Nitric Oxide Modulation of CFTR Expression and Function

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DESCRIPTION (provided by applicant): The cystic fibrosis trans-membrane conductance regulator (CFTR), a 1480 amino acid protein, is a member of the traffic ATPase family (60) and functions as a cAMP-regulated CI channel. Based on our published results and preliminary data, we hypothesize that chronic exposure of mice and airway cells to agents which increase concentrations of reactive species (RONS), formed by the interaction of nitric oxide (NO) with partially reduced oxygen intermediates, results in oxidative modifications (oxidation, nitration and/or nitrosation) of key CFTR amino acids. These changes may: (1) decrease apical levels of CFTR by targeting it for ubiquitination and endoplasmic reticulum associated degradation by proteasomes and (2) impair Cl- secretion across the airway and alveolar epithelial cells following cAMP-stimulation by decreasing CFTR phosphorylation. These hypotheses will be tested both in vitro, by exposing Calu-3, primary human airway epithelial cells and mouse tracheocytes (MTE) to NO and RONS, as well as C57BL/6 mice to NO (1-10 ppm); nitrogen dioxide (NO2:1-10 ppm); intratracheal instillation of Mycoplasma pulmonis and measure the extent of oxidative modification and ubiquitination of CFTR as well as microscopic (single channel Cl currents) and macroscopic (whole cell Cl currents, nasal potential differences and alveolar fluid clearance) indices of its ability to act as a cAMP-activated Cl- channel. To identify specific amino acids modifications leading to loss of CFTR function, we will construct CFTR mutants by substituting each of the 40 CFTR tyrosines with alanine, express each cRNA in oocytes, and measure basal and cAMP-activated whole cell and single channel Cl- currents before and after exposure of oocyte to the RONS. Because of the well demonstrated vital importance of CFTR in both the hydration of airway fluid, as well as in cAMP-activated Na+ transport across the alveolar epithelium, the results of these studies may offer significant new insight into the pathophysiology of a number of pulmonary, non cystic fibrosis inflammatory diseases such as asthma, chronic obstructive lung disease and adult respiratory distress syndrome.