TRAF1 negatively regulates C-type lectin receptor-induced proinflammatory response to fungal infection

Abstract

Abstract Fungal infections pose serious health threat worldwide, causing severe mucosal and systemic candidiasis in elderly people, AIDS patients and organ recipients. Through sensing fungal cell-wall components b-glucan and mannan, C-type lectin receptors (CLRs) dectin-1 and dectin-2/3 play pivotal role in the induction of anti-fungal innate and adaptive immune responses. However, the regulatory mechanisms of CLR signaling remain to be better understood. Indeed, our previous work demonstrated that the protein tyrosine phosphatase SHP-2 acts as a positive regulator of CLR-induced signaling, and thus plays a critical role in DCs to promote anti-fungal Th17 response. In this study, we found that fungus-elicited CLR signals are also stringently controlled by negative regulation. Upon C. albicans infection, TRAF1 was highly induced in skin, lung and kidney. Elevated TRAF1 expression was also detected in macrophages and DCs stimulated by dectin-1 and dectin-2/3 ligands, respectively. Mechanistically, TRAF1 acted as a feed-back negative regulator critically controlling the induction of proinflammatory genes, such as Cxcl1 and Tnf, in response to fungal infection. Consistently, TRAF1-deficient mice exhibited increased neutrophil-infiltration, highly efficient fungal eradication and ameliorated tissue damage, culminating on improved host defense and better survival. Taken together, this study identified a new feed-back regulatory mechanism by which CLRs regulate anti-fungal proinflammatory response.