Abstract: SA-PO306
Par3A and Par3B Orchestrate Podocyte Polarity
Session Information
- Cellular Crosstalk in Glomerular Diseases - II
October 27, 2018 | Location: Exhibit Hall, San Diego Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Glomerular Diseases
- 1201 Glomerular Diseases: Fibrosis and Extracellular Matrix
Authors
- Köhler, Sybille, University Hospital Cologne, Cologne, Germany
- Iden, Sandra, University of Cologne, Cologne, Germany
- Niessen, Carien M., CECAD University clinic of Cologne, Cologne, Germany
- Schermer, Bernhard, University Hospital Cologne, Cologne, Germany
- Benzing, Thomas, University of Cologne, Cologne, Germany
- Denholm, Barry, Edinburgh University, Edinburgh, United Kingdom
- Brinkkoetter, Paul T., University Hospital Cologne, Cologne, Germany
Background
Polarity signaling through the aPKC-Par polarity complex is essential for the development and maintenance of the podocyte architecture and the function of the glomerular filtration barrier of the kidney. Despite its well-established role in aPKC-mediated signaling, Par3A appears to be dispensable for the function of the glomerular filtration barrier. Interestingly, loss of Par3B also did not result in albuminuria and glomerulosclerosis.
Methods
To study potential compensatory mechanisms between Par3A and Par3B, we employed conditional in vivo targeting strategies specifically in podocytes and generated podocyte-specific Par3A/B double knockout mice.
Results
Within 8 weeks Par3A/B DKO mice developed severe proteinuria and renal failure. We utilized Drosophila nephrocytes to further study the interplay between the different Par3 proteins. Here, we show co-localization of the Par3A/B homolog bazooka and the nephrocyte diaphragm proteins Sns (nephrin) and Duf (NEPH1) at different developmental stages. Silencing bazooka expression resulted in disturbed nephrocyte diaphragm morphology, severe filtration defects and delayed larval development.
To investigate the functional role of Par3A and Par3B, we re-expressed different murine Par3 variants in a bazooka knockdown background using the UAS-GAL4 system. Here, we performed several morphological and functional studies and observed different degrees of rescue potential. We utilized high resolution microscopy to resolve the nephrocyte diaphragm pattern and observed a decreased coverage and severely changed localization of Duf (dNeph) and Pyd (dZO-1) after nephrocyte-specific depletion of bazooka. This phenotype can be partially rescued by re-expression of aPKCiota-binding Par3 variants, while the 100kDa Par3A variant and Par3B present with almost no rescue. As none of the Par3 variants is able to provide a full rescue and to study the potential compensatory phenotype between Par3A and Par3B we generated Par3A/B double rescue flies and could show an almost complete rescue in Duf (dNeph) and Pyd (dZO-1) localization, confirming the compensatory potential of the two Par3 variants.
Conclusion
Taken together, these findings support the hypothesis of a potential compensatory mechanism between Par3A and Par3B to maintain polarity signaling at the slit diaphragm which are - at least partially – independent of aPKC.