Kidney Week

Abstract: TH-PO676

The Role of LKB1-AMPK Signaling on Renal mTOR and Cyst Progression in ADPKD

Session Information

• ADPKD: Genetic and Model Studies
  October 25, 2018 | Location: Exhibit Hall, San Diego Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Genetic Diseases of the Kidney

• 1001 Genetic Diseases of the Kidney: Cystic

Authors

• Zhang, Yan, University of Kansas Medical Center, Kansas City, Kansas, United States

Yan Zhang,

• Dai, Yuqiao, University of Kansas Medical Center, Kansas City, Kansas, United States

Yuqiao Dai,

• Reif, Gail, University of Kansas Medical Center, Kansas City, Kansas, United States

Gail Reif,

• Daniel, Emily A., University of Kansas Medical Center, Kansas City, Kansas, United States

Emily A. Daniel,

• Khanna, Aditi, University of Kansas Medical Center, Kansas City, Kansas, United States

Aditi Khanna,

• Magenheimer, Brenda S., University of Kansas Medical Center, Kansas City, Kansas, United States

Brenda S. Magenheimer,

• Wallace, Darren P., University of Kansas Medical Center, Kansas City, Kansas, United States

Darren P. Wallace,

Background

In ADPKD, the mTOR pathway is thought to contribute to cyst epithelial cell proliferation and cyst growth. Downstream components of the mTOR pathway, i.e. ribosomal protein S6, are aberrantly phosphorylated in cyst-lining cells. Fluid accumulation within the cyst cavity is driven by Cl^- secretion via apical CFTR Cl^- channels. AMP Kinase (AMPK) is an important negative regulator of both mTOR and CFTR. Liver Kinase B1 (LKB1), a well-known tumor suppressor, directly phosphorylates and activates AMPK. Previously, we showed that BIT-11, a novel small molecule LKB1 activator, increased P-AMPK and decreased P-S6 in human ADPKD cells. BIT-11 decreased ADPKD cell proliferation, Cl^- secretion and in vitro cyst growth and blocked cyst-like tubule dilations in Pkd1^-/- mouse kidneys in metanephric organ culture. Our hypothesis is that the LKB1-AMPK pathway regulates mTOR-mediated cell proliferation and CFTR-dependent fluid secretion by cystic cells and modulates ADPKD progression.

Methods

An inducible LKB1 knockout cell line was generated from Lkb1^flox/flox:ROSA26-Cre^ERT2 mouse kidneys. To determine if the loss of LKB1 is sufficient to induce cystic disease, we crossed Lkb1^flox/flox and Pkhd1-Cre mice to knock out LKB1 selectively in collecting ducts (CDs). To test the effect of direct LKB1 activation, BIT-11 was delivered by daily gavage from 5 to 20 weeks to Pkd1^RC/RC:Pkd2^+/- mice, an ADPKD model that develops a renal cystic disease by 5 weeks of age and a progressive decline in renal function.

Results

Lkb1^flox/flox:ROSA26-Cre^ERT2 renal cells were treated with tamoxifen to delete LKB1 expression. The loss of LKB1 significantly decreased P-AMPK, but had no effect on mTOR signaling. CD-specific knockout of LKB1 in otherwise normal mice resulted in hydronephrosis; however, renal cyst formation was not observed. On the other hand, treatment with BIT-11 caused a significant decrease in kidney weight (percent body weight), blood urea nitrogen and interstitial fibrosis in Pkd1^RC/RC:Pkd2^+/- mice.

Conclusion

The LKB1-AMPK pathway does not appear to regulate basal mTOR activity in the adult kidney; however, direct activation of this pathway using a novel LKB1 activator decreased mTOR-mediated cell proliferation and the decline in renal function in ADPKD mice, suggesting that this may be a potential therapeutic approach for the treatment of ADPKD.

Funding

• NIDDK Support