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Correction of delF508-CFTR activity with benzo(c)quinolizinium compounds through facilitation of its processing in cystic fibrosis airway cells

¹ Department of Medical Biochemistry, University of Wales College of Medicine, Heath Park, Cardiff, CF14 4XN, UK
² Laboratoire physiologie des régulations cellulaires, UMR6558, Université de Poitiers, 40 avenue du recteur Pineau, 86022 Poitiers, France
³ Laboratoire de chimie organique, Faculté de médecine et de pharmacie de Poitiers, 34 rue du jardin des plantes, 86005 Poitiers, France
⁴ Department of Physiological Sciences, University Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
⁵ Laboratorio di genetica molecolare, Istituto Giannina Gaslini, 16148 Genova, Italy
⁶ Department of Child Health, University Hospital of Wales, Heath Park, Cardiff, CF14 4XN, UK

*Authors for correspondence (e-mail: frederic.becq{at}univ-poitiers.fr; dormer{at}cardiff.uk)

Accepted July 31, 2001

A number of genetic diseases, including cystic fibrosis, have been identified as disorders of protein trafficking associated with retention of mutant protein within the endoplasmic reticulum. In the presence of the benzo(c)quinolizinium drugs, MPB-07 and its congener MPB-91, we show the activation of cystic fibrosis transmembrane conductance regulator (CFTR) delF508 channels in IB3-1 human cells, which express endogenous levels of delF508-CFTR. These drugs were without effect on the Ca²⁺-activated Cl^– transport, whereas the swelling-activated Cl^– transport was found altered in MPB-treated cells. Immunoprecipitation and in vitro phosphorylation shows a 20% increase of the band C form of delF508 after MPB treatment. We then investigated the effect of these drugs on the extent of mislocalisation of delF508-CFTR in native airway cells from cystic fibrosis patients. We first showed that delF508 CFTR was characteristically restricted to an endoplasmic reticulum location in approximately 80% of untreated cells from CF patients homozygous for the delF508-CFTR mutation. By contrast, 60-70% of cells from non-CF patients showed wild-type CFTR in an apical location. MPB-07 treatment caused dramatic relocation of delF508-CFTR to the apical region such that the majority of delF508/delF508 CF cells showed a similar CFTR location to that of wild-type. MPB-07 had no apparent effect on the distribution of wild-type CFTR, the apical membrane protein CD59 or the ER membrane Ca²⁺,Mg-ATPase. We also showed a similar pharmacological effect in nasal cells freshly isolated from a delF508/G551D CF patient. The results demonstrate selective redirection of a mutant membrane protein using cell-permeant small molecules of the benzo(c)quinolizinium family and provide a major advance towards development of a targetted drug treatment for cystic fibrosis and other disorders of protein trafficking.

Key words: CFTR, delF508, Immunolocalisation, Human airway cells, Pharmacology, Trafficking

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