title: Effect of Glycosylation on an Immunodominant Region in the V1V2 Variable Domain of the HIV-1 Envelope gp120 Protein.
abstract: Heavy glycosylation of the envelope (Env) surface subunit, gp120, is a key adaptation of HIV-1; however, the precise effects of glycosylation on the folding, conformation and dynamics of this protein are poorly understood. Here we explore the patterns of HIV-1 Env gp120 glycosylation, and particularly the enrichment in glycosylation sites proximal to the disulfide linkages at the base of the surface-exposed variable domains. To dissect the influence of glycans on the conformation these regions, we focused on an antigenic peptide fragment from a disulfide bridge-bounded region spanning the V1 and V2 hyper-variable domains of HIV-1 gp120. We used replica exchange molecular dynamics (MD) simulations to investigate how glycosylation influences its conformation and stability. Simulations were performed with and without N-linked glycosylation at two sites that are highly conserved across HIV-1 isolates (N156 and N160); both are contacts for recognition by V1V2-targeted broadly neutralizing antibodies against HIV-1. Glycosylation stabilized the pre-existing conformations of this peptide construct, reduced its propensity to adopt other secondary structures, and provided resistance against thermal unfolding. Simulations performed in the context of the Env trimer also indicated that glycosylation reduces flexibility of the V1V2 region, and provided insight into glycan-glycan interactions in this region. These stabilizing effects were influenced by a combination of factors, including the presence of a disulfide bond between the Cysteines at 131 and 157, which increased the formation of beta-strands. Together, these results provide a mechanism for conservation of disulfide linkage proximal glycosylation adjacent to the variable domains of gp120 and begin to explain how this could be exploited to enhance the immunogenicity of those regions. These studies suggest that glycopeptide immunogens can be designed to stabilize the most relevant Env conformations to focus the immune response on key neutralizing epitopes.
authors.affiliation: Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America.|Center for Biomolecular Biophysics, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America.
authors.forename: Jianhui
authors.initials: J
authors.lastname: Tian
authors.affiliation: Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America.
authors.forename: Cesar A
authors.initials: CA
authors.lastname: López
authors.affiliation: Department of Pathology and Laboratory Medicine and Emory Vaccine Center, Emory University, Atlanta, Georgia, United States of America.
authors.forename: Cynthia A
authors.initials: CA
authors.lastname: Derdeyn
authors.affiliation: University of California Berkeley, School of Public Health, Berkeley, California, United States of America.
authors.forename: Morris S
authors.initials: MS
authors.lastname: Jones
authors.affiliation: New Jersey Medical School, Rutgers University, Newark, New Jersey, United States of America.
authors.forename: Abraham
authors.initials: A
authors.lastname: Pinter
authors.affiliation: Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America.
authors.forename: Bette
authors.initials: B
authors.lastname: Korber
authors.affiliation: Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America.
authors.forename: S
authors.initials: S
authors.lastname: Gnanakaran
mesh_terms: D001665:Binding Sites; D006031:Glycosylation; D015699:HIV Envelope Protein gp120 / Q000737:chemistry* / Q000276:immunology*; D016056:Immunodominant Epitopes / Q000276:immunology*; D062105:Molecular Docking Simulation / Q000379:methods; D011485:Protein Binding; D000072417:Protein Domains / Q000276:immunology; D057127:Single-Chain Antibodies / Q000737:chemistry* / Q000276:immunology*
chemical_list: D015699:HIV Envelope Protein gp120; D016056:Immunodominant Epitopes; D057127:Single-Chain Antibodies; C514793:gp120 protein, Human immunodeficiency virus 1