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An Inwardly Rectifying Potassium Channel in Apical Membrane of Calu-3 Cells.
- Source :
-
Journal of Biological Chemistry . 11/5/2004, Vol. 279 Issue 45, p46558-46565. 8p. 1 Diagram, 2 Charts, 19 Graphs. - 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 ∼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. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00219258
- Volume :
- 279
- Issue :
- 45
- Database :
- Academic Search Index
- Journal :
- Journal of Biological Chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 15370560
- Full Text :
- https://doi.org/10.1074/jbc.M406058200