Metabolic stress opens K+ channels in hepatoma cells through a Ca2+- and protein kinase calpha-dependent mechanism.
These studies of a model liver cell line evaluate the mechanisms responsible for regulated release of K+ ions during metabolic stress. Metabolic inhibition of HTC hepatoma cells by exposure to 2, 4-dinitrophenol (50 microM) and 2-deoxy-D-glucose (10 mM) stimulated outward currents carried by K+ of 974 +/- 75 pA at 0 mV (n = 20, p < 0.001). Currents were inhibited by chelation of intracellular Ca2+ or exposure to apamin (50 nM), an inhibitor of SKCa channels. In cell-attached recordings from intact cells, removal of metabolic substrates (25/28 cells) or exposure to metabolic inhibitors (32/40 cells) opened K+-selective channels with a conductance of 6.5 +/- 0. 2 pS. Channels had an open probability of 0.31 +/- 0.08 and opened in bursts averaging 3.55 +/- 0.27 ms in duration (n = 6). Metabolic stress was associated with rapid translocation of the alpha isoform of protein kinase C (PKCalpha) from cytosol to membrane; and down-regulation of PKCalpha by phorbol esters or exposure to the PKC inhibitor chelerythrine (10 microM) each inhibited currents. Moreover, intracellular perfusion with purified PKCalpha activated currents in a Ca2+- and concentration-dependent manner. These findings indicate that metabolic stress leads to opening of apamin-sensitive SKCa channels in hepatoma cells through a Ca2+- and PKC-dependent mechanism and suggest that PKCalpha may be selectively involved in the response. This mechanism functionally couples the metabolic state of cells to membrane K+ permeability and represents a potential target for modification of liver injury associated with ischemia and preservation.
Wang
Y
Y
Department of Medicine, Duke University Medical Center Durham, North Carolina 27710, USA.
Sostman
A
A
Roman
R
R
Stribling
S
S
Vigna
S
S
Hannun
Y
Y
Raymond
J
J
Fitz
J G
JG
D019297:2,4-Dinitrophenol; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D003847:Deoxyglucose / Q000494:pharmacology; D004140:Dinitrophenols / Q000494:pharmacology; D004553:Electric Conductivity; D017097:Electric Impedance; D004791:Enzyme Inhibitors; D015640:Ion Channel Gating; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008969:Molecular Sequence Data; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051571:Protein Kinase C-alpha; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D014407:Tumor Cells, Cultured; D017871:Calcium-Calmodulin-Dependent Protein Kinases
D019297:2,4-Dinitrophenol; D000255:Adenosine Triphosphate; D002118:Calcium; D003847:Deoxyglucose; D004140:Dinitrophenols; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D011188:Potassium; D015221:Potassium Channels; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases