Abstract: TH-PO598
mTORC2 (Rictor) Knockout Decreases the Cystic Phenotype in Pkd1-/- Mice
Session Information
- Cystic Kidney Diseases - I
November 02, 2017 | Location: Hall H, Morial Convention Center
Abstract Time: 10:00 AM - 10:00 AM
Category: Genetic Diseases of the Kidney
- 801 Cystic Kidney Diseases
Authors
- Holditch, Sara, UC Denver Anschutz Medical Campus, Aurora, Colorado, United States
- Brown, Carolyn Nicole, UC Denver Anschutz Medical Campus, Aurora, Colorado, United States
- Ravichandran, Kameswaran, Hera BioLabs, Lexington, Kentucky, United States
- Edelstein, Charles L., UC Denver Anschutz Medical Campus, Aurora, Colorado, United States
Background
mTOR exists in two distinct structural and functional complexes mTORC1 (Raptor) and mTORC2 (Rictor-Rapamycin-independent companion of mTOR). We have shown that mTOR kinase inhibition, capable of inhibiting both Raptor and Rictor, reduces cyst growth. However, the effect of mTORC2 (Rictor) inhibition alone on PKD is not known. The aim of our study was to determine the effect of Rictor-/- on the cystic phenotype of Pkd1-/- mice.
Methods
Expression of kidney specific Cre recombinase, with Tamoxifen administration on days 19-21, in Pkd1 fl/fl mice results in Pkd1-/- mice that have a slow onset of cystic disease with severe PKD and renal failure at 130 days post tamoxifen injection. To determine if the effect of Rictor-/- on the cystic phenotype of Pkd1-/-mice, Rictor fl/fl mice were bred with the Pkd1 fl/fl; KspCad-CreERT2 mice to develop Rictor fl/fl, Pkd1 fl/fl; KspCad-CreERT2 mice treated with tamoxifen to develop kidney-specific Rictor-/-Pkd1-/- mice and aged to 150 days post Tamoxifen. Non-invasive quantitative assessment of cyst development per kidney at 90 days, a time when nascent cysts are forming, was performed by T2-weighted and FISP-MRI at 4.7 Tesla.
Results
Genetic deletion of mTORC2 (Rictor) in Pkd1-/-mice results in significantly lower kidney weight, cyst volume, number of cysts and SCr. (See Table)
Conclusion
Study of signaling pathways downstream of mTORC2 (pAkt, SGK1, PKCα) and a head to head study of sirolimus (Raptor inhibitor) VS. new generation mTOR kinase inhibitors (inhibit both Raptor and Rictor) is warranted to better understand the pathways responsible for PKD cyst expansion.
| Wild type (n=8) | Pkd1-/- (n=9) | Pkd1-/- Rictor-/- (n=6) | |
| Body wt (g) | 30 | 27 | 32 |
| 2K (g) | 0.35 | 0.53 | 0.36* |
| 2K/TBW (%) | 1.1 | 2.0 | 1.2* |
| Cyst volume (%) | 0 | 40.1 | 14.6* |
| No of cysts/kidney | 0 | 5.3 | 0.8* |
| Heart wt (g) | 0.3 | 0.15 | 0.17 |
| BUN (mg/dL) | 24 | 29 | 25 |
| SCr (mg/dL) | 0.22 | 0.33 | 0.2* |
2K/TBW (%) Two kidney/total body weight, *p<0.05 vs. Pkd1-/-
Funding
- Other U.S. Government Support