Kidney Week

Abstract: SA-PO466

The Consequences of Decreased Cap-Dependent Translation in Polycystic Kidney Disease

Session Information

• Cystic Kidney Diseases: Basic/Translational
  November 09, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Genetic Diseases of the Kidneys

• 1001 Genetic Diseases of the Kidneys: Cystic

Authors

• Holditch, Sara, UC Denver Anschutz Medical Campus, Aurora, Colorado, United States

Sara Holditch,

• Brown, Carolyn Nicole, UC Denver Anschutz, Aurora, Colorado, United States

Carolyn Nicole Brown,

• Atwood, Daniel, University of Colorado Anschutz, Aurora, Colorado, United States

Daniel Atwood,

• Hopp, Katharina, University of Colorado Denver, AMC, Aurora, Colorado, United States

Katharina Hopp,

• Edelstein, Charles L., University of Colorado Denver, Aurora, Colorado, United States

Charles L. Edelstein,

Background

Autosomal Dominant Polycystic kidney disease (ADPKD) is the most common life-threatening hereditary disease, characterized by cyst formation and growth. Unchecked proliferation of cystic epithelial cells is a major contributor to cyst growth. At the nexus of regulating proliferation is the 4E-BP1 pathway, a crucial checkpoint in cap-dependent protein translation and proliferation. We demonstrate on immunohistochemistry staining that ADPKD mice and rat models, ADPKD patient renal biopsies, and PKD1^-/- cells exhibit hyperphosphorylated 4E-BP1, a biomarker of increased translation and proliferation. We hypothesized that expression of constitutively active 4E-BP1 constructs (4E-BP1^F113A and 4E-BP1^R13AF113A) would repress translation, decrease proliferation, and reduce cyst expansion.

Methods

In the orthologous ADPKD model, the C57BL/6 Pkd1^RC/RC mouse, we determined the effect of 4E-BP1^F113A on cystic disease (on MRI scan).

Results

Unexpectedly, relative to controls, 4E-BP1^F113A resulted in increased cyst burden (%) (48±5 vs. 72±6*), decreased functional parenchyma (%) (46±7 vs 22±5*, suppressed TUNEL staining (% positive cyst epithelium, 24±9 vs. 36±14*), and increased Bcl-2 expression (relative densitometry units, 12±2 vs. 8±2*). Values are means of control treated, and 4E-BP1^F113A treated Pkd1^RC/RC ± SEM, *p<0.05.

Conclusion

To determine the mechanism of 4E-BP1^F113A enhanced PKD, we performed in vitro studies in ADPKD patient cells. In vitro, 4E-BP1^F113A and 4E-BP1^R13AF113A significantly repressed cap-dependent translation as anticipated (57% mean reduction across 3 cyst cell lines). However, 4E-BP1 transduction increased mTOR signaling, enhanced proliferation, decreased apoptosis, impaired NADPH oxidoreductase activity and increased superoxide production. Reduced 4E-BP1 expression reversed the in vitro phenotype. These results demonstrate the importance of cap-dependent translation in PKD cyst lining epithelial cells

Funding

• Other U.S. Government Support