{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,9]],"date-time":"2026-10-09T02:03:05Z","timestamp":1791511385641,"version":"4.3.4"},"reference-count":60,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2024,11,19]],"date-time":"2024-11-19T00:00:00Z","timestamp":1731974400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Immunol."],"abstract":"<jats:sec><jats:title>Background<\/jats:title><jats:p>The serine protease like (Spl) proteases of <jats:italic>Staphylococcus aureus<\/jats:italic> are a family of six proteases whose function and impact on virulence are poorly understood. Here we propose alpha-1-antitrypsin (AAT), an important immunomodulatory serine protease inhibitor as target of SplD, E and F. AAT is an acute phase protein, interacting with many proteases and crucial for prevention of excess tissue damage by neutrophil elastase during the innate immune response to infections.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>We used MALDI-TOF-MS to identify the cleavage site of Spl proteases within AAT\u2019s reactive center loop (RCL) and LC-MS\/MS to quantify the resulting peptide cleavage product in <jats:italic>in vitro<\/jats:italic> digestions of AAT and heterologous expressed proteases or culture supernatants from different <jats:italic>S. aureus<\/jats:italic> strains. We further confirmed proteolytic cleavage and formation of a covalent complex with Western Blots, investigated AAT\u2019s inhibitory potential against Spls and examined the NETosis inhibitory activity of AAT-Spl-digestions.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>SplD, E and F, but not A or B, cleave AAT in its RCL, resulting in the release of a peptide consisting of AAT\u2019s C-terminal 36 amino acids (C36). Synthetic C36, as well as AAT-SplD\/E\/F-digestions exhibit NETosis inhibition. Only SplE, but not D or F, was partly inhibited by AAT, forming a covalent complex.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusion<\/jats:title><jats:p>We unraveled a new virulence trait of <jats:italic>S. aureus<\/jats:italic>, where SplD\/E\/F cleave and inactivate AAT while the cleavage product C36 inhibits NETosis.<\/jats:p><\/jats:sec>","DOI":"10.3389\/fimmu.2024.1481181","type":"journal-article","created":{"date-parts":[[2024,11,19]],"date-time":"2024-11-19T06:17:59Z","timestamp":1731997079000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":12,"title":["Alpha-1-antitrypsin as novel substrate for S. aureus\u2019 Spl proteases \u2013 implications for virulence"],"prefix":"10.3389","volume":"15","author":[{"given":"Franziska","family":"Scherr","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Murthy 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