Kidney Week

Abstract: TH-OR26

ClC-K2 Chloride Channel Determines Acid-Base Transport and Chloride Reabsorption in Intercalated Cells of the Collecting Duct

Session Information

• Molecular Insights in Ion, Acid, and Water Handling
  October 22, 2020 | Location: Simulive
  Abstract Time: 05:00 PM - 07:00 PM

Category: Fluid, Electrolyte, and Acid-Base Disorders

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

Authors

• Hassanzadeh Khayyat, Naghmeh, University of Texas John P and Katherine G McGovern Medical School, Houston, Texas, United States

Naghmeh Hassanzadeh Khayyat, PhD



Current position: Postdoctoral Research Fellow at McGovern Medical school, UTHSC at Houston, Texas Ph.D. in Cell and Molecular Biology (2019), University of Houston, Houston, Texas M.S. in Cell Biology (2013), Illinois Institute of Technology, Chicago, Illinois B.S. in Cell and Molecular Biology (2011), University of Tehran, Tehran, Iran

• Tomilin, Victor N., University of Texas John P and Katherine G McGovern Medical School, Houston, Texas, United States

Victor N. Tomilin,

• Zaika, Oleg L., University of Texas John P and Katherine G McGovern Medical School, Houston, Texas, United States

Oleg L. Zaika,

• Pochynyuk, Oleh, University of Texas John P and Katherine G McGovern Medical School, Houston, Texas, United States

Oleh Pochynyuk,

Background

Intercalated cells (ICs) of the collecting duct (CD) play a critical role in regulation of systemic acid-base homeostasis. In addition, ICs are capable of performing trans-cellular Cl^- reabsorption particularly during volume depletion. While the major apical membrane transport systems are well characterized, little is known about mechanisms and contribution of the basolateral membrane in both processes. Kidney specific ClC-K2 is expressed in the basolateral membrane of the distal nephron segments, including the CD.

Methods

We generated ClC-K2 deficient mice using cre-loxP strategy to investigate the role of the channel in acid-base and Cl^- transport. We combined BCECF-sensitive intracellular pH (pH_i) measurements with fluorescent AQP2-based identification of principal cells (PCs) and ICs to assess ClC-K2-dependent pH_i changes in different cell types.

Results

ClC-K2 inhibition with NPPB (100 μM) had no effect in PCs of WT mice, whereas it induced rapid intracellular acidification in B-type and alkalization in A-type of ICs. NPPB failed to significantly affect pH_i in CDs from ClC-K2 deficient mice. Extracellular Cl^- removal to drive basolateral Cl^- exit via ClC-K2 had no effect on pH_i in PCs, but caused alkalization in B-type and acidification in A-type of ICs. Importantly, Cl^- removal did not induce pH_i changes in both A- and B-type of ICs from ClC-K2 deficient mice. This suggests that ClC-K2 mediates trans-cellular Cl^- reabsorption and determines apical acid-base transport by controlling intracellular Cl^- concentration. Moreover, application of Angiotensin II (Ang II, 500 nM) increased ClC-K2 single channel activity and augmented respective ClC-K2-dependent pHi changes in B- but not A-type of ICs to favor apical Cl^-/HCO₃^- exchange. In addition, induction of metabolic acidosis with NH₄Cl supplementation in water, increases H⁺ secretion from ICs of WT but not ClC-K2 deficient mice. Furthermore, ClC-K2 activity (measured as NPPB-dependent pH_i changes) was increased in A-type but decreased in B-type of ICs, overall favoring urinary acidification in WT mice.

Conclusion

Altogether, our results show that ClC-K2 is central for acid-base transport in the CD. ClC-K2 activity can be independently regulated in A- and B-type of ICs during different physiological conditions to allow fine tuning of renal acid-base handling.

Funding

• Other NIH Support