Ca 2+ Ions Promote Fusion of Middle East Respiratory Syndrome Coronavirus with Host Cells and Increase Infectivity.

Autor:	Straus MR; Department of Microbiology and Immunology, Cornell University, Ithaca, New York, USA., Tang T; Robert Frederick Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, USA., Lai AL; ACERT, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, USA., Flegel A; Department of Microbiology and Immunology, Cornell University, Ithaca, New York, USA.; Institute of Veterinary Biochemistry, Freie Universität Berlin, Berlin, Germany., Bidon M; Robert Frederick Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, USA., Freed JH; ACERT, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, USA., Daniel S; Robert Frederick Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, USA sd386@cornell.edu grw7@cornell.edu., Whittaker GR; Department of Microbiology and Immunology, Cornell University, Ithaca, New York, USA sd386@cornell.edu grw7@cornell.edu.
Jazyk:	angličtina
Zdroj:	Journal of virology [J Virol] 2020 Jun 16; Vol. 94 (13). Date of Electronic Publication: 2020 Jun 16 (Print Publication: 2020).
DOI:	10.1128/JVI.00426-20
Abstrakt:	Fusion with, and subsequent entry into, the host cell is one of the critical steps in the life cycle of enveloped viruses. For Middle East respiratory syndrome coronavirus (MERS-CoV), the spike (S) protein is the main determinant of viral entry. Proteolytic cleavage of the S protein exposes its fusion peptide (FP), which initiates the process of membrane fusion. Previous studies on the related severe acute respiratory syndrome coronavirus (SARS-CoV) FP have shown that calcium ions (Ca 2+ ) play an important role in fusogenic activity via a Ca 2+ binding pocket with conserved glutamic acid (E) and aspartic acid (D) residues. SARS-CoV and MERS-CoV FPs share a high sequence homology, and here, we investigated whether Ca 2+ is required for MERS-CoV fusion by screening a mutant array in which E and D residues in the MERS-CoV FP were substituted with neutrally charged alanines (A). Upon verifying mutant cell surface expression and proteolytic cleavage, we tested their ability to mediate pseudoparticle (PP) infection of host cells in modulating Ca 2+ environments. Our results demonstrate that intracellular Ca 2+ enhances MERS-CoV wild-type (WT) PP infection by approximately 2-fold and that E891 is a crucial residue for Ca 2+ interaction. Subsequent electron spin resonance (ESR) experiments revealed that this enhancement could be attributed to Ca 2+ increasing MERS-CoV FP fusion-relevant membrane ordering. Intriguingly, isothermal calorimetry showed an approximate 1:1 MERS-CoV FP to Ca 2+ ratio, as opposed to an 1:2 SARS-CoV FP to Ca 2+ ratio, suggesting significant differences in FP Ca 2+ interactions of MERS-CoV and SARS-CoV FP despite their high sequence similarity. IMPORTANCE Middle East respiratory syndrome coronavirus (MERS-CoV) is a major emerging infectious disease with zoonotic potential and has reservoirs in dromedary camels and bats. Since its first outbreak in 2012, the virus has repeatedly transmitted from camels to humans, with 2,468 confirmed cases causing 851 deaths. To date, there are no efficacious drugs and vaccines against MERS-CoV, increasing its potential to cause a public health emergency. In order to develop novel drugs and vaccines, it is important to understand the molecular mechanisms that enable the virus to infect host cells. Our data have found that calcium is an important regulator of viral fusion by interacting with negatively charged residues in the MERS-CoV FP region. This information can guide therapeutic solutions to block this calcium interaction and also repurpose already approved drugs for this use for a fast response to MERS-CoV outbreaks. (Copyright © 2020 American Society for Microbiology.)
Databáze:	MEDLINE
Externí odkaz:	Zobrazit plný text záznamu