Molecular characterization of volume-sensitive SKCa channels in human liver cell lines

Richard Roman, Andrew P. Feranchak, Marlyn Troetsch, Jeffrey C. Dunkelberg, Gordon Kilic, Thorsten Schlenker, Jerome Schaack, J. Gregory Fitz

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36 Scopus citations

Abstract

In human liver, Ca2+-dependent changes in membrane K+ permeability play a central role in coordinating functional interactions between membrane transport, metabolism, and cell volume. On the basis of the observation that K+ conductance is partially sensitive to the bee venom toxin apamin, we aimed to assess whether small-conductance Ca2+-sensitive K+ (SKCa) channels are expressed endogenously and contribute to volume-sensitive K+ efflux and cell volume regulation. We isolated a full-length 2,140-bp cDNA (hSK2) highly homologous to rat brain rSK2 cDNA, including the putative apamin-sensitive pore domain, from a human liver cDNA library. Identical cDNAs were isolated from primary human hepatocytes, human HuH-7 hepatoma cells, and human Mz-ChA-1 cholangiocarcinoma cells. Transduction of Chinese hamster ovary cells with a recombinant adenovirus encoding the hSK2-green fluorescent protein fusion construct resulted in expression of functional apamin-sensitive K+ channels. In Mz-ChA-1 cells, hypotonic (15% less sodium glutamate) exposure increased K+ current density (1.9 ± 0.2 to 37.5 ± 7.1 pA/pF; P < 0.001). Apamin (10-100 nM) inhibited K+ current activation and cell volume recovery from swelling. Apamin-sensitive SKca channels are functionally expressed in liver and biliary epithelia and likely contribute to volume-sensitive changes in membrane K+ permeability. Accordingly, the hSK2 protein is a potential target for pharmacological modulation of liver transport and metabolism through effects on membrane K+ permeability.

Original languageEnglish (US)
Pages (from-to)G116-G122
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume282
Issue number1 45-1
StatePublished - Jun 27 2002

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Keywords

  • Apamin
  • Cell volume
  • Cholangiocyte
  • Hepatocyte

ASJC Scopus subject areas

  • Physiology
  • Hepatology
  • Gastroenterology
  • Physiology (medical)

Cite this

Roman, R., Feranchak, A. P., Troetsch, M., Dunkelberg, J. C., Kilic, G., Schlenker, T., Schaack, J., & Gregory Fitz, J. (2002). Molecular characterization of volume-sensitive SKCa channels in human liver cell lines. American Journal of Physiology - Gastrointestinal and Liver Physiology, 282(1 45-1), G116-G122.