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Abstract: TH-PO474

Molecular Mechanisms of Novel NPHS2 Pathogenic Variants and Proposed Therapeutic Interventions

Session Information

Category: Genetic Diseases of the Kidneys

  • 1202 Genetic Diseases of the Kidneys: Non-Cystic

Author

  • Abu-Maziad, Asmaa Soliman, The University of Arizona Health Sciences, Tucson, Arizona, United States
Background

The human NPHS2 gene encodes podocin protein, an essential component of GBM. Mutations in NPHS2 causes steroid-resistant FSGS/nephrotic syndrome. Podocin signaling is essential to the structure and function of glomerular podocytes. Defining the molecular dysfunctions of this novel NPHS2 mutations is imperative to improving our understanding of the dynamic roles of podocin protein and potential therapeutic interventions.

Methods

We study the molecular and biochemical properties of the NPHS2 pathogenic variants and podocin protein using patient-derived induced pluripotent stem cell (piPSC) and reprogrammed podocytes. To further study the implications of the W122S mutation, in silico analysis was performed. ColabFold was used to predict the structure of wild-type podocin and W122S mutated podocin.

Results

Try122 is located in podocin’s transmembrane region, where the protein inserts itself into the inner leaflet of the plasma membrane. It is here where podocin recruits nephrin and CD2AP into lipid rafts, forming a multiprotein signaling complex. This complex was found to be integral in the formation of the podocyte’s actin cytoskeleton. Given its predicted location on the outer surface of the transmembrane region of podocin, Try122 supports podocin’s ability to embed itself in the plasma membrane.

Conclusion

Distinct differences in lipophilicity and structure of the transmembrane domain are revealed. Further work using our patient`s derived stem cell will allow us to understand the signaling cascade and therapies.

Structure prediction results of wild type podocin residues and their respective mutations. Visualized with hydrophobicity maps on surfaces and contacted residues. A. Transmembrane tryptophan 122 contacting Ser120 and Phe119. B. Podocin mutant W122S contacting Phe119 and losing contact with Ser120. Distinct differences in lipophilicity and structure of the transmembrane domain are visible. C. Glutamic acid 178 protrudes from PHB domain and contacts Met187. D. E178D mutant shows a similar structure to wild type form and maintains contact with Met187.