SERINC5 protein inhibits HIV-1 fusion pore formation by promoting functional inactivation of envelope glycoproteins.
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.
From the Department of Pediatrics, Emory University, Atlanta, Georgia 30322 and.
Chetan
C
Sood
From the Department of Pediatrics, Emory University, Atlanta, Georgia 30322 and.
Mariana
M
Marin
the Centre for Integrative Biology, University of Trento, 38123 Trento, Italy.
Ajit
A
Chande
the Centre for Integrative Biology, University of Trento, 38123 Trento, Italy.
Massimo
M
Pizzato
From the Department of Pediatrics, Emory University, Atlanta, Georgia 30322 and gmeliki@emory.edu.
Gregory B
GB
Melikyan
D057809:HEK293 Cells; D015483:HIV Antibodies / Q000494:pharmacology; D015700:HIV Envelope Protein gp41 / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D000072417:Protein Domains; D058849:Protein Refolding; D054311:nef Gene Products, Human Immunodeficiency Virus / Q000235:genetics / Q000378:metabolism
D015483:HIV Antibodies; D015700:HIV Envelope Protein gp41; D008565:Membrane Proteins; C000602387:SERINC5 protein, human; C514787:gp41 protein, Human immunodeficiency virus 1; D054311:nef Gene Products, Human Immunodeficiency Virus; C514837:nef protein, Human immunodeficiency virus 1
Env inactivation; HIV neutralization; conformational changes; fluorescence; hemifusion; host defense; membrane fusion; membrane-proximal extracellular domain; peptides; virus entry