Interferon redundancy counteracts proteolytic inactivation by SARS-CoV-2 3CL main protease

Authors

Grin, P. M., de Jesus, H. C. R., Pablos, I., Kappelhoff, R., Butler, G. S., Charaf, B., Overall, C. M.

Abstract

Interferons (IFNs) are secreted during virus infection and induce antiviral responses through receptor-mediated phosphorylation of signal transducer and activator of transcription (STAT) proteins, leading to IFN-stimulated gene expression with antiviral activity. We previously reported that the SARS-CoV-2 main protease, 3CLpro, is secreted from infected cells through gasdermin D/E pores and retains proteolytic activity in human serum against extracellular substrates. Here, we show that 3CLpro selectively cleaves glycosylated IFN-L1, IFN-L2, and a rare naturally occurring variant of IFN-{gamma} (Arg160Gln), but does not cleave wild-type IFN-{gamma}, IFN-L3, IFN-L4, IFN-alpha proteins or IFN-{beta}. We identified sites of O-linked glycosylation of IFN-L1 at Thr137 and one or more threonines or serine in the sequence 24TSKPTTT30, and N-linked glycosylation at Asn65 that were indispensable for signaling. Unexpectedly, O-glycosylation was also required for the cleavage and inactivation of IFN-L1 by 3CLpro at two sites. Cleavage reduced STAT1 phosphorylation and impaired the induction of the IFN-stimulated proteins MX1, OAS2, and IFIT1. Although 3CLpro cleaved IFN-L2 proximal to its N-terminus at ARLH32{downarrow}GALP, cleavage neither disrupted signaling nor antiviral activity against SARS-CoV-2 and vesicular stomatitis virus. We further show that matrix metalloproteinases (MMPs) 2, 7, 8, and 12 degrade 3CLpro, whereas 3CLpro shows no activity against these MMPs.

Preprint server: bioRxiv
The authors list and abstract were imported from bioRxiv on 09 Sep 2026.

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