Azouz, N. P.Klingler, A. M.Callahan, VictoriaAkhrymuk, Ivan V.Elez, K.Raich, L.Henry, B. M.Benoit, J. L.Benoit, S. W.Noé, F.Kehn-Hall, KyleneRothenberg, M. E.2021-08-252021-08-252021-01-012469-2964PMC8097828pai.v6i1.408 (PII)http://hdl.handle.net/10919/104707Background: Host proteases have been suggested to be crucial for dissemination of MERS, SARS-CoV, and SARS-CoV-2 coronaviruses, but the relative contribution of membrane versus intracellular proteases remains controversial. Transmembrane serine protease 2 (TMPRSS2) is regarded as one of the main proteases implicated in the coronavirus S protein priming, an important step for binding of the S protein to the angiotensin-converting enzyme 2 (ACE2) receptor before cell entry. Methods: We developed a cell-based assay to identify TMPRSS2 inhibitors. Inhibitory activity was established in SARS-CoV-2 viral load systems. Results: We identified the human extracellular serine protease inhibitor (serpin) alpha 1 anti-trypsin (A1AT) as a novel TMPRSS2 inhibitor. Structural modeling revealed that A1AT docked to an extracellular domain of TMPRSS2 in a conformation that is suitable for catalysis, resembling similar serine protease inhibitor complexes. Inhibitory activity of A1AT was established in a SARS-CoV-2 viral load system. Notably, plasma A1AT levels were associated with COVID-19 disease severity. Conclusions: Our data support the key role of extracellular serine proteases in SARS CoV-2 infections and indicate that treatment with serpins, particularly the FDA-approved drug A1AT, may be effective in limiting SARS-CoV-2 dissemination by affecting the surface of the host cells.Pages 55-74application/pdfenCreative Commons Attribution 4.0 InternationalCOVIDTMPRSS2alpha 1 antitrypsincamostat mesylatecoronavirusproteaseArticle - Refereed2021-08-25https://doi.org/10.20411/pai.v6i1.40861Kehn-Hall, Kylene [0000-0001-8036-7213]339692492469-2964