Abstract
The hantavirus envelope glycoproteins Gn and Gc mediate virion assembly and cell entry, with Gc driving fusion of viral and endosomal membranes. Although the X-ray structures and overall arrangement of Gn and Gc on the hantavirus spikes are known, their detailed interactions are not. Here we show that the lateral contacts between spikes are mediated by the same 2-fold contacts observed in Gc crystals at neutral pH, allowing the engineering of disulfide bonds to cross-link spikes. Disrupting the observed dimer interface affects particle assembly and overall spike stability. We further show that the spikes display a temperature-dependent dynamic behavior at neutral pH, alternating between 'open' and 'closed' forms. We show that the open form exposes the Gc fusion loops but is off-pathway for productive Gc-induced membrane fusion and cell entry. These data also provide crucial new insights for the design of optimized Gn/Gc immunogens to elicit protective immune responses.
Highlights
Hantaviruses persistently infect rodents throughout the world
The ‘dimer’ interaction observed in the hantavirus Gc crystals is reminiscent of the crystallographic dimer contacts presented by class II alphavirus fusion protein E1 (Roussel et al, 2006), which is recapitulated by the 2-fold related contacts between hetero-hexameric (E2/E1)3 spikes at the surface of alphavirus particles (Sun et al, 2013; Voss et al, 2010) (Figure 1a)
To test whether the Gc:Gc interface observed in the crystallographic dimer is involved in contacts between adjacent spikes at the surface of hantavirus particles, we introduced cysteine substitutions of candidate Gc residues at the putative 2-fold interface, such that they could form inter-spike disulfide bonds
Summary
Hantaviruses (order Bunyavirales, family Hantaviridae, genus Orthohantavirus) persistently infect rodents throughout the world. Virion-like particles (VLPs) are formed when GPC is expressed in the absence of other viral proteins (Acuna et al, 2014), indicating an important role of the glycoproteins in virion budding and in cell exit of the progeny. Electron cryo-tomography (cryo-ET) data revealed spikes with volumes that can accommodate the molecular mass of (Gn/Gc) hetero-octamers, related by 2-fold symmetry axes oriented radially in the particle (Battisti et al, 2011; Huiskonen et al, 2010). A higher resolution 15.6 Acryo-ET map allowed the docking of the Gn ectodomain into the central lobes on the tetrameric spike, at the membrane distal side, and masking the Gc fusion loops, suggesting that the 2-fold related spike-spike interactions are made by the Gc moiety (Li et al, 2016).
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call