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Unbiased cleavage site prediction uncovers viral antagonism of host innate immunity by SARS-CoV-2 3C-like protease
Nora Yucel, Silvia Marchiano, Evan Tchelepi, Germana Paterlini, Ivan A. Kuznetsov, Kristina Li, Quentin McAfee, Nehaar Nimmagadda, Andy Ren, Sam Shi, Alyssa Grogan, Aikaterini Kontrogianni-Konstantopoulos, Charles Murry, Zoltan Arany
Nora Yucel, Silvia Marchiano, Evan Tchelepi, Germana Paterlini, Ivan A. Kuznetsov, Kristina Li, Quentin McAfee, Nehaar Nimmagadda, Andy Ren, Sam Shi, Alyssa Grogan, Aikaterini Kontrogianni-Konstantopoulos, Charles Murry, Zoltan Arany
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Research Article COVID-19 Virology

Unbiased cleavage site prediction uncovers viral antagonism of host innate immunity by SARS-CoV-2 3C-like protease

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Abstract

How SARS-CoV-2 causes a wide range of clinical manifestations and disease severity remains poorly understood. SARS-CoV-2 encodes 2 proteases (3CLPro and PLPro), vital for viral production, but also promiscuous with respect to host protein targets. Pharmacological inhibition of 3CLPro markedly reduced hospitalization and death in Phase 2/3 clinical studies. Here, we develop a bioinformatic algorithm, leveraging experimental data from SARS-CoV, to predict host cleavage targets of 3CLPro. We capture targets of 3CLPro described previously for SARS-CoV-2, as well as thousands of putative targets. We validate numerous targets cleaved during infection, including the giant sarcomeric protein obscurin and the innate immune protein OAS1. A long form of OAS1, p46, has been associated in numerous GWAS studies with lesser COVID disease severity. We show that 3CLPro cleaves p46 OAS1 immediately upstream of a known prenylation domain, relocalizing OAS1 from subcellular membranes to the cytosol, rendering it akin to the nonprotective, cytosolic p42 isoform. Similar OAS1 relocalization occurs upon infection by SARS-CoV-2. Our data provide a high-throughput resource to identify putative host cleavage targets of 3CLPro and reveal a mechanism by which SARS-CoV-2 antagonizes host innate immunity in individuals with the protective p46 isoform of OAS1.

Authors

Nora Yucel, Silvia Marchiano, Evan Tchelepi, Germana Paterlini, Ivan A. Kuznetsov, Kristina Li, Quentin McAfee, Nehaar Nimmagadda, Andy Ren, Sam Shi, Alyssa Grogan, Aikaterini Kontrogianni-Konstantopoulos, Charles Murry, Zoltan Arany

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Figure 4

Obscurin cleavage with 3CLPro expression.

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Obscurin cleavage with 3CLPro expression.
(A) Schematic of Obscurin doma...
(A) Schematic of Obscurin domain structure (generated from accession #NP_001258152.2/Unitprot ID A6NGQ3) with overlayed predicted cleavage sites (based on “canonical” UniProt Q5VST9 sequence) and predicted ~150 kDa fragment arising from Q4075 and Q5488 cleavage events. In red are cut-site locations based on the canonical sequence Q5VST9; in blue are the locations based on A6NGQ3. Epitope regions for antibodies used for this study are labeled 1–5. (B) Obscurin expression after 72 hours of 3CLPro or catalytically inactive C145A. Western blots are shown for all 5 obscurin antibodies, as well as ACTN2 and MYH6 as sarcomeric protein controls run on tris-acetate gels. 14-3-3 shown as loading control, as well as StrepTagII to mark 3CL/C145A expression, with proteins run separately on standard tris-glycine based gels. (C) Quantification of blots shown in B, normalized by ACTN2 staining run for each obscurin blot on the same membrane. Significance determined by Ordinary 2-way ANOVA with Šidák’s multiple-comparison test. N = 3 biological replicates. (D) Immunocytochemistry for obscurin and ACTN2 after 48 hours overexpression of 3CLPro or catalytically inactive C145A. Scale bar: 10 μm. (E) Expression of cleavage targets following expression of 3CLPro or catalytically inactive C145A. Following 24 hours of overexpression, MG132 (1 μM) or vehicle was added for 24 hours for a total of 48 hours overexpression with or without MG132. Fragments are highlighted for OBSCN, TAB1, and SVIL. Location of the obscurin fragment is underlined in black in the schematic in A. MYH6 shown as an loading control, Ubiquitin shown to demonstrate efficacy of MG132 addition, and StrepTagII staining shown to indicate 3CL or C145A expression.

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