FAM21 is critical for TLR2/CLEC4E-mediated dendritic cell function againstCandida albicans

FAM21 (family with sequence similarity 21) is a component of the Wiskott–Aldrich syndrome protein and SCAR homologue (WASH) protein complex that mediates actin polymerization at endosomal membranes to facilitate sorting of cargo-containing vesicles out of endosomes. To study the function of FAM21in vivo, we generated conditional knockout (cKO) mice in the C57BL/6 background in which FAM21 was specifically knocked out of CD11c-positive dendritic cells. Bone marrow-derived dendritic cells (BMDC) from those mice displayed enlarged early endosomes, and altered cell migration and morphology relative to wildtype (WT) cells. FAM21-cKO cells were less competent in phagocytosis and antigen processingin vitro, though antigen presentation was not affected. More importantly, we identified the TLR2/CLEC4E signaling pathway as being downregulated in FAM21-cKO BMDCs when challenged with its specific ligandCandida albicans. Moreover, FAM21-cKO mice were more susceptible toC. albicansinfection than WT mice. Reconstitution of WT BMDCs in FAM21-cKO mice rescued them from lethalC. albicansinfection. Thus, our study highlights the importance of FAM21 in a host immune response against a significant pathogen.