Abstract: FR-PO705
Mitochondrial ROS Sensitize Podocytes to Insulin Resulting in mTOR Activation
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
- Odenthal, Johanna, Uniklinik Koln, Koln, Nordrhein-Westfalen, Germany
- Reitmeier, Katrin, Uniklinik Koln, Koln, Nordrhein-Westfalen, Germany
- Kuehne, Lucas, Uniklinik Koln, Koln, Nordrhein-Westfalen, Germany
- Schermer, Bernhard, Uniklinik Koln, Koln, Nordrhein-Westfalen, Germany
- Benzing, Thomas, Uniklinik Koln, Koln, Nordrhein-Westfalen, Germany
- Brinkkoetter, Paul T., Uniklinik Koln, Koln, Nordrhein-Westfalen, Germany
Background
Beyond their contribution to maintaining cellular ATP levels, mitochondria have been recognized as signaling hubs regulating podocyte function in states of health and disease. Recently, we established podocyte specific Phb2 deficient mice as in vivo model to study dysfunctional mitochondria and their impact on podocyte metabolism. PHB2 acts as scaffold protein at the inner mitochondrial membrane and is required for proper fusion and function of mitochondria. Loss of PHB2 resulted in hyperactive Insulin/IGF1 signaling and increased mTOR activation in podocytes (Ising et al. EMBO Mol Med 2015).
Methods
To further elucidate the molecular mechanisms by which mitochondria orchestrate the podocytes’ response to insulin, we employed Drosophila melanogaster as a model and studied nephrocytes, podocyte-equivalent cells of the fly, responsible for filtration of the hemolymph. Cell-specific RNAi-mediated knockdown and simultaneous overexpression of candidate genes enabled us to investigate genetic interactions to identify the mitochondrial signaling cascade leading to the observed insulin hypersensitivity and subsequent mTOR activation.
Results
Knockdown of Drosophila Phb2 in nephrocytes leads to severe functional and morphological defects mimicking the published mammalian phenotype and confirming the feasibility of this approach. Simultaneous overexpression of a dominant-negative form of the Insulin-Receptor ameliorated both, functional and morphological defects in Phb2 deficient nephrocytes emphasizing the impact of hyperactive insulin signaling on the disease phenotype. Last, we tested the hypothesis, that increased mitochondrial ROS might lead to an autophosphorylation of the Insulin-Receptor and thereby enhance the intracellular insulin cascade upon binding of exogenous insulin. To this end, we overexpressed Drosophila Sod1 in the Phb2-knockdown background and observed a significant rescue effect.
Conclusion
Our results underline the importance of mitochondria as signaling hubs for nephrocyte/podocyte biology. The impact of mitochondria on metabolic signaling events can be recapitulated in Drosophila and appears to be conserved throughout evolution. Using Drosophila nephrocytes, we could identify mitochondrial ROS as important intracellular signal component leading to hyperactivation of the Insulin-Receptor and mTOR activation.