ABSTRACT
Anti-spike neutralizing antibodies (S NAbs) have been developed for prevention and treatment against COVID-19. The nanoscopic characterization of the dynamic interaction between spike proteins and S NAbs remains difficult. By using high-speed atomic force microscopy (HS-AFM), we elucidate the molecular property of an S NAb and its interaction with spike proteins. The S NAb appeared as monomers with a Y conformation at low density and formed hexameric oligomers at high density. The dynamic S NAb-spike protein interaction at RBD induces neither RBD opening nor S1 subunit shedding. Furthermore, the interaction was stable at endosomal pH. These findings indicated that the S NAb could have a negligible risk of antibody-dependent enhancement. Dynamic movement of spike proteins on small extracellular vesicles (S sEV) resembled that on SARS-CoV-2. The sensitivity of variant S sEVs to S NAb could be evaluated using HS-AFM. Altogether, we demonstrate a nanoscopic assessment platform for evaluating the binding property of S NAbs.
Subject(s)
COVID-19 , Humans , SARS-CoV-2 , Spike Glycoprotein, Coronavirus , Antibodies, Viral , Antibodies, NeutralizingABSTRACT
SARS-CoV-2 spike protein (S) binds to human angiotensin-converting enzyme 2 (hACE2), allowing virus to dock on cell membrane follow by viral entry. Here, we use high-speed atomic force microscopy (HS-AFM) for real-time visualization of S, and its interaction with hACE2 and small extracellular vesicles (sEVs). Results show conformational heterogeneity of S, flexibility of S stalk and receptor-binding domain (RBD), and pH/temperature-induced conformational change of S. S in an S-ACE2 complex appears as an all-RBD up conformation. The complex acquires a distinct topology upon acidification. S and S2 subunit demonstrate different membrane docking mechanisms on sEVs. S-hACE2 interaction facilitates S to dock on sEVs, implying the feasibility of ACE2-expressing sEVs for viral neutralization. In contrary, S2 subunit docks on lipid layer and enters sEV using its fusion peptide, mimicking the viral entry scenario. Altogether, our study provides a platform that is suitable for real-time visualization of various entry inhibitors, neutralizing antibodies, and sEV-based decoy in blocking viral entry. Teaser: Comprehensive observation of SARS-CoV-2 spike and its interaction with receptor ACE2 and sEV-based decoy in real time using HS-AFM.
Subject(s)
Angiotensin-Converting Enzyme 2/metabolism , Extracellular Vesicles/metabolism , Spike Glycoprotein, Coronavirus/metabolism , Angiotensin-Converting Enzyme 2/chemistry , Humans , Hydrogen-Ion Concentration , Lipid Bilayers/metabolism , Microscopy, Atomic Force , Protein Binding , Protein Conformation , Protein Domains , Protein Subunits , SARS-CoV-2/drug effects , SARS-CoV-2/physiology , Spike Glycoprotein, Coronavirus/chemistry , Temperature , Virus InternalizationABSTRACT
Nuclear pore complexes (NPC) regulate molecular traffics on nuclear envelope, which plays crucial roles during cell fate specification and diseases. The viral accessory protein NSP9 of SARS-CoV-2 is reported to interact with nucleoporin 62 (NUP62), a structural component of the NPC, but its biological impact on the host cell remain obscure. Here, we established new cell line models with ectopic NSP9 expression and determined the subcellular destination and biological functions of NSP9. Confocal imaging identified NSP9 to be largely localized in close proximity to the endoplasmic reticulum. In agreement with the subcellular distribution of NSP9, association of NSP9 with NUP62 was observed in cytoplasm. Furthermore, the overexpression of NSP9 correlated with a reduction of NUP62 expression on the nuclear envelope, suggesting that attenuating NUP62 expression might have contributed to defective NPC formation. Importantly, the loss of NUP62 impaired translocation of p65, a subunit of NF-κB, upon TNF-α stimulation. Concordantly, NSP9 over-expression blocked p65 nuclear transport. Taken together, these data shed light on the molecular mechanisms underlying the modulation of host cells during SARS-CoV-2 infection.
Subject(s)
COVID-19/metabolism , COVID-19/virology , Host Microbial Interactions/physiology , Membrane Glycoproteins/metabolism , Nuclear Pore Complex Proteins/metabolism , RNA-Binding Proteins/metabolism , SARS-CoV-2/metabolism , Viral Nonstructural Proteins/metabolism , Active Transport, Cell Nucleus , Endoplasmic Reticulum/metabolism , Endoplasmic Reticulum/virology , Gene Knockdown Techniques , HeLa Cells , Humans , Membrane Glycoproteins/antagonists & inhibitors , Membrane Glycoproteins/genetics , Models, Biological , Nuclear Envelope/metabolism , Nuclear Envelope/virology , Nuclear Pore Complex Proteins/antagonists & inhibitors , Nuclear Pore Complex Proteins/genetics , RNA-Binding Proteins/genetics , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , Transcription Factor RelA/metabolism , Viral Nonstructural Proteins/geneticsABSTRACT
The novel human betacoronavirus SARS-CoV-2 has caused an unprecedented pandemic in the 21st century. Several studies have revealed interactions between SARS-CoV-2 viral proteins and host nucleoporins, yet their functions are largely unknown. Here, we demonstrate that the open-reading frame 6 (ORF6) of SARS-CoV-2 can directly manipulate localization and functions of nucleoporins. We found that ORF6 protein disrupted nuclear rim staining of nucleoporins RAE1 and NUP98. Consequently, this disruption caused aberrant nucleocytoplasmic trafficking and led to nuclear accumulation of mRNA transporters such as hnRNPA1. Ultimately, host cell nucleus size was reduced and cell growth was halted.