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.

scholarly journals Sequence Analysis Indicates that 2019-nCoV Virus Contains a Putative Furin Cleavage Site at the Boundary of S1 and S2 Domains of Spike Protein

2020 ◽  
Author(s):  
Z. Galen WO
Keyword(s):  
Amino Acid ◽  
Cleavage Site ◽  
Spike Protein ◽  
Sequence Motif ◽  
Furin Cleavage ◽  
Host Cell Membrane ◽  
Virus Family ◽  
Prediction Program ◽  
Furin Cleavage Site ◽  
Novel Coronavirus

The infectious 2019-nCoV virus, which caused the current novel coronavirus pneumonia epidemic outbreak, possesses a unique 4-Amino Acid insert at the boundary of the two subdomains (S1 and S2) of Spike protein based on multiple protein sequence alignment with the large SARS and SARS-related virus family. Using Bat CoV_RaTG13 Spike protein as reference (sharing 97% aa identity) the 4-amino acid insert can be identified as PRRA (AA position 681-684). The effect of the 4-AA insertion is the presence of a furin signature sequence motif (PRRARSV) at the boundary of S1 and S2 domains of spike protein. This sequence motif consists the required Arg residue for P1 and P4 position of Furin site. In addition, it contains Arg at P3 site as well as Ser at P1’ site of furin motif. This sequence motif matches Aerolysin furin site in FurinDB and was predicted to be moderately strong (score 0.62) by ProP, a protease cleavage site prediction program. This finding suggests that the infectious 2019-nCoV virus, unlike SARS viruses, may be processed via cellular furin recognition and cleavage of the spike protein before host cell membrane fusion and entry. This putative furin site in spike protein of 2019-nCoV virus, if proven to be functional, suggests the potential of looking into agents inhibiting furin as therapeutic mean for the treatment of the novel coronavirus pneumonia.

scholarly journals A Furin Cleavage Site Inserted into the Spike Protein of SARS-CoV-2: A Structural Implication?

2020 ◽  
Author(s):  
Wei Li
Keyword(s):  
Cleavage Site ◽  
Structural Data ◽  
Cell Entry ◽  
Spike Protein ◽  
Spike Glycoprotein ◽  
Furin Cleavage ◽  
Furin Cleavage Site ◽  
Structural Consequence ◽  
Viral Cell Entry

One notable features of the SARS-CoV-2 genome is that the spike protein of SARS-CoV-2 has a functional polybasic (furin) cleavage site (RRAR) at the S1–S2 boundary through the insertion of 12 nucleotides encoding PRRA. To date, the furin cleavage site (FCS) remains an experimentally uncharted territory both structurally and functionally. For instance, whether or not FCS is actually cleaved, before or after viral cell entry or exit, still remains to be experimentally investigated. With currently available structural data, this article presents a computational structural characterization of the FCS inserted into SARS-CoV-2 spike glycoprotein, and puts forward a set of structural hypothesis against the hypothesis of SARS-CoV-2 from purposeful manipulation: (1), the inserted FCS does not alter, neither stabilize nor de-stabilize, the overall structure of SARS-CoV-2 spike glycoprotein; (2), the net structural consequence of FCS is the insertion of a furin cleavage site into SARS-CoV-2 spike glycoprotein, whose S1 and S2 subunits will still be bonded together even if the FCS is actually cleaved by furin protease.

scholarly journals Genomic surveillance reveals the emergence of SARS-CoV-2 Lineage A from Islamabad Pakistan

2021 ◽  
Author(s):  
Massab Umair ◽  
Aamer Ikram ◽  
Zaira Rehman ◽  
Syed Adnan Haider ◽  
Nazish Badar ◽  
...  
Keyword(s):  
Amino Acid ◽  
Virus Replication ◽  
Cleavage Site ◽  
Disease Dynamics ◽  
Amino Acid Deletion ◽  
Spike Glycoprotein ◽  
Furin Cleavage ◽  
Actual Impact ◽  
Furin Cleavage Site ◽  
The World

The lineage A of SARS-CoV-2 has been around the world since the start of the pandemic. In Pakistan the last case of lineage A was reported in April, 2021 since then no case has been reported. In November, 2021 during routine genomic surveillance at National Institute of Health we have found 07 cases of lineage A from Islamabad, Pakistan. The study reports two novel deletions in the spike glycoprotein. One 09 amino acid deletion (68-76 a.a) is found in the S1 subunit while another 10 amino acid deletion (679-688 a.a) observed at the junction of S1/S2 referred as furin cleavage site. The removal of furin cleavage site may result in impaired virus replication thus decreasing its pathogenesis. The actual impact of these two deletions on the virus replication and disease dynamics needs to be studied in detail. Moreover, the enhanced genomic surveillance will be required to track the spread of this lineage in other parts of the country.

scholarly journals Insight towards the effect of the multibasic cleavage site of SARS-CoV-2 spike protein on cellular proteases

2020 ◽  
Author(s):  
Kamal Shokeen ◽  
Shambhavi Pandey ◽  
Manisha Shah ◽  
Sachin Kumar
Keyword(s):  
Amino Acid ◽  
Host Cell ◽  
Cleavage Site ◽  
Decisive Role ◽  
Cell Receptor ◽  
Single Amino Acid ◽  
Furin Cleavage ◽  
Proteolytic Activation ◽  
S Protein ◽  
Furin Cleavage Site

AbstractSevere respiratory syndrome coronavirus 2 (SARS-CoV-2) infection presents an immense global health problem. Spike (S) protein of coronavirus is the primary determinant of its entry into the host as it consists of both receptor binding and fusion domain. While tissue tropism, host range, and pathogenesis of coronavirus are primarily controlled by the interaction of S protein with the cell receptor, it is possible that proteolytic activation of S protein by host cell proteases also plays a decisive role. The host-cell proteases have shown to be involved in the proteolysis of S protein and cleaving it into two functional subunits, S1 and S2, during the maturation process. In the present study, the interaction of S protein of SARS-CoV-2 with different host proteases like furin, cathepsin B, and plasmin has been analyzed. Incorporation of the furin cleavage site (R-R-A-R) in the S protein in SARS-CoV-2 has been studied by mutating the individual amino acid. Our results suggest the polytropic nature of the S protein of SARS-CoV-2. Our analysis indicated that a single amino acid substitution in the polybasic cleavage site of S protein perturb the binding of cellular proteases. This mutation study might help to generate an attenuated SARS-CoV-2. Besides, targeting of host proteases by inhibitors may result in a practical approach to stop the cellular spread of SARS-CoV-2 and to develop its antiviral.

scholarly journals The furin-S2’ site in avian coronavirus plays a key role in central nervous system damage progression

2021 ◽  
Author(s):  
Jinlong Cheng ◽  
Ye Zhao ◽  
Yanxin Hu ◽  
Jing Zhao ◽  
Jia Xue ◽  
...  
Keyword(s):  
Blood Brain Barrier ◽  
Cleavage Site ◽  
Quantitative Polymerase Chain Reaction ◽  
Spike Protein ◽  
Brain Barrier ◽  
Cell Tropism ◽  
Furin Cleavage ◽  
S Protein ◽  
Blood Brain ◽  
Furin Cleavage Site

The furin cleavage site plays an important role in virus pathogenicity. The spike protein of SARS-CoV-2 harbors a furin cleavage site insertion in contrast to SARS-CoV, which may be related to its stronger communicability. An avian coronavirus with an extra furin cleavage site upstream of the fusion peptide (S2’ site) infected monocyte cells and neuron cells leading to viremia or encephalitis, respectively. Immunohistochemistry and real-time quantitative polymerase chain reaction were used to follow disease progression and demonstrated differences between the parent avian coronavirus and mutated avian coronavirus with a furin-S2’ site. Magnetic resonance imaging and biological dye to evaluate the blood–brain barrier permeability showed that avian coronavirus with a furin-S2’ site had increased permeability compared with parent avian coronavirus. Immunohistochemistry of brains after intracerebral injection of avian coronavirus and immunofluorescence staining of primary neuron cells demonstrated the furin-S2’ site expanded the cell tropism of the mutant avian coronavirus to neuron cells. TNF-α, which has a key role in blood–brain barrier permeability, was highly induced by avian coronavirus with a furin-S2’ site compared with the parent avian coronavirus. We demonstrated the process involved in mutant avian coronavirus-induced disease and that the addition of a furin-S2’ site changed the virus cell tropism. IMPORTANCE Coronaviruses have broken out three times in two decades. Spike (S) protein plays a key role in the process of infection. To clarify importance of furin cleavage site in spike protein for coronavirus, we investigated the pathogenesis of neurotropic avian coronavirus whose spike protein contains an extra furin cleavage site (furin-S2’ site). By combining real-time quantitative polymerase chain reaction and immunohistochemistry we demonstrated that infectious bronchitis virus (IBV) infects brain instead of trachea when its S protein contains furin-S2’ site. Moreover, the virus was shown to increase the permeability of blood-brain barrier, infect neuron cells and induce high expression of TNF-α. Based on these results we further show that furin cleavage site in S protein plays an important role in coronavirus pathogenicity and cell tropism. Our study extends previous publications on function of S protein of coronavirus, increasing the understanding of researchers to coronavirus.

scholarly journals Delta variant with P681R critical mutation revealed by ultra-large atomic-scale ab initio simulation: Implications for the fundamentals of biomolecular interactions

2021 ◽  
Author(s):  
Puja Adhikari ◽  
Bahaa Jawad ◽  
Praveen Rao ◽  
Rudolf Podgornik ◽  
Wai-Yim Ching
Keyword(s):  
Amino Acid ◽  
Ab Initio ◽  
Infection Rate ◽  
Large Scale ◽  
Atomic Scale ◽  
Spike Protein ◽  
Furin Cleavage ◽  
Double Mutation ◽  
Furin Cleavage Site ◽  
High Infection

ABSTRACTSARS-CoV-2 Delta variant is emerging as a globally dominant strain. Its rapid spread and high infection rate are attributed to a mutation in the spike protein of SARS-CoV-2 allowing the virus to invade human cells much faster and with increased efficiency. Particularly, an especially dangerous mutation P681R close to the furin cleavage site has been identified as responsible for increasing the infection rate. Together with the earlier reported mutation D614G in the same domain, it offers an excellent instance to investigate the nature of mutations and how they affect the interatomic interactions in the spike protein. Here, using ultra large-scale ab initio computational modeling, we study the P681R and D614G mutations in the SD2-FP domain including the effect of double mutation and compare the results with the wild type. We have recently developed a method of calculating the amino acid-amino acid bond pairs (AABP) to quantitatively characterize the details of the interatomic interactions, enabling us to explain the nature of mutation at the atomic resolution. Our most significant find is that the mutations reduce the AABP value, implying a reduced bonding cohesion between interacting residues and increasing the flexibility of these amino acids to cause the damage. The possibility of using this unique mutation quantifiers in a machine learning protocol could lead to the prediction of emerging mutations.

scholarly journals Mutational spectra of SARS-CoV-2 isolated from animals

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e10609
Author(s):  
Ahmed Elaswad ◽  
Mohamed Fawzy ◽  
Shereen Basiouni ◽  
Awad A. Shehata
Keyword(s):  
Amino Acid ◽  
Wide Spectrum ◽  
Geographic Region ◽  
Heptad Repeat ◽  
Binding Motif ◽  
Amino Acid Substitutions ◽  
Furin Cleavage ◽  
S Protein ◽  
Furin Cleavage Site ◽  
Unique Amino Acid

Coronaviruses are ubiquitous and infect a wide spectrum of animals and humans. The newly emerged severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has become a worldwide pandemic. To address the role that animals may play in the evolution of SARS-CoV-2, the full genome sequences of SARS-CoV-2 isolated from animals were compared with SARS-CoV-2 human isolates from the same clade and geographic region. Phylogenetic analysis of SARS-CoV-2 isolated from the cat, dog, mink, mouse, and tiger revealed a close relationship with SARS-CoV-2 human isolates from the same clade and geographic region with sequence identities of 99.94–99.99%. The deduced amino acid sequence of spike (S) protein revealed the presence of a furin cleavage site (682RRAR▾685), which did not differ among all SARS-CoV-2 isolates from animals and humans. SARS-CoV-2 isolates from minks exhibited two amino acid substitutions (G261D, A262S) in the N-terminal domain of S protein and four (L452M, Y453F, F486L, N501T) in the receptor-binding motif (RBM). In the mouse, the S protein had two amino acid substitutions, one in the RBM (Q498H) and the other (N969S) in the heptad repeat 1. SARS-CoV-2 isolated from minks furtherly exhibited three unique amino acid substitutions in the nucleocapsid (N)protein. In the cat, two unique amino acid substitutions were discovered in the N (T247I) and matrix (T175M) proteins. Additionally, SARS-CoV-2 isolated from minks possessed sixteen, four, and two unique amino acid substitutions in the open reading frame 1ab (ORF1ab), ORF3a, and ORF6, respectively. Dog and cat SARS-CoV-2 isolates showed one and seven unique amino acid substitutions in ORF1ab, respectively. Further studies may be necessary to determine the pathogenic significance of these amino acid substitutions to understand the molecular epidemiology and evolution of SARS-CoV-2.

Viral and Host Attributes Underlying the Origins of Zoonotic Coronaviruses in Bats

2021 ◽  
Author(s):  
Alison E Stout ◽  
Qinghua Guo ◽  
Jean K Millet ◽  
Gary R Whittaker
Keyword(s):  
Viral Pathogenesis ◽  
Spike Protein ◽  
Future Research ◽  
Receptor Binding Domain ◽  
Viral Reservoirs ◽  
Furin Cleavage ◽  
Proteolytic Activation ◽  
Furin Cleavage Site ◽  
Unique Aspect ◽  
Genome Level

With a presumed origin in bats, the COVID-19 pandemic has been a major source of morbidity and mortality in the humanpopulation, and the causative agent, SARS-CoV-2, aligns most closely at the genome level with the bat coronavirusesRaBtCoV4991/RaTG13 and RmYN02. The ability of bats to provide reservoirs of numerous viruses in addition to coronavirusesremains an active area of research. Unique aspects of the physiology of the chiropteran immune system may contributeto the ability of bats to serve as viral reservoirs. The coronavirus spike protein plays important roles in viral pathogenesis and the immune response. Although much attention has focused on the spike receptor-binding domain, a unique aspect of SARS-CoV-2 as compared with its closest relatives is the presence of a furin cleavage site in the S1–S2 region of the spike protein. Proteolytic activation is likely an important feature that allows SARS-CoV-2—and other coronaviruses—to overcome the species barriers and thus cause human disease. The diversity of bat species limits the ability to draw broad conclusions about viral pathogenesis, but comparisons across species and with reference to humans and other susceptible mammals may guide future research in this regard.

scholarly journals SARS-CoV-2 convergent evolution as a guide to explore adaptive advantage

2021 ◽  
Author(s):  
Jiri Zahradnik ◽  
Jaroslav Nunvar ◽  
Gideon Schreiber
Keyword(s):  
Receptor Binding ◽  
Convergent Evolution ◽  
Great Majority ◽  
Viral Population ◽  
Binding Motif ◽  
Furin Cleavage ◽  
S Protein ◽  
Adaptive Mutations ◽  
Furin Cleavage Site ◽  
Protein Receptor

Much can be learned from 1.2 million sequences of SARS-CoV-2 generated during the last 15 months. Out of the overwhelming number of mutations sampled so far, only few rose to prominence in the viral population. Many of these emerged recently and independently in multiple lineages. Such a textbook example of convergent evolution at the molecular level is not only curiosity but a guide to uncover the basis for adaptive advantage behind these events. Focusing on the extent of the convergent evolution in the spike (S) protein, our report confirms that the most concerning SARS-CoV-2 lineages carry the heaviest burden of convergent S-protein mutations, suggesting their fundamental adaptive advantage. The great majority (21/25) of S-protein sites under convergent evolution tightly cluster in three functional domains; N-terminal domain, receptor-binding domain, and Furin cleavage site. We further show that among the S-protein receptor-binding motif mutations, ACE2 affinity-improving substitutions are favored. While the probed mutation space in the S protein covered all amino-acids reachable by single nucleotide changes, substitutions requiring two nucleotide changes or epistatic mutations of multiple-residues have only recently started to emerge. Unfortunately, despite their convergent emergence and physical association, most of these adaptive mutations and their combinations remain understudied. We aim to promote research of current variants which are currently understudied but may become important in the future.

scholarly journals Spike glycoprotein and host cell determinants of SARS-CoV-2 entry and cytopathic effects

2020 ◽  
Author(s):  
Hanh T. Nguyen ◽  
Shijian Zhang ◽  
Qian Wang ◽  
Saumya Anang ◽  
Jia Wang ◽  
...  
Keyword(s):  
Host Cell ◽  
Cell Fusion ◽  
Cleavage Site ◽  
Virus Entry ◽  
Cytoplasmic Tail ◽  
Syncytium Formation ◽  
Spike Glycoprotein ◽  
Furin Cleavage ◽  
Cytopathic Effects ◽  
Furin Cleavage Site

SARS-CoV-2, a betacoronavirus, is the cause of the COVID-19 pandemic. The SARS-CoV-2 spike (S) glycoprotein trimer mediates virus entry into host cells and cytopathic effects (syncytium formation). We studied the contribution of several S glycoprotein features to these functions, focusing on those that differ among related coronaviruses. Acquisition of the furin cleavage site by the SARS-CoV-2 S glycoprotein decreased virus stability and infectivity, but greatly enhanced syncytium-forming ability. Notably, the D614G change found in globally predominant SARS-CoV-2 strains increased infectivity, modestly enhanced responsiveness to the ACE2 receptor and susceptibility to neutralizing sera, and tightened association of the S1 subunit with the trimer. Apparently, these two features of the SARS-CoV-2 S glycoprotein, the furin cleavage site and D614G, have evolved to balance virus infectivity, stability, cytopathicity and antibody vulnerability. Although the endodomain (cytoplasmic tail) of the S2 subunit was not absolutely required for virus entry or syncytium formation, alteration of palmitoylated cysteine residues in the cytoplasmic tail decreased the efficiency of these processes. As proteolytic cleavage contributes to the activation of the SARS-CoV-2 S glycoprotein, we evaluated the ability of protease inhibitors to suppress S glycoprotein function. Matrix metalloprotease inhibitors suppressed S-mediated cell-cell fusion, but not virus entry. Synergy between inhibitors of matrix metalloproteases and TMPRSS2 suggests that both host proteases can activate the S glycoprotein during the process of syncytium formation. These results provide insights into SARS-CoV-2 S glycoprotein-host cell interactions that likely contribute to the transmission and pathogenicity of this pandemic agent. IMPORTANCE The development of an effective and durable SARS-CoV-2 vaccine is essential for combating the growing COVID-19 pandemic. The SARS-CoV-2 spike (S) glycoprotein is the main target of neutralizing antibodies elicited during virus infection or following vaccination. Knowledge of the spike glycoprotein evolution, function and interactions with host factors will help researchers to develop effective vaccine immunogens and treatments. Here we identify key features of the spike glycoprotein, including the furin cleavage site and the D614G natural mutation, that modulate viral cytopathic effects, infectivity and sensitivity to inhibition. We also identify two inhibitors of host metalloproteases that block S-mediated cell-cell fusion, a process that contributes to the destruction of the virus-infected cell.

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