Bimodular effects of D614G mutation on the spike glycoprotein of SARS-CoV-2 enhance protein processing, membrane fusion, and viral infectivity.
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ABSTRACT:
SUBMITTER: Jiang X
PROVIDER: S-EPMC7670837 | biostudies-literature | 2020 Nov
REPOSITORIES: biostudies-literature
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Bimodular effects of D614G mutation on the spike glycoprotein of SARS-CoV-2 enhance protein processing, membrane fusion, and viral infectivity.
Jiang Xiaoyi X Zhang Zhengrong Z Wang Chenxi C Ren Hongguang H Gao Lihua L Peng Haoran H Niu Zubiao Z Ren He H Huang Hongyan H Sun Qiang Q
Signal transduction and targeted therapy 20201117 1
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Project description:SARS-CoV-2 variants with spike (S)-protein D614G mutations now predominate globally. We therefore compare the properties of the mutated S protein (SG614) with the original (SD614). We report here pseudoviruses carrying SG614 enter ACE2-expressing cells more efficiently than those with SD614. This increased entry correlates with less S1-domain shedding and higher S-protein incorporation into the virion. Similar results are obtained with virus-like particles produced with SARS-CoV-2 M, N, E, and S proteins. However, D614G does not alter S-protein binding to ACE2 or neutralization sensitivity of pseudoviruses. Thus, D614G may increase infectivity by assembling more functional S protein into the virion.
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Project description:SARS‐CoV‐2 has become an increasingly dangerous virus infecting 77.6 million people and resulting in over 2 million deaths in the last year. The spike glycoprotein plays an important role in the viral infection process by recognizing and binding to the ACE2 receptor in host's cells. Due to the importance of this protein, current research efforts are focused on mutations that impact viral infectivity. SARS‐CoV‐2 viruses with a spike mutation at position 614 were recently shown to be more infectious than their wild‐type ancestor. The D614G substitution eliminates a hydrogen bond with a threonine residue (T859) in an adjacent protein chain, allowing the spike protein to assume more readily an open conformation. Since the open conformation mediates attachment to the ACE2 receptor, the D614G mutant causes higher infectivity than the wild‐type spike protein. The main goal of this research was to create physical 3D printed models of the wild‐type and mutant spike proteins to visualize the molecular changes caused by the D614G mutation. Structural analyses of the wild‐type and the D614G spike mutant were performed using the Protein Data Bank files, 6vxx and 6xs6. To visualize the conformational changes caused by the D614G mutation, the protein structure alignments were performed using Pymol. A combined file containing the superimposed structures was imported into Jmol to create the scripts for model construction and 3D printing. A small protein model was built to describe the overall structure of the spike and the location of the amino acids linked to higher viral infectivity. An additional detailed model was constructed to illustrate the biochemical interactions at the mutation site. In this model, important amino acids such as Asp614, Ala647, and Thr859 are highlighted due to their role in hydrogen bonding and spike protein binding to the ACE2 receptor. A magnetic piece was created to show the effects of the aspartic acid to glycine mutation at position 614. A Jmol tutorial was designed to complement the 3D models and assess students’ learning of the structure and function of SARS‐CoV‐2 spike protein. This exercise will allow undergraduate students and faculty to visualize and better understand how single amino acid mutations can lead to changes in viral infectivity.
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Project description:With the COVID-19 pandemic, the evolutionary fate of SARS-CoV-2 becomes a matter of utmost concern. Mutation D614G in the spike (S) protein has become dominant, and recent evidence suggests it yields a more stable phenotype with higher transmission efficacy. We carry out a structural analysis that provides mechanistic clues on the enhanced infectivity. The D614G substitution creates a sticky packing defect in subunit S1, promoting its association with subunit S2 as a means to stabilize the structure of S1 within the S1/S2 complex. The results raise the therapeutic possibility of immunologically targeting the epitope involved in stabilizing the G614 phenotype as a means of reducing the infection efficacy of SARS-CoV-2. This therapeutic modality would not a-priori interfere directly with current efforts toward the immunological targeting of the RBD epitope; hence, it could be exploited as a complementary treatment.
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Project description:SARS coronavirus 2 (SARS-CoV-2) isolates encoding a D614G mutation in the viral spike (S) protein predominate over time in locales where it is found, implying that this change enhances viral transmission. We therefore compared the functional properties of the S proteins with aspartic acid (S D614 ) and glycine (S G614 ) at residue 614. We observed that retroviruses pseudotyped with S G614 infected ACE2-expressing cells markedly more efficiently than those with S D614 . This greater infectivity was correlated with less S1 shedding and greater incorporation of the S protein into the pseudovirion. Similar results were obtained using the virus-like particles produced with SARS-CoV-2 M, N, E, and S proteins. However, S G614 did not bind ACE2 more efficiently than S D614 , and the pseudoviruses containing these S proteins were neutralized with comparable efficiencies by convalescent plasma. These results show S G614 is more stable than S D614 , consistent with epidemiological data suggesting that viruses with S G614 transmit more efficiently.
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Project description:The SARS-CoV2 coronavirus responsible for the current COVID19 pandemic has been reported to have a relatively low mutation rate. Nevertheless, a few prevalent variants have arisen that give the appearance of undergoing positive selection as they are becoming increasingly widespread over time. Most prominent among these is the D614G amino acid substitution in the SARS-CoV2 Spike protein, which mediates viral entry. The D614G substitution, however, is in linkage disequilibrium with the ORF1b P314L mutation where both mutations almost invariably co-occur, making functional inferences problematic. In addition, the possibility of repeated new introductions of the mutant strain does not allow one to distinguish between a founder effect and an intrinsic genetic property of the virus. Here, we synthesized and expressed the WT and D614G variant SARS-Cov2 Spike protein, and report that using a SARS-CoV2 Spike protein pseudotyped lentiviral vector we observe that the D614G variant Spike has >1/2 log10 increased infectivity in human cells expressing the human ACE2 protein as the viral receptor. The increased binding/fusion activity of the D614G Spike protein was corroborated in a cell fusion assay using Spike and ACE2 proteins expressed in different cells. These results are consistent with the possibility that the Spike D614G mutant increases the infectivity of SARS-CoV2.
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Project description:The development of the SARS-CoV-2 pandemic has prompted an extensive worldwide sequencing effort to characterise the geographical spread and molecular evolution of the virus. A point mutation in the spike protein, D614G, emerged as the virus spread from Asia into Europe and the USA, and has rapidly become the dominant form worldwide. Here we review how the D614G variant was identified and discuss recent evidence about the effect of the mutation on the characteristics of the virus, clinical outcome of infection and host immune response.
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Project description:The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein substitution D614G became dominant during the coronavirus disease 2019 (COVID-19) pandemic1,2. However, the effect of this variant on viral spread and vaccine efficacy remains to be defined. Here we engineered the spike D614G substitution in the USA-WA1/2020 SARS-CoV-2 strain, and found that it enhances viral replication in human lung epithelial cells and primary human airway tissues by increasing the infectivity and stability of virions. Hamsters infected with SARS-CoV-2 expressing spike(D614G) (G614 virus) produced higher infectious titres in nasal washes and the trachea, but not in the lungs, supporting clinical evidence showing that the mutation enhances viral loads in the upper respiratory tract of COVID-19 patients and may increase transmission. Sera from hamsters infected with D614 virus exhibit modestly higher neutralization titres against G614 virus than against D614 virus, suggesting that the mutation is unlikely to reduce the ability of vaccines in clinical trials to protect against COVID-19, and that therapeutic antibodies should be tested against the circulating G614 virus. Together with clinical findings, our work underscores the importance of this variant in viral spread and its implications for vaccine efficacy and antibody therapy.
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Project description:The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein acquired a D614G mutation early in the pandemic that confers greater infectivity and is now the globally dominant form. To determine whether D614G might also mediate neutralization escape that could compromise vaccine efficacy, sera from spike-immunized mice, nonhuman primates, and humans were evaluated for neutralization of pseudoviruses bearing either D614 or G614 spike. In all cases, the G614 pseudovirus was moderately more susceptible to neutralization. The G614 pseudovirus also was more susceptible to neutralization by receptor-binding domain (RBD) monoclonal antibodies and convalescent sera from people infected with either form of the virus. Negative stain electron microscopy revealed a higher percentage of the 1-RBD "up" conformation in the G614 spike, suggesting increased epitope exposure as a mechanism of enhanced vulnerability to neutralization. Based on these findings, the D614G mutation is not expected to be an obstacle for current vaccine development.
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Project description:The D614G mutation in the spike protein of SARS-CoV-2 alters the fitness of the virus, leading to the dominant form observed in the COVID-19 pandemic. However, the molecular basis of the mechanism by which this mutation enhances fitness is not clear. Here we demonstrated by cryo-electron microscopy that the D614G mutation resulted in increased propensity of multiple receptor-binding domains (RBDs) in an upward conformation poised for host receptor binding. Multiple substates within the one RBD-up or two RBD-up conformational space were determined. According to negative staining electron microscopy, differential scanning calorimetry, and differential scanning fluorimetry, the most significant impact of the mutation lies in its ability to eliminate the unusual cold-induced unfolding characteristics and to significantly increase the thermal stability under physiological pH. The D614G spike variant also exhibited exceptional long-term stability when stored at 37 °C for up to 2 months. Our findings shed light on how the D614G mutation enhances the infectivity of SARS-CoV-2 through a stabilizing mutation and suggest an approach for better design of spike protein-based conjugates for vaccine development.
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