Role of the outward delayed rectifier K+ current in ceramide-induced caspase activation and apoptosis in cultured cortical neurons.
We studied the novel hypothesis that an up-modulation of channels for outward delayed rectifier K+ current (I(K)) plays a key role in ceramide-induced neuronal apoptosis. Exposure for 6-10 h to the membrane-permeable C2-ceramide (25 microM) or to sphingomyelinase (0.2 unit/ml), but not to the inactive ceramide analogue C2-dihydroceramide (25 microM), enhanced the whole-cell I(K) current without affecting the transient A-type K+ current and increased caspase activity, followed by neuronal apoptosis 24 h after exposure onset. Tetraethylammonium (TEA) or 4-chloro-N,N-diethyl-N-heptylbenzenebutanaminium tosylate (clofilium), at concentrations inhibiting I(K), attenuated the C2-ceramide-induced caspase-3-like activation as well as neuronal apoptosis. Raising extracellular K+ to 25 mM similarly blocked the C2-ceramide-induced cell death; the neuroprotection by 25 mM K+ or TEA was not eliminated by blocking voltage-gated Ca2+ channels. An inhibitor of tyrosine kinases, herbimycin A (10 nM) or lavendustin A (0.1-1 microM), suppressed I(K) enhancement and/or apoptosis induced by C2-ceramide. It is suggested that ceramide-induced I(K) current enhancement is mediated by tyrosine phosphorylation and plays a critical role in neuronal apoptosis.
Yu
S P
SP
Center for the Study of Nervous System Injury and Department of Neurology, Washington University School of Medicine, St. Louis, Missouri, USA.
Yeh
C H
CH
Gottron
F
F
Wang
X
X
Grabb
M C
MC
Choi
D W
DW
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002118:Calcium / Q000502:physiology; D020169:Caspases / Q000378:metabolism*; D002478:Cells, Cultured; D002518:Ceramides / Q000494:pharmacology / Q000502:physiology*; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D051668:Delayed Rectifier Potassium Channels; D004789:Enzyme Activation; D008564:Membrane Potentials; D051379:Mice; D009474:Neurons / Q000187:drug effects / Q000201:enzymology*; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D015398:Signal Transduction / Q000502:physiology; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism; D019789:Tetraethylammonium / Q000494:pharmacology; D014443:Tyrosine / Q000378:metabolism
D002518:Ceramides; D051668:Delayed Rectifier Potassium Channels; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D014443:Tyrosine; D019789:Tetraethylammonium; D013108:Sphingomyelin Phosphodiesterase; D020169:Caspases; D002118:Calcium