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.

Public Health Relevance

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.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK065161-09
Application #
8517681
Study Section
Special Emphasis Panel (ZRG1-RUS-C (02))
Program Officer
Ketchum, Christian J
Project Start
2003-07-01
Project End
2014-06-30
Budget Start
2013-07-01
Budget End
2014-06-30
Support Year
9
Fiscal Year
2013
Total Cost
$306,566
Indirect Cost
$100,856
Name
University of Pittsburgh
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
004514360
City
Pittsburgh
State
PA
Country
United States
Zip Code
15213
Chen, Jingxin; Kleyman, Thomas R; Sheng, Shaohu (2014) Deletion of ?-subunit exon 11 of the epithelial Na+ channel reveals a regulatory module. Am J Physiol Renal Physiol 306:F561-7
Carattino, Marcelo D; Mueller, Gunhild M; Palmer, Lawrence G et al. (2014) Prostasin interacts with the epithelial Na+ channel and facilitates cleavage of the ?-subunit by a second protease. Am J Physiol Renal Physiol 307:F1080-7
Mukherjee, Anindit; Mueller, Gunhild M; Kinlough, Carol L et al. (2014) Cysteine palmitoylation of the ? subunit has a dominant role in modulating activity of the epithelial sodium channel. J Biol Chem 289:14351-9
Buck, Teresa M; Plavchak, Lindsay; Roy, Ankita et al. (2013) The Lhs1/GRP170 chaperones facilitate the endoplasmic reticulum-associated degradation of the epithelial sodium channel. J Biol Chem 288:18366-80
Shi, Shujie; Carattino, Marcelo D; Hughey, Rebecca P et al. (2013) ENaC regulation by proteases and shear stress. Curr Mol Pharmacol 6:28-34
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
Passero, Christopher J; Mueller, Gunhild M; Myerburg, Michael M et al. (2012) TMPRSS4-dependent activation of the epithelial sodium channel requires cleavage of the ?-subunit distal to the furin cleavage site. Am J Physiol Renal Physiol 302:F1-8
Kashlan, Ossama B; Kleyman, Thomas R (2011) ENaC structure and function in the wake of a resolved structure of a family member. Am J Physiol Renal Physiol 301:F684-96
Passero, Christopher J; Carattino, Marcelo D; Kashlan, Ossama B et al. (2010) Defining an inhibitory domain in the gamma subunit of the epithelial sodium channel. Am J Physiol Renal Physiol 299:F854-61
Passero, Christopher J; Hughey, Rebecca P; Kleyman, Thomas R (2010) New role for plasmin in sodium homeostasis. Curr Opin Nephrol Hypertens 19:13-9

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