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The tetraspanin CD9 facilitates MERS-coronavirus entry by scaffolding host cell receptors and proteases.
PLoS Pathog. 2017 Jul; 13(7):e1006546.PP

Abstract

Infection by enveloped coronaviruses (CoVs) initiates with viral spike (S) proteins binding to cellular receptors, and is followed by proteolytic cleavage of receptor-bound S proteins, which prompts S protein-mediated virus-cell membrane fusion. Infection therefore requires close proximity of receptors and proteases. We considered whether tetraspanins, scaffolding proteins known to facilitate CoV infections, hold receptors and proteases together on cell membranes. Using knockout cell lines, we found that the tetraspanin CD9, but not the tetraspanin CD81, formed cell-surface complexes of dipeptidyl peptidase 4 (DPP4), the MERS-CoV receptor, and the type II transmembrane serine protease (TTSP) member TMPRSS2, a CoV-activating protease. This CD9-facilitated condensation of receptors and proteases allowed MERS-CoV pseudoviruses to enter cells rapidly and efficiently. Without CD9, MERS-CoV viruses were not activated by TTSPs, and they trafficked into endosomes to be cleaved much later and less efficiently by cathepsins. Thus, we identified DPP4:CD9:TTSP as the protein complexes necessary for early, efficient MERS-CoV entry. To evaluate the importance of these complexes in an in vivo CoV infection model, we used recombinant Adenovirus 5 (rAd5) vectors to express human DPP4 in mouse lungs, thereby sensitizing the animals to MERS-CoV infection. When the rAd5-hDPP4 vectors co-expressed small RNAs silencing Cd9 or Tmprss2, the animals were significantly less susceptible, indicating that CD9 and TMPRSS2 facilitated robust in vivo MERS-CoV infection of mouse lungs. Furthermore, the S proteins of virulent mouse-adapted MERS-CoVs acquired a CD9-dependent cell entry character, suggesting that CD9 is a selective agent in the evolution of CoV virulence.

Authors+Show Affiliations

Department of Microbiology and Immunology, Loyola University Medical Center, Maywood, IL, United States of America.Department of Microbiology and Immunology, Loyola University Medical Center, Maywood, IL, United States of America.Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, IA, United States of America.Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, IA, United States of America.Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, IA, United States of America. Department of Microbiology, University of Iowa, Iowa City, IA, United States of America.Department of Microbiology and Immunology, Loyola University Medical Center, Maywood, IL, United States of America.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

28759649

Citation

Earnest, James T., et al. "The Tetraspanin CD9 Facilitates MERS-coronavirus Entry By Scaffolding Host Cell Receptors and Proteases." PLoS Pathogens, vol. 13, no. 7, 2017, pp. e1006546.
Earnest JT, Hantak MP, Li K, et al. The tetraspanin CD9 facilitates MERS-coronavirus entry by scaffolding host cell receptors and proteases. PLoS Pathog. 2017;13(7):e1006546.
Earnest, J. T., Hantak, M. P., Li, K., McCray, P. B., Perlman, S., & Gallagher, T. (2017). The tetraspanin CD9 facilitates MERS-coronavirus entry by scaffolding host cell receptors and proteases. PLoS Pathogens, 13(7), e1006546. https://doi.org/10.1371/journal.ppat.1006546
Earnest JT, et al. The Tetraspanin CD9 Facilitates MERS-coronavirus Entry By Scaffolding Host Cell Receptors and Proteases. PLoS Pathog. 2017;13(7):e1006546. PubMed PMID: 28759649.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - The tetraspanin CD9 facilitates MERS-coronavirus entry by scaffolding host cell receptors and proteases. AU - Earnest,James T, AU - Hantak,Michael P, AU - Li,Kun, AU - McCray,Paul B,Jr AU - Perlman,Stanley, AU - Gallagher,Tom, Y1 - 2017/07/31/ PY - 2017/03/31/received PY - 2017/07/21/accepted PY - 2017/08/10/revised PY - 2017/8/2/pubmed PY - 2017/9/19/medline PY - 2017/8/1/entrez SP - e1006546 EP - e1006546 JF - PLoS pathogens JO - PLoS Pathog VL - 13 IS - 7 N2 - Infection by enveloped coronaviruses (CoVs) initiates with viral spike (S) proteins binding to cellular receptors, and is followed by proteolytic cleavage of receptor-bound S proteins, which prompts S protein-mediated virus-cell membrane fusion. Infection therefore requires close proximity of receptors and proteases. We considered whether tetraspanins, scaffolding proteins known to facilitate CoV infections, hold receptors and proteases together on cell membranes. Using knockout cell lines, we found that the tetraspanin CD9, but not the tetraspanin CD81, formed cell-surface complexes of dipeptidyl peptidase 4 (DPP4), the MERS-CoV receptor, and the type II transmembrane serine protease (TTSP) member TMPRSS2, a CoV-activating protease. This CD9-facilitated condensation of receptors and proteases allowed MERS-CoV pseudoviruses to enter cells rapidly and efficiently. Without CD9, MERS-CoV viruses were not activated by TTSPs, and they trafficked into endosomes to be cleaved much later and less efficiently by cathepsins. Thus, we identified DPP4:CD9:TTSP as the protein complexes necessary for early, efficient MERS-CoV entry. To evaluate the importance of these complexes in an in vivo CoV infection model, we used recombinant Adenovirus 5 (rAd5) vectors to express human DPP4 in mouse lungs, thereby sensitizing the animals to MERS-CoV infection. When the rAd5-hDPP4 vectors co-expressed small RNAs silencing Cd9 or Tmprss2, the animals were significantly less susceptible, indicating that CD9 and TMPRSS2 facilitated robust in vivo MERS-CoV infection of mouse lungs. Furthermore, the S proteins of virulent mouse-adapted MERS-CoVs acquired a CD9-dependent cell entry character, suggesting that CD9 is a selective agent in the evolution of CoV virulence. SN - 1553-7374 UR - https://www.unboundmedicine.com/medline/citation/28759649/The_tetraspanin_CD9_facilitates_MERS_coronavirus_entry_by_scaffolding_host_cell_receptors_and_proteases_ L2 - https://dx.plos.org/10.1371/journal.ppat.1006546 DB - PRIME DP - Unbound Medicine ER -