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Abstract: PO1098

Piezo1 in Intercalated Cells (ICs) Mediates Flow-Induced [Ca2+]i Transients in Mouse Cortical Collecting Duct (CCD)

Session Information

Category: Fluid, Electrolyte, and Acid-Base Disorders

  • 901 Fluid, Electrolyte, and Acid-Base Disorders: Basic

Authors

  • Carrisoza-Gaytan, Rolando, Icahn School of Medicine at Mount Sinai Department of Pediatrics, New York, New York, United States
  • Mutchler, Stephanie, University of Pittsburgh Department of Medicine, Pittsburgh, Pennsylvania, United States
  • Soong, Joanne, Icahn School of Medicine at Mount Sinai Department of Pediatrics, New York, New York, United States
  • Dalghi, Marianela G., University of Pittsburgh Department of Medicine, Pittsburgh, Pennsylvania, United States
  • Apodaca, Gerard, University of Pittsburgh Department of Medicine, Pittsburgh, Pennsylvania, United States
  • Kleyman, Thomas R., University of Pittsburgh Department of Medicine, Pittsburgh, Pennsylvania, United States
  • Satlin, Lisa M., Icahn School of Medicine at Mount Sinai Department of Pediatrics, New York, New York, United States
Background

Within the CCD, an acute increase in tubular fluid flow rate (TFFR) exposes principal cells (PCs) and ICs therein to hydrodynamic forces. In response, a biphasic increase in [Ca2+]i is observed, with an immediate high amplitude increase due to release of IP3-sensitive internal Ca2+ stores coupled to extracellular Ca2+ entry at the basolateral membrane. This is followed by a decay to a plateau level that is higher than baseline and sustained by luminal Ca2+ entry (Liu et al., 2003; 2005; 2007). This increase in [Ca2+]i is necessary for BK channel-mediated flow induced K+ secretion (FIKS) in the microperfused mammalian CCD. We have recently reported that PIEZO1, a mechanosensitive, Ca2+ permeable channel, is expressed on the basolateral membranes of PCs and ICs in the mouse CCD (Dalghi et al., 2019).

Methods

To examine whether IC Piezo1 expression contributes to the increase in [Ca2+]i triggered by TFFR, we generated a mouse with targeted deletion of Piezo1 in ICs (IC-Piezo1-KO).

Results

Immunofluorescence analyses of kidneys harvested from mice (C57BL/6) expressing PIEZO1-tdTomato revealed a significant increase of PIEZO1 expression in ICs from mice fed a high K (HK, 5% K+, n=4) vs. standard K (SK, 1% K+, n=4) diet for 10 days. Fluorescence intensity ratios (FIRs; ratio of the Ca2+ indicator Fura-2 emission signals measured at excitation wavelengths of 340 nm and 380 nm), corresponding to [Ca2+]i, were measured in individually identified PCs and ICs in CCDs isolated from (i) HK-fed IC-Piezo1-KO (n=3), (ii) SK-fed littermate control (n=3), and (iii) HK-fed control (n=3) mice and then exposed to the PIEZO1-activator Yoda1 (1 µM). PCs and ICs from HK-fed control mice exhibited a greater increase in [Ca2+]i in response to Yoda1 than SK-fed control mice (p≤0.001). However, ICs from HK-fed IC-Piezo1-KO mice exhibited a reduced or absent increase in [Ca2+]i in response to Yoda1 vs. SK-fed control mice (p≤0.001). In microperfused CCDs isolated from IC-Piezo1-KO mice, an increase in TFFR did not elicit a typical increase in [Ca2+]i in ICs (p≤0.001, n=3 controls and n=4 KOs).

Conclusion

We conclude that Piezo1 is upregulated in the CCD by a HK diet and contributes to the TFFR-induced increase in [Ca2+]i in ICs necessary for FIKS.

Funding

  • NIDDK Support