Facilitating SARS CoV-2 RNA-Dependent RNA polymerase (RdRp) drug discovery by the aid of HCV NS5B palm subdomain binders: In silico approaches and benchmarking.

Corona Virus 2019 Disease (COVID-19) is a rapidly emerging pandemic caused by a newly discovered beta coronavirus, called Sever Acute Respiratory Syndrome Coronavirus 2 (SARS CoV-2). SARS CoV-2 is an enveloped, single stranded RNA virus that depends on RNA-dependent RNA polymerase (RdRp) to replicate. Therefore, SARS CoV-2 RdRp is considered as a promising target to cease virus replication. SARS CoV-2 polymerase shows high structural similarity to Hepatitis C Virus-1b genotype (HCV-1b) polymerase. Arising from the high similarity between SARS CoV-2 RdRp and HCV NS5B, we utilized the reported small-molecule binders to the palm subdomain of HCV NS5B (genotype 1b) to generate a high-quality DEKOIS 2.0 benchmark set and conducted a benchmarking analysis against HCV NS5B. The three highly cited and publicly available docking tools AutoDock Vina, FRED and PLANTS were benchmarked. Based on the benchmarking results and analysis via pROC-Chemotype plot, PLANTS showed the best screening performance and can recognize potent binders at the early enrichment. Accordingly, we used PLANTS in a prospective virtual screening to repurpose both the FDA-approved drugs (DrugBank) and the HCV-NS5B palm subdomain binders (BindingDB) for SARS CoV-2 RdRp palm subdomain. Further assessment by molecular dynamics simulations for 50 ns recommended diosmin (from DrugBank) and compound 3 (from BindingDB) to be the best potential binders to SARS CoV-2 RdRp palm subdomain. The best predicted compounds are recommended to be biologically investigated against COVID-19. In conclusion, this work provides in-silico analysis to propose possible SARS CoV-2 RdRp palm subdomain binders recommended as a remedy for COVID-19. Up-to-our knowledge, this study is the first to propose binders at the palm subdomain of SARS CoV2 RdRp. Furthermore, this study delivers an example of how to make use of a high quality custom-made DEKOIS 2.0 benchmark set as a procedure to elevate the virtual screening success rate against a vital target of the rapidly emerging pandemic.

Is Low Alveolar Type II Cell SOD3 in the Lungs of Elderly Linked to the Observed Severity of COVID-19?

Human lungs single-cell RNA sequencing data from healthy donors (elderly and young; GEO accession no. GSE122960) were analyzed to isolate and specifically study gene expression in alveolar type II cells. Colocalization of angiotensin-converting enzyme 2 (ACE2) and TMPRSS2 enables severe acute respiratory syndrome coronavirus 2 (SARS-CoV 2) to enter the cells. Expression levels of these genes in the alveolar type II cells of elderly and young patients were comparable and, therefore, do not seem to be responsible for worse outcomes observed in coronavirus disease 2019 (COVID-19) affected elderly. In cells from the elderly, 263 genes were downregulated and 95 upregulated. Superoxide dismutase 3 (SOD3) was identified as the top-ranked gene that was most downregulated in the elderly. Other redox-active genes that were also downregulated in cells from the elderly included activating transcription factor 4 (ATF4) and metallothionein 2A (M2TA). ATF4 is an endoplasmic reticulum stress sensor that defends lungs via induction of heme oxygenase 1. The study of downstream factors known to be induced by ATF4, according to Ingenuity Pathway Analysis™, identified 24 candidates. Twenty-one of these were significantly downregulated in the cells from the elderly. These downregulated candidates were subjected to enrichment using the Reactome Database identifying that in the elderly, the ability to respond to heme deficiency and the ATF4-dependent ability to respond to endoplasmic reticulum stress is significantly compromised. SOD3-based therapeutic strategies have provided beneficial results in treating lung disorders including fibrosis. The findings of this study propose the hypotheses that lung-specific delivery of SOD3/ATF4-related antioxidants will work in synergy with promising antiviral drugs such as remdesivir to further improve COVID-19 outcomes in the elderly.