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.
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.
|Shobair, Mahmoud; Dagliyan, Onur; Kota, Pradeep et al. (2016) Gain-of-Function Mutation W493R in the Epithelial Sodium Channel Allosterically Reconfigures Intersubunit Coupling. J Biol Chem 291:3682-92|
|Yu, Dongfang; Davis, Richard M; Aita, Megumi et al. (2016) Characterization of Rat Meibomian Gland Ion and Fluid Transport. Invest Ophthalmol Vis Sci 57:2328-43|
|Dickey, Audrey S; Pineda, Victor V; Tsunemi, Taiji et al. (2016) PPAR-Î´ is repressed in Huntington's disease, is required for normal neuronal function and can be targeted therapeutically. Nat Med 22:37-45|
|Sesma, Juliana I; Weitzer, Clarissa D; Livraghi-Butrico, Alessandra et al. (2016) UDP-glucose promotes neutrophil recruitment in the lung. Purinergic Signal 12:627-635|
|Livraghi-Butrico, A; Grubb, B R; Wilkinson, K J et al. (2016) Contribution of mucus concentration and secreted mucins Muc5ac and Muc5b to the pathogenesis of muco-obstructive lung disease. Mucosal Immunol :|
|Esther Jr, Charles R; Coakley, Raymond D; Henderson, Ashley G et al. (2015) Metabolomic Evaluation of Neutrophilic Airway Inflammation in Cystic Fibrosis. Chest 148:507-15|
|Lazarowski, Eduardo R; Harden, T Kendall (2015) UDP-Sugars as Extracellular Signaling Molecules: Cellular and Physiologic Consequences of P2Y14 Receptor Activation. Mol Pharmacol 88:151-60|
|Billet, Arnaud; Jia, Yanlin; Jensen, Tim et al. (2015) Regulation of the cystic fibrosis transmembrane conductance regulator anion channel by tyrosine phosphorylation. FASEB J 29:3945-53|
|Hildebrandt, Ellen; Ding, Haitao; Mulky, Alok et al. (2015) A stable human-cell system overexpressing cystic fibrosis transmembrane conductance regulator recombinant protein at the cell surface. Mol Biotechnol 57:391-405|
|Aleksandrov, Luba A; Jensen, Timothy J; Cui, Liying et al. (2015) Thermal stability of purified and reconstituted CFTR in a locked open channel conformation. Protein Expr Purif 116:159-66|
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