VDR agonists trigger Wnt/β-catenin downregulation in a Kaposi?s sarcoma cellular model

GONZALEZ PARDO, VERNONICA; TAPIA, CINTHYA; DE GENARO, PABLO

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 (eso se podria sacar si se excede en caracteres), was increased in the nucleus and plasma membrane. This event that was accompanied by a VE-cadherin plasma membrane increased . 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 targets genes in response to 1α,25(OH)2D3