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MEMBRANE TRANSPORTERS, ION CHANNELS, AND PUMPS
F508 CFTR trafficking and restores cAMP-stimulated anion secretion in cystic fibrosis epithelia
Departments of 1Biomedical Sciences and 2Medical Physiology and Pharmacology and Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri 65211
Submitted 5 August 2003 ; accepted in final form 10 March 2004
The major disease-causing mutation of the cystic fibrosis transmembrane conductance regulator (CFTR) is deletion of phenylalanine 508 (
F508), which adversely affects processing and plasma membrane targeting of CFTR. Under conditions predicted to stabilize protein folding,
F508 CFTR is capable of trafficking to the plasma membrane and retains cAMP-regulated anion channel activity. Overexpression is one factor that increases CFTR trafficking; therefore, we hypothesized that expression of a domain mimic of the first nucleotide-binding fold (NBF1) of CFTR, i.e., the site of F508, may be sufficient to overwhelm the quality control process or otherwise stabilize
F508 CFTR and thereby restore cAMP-stimulated anion secretion. In epithelial cells expressing recombinant
F508 human (h)CFTR, expression of wild-type NBF1 increased the amount of both core-glycosylated and mature protein to a greater extent than expression of
F508 NBF1. Expression of wild-type NBF1 in the
F508 hCFTR cells increased whole cell Cl current density to
50% of that in cells expressing wild-type hCFTR. Expression of NBF1 in polarized epithelial monolayers from a
F508/
F508 cystic fibrosis mouse (MGEF) restored cAMP-stimulated transepithelial anion secretion but not in monolayers from a CFTR-null mouse (MGEN). Restoration of anion secretion was sustained in NBF1-expressing MGEF for >30 passages, whereas MGEN corrected with hCFTR progressively lost anion secretion capability. We conclude that expression of a NBF1 domain mimic may be useful for correction of the
F508 CFTR protein trafficking defect in cystic fibrosis epithelia.
protein processing; mouse; retrovirus; gene therapy
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