Abstract: FR-PO706
mTOR-Dependent Autophagy Regulates Slit Diaphragm Density in Podocyte-Like Drosophila Nephrocytes
Session Information
- Glomerular Diseases: Podocyte Biology - I
November 04, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
Abstract Time: 10:00 AM - 12:00 PM
Category: Glomerular Diseases
- 1304 Glomerular Diseases: Podocyte Biology
Authors
- Spitz, Dominik, Renal Division, Department of Medicine, Faculty of Medicine and Medical Center - University of Freiburg, Freiburg, Germany
- Comas Soberats, Maria, Renal Division, Department of Medicine, Faculty of Medicine and Medical Center - University of Freiburg, Freiburg, Germany
- Gerstner, Lea, Renal Division, Department of Medicine, Faculty of Medicine and Medical Center - University of Freiburg, Freiburg, Germany
- Kayser, Séverine, Renal Division, Department of Medicine, Faculty of Medicine and Medical Center - University of Freiburg, Freiburg, Germany
- Helmstädter, Martin, Renal Division, Department of Medicine, Faculty of Medicine and Medical Center - University of Freiburg, Freiburg, Germany
- Walz, Gerd, Renal Division, Department of Medicine, Faculty of Medicine and Medical Center - University of Freiburg, Freiburg, Germany
- Hermle, Tobias F., Renal Division, Department of Medicine, Faculty of Medicine and Medical Center - University of Freiburg, Freiburg, Germany
Background
Both mTor signaling and autophagy are important modulators of podocyte homeostasis, regeneration and aging, and have been implicated in glomerular diseases. However, the mechanistic role of these pathways for the glomerular filtration barrier remains poorly understood.
Methods
Drosophila presents a well-established model to study mTor signaling and autophagy with versatile genetic tools like tissue-specific RNAi-mediated knockdown or overexpression of wild type or functionally modified proteins. We used Drosophila nephrocytes as a podocyte model to investigate the connection of mTor signaling and autophagy and the homeostasis and maintenance of the nephrocyte ultrastructure and function as a storage kidney.
Results
We found that in the podocyte-like nephrocytes, mTor signaling positively controls cell size, survival and the extent of the subcortical actin network. Surprisingly, the inhibition of mTor signaling resulted in increased slit diaphragm spacing, whereas gain-of-function of mTor signaling did not affect slit diaphragm spacing, suggesting that additional cues limit the maximal density. Interestingly, both activation and inhibition of mTor signaling led to decreased nephrocyte function indicating that a fine balance of signaling activity is needed for proper function. We showed that basal autophagy in nephrocytes is required for survival and limits expression of sns (nephrin), but does not directly affect slit diaphragm formation or endocytic activity. However, using a genetic rescue approach, we demonstrated that excessive autophagy associated with loss of mTor function is primarily responsible for slit diaphragm misspacing.
Conclusion
Utilizing the Drosophila nephrocyte model to study the mechanistic role of mTor signaling and autophagy for the glomerular filtration barrier, we discovered a direct regulatory impact on the slit diaphragm architecture.