Role of SARS-CoV viroporins E, 3a and 8a in virus replication and virulence: complementation between the PBMs of E and 3a proteins

Abstract

Severe acute respiratory syndrome coronavirus (SARS-CoV) causes lethal disease in humans, which is characterized by exacerbated inflammatory response and extensive lung pathology. In addition to protein components, viral genomes can also encode non-coding RNAs (ncRNAs) differing in size, biogenesis, and function, which are not necessarily comparable to those produced by host cells. To address the relevance of small non-coding RNAs in SARS-CoV pathology, we deep sequenced RNAs from the lungs of infected mice, which reproduce the pulmonary pathology observed in humans. Recombinant SARS-CoV (rSARS-CoV) variants lacking each of these proteins have been engineered. Analysis of the deletion mutantsshowed that none of themwere essential for virus replication, and that proteins 3a and E were relevant in virulence. In contrast, a virus simultaneously missing 3a and E genes could not be rescued suggesting a complementation between proteins 3a and E for virus viability. At least two activities are shared by these two viroporins: ion channel (IC) and PDZ binding motif (PBM).PBMs can potentially bind over 400 cellular proteins containing PDZ domains conferring high relevance to PBM motifs in the control of cell behaviour. In the present work, we studied whether 3a and E protein IC activities or PBMswere responsible for this complementation. In order to construct rSARS-CoV without 3a or E protein IC activity, the amino acids involved in this activity were determined and rSARS-CoVs missing E or 3a proteins IC conductancewere constructed.