Characterization of the epithelial sodium channel delta-subunit in human nasal epithelium.
Article Details
- CitationCopy to clipboard
Bangel-Ruland N, Sobczak K, Christmann T, Kentrup D, Langhorst H, Kusche-Vihrog K, Weber WM
Characterization of the epithelial sodium channel delta-subunit in human nasal epithelium.
Am J Respir Cell Mol Biol. 2010 Apr;42(4):498-505. doi: 10.1165/rcmb.2009-0053OC. Epub 2009 Jun 11.
- PubMed ID
- 19520916 [ View in PubMed]
- Abstract
The epithelial sodium channel (ENaC) mediates the first step in Na+ reabsorption in epithelial cells such as kidney, colon, and airways and may consist of four homologous subunits (alpha, beta, gamma, delta). Predominantly, the alpha-subunit is expressed in these epithelia, and it usually forms functional channels with the beta- and gamma-subunits. The delta-subunit was first found in human brain and kidney, but the expression was also detected in human cell lines of lung, pancreatic, and colonic origin. When co-expressed with beta and gamma accessory subunits in heterologous systems, the two known isoforms of the delta-ENaC subunit (delta1 and delta2) can build amiloride-sensitive Na+ channels. In the present study we demonstrate the expression and function of the delta-subunit in human nasal epithelium (HNE). We cloned and sequenced the full-length cDNA of the delta-ENaC subunit and were able to show that in nasal tissue at least isoform 1 is expressed. Furthermore, we performed Western blot analyses and compared the cell surface expression of the delta-subunit with the classically expressed alpha-subunit by using immunofluorescence experiments. Thereby, we could show that the quantity of both subunits is almost similar. In addition, we show the functional expression of the delta-ENaC subunit with measurements in modified Ussing chambers, and demonstrate that in HNE a large portion of the Na+ transport is mediated by the delta-ENaC subunit. Therefore, we suppose that the delta-subunit may possess an important regulatory function and might interact with other ENaC subunits or members of the DEG/ENaC family in the human respiratory epithelium.