A Novel Natural Product Compound Enhances cAMP-Regulated Chloride Conductance of Cells Expressing CFTRΔF508

Abstract

Background: Cystic fibrosis (CF) results from mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which encodes a chloride channel localized at the plasma membrane of diverse epithelia. The most common mutation leading to CF, ⌬F508, occurs in the first nucleotide-binding domain (NBD1) of CFTR. The ⌬F508 mutation disrupts protein processing, leading to a decreased level of mutant channels at the plasma membrane and reduced transepithelial chloride permeability. Partial correction of the ⌬F508 molecular defect in vitro is achieved by incubation of cells with several classes of chemical chaperones, indicating that further investigation of novel small molecules is warranted as a means for producing new therapies for CF. Materials and Methods: The yeast two-hybrid assay was used to study the effect of CF-causing mutations on the ability of NBD1 to self-associate and form dimers. A yeast strain demonstrating defective growth as a result of impaired NBD1 dimerization due to ⌬F508 was used as a drug discovery bioassay for the identification of plant natural product compounds restoring mutant NBD1 interaction. Active compounds were purified and the chemical structures determined. The purified compounds were tested in epithelial cells expressing CFTR⌬F508

Osteopetrosis Mutation R444L Causes Endoplasmic Reticulum Retention and Misprocessing of Vacuolar H+-ATPase a3 Subunit

“…Thus, much effort has been expended in attempting to find a clinically viable pharmacological means of achieving trafficking of the mutant protein to the plasma membrane as a potential cure for a large percentage of cystic fibrosis cases (53,54). In a similar manner, a pharmacological chaperone that can rescue a3 R444L , especially if usable during early infancy, or in utero, might be of benefit to patients afflicted with a3 R444L -mediated ARO.…”

Rubescins A, B and C: New Havanensin Type Limonoids from Root Bark of <i>Trichilia rubescens</i> (Meliaceae)

“…Filtration and vacuum concentration of the resulting solution led to a dark greenish extract (yield: 15.5%). A bioassay-guided chromatographic fractionation over silica gel of the above extract, followed by purification using silica gel column chromatography resulted in the isolation of three new limonoids, rubescins A-C (1-3) and known compounds including, havanensin type limonoid TS3 (4), 7) β-sitosterol and stigmasterol as described in Experimental. The known compounds were identified by comparison of their spectroscopic data ( 1 H-, 13 C-NMR and mass spectra) with those reported in literature.…”

“…The known compounds were identified by comparison of their spectroscopic data ( 1 H-, 13 C-NMR and mass spectra) with those reported in literature. 7) Rubescin A 1, mp 234-236°C, [ quaternary carbons. These data suggested that 1 was a tetranorterpenoid similar to havanensin type limonoid TS3.…”

“…6) Previous chemical investigations of the leaves of this species have led to the isolation of a series of havanensin-type limonoids denoted TS1, TS2, TS3, and trichirubines A and B which have been found to increase chloride conductance in epithelial cells and to exhibit antimalarial activity. 7,8) As part of our ongoing research program on the Meliaceae family, 9) three new havanensin type limonoids named rubescins A-C (1-3) and three known compounds, were isolated from the root bark of Trichilia rubescens. Their structures were elucidated by spectroscopic methods.…”

An Extract from the Medicinal PlantPhyllanthus acidusand Its Isolated Compounds Induce Airway Chloride Secretion: A Potential Treatment for Cystic Fibrosis

“…Pharmacological interventions attempt to correct defective ion transport among other pulmonary phenotypes. Recent strategies make use of natural food components because of their ready accessibility and low toxicity (deCarvalho et al, 2002;Bjarnsholt et al, 2005;Egan et al, 2004). These compounds act in different ways, such as correcting the trafficking defect of mutant CFTR or potentiating residual CFTR activity (Kunzelmann and Mall, 2003;Moran and Zegarra-Moran, 2005;Van Goor et al, 2006).…”