The Preliminary Study On The Secretion Of WNT Protein In Dendritic Cells

Dendritic cells (DCs) were the most important antigen presenting cells (APCs). And it was demonstrated that Wnt signaling pathways can regulate the immune systems in various aspects. Here we are curious about the regulation roles of Wnt signaling pathway in DC. Dendritic cells were induced from blood monocytes by co-culturing with GM-CSF and IL-4 for five days. In this study we investigated the expression and secretion of several Wnt signaling components in this monocyte-derived dendritic cells and analysed its effects on the functions of DC.In this study, we examined the expression profiles of Wnt signaling components by RT-PCR. It was demonstrated that the mRNA of WNT5A ligands and several receptors of Wnt signaling pathway like Frz1, Frz2, Frz3, Frz4, LRP6 and ROR2 were continuously expressed during the differentiation process from monocytes to DC. The distribution of WNT5A in the whole cytoplasm was also confirmed by immunofluorescence data. All this implied us that the Wnt signaling pathway might play an important role in the differentiation and functions of dendritic cells.It was reported that SB216763 was an activator of the canonical Wnt signaling pathway (Wnt/β-catenin signaling). In this study it was showed that treatment with 10μM SB216763 for 2-3 hours could stimulated the accumulation and activation ofβ-catenin in DC. And the activation ofβ-catenin could induce the phenotypic maturation of DC. The mean fluorescence intensity of costimulatory molecules CD80, CD86 and functional molecule CD40 increased significantly, nearly the same level of that expressed on mature DC. But the DC was not mature in function. The expression of inflammatory factors IL-1β, IL-6, IL-12 p40, TNF-a and chemokine receptors CCR7 was much lower than that expressed by LPS-activated mature DC, even lower than that of immature DC. Therefore they belong to a kind of tolerogenic DC.Additionally, the secretion mechanism of WNT5A in DC and transport of hydrophobic WNT protein between cells remained unknown. Recently it was demonstrated that Wntless and Retromer Complex facilitate the secretion of WNT in the development process of Drosophila. In order to prove whether Wntless and Retromer Complex have the same role in the secretion of WNT in DC, we knocked down the expression of Wntless and Vps35, the key subunit of Retromer Complex, by RNA interference. It was showed that the distribution of WNT5A on the cell membrane decreased with the reduction of Wntless and Vps35. Hence the study demonstrated that Wntless and Retromer Complex participated in the secretion of WNT in DC.