Cyclic AMP promotes cyst growth in polycystic kidney disease (PKD) by stimulating cell proliferation and fluid secretion. Previously, we showed that the primary cilium of renal epithelial cells contains a cAMP regulatory complex comprising adenylyl cyclases 5 and 6 (AC5/6), polycystin-2, A-kinase anchoring protein 150, protein kinase A, and phosphodiesterase 4C. In Kif3a mutant cells that lack primary cilia, the formation of this regulatory complex is disrupted and cAMP levels are increased. Inhibition of AC5 reduces cAMP levels in Kif3a mutant cells, suggesting that AC5 may mediate the increase in cAMP in PKD. Here, we examined the role of AC5 in an orthologous mouse model of PKD caused by kidney-specific ablation of Pkd2. Knockdown of AC5 with siRNA attenuated the increase in cAMP levels in Pkd2-deficient renal epithelial cells. Levels of cAMP and AC5 mRNA transcripts were elevated in the kidneys of mice with collecting duct-specific ablation of Pkd2. Compared with Pkd2 single mutant mice, AC5/Pkd2 double mutant mice had less kidney enlargement, lower cyst index, reduced kidney injury, and improved kidney function. Importantly, cAMP levels and cAMP-dependent signaling were reduced in the kidneys of AC5/Pkd2 double mutant compared to the kidneys of Pkd2 single mutant mice. Additionally, we localized endogenous AC5 in the primary cilium of renal epithelial cells and showed that ablation of AC5 reduced ciliary elongation in the kidneys of Pkd2 mutant mice. Thus, AC5 contributes importantly to increased renal cAMP levels and cyst growth in Pkd2 mutant mice, and inhibition of AC5 may be beneficial in the treatment of PKD.
Bibliographical noteFunding Information:
Research reported in this publication was supported by the National Institutes of Health under award number R37DK042921 (P.I.) and the UT Southwestern O’Brien Kidney Research Core Center (P30DK079328). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. We thank Drs Kirk Hammond and Tong Tang (University of California, San Diego) for providing the AC5 knockout mice, Dr. William Snell (UT Southwestern) for the antibody against IFT140, Dr Karam Aboudehen (University of Minnesota) for critically reviewing the manuscript, the UT Southwestern Live Cell Imaging Core Facility for image analysis, and Matanel Yheskel for expert technical assistance.
SS receives equity and consulting fees from Goldfinch Biopharma. VP is a consultant and receives grant support from Regulus Therapeutics. All the other authors declared no competing interests.
© 2017 International Society of Nephrology
- adenylyl cyclase
- cyclic AMP
- knockout mice
- polycystic kidney disease