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PLoS Pathog . Thiopurines inhibit coronavirus Spike protein processing and incorporation into progeny virions

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  • PLoS Pathog . Thiopurines inhibit coronavirus Spike protein processing and incorporation into progeny virions


    PLoS Pathog


    . 2022 Sep 19;18(9):e1010832.
    doi: 10.1371/journal.ppat.1010832. Online ahead of print.
    Thiopurines inhibit coronavirus Spike protein processing and incorporation into progeny virions


    Eric S Pringle 1 , Brett A Duguay 1 , Maxwell P Bui-Marinos 2 3 , Rory P Mulloy 2 3 , Shelby L Landreth 4 5 , Krishna Swaroop Desireddy 6 , Stacia M Dolliver 1 , Shan Ying 1 , Taylor Caddell 1 , Trinity H Tooley 1 , Patrick D Slaine 1 , Stephen L Bearne 6 7 , Darryl Falzarano 4 5 , Jennifer A Corcoran 2 3 , Denys A Khaperskyy 1 , Craig McCormick 1



    Affiliations

    Abstract

    There is an outstanding need for broadly acting antiviral drugs to combat emerging viral diseases. Here, we report that thiopurines inhibit the replication of the betacoronaviruses HCoV-OC43 and SARS-CoV-2. 6-thioguanine (6-TG) disrupted early stages of infection, limiting accumulation of full-length viral genomes, subgenomic RNAs and structural proteins. In ectopic expression models, we observed that 6-TG increased the electrophoretic mobility of Spike from diverse betacoronaviruses, matching the effects of enzymatic removal of N-linked oligosaccharides from Spike in vitro. SARS-CoV-2 virus-like particles (VLPs) harvested from 6-TG-treated cells were deficient in Spike. 6-TG treatment had a similar effect on production of lentiviruses pseudotyped with SARS-CoV-2 Spike, yielding pseudoviruses deficient in Spike and unable to infect ACE2-expressing cells. Together, these findings from complementary ectopic expression and infection models strongly indicate that defective Spike trafficking and processing is an outcome of 6-TG treatment. Using biochemical and genetic approaches we demonstrated that 6-TG is a pro-drug that must be converted to the nucleotide form by hypoxanthine phosphoribosyltransferase 1 (HPRT1) to achieve antiviral activity. This nucleotide form has been shown to inhibit small GTPases Rac1, RhoA, and CDC42; however, we observed that selective chemical inhibitors of these GTPases had no effect on Spike processing or accumulation. By contrast, the broad GTPase agonist ML099 countered the effects of 6-TG, suggesting that the antiviral activity of 6-TG requires the targeting of an unknown GTPase. Overall, these findings suggest that small GTPases are promising targets for host-targeted antivirals.


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