Van Eylen F, Bollen A, Herchuelz A
Laboratory of Pharmacology, Brussels University School of Medicine, Bâtiment GE, 808 route de Lennik, B-1070 Brussels, Belgium.
J Endocrinol. 2001 Mar;168(3):517-26. doi: 10.1677/joe.0.1680517.
In the rat pancreatic beta-cell, Na/Ca exchange displays a quite high capacity. The cell is equipped with two alternatively spliced Na/Ca exchanger-1 (NCX1) isoforms, namely NCX1.3 and NCX1.7. To examine the existence of a possible functional difference between these splice variants, they were cloned, together with the heart variant NCX1.1, and expressed in human embryonic kidney-293 (HEK293) and Chinese hamster ovary (CHO) cells. In these two systems, the three splice variants showed a comparable level of intracellular Na+ (Na+(i))-dependent extracellular Ca2+(Ca2+(o)) uptake. Different levels of NCX1.3 and NCX1.7 transcripts were found in four rodent species, together with a marked interspecies difference in Na/Ca exchange activity. Three additional splice variants were found (NCX1.2, NCX1.9 and NCX1.13) in guinea-pigs, hamsters and mice, again in different proportions. Our data provide evidence for the activity of the three NCX1 splice variants. They also show the existence of a differential and species-specific transcription pattern of NCX1 gene products in pancreatic islet cells.
在大鼠胰腺β细胞中，钠钙交换具有相当高的能力。该细胞配备有两种可变剪接的钠钙交换体-1（NCX1）亚型，即NCX1.3和NCX1.7。为了研究这些剪接变体之间可能存在的功能差异，将它们与心脏变体NCX1.1一起克隆，并在人胚肾-293（HEK293）细胞和中国仓鼠卵巢（CHO）细胞中表达。在这两种系统中，三种剪接变体显示出相当水平的细胞内钠离子（Na⁺(i)）依赖性细胞外钙离子（Ca²⁺(o)）摄取。在四种啮齿动物物种中发现了不同水平的NCX1.3和NCX1.7转录本，同时钠钙交换活性存在明显的种间差异。在豚鼠、仓鼠和小鼠中又发现了另外三种剪接变体（NCX1.2、NCX1.9和NCX1.13），同样比例不同。我们的数据为三种NCX1剪接变体的活性提供了证据。它们还表明在胰岛细胞中存在NCX1基因产物的差异和物种特异性转录模式。
