A short sequence in the tail of SARS-CoV-2 envelope protein controls accessibility of its PDZ Binding Motif to the cytoplasm. (preprint)

The carboxy terminal tail of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) envelope protein (E) contains a PDZ-binding motif (PBM) which is crucial for coronavirus pathogenicity. During SARS-CoV-2 infection, the viral E protein is expressed within the Golgi apparatus membrane of host cells with its PBM facing the cytoplasm. In this work we study the molecular mechanisms controlling the presentation of the PBM to host PDZ (PSD-95/Dlg/ZO-1) domain-containing proteins. We show that at the level of the Golgi apparatus, the PDZ-binding motif of the E protein is not detected by E C-terminal specific antibodies neither by PDZ domain-containing protein binding partner. Four alanine substitutions upstream of the PBM in the central region of the E protein tail is sufficient to generate immunodetection by anti-E antibodies and trigger robust recruitment of the PDZ domain-containing protein into the Golgi organelle. Overall, this work suggests that the presentation of the PBM to the cytoplasm is under conformational regulation mediated by the central region of the E protein tail and that PBM presentation probably does not occur at the surface of Golgi cisternae but likely at post-Golgi stages of the viral cycle.

Neuroinvasion and anosmia are independent phenomena upon infection with SARS-CoV-2 and its variants (preprint)

Anosmia was identified as a hallmark of COVID-19 early in the pandemic, however, with the emergence of variants of concern, the clinical profile induced by SARS-CoV-2 infection has changed, with anosmia being less frequent. Several studies have focused on the neuropathogenesis of the original SARS-CoV-2, but little is known about the neuropathological potential of the variants. Here, we assessed the clinical, olfactory and inflammatory conditions of golden hamsters infected with the original SARS-CoV-2, its ORF7-deleted mutant, and three variants: Gamma, Delta and Omicron/BA.1. We show that infected animals developed a variant-dependent clinical disease, and that the ORF7 of SARS-CoV-2 contribute to causing olfactory disturbances. Conversely, all SARS-CoV-2 variants were found to be neuroinvasive, regardless of the clinical presentation they induce. With newly-generated nanoluciferase-expressing SARS-CoV-2, we validated the olfactory pathway as a main entry point towards the brain, confirming that neuroinvasion and anosmia are independent phenomena upon SARS-CoV-2 infection.

Interactions of SARS-CoV-2 protein E with cell junctions and polarity PDZ-containing proteins (preprint)

The C-terminus of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) protein E contains a PBM (PDZ binding motif) targeting PDZ (PSD-95/Dlg/ZO-1) domains identical to the PBM of SARS-CoV. The latter is involved in the pathogenicity of the virus. Recently, we identified ten human PDZ-containing proteins showing significant interactions with SARS-CoV-2 protein E PBM. We selected several of them involved in cellular junctions and cell polarity (TJP1, PARD3, MLLT4, LNX2) and MPP5/Pals1 previously shown to interact with SARS-CoV E PBM. Targeting cellular junctions and polarity components is a common strategy by viruses to hijack cell machinery to their advantage. In this study, we showed that these host PDZ domains TJP1, PARD3, MLLT4, LNX2 and MPP5/PALS1 interact in a PBM-dependent manner in vitro and colocalize with the full-length E protein in cellulo, sequestrating the PDZ domains to the Golgi compartment. We solved three crystal structures of complexes between human LNX2, MLLT4 and MPP5 PDZs and SARS-CoV-2 E PBM highlighting its binding preferences for several cellular targets. Finally, we showed different affinities for the PDZ domains with the original SARS-CoV-2 C-terminal sequence containing the PBM and the one of the beta variant that contains a mutation close to the PBM. The acquired mutations in E protein localized near the PBM might have important effects both on the structure and the ion-channel activity of the E protein and on the host machinery targeted by the variants during the infection.