title: Residues in the stalk domain of the hendra virus g glycoprotein modulate conformational changes associated with receptor binding.
abstract: Hendra virus (HeV) is a member of the broadly tropic and highly pathogenic paramyxovirus genus Henipavirus. HeV is enveloped and infects cells by using membrane-anchored attachment (G) and fusion (F) glycoproteins. G possesses an N-terminal cytoplasmic tail, an external membrane-proximal stalk domain, and a C-terminal globular head that binds the recently identified receptors ephrinB2 and ephrinB3. Receptor binding is presumed to induce conformational changes in G that subsequently trigger F-mediated fusion. The stalk domains of other attachment glycoproteins appear important for oligomerization and F interaction and specificity. However, this region of G has not been functionally characterized. Here we performed a mutagenesis analysis of the HeV G stalk, targeting a series of isoleucine residues within a hydrophobic alpha-helical domain that is well conserved across several attachment glycoproteins. Nine of 12 individual HeV G alanine substitution mutants possessed a complete defect in fusion-promotion activity yet were cell surface expressed and recognized by a panel of conformation-dependent monoclonal antibodies (MAbs) and maintained their oligomeric structure. Interestingly, these G mutations also resulted in the appearance of an additional electrophoretic species corresponding to a slightly altered glycosylated form. Analysis revealed that these G mutants appeared to adopt a receptor-bound conformation in the absence of receptor, as measured with a panel of MAbs that preferentially recognize G in a receptor-bound state. Further, this phenotype also correlated with an inability to associate with F and in triggering fusion even after receptor engagement. Together, these data suggest the stalk domain of G plays an important role in the conformational stability and receptor binding-triggered changes leading to productive fusion, such as the dissociation of G and F.
authors.affiliation: Department of Microbiology and Immunology, Uniformed Services University, Bethesda, MD 20814, USA. cbroder@usuhs.mil
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Bishop
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Hickey
authors.forename: Dimple
authors.initials: D
authors.lastname: Khetawat
authors.forename: Jared R
authors.initials: JR
authors.lastname: Patch
authors.forename: Katharine N
authors.initials: KN
authors.lastname: Bossart
authors.forename: Zhongyu
authors.initials: Z
authors.lastname: Zhu
authors.forename: Lin-Fa
authors.initials: LF
authors.lastname: Wang
authors.forename: Dimiter S
authors.initials: DS
authors.lastname: Dimitrov
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Broder
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000911:Antibodies, Monoclonal / Q000276:immunology; D000914:Antibodies, Viral / Q000276:immunology; D002459:Cell Fusion; D002460:Cell Line; D036388:Ephrin-B2 / Q000378:metabolism*; D036389:Ephrin-B3 / Q000378:metabolism*; D045404:Hendra Virus / Q000502:physiology*; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D011487:Protein Conformation; D016415:Sequence Alignment; D014759:Viral Envelope Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D036388:Ephrin-B2; D036389:Ephrin-B3; D014759:Viral Envelope Proteins; C116204:attachment protein G
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