N-methyl-D-aspartate receptor subunit NR3a expression and function in principal cells of the collecting duct

作者：Sproul Adrian; Steele Stacy L; Thai Tiffany L; Yu ShanPing; Klein Janet D; Sands Jeff M; Bell P Darwin^*

来源：American Journal of Physiology - Renal Fluid and Electrolyte Physiology, 2011, 301(1): F44-F54.

DOI：10.1152/ajprenal.00666.2010

• cytosolic calcium
• aquaporin 2
• medullary tonicity

Sproul A, Steele SL, Thai TL, Yu S, Klein JD, Sands JM, Bell PD. N-methyl-D-aspartate receptor subunit NR3a expression and function in principal cells of the collecting duct. Am J Physiol Renal Physiol 301: F44-F54, 2011. First published March 23, 2011; doi: 10.1152/ajprenal.00666.2010.-N-methyl-D-aspartate receptors (NMDARs) are Ca(2+) -permeable, ligand-gated, nonselective cation channels that function as neuronal synaptic receptors but which are also expressed in multiple peripheral tissues. Here, we show for the first time that NMDAR subunits NR3a and NR3b are highly expressed in the neonatal kidney and that there is continued expression of NR3a in the renal medulla and papilla of the adult mouse. NR3a was also expressed in mIMCD-3 cells, where it was found that hypoxia and hypertonicity upregulated NR3a expression. Using short-hairpin (sh) RNA-based knockdown, a stable inner medullary collecting duct (IMCD) cell line was established that had similar to 80% decrease in NR3a. Knockdown cells exhibited an increased basal intracellular calcium concentration, reduced cell proliferation, and increased cell death. In addition, NR3a knockdown cells exhibited reduced water transport in response to the addition of vasopressin, suggesting an alteration in aquaporin-2 (AQP2) expression/function. Consistent with this notion, we demonstrate decreased surface expression of glycosylated AQP2 in IMCD cells transfected with NR3a shRNA. To determine whether this also occurred in vivo, we compared AQP2 levels in wild-type vs. in NR3a(-/-) mice. Total AQP2 protein levels in the outer and inner medulla were significantly reduced in knockout mice compared with control mice. Finally, NR3a(-/-) mice showed a significant delay in their ability to increase urine osmolality during water restriction. Thus NR3a may play a renoprotective role in collecting duct cells. Therefore, under conditions that are associated with high vasopressin levels, NR3a, by maintaining low intracellular calcium levels, protects the function of the principal cells to reabsorb water and thereby increase medullary osmolality.

• 出版日期2011-7