Ribavirin is a guanosine analog and has a broad-spectrum antiviral activity against RNA viruses. Based on this, we aimed to show the anti-SARS-CoV-2 activity of this drug molecule via in vitro, in silico and molecular techniques. Ribavirin showed antiviral activity in Vero E6 cells following SARS-CoV-2 infection whereas the drug itself did not show any toxic effect over the concentration range tested. In silico analysis suggested that Ribarivin has a broad-spectrum impact on SARS-CoV-2, acting at different viral proteins. According to the detailed molecular techniques, Ribavirin was shown to decrease the expression of TMPRSS2 both at mRNA and protein levels 48 hours after treatment. The suppressive effect of Ribavirin in ACE2 protein expression was shown to be dependent on cell types. Finally, proteolytic activity assays showed that Ribavirin also showed an inhibitory effect on TMPRSS2 enzyme. Based on these results, we hypothesized that Ribavirin may inhibit the expression of TMPRSS2 by modulating the formation of inhibitory G-quadruplex structures at the TMPRSS2 promoter. As a conclusion, Ribavirin is a potential antiviral drug for the treatment against SARS-CoV-2, and it interferes with the effect of TMPRSS2 and ACE2 expression.

Ribavirin is a guanosine analog and has a broad-spectrum antiviral activity against RNA viruses. Based on this, we aimed to show the anti-SARS-CoV-2 activity of this drug molecule via in vitro, in silico and molecular techniques. Ribavirin showed antiviral activity in Vero E6 cells following SARS-CoV-2 infection. In silico analysis suggested that Ribarivin has a broad-spectrum impact on Vero E6 cells. According to the detailed molecular techniques, Ribavirin was shown to decrease TMPRSS2 expression both at mRNA and protein level 48 hours after treatment. The suppressive effect of Ribavirin in ACE2 protein expression was shown to be dependent on cell types. Finally, proteolytic activity assays showed that Ribavirin also showed an inhibitory effect on TMPRSS2 enzyme. As a conclusion, Ribavirin is a potential antiviral drug for the treatment against SARS-CoV-2, and it interferes with the effect of TMPRSS2 and ACE2 expression.

GPR56/ADGRG1 is an adhesion GPCR and mutations on this receptor cause cortical malformation due to the over-migration of neural progenitor cells on the brain surface. At the pial surface, GPR56 interacts with collagen III, induces Rho dependent activation through Gα12/13 and inhibits the neuronal migration. In human glioma cells, GPR56 inhibits cell migration through Gαq/11 dependent Rho pathway. GPR56-tetraspanin complex is known to couple with Gαq/11. GPR56 is an aGPCR that couples with various G proteins and signals through different downstream pathways. In this study, BFPP mutants disrupting GPR56 function but remain to be expressed on plasma membrane were used to study receptor signaling through Gα12, Gα13 and Gα11 with BRET biosensors. GPR56 showed coupling with all three G proteins and activated heterotrimeric G protein signaling upon stimulation with Stachel peptide. However, BFPP mutants showed different signaling defects for each G protein indicative of distinct activation and signaling properties of GPR56 for Gα12, Gα13 or Gα11. β-arrestin recruitment was also investigated following the activation of GPR56 with Stachel peptide using BRET biosensors. N-terminally truncated GPR56 showed enhanced β-arrestin recruitment, however neither wild-type receptor nor BFPP mutants gave any measurable recruitment upon Stachel stimulation, pointing different activation mechanisms for β-arrestin involvement.

GPR56/ADGRG1 is an adhesion G protein‐coupled receptor (GPCR) and mutations on this receptor cause cortical malformation due to the over‐migration of neural progenitor cells on brain surface. At pial surface, GPR56 interacts with collagen III, induces Rho‐dependent activation through Gα12/13 and inhibits the neuronal migration. In human glioma cells, GPR56 inhibits cell migration through Gαq/11‐dependent Rho pathway. GPR56‐tetraspanin complex is known to couple Gαq/11. GPR56 is an aGPCR that couples with various G proteins and signals through different downstream pathways. In this study, bilateral frontoparietal polymicrogyria (BFPP) mutants disrupting GPR56 function but remaining to be expressed on plasma membrane were used to study receptor signalling through Gα12, Gα13 and Gα11 with BRET biosensors. GPR56 showed coupling with all three G proteins and activated heterotrimeric G protein signalling upon stimulation with Stachel peptide. However, BFPP mutants showed different signalling defects for each G protein indicative of distinct activation and signalling properties of GPR56 for Gα12, Gα13 or Gα11. β‐arrestin recruitment was also investigated following the activation of GPR56 with Stachel peptide using BRET biosensors. N‐terminally truncated GPR56 showed enhanced β‐arrestin recruitment; however, neither wild‐type receptor nor BFPP mutants gave any measurable recruitment upon Stachel stimulation, pointing different activation mechanisms for β‐arrestin involvement.