The epithelial Na channel (ENaC) forms a pathway for Na absorption in the kidney, lung, and other epithelia. In order to maintain Na homeostasis and control blood pressure, ENaC is tightly regulated to respond to conditions of Na/volume depletion and Na/volume excess. However, defects in this regulation are responsible for nearly all of the known inherited forms of hypertension, and contributes to the pathogenesis of cystic fibrosis. The overall hypothesis of the proposed research is that mechanisms that control ENaC trafficking are critical for the regulation of epithelial Na transport. We propose three Specific Aims to test this hypothesis. 1. Our previous work indicates that Nedd4-2 is critical in the regulation of ENaC surface expression;defects in this regulation cause Liddle's syndrome, an inherited form of hypertension. In this aim, we will use novel approaches to investigate the mechanisms by which Nedd4-2 regulates ENaC surface expression. 2. Recent work indicates that ENaC is activated by proteolytic cleavage of the channel. Surprisingly, we found that Liddle's syndrome mutations selectively increase surface expression of cleaved ENaC channels. This provides a novel mechanism by which Liddle's syndrome mutations might alter ENaC gating. In this aim, we will pursue the underlying molecular mechanisms. 3. The assembly of ENaC subunits into a complex is a critical step in efficient trafficking to the cell surface. Based on preliminary data, we will investigate the mechanisms by which CHIP, a co-chaperone E3 ubiquitin ligase, regulates ENaC trafficking in the biosynthetic pathway. By using powerful new approaches and by testing novel hypotheses, this work will help to explain previous data and will generate new insight into mechanisms that regulate ENaC surface expression, and hence, epithelial Na transport and Na homeostasis. This has important implications for our understanding and treatment of diseases including hypertension and cystic fibrosis.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL058812-13
Application #
7813803
Study Section
Cellular and Molecular Biology of the Kidney Study Section (CMBK)
Program Officer
Thrasher, Terry N
Project Start
1997-09-01
Project End
2012-03-31
Budget Start
2010-04-01
Budget End
2011-03-31
Support Year
13
Fiscal Year
2010
Total Cost
$331,875
Indirect Cost
Name
University of Iowa
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
062761671
City
Iowa City
State
IA
Country
United States
Zip Code
52242
Butler, Phillip L; Staruschenko, Alexander; Snyder, Peter M (2015) Acetylation stimulates the epithelial sodium channel by reducing its ubiquitination and degradation. J Biol Chem 290:12497-503
Sierra, Ana; Zhu, Zhiyong; Sapay, Nicolas et al. (2013) Regulation of cardiac ATP-sensitive potassium channel surface expression by calcium/calmodulin-dependent protein kinase II. J Biol Chem 288:1568-81
Zhou, Ruifeng; Tomkovicz, Vivian R; Butler, Phillip L et al. (2013) Ubiquitin-specific peptidase 8 (USP8) regulates endosomal trafficking of the epithelial Na+ channel. J Biol Chem 288:5389-97
Sharotri, Vikas; Collier, Daniel M; Olson, Diane R et al. (2012) Regulation of epithelial sodium channel trafficking by proprotein convertase subtilisin/kexin type 9 (PCSK9). J Biol Chem 287:19266-74
Snyder, Peter M (2012) Intoxicated Na(+) channels. Focus on ""ethanol stimulates epithelial sodium channels by elevating reactive oxygen species"". Am J Physiol Cell Physiol 303:C1125-6
Wiemuth, Dominik; Lott, J Shaun; Ly, Kevin et al. (2010) Interaction of serum- and glucocorticoid regulated kinase 1 (SGK1) with the WW-domains of Nedd4-2 is required for epithelial sodium channel regulation. PLoS One 5:e12163
Zhou, Ruifeng; Kabra, Rajesh; Olson, Diane R et al. (2010) Hrs controls sorting of the epithelial Na+ channel between endosomal degradation and recycling pathways. J Biol Chem 285:30523-30
Collier, Daniel M; Snyder, Peter M (2009) Extracellular chloride regulates the epithelial sodium channel. J Biol Chem 284:29320-5