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Kidney Week

Abstract: TH-OR38

The C-Terminal Tail of Polycystin 1 Rescues Cystic Phenotype in a Mitochondrial Enzyme-Dependent Fashion

Session Information

Category: Genetic Diseases of the Kidneys

  • 1001 Genetic Diseases of the Kidneys: Cystic

Authors

  • Onuchic, Laura, Yale University School of Medicine, New Haven, Connecticut, United States
  • Padovano, Valeria, Yale University School of Medicine, New Haven, Connecticut, United States
  • Schena, Giorgia, Yale University School of Medicine, New Haven, Connecticut, United States
  • Rajendran, Vanathy, Yale University School of Medicine, New Haven, Connecticut, United States
  • Gresko, Nikolay P., Yale University School of Medicine, New Haven, Connecticut, United States
  • Dong, Ke, Yale University School of Medicine, New Haven, Connecticut, United States
  • Shi, Xiaojian, Yale University School of Medicine, New Haven, Connecticut, United States
  • Shen, Hongying, Yale University School of Medicine, New Haven, Connecticut, United States
  • Somlo, Stefan, Yale University School of Medicine, New Haven, Connecticut, United States
  • Caplan, Michael J., Yale University School of Medicine, New Haven, Connecticut, United States
Background

Approximately 85% of Autosomal Dominant Polycystic Kidney Disease (ADPKD) cases are caused by mutations in PKD1, which encodes polycystin-1 (PC1). PC1 is a large transmembrane protein that undergoes C-terminal cleavage, generating fragments (PC1-CTT) that translocate to mitochondria and nucleus. We find that PC1-CTT expression in an inducible PC1 KO ADPKD mouse model substantially rescues cystic phenotype and we elucidate mechanisms involved in this effect.

Methods

We generated BAC transgenic mice expressing a Flox-Stop 2HA-PC1-CTT inserted in the Rosa26 locus and crossed it with the inducible Pax8rtTA; TetO-Cre; Pkd1fl/fl ADPKD mouse model. Doxycycline induction of these mice (PC1-CTT; Pax8rtTA; TetO-Cre; Pkd1fl/fl on the C57BL6N background) leads to PC1-CTT expression in renal epithelial cells that lack full-length PC1. We applied MS-based proteomics and Co-IP techniques to identify PC1-CTT interactors and used MS-based metabolomics to identify mitochondrial differences associated with the observed phenotype.

Results

Compared to PC1 KO mice, PC1 KO mice expressing PC1-CTT have 3-fold lower kidney weight/body weight ratio (5.10% vs 14.85%, p<0.0001) and 3.6-fold lower BUN (32.7mg/dL vs 120.7mg/dL, p=0.0008), with both groups presenting comparable gender distributions. BUN levels in PC1-CTT-expressing ADPKD mice are comparable to those in WT controls. We show that PC1-CTT interacts with mitochondrial enzyme Nicotinamide Nucleotide Transhydrogenase (NNT) and confirm the importance of this interaction by crossing the same PC1-CTT expressing PC1 KO mice with NNT-deficient C57BL6J mice. These mice do not exhibit an improved cystic phenotype. Both in vivo and in vitro, PC1-CTT re-expression in the presence of NNT leads to increased mitochondrial mass, altered redox modulation, increased assembly of ATP synthase at a "per mitochondria" level as well as decreased tubular proliferation, suggesting potential mechanisms for the observed rescue. Finally, unbiased metabolomics reveals that PC1-CTT's ability to rescue the ADPKD metabolic profile is tied to the presence of NNT.

Conclusion

Expression of PC1-CTT and its interaction with NNT significantly rescues ADPKD renal phenotype. Considering its small size, PC1-CTT could be explored as a gene therapy approach for ADPKD.

Funding

  • NIDDK Support