tetano
Editor, Senior Moderator
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[SUP] 1 [/SUP], Brett A Duguay[SUP] 1 [/SUP], Maxwell P Bui-Marinos[SUP] 2 3 [/SUP], Rory P Mulloy[SUP] 2 3 [/SUP], Shelby L Landreth[SUP] 4 5 [/SUP], Krishna Swaroop Desireddy[SUP] 6 [/SUP], Stacia M Dolliver[SUP] 1 [/SUP], Shan Ying[SUP] 1 [/SUP], Taylor Caddell[SUP] 1 [/SUP], Trinity H Tooley[SUP] 1 [/SUP], Patrick D Slaine[SUP] 1 [/SUP], Stephen L Bearne[SUP] 6 7 [/SUP], Darryl Falzarano[SUP] 4 5 [/SUP], Jennifer A Corcoran[SUP] 2 3 [/SUP], Denys A Khaperskyy[SUP] 1 [/SUP], Craig McCormick[SUP] 1 [/SUP]
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.
. 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[SUP] 1 [/SUP], Brett A Duguay[SUP] 1 [/SUP], Maxwell P Bui-Marinos[SUP] 2 3 [/SUP], Rory P Mulloy[SUP] 2 3 [/SUP], Shelby L Landreth[SUP] 4 5 [/SUP], Krishna Swaroop Desireddy[SUP] 6 [/SUP], Stacia M Dolliver[SUP] 1 [/SUP], Shan Ying[SUP] 1 [/SUP], Taylor Caddell[SUP] 1 [/SUP], Trinity H Tooley[SUP] 1 [/SUP], Patrick D Slaine[SUP] 1 [/SUP], Stephen L Bearne[SUP] 6 7 [/SUP], Darryl Falzarano[SUP] 4 5 [/SUP], Jennifer A Corcoran[SUP] 2 3 [/SUP], Denys A Khaperskyy[SUP] 1 [/SUP], Craig McCormick[SUP] 1 [/SUP]
Affiliations
- PMID: 36121863
- DOI: 10.1371/journal.ppat.1010832
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.