Project II is designed to discover the molecular basis of CFTR-mediated restraint of ENaC activity in human airway epithelia. CFTR-mediated chloride secretion and ENaC-mediated sodium absorption have been considered central to control of airway surface liquid hydration, but the concept of reciprocal control of these opposing ion transport pathways is controversial. In some tissues where CFTR and ENaC are each expressed, their stimulation is coordinated to achieve Na and Cl absorption. Indeed, that is the case in alveolar type 2 cells (AT2C), which are to be characterized in Project III of this PPG. However, in airway epithelia, abundant evidence suggests that CFTR restrains ENaC function. We recently reported that CFTR and ENaC coimmunoprecipitate in normal airway epithelia, and ENaC in CF bronchial epithelium undergoes more extensive cleavage than ENaC in normal. Because ENaC mediated Na+ absorption is activated by cleavage of ENaC extracellular domains, this finding is congruent with the notion that CFTR restrains ENaC cleavage in normal bronchial epithelia. Project II proposes to identify the molecular basis of CFTR-ENaC associations in airway epithelia, which will be accomplished by biochemical assays, comparisons of CFTR and ENaC associated proteins in bronchial airway cells and AT2C, and molecular modeling of detected interactions (Aim 1). With this information. Project II will test two mechanistic hypotheses that describe inhibition of ENaC cleavage.
In Aim 2, we hypothesize that physical interaction of the R-domain of CFTR with the cytosolic N-termini of ENaC inhibits ENaC proteolysis and activation. This hypothesis is based on the novel observation that ENaC proteolysis is stimulated by phosphoinositde-binding of its cytosolic N terminal tails.
In Aim 3, Project II will test the requirement for CFTR function in the regulation of ENaC cleavage, and will further test specifically how CFTR's control of ASL pH mediates CFTR-specific effects on ENaC proteolysis. Information from these aims will further our understanding of CFTR regulation of ENaC function, specifically addressing the questions of why this regulation is cell specific, and yet when present, how it may be mediated by multiple mechanisms.

Public Health Relevance

Airway surfaces are protected by a hydrated layer of salt, water and mucins. Project II addresses control of surface liquid hydration by the ion channels CFTR and ENaC. In cytic fibrosis airway disease, CFTR is absent, ENaC is unregulated and airway surface hydration is lost. Airway obstruction follows, and this process may occur in other respiratory diseases, such as smoking induced COPD. Our results will expand understanding of and potential treatments for human lung disease.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Program Projects (P01)
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Heart, Lung, and Blood Initial Review Group (HLBP)
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University of North Carolina Chapel Hill
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He, Lihua; Aleksandrov, Andrei A; An, Jianli et al. (2015) Restoration of NBD1 thermal stability is necessary and sufficient to correct ?F508 CFTR folding and assembly. J Mol Biol 427:106-20
Roy, Michelle G; Livraghi-Butrico, Alessandra; Fletcher, Ashley A et al. (2014) Muc5b is required for airway defence. Nature 505:412-6
Henderson, Ashley G; Ehre, Camille; Button, Brian et al. (2014) Cystic fibrosis airway secretions exhibit mucin hyperconcentration and increased osmotic pressure. J Clin Invest 124:3047-60
Esther Jr, Charles R; Boucher, Richard C; Johnson, M Ross et al. (2014) Airway drug pharmacokinetics via analysis of exhaled breath condensate. Pulm Pharmacol Ther 27:76-82
Donnelley, Martin; Morgan, Kaye S; Siu, Karen K W et al. (2014) Non-invasive airway health assessment: synchrotron imaging reveals effects of rehydrating treatments on mucociliary transit in-vivo. Sci Rep 4:3689
Cholon, Deborah M; Quinney, Nancy L; Fulcher, M Leslie et al. (2014) Potentiator ivacaftor abrogates pharmacological correction of ?F508 CFTR in cystic fibrosis. Sci Transl Med 6:246ra96
Bove, Peter F; Dang, Hong; Cheluvaraju, Chaitra et al. (2014) Breaking the in vitro alveolar type II cell proliferation barrier while retaining ion transport properties. Am J Respir Cell Mol Biol 50:767-76
Guo, Xueliang; Zheng, Shuo; Dang, Hong et al. (2014) Genome reference and sequence variation in the large repetitive central exon of human MUC5AC. Am J Respir Cell Mol Biol 50:223-32
Yang, Zhengrong; Wang, Chi; Zhou, Qingxian et al. (2014) Membrane protein stability can be compromised by detergent interactions with the extramembranous soluble domains. Protein Sci 23:769-89
Hill, David B; Vasquez, Paula A; Mellnik, John et al. (2014) A biophysical basis for mucus solids concentration as a candidate biomarker for airways disease. PLoS One 9:e87681

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