Deletion of NEDD4‐2 Abolishes the Inhibitory Effect of High Sodium (HS) Intake on the Basolateral Kir4.1/Kir5.1 of the DCT and Thiazide‐Sensitive Na‐Cl Cotransport (NCC)

Abstract

BackgroundWe have previously demonstrated that the deletion of NEDD4‐2 increased the basolateral Kir4.1/Kir5.1 channel activity in the distal convoluted tubule (DCT), suggesting the role of NEDD4‐2 in the regulation of basolateral Kir4.1/Kir5.1. Also, it has been demonstrated that dietary sodium intake regulated the basolateral Kir4.1/Kir5.1 channel activity in the DCT such that low sodium (LS) intake stimulated whereas HS intake inhibited the Kir4.1/Kir5.1 channels in the DCT. The HS‐induced inhibition of basolateral Kir4.1/Kir5.1 channels in the DCT was essential for the HS‐induced inhibition of NCC expression/activity because HS failed to inhibit NCC in the kidney‐specific Kir4.1 knockout mice. The aims of the present study are: 1) To explore whether the effect of HS on the basolateral Kir4.1/Kir5.1 in the DCT is compromised in the absence of Nedd4‐2; 2) To examine whether the deletion of Nedd4‐2 abolishes the effect of HS on NCC activity.MethodsWe have used the patch‐clamp methods to measure the basolateral K (Kir4.1/Kir5.1) channel activity of the DCT and DCT membrane potential, and employed renal clearance method to measure thiazide‐sensitive renal sodium excretion in Nedd4l+/+ (WT) mice and renal tubule‐specific Nedd4l−/− mice (Ks‐NEDD4‐2 KO).ResultsWe confirmed the previous finding that HS inhibited the basolateral Kir4.1/Kir5.1 channel activity in the DCT and depolarized the DCT membrane and that LS intake increased the basolateral K conductance and hyperpolarized DCT membrane. The deletion of NEDD4‐2 increased the basolateral Kir4.1/Kir5.1 channel activity in the DCT and hyperpolarized DCT membrane. Moreover, the effect of either HS or LS on the basolateral Kir4.1/Kir5.1 channel activity was absent in Ks‐NEDD4‐2 KO mice. Renal clearance experiments showed that LS increased while HS decreased thiazide‐sensitive urinary sodium excretion, indicating the stimulation of NCC and the inhibition of NCC, respectively. The deletion of Nedd4‐2 not only augmented the thiazide‐induced natriuresis but also abolished the inhibitory effect of HS on the thiazide‐induced natriuresis. Furthermore, LS intake failed to further increase thiazide‐sensitive renal sodium excretion. Thus, the effect of HS and LS intake on NCC activity was abolished in Ks‐NEDD4‐2 KO mice.ConclusionNEDD4‐2 plays an important role in mediating the inhibitory effect of HS on the basolateral Kir4.1/Kir5.1 channel activity and NCC activity/expression.Support or Funding InformationDK115366