Dectin-1, also known as CLEC7A and the beta-glucan receptor, is a 33 kDa type II transmembrane C-type lectin that participates in the innate immune response to fungal pathogens. Although Dectin-1 structurally resembles other CLEC molecules, it binds its ligands in a calcium-independent manner.
Mature human Dectin-1 consists of a short N-terminal ITAM-containing cytoplasmic tail, a transmembrane segment, and a C-terminal stalk with carbohydrate recognition domain (CRD) in the extracellular domain. Alternate splicing generates one major splice form that lacks the stalk region. This isoform is expressed on the surface of monocytes, macrophages, myeloid DC, neutrophils, eosinophils, B cells, and CD4+ T cells. The CRD selectively binds beta-glucan polymers, a major component of yeast and mycobacterial cell walls. Yeast beta-glucan is accessible to Dectin-1 only during the process of cell budding. Dectin-1 does not recognize the filamentous form of yeast. Dectin-1 mediates the phagocytosis of zymosan particles and intact yeast.
In the membrane, Dectin-1 colocalizes with TLR2 in the presence of zymosan, and the two receptors cooperate in ligand recognition and the propagation of proinflammatory signaling. Dectin-1 also interacts with tetraspanin CD37. This increases its stability on the cell membrane and inhibits ligand-induced signaling. Dectin-1 knockout mice show increased susceptibility to pathogenic infection.
In addition to the full-length Dectin-2 alpha isoform, 2 truncated isoforms, lacking the neck domain (2 beta) or part of the carbohydrate recognition domain (2 gamma), exist.