Acute insulin stimulation induces phosphorylation of the Na-Cl cotransporter in cultured distal mpkDCT cells and mouse kidney

• Published in: PloS one 2011-08, Vol.6 (8), p.e24277-e24277
• Main Authors: Sohara, Eisei, Rai, Tatemitsu, Yang, Sung-Sen, Ohta, Akihito, Naito, Shotaro, Chiga, Motoko, Nomura, Naohiro, Lin, Shih-Hua, Vandewalle, Alain, Ohta, Eriko, Sasaki, Sei, Uchida, Shinichi
• Format: Article
• Language: English
• Subjects: 1-Phosphatidylinositol 3-kinase; Alanine; Animal experimentation; Animals; Biology; Cells, Cultured; Distal tubules; Gene Knockdown Techniques; Insulin; Insulin - administration & dosage; Insulin - pharmacology; Insulin resistance; Kidney Tubules, Distal - cytology; Kidney Tubules, Distal - enzymology; Kidney Tubules, Distal - metabolism; Kidneys; Kinases; Localization; Medicine; Mice; Oxidative stress; Phosphatidylinositol 3-Kinases - metabolism; Phosphorylation; Phosphorylation - drug effects; Potassium; Proline; Protein-Serine-Threonine Kinases - metabolism; Reabsorption; Rodents; Sodium; Sodium chloride; Sodium Chloride Symporters - metabolism; Sodium Chloride, Dietary - pharmacology; Time Factors; Tubules
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0024277

The NaCl cotransporter (NCC) is essential for sodium reabsorption at the distal convoluted tubules (DCT), and its phosphorylation increases its transport activity and apical membrane localization. Although insulin has been reported to increase sodium reabsorption in the kidney, the linkage between insulin and NCC phosphorylation has not yet been investigated. This study examined whether insulin regulates NCC phosphorylation. In cultured mpkDCT cells, insulin increased phosphorylation of STE20/SPS1-related proline-alanine-rich kinase (SPAK) and NCC in a dose-dependent manner. This insulin-induced phosphorylation of NCC was suppressed in WNK4 and SPAK knockdown cells. In addition, Ly294002, a PI3K inhibitor, decreased the insulin effect on SPAK and NCC phosphorylation, indicating that insulin induces phosphorylation of SPAK and NCC through PI3K and WNK4 in mpkDCT cells. Moreover, acute insulin administration to mice increased phosphorylation of oxidative stress-responsive kinase-1 (OSR1), SPAK and NCC in the kidney. Time-course experiments in mpkDCT cells and mice suggested that SPAK is upstream of NCC in this insulin-induced NCC phosphorylation mechanism, which was confirmed by the lack of insulin-induced NCC phosphorylation in SPAK knockout mice. Moreover, insulin administration to WNK4 hypomorphic mice did not increase phosphorylation of OSR1, SPAK and NCC in the kidney, suggesting that WNK4 is also involved in the insulin-induced OSR1, SPAK and NCC phosphorylation mechanism in vivo. The present results demonstrated that insulin is a potent regulator of NCC phosphorylation in the kidney, and that WNK4 and SPAK are involved in this mechanism of NCC phosphorylation by insulin.