title: Tyrosine sulfation in the second variable loop (V2) of HIV-1 gp120 stabilizes V2-V3 interaction and modulates neutralization sensitivity.
abstract: Elicitation of broadly neutralizing antibodies is essential for the development of a protective vaccine against HIV-1. However, the native HIV-1 envelope adopts a protected conformation that conceals highly conserved sites of vulnerability from antibody recognition. Although high-definition structures of the monomeric core of the envelope glycoprotein subunit gp120 and, more recently, of a stabilized soluble gp140 trimer have been solved, fundamental aspects related to the conformation and function of the native envelope remain unresolved. Here, we show that the conserved central region of the second variable loop (V2) of gp120 contains sulfated tyrosines (Tys173 and Tys177) that in the CD4-unbound prefusion state mediate intramolecular interaction between V2 and the conserved base of the third variable loop (V3), functionally mimicking sulfated tyrosines in CCR5 and anti-coreceptor-binding-site antibodies such as 412d. Recombinant gp120 expressed in continuous cell lines displays low constitutive levels of V2 tyrosine sulfation, which can be enhanced markedly by overexpression of the tyrosyl sulfotransferase TPST2. In contrast, virion-associated gp120 produced by primary CD4(+) T cells is inherently highly sulfated. Consistent with a functional role of the V2 sulfotyrosines, enhancement of tyrosine sulfation decreased binding and neutralization of HIV-1 BaL by monomeric soluble CD4, 412d, and anti-V3 antibodies and increased recognition by the trimer-preferring antibodies PG9, PG16, CH01, and PGT145. Conversely, inhibition of tyrosine sulfation increased sensitivity to soluble CD4, 412d, and anti-V3 antibodies and diminished recognition by trimer-preferring antibodies. These results identify the sulfotyrosine-mediated V2-V3 interaction as a critical constraint that stabilizes the native HIV-1 envelope trimer and modulates its sensitivity to neutralization.
authors.affiliation: Laboratory of Immunoregulation and Bioinformatics and Computational Biosciences Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892.
authors.forename: Raffaello
authors.initials: R
authors.lastname: Cimbro
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Gallant
authors.forename: Michael A
authors.initials: MA
authors.lastname: Dolan
authors.forename: Christina
authors.initials: C
authors.lastname: Guzzo
authors.forename: Peng
authors.initials: P
authors.lastname: Zhang
authors.forename: Yin
authors.initials: Y
authors.lastname: Lin
authors.forename: Huiyi
authors.initials: H
authors.lastname: Miao
authors.forename: Donald
authors.initials: D
authors.lastname: Van Ryk
authors.forename: James
authors.initials: J
authors.lastname: Arthos
authors.forename: Inna
authors.initials: I
authors.lastname: Gorshkova
authors.forename: Patrick H
authors.initials: PH
authors.lastname: Brown
authors.forename: Darrell E
authors.initials: DE
authors.lastname: Hurt
authors.forename: Paolo
authors.initials: P
authors.lastname: Lusso
mesh_terms: D015153:Blotting, Western; D005434:Flow Cytometry; D057809:HEK293 Cells; D015699:HIV Envelope Protein gp120 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000235:genetics* / Q000276:immunology*; D006801:Humans; D009500:Neutralization Tests; D011487:Protein Conformation; D020349:Surface Plasmon Resonance; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D015699:HIV Envelope Protein gp120; C514793:gp120 protein, Human immunodeficiency virus 1; C005662:tyrosine O-sulfate; D014443:Tyrosine