Abstract: FR-PO718
Geranylgeranylation of Small GTPase Is Critical to Preserving the Glomerular Filtration Barrier Integrity
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
- Boi, Roberto, University of Gothenburg, Institute of Neurosciences and Physiology, Gothenburg, Sweden
- Bergwall, Lovisa, University of Gothenburg, Institute of Neurosciences and Physiology, Gothenburg, Sweden
- Ebefors, Kerstin, University of Gothenburg, Institute of Neurosciences and Physiology, Gothenburg, Sweden
- Nystrom, Jenny C., University of Gothenburg, Institute of Neurosciences and Physiology, Gothenburg, Sweden
- Buvall, Lisa, University of Gothenburg, Institute of Neurosciences and Physiology, Gothenburg, Sweden
Background
Actin cytoskeleton maintenance in podocytes is carefully and yet dynamically regulated by RhoGTPases Rac1, Cdc42, and RhoA and other small GTPases such as Rap1. These GTPases are commonly post-translational modified by geranylgeranyltransferase type-I (GGTase-I) or farnesyltransferase (FTase), which covalently transfer respectively a geranylgeranyl or a farnesyl to their target GTPases. These modifications are known as prenylation and are known to have a regulatory activity on small GTPases. Our hypothesis is that prenylation plays an important role in the regulation of normal glomerular permselectivity and that dysregulation leads to proteinuria and progression of glomerular disease.
Methods
The glomerular expression of GGTase-I was localized using immunofluorescence. Podocyte-specific GGTase-I and FTase knockout mice were generated. Albuminuria and foot process effacement (TEM) were used to investigate filtration barrier function. Depletion of GGTase-I was studied also in vitro using an inhibitor or with knockdown of gene expression. Immunofluorescence was used to analyze modifications of the actin cytoskeleton and β1 integrin localization.
Results
GGTase-I was found to be expressed mainly by the podocytes in the human glomerulus. In vivo experiments in mice showed that GGTase-I knockout caused early-onset progressive albuminuria, accompanied by foot process effacement, while littermate controls and FTase knockout mice did not. In vitro, GGTase-I knockdown or inhibition markedly increased RhoA, Rac1, Cdc42, and Rap1 activation. This caused actin cytoskeleton disruption and altered β1 integrin distribution.
Conclusion
In podocytes, geranylgeranylation was shown to be important in maintaining the balance of RhoGTPases and Rap1 and to be crucial for maintaining glomerular integrity and function.
Funding
- Government Support – Non-U.S.