Prediction and validation of host cleavage targets of SARS-CoV-2 3C like protease

How SARS-CoV-2 causes the observed range of clinical manifestations and disease severity remains poorly understood. SARS-CoV-2 encodes for two proteases (3CLPro and PLPro), vital for viral production, but also promiscuous with respect to host protein targets, likely contributing to the range of disease. Pharmacological inhibition of the 3C-like3 protease has revealed remarkable reduction in hospitalization and death in phase 2/3 clinical studies. However, the mechanisms responsible for the pathology mediated by those proteases are still unclear. In this study, we develop a bioinformatic algorithm, leveraging experimental data from SARS-CoV, to predict host cleavage targets of the SARS-CoV-2 3C-like protease, or 3CLPro. We capture targets of the 3CL protease described previously for SARS-CoV, and we identify hundreds of new putative targets. We experimentally validate a number of these predicted targets, including the giant sarcomeric protein Obscurin, and show that expression of 3CL protease alone recapitulates the sarcomeric disorganization seen by SARS-CoV-2 infection of hiPSC-derived cardiomyocytes. Our data provide a resource to identify putative host cleavage targets of 3CL protease that contribute to mechanisms and heterogeneity of disease in COVID-19 and future coronavirus outbreaks.

Discovery of a AhR flavonoid agonist that counter-regulates ACE2 expression in rodent models of inflammation and attenuates ACE2-SARS-CoV2 interaction in vitro

The severe acute respiratory syndrome (SARS)-CoV-2, a newly emerged coronavirus first identified in 2019, is the pathogenetic agent od Corona Virus Induced Disease (COVID)19. The virus enters the human cells after binding to the angiotensin converting enzyme (ACE) 2 receptor in target tissues. ACE2 expression is induced in response to inflammation. The colon expression of ACE2 is upregulated in patients with inflammatory bowel disease (IBD), highlighting a potential risk of intestinal inflammation in promoting viral entry in the human body. Because mechanisms that regulate ACE2 expression in the intestine are poorly understood and there is a need of anti-SARS-CoV2 therapies, we have settled to investigate whether natural flavonoids might regulate the expression of ACE2 in intestinal models of inflammation. The results of these studies demonstrated that pelargonidin, a natural flavonoid bind and activates the Aryl hydrocarbon Receptor (AhR) in vitro and reverses intestinal inflammation caused by chronic exposure to high fat diet or to the intestinal braking-barrier agent DSS in a AhR-dependent manner. In these two models, development of colon inflammation associated with upregulation of ACE2 mRNA expression. Colon levels of ACE2 mRNA were directly correlated with TNF mRNA levels. In contrast to ACE2 the angiotensin 1-7 receptor MAS was downregulated in the inflamed tissues. Molecular docking studies suggested that pelargonidin binds a fatty acid binding pocket on the receptor binding domain of SARS-CoV2 Spike protein. In vitro studies demonstrated that pelargonidin significantly reduces the binding of SARS-CoV2 Spike protein to ACE2 and reduces the SARS-CoV2 replication in a concentration-dependent manner. In summary, we have provided evidence that a natural flavonoid might hold potential in reducing intestinal inflammation and ACE2 induction in the inflamed colon in a AhR-dependent manner.

SARS-CoV-2 infects human pluripotent stem cell-derived cardiomyocytes, impairing electrical and mechanical function

Global health has been threatened by the COVID-19 pandemic, caused by the novel severe acute respiratory syndrome coronavirus (SARS-CoV-2)1. Although considered primarily a respiratory infection, many COVID-19 patients also suffer severe cardiovascular disease2-4. Improving patient care critically relies on understanding if cardiovascular pathology is caused directly by viral infection of cardiac cells or indirectly via systemic inflammation and/or coagulation abnormalities3,5-9. Here we examine the cardiac tropism of SARS-CoV-2 using human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) and three-dimensional engineered heart tissues (3D-EHTs). We observe that hPSC-CMs express the viral receptor ACE2 and other viral processing factors, and that SARS-CoV-2 readily infects and replicates within hPSC-CMs, resulting in rapid cell death. Moreover, infected hPSC-CMs show a progressive impairment in both electrophysiological and contractile properties. Thus, COVID-19-related cardiac symptoms likely result from a direct cardiotoxic effect of SARS-CoV-2. Long-term cardiac complications might be possible sequelae in patients who recover from this illness.