Single residues in the surface subunits of oncogenic sheep retrovirus envelopes distinguish receptor-mediated triggering for fusion at low pH and infection

Marceline Côté, Yi Min Zheng, Lorraine Albritton, Shan Lu Liu

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Abstract

Jaagsiekte sheep retrovirus (JSRV) and enzootic nasal tumor virus (ENTV) are two closely related oncogenic retroviruses that share the same cellular receptor yet exhibit distinct fusogenicity and infectivity. Here, we find that the low fusogenicity of ENTV envelope protein (Env) is not because of receptor binding, but lies in its intrinsic insensitivity to receptor-mediated triggering for fusion at low pH. Distinct from JSRV, shedding of ENTV surface (SU) subunit into culture medium was not enhanced by a soluble form of receptor, Hyal2 (sHyal2), and sHyal2 was unable to effectively inactivate the ENTV pseudovirions. Remarkably, replacing either of the two amino acid residues, N191 or S195, located in the ENTV SU with the corresponding JSRV residues, H191 or G195, markedly increased the Env-mediated membrane fusion activity and infection. Reciprocal amino acid substitutions also partly switched the sensitivities of ENTV and JSRV pseudovirions to sHyal2-mediated SU shedding and inactivation. While N191 is responsible for an extra N-linked glycosylation of ENTV SU relative to that of JSRV, S195 possibly forms a hydrogen bond with a surrounding amino acid residue. Molecular modeling of the pre-fusion structure of JSRV Env predicts that the segment of SU that contains H191 to G195 contacts the fusion peptide and suggests that the H191N and G195S changes seen in ENTV may stabilize its pre-fusion structure against receptor priming and therefore modulate fusion activation by Hyal2. In summary, our study reveals critical determinants in the SU subunits of JSRV and ENTV Env proteins that likely regulate their local structures and thereby differential receptor-mediated fusion activation at low pH, and these findings explain, at least in part, their distinct viral infectivity.

Original languageEnglish (US)
Pages (from-to)173-183
Number of pages11
JournalVirology
Volume421
Issue number2
DOIs
StatePublished - Dec 20 2011

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Jaagsiekte sheep retrovirus
Oncogenic Viruses
Retroviridae
Nose
Sheep
Infection
env Gene Products
Viral Envelope Proteins
Amino Acids
Membrane Fusion
Amino Acid Substitution
Glycosylation
Culture Media
Hydrogen
Peptides

All Science Journal Classification (ASJC) codes

  • Virology

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Single residues in the surface subunits of oncogenic sheep retrovirus envelopes distinguish receptor-mediated triggering for fusion at low pH and infection. / Côté, Marceline; Zheng, Yi Min; Albritton, Lorraine; Liu, Shan Lu.

In: Virology, Vol. 421, No. 2, 20.12.2011, p. 173-183.

Research output: Contribution to journalArticle

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