DNAM-1 mediates NK-cell activation and host-pathogen interaction via direct binding to fungal cell wall proteases

Natural killer (NK) cells play a key role in combating invasive mycoses, with surface proteins crucial for immune cell-target interactions. Here, we investigate the role of DNAX accessory molecule 1 (DNAM-1; CD226) in the recognition of Aspergillus fumigatus and Candida albicans hyphae. Super-resolution microscopy reveals a uniform distribution of DNAM-1 on naïve NK cells that is maintained upon contact with fungal hyphae. However, soluble DNAM-1 binds to the fungal cell wall and blocking DNAM-1 reduces antifungal activity in colony-forming assays. Furthermore, in silico domain-domain interaction analysis identifies several fungal proteins as putative DNAM-1 targets, including OpsB in A. fumigatus and Sap10 in C. albicans. High-affinity binding between Sap10 and DNAM-1 is predicted computationally and confirmed experimentally by co-immunoprecipitation and fluorescence correlation spectroscopy. Microscopic analysis further demonstrates that Sap10 binds to primary NK cells but not to DNAM-1-deficient NK cells. Sap10 binding induced NK-cell activation, as evidenced by increased CD69 expression and elevated perforin and CCL3 secretion. These findings identify Sap10 as a fungal ligand of DNAM-1 and reveal a mechanism by which NK cells recognize fungal pathogens.