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Abstract: SA-PO218

Cell Adhesion Function of β-Catenin in Podocytes Is Crucial for Glomerular Filtration Barrier

Session Information

  • Glomerular: Cell Biology
    November 04, 2017 | Location: Hall H, Morial Convention Center
    Abstract Time: 10:00 AM - 10:00 AM

Category: Glomerular

  • 1003 Glomerular: Cell Biology

Authors

  • Duong, Michelle, Hanover Medical School, Hannover, Germany
  • Teng, Beina, Medical School Hannover, Hannover, Germany
  • Haller, Hermann G., Hannover Medical School, Hannover, Germany
  • Schiffer, Mario, Hannover Medical School, Hannover, Germany
Background

β-Catenin has two functions: it mediates cell adhesion and Wnt signaling. Its function depends on its subcellular localization, as membranous β-catenin locates at cell adhesion complexes with cadherin and α-Catenin. On the other hand, β-catenin transcriptional activity is regulated by a nuclear β-catenin localization. We have shown β-catenin interacts with PKCε and PKCε deficiency leads to a nuclear localization of β-catenin. PKCε -/- podocytes show a increased cell detachment, apoptosis and reduced differentiation. P-cadherin and IQGAP1 are proteins involved in membranous β-catenin stability. We therefore investigated the relationship of this complex in podocytes.

Methods

We performed time course Western blot of cell lysates of murine PKCε -/- podocytes and tested the IQGAP and P-cadherin expression. We used adenoviral PKCε and β-catenin constructs to overexpress these proteins in PKCε deficient podocytes. Immunofluorescent staining was performed on murine kidney sections and podocytes to examine the P-cadherin and vinculin expression. Zebrafish larvae were injected with β-catenin1 morpholino and localization mutant β-catenin RNAs to investigate their function in vivo.

Results

During the differentiation of PKCε -/- podocytes, IQGAP1 and p-cadherin expression was reduced compared to WT cells. Overexpression of not only PKCε, but also ß-catenin, could reverse this effect and led to an normal IQGAP1 expression. We saw in immunofluorescence and western blot analysis a downregulated vinculin expression in PKCε -/- podocytes, which could be reversed by β-catenin overexpression. β-Catenin1 knockdown in zebrafish led to with proteinuria and edema. This could be partially rescued with overexpression of a β-catenin mutant expressed in the membrane, while a β-catenin mutant expressed in the nucleus could not reverse proteinuria.

Conclusion


We show β-catenin as a upstream mediator of cell-adhesion by its regulation of the adherens junction proteins P-cadherin, IQGAP1 and focal adhesion molecules such as vinculin. This complex is disturbed in functionally disabled podocytes. ß-catenin is translocated to the nucleus in unhealthy podocytes and the cell-adhesion function of β-catenin plays a more important role in the maintenance of the glomerular filtration barrier in zebrafish. The Wnt signaling function of β-catenin alone seems not to promote kidney health.