THAPSIGARGIN, A TUMOR PROMOTER, DISCHARGES INTRACELLULAR CA-2+ STORES BY SPECIFIC-INHIBITION OF THE ENDOPLASMIC-RETICULUM CA-2+-ATPASE
THAPSIGARGIN, A TUMOR PROMOTER, DISCHARGES INTRACELLULAR CA-2+ STORES BY SPECIFIC-INHIBITION OF THE ENDOPLASMIC-RETICULUM CA-2+-ATPASE
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DOI：
10.1073/pnas.87.7.2466
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发表时间：
1990-04-01
影响因子：
11.1
通讯作者：
DAWSON, AP
中科院分区：
文献类型：
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作者：
THASTRUP, O;CULLEN, PJ;DAWSON, AP
Thapsigargin 是一种促进肿瘤的倍半萜内酯，在大鼠肝细胞中释放细胞内 Ca2+，就像在许多脊椎动物细胞类型中一样。它似乎在细胞内起作用，因为将分离的大鼠肝微粒体与毒胡萝卜素一起孵育会诱导储存的 Ca2+ 快速、剂量依赖性释放。毒胡萝卜素可释放的微粒体 Ca2+ 库包括对肌醇 1,4,5-三磷酸和 GTP 敏感的库。毒胡萝卜素预处理微粒体会阻止随后加载 45Ca2+，表明其目标是内质网的 ATP 依赖性 Ca2+ 泵。这一假设得到了以下证据的有力支持：毒胡萝卜素可快速抑制大鼠肝微粒体的 Ca2+ 激活的 ATP 酶活性，其剂量依赖性与全细胞或分离的微粒体 Ca2+ 放电中所见的剂量依赖性相同。对 Ca2+-ATP 酶内质网亚型的抑制具有高度选择性，因为毒胡萝卜素对肝细胞或红细胞质膜或心肌或骨骼肌肌浆网的 Ca2+-ATP 酶影响很小或没有影响。这些结果表明，毒胡萝卜素通过内质网 Ca2+ 泵的急性和高度特异性停滞，然后从至少两个药理学不同的 Ca2+ 库中快速泄漏 Ca2+，从而增加敏感细胞中胞质游离 Ca2+ 的浓度。讨论了毒胡萝卜素在 Ca2+ 稳态分析中应用的作用机制以及 Ca2+ 控制的可能形式的影响。
Thapsigargin, a tumor-promoting sesquiterpene lactone, discharges intracellular Ca2+ in rat hepatocytes, as it does in many vertebrate cell types. It appears to act intracellularly, as incubation of isolated rat liver microsomes with thapsigargin induces a rapid, dose-dependent release of stored Ca2+. The thapsigargin-releasable pool of microsomal Ca2+ includes the pools sensitive to inositol 1,4,5-trisphosphate and GTP. Thapsigargin pretreatment of microsomes blocks subsequent loading with 45Ca2+, suggesting that its target is the ATP-dependent Ca2+ pump of endoplasmic reticulum. This hypothesis is strongly supported by the demonstration that thapsigargin causes a rapid inhibition of the Ca2+-activated ATPase activity of rat liver microsomes, with an identical dose dependence to that seen in whole cell or isolated microsome Ca2+ discharge. The inhibition of the endoplasmic reticulum isoform of the Ca2+-ATPase is highly selective, as thapsigargin has little or no effect on the Ca2+-ATPase of hepatocyte or erythrocyte plasma membrane or of cardiac or skeletal muscle sarcoplasmic reticulum. These results suggest that thapsigargin increases the concentration of cytosolic free Ca2+ in sensitive cells by an acute and highly specific arrest of the endoplasmic reticulum Ca2+ pump, followed by a rapid Ca2+ leak from at least two pharmacologically distinct Ca2+ stores. The implications of this mechanism of action for the application of thapsigargin in the analysis of Ca2+ homeostasis and possible forms of Ca2+ control are discussed.