Contribution of Dectin-1 to the Recognition of Fungal Cell Wall Products and the Activation of Innate Immune Response

1,3-Beta-glucans is a major cell wall component in fungi. Receptor molecules relating to innate immunity may recognize such cell wall products, and affect host defense systems. A beta-glucan receptor, dectin-1, is a C-type lectin and may contribute to the innate immune responses. To examine the role of dectin-1 in recognition of 1,3-beta-glucans and subsequent activation of intracellular signaling, the molecular characteristics of a carbohydrate recognition domain (CRD) of dectin-1 were investigated. The binding ability to beta-glucans was abolished by mutating two amino acid residues, Trp221 and His223, on the CRD. Dectin-1 increased TLR2-mediated NF-kappaB activation in response to zymosan. However, dectin-1 alone could not affect the activation pathway for NF-kappaB, nor did co-expression of dectin-1 mutant and TLR2 increase the NF-kappaB activation. These results suggest that dectin-1 may have a co-stimulatory effect on leukocyte activation in response to fungal infection.