Protein kinase C ϵ stabilizes β-catenin and regulates its subcellular localization in podocytes.

Abstract

Kidney disease has been linked to dysregulated signaling via PKC in kidney cells such as podocytes. PKCα is a conventional isoform of PKC and a well-known binding partner of β-catenin, which promotes its degradation. β-Catenin is the main effector of the canonical Wnt pathway and is critical in cell adhesion. However, whether other PKC isoforms interact with β-catenin has not been studied systematically. Here we demonstrate that PKCϵ-deficient mice, which develop proteinuria and glomerulosclerosis, display lower β-catenin expression compared with PKC wild-type mice, consistent with an altered phenotype of podocytes in culture. Remarkably, β-catenin showed a reversed subcellular localization pattern: Although β-catenin exhibited a perinuclear pattern in undifferentiated wild-type cells, it predominantly localized to the nucleus in PKCϵ knockout cells. Phorbol 12-myristate 13-acetate stimulation of both cell types revealed that PKCϵ positively regulates β-catenin expression and stabilization in a glycogen synthase kinase 3β-independent manner. Further, β-catenin overexpression in PKCϵ-deficient podocytes could restore the wild-type phenotype, similar to rescue with a PKCϵ construct. This effect was mediated by up-regulation of P-cadherin and the β-catenin downstream target fascin1. Zebrafish studies indicated three PKCϵ-specific phosphorylation sites in β-catenin that are required for full β-catenin function. Co-immunoprecipitation and pulldown assays confirmed PKCϵ and β-catenin as binding partners and revealed that ablation of the three PKCϵ phosphorylation sites weakens their interaction. In summary, we identified a novel pathway for regulation of β-catenin levels and define PKCϵ as an important β-catenin interaction partner and signaling opponent of other PKC isoforms in podocytes.

• Authors: Michelle Duong, Xuejiao Yu, Beina Teng, Patricia Schroder, Hermann Haller, Susanne Eschenburg, Mario Schiffer
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 292 Issue 29 Pg. 12100-12110 (07 21 2017) ISSN: 1083-351X [Electronic] United States
• PMID: 28539358 (Publication Type: Comparative Study, Journal Article, Validation Study)
• Copyright: © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Chemical References

• CTNNB1 protein, mouse
• Carcinogens
• Recombinant Proteins
• beta Catenin
• phorbolol myristate acetate
• Prkce protein, mouse
• Glycogen Synthase Kinase 3 beta
• Protein Kinase C-epsilon
• Tetradecanoylphorbol Acetate

Topics

• Active Transport, Cell Nucleus (drug effects)
• Amino Acid Substitution
• Animals
• Biological Assay
• Carcinogens (toxicity)
• Cell Line, Transformed
• Gene Expression Regulation (drug effects)
• Glycogen Synthase Kinase 3 beta (metabolism)
• HEK293 Cells
• Humans
• Mice, Knockout
• Mutagenesis, Site-Directed
• Mutation
• Phosphorylation (drug effects)
• Podocytes (cytology, drug effects, metabolism)
• Protein Kinase C-epsilon (antagonists & inhibitors, genetics, metabolism)
• Protein Processing, Post-Translational (drug effects)
• Protein Stability (drug effects)
• Recombinant Proteins (chemistry, metabolism)
• Tetradecanoylphorbol Acetate (analogs & derivatives, toxicity)
• Tissue Culture Techniques
• beta Catenin (antagonists & inhibitors, chemistry, genetics, metabolism)