Ectopic expression of C-type lectin Mincle renders mice susceptible to staphylococcal pneumonia.

Staphylococcus aureus is a prevalent pathogen in pneumonia and harbors glycolipids which may serve as molecular patterns in Mincle (Macrophage inducible C-type lectin) dependent pathogen recognition. We examined the role of Mincle in lung defense against S. aureus in WT, Mincle KO and Mincle transgenic (tg) mice. Two glycolipids, glucosyl-diacylglycerol (Glc-DAG) and diglucosyl-diacylglycerol (Glc2-DAG) were purified, of which only Glc-DAG triggered Mincle reporter cell activation and professional phagocyte responses. Proteomic profiling revealed that Glc2-DAG blocked Glc-DAG-induced cytokine responses, thereby acting as inhibitor of Glc-DAG/Mincle-signaling. WT mice responded to S. aureus with a similar lung pathology as Mincle KO mice, most likely due to Glc2-DAG-dependent inhibition of Glc-DAG/Mincle-signaling. In contrast, ectopic Mincle expression caused severe lung pathology in S. aureus-infected mice characterized by bacterial outgrowth and fatal pneumonia. Collectively, Glc2-DAG inhibits Glc-DAG/Mincle-dependent responses in WT mice, whereas sustained Mincle expression overrides Glc2-DAG-mediated inhibitory effects, conferring increased host susceptibility to S. aureus.