Characterization of Wild-Type and ΔF508 Cystic Fibrosis Transmembrane Regulator in Human Respiratory Epithelia

Abstract

Previous studies in native tissues have produced conflicting data on the localization and metabolic fate of WT and ⌬F508 cystic fibrosis transmembrane regulator (CFTR) in the lung. Combining immunocytochemical and biochemical studies utilizing new high-affinity CFTR mAbs with ion transport assays, we examined both 1) the cell type and region specific expression of CFTR in normal airways and 2) the metabolic fate of ⌬F508 CFTR and associated ERM proteins in the cystic fibrosis lung. Studies of lungs from a large number of normal subjects revealed that WT CFTR protein localized to the apical membrane of ciliated cells within the superficial epithelium and gland ducts. In contrast, other cell types in the superficial, gland acinar, and alveolar epithelia expressed little WT CFTR protein. No ⌬F508 CFTR mature protein or function could be detected in airway specimens freshly excised from a large number of ⌬F508 homozygous subjects, despite an intact ERM complex. In sum, our data demonstrate that WT CFTR is predominantly expressed in ciliated cells, and ⌬F508 CFTR pathogenesis in native tissues, like heterologous cells, reflects loss of normal protein processing.

Ezrin-Radixin-Moesin-Binding Phosphoprotein (EBP50), an Estrogen-Inducible Scaffold Protein, Contributes to Biliary Epithelial Cell Proliferation

“…Whether EBP50 undergoes cytoplasmic delocalization in homozygous ⌬F508 CFTR bronchial epithelial cells is a matter of debate. 39, 40 Here we show that ⌬F508 CFTR mutation is neither sufficient nor necessary for EBP50 to undergo delocalization in cholangiocytes. Accordingly, delocalization of EBP50 was absent in the native bile ducts from ⌬F508 CF patients and present in the ductular cells from non CF patients.…”

Pseudomonas aeruginosa triggers CFTR-mediated airway surface liquid secretion in swine trachea

“…29), triggering the release of proinflammatory cytokines into the submucosa within several minutes (30). The cytokines diffuse from the surface epithelium to the glands located ∼150 μm away (31,32), stimulating CFTR-dependent ASL secretion (13). Flagellin also will induce mucin expression within 18-24 h and further contribute to bacteria clearance (33,34).…”

Expression of CFTR from a ciliated cell-specific promoter is ineffective at correcting nasal potential difference in CF mice

“…In human nasal and lower airways, it has been reported by several investigators that CFTR is present predominantly at the apical surface of ciliated cells. [5][6][7] In a recent report, targeting expression of CFTR to ciliated cells using a parainfluenza virus was demonstrated to correct several features of the CF phenotype in vitro. 27 Thus a ciliated cell-specific promoter may be useful to both drive expression of CFTR in the correct cell type and also to limit expression in non-target tissue.…”

“…In the human airway, CFTR has been reported to be expressed in ciliated cells and in serous cells of the submucosal glands. [5][6][7][8] However, the exact cellular distribution of CFTR and the importance of different cell types to disease pathogenesis remain unclear. To express CFTR in the correct cells at the correct level, the use of the endogenous cellular promoter to drive expression of the transgene would be ideal.…”