Transcription regulation of SARS-CoV-2 receptor ACE2 by Sp1: a potential therapeutic target (preprint)

Angiotensin-converting enzyme 2 (ACE2) is a major cell entry receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Induction of ACE2 expression may represent an effective tactic employed by SARS-CoV-2 to facilitate its own propagation. However, the regulatory mechanisms of ACE2 expression after viral infection remain largely unknown. By employing an array of 45 different luciferase reporters, we identify that the transcription factor Sp1 positively and HNF4 negatively regulate the expression of ACE2 at the transcriptional levels in HPAEpiC cells, a human lung epithelial cell line. SARS-CoV-2 infection promotes and inhibits the transcription activity of Sp1 and HNF4, respectively. The PI3K/AKT signaling pathway, which is activated by SARS-CoV-2 infection, is a crucial node for induction of ACE2 expression by increasing Sp1 phosphorylation, an indicator of its activity, and reducing HNF4 nuclear location. Furthermore, we show that colchicine could inhibit the PI3K/AKT signaling pathway, thereby suppressing ACE2 expression. Inhibition of Sp1 by either its inhibitor mithramycin A or colchicine reduces viral replication and tissue injury in Syrian hamsters infected with SARS-CoV-2. In summary, our study uncovers a novel function of Sp1 in regulating ACE2 expression and suggests that Sp1 is a potential target to reduce SARS-CoV-2 infection.

Novel and potent inhibitors targeting DHODH, a rate-limiting enzyme in de novo pyrimidine biosynthesis, are broad-spectrum antiviral against RNA viruses including newly emerged coronavirus SARS-CoV-2 (preprint)

Emerging and re-emerging RNA viruses occasionally cause epidemics and pandemics worldwide, such as the on-going outbreak of coronavirus SARS-CoV-2. Existing direct-acting antiviral (DAA) drugs cannot be applied immediately to new viruses because of virus-specificity, and the development of new DAA drugs from the beginning is not timely for outbreaks. Thus, host-targeting antiviral (HTA) drugs have many advantages to fight against a broad spectrum of viruses, by blocking the viral replication and overcoming the potential viral mutagenesis simultaneously. Herein, we identified two potent inhibitors of DHODH, S312 and S416, with favorable drug-like and pharmacokinetic profiles, which all showed broad-spectrum antiviral effects against various RNA viruses, including influenza A virus (H1N1, H3N2, H9N2), Zika virus, Ebola virus, and particularly against the recent novel coronavirus SARS-CoV-2. Our results are the first to validate that DHODH is an attractive host target through high antiviral efficacy in vivo and low virus replication in DHODH knocking-out cells. We also proposed the drug combination of DAA and HTA was a promising strategy for anti-virus treatment and proved that S312 showed more advantageous than Oseltamivir to treat advanced influenza diseases in severely infected animals. Notably, S416 is reported to be the most potent inhibitor with an EC50 of 17nM and SI value >5882 in SARS-CoV-2-infected cells so far. This work demonstrates that both our self-designed candidates and old drugs (Leflunomide/Teriflunomide) with dual actions of antiviral and immuno-repression may have clinical potentials not only to influenza but also to COVID-19 circulating worldwide, no matter such viruses mutate or not.