Activation of phospholipase C in SH-SY5Y neuroblastoma cells by potassium-induced calcium entry.
1. We used SH-SY5Y human neuroblastoma cells to investigate whether depolarization with high K+ could stimulate inositol (1,4,5)trisphosphate (Ins(1,4,5)P3) formation and, if so, the mechanism involved. 2. Ins(1,4,5)P3 was measured by a specific radioreceptor mass assay, whilst [Ca2+]i was measured fluorimetrically with the Ca2+ indicator dye, Fura-2. 3. Depolarization with K+ caused a time- and dose-dependent increase in [Ca2+]i (peak at 27 s, EC50 of 50.0 +/- 9.0 mM) and Ins(1,4,5)P3 formation (peak at 30 s, EC50 of 47.4 +/- 1.1 mM). 4. Both the K(+)-induced Ins(1,4,5)P3 formation and increase in [Ca2+]i were inhibited dose-dependently by the L-type voltage-sensitive Ca2+ channel closer, (R+)-BayK8644, with IC50 values of 53.4 nM and 87.9 nM respectively. 5. These data show a close temporal and dose-response relationship between Ca2+ entry via L-type voltage-sensitive Ca2+ channels and Ins(1,4,5)P3 formation following depolarization with K+, indicating that Ca2+ influx can activate phospholipase C in SH-SY5Y cells.
University Department of Anaesthesia, Leicester Royal Infirmary.
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D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects; D002478:Cells, Cultured / Q000187:drug effects; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D009447:Neuroblastoma; D011188:Potassium / Q000494:pharmacology*; D013997:Time Factors; D010738:Type C Phospholipases / Q000187:drug effects*
D015220:Calcium Channels; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D015544:Inositol 1,4,5-Trisphosphate; D010738:Type C Phospholipases; D011188:Potassium; D002118:Calcium