Epithelial Na+ channel (ENaCs) are expressed in the aldosterone-sensitive distal nephron where they serve as the final site of renal Na+ reabsorption and have a key role in the regulation of extracellular fluid volume and blood pressure. ENaCs are also expressed throughout the airway and in alveoli, where they mediate Na+ reabsorption and have a critical role in regulating the volume of airway and alveolar fluids. Channel assembly appears to be an inefficient process, and quality control mechanisms within the ER have an important role in preventing exit of misfolded channel subunits from the ER while promoting the exit of properly assembled oligomeric channels for delivery to the cell surface. Channel subunits also undergo post- translational processing that includes cleavage by proteases. Proposed studies in Aim 1 will define quality control mechanisms within the ER that targets ENaC subunits for degradation. Proposed studies in Aim 2 will define the processing of ENaC subunits and regulation of channel activity by proteases. Proposed studies in Aim 3 will define the role of palmitoylation in the regulation of ENaC. These studies should generate new information regarding ENaC biogenesis and post-translational processing that provide additional levels of control of the cellular and surface pool of Na+ channels and of channel gating.
Epithelial Na+ channels have key roles in the regulation of extracellular fluid volume, blood pressure and the volume of airway and alveolar fluids. Our proposed studies will address cellular mechanisms that are involved in the biogenesis and post-translational processing of Na+ channels. Enhanced ENaC proteolysis contributes to the increase in channel activity observed in Liddle's syndrome and in cystic fibrosis, and may contribute to the increase in Na+ retention that occurs in nephrotic syndrome. At a basic level, our studies are relevant to understanding the process of ER associated degradation (ERAD). Our proposed studies are particularly relevant to oligomeric integral membrane proteins, as their cellular requirements for ERAD may evolve upon the acquisition of their quaternary structure.
|Buck, Teresa M; Jordan, Rick; Lyons-Weiler, James et al. (2015) Expression of three topologically distinct membrane proteins elicits unique stress response pathways in the yeast Saccharomyces cerevisiae. Physiol Genomics 47:198-214|
|Ray, Evan C; Kleyman, Thomas R (2015) Cutting it out: ENaC processing in the human nephron. J Am Soc Nephrol 26:1-3|
|Chen, Jingxin; Kleyman, Thomas R; Sheng, Shaohu (2014) Deletion of Î±-subunit exon 11 of the epithelial Na+ channel reveals a regulatory module. Am J Physiol Renal Physiol 306:F561-7|
|Kleyman, Thomas R; Myerburg, Michael M (2014) Proteases, ENaCs and cystic fibrosis. J Physiol 592:5145|
|Carattino, Marcelo D; Mueller, Gunhild M; Palmer, Lawrence G et al. (2014) Prostasin interacts with the epithelial Na+ channel and facilitates cleavage of the Î³-subunit by a second protease. Am J Physiol Renal Physiol 307:F1080-7|
|Kolb, Alexander R; Needham, Patrick G; Rothenberg, Cari et al. (2014) ESCRT regulates surface expression of the Kir2.1 potassium channel. Mol Biol Cell 25:276-89|
|Mukherjee, Anindit; Mueller, Gunhild M; Kinlough, Carol L et al. (2014) Cysteine palmitoylation of the Î³ subunit has a dominant role in modulating activity of the epithelial sodium channel. J Biol Chem 289:14351-9|
|Shi, Shujie; Carattino, Marcelo D; Hughey, Rebecca P et al. (2013) ENaC regulation by proteases and shear stress. Curr Mol Pharmacol 6:28-34|
|Kleyman, Thomas R; Satlin, Lisa M; Hallows, Kenneth R (2013) Opening lines of communication in the distal nephron. J Clin Invest 123:4139-41|
|Chen, Jingxin; Kleyman, Thomas R; Sheng, Shaohu (2013) Gain-of-function variant of the human epithelial sodium channel. Am J Physiol Renal Physiol 304:F207-13|
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