Abstract
Flavivirus envelope protein (E) mediates membrane fusion and viral entry from endosomes. A low-pH induced, dimer-to-trimer rearrangement and reconfiguration of the membrane-proximal “stem" of the E ectodomain draw together the viral and cellular membranes. We found stem-derived peptides from dengue virus (DV) bind stem-less E trimer and mimic the stem-reconfiguration step in the fusion pathway. We adapted this experiment as a high-throughput screen for small molecules that block peptide binding and thus may inhibit viral entry. A compound identified in this screen, 1662G07, and a number of its analogs reversibly inhibit DV infectivity. They do so by binding the prefusion, dimeric E on the virion surface, before adsorption to a cell. They also block viral fusion with liposomes. Structure-activity relationship studies have led to analogs with submicromolar IC90s against DV2, and certain analogs are active against DV serotypes 1,2, and 4. The compounds do not inhibit the closely related Kunjin virus. We propose that they bind in a previously identified, E-protein pocket, exposed on the virion surface and although this pocket is closed in the postfusion trimer, its mouth is fully accessible. Examination of the E-trimer coordinates (PDB 1OK8) shows that conformational fluctuations around the hinge could open the pocket without dissociating the trimer or otherwise generating molecular collisions. We propose that compounds such as 1662G07 trap the sE trimer in a “pocket-open" state, which has lost affinity for the stem peptide and cannot support the final “zipping up" of the stem.
Highlights
Enveloped viruses penetrate into the cytosol of their target cell by fusion of viral and cellular membranes [1,2]
Fusion of viral and cellular membranes is necessary to establish infection by an enveloped virus. This process is facilitated by rearrangement of protein(s) present on the virion surface in response to molecular cues from the compartment from which fusion occurs, such as low pH of an endosome
We previously showed that peptides derived from the membrane proximal ‘‘stem’’ of the E protein bind a form of E that represents a late-stage fusion intermediate
Summary
Enveloped viruses penetrate into the cytosol of their target cell by fusion of viral and cellular membranes [1,2]. Flaviviruses, such as dengue, penetrate from endosomes, following uptake by clathrin-mediated endocytosis [3,4]. At endosomal pH, proton binding by their envelope protein, E, triggers a fusion-promoting conformation change [5,6]. The three domains (DI–III) of the E protein reorient with respect to one other during the fusion-promoting conformational transition, which includes dissociation of the prefusion dimer and reconfiguration of the subunits into trimers [2]. The driving force for pinching the two membranes together appears to come from contacts made by domain III, as it folds back against domain I, and by the stem, as it ‘‘zips’’ up along adjacent domain II monomers [1,2]
Sign-in/Register to view highlights & summary 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 callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
