8uk3
The rotavirus VP5*/VP8* conformational transition permeabilizes membranes to Ca2+ (class 6 reconstruction)
Structural highlights
FunctionVP4_ROTRH Spike-forming protein that mediates virion attachment to the host epithelial cell receptors and plays a major role in cell penetration, determination of host range restriction and virulence. It is subsequently lost, together with VP7, following virus entry into the host cell. Rotavirus attachment and entry into the host cell probably involves multiple sequential contacts between the outer capsid proteins VP4 and VP7, and the cell receptors. In sialic acid-dependent and/or integrin-dependent strains, VP4 seems to essentially target sialic acid and/or the integrin heterodimer ITGA2/ITGB1.[1] Outer capsid protein VP5*: forms the spike "foot" and "body". Acts as a membrane permeabilization protein that mediates release of viral particles from endosomal compartments into the cytoplasm. In integrin-dependent strains, VP5* targets the integrin heterodimer ITGA2/ITGB1 for cell attachment.[2] VP8* forms the head of the spikes. It is the viral hemagglutinin and an important target of neutralizing antibodies. In sialic acid-dependent strains, VP8* binds to host cell sialic acid, most probably a ganglioside, providing the initial contact.[3] Publication Abstract from PubMedRotaviruses infect cells by delivering into the cytosol a transcriptionally active inner capsid particle (a "double-layer particle": DLP). Delivery is the function of a third, outer layer, which drives uptake from the cell surface into small vesicles from which the DLPs escape. In published work, we followed stages of rhesus rotavirus (RRV) entry by live-cell imaging and correlated them with structures from cryogenic electron microscopy and tomography (cryo-EM and cryo-ET). The virus appears to wrap itself in membrane, leading to complete engulfment and loss of Ca2+ from the vesicle produced by the wrapping. One of the outer-layer proteins, VP7, is a Ca2+-stabilized trimer; loss of Ca2+ releases both VP7 and the other outer-layer protein, VP4, from the particle. VP4, activated by cleavage into VP8* and VP5*, is a trimer that undergoes a large-scale conformational rearrangement, reminiscent of the transition that viral fusion proteins undergo to penetrate a membrane. The rearrangement of VP5* thrusts a 250-residue, C-terminal segment of each of the three subunits outward, while allowing the protein to remain attached to the virus particle and to the cell being infected. We proposed that this segment inserts into the membrane of the target cell, enabling Ca2+ to cross. In the work reported here, we show the validity of key aspects of this proposed sequence. By cryo-EM studies of liposome-attached virions ("triple-layer particles": TLPs) and single-particle fluorescence imaging of liposome-attached TLPs, we confirm insertion of the VP4 C-terminal segment into the membrane and ensuing generation of a Ca2+ "leak". The results allow us to formulate a molecular description of early events in entry. We also discuss our observations in the context of other work on double-strand RNA virus entry. The rotavirus VP5*/VP8* conformational transition permeabilizes membranes to Ca2.,de Sautu M, Herrmann T, Scanavachi G, Jenni S, Harrison SC PLoS Pathog. 2024 Apr 4;20(4):e1011750. doi: 10.1371/journal.ppat.1011750. , eCollection 2024 Apr. PMID:38574119[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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