Absence of E protein arrests transmissible gastroenteritis coronavirus maturation in the secretory pathway

Abstract

A recombinant transmissible gastroenteritis coronavirus (rTGEV) in which E gene was deleted (rTGEV-DeltaE) has been engineered. This deletion mutant only grows in cells expressing E protein (E(+) cells) indicating that E was an essential gene for TGEV replication. Electron microscopy studies of rTGEV-DeltaE infected BHK-pAPN-E(-) cells showed that only immature intracellular virions were assembled. These virions were non-infectious and not secreted to the extracellular medium in BHK-pAPN-E(-) cells. RNA and protein composition analysis by RNase-gold and immunoelectron microscopy showed that rTGEV-DeltaE virions contained RNA and also all the structural TGEV proteins, except the deleted E protein. Nevertheless, full virion maturation was blocked. Studies of the rTGEV-DeltaE subcellular localization by confocal and immunoelectron microscopy in infected E(-) cells showed that in the absence of E protein virus trafficking was arrested in the intermediate compartment. Therefore, the absence of E protein in TGEV resulted in two actions, a blockade of virus trafficking in the membranes of the secretory pathway, and prevention of full virus maturation.

Supramolecular Architecture of the Coronavirus Particle

“…The 229E-4a accessory protein also has ion channel activity, but it is not known whether this can compensate for deletion of E (Zhang et al, 2014). In contrast, deletion of E in TGEV prevented the formation of infectious virions (Ortego et al, 2007).…”

Antigen delivery systems for veterinary vaccine development

“…In the absence of E protein immature TGEV particles of a size slightly larger than the mature viruses were formed. These particles were not released to the supernatants of infected cultures, whereas infectious viruses were assembled in packaging cell lines providing the E protein in trans [286]. The ability to generate TGEV-E mutants that are replication-competent but propagation-deficient by complementation in packaging cell lines, supports the potential use of coronavirus as vaccine vectors.…”

Deciphering the biology of porcine epidemic diarrhea virus in the era of reverse genetics

“…The S protein mediates specific receptor binding and membrane fusion to facilitate viral entry and contains major antigenic epitopes for neutralizing antibodies against PEDV (Sun et al, 2007). The E protein is a membrane protein which has been found to play a role in viral budding in other coronaviruses (Ortego et al, 2007), while the M protein plays a role in viral assembly (de Haan et al, 2000). Coronavirus N proteins bind viral RNA, providing structural scaffolding for viral transcription, replication and assembly (McBride et al, 2014).…”