Csi. Nobel et al., Inhibition of Na+/K+-ATPase may be one mechanism contributing to potassiumefflux and cell shrinkage in CD95-induced apoptosis, APOPTOSIS, 5(2), 2000, pp. 153-163
To investigate the involvement of K+ efflux in apoptotic cell shrinkage, we
monitored efflux of the K+ congener, Rb-86(+), 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 Rb-
86(+) efflux, and a decrease in cell volume compared with control cells. Pr
eincubating Jurkat cells with Val-Ala-Asp-chloromethylketone (VAD-cmk), an
inhibitor of caspase proteases, prevented the observed Rb-86(+) efflux and
cell shrinkage induced by the anti- CD95 antibody. A wide range of inhibito
rs against most types of K+ channels could not inhibit CD95-mediated efflux
of Rb-86(+), however, the uptake of Rb-86(+) by Jurkat cells was severely
compromised when treated with anti-CD95 antibody. Uptake of Rb-86(+) in Jur
kat cells was sensitive to ouabain (a specific Na+/K+-ATPase inhibitor), de
monstrating Na+/K+-ATPase dependent K+ uptake. Ouabain induced significant
Rb-86(+) efflux in untreated cells, as well as it seemed to compete with Rb
-86(+) efflux induced by the anti-CD95 antibody, supporting a role for Na+/
K+-ATPase in the CD95-mediated Rb-86(+) 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 ma
y also facilitate apoptotic cell shrinkage.