Corona and Influenza Virus Proteolytic Priming takes place in Tetraspanin-Enriched Membrane Microdomains Journal Article

Authors: Earnest, J. T.; Hantak, M. P.; Park, J. E.; Gallagher, T.
Article Title: Corona and Influenza Virus Proteolytic Priming takes place in Tetraspanin-Enriched Membrane Microdomains
Abstract: Coronaviruses (CoVs) and low-pathogenicity influenza A viruses (LP IAVs) depend on target cell proteases to cleave their viral glycoproteins and prime them for virus-cell membrane fusion. Several proteases cluster into tetraspanin-enriched microdomains (TEMs), suggesting that TEMs are preferred virus entry portals. Here we found that several CoV receptors and virus-priming proteases were indeed present in TEMs. Isolated TEMs, when mixed with CoV and LP IAV pseudo-particles, cleaved viral fusion proteins to fusion-primed fragments and potentiated viral transductions. That entering viruses utilize TEMs as a protease source was further confirmed using tetraspanin antibodies and tetraspanin shRNAs. Tetraspanin antibodies inhibited CoV and LP IAV infections, but their virus-blocking activities were overcome by expressing excess TEM-associated proteases. Similarly, cells with reduced levels of the tetraspanin CD9 resisted CoV pseudo-particle transductions, but were made susceptible by overproducing TEM-associated proteases. These findings indicated that antibodies and CD9 depletions interfere with viral proteolytic priming, in ways that are overcome by surplus proteases. TEMs appear to be exploited by some CoVs and LP IAVs for appropriate co-engagement with cell receptors and proteases. IMPORTANCE: Enveloped viruses use their surface glycoproteins to catalyze membrane fusion, an essential cell entry step. Host cell components prime these viral surface glycoproteins to catalyze membrane fusion at specific times and places during virus-cell entry. Amongst these priming components are proteases, which cleave viral surface glycoproteins, unleashing them to refold in ways that catalyze virus-cell membrane fusions. For some enveloped viruses, these proteases are known to reside on target cell surfaces. This research focuses on corona- and influenza A- virus-cell entry, and identifies TEMs as sites of viral proteolysis, thereby defining subcellular locations of virus priming with greater precision. Implications of these findings extend to the use of virus entry antagonists, such as protease inhibitors, which might be most effective when localized to these microdomains.
Journal Title: Journal of virology
Volume: 89
Issue: 11
ISSN: 1098-5514; 0022-538X
Publisher: American Society for Microbiology. All Rights Reserved  
Date Published: 2015
Start Page: 6093
End Page: 6104
Language: ENG
Notes: LR: 20150404; CI: Copyright (c) 2015; JID: 0113724; aheadofprint