Role of the Outward Delayed Rectifier K+ Current in Ceramide‐Induced Caspase Activation and Apoptosis in Cultured Cortical Neurons

• Published in: Journal of neurochemistry Vol. 73; no. 3; pp. 933 - 941
• Main Authors: Yu, Shan Ping, Yeh, Chen‐Hsiung, Gottron, Frank, Wang, Xin, Grabb, Margaret C., Choi, Dennis W.
• Format: Journal Article
• Language: English
• Published: Oxford UK Blackwell Science Ltd 01.09.1999; Blackwell
• Subjects: Ageing, cell death; Animals; Apoptosis - drug effects; Apoptosis - physiology; Biological and medical sciences; Calcium - physiology; Caspases - metabolism; Cell physiology; Cells, Cultured; Ceramide; Ceramides - pharmacology; Ceramides - physiology; Cerebral Cortex - cytology; Cerebral Cortex - drug effects; Cerebral Cortex - enzymology; Delayed Rectifier Potassium Channels; Enzyme Activation; Fundamental and applied biological sciences. Psychology; Membrane Potentials; Mice; Molecular and cellular biology; Neuronal apoptosis; Neurons - drug effects; Neurons - enzymology; Outward delayed rectifier Iκ channel; Patch-Clamp Techniques; Phosphorylation; Potassium Channel Blockers; Potassium Channels - metabolism; Potassium Channels, Voltage-Gated; Signal Transduction - physiology; Sphingomyelin Phosphodiesterase - metabolism; Tetraethylammonium - pharmacology; Tyrosine - metabolism; Tyrosine phosphorylation; Rodentia; Sphingolipid; Ionic current; Outward current; In vitro; Signal transduction; Vertebrata; Mammalia; Neuron; Mouse; Ceramide; Potassium; Apoptosis
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1046/j.1471-4159.1999.0730933.x

: We studied the novel hypothesis that an upmodulation of channels for outward delayed rectifier K+ current (Iκ) plays a key role in ceramide‐induced neuronal apoptosis. Exposure for 6‐10 h to the membrane‐permeable C2‐ceramide (25 μM) or to sphingomyelinase (0.2 unit/ml), but not to the inactive ceramide analogue C2‐dihydroceramide (25 μM), enhanced the whole‐cell Iκ 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 Iκ, 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 μM), suppressed Iκ enhancement and/or apoptosis induced by C2‐ceramide. It is suggested that ceramide‐induced Iκ current enhancement is mediated by tyrosine phosphorylation and plays a critical role in neuronal apoptosis.