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Abstract: SA-PO446

Ureteric Bud (UB) Prorenin Receptor (PRR) Directs UB Branching Morphogenesis by Regulating V-ATPase Activity and Autophagy in UB Cells

Session Information

Category: Development, Stem Cells, and Regenerative Medicine

  • 500 Development, Stem Cells, and Regenerative Medicine

Authors

  • Yosypiv, Ihor V., Tulane University, New Orleans, Louisiana, United States
  • Taylor, Renfang Song, Southwest Baptist University, Bolivar, Missouri, United States
  • Nakhoul, Nazih L., Tulane Medical School, New Orleans, Louisiana, United States
Background

Targeted ablation of the PRR in the UB lineage in Hoxb7Cre/PRRflox/flox (PRRUB-/-) mice causes severe defects in UB branching, leading to decreased nephron endowment and renal hypodysplasia. Since PRR is an accessory subunit of the vacuolar proton pump V-ATPase, we investigated the role of V-ATPase and autophagy in PRR-induced UB branching in mice.

Methods

UB cells were FACS-isolated from Hoxb7Cre+/GFP+/PRRflox/flox (PRRUB-/-) and control (PRRUB+/+) littermates at birth (P0). V-ATPase subunit expression in isolated cells was determined by microarray and validated by real-time RT-PCR. PRR knockdown in immortalized UB cells (iUBc) was achieved with adenovirus-driven short hairpin RNA (shPRR). Effect of PRR knockdown on cell pH and V-ATPase activity was determined by staining with Lysotracker (a lysosomal pH marker) and from measurements of Na-independent cell pH recovery rates after intracellular acidification with a NH4Cl prepulse.

Results

Expression of V-ATPase subunits Atp6ap2 (PRR), V0a4, V0b, V1b1 and V1g1 was reduced in PRRUB-/- compared to PRRUB+/+ UB cells. shPRR decreased mRNA levels of PRR by 80-90% and of kidney-specific α4 V-ATPase subunit by 50% compared to control scrambled control PRR (scPRR) virus in iUBc. shPRR decreased Lysotracker fluorescence in iUBc compared to scPRR (p<0.001). Intracellular pH (pHi) measurements (by BCECF fluorescence) indicated slower recovery from acid loads in shPRR-treated cells due to reduced V-ATPase activity. Immunofluorescence of key autophagy protein LAMP2 was increased in the UB of PRRUB-/- compared to PRRUB+/+ kidneys on E14.5, consistent with autophagic defects in UB cells in PRRUB-/- kidneys.

Conclusion

PRR knockdown decreases expression of α4 subunit of V-ATPase and suppresses V-ATPase activity in iUB cells in vitro, resulting in deacidification of intracellular vesicles. We propose that endogenous UB PRR regulates normal UB branching morphogenesis through stimulation of V-ATPase activity, control of lysosomal pH and appropriate autophagic flux in UB cells.