Distal convoluted tubule Cl⁻concentration is modulated via K⁺channels and transporters

Abstract

Cl--sensitive with-no-lysine kinase (WNK) plays a key role in regulating the thiazide-sensitive sodium-chloride cotransporter (NCC) in the distal convoluted tubule (DCT). Cl- enters DCT cells through NCC and leaves the cell across the basolateral membrane via the Cl- channel ClC-Kb or a K-Cl cotransporter (KCC). While KCC is electroneutral, Cl- exit via ClC-Kb is electrogenic. Therefore, an alteration in DCT basolateral K+ channel activity is expected to influence Cl- movement across the basolateral membrane. Although a role for intracellular Cl- in the regulation of WNK and NCC has been established, intracellular Cl- concentrations ([Cl-]i) have not been directly measured in mammalian DCT. Therefore, to measure [Cl-]i in DCT cells, we have generated a transgenic mouse model expressing an optogenetic kidney-specific Cl-Sensor and measured Cl- fluorescent imaging in the isolated DCT. Basal measurements indicate that the mean [Cl-]i is approximately 7 mM. Stimulation of chloride exit with low chloride hypotonic solutions decreased [Cl-]i, whereas inhibition of KCC by DIOA or inhibition of ClC-Kb by NPPB increased [Cl-]i, suggesting roles for both KCC and ClC-Kb modulating [Cl-]i . Blocking the basolateral K+ channels, Kir4.1/5.1, with barium significantly increased the [Cl-]i. Finally, a decrease in extracellular K+ concentration transiently decreased [Cl-]i whereas raising extracellular K+ transiently increased [Cl-]i, further suggesting a role for Kir4.1/5.1 in the regulation of [Cl-]i. We conclude that the alteration in ClC-Kb, KCC and Kir4.1/5.1 activity influences the [Cl-]i in the DCT.

Potassium Effects on NCC Are Attenuated during Inhibition of Cullin E3–Ubiquitin Ligases

“…Dietary changes in K + supplementation in mice alters WNK4 phosphorylation [ 7 , 51 ], and WNK4 -/- mice do not increase NCC abundance after a low K + diet [ 52 ], suggesting that K + modulates NCC activity via alterations in the activity of WNK kinases. This alteration in WNK kinase activity is mediated, at least in part, through alterations in the activity of the basolateral K + channels Kir 4.1 and Kir 5.1 (forming a Kir 4.1/5.1 heterodimer) and alterations in the intracellular concentration of Cl − ([Cl − ]i) [ 7 , 13 , 53 , 54 ]. Supporting this, the inhibitory effects of a high K + diet on NCC phosphorylation and abundance are greatly diminished in Kir4.1 or Kir5.1 knockout mice [ 14 , 53 ], and the effects of acute K + loading to reduce NCC phosphorylation are not observed in Cl − -insensitive WNK4 mice [ 55 ].…”

Potassium effects on NCC are attenuated during inhibition of Cullin E3-ubiquitin ligases

“…Dietary changes in K + supplementation in mice alters WNK4 phosphorylation [7, 50] and WNK4 -/- mice do not increase NCC abundance after a low K + diet [51], suggesting that K + modulates NCC activity via alterations in the activity of WNK kinases. This alteration in WNK kinase activity is mediated, at least in part, through alterations in activity of the basolateral K + channels Kir 4.1 and Kir 5.1 (forming a Kir4.1/5.1 heterodimer) and alterations in the intracellular concentration of Cl − ([Cl − ] i ) [7, 13, 52, 53]. Supporting this, the inhibitory effects of a high K + diet on NCC phosphorylation and abundance are greatly diminished in Kir4.1 or Kir5.1 knockout mice [14, 52] and the effects of acute K + loading to reduce NCC phosphorylation are not observed in Cl - -insensitive WNK4 mice [54].…”

The Role of the Renal Dopaminergic System and Oxidative Stress in the Pathogenesis of Hypertension

“…In the renal cortical collecting duct, D 2 R (isoform not determined) inhibits basolateral K + channels Kir4.1/5.1 and Kir4.1 channels [ 201 ] that can eventually affect NCC and chloride-channel protein Cl-Kb activities [ 202 , 203 ]. In the cortical collecting duct, the D 1 -like but not D 2 -like receptors can inhibit Na + /K + -ATPase activity [ 204 ].…”