Dectin-1 Stimulation by <i>Candida albicans</i> Yeast or Zymosan Triggers NFAT Activation in Macrophages and Dendritic Cells

Innate immune pattern recognition receptors play critical roles in pathogen detection and initiation of antimicrobial responses. We and others have previously demonstrated the importance of the beta-glucan receptor Dectin-1 in the recognition of pathogenic fungi by macrophages and dendritic cells and have elucidated some of the mechanisms by which Dectin-1 signals to coordinate the antifungal response. While Dectin-1 signals alone are sufficient to trigger phagocytosis and Src-Syk-mediated induction of antimicrobial reactive oxygen species, collaboration with TLR2 signaling enhances NF-kappaB activation and regulates cytokine production. In this study we demonstrate that Dectin-1 signaling can also directly modulate gene expression via activation of NFAT. Dectin-1 ligation by zymosan particles or live Candida albicans yeast triggers NFAT activation in macrophages and dendritic cells. Dectin-1-triggered NFAT activation plays a role in the induction of early growth response 2 and early growth response 3 transcription factors, and cyclooxygenase-2. Furthermore, we show that NFAT activation regulates IL-2, IL-10 and IL-12 p70 production by zymosan-stimulated dendritic cells. These data establish NFAT activation in myeloid cells as a novel mechanism of regulation of the innate antimicrobial response.