Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. CFTR serves as a cAMP-stimulated chloride channel in a wide range of epithelial tissues and its dysfunction is a hallmark of CF. Over 1400 mutations in the CFTR gene are known, but functional data exist only for a minority of the mutant channels. The aim of the present study was to functionally characterize a novel CFTR mutation identified in a patient with atypical CF. Full length sequencing of the patient’s CFTR gene revealed a homozygous C to T transition at nucleotide position 331 (CCT>TCT), which results in a P67S amino acid substitution. Mutant and wild-type CFTR were heterologously expressed in Xenopus laevis oocytes. CFTR whole-cell currents were studied using the two-electrode voltage-clamp technique. Channel surface expression was assessed by a chemiluminescence assay. Expression of P67S-CFTR resulted in functional CFTR chloride channels. However, the CFTR chloride conductance observed in oocytes expressing the mutant channel averaged only 24% of that in oocytes expressing wild-type CFTR. Similarly, surface expression of the mutant channel was reduced. In contrast, the mutation did not alter the anion selectivity of the channel, and Western blot analysis indicated a similar protein expression level of mutant and wild-type CFTR. Our findings indicate that the P67S mutation reduces CFTR chloride channel function by reducing channel surface expression. The mild disease phenotype of the patient indicates that the residual function of the mutant channel is sufficient to prevent the development of severe CF symptoms.

Keywords:
CFTR, P67S mutation, Cystic fibrosis, Pancreatic insufficiency, Xenopus laevis oocytes, Chloride channel, Electrophysiology, Surface expression
This content is only available via PDF.
© 2007 S. Karger AG, Basel
2007
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.
You do not currently have access to this content.