Picornavirus RNA is protected from cleavage by ribonuclease during virion uncoating and transfer across cellular and model membranes

Abstract

Picornaviruses are non-enveloped RNA viruses that enter cells via receptor-mediated endocytosis. Because they lack an envelope, picornaviruses face the challenge of delivering their RNA genomes across the membrane of the endocytic vesicle into the cytoplasm to initiate infection. Currently, the mechanism of genome release and translocation across membranes remains poorly understood. Within the enterovirus genus, poliovirus, rhinovirus 2, and rhinovirus 16 have been proposed to release their genomes across intact endosomal membranes through virally induced pores, whereas one study has proposed that rhinovirus 14 releases its RNA following disruption of endosomal membranes. For the more distantly related aphthovirus genus (e.g. foot-and-mouth disease viruses and equine rhinitis A virus) acidification of endosomes results in the disassembly of the virion into pentamers and in the release of the viral RNA into the lumen of the endosome, but no details have been elucidated as how the RNA crosses the vesicle membrane. However, more recent studies suggest aphthovirus RNA is released from intact particles and the dissociation to pentamers may be a late event. In this study we have investigated the RNase A sensitivity of genome translocation of poliovirus using a receptor-decorated-liposome model and the sensitivity of infection of poliovirus and equine-rhinitis A virus to co-internalized RNase A. We show that poliovirus genome translocation is insensitive to RNase A and results in little or no release into the medium in the liposome model. We also show that infectivity is not reduced by co-internalized RNase A for poliovirus and equine rhinitis A virus. Additionally, we show that all poliovirus genomes that are internalized into cells, not just those resulting in infection, are protected from RNase A. These results support a finely coordinated, directional model of viral RNA delivery that involves viral proteins and cellular membranes.

Human Neonatal Fc Receptor Is the Cellular Uncoating Receptor for Enterovirus B

“…The same phenomenon was not observed in either free Echo 6 particles or the CD55-Echo 6 complex ( Figure 6A). To further confirm that FcRn mediates virus capsid uncoating, a receptor-decorated liposome model was used as designed for a PVR-induced poliovirus uncoating study (Groppelli et al, 2017;Tuthill et al, 2006). His-tagged FcRn or CD55 was incubated with nickel-charged liposomes to form receptor-decorated liposomes.…”

Promising approaches for the treatment and prevention of viral respiratory illnesses

“…48 Nonenveloped viruses, such as rhinovirus, release their genomes through a conformational shift of the capsid proteins accompanied by an expansion of the viral shell along with the opening of symmetry-related channels (pores) from which the genome is released (virus uncoating). 49,50 Various capsid-binding compounds against rhinoviruses have been tested (R and WIN series) without ultimate success. 51 Pleconaril, BTA798 (vapendavir), and pocapavir (V-073) are still under clinical evaluation.…”

Interacting motif networks located in hotspots associated with RNA release are conserved in Enterovirus capsids

“…The conformational changes that occur in the virus capsid during RNA release are known for several enteroviruses [7][8][9]16,17]. During uncoating the N terminus of VP1 and the VP4 protein are externalised from the capsid, with the consequent release of RNA.…”