The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) is a multifunctional protein that both transports Cl- across the apical plasma membrane of epithelial cells and regulates ion transport by other proteins, such as the Epithelial Sodium Channel, ENaC. A cardinal feature of Cystic Fibrosis (CF) is hyperactivity of Na+ transport via ENaC in the airway epithelia, although the mechanism by which this results from the absence of CFTR is not known. Efforts at pharmacologic repair of mutant CFTR function, such as the use of Sodium 4- Phenylbutyrate (4PBA) to correct trafficking of the most common mutant CFTR, ?F508-CFTR, have concentrated on assessing restoration of a mutant CFTR's Cl- transport function. These studies have often ignored the influence of 4PBA or other CFTR "correctors" on ENaC trafficking and/or function. Our proposed studies will address whether pharmacologic repair, or correction of ?F508-CFTR trafficking will promote appropriate regulation of ENaC in the CF airway. This is a key issue in the implementation of pharmacologic strategies to improve ?F508 CFTR trafficking and function. Our hypothesis is that 4PBA induces modulations of molecular chaperone expression in epithelial cells that result in altered intracellular trafficking and functional expression of CFTR and ENaC. Because 4PBA also improves the intracellular trafficking of a number of mutant proteins in diseases besides CF, this hypothesis may also be germane to developing pharmacologic therapies for a number of other protein conformational diseases. 4PBA causes altered expression of the cytosolic chaperones Hsc70 and Hsp70, as well as a novel luminal endoplasmic reticular protein of 29 kDa, ERp29. Our data suggest that specifically altered expression of these chaperones modulates CFTR, ?F508 and ENaC trafficking and functional expression. The present proposal will build on these preliminary data and test this hypothesis with studies directed at the following Specific Aims:
Specific Aim 1 : To determine the mechanism by which Hsc70 and Hsp70 modulate CFTR, ?F508 and ENaC trafficking in epithelial cells.
Specific Aim 2 : To determine the mechanism by which ERp29, a novel 4-phenylbutyrate-regulated luminal endoplasmic reticular protein, regulates the trafficking of CFTR, ?F508 and ENaC in epithelial cells.

Public Health Relevance

The major mechanim by which the lung and airway defends itself from the environment depends on proper ion transport in the respiratory epithelia. Such ion transport is aberrant in Cystic Fibrosis, leading to significant morbidity and mortality. These data will promote better understanding of the regulation of channels responsible for ion transport in Cystic Fibrosis and other diseases of the airway, and inform development of novel, mechanism-based therapies for Cystic Fibrosis.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK058046-11
Application #
8241006
Study Section
Cellular and Molecular Biology of the Kidney Study Section (CMBK)
Program Officer
Mckeon, Catherine T
Project Start
2000-09-01
Project End
2014-03-31
Budget Start
2012-04-01
Budget End
2014-03-31
Support Year
11
Fiscal Year
2012
Total Cost
$354,210
Indirect Cost
$138,885
Name
Children's Hospital of Philadelphia
Department
Type
DUNS #
073757627
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Grumbach, Yael; Bikard, Yann; Suaud, Laurence et al. (2014) ERp29 regulates epithelial sodium channel functional expression by promoting channel cleavage. Am J Physiol Cell Physiol 307:C701-9
Chanoux, Rebecca A; Shubin, Calla B; Robay, Amal et al. (2013) Hsc70 negatively regulates epithelial sodium channel trafficking at multiple sites in epithelial cells. Am J Physiol Cell Physiol 305:C776-87
Chanoux, Rebecca A; Robay, Amal; Shubin, Calla B et al. (2012) Hsp70 promotes epithelial sodium channel functional expression by increasing its association with coat complex II and its exit from endoplasmic reticulum. J Biol Chem 287:19255-65
Suaud, Laurence; Miller, Katelyn; Alvey, Lora et al. (2011) ERp29 regulates DeltaF508 and wild-type cystic fibrosis transmembrane conductance regulator (CFTR) trafficking to the plasma membrane in cystic fibrosis (CF) and non-CF epithelial cells. J Biol Chem 286:21239-53
Suaud, Laurence; Miller, Katelyn; Panichelli, Ashley E et al. (2011) 4-Phenylbutyrate stimulates Hsp70 expression through the Elp2 component of elongator and STAT-3 in cystic fibrosis epithelial cells. J Biol Chem 286:45083-92
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Das, Shamie; Smith, Tekla D; Sarma, Jayasri Das et al. (2009) ERp29 restricts Connexin43 oligomerization in the endoplasmic reticulum. Mol Biol Cell 20:2593-604
Yan, Wusheng; Spruce, Lynn; Rosenblatt, Michael M et al. (2007) Intracellular trafficking of a polymorphism in the COOH terminus of the alpha-subunit of the human epithelial sodium channel is modulated by casein kinase 1. Am J Physiol Renal Physiol 293:F868-76
Suaud, Laurence; Yan, Wusheng; Carattino, Marcelo D et al. (2007) Regulatory interactions of N1303K-CFTR and ENaC in Xenopus oocytes: evidence that chloride transport is not necessary for inhibition of ENaC. Am J Physiol Cell Physiol 292:C1553-61
Suaud, Laurence; Yan, Wusheng; Rubenstein, Ronald C (2007) Abnormal regulatory interactions of I148T-CFTR and the epithelial Na+ channel in Xenopus oocytes. Am J Physiol Cell Physiol 292:C603-11

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