Uehara Akira, Iwamoto Takahiro, Nakamura Yuki, Imanaga Issei
Department of Physiology, School of Medicine, Fukuoka University, 7-chome Nanakuma, Jonan-ku, Japan.
J Pharmacol Sci. 2004 Sep;96(1):19-22. doi: 10.1254/jphs.fmj04002x4. Epub 2004 Sep 10.
Sensitivities of the reverse-mode Na+/Ca2+ exchange activity measured as the Na+i-dependent Ca2+ uptake to extracellular monovalent cations K+, Li+, and Na+ were compared between the K+ -dependent (NCKX2) and the K+ -independent Na+/Ca2+ exchanger (NCX1) overexpressed in a fibroblast cell. Interestingly, the exchange activity of NCKX2 was not influenced by Li+ while it was increased by K+. On the contrary, the activity of NCX1 was increased by Li+. Thus, the cation sensitivities to K+ and Li+ markedly differed between NCKX2 and NCX1. In addition, Na+ exerted a significantly smaller inhibitory effect on the activity in NCKX2 than in NCX1. The Na+/Ca2+ exchange activities of NCKX2 and NCX1 are considered to be regulated differentially via the respective binding site domains that have distinct sensitivities to the external monovalent cations.
在成纤维细胞中过表达的钾离子依赖性（NCKX2）和非钾离子依赖性钠钙交换体（NCX1）之间，比较了以细胞内钠离子依赖性钙离子摄取来衡量的反向模式钠钙交换活性对细胞外单价阳离子钾离子、锂离子和钠离子的敏感性。有趣的是，NCKX2的交换活性不受锂离子影响，却因钾离子而增加。相反，NCX1的活性因锂离子而增加。因此，NCKX2和NCX1对钾离子和锂离子的阳离子敏感性明显不同。此外，钠离子对NCKX2活性的抑制作用明显小于对NCX1的抑制作用。NCKX2和NCX1的钠钙交换活性被认为是通过对外部单价阳离子具有不同敏感性的各自结合位点结构域进行差异调节的。
