Identification and Characterization of LYSMD3, A Novel Epithelial Cell Pattern Recognition Receptor for Chitin

LysM-domain containing (LysMD) proteins are widespread in nature and associated with host-pathogen interactions, often-binding peptidoglycan and chitin. However, the functions of mammalian LysMD proteins have not been fully defined. Chitin, a major component of fungal cell walls, has been associated with allergic disorders such as asthma. However, chitin recognition by mammals remains enigmatic at best. The principal receptor(s) on epithelial cells for chitin recognition remain to be determined. In this study, we demonstrate that LYSMD3 is expressed on the surface of human airway epithelial cells. Interestingly, LYSMD3 is able to bind chitin and β-glucan as well as fungal spores. Knockdown and knockout of LYSMD3 markedly impaired chitin and fungi-induced inflammatory cytokine production in lung epithelial cells. Antagonization of LYSMD3 ectodomain by soluble LYSMD3 protein, multiple ligands, or antibody against LYSMD3 all significantly blocked chitin signaling. Taken together our study identifies LYSMD3 as a mammalian pattern recognition receptor (PRR) for chitin and is required for the epithelial inflammatory response to chitin and fungal spores.