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An inwardly rectifying potassium channel in apical membrane of Calu-3 cells.
- Source :
-
The Journal of biological chemistry [J Biol Chem] 2004 Nov 05; Vol. 279 (45), pp. 46558-65. Date of Electronic Publication: 2004 Aug 24. - Publication Year :
- 2004
-
Abstract
- Patch clamp methods and reverse transcription-polymerase chain reaction (RT-PCR) were used to characterize an apical K+ channel in Calu-3 cells, a widely used model of human airway gland serous cells. In cell-attached and excised apical membrane patches, we found an inwardly rectifying K+ channel (Kir). The permeability ratio was PNa/PK = 0.058. In 30 patches with both cystic fibrosis transmembrane conductance regulator and Kir present, we observed 79 cystic fibrosis transmembrane conductance regulator and 58 Kir channels. The average chord conductance was 24.4 +/- 0.5 pS (n = 11), between 0 and -200 mV, and was 9.6 +/- 0.7 pS (n = 8), between 0 and 50 mV; these magnitudes and their ratio of approximately 2.5 are most similar to values for rectifying K+ channels of the Kir4.x subfamilies. We attempted to amplify transcripts for Kir4.1, Kir4.2, and Kir5.1; of these only Kir4.2 was present in Calu-3 lysates. The channel was only weakly activated by ATP and was relatively insensitive to internal pH. External Cs+ and Ba2+ blocked the channel with Kd values in the millimolar range. Quantitative modeling of Cl- secreting epithelia suggests that secretion rates will be highest and luminal K+ will rise to 16-28 mm if 11-25% of the total cellular K+ conductance is placed in the apical membrane (Cook, D. I., and Young, J. A. (1989) J. Membr. Biol. 110, 139-146). Thus, we hypothesize that the K+ channel described here optimizes the rate of secretion and is involved in K+ recycling for the recently proposed apical H+ -K+ -ATPase in Calu-3 cells.
- Subjects :
- Adenosine Triphosphate chemistry
Adenosine Triphosphate metabolism
Barium chemistry
Cell Line
Cesium chemistry
Chlorine chemistry
Cystic Fibrosis Transmembrane Conductance Regulator metabolism
Dose-Response Relationship, Drug
Electrophysiology
Humans
Hydrogen-Ion Concentration
Immediate-Early Proteins metabolism
Kinetics
Monomeric GTP-Binding Proteins metabolism
Patch-Clamp Techniques
Potassium chemistry
Potassium Channels, Inwardly Rectifying metabolism
RNA, Messenger metabolism
Reverse Transcriptase Polymerase Chain Reaction
Time Factors
Kir5.1 Channel
Cell Membrane metabolism
Potassium Channels chemistry
Subjects
Details
- Language :
- English
- ISSN :
- 0021-9258
- Volume :
- 279
- Issue :
- 45
- Database :
- MEDLINE
- Journal :
- The Journal of biological chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 15328350
- Full Text :
- https://doi.org/10.1074/jbc.M406058200