VDR agonists trigger Wnt/B-catenin downregulation in a celular model of Kaposi?s sarcoma

VERONICA GONZALEZ PARDO; CINTHYA TAPIA; PABLO DE GENERARO

Salta

Congreso; Joint LV Annual SAIB Meeting and XIV PABMB Congress; 2019

SAIB

We have previously shown that 1α,25(OH)2D3 exerts antiproliferative effects in endothelial cells stable expressing Kaposi?s Sarcoma-associated Herpesvirus G Protein-coupled Receptor (vGPCR) through NF-κB pathway inhibition and apoptosis induction. β-catenin, a multifunctional protein, is required for cell-cell adhesion and gene expression regulation in response to Wnt. Aberrant activation of this pathway provokes β-catenin accumulation in the nucleus and induces cell proliferation. Since it is well documented that vGPCR activates the canonical Wnt/β-catenin signaling pathway, we investigated if β-catenin and its target genes are regulated by 1α,25(OH)2D3. Firstly, Western blot studies showed an increase in β-catenin protein levels, which were not affected by the presence of Actinomycin D, a transcription blocker, after 1α,25(OH)2D3 (10 nM, 24 h) treatment. Secondly, β-catenin localization, investigated by immunofluorescence and subcellular fractioning techniques, was increased in the nucleus and plasma membrane. This event was accompanied by an increase in VE-cadherin in the cell membrane. Furthermore, a β-catenin/VDR interaction was observed by co-immunoprecipitation, which correlated with a decrease in the expression levels of β-catenin target genes c-myc, cyclin D1 and MMP-9 mRNA after 1α,25(OH)2D3 (10 nM, 48 h). Finally, Dkk-1, the extracellular inhibitor of Wnt/β-catenin pathway, elicited an initial upregulation of mRNA expression accompanied by lower β-catenin protein levels (0.5-1 h). Altogether, β-catenin/VDR interaction may account for non-transcriptional accumulation of β-catenin protein levels and downregulation of its target genes in response to 1α,25(OH)2D3