The sodium chloride cotransporter (NCC) and epithelial sodium channel (ENaC) associate

Abstract

The thiazide-sensitive sodium chloride cotransporter (NCC) and the Epithelial Sodium Channel (ENaC) are two of the most important determinants of salt balance and thus systemic blood pressure. Abnormalities in either result in profound changes in blood pressure. There is one segment of the nephron where these two sodium transporters are co-expressed, the second part of the Distal Convoluted Tubule. This is a key part of the aldosterone-sensitive distal nephron, the final regulator of salt handling in the kidney. Aldosterone is the key hormonal regulator for both of these proteins. Despite these shared regulators and co-expression in a key nephron segment, associations between these proteins have not been investigated. After confirming apical localization of these proteins, we demonstrated the presence of functional transport proteins and native association by Blue Native PAGE. Extensive co-immunoprecipitation experiments demonstrated a consistent interaction of NCC with alpha and gamma ENaC. Mammalian two-hybrid studies demonstrated direct binding of NCC to ENaC subunits. Fluorescence Resonance Energy Transfer and immunogold EM studies confirmed that these transport proteins are within appropriate proximity for direct binding. Additionally, we demonstrate that there are functional consequences of this interaction, with inhibition of NCC affecting ENaC function. This novel finding of an association between ENaC and NCC could alter our understanding of salt transport in the distal tubule.

Dominant functional role of the novel phosphorylation site S811 in the human renal NaCl cotransporter

“…Of interest, it has recently been demonstrated that NCC can interact with the epithelial Na + channel (ENaC) (69). Moreover, inhibition of NCC also affected the function of ENaC, likely via the direct interaction of both proteins (70). As NCC and ENaC are coexpressed along the later part of the DCT, it has been suggested that this interaction can regulate Na + reabsorption in the DCT (70,71).…”

KCNQ‐SMIT complex formation facilitates ion channel‐solute transporter cross talk

“…The Orai1 Ca 2+ channel, better known for interacting with stromal interaction molecule 1 (21), can also form complexes with secretory pathway Ca 2+ ‐ATPase isoform 2 (SPCA2), a P‐type calcium ion transporter found in the Golgi (22). The epithelial sodium channel, ENaC, was recently discovered to interact with the sodium chloride cotransporter NCC in vitro and in the distal convoluted tubule of the kidney (23). CFTR chloride channels, which also display some properties of ATP‐binding cassette transporters, can coassemble with chloride/bicarbonate exchangers from the SLC26A solute transporter family (24, 25).…”

Circadian regulation of renal function

“…While the NCC also reabsorbs sodium in the DCT2 segment, the amiloride-sensitive epithelial sodium channel (ENaC) reabsorbs Na + in the DCT2, the connecting tubule (CNT) and collecting duct [48–50]. In the DCT2, NCC co-localizes with ENaC [51–53], and this association can be further enhanced through the actions of aldosterone [54]. …”