Characterization Of A Novel Splice Variant Of Î´ Enac Subunit In Human Lungs
Salt absorption via apical epithelial sodium channels (ENaC) is a critical rate-limiting process in maintaining airway and lung lining fluid at the physiological level. Î´ ENaC (termed Î´1 in this article) has been detected in human lung epithelial cells in addition to Î±, Î², and Î³ subunits (Ji HL, Su XF, Kedar S, Li J, Barbry P, Smith PR, Matalon S, Benos DJ. J Biol Chem 281: 8233-8241, 2006; Nie HG, Chen L, Han DY, Li J, Song WF, Wei SP, Fang XH, Gu X, Matalon S, Ji HL, J Physiol 587: 2663-2676, 2009) and may contribute to the differences in the biophysical properties of amiloride-inhibitable cation channels in pulmonary epithelial cells. Here we cloned a splicing variant of the Î´1 ENaC, namely, Î´2 ENaC in human bronchoalveolar epithelial cells (16HBEo). Î´2 ENaC possesses 66 extra amino acids attached to the distal amino terminal tail of the Î´1 ENaC. Î´2 ENaC was expressed in both alveolar type I and II cells of human lungs as revealed by in situ hybridization and real-time RT-PCR. To characterize the biophysical and pharmacological features of the splicing variant, we injected Xenopus oocytes with human ENaC cRNAs and measured whole cell and single channel currents of Î´1Î²Î³, Î´2Î²Î³, and Î±Î²Î³ channels. Oocytes injected with Î´2Î²Î³ cRNAs exhibited whole cell currents significantly greater than those expressing Î´1Î²Î³ and Î±Î²Î³ channels. Single channel activity, unitary conductance, and open probability of Î´2Î²Î³ channels were significantly greater compared with Î´1Î²Î³ and Î±Î²Î³ channels. In addition, Î´2Î²Î³ and Î´1Î²Î³ channels displayed significant differences in apparent Na + affinity, dissociation constant for amiloride (K iamil), the EC50 for capsazepine activation, and gating kinetics by protons. Channels comprising of this novel splice variant may contribute to the diversities of native epithelial Na + channels. Â© 2012 the American Physiological Society.
American Journal of Physiology - Lung Cellular and Molecular Physiology
Digital Object Identifier (DOI)
Zhao, Run Zhen; Nie, Hong Guang; Su, Xue Feng; Han, Dong Yun; Lee, Andrew; Huang, Yao; Chang, Yongchang; Matalon, Sadis; and Ji, Hong Long, "Characterization Of A Novel Splice Variant Of Î´ Enac Subunit In Human Lungs" (2012). Neurobiology. 44.