C4PR_LIV: The SARS-CoV-2 ORF3C protein interactome in Vero cells

ABSTRACT: The SARS-CoV-2 genome encodes a multitude of accessory proteins. Using comparative genomic approaches, an additional accessory protein, ORF3c, has been predicted to be encoded within the ORF3a sgmRNA. Expression of ORF3c during infection has been confirmed independently by ribosome profiling. Despite ORF3c also being present in the 2002-2003 SARS-CoV, its function has remained unexplored. Here we show that ORF3c localises only to mitochondria during infection, where it inhibits innate immunity by restricting IFN-β production, but not NF-κB activation or JAK-STAT signalling downstream of type I IFN stimulation. We find that ORF3c acts after stimulation with cytoplasmic RNA helicases RIG-I or MDA5 or adaptor protein MAVS, but not after TRIF, TBK1 or phospho-IRF3 stimulation. ORF3c co-immunoprecipitates with the antiviral proteins MAVS and PGAM5 and induces MAVS cleavage by caspase-3. Unlike early lineage SARS-CoV-2 strains, delta variant strains lack intact ORF3c and do not cleave MAVS to the same extent. Together, these data provide insight into an uncharacterised mechanism of innate immune evasion by this important human pathogen. We suggest a model whereby ORF3c inhibits PGAM5-induced mitophagy and instead induces apoptosis, accompanied by caspase-3 activation. This repository contains data associated with the SARS-CoV-2 ORF3C SILAC AP-MS portions of this work.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Cercopithecus Aethiops (green Monkey) (grivet)

TISSUE(S): Permanent Cell Line Cell

DISEASE(S): Severe Acute Respiratory Syndrome

SUBMITTER: Ed Emmott  

LAB HEAD: Ed Emmott

PROVIDER: PXD037765 | Pride | 2023-10-08

REPOSITORIES: Pride