Maitotoxin converts the plasmalemmal Ca(2+) pump into a Ca(2+)-permeable nonselective cation channel.
Maitotoxin converts the plasmalemmal Ca(2+) pump into a Ca(2+)-permeable nonselective cation channel.
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Maitotoxin 将质膜 Ca(2 ) 泵转化为 Ca(2 ) 可渗透的非选择性阳离子通道。
DOI：
10.1152/ajpcell.00252.2009
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
Schilling,WilliamP
中科院分区：
文献类型：
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作者：
Sinkins,WilliamG;Estacion,Mark;Prasad,Vikram;Goel,Monu;Shull,GaryE;Kunze,DianaL;Schilling,WilliamP
麦芽毒素 (MTX) 激活 Ca2+ 渗透性非选择性阳离子通道，并导致迄今为止检查的每个细胞中胞质游离 Ca2+ 浓度 ([Ca2+]i) 急剧增加，但所涉及通道的分子身份仍然未知。一条线索来自于对一种结构相关的海洋毒素——海藻毒素（PTX）的研究。 PTX 与质膜 Na+-K+-ATP 酶 (NKA) 结合，并将 Na+ 泵转化为非选择性阳离子通道。鉴于MTX通道对Ca2+的高渗透性，我们考虑了MTX可能与质膜Ca2+-ATP酶（PMCA）泵结合的可能性，并且像PTX一样，将泵转化为通道。为了验证这一假设，PMCA 在草地贪夜蛾 (Sf9) 昆虫细胞和人胚肾 (HEK) 293 细胞中过表达。在这两种细胞类型中，PMCA 表达的增强与 MTX 诱导的全细胞膜电流的显着增加相关。 MTX 对野生型和 PMCA 过表达 HEK 细胞中全细胞电流的影响对包括 Ca2+ 和 ATP 在内的泵配体敏感。通过使用小干扰RNA敲低HEK细胞中的PMCA1或来自具有PMCA1(+/-)PMCA4(−/−)基因型的转基因小鼠的小鼠胚胎成纤维细胞中的PMCA1，MTX诱导的电流显着降低。最后，分离的膜或纯化的 PMCA 制剂中的 PMCA 催化活性（即 Ca2+-ATP 酶）被 MTX 抑制。总之，这些结果表明 MTX 结合 PMCA 泵并将其转化为 Ca2+ 渗透性非选择性阳离子通道。
Maitotoxin (MTX) activates Ca2+-permeable nonselective cation channels and causes a dramatic increase in cytosolic free Ca2+concentration ([Ca2+]i) in every cell examined to date, but the molecular identity of the channels involved remains unknown. A clue came from studies of a structurally related marine toxin called palytoxin (PTX). PTX binds to the plasmalemmal Na+-K+-ATPase (NKA) and converts the Na+pump into a nonselective cation channel. Given the high permeability of the MTX channel for Ca2+, we considered the possibility that MTX may bind to the plasmalemmal Ca2+-ATPase (PMCA) pump, and like PTX, convert the pump into a channel. To test this hypothesis, the PMCA was overexpressed inSpodoptera frugiperda(Sf9) insect cells and in human embryonic kidneys (HEK) 293 cells. In both cell types, enhanced expression of the PMCA was associated with a significant increase in MTX-induced whole cell membrane currents. The effect of MTX on whole cell currents in both wild-type and PMCA overexpressing HEK cells was sensitive to pump ligands including Ca2+and ATP. MTX-induced currents were significantly reduced by knockdown of PMCA1 in HEK cells using small interfering RNA or in mouse embryonic fibroblasts from genetically modified mice with thePMCA1(+/−)PMCA4(−/−) genotype. Finally, PMCA catalytic activity (i.e., Ca2+-ATPase) in isolated membranes, or in purified PMCA preparations, was inhibited by MTX. Together, these results suggest that MTX binds to and converts the PMCA pump into a Ca2+-permeable nonselective cation channel.