Studies ◽  
Spike Protein ◽  
Spike Glycoprotein ◽  
Furin Cleavage ◽  
New Host ◽  
S Protein ◽  
Furin Cleavage Site ◽  
Ribosome Pausing

The SARS-CoV-2 Spike glycoprotein (S protein) acquired a unique new 4 amino acid -PRRA- insertion sequence at amino acid residues (aa) 681–684 that forms a new furin cleavage site in S protein as well as several new glycosylation sites. We studied various statistical properties of the -PRRA- insertion at the RNA level (CCUCGGCGGGCA). The nucleotide composition and codon usage of this sequence are different from the rest of the SARS-CoV-2 genome. One of such features is two tandem CGG codons, although the CGG codon is the rarest codon in the SARS-CoV-2 genome. This suggests that the insertion sequence could cause ribosome pausing as the result of these rare codons. Due to population variants, the Nextstrain divergence measure of the CCU codon is extremely large. We cannot exclude that this divergence might affect host immune responses/effectiveness of SARS-CoV-2 vaccines, possibilities awaiting further investigation. Our experimental studies show that the expression level of original RNA sequence “wildtype” spike protein is much lower than for codon-optimized spike protein in all studied cell lines. Interestingly, the original spike sequence produces a higher titer of pseudoviral particles and a higher level of infection. Further mutagenesis experiments suggest that this dual-effect insert, comprised of a combination of overlapping translation pausing and furin sites, has allowed SARS-CoV-2 to infect its new host (human) more readily. This underlines the importance of ribosome pausing to allow efficient regulation of protein expression and also of cotranslational subdomain folding.

Differential regulation of granulopoiesis by the basic helix-loop-helix transcriptional inhibitors Id1 and Id2

Blood ◽  
2005 ◽  
Vol 105 (11) ◽  
pp. 4272-4281 ◽  
Author(s):  
Miranda Buitenhuis ◽  
Hanneke W. M. van Deutekom ◽  
Liesbeth P. Verhagen ◽  
Anders Castor ◽  
Sten Eirik W. Jacobsen ◽  
...  
Keyword(s):  
Critical Role ◽  
Ectopic Expression ◽  
Constitutive Expression ◽  
Retroviral Transduction ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
Cd34 Cells ◽  
Final Maturation ◽  
Inhibitor Of Dna Binding

Abstract Inhibitor of DNA binding (Id) proteins function as inhibitors of members of the basic helix-loop-helix family of transcription factors and have been demonstrated to play an important role in regulating lymphopoiesis. However, the role of these proteins in regulation of myelopoiesis is currently unclear. In this study, we have investigated the role of Id1 and Id2 in the regulation of granulopoiesis. Id1 expression was initially up-regulated during early granulopoiesis, which was then followed by a decrease in expression during final maturation. In contrast, Id2 expression was up-regulated in terminally differentiated granulocytes. In order to determine whether Id expression plays a critical role in regulating granulopoiesis, Id1 and Id2 were ectopically expressed in CD34+ cells by retroviral transduction. Our experiments demonstrate that constitutive expression of Id1 inhibits eosinophil development, whereas in contrast neutrophil differentiation was modestly enhanced. Constitutive Id2 expression accelerates final maturation of both eosinophils and neutrophils, whereas inhibition of Id2 expression blocks differentiation of both lineages. Transplantation of β2-microglobulin-/- nonobese diabetic severe combined immunodeficient (NOD/SCID) mice with CD34+ cells ectopically expressing Id1 resulted in enhanced neutrophil development, whereas ectopic expression of Id2 induced both eosinophil and neutrophil development. These data demonstrate that both Id1 and Id2 play a critical, although differential role in granulopoiesis.

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