An inwardly rectifying potassium channel in apical membrane of Calu-3 cells

J Biol Chem. 2004 Nov 5;279(45):46558-65. doi: 10.1074/jbc.M406058200. Epub 2004 Aug 24.

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphate / chemistry
  • Adenosine Triphosphate / metabolism
  • Barium / chemistry
  • Cell Line
  • Cell Membrane / metabolism*
  • 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 / chemistry*
  • Potassium Channels, Inwardly Rectifying / metabolism
  • RNA, Messenger / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Time Factors

Substances

  • CFTR protein, human
  • Immediate-Early Proteins
  • Kcnj10 (channel)
  • Kir4.2 channel
  • Kir5.1 channel
  • Potassium Channels
  • Potassium Channels, Inwardly Rectifying
  • RNA, Messenger
  • Cystic Fibrosis Transmembrane Conductance Regulator
  • Cesium
  • Barium
  • Chlorine
  • Adenosine Triphosphate
  • GEM protein, human
  • Monomeric GTP-Binding Proteins
  • Potassium