Abstract: SA-OR005

aPKC Independent Signaling Events of Par3 at the Glomerular Slit Diaphragm

Session Information

  • A View on the Glomerulus
    November 04, 2017 | Location: Room 294, Morial Convention Center
    Abstract Time: 05:18 PM - 05:30 PM

Category: Glomerular

  • 1003 Glomerular: Cell Biology

Authors

  • Köhler, Sybille, University Hospital Cologne, Cologne, Germany
  • Niessen, Carien M., CECAD University clinic of Cologne, Cologne, Germany
  • Iden, Sandra, University of Cologne, Köln, Germany
  • Bloch, Wilhelm, German Sport University, Cologne, Germany
  • Schermer, Bernhard, University Hospital Cologne, Cologne, Germany
  • Benzing, Thomas, University of Cologne, Köln, 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.

Results

mRNA seq data from primary podocytes revealed high levels of Par3B in podocytes, which were much higher in comparison to Par3A levels. Interestingly, loss of Par3B also did not cause glomerulosclerosis or albuminuria. To study a potential compensatory mechanism between Par3A and Par3B, we generated podocyte-specific Par3A/B double knockout mice. Par3A/B double knockout mice were born following Mendelian rules. Within 8 weeks of age Par3A/B DKO mice developed severe proteinuria in comparison to control mice. To further study the interplay between the different Par3 proteins, we utilized Drosophila nephrocytes. Here, we show co-localization of the Par3A/B homolog bazooka and the nephrocyte diaphragm proteins Sns (nephrin) and Duf (NEPH1) in different developmental stages at the nephrocyte diaphragm. Second, we analyzed the role of bazooka on nephrocyte function. Silencing bazooka expression resulted in a disturbed nephrocyte diaphragm morphology and severe filtration defects. To study the mammalian Par3 proteins in greater detail, we used the UAS-GAL4 system to re-express different murine Par3 variants in a bazooka knockdown background. Although the rescue capacity differed between the different mammalian Par3A isoforms, none of the isoforms resulted in a complete rescue. Even the 100kDa isoform, lacking the aPKC-binding domain, resulted in partial rescue, suggesting an aPKC-independent function for Par3A in nephrocyte filtration. In line with these findings, an aPKCiota interactome from immortalized mouse podocytes, revealed Lgl2 and Par6 as predominant interactors of aPKCiota.

Conclusion

Taken together, the data establish an important role for Par3 function in podocytes and reveal this function is, at least partially, independent from aPKC.