KCNJ10 determines the expression of the apical Na-Cl cotransporter (NCC) in the early distal convoluted tubule (DCT1)

Abstract

The renal phenotype induced by loss-of-function mutations of inwardly rectifying potassium channel (Kir), Kcnj10 (Kir4.1), includes salt wasting, hypomagnesemia, metabolic alkalosis and hypokalemia. However, the mechanism by which Kir.4.1 mutations cause the tubulopathy is not completely understood. Here we demonstrate that Kcnj10 is a main contributor to the basolateral K conductance in the early distal convoluted tubule (DCT1) and determines the expression of the apical Na-Cl cotransporter (NCC) in the DCT. Immunostaining demonstrated Kcnj10 and Kcnj16 were expressed in the basolateral membrane of DCT, and patch-clamp studies detected a 40-pS K channel in the basolateral membrane of the DCT1 of p8/p10 wild-type Kcnj10 +/+ mice (WT). This 40-pS K channel is absent in homozygous Kcnj10 −/− (knockout) mice. The disruption of Kcnj10 almost completely eliminated the basolateral K conductance and decreased the negativity of the cell membrane potential in DCT1. Moreover, the lack of Kcnj10 decreased the basolateral Cl conductance, inhibited the expression of Ste20-related proline-alanine-rich kinase and diminished the apical NCC expression in DCT. We conclude that Kcnj10 plays a dominant role in determining the basolateral K conductance and membrane potential of DCT1 and that the basolateral K channel activity in the DCT determines the apical NCC expression possibly through a Ste20-related proline-alanine-rich kinasedependent mechanism. SeSAME/EAST syndrome | Kir.5.1 | SPAK | WNK T he distal convoluted tubule (DCT) of the kidney is responsible for the absorption of 5% of the filtered NaCl load and plays an important role in the reabsorption of Ca 2+ and Mg 2+

Caveolin-1 Deficiency Inhibits the Basolateral K+ Channels in the Distal Convoluted Tubule and Impairs Renal K+ and Mg2+ Transport

“…Moreover, immunostaining image demonstrates that cav-1 is highly expressed in the basolateral (Figure 1, F-H), which is identified by positive immunostaining of parvalbumin, a Ca 2+ -binding protein exclusively expressed in the DCT. 21 Because previous study showed that Kir4.1 was expressed in the basolateral membrane of DCT, 13 it is reasonable to assume that Kir4.1 and cav-1 are colocalized in the basolateral membrane of DCT cells. Our previous study demonstrated that c-Src phosphorylated Kcnj10 and that the inhibition of src-family protein tyrosine kinase (SFK), a family of c-Src-like tyrosine kinase, 22 decreased the basolateral 40 pS K + channel activity in DCT1.…”

“…As discussed previously, the DCT1 cells have no apical K + channel, and they have a lack of coupling with neighboring cells. 9,13 Therefore, the whole-cell K currents were equal to the basolateral K + conductance. Figure 6A is a set of whole-cell recording showing that K + currents of DCT1 in cav-1 KO mice (513672 pA) were significantly lower than those in WT mice (1,3006205 pA) (n=8).…”

“…[14][15][16] Experiments performed in Kcnj10 knockout (KO) mice showed that the disruption of Kcnj10 decreased the expression of NCC and SPAK. 13 This strongly suggests the critical role of basolateral K channels in the regulation of transepithelial membrane transport in the DCT. However, because homozygous Kcnj10 2 /2 mice could not survive .2 weeks after the birth, 17 this made it impossible to further characterize the membrane transport in those mice.…”

“…[10][11][12] The role of Kir4.1 in forming the basolateral 40 pS K + channel of the DCT was convincingly demonstrated by the observation that the disruption of Kcnj10 (Kir.4.1) completely eliminated the 40 pS K + channel. 13 Moreover, the basolateral K + conductance was largely abolished in the early DCT (DCT1) of Kcnj10 2/2 mice, suggesting that Kcnj10 (Kir.4.1) is a major contributor to the basolateral K + conductance in the DCT1. Loss-of-function mutations of Kcnj10 cause SeSAME/ EAST syndrome, and the renal phenotype of the disease is characterized by salt wasting, hypomagnesemia, metabolic alkalosis, and hypokalemia.…”

Réabsorption du sel et sécrétion du potassium par le néphron distal

“…Cette hypothèse a été vérifiée chez la souris Kir4.1 -/-. Ces animaux présentent en effet une diminution de l'expression de SPAK et de NCC [30]. Ces résultats permettent d'expliquer comment des mutations inactivatrices du gène codant Kir4.1 peuvent être à l'origine du syndrome EAST (epilepsy, ataxia, sensorineural deafness, and tubulopathy)/SeSAME (seizures, sensorineural deafness, ataxia, mental retardation, and electrolyte imbalance), un syndrome qui touche de nombreux organes et dont les manifestations rénales sont semblables à celles observées chez les patients atteints du syndrome de Gitelman causé, lui, par des mutations inactivatrices de NCC [31,32].…”