Monomeric ephrinB2 binding induces allosteric changes in Nipah virus G that precede its full activation

Joyce J W Wong,Shiheng Liu,Z Hong Zhou,George P Leser,Joshua Salafsky,Robert A Lamb,Elizabeth A Komives,Jiayan Zhang,Theodore S Jardetzky,Tracy A Young

doi:10.1038/s41467-017-00863-3

Abstract

Nipah virus is an emergent paramyxovirus that causes deadly encephalitis and respiratory infections in humans. Two glycoproteins coordinate the infection of host cells, an attachment protein (G), which binds to cell surface receptors, and a fusion (F) protein, which carries out the process of virus-cell membrane fusion. The G protein binds to ephrin B2/3 receptors, inducing G conformational changes that trigger F protein refolding. Using an optical approach based on second harmonic generation, we show that monomeric and dimeric receptors activate distinct conformational changes in G. The monomeric receptor-induced changes are not detected by conformation-sensitive monoclonal antibodies or through electron microscopy analysis of G:ephrinB2 complexes. However, hydrogen/deuterium exchange experiments confirm the second harmonic generation observations and reveal allosteric changes in the G receptor binding and F-activating stalk domains, providing insights into the pathway of receptor-activated virus entry.

Highlights

Nipah virus is an emergent paramyxovirus that causes deadly encephalitis and respiratory infections in humans
An epitope immediately preceding the N-terminus of the Nipah virus G (NiV G) receptor-binding domain (RBD) recognized by monoclonal antibody mAb45 and a stalk domain epitope recognized by polyclonal antibody Ab167 become more tightly bound by their respective antibodies, while an epitope on the globular head domain recognized by monoclonal antibody mAb213 becomes less bound[13, 17]
To understand better the conformational changes induced in NiV G upon binding its host receptor ephrinB2, we explored the possibility of using second harmonic generation (SHG) to monitor G conformational states

Summary

Introduction

Nipah virus is an emergent paramyxovirus that causes deadly encephalitis and respiratory infections in humans. Nipah and Hendra viruses, which define the Henipavirus genus within the Paramyxoviridae, cause periodic outbreaks of encephalitic and respiratory illness in humans with high morbidity and mortality. Binding of ephrin B2/3 is thought to result in a series of rearrangements in the G tetramer that culminate in the exposure of stalk domain residues that activate F, but are occluded by the head domains in the untriggered state[11, 13, 14] These rearrangements are thought to involve changes in the quaternary structure of the G tetramer, as very little change occurs within the henipavirus G RBDs in crystal structures with ephrinB2 or B315, 16. The F-activating role of the exposed attachment protein stalk is supported by constitutive activation of paramyxovirus fusion with headless attachment protein constructs[13, 26,27,28], fusion activation by chimeric attachment proteins with heterotypic head domains and homotypic stalks[29] and the disruption of fusion by stalk domain mutants that modulate interactions with F30–32

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Results

Conclusion