Abstract: FR-PO769
Influence of Mitochondrial Signals on Metabolic Signaling Pathways in Podocytes
Session Information
- Glomerular Diseases: Mechanisms and Podocyte Biology
October 25, 2024 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Glomerular Diseases
- 1401 Glomerular Diseases: Mechanisms, including Podocyte Biology
Authors
- Reitmeier, Katrin, University of Cologne Center for Molecular Medicine Cologne, Cologne, Nordrhein-Westfalen, Germany
- Odenthal, Johanna, University of Cologne Center for Molecular Medicine Cologne, Cologne, Nordrhein-Westfalen, Germany
- Schermer, Bernhard, University of Cologne Center for Molecular Medicine Cologne, Cologne, Nordrhein-Westfalen, Germany
- Benzing, Thomas, University of Cologne Center for Molecular Medicine Cologne, Cologne, Nordrhein-Westfalen, Germany
- Brinkkoetter, Paul T., University of Cologne Center for Molecular Medicine Cologne, Cologne, Nordrhein-Westfalen, Germany
Group or Team Name
- Nephrolab Cologne.
Background
Mitochondrial signals are of interest in podocyte research due to the identification of single gene mutations associated with glomerular diseases, including a cluster of genes linked to mitochondrial dysfunction. We recently identified a link between structurally impaired mitochondria due to the loss of PHB2, a protein essential for the fusion of mitochondria, and hyperactivation of the Insulin signaling cascade in Phb2 deficient podocytes. The mouse model revealed that hyperactive Insulin signaling causes a severe glomerular phenotype and premature death of the animals. This phenotype was ameliorated by blocking of insulin receptor signaling via double knockout of the Insulin and IGF-1 receptor (Ising et al. 2015).
Methods
We use Drosophila melanogaster nephrocytes to examine the signaling mechanism from dysfunctional mitochondria to the Insulin receptor. These podocyte-equivalent cells exhibit functional and structural similarities with mammalian podocytes, making them an established model for podocyte research. We employ nephrocyte-specific RNAi-mediated knockdown and simultaneous overexpression of target genes. The effects are assessed by performing fluorescent tracer uptake assay and immunofluorescence staining to evaluate nephrocyte filter function and morphology.
Results
We successfully replicated the phenotype observed in the PHB2 knockout mouse model in nephrocytes. Phb2 depletion led to a functional and morphological phenotype, and insulin signaling hyperactivation. We were able to interfere with and rescue this phenotype by overexpressing a functionally disabled insulin receptor variant. Notably, elevated ROS levels were observed upon Phb2 knockdown, even when insulin signaling was blocked. We hypothesized that ROS transduce a signal from dysfunctional mitochondria to the insulin receptor. To test this, we overexpressed SOD1 in the Phb2 knockdown background, which depleted ROS levels and significantly rescued the Phb2 phenotype.
Conclusion
Our results demonstrate that nephrocytes are a suitable model to study the link between dysfunctional mitochondria and insulin signaling hyperactivation. We propose a signaling mechanism where mitochondrial dysfunction elevates mitochondrial ROS levels, sensitizing podocytes to insulin signaling by targeting the insulin receptor and initiating receptor autophosphorylation.
Funding
- Government Support – Non-U.S.