Kidney Week

Abstract: TH-OR105

Enhanced Protein Folding via XBP1 Activation Ameliorates ADPKD Due to PC1 Misfolding

Session Information

• PKD: Genetic, Mechanistic, and Clinical
  October 25, 2018 | Location: 25A, San Diego Convention Center
  Abstract Time: 05:18 PM - 05:30 PM

Category: Genetic Diseases of the Kidney

• 1001 Genetic Diseases of the Kidney: Cystic

Authors

• Krappitz, Matteus, Yale University , New Haven, Connecticut, United States

Matteus Krappitz, DrMed

• Staudner, Tobias, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany

Tobias Staudner,

• Westergerling, Parisa, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany

Parisa Westergerling,

• Hollmann, Till Amadeus, Yale School of Medicine, New Haven, Connecticut, United States

Till Amadeus Hollmann,

• Rümmele, David R., Yale university, New Haven, Connecticut, United States

David R. Rümmele,

• Roosendaal, Charlotte E.J., Yale University , New Haven, Connecticut, United States

Charlotte E.J. Roosendaal,

• Pedroso Balbo, Bruno Eduardo, Yale University, New Haven, Connecticut, United States

Bruno Eduardo Pedroso Balbo,

• Gallagher, Rachel, Yale University School of Medicine, New Haven, Connecticut, United States

Rachel Gallagher,

• Somlo, Stefan, Yale University , New Haven, Connecticut, United States

Stefan Somlo,

• Fedeles, Sorin V., Yale University School of Medicine, New Haven, Connecticut, United States

Sorin V. Fedeles,

Background

Pkd1 is one of the two genes responsible for autosomal dominant polycystic kidney disease (ADPKD). In ADPKD, ~30% of mutations are missense predicted to result in reduced PC1 function. XBP1 encodes the main chaperone modulator of the ER unfolded protein response. Here we investigated the role of XBP1 as a “genetic” chaperone therapy which may affect the levels of functional PC1 carrying patient derived missense mutations using the p.R2220W human REJ mutant (p.R2216W in mouse) as a representative candidate.

Methods

The effect of XBP1 on the expression and trafficking of the PC1-R2220W-V5 mutant was determined in vitro. A Pkd1^R2216W knock-in mouse model was generated. Using this backbone, Pkd1^R2216W/fl;Pkhd1-Cre and Pkd1^R2216W/fl;Pkhd1-Cre;XBP1-Rosa-floxstop-TG mice were examined by morphological, functional and biochemical analyses.

Results

Expression of XBP1 in transiently cells expressing PC1-R2220W-V5 leads to increased expression and GPS cleavage of the mutant protein. Ciliary trafficking of PC1-R2220W was markedly improved by co-expression of XBP1 as compared with PC1-R2220W alone. At P16, Pkd1^R2216W/fl;Pkhd1-Cre mice developed cystic disease compared with Pkd1^R2220W/+ animals as seen via a significant increase in renal parameters [KW/BW, 0.01±0.001 vs. 0.13±0.008, ****p<0.0001; BUN, 33.35±4.44 vs. 102.2±26.4, **p=0.0042; n=10, 7]. Expression of the conditional XBP1 transgene in Pkd1^R2216W/fl;XBP1-TG;Pkhd1-Cre mice at P16 led to a significant decrease in the cystic burden compared to the controls [KW/BW, 0.07±0.006 vs. 0.13±0.008, ****p<0.0001; BUN 50.57±8.47 vs. 102.2±26.49, *p=0.027, n=10, 7]. Using TUNEL and Ki67 assays we found that induction of XBP1 in the cyst lining cells led to a significant reduction in proliferation with no impact on apoptosis suggesting that the improved cystic phenotype in the Pkd1^R2216W/fl;XBP1-TG;Pkhd1-Cre animals is due to a reduction in cyst growth.

Conclusion

Our data raises the possibility that in vivo chaperone therapy for the treatment of ADPKD may have a beneficial role for a subset of PC1 missense mutations.

Funding

• NIDDK Support