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SARS-CoV-2 papain-like protease (PLpro) plays multiple roles in regulating cellular proteins in the endoplasmic reticulum

ABSTRACT: Nsp3s are the largest non-structural proteins of coronaviruses. These transmembrane proteins include a papain-like protease (PLpro) that plays essential roles in cleaving viral polyproteins into their mature units. The PLpro of SARS-CoV viruses also have deubiquitinating and deISGylating activities. As Nsp3 is an endoplasmic reticulum (ER)-localized protein, we asked if the deubiquitinating activity of SARS-CoV-2 PLpro affects proteins that are substrates for ER-associated degradation (ERAD). Using full-length Nsp3 as well as a truncated transmembrane form we interrogated, by co-expression, three potential ERAD substrates, all of which play roles in regulating lipid biosynthesis. Transmembrane PLpro increased the level of INSIG-1 and decreased its ubiquitination. However, different effects were seen with SREBP-1 and SREBP-2. When co-expressed, transmembrane PLpro cleaves SREBP-1 at three sites, including two non-canonical sites in the N terminal half of the protein, resulting in a decrease in precursors of the active transcription factor. Conversely, cleavage of SREBP-2 occurs at a single canonical site that disrupts a C-terminal degron, resulting in increased SREBP-2 levels. When this site is mutated and the degron can no longer be interrupted, SREBP-2 is still stabilized by transmembrane PLpro, which correlates with a decrease in SREBP-2 ubiquitination. All of these observations are dependent on PLpro catalytic activity. Our findings demonstrate that, when anchored to the ER membrane, SARS-CoV-2 Nsp3 PLpro can function as a deubiquitinating enzyme to stabilize ERAD substrates. Additionally, SARS-CoV-2 Nsp3 PLpro can cleave ER resident proteins, including at sites that could escape analyses based on the established consensus sequence.

INSTRUMENT(S): Orbitrap Fusion Lumos, Q Exactive HF

ORGANISM(S): Homo Sapiens (ncbitaxon:9606)

SUBMITTER: Allan M. Weissman

PROVIDER: MSV000092963 | MassIVE |

REPOSITORIES: MassIVE

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SARS-CoV-2 papain-like protease (PLpro) plays multiple roles in regulating cellular proteins in the endoplasmic reticulum

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