Inhibition of Na+/K(+)-ATPase may be one mechanism contributing to potassium efflux and cell shrinkage in CD95-induced apoptosis.
To investigate the involvement of K+ efflux in apoptotic cell shrinkage, we monitored efflux of the K+ congener, 86Rb+, and cell volume during CD95-mediated apoptosis in Jurkat cells. An anti-CD95 antibody caused apoptosis associated with intracellular GSH depletion, a significant increase in 86Rb+ efflux, and a decrease in cell volume compared with control cells. Preincubating Jurkat cells with Val-Ala-Asp-chloromethylketone (VAD-cmk), an inhibitor of caspase proteases, prevented the observed 86Rb+ efflux and cell shrinkage induced by the anti-CD95 antibody. A wide range of inhibitors against most types of K+ channels could not inhibit CD95-mediated efflux of 86Rb+, however, the uptake of 86Rb+ by Jurkat cells was severely compromised when treated with anti-CD95 antibody. Uptake of 86Rb+ in Jurkat cells was sensitive to ouabain (a specific Na+/K(+)-ATPase inhibitor), demonstrating Na+/K(+)-ATPase dependent K+ uptake. Ouabain induced significant 86Rb+ efflux in untreated cells, as well as it seemed to compete with 86Rb+ efflux induced by the anti-CD95 antibody, supporting a role for Na+/K(+)-ATPase in the CD95-mediated 86Rb+ efflux. Ouabain treatment of Jurkat cells did not cause a reduction in cell volume, although together with the anti-CD95 antibody, ouabain potentiated CD95-mediated cell shrinkage. This suggests that the observed inhibition of Na+/K(+)-ATPase during apoptosis may also facilitate apoptotic cell shrinkage.
Institute of Environmental Medicine, Division of Toxicology, Karolinska Institutet, Box 210, S-171 77 Stockholm, Sweden. stefan.nobel@eu.pnu.com
C S
CS
Nobel
J K
JK
Aronson
D J
DJ
van den Dobbelsteen
A F
AF
Slater
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis; D001692:Biological Transport / Q000187:drug effects; D048429:Cell Size / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D010042:Ouabain / Q000494:pharmacology*; D011188:Potassium / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012414:Rubidium Radioisotopes / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D019014:fas Receptor / Q000378:metabolism*
D000590:Amino Acid Chloromethyl Ketones; D004791:Enzyme Inhibitors; D012414:Rubidium Radioisotopes; D019014:fas Receptor; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D005978:Glutathione; D011188:Potassium