C-type lectin receptor-induced NF-κB activation in innate immune and inflammatory responses

The C-type lectin receptors (CLRs) belong to a large family of proteins that contain a carbohydrate recognition domain (CRD) and calcium binding sites on their extracellular domains. Recent studies indicate that many CLRs, such as Dectin-1, Dectin-2 and Mincle, function as pattern recognition receptors (PRRs) recognizing carbohydrate ligands from infected microorganisms. Upon ligand binding, these CLRs induce multiple signal transduction cascades through their own immunoreceptor tyrosine-based activation motifs (ITAMs) or interacting with ITAM-containing adaptor proteins such as FcRγ. Emerging evidence indicate that CLR-induced signaling cascades lead to the activation of nuclear factor kappaB (NF-κB) family of transcriptional factors through a Syk- and CARD9-dependent pathway(s). The activation of NF-κB plays a critical role in the induction of innate immune and inflammatory responses following microbial infection and tissue damages. In this review, we will summarize the recent progress on the signal transduction pathways induced by CLRs, and how these CLRs activate NF-κB and contribute to innate immune and inflammatory responses.