biostudies-literatureNing YChina Scholarship CouncilAustrian Science Fund FWFDeutsche Forschungsgemeinschaft24924-24934https://www.ebi.ac.uk/biostudies/studies/S-EPMC7618453biostudies-literatureUnknown68(23)C-Type lectins are a large family of carbohydrate-binding proteins. Langerin is a member of this family and is expressed by Langerhans cells, involved in pathogen recognition and innate immune activation, making it a target for small-molecule modulation in immunology and infectious diseases. We previously identified thiazolopyrimidinones as a series of allosteric inhibitors, but the underlying mechanism remained unclear. In this study, ⁴³Ca NMR demonstrated that these fragments induce Ca²⁺ release from the receptor. Our ITC data suggested a competitive relationship between inhibitors and Ca²⁺, which was further validated by ¹⁹F NMR spectroscopy showing inhibition of carbohydrate binding. Surprisingly, the fragment binding site was found to be locJournal of medicinal chemistryCalcium Competitive Inhibition of Langerin by Thiazolopyrimidinones.PMC761845310.55776/I5771NI 515710.55776/I5157669831-NA1274/7-1I 5771202106790019Turhan ERuwolt MNeu UNazare MKohnke JRademacher CLefebre JEfrem NLKurzbach DBesch MNing YAmoussa MLoll BZheng DfalseCalcium Competitive Inhibition of Langerin by Thiazolopyrimidinones.C-Type lectins are a large family of carbohydrate-binding proteins. Langerin is a member of this family and is expressed by Langerhans cells, involved in pathogen recognition and innate immune activation, making it a target for small-molecule modulation in immunology and infectious diseases. We previously identified thiazolopyrimidinones as a series of allosteric inhibitors, but the underlying mechanism remained unclear. In this study, ⁴³Ca NMR demonstrated that these fragments induce Ca²⁺ release from the receptor. Our ITC data suggested a competitive relationship between inhibitors and Ca²⁺, which was further validated by ¹⁹F NMR spectroscopy showing inhibition of carbohydrate binding. Surprisingly, the fragment binding site was found to be loc2025-01-01T00:00:00Z2025 Dec2026-06-10T05:17:48.117Z2026-06-10T03:07:27.953ZS-EPMC76184534126104010.1021/acs.jmedchem.5c01756