Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 292, Issue 14, Pages 6014-6026Publisher
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M117.777714
Keywords
fluorescence; host defense; membrane fusion; peptides; virus entry; Env inactivation; HIV neutralization; conformational changes; hemifusion; membrane-proximal extracellular domain
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Funding
- National Institutes of Health [R01 GM054787]
- FP7 Marie Curie Career Integration Grant [322130]
- Caritro Ricerca Biomedica [2013.0248]
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The host proteins, SERINC3 and SERINC5, have been recently shown to incorporate into HIV-1 particles and compromise their ability to fuse with target cells, an effect that is antagonized by the viral Nef protein. Envelope (Env) glycoproteins from different HIV-1 isolates exhibit a broad range of sensitivity to SERINC-mediated restriction, and the mechanism by which SERINCs interfere with HIV-1 fusion remains unclear. Here, we show that incorporation of SERINC5 into virions in the absence of Nef inhibits the formation of small fusion pores between viruses and cells. Strikingly, we found that SERINC5 promotes spontaneous functional inactivation of sensitive but not resistant Env glycoproteins. Although SERINC5-Env interaction was not detected by co-immunoprecipitation, incorporation of this protein enhanced the exposure of the conserved gp41 domains and sensitized the virus to neutralizing antibodies and gp41-derived inhibitory peptides. These results imply that SERINC5 restricts HIV-1 fusion at a step prior to small pore formation by selectively inactivating sensitive Env glycoproteins, likely through altering their conformation. The increased HIV-1 sensitivity to anti-gp41 antibodies and peptides suggests that SER5 also delays refolding of the remaining fusion-competent Env trimers.
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