Document Detail

Beta-adrenergic receptors couple to CFTR chloride channels of intercalated mitochondria-rich cells in the heterocellular toad skin epithelium.
MedLine Citation:
PMID:  14729151     Owner:  NLM     Status:  MEDLINE    
In the heterocellular toad skin epithelium the beta-adrenergic receptor agonist isoproterenol activates cyclic AMP-dependent Cl(-) channels that are not located in the principal cells. With four experimental approaches, in the present study, we tested the hypothesis that the signalling pathway targets cystic fibrosis transmembrane conductance regulator (CFTR)-chloride channels of mitochondria-rich cells. (i) Serosal application of isoproterenol (log(10)EC(50)=-7.1+/-0.2; Hill coefficient=1.1+/-0.2), as well as noradrenaline, activated an anion pathway with an apical selectivity sequence, G(Cl)>G(Br)> or =G(NO(3))>G(I), comparable to the published selectivity sequence of cloned human CFTR expressed in Xenopus oocytes. (ii) Known modulators of human CFTR, glibenclamide (200 micromol/l) and genistein (50 micromol/l), depressed and activated, respectively, the receptor-stimulated G(Cl). Genistein did not modify the anion selectivity. (iii) Transcellular voltage clamp studies of single isolated mitochondria-rich cells revealed functional beta-adrenergic receptors on the basolateral membrane. With approximately 60,000 mitochondria-rich cells per cm(2), the saturating activation of 11.9+/-1.6 nS/cell accounted for the measured isoproterenol-activated transepithelial conductance of 600-900 microS/cm(2). In forskolin-stimulated cells, glibenclamide (200 micromol/l) reversibly inhibited the transcellular conductance by 9.6+/-1.6 nS/cell. (iv) With primers constructed from cloned Xenopus CFTR and PCR amplification of reverse-transcribed mRNA from toad skin, full-length Bufo CFTR cDNA was generated. The derived protein of 1466 residues shows 86% homology with xCFTR and 89% homology with hCFTR. All major functional sequences, that is, the R- and the NBF1- and NBF2-domains are well-conserved as are the predicted transmembrane segments proposed to form the pore of the channel protein. These new results taken together with our previously identified small-conductance CFTR-like Cl(-) channel in the apical membrane of the mitochondria-rich cells lead to the conclusion that the toad's CFTR gene codes for a functional Cl(-) channel in the apical plasma membrane of this minority cell type.
Erik Hviid Larsen; Jan Amstrup; Niels J Willumsen
Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Biochimica et biophysica acta     Volume:  1618     ISSN:  0006-3002     ISO Abbreviation:  Biochim. Biophys. Acta     Publication Date:  2003 Dec 
Date Detail:
Created Date:  2004-01-19     Completed Date:  2004-03-23     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0217513     Medline TA:  Biochim Biophys Acta     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  140-52     Citation Subset:  IM    
August Krogh Institute, University of Copenhagen, Universitetsparken 13, DK-2100, Copenhagen, Denmark.
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MeSH Terms
Amino Acid Sequence
Bufo bufo
Cystic Fibrosis Transmembrane Conductance Regulator / chemistry,  genetics,  metabolism*
DNA, Complementary / biosynthesis,  chemistry
Epithelial Cells / chemistry,  drug effects,  metabolism
Epithelium / drug effects,  metabolism
Galvanic Skin Response
Genistein / pharmacology
Glyburide / pharmacology
Isoproterenol / pharmacology
Molecular Sequence Data
Patch-Clamp Techniques
Receptors, Adrenergic, beta / chemistry,  drug effects,  metabolism*
Sequence Alignment
Skin / chemistry,  metabolism*
Reg. No./Substance:
0/DNA, Complementary; 0/Receptors, Adrenergic, beta; 10238-21-8/Glyburide; 126880-72-6/Cystic Fibrosis Transmembrane Conductance Regulator; 446-72-0/Genistein; 7683-59-2/Isoproterenol

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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