在表达牛心脏钠钙交换体的转染中国仓鼠卵巢细胞中的钠钙交换和储存依赖性钙内流。毒胡萝卜素处理细胞中交换活性的加速。

Sodium-calcium exchange and store-dependent calcium influx in transfected chinese hamster ovary cells expressing the bovine cardiac sodium-calcium exchanger. Acceleration of exchange activity in thapsigargin-treated cells.

作者信息

Chernaya G, Vázquez M, Reeves J P

机构信息

Department of Physiology, University of Medicine and Dentistry of New Jersey, The New Jersey Medical School, Newark, 07103, USA.

出版信息

J Biol Chem. 1996 Mar 8;271(10):5378-85. doi: 10.1074/jbc.271.10.5378.

DOI:10.1074/jbc.271.10.5378

PMID:8621391

Abstract

The effects of extracellular Na+ on store-dependent Ca2+ influx were compared for transfected Chinese hamster ovary cells expressing the bovine cardiac Na+-Ca2+ exchanger (CK1.4 cells) and vector-transfected control cells. Store-dependent Ca2+ influx was elicited by depletion of intracellular Ca2+ stores with ionomycin, thapsigargin, or extracellular ATP, a purinergic agonist. In each case, the rise in [Ca2+]i upon the addition of extracellular Ca2+ was reduced in CK1.4 cells compared with control cells at physiological [Na+]o. When Li+ or NMDG was substituted for Na+, the CK1.4 cells showed a greater rise in [Ca2+]i than control cells over the subsequent 3 min after the addition of Ca2+o. Under Na+-free conditions, SK&F 96365 (50 microM), a blocker of store-operated Ca2+ channels, nearly abolished the thapsigargin-induced rise in [Ca2+]i in the control cells but only partially inhibited this response in the CK1.4 cells. We conclude that in the CK1.4 cells, Ca2+ entry through store-operated channels was counteracted by Na+o-dependent Ca2+ efflux at physiological [Na+]o, whereas Ca2+ entry was enhanced through Na+i-dependent Ca2+ influx in the Na+-free medium. We examined the effects of thapsigargin on Ba2+ entry in the CK1.4 cells because Ba2+ is transported by the Na+-Ca2+ exchanger, but it enters these cells only poorly through store-operated channels, and it is not sequestered by intracellular organelles. Thapsigargin treatment stimulated Ba2+ influx in a Na+-free medium, consistent with an acceleration of Ba2+ entry through the Na+-Ca2+ exchanger. We conclude that organellar Ca2+ release induces a regulatory activation of Na+-Ca2+ exchange activity.

摘要

比较了表达牛心脏钠钙交换体的转染中国仓鼠卵巢细胞（CK1.4细胞）和载体转染的对照细胞中细胞外Na⁺对储存依赖性Ca²⁺内流的影响。通过用离子霉素、毒胡萝卜素或细胞外ATP（一种嘌呤能激动剂）耗尽细胞内Ca²⁺储存来引发储存依赖性Ca²⁺内流。在每种情况下，与生理[Na⁺]ₒ条件下的对照细胞相比，添加细胞外Ca²⁺后CK1.4细胞中[Ca²⁺]i的升高有所降低。当用Li⁺或NMDG替代Na⁺时，在添加Ca²⁺ₒ后的随后3分钟内，CK1.4细胞中[Ca²⁺]i的升高比对照细胞更大。在无Na⁺条件下，储存操纵性Ca²⁺通道阻滞剂SK&F 96365（50微摩尔）几乎消除了毒胡萝卜素诱导的对照细胞中[Ca²⁺]i的升高，但仅部分抑制了CK1.4细胞中的这种反应。我们得出结论，在CK1.4细胞中，在生理[Na⁺]ₒ条件下，通过储存操纵性通道的Ca²⁺内流被Na⁺ₒ依赖性Ca²⁺外流抵消，而在无Na⁺培养基中，Ca²⁺内流通过Na⁺i依赖性Ca²⁺内流增强。我们研究了毒胡萝卜素对CK1.4细胞中Ba²⁺内流的影响，因为Ba²⁺由钠钙交换体转运，但它仅通过储存操纵性通道少量进入这些细胞，并且不会被细胞内细胞器螯合。毒胡萝卜素处理在无Na⁺培养基中刺激了Ba²⁺内流，这与通过钠钙交换体加速Ba²⁺进入一致。我们得出结论，细胞器Ca²⁺释放诱导钠钙交换活性的调节性激活。