Newcomb R, Szoke B, Palma A, Wang G, Chen X h, Hopkins W, Cong R, Miller J, Urge L, Tarczy-Hornoch K, Loo J A, Dooley D J, Nadasdi L, Tsien R W, Lemos J, Miljanich G
Elan Pharmaceuticals Inc., Menlo Park, California 94025, USA.
Biochemistry. 1998 Nov 3;37(44):15353-62. doi: 10.1021/bi981255g.
We describe the first potent and selective blocker of the class E Ca2+channel. SNX-482, a novel 41 amino acid peptide present in the venom of the African tarantula, Hysterocrates gigas, was identified through its ability to inhibit human class E Ca2+ channels stably expressed in a mammalian cell line. An IC50 of 15-30 nM was obtained for block of the class E Ca2+ channel, using either patch clamp electrophysiology or K+-evoked Ca2+ flux. At low nanomolar concentrations, SNX-482 also blocked a native resistant or R-type Ca2+ current in rat neurohypophyseal nerve terminals, but concentrations of 200-500 nM had no effect on R-type Ca2+ currents in several types of rat central neurons. The peptide has the sequence GVDKAGCRYMFGGCSVNDDCCPRLGCHSLFSYCAWDLTFSD-OH and is homologous to the spider peptides grammatoxin S1A and hanatoxin, both peptides with very different ion channel blocking selectivities. No effect of SNX-482 was observed on the following ion channel activities: Na+ or K+ currents in several cultured cell types (up to 500 nM); K+ current through cloned potassium channels Kv1.1 and Kv1. 4 expressed in Xenopus oocytes (up to 140 nM); Ca2+ flux through L- and T-type Ca2+ channels in an anterior pituitary cell line (GH3, up to 500 nM); and Ba2+ current through class A Ca2+ channels expressed in Xenopus oocytes (up to 280 nM). A weak effect was noted on Ca2+ current through cloned and stably expressed class B Ca2+ channels (IC50 > 500 nM). The unique selectivity of SNX-482 suggests its usefulness in studying the diversity, function, and pharmacology of class E and/or R-type Ca2+ channels.
我们描述了首个强效且具有选择性的E类钙离子通道阻滞剂。通过其抑制在哺乳动物细胞系中稳定表达的人类E类钙离子通道的能力，鉴定出了SNX-482，这是一种存在于非洲狼蛛（Hysterocrates gigas）毒液中的新型41个氨基酸的肽。使用膜片钳电生理学或钾离子诱发的钙离子通量法，获得了阻断E类钙离子通道的半数抑制浓度（IC50）为15 - 30 nM。在低纳摩尔浓度下，SNX-482还能阻断大鼠神经垂体神经末梢中的天然抗性或R型钙离子电流，但200 - 500 nM的浓度对几种类型的大鼠中枢神经元中的R型钙离子电流没有影响。该肽的序列为GVDKAGCRYMFGGCSVNDDCCPRLGCHSLFSYCAWDLTFSD - OH，与蜘蛛肽grammatoxin S1A和hanatoxin同源，这两种肽具有非常不同的离子通道阻断选择性。未观察到SNX-482对以下离子通道活性有影响：几种培养细胞类型中的钠离子或钾离子电流（高达500 nM）；非洲爪蟾卵母细胞中表达的克隆钾通道Kv1.1和Kv1.4的钾离子电流（高达140 nM）；垂体前叶细胞系（GH3，高达500 nM）中通过L型和T型钙离子通道的钙离子通量；以及非洲爪蟾卵母细胞中表达的A类钙离子通道的钡离子电流（高达280 nM）。观察到对通过克隆并稳定表达的B类钙离子通道的钙离子电流有微弱影响（IC50 > 500 nM）。SNX-482独特的选择性表明其在研究E类和/或R型钙离子通道的多样性、功能和药理学方面具有实用性。
