Abstract Coronavirus disease (COVID-19) is a contagious respiratory disease caused by the SARS-CoV-2 virus. The clinical phenotypes are variable, ranging from spontaneous recovery to serious illness and death. On March 2020, a global COVID-19 pandemic was declared by the World Health Organization (WHO). As of February 2023, almost 670 million cases and 6,8 million deaths have been confirmed worldwide. Coronaviruses, including SARS-CoV-2, contain a single-stranded RNA genome enclosed in a viral capsid consisting of four structural proteins: the nucleocapsid (N) protein, in the ribonucleoprotein core, the spike (S) protein, the envelope (E) protein, and the membrane (M) protein, embedded in the surface envelope. In particular, the E protein is a poorly characterized viroporin with high identity amongst all the β-coronaviruses (SARS-CoV-2, SARS-CoV, MERS-CoV, HCoV-OC43) and a low mutation rate. Here, we focused our attention on the study of SARS-CoV-2 E and M proteins, and we found a general perturbation of the host cell calcium (Ca 2+ ) homeostasis and a selective rearrangement of the interorganelle contact sites. In vitro and in vivo biochemical analyses revealed that the binding of specific nanobodies to soluble regions of SARS-CoV-2 E protein reversed the observed phenotypes, suggesting that the E protein might be an important therapeutic candidate not only for vaccine development, but also for the clinical management of COVID designing drug regimens that, so far, are very limited.
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Hexamethylene amiloride binds the SARS‐CoV‐2 envelope protein at the protein–lipid interface
The SARS‐CoV‐2 envelope (E) protein forms a five‐helix bundle in lipid bilayers whose cation‐conducting activity is associated with the inflammatory response and respiratory distress symptoms of COVID‐19. E channel activity is inhibited by the drug 5‐(N,N‐hexamethylene) amiloride (HMA). However, the binding site of HMA in E has not been determined. Here we use solid‐state NMR to measure distances between HMA and the E transmembrane domain (ETM) in lipid bilayers.13C,15N‐labeled HMA is combined with fluorinated or13C‐labeled ETM. Conversely, fluorinated HMA is combined with13C,15N‐labeled ETM. These orthogonal isotopic labeling patterns allow us to conduct dipolar recoupling NMR experiments to determine the HMA binding stoichiometry to ETM as well as HMA‐protein distances. We find that HMA binds ETM with a stoichiometry of one drug per pentamer. Unexpectedly, the bound HMA is not centrally located within the channel pore, but lies on the lipid‐facing surface in the middle of the TM domain. This result suggests that HMA may inhibit the E channel activity by interfering with the gating function of an aromatic network. These distance data are obtained under much lower drug concentrations than in previous chemical shift perturbation data, which showed the largest perturbation for N‐terminal residues. This difference suggests that HMA has higher affinity for the protein–lipid interface than the channel pore. These results give insight into the inhibition mechanism of HMA for SARS‐CoV‐2 E.
more » « less- NSF-PAR ID:
- 10463172
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Protein Science
- Volume:
- 32
- Issue:
- 10
- ISSN:
- 0961-8368
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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