title: Crystal structure of herpes simplex virus 2 gD bound to nectin-1 reveals a conserved mode of receptor recognition.
abstract: Herpes simplex virus 1 (HSV-1) and HSV-2 are among the most prevalent human pathogens. Both viruses can recognize, via the surface envelope glycoprotein D (gD), human nectin-1 as a functional receptor. Previous studies have successfully elucidated the molecular basis of the binding between HSV-1 gD and nectin-1 by cocrystallography. Despite a high sequence identity between HSV-1 and HSV-2 gDs, the atomic intermolecule details for the HSV-2-gD/nectin-1 interaction remain elusive. Here, we report the crystal structures of both the unbound and the nectin-1-bound HSV-2 gDs. The free-gD structure expectedly comprises an IgV-like core and the surface-exposed terminal extensions as observed in its HSV-1 counterpart but lacks traceable electron densities for a large portion of the terminal elements. These terminal residues were clearly traced in the complex structure as a definitive loop in the N terminus and an α-helix in the C terminus, thereby showing a conserved nectin-1-binding mode as reported for HSV-1 gD. The interface residues in nectin-1 were further mutated and tested for the gD interaction by surface plasmon resonance. The resultant binding patterns were similar for HSV-1 and HSV-2 gDs, further supporting a homologous receptor-binding basis by the two viruses for nectin-1. These data, together with a cell-based fusion assay showing a cross-inhibition of the gD/nectin-1-mediated cell-cell fusion by soluble HSV-1 and HSV-2 gDs, provided solid structural and functional evidence that HSV-1 and HSV-2 recognize nectin-1 via the same binding mode. Finally, we also demonstrated that nectin-1 I80 is an important residue involved in gD interaction.
  
  
  OBJECTIVE
  Despite intensified studies, a detailed picture of the molecular features in the HSV-2-gD/nectin-1 interaction remains unavailable. Previous work focused on HSV-1 gD, which folds into an IgV-like core with large terminal extensions and utilizes the extension elements to engage nectin-1. Here, we report the crystal structures of HSV-2 gD in both the free and the nectin-1-bound forms. The atomic intermolecule details for HSV-2-gD/nectin-1 interaction are clearly presented. The observed binding mode is identical to that reported for its HSV-1 counterpart. This structural observation was further supported by our comparative functional assays showing that nectin-1 mutations similarly affect the ligand-receptor interaction of both virus gDs. Taken together, we provide comprehensive structural and functional data demonstrating a conserved receptor-binding mode between HSV-1 and HSV-2 for nectin-1. Our results also indicate that the tropism difference between the two viruses likely arises from aspects other than the gD/nectin-1 binding features.
authors.affiliation: CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Guangwen
authors.initials: G
authors.lastname: Lu
authors.affiliation: CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Na
authors.initials: N
authors.lastname: Zhang
authors.affiliation: CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Jianxun
authors.initials: J
authors.lastname: Qi
authors.affiliation: CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.affiliation: CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Zhujun
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Soochow University, Institutes of Biology and Medical Sciences, Suzhou, China.
authors.forename: Chunfu
authors.initials: C
authors.lastname: Zheng
authors.affiliation: CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China Laboratory of Protein Engineering and Vaccines, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China Research Network of Immunity and Health (RNIH), Beijing Institutes of Life Science, Chinese Academy of Sciences, Beijing, China Office of Director-General, Chinese Center for Disease Control and Prevention (China CDC), Beijing, China.
authors.forename: George F
authors.initials: GF
authors.lastname: Gao
authors.affiliation: CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China yanjh@im.ac.cn.
authors.forename: Jinghua
authors.initials: J
authors.lastname: Yan
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D016466:CHO Cells; D015815:Cell Adhesion Molecules / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003412:Cricetulus; D018360:Crystallography, X-Ray; D004252:DNA Mutational Analysis; D018258:Herpesvirus 2, Human; D006801:Humans; D000075983:Nectins; D011485:Protein Binding; D011487:Protein Conformation; D011991:Receptors, Virus / Q000737:chemistry* / Q000378:metabolism; D020349:Surface Plasmon Resonance; D014759:Viral Envelope Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D015815:Cell Adhesion Molecules; C000619010:NECTIN1 protein, human; D000075983:Nectins; D011991:Receptors, Virus; D014759:Viral Envelope Proteins; C040570:glycoprotein D-herpes simplex virus type 2