This possibility seemed to be strengthened by the observation

that SIGNR1 physically associates with Dectin-1 constitutively in cells over-expressing SIGNR1 and Dectin-1 (data not shown). Moreover, SIGNR1 and Dectin-1 co-localized to part of the phagosomal membrane in RAW-SIGNR1/Dectin-1 cells (data not shown). This is not the case in rpMϕ, where association/co-localization of SIGNR1 and Dectin-1 was not observed without stimulation, as reported in the case of TNF-α production by collaboration between TLR2 and Dectin-1 8. However, Dectin-1 was recruited to the phagosomal membrane where SIGNR1 captures microbes, and both molecules were detected to physically associate with each other in a time-dependent manner after stimulation. The oxidative burst of RAW-SIGNR1 cells in response to live C. albicans was too weak Selleckchem MAPK inhibitor to detect (data not shown). This may be due to the fact that the cell wall in the live microorganism is covered with mannoproteins, preventing Dectin-1 from accessing the β-glucan ligand. However, RAW-SIGNR1 cells showed significant candidacidal

activity, and this activity was substantially dependent Seliciclib order on Syk-mediated signaling. When RAW-SIGNR1/Dectin-1 cells (data not shown) and rpMϕ were exposed to live microbes, β-glucan appeared to be accessible to Dectin-1, and SIGNR1 and Dectin-1 co-localized to part of the phagosomal membrane. Therefore, it is feasible that such cellular events effectively induce candidacidal activity. Tangeritin It is not clear how SIGNR1 utilizes Syk-mediated signaling though Dectin-1. It has been reported that cross-linking of SIGNR1 by neo-glycoprotein containing mannose residues and specific antibody induces the activation of JNK and NF-κB, leading to the production of TNF-α 31, IL-12 32 and IL-10 33. Therefore, it is plausible that SIGNR1

transduces the signal by itself. However, RAW264.7 cells expressing the SIGNR1 truncated cytosolic portion were still able to facilitate the oxidative response, suggesting that it is unlikely that there is any direct involvement of the cytosolic portion of SIGNR1 in signal transduction. SIGNR1 in RAW264.7 transfectants is reported to co-localize in lipid rafts with several Src family kinases 31. Therefore, cross-linking of SIGNR1 by ligand/microbes possibly induces activation of the kinases. Alternatively, SIGNR1 might also cooperate with other unidentified molecules than Dectin-1 to induce the Syk-dependent signaling. These possibilities remain to be elucidated in future experiments. In the systemic infection or stimulation, SIGNR1 may not be a major player in the host defense, since SIGNR1 is expressed in limited populations of DCs and Mϕ.