Functional comparison of the three isoforms of the Na+/Ca2+ exchanger (NCX1, NCX2, NCX3)
Functional comparison of the three isoforms of the Na+/Ca2+ exchanger (NCX1, NCX2, NCX3)
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DOI：
10.1152/ajpcell.1998.274.2.c415
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发表时间：
1998-02-01
影响因子：
5.5
通讯作者：
Philipson, KD
中科院分区：
文献类型：
--
作者：
Linck, B;Qiu, ZY;Philipson, KD
三种不同的哺乳动物Na+/Ca 2+交换器已被克隆：NCX 1，NCX 2和NCX 3。我们对这三种交换器进行了详细的功能比较。每个交换器在BHK细胞的质膜中以高水平稳定表达。使用三种不同的互补技术评估Na+/Ca 2+交换活性：Na+梯度依赖性Ca-45（2+）摄取到完整细胞中，Na+梯度依赖性Ca-45（2+）摄取到从转染细胞分离的膜囊泡中，以及使用切下的细胞膜的巨大斑块测量交换电流。运输离子Na+和Ca 2+的表观亲和力显着相似的三个交换器在两个膜表面。同样地，获得了对pH变化、胰凝乳蛋白酶处理和各种抑制剂的应用的大致相似的响应。细胞ATP耗竭抑制了NCX 1和NCX 2的活性，但不影响NCX 3的活性。通过激活蛋白激酶A和C的试剂，NCX 1和NCX 3的交换活性适度增加。所有交换器都受细胞内Ca ~（2+）的调节。NCX 1诱导的交换电流特别大，在切除的补丁，像本地心肌交换，由ATP刺激。结果可能会受到我们选择的表达系统和特定剪接变体的影响，但总体而言，这三种交换剂似乎具有非常相似的性质。
Three distinct mammalian Na+/Ca2+ exchangers have been cloned: NCX1, NCX2, and NCX3. We have undertaken a detailed functional comparison of these three exchangers. Each exchanger was stably expressed at high levels in the plasma membranes of BHK cells. Na+/Ca2+ exchange activity was assessed using three different complementary techniques: Na+ gradient-dependent Ca-45(2+) uptake into intact cells, Na+ gradient-dependent Ca-45(2+) uptake into membrane vesicles isolated from the transfected cells, and exchange currents measured using giant patches of excised cell membrane. Apparent affinities for the transported ions Na+ and Ca2+ were markedly similar for the three exchangers at both membrane surfaces. Likewise, generally similar responses to changes in pH, chymotrypsin treatment, and application of various inhibitors were obtained. Depletion of cellular ATP inhibited NCX1 and NCX2 but did not affect the activity of NCX3. Exchange activities of NCX1 and NCX3 were modestly increased by agents that activate protein kinases A and C. All exchangers were regulated by intracellular Ca2+. NCX1-induced exchange currents were especially large in excised patches and, like the native myocardial exchanger, were stimulated by ATP. Results may be influenced by our choice of expression system and specific splice variants, but, overall, the three exchangers appear to have very similar properties.