This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Google Scholar
Right arrow Articles by Yamada, Y.
Right arrow Articles by Liu, D. X.
PubMed
Right arrow PubMed Citation
Right arrow Articles by Yamada, Y.
Right arrow Articles by Liu, D. X.

 Previous Article  |  Next Article 

Journal of Virology, September 2009, p. 8744-8758, Vol. 83, No. 17
0022-538X/09/$08.00+0     doi:10.1128/JVI.00613-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Proteolytic Activation of the Spike Protein at a Novel RRRR/S Motif Is Implicated in Furin-Dependent Entry, Syncytium Formation, and Infectivity of Coronavirus Infectious Bronchitis Virus in Cultured Cells{triangledown}

Yoshiyuki Yamada1 and Ding Xiang Liu1,2*

Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673,1 Department of Biological Sciences, National University of Singapore, Science Drive 4, Singapore 1175432

Received 25 March 2009/ Accepted 13 June 2009

The spike (S) protein of the coronavirus (CoV) infectious bronchitis virus (IBV) is cleaved into S1 and S2 subunits at the furin consensus motif RRFRR537/S in virus-infected cells. In this study, we observe that the S2 subunit of the IBV Beaudette strain is additionally cleaved at the second furin site (RRRR690/S) in cells expressing S constructs and in virus-infected cells. Detailed time course experiments showed that a peptide furin inhibitor, decanoyl-Arg-Val-Lys-Arg-chloromethylketone, blocked both viral entry and syncytium formation. Site-directed mutagenesis studies revealed that the S1/S2 cleavage by furin was not necessary for, but could promote, syncytium formation by and infectivity of IBV in Vero cells. In contrast, the second site is involved in the furin dependence of viral entry and syncytium formation. Mutations of the second site from furin-cleavable RRRR/S to non-furin-cleavable PRRRS and AAARS, respectively, abrogated the furin dependence of IBV entry. Instead, a yet-to-be-identified serine protease(s) was involved, as revealed by protease inhibitor studies. Furthermore, sequence analysis of CoV S proteins by multiple alignments showed conservation of an XXXR/S motif, cleavable by either furin or other trypsin-like proteases, at a position equivalent to the second IBV furin site. Taken together, these results suggest that proteolysis at a novel XXXR/S motif in the S2 subunit might be a common mechanism for the entry of CoV into cells.

* Corresponding author. Mailing address: Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673. Phone: 65 6586 9581. Fax: 65 6779 1117. E-mail: dxliu{at}imcb.a-star.edu.sg

{triangledown} Published ahead of print on 24 June 2009.

Journal of Virology, September 2009, p. 8744-8758, Vol. 83, No. 17
0022-538X/09/$08.00+0     doi:10.1128/JVI.00613-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»