标题：Apamin as a selective blocker of the calcium-dependent potassium channel in neuroblastoma cells: voltage-clamp and biochemical characterization of the toxin receptor
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1982
卷号：79
期号：4
页码：1308-1312
DOI：10.1073/pnas.79.4.1308
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：This paper describes the interaction of apamin, a bee venom neurotoxin, with the mouse neuroblastoma cell membrane. Voltage-clamp analyses have shown that apamin at low concentrations specifically blocks the Ca2+-dependent K+ channel in differentiated neuroblastoma cells. Binding experiments with highly radiolabeled toxin indicate that the dissociation constant of the apamin-receptor complex in differentiated neuroblastoma cells is 15-22 pM and the maximal binding capacity is 12 fmol/mg of protein. The receptor is destroyed by proteases, suggesting that it is a protein. The binding capacity of neuroblastoma cells for radiolabeled apamin dramatically increases during the transition from the nondifferentiated to the differentiated state. The number of Ca2+-dependent K+ channels appears to be at most 1/5th the number of fast Na+ channels in differentiated neuroblastoma. The binding of radiolabeled apamin to its receptor is antagonized by monovalent and divalent cations. Na+ inhibition of the binding of 125I-labeled apamin is of the competitive type (Kd(Na+) = 44 mM). Guanidinium and guanidinated compounds such as amiloride or neurotensin prevent binding of 125I-labeled apamin, the best antagonist being neurotensin.
