ZIP8, member of the solute-carrier-39 (SLC39) metal-transporter family: Characterization of transporter properties
ZIP8, member of the solute-carrier-39 (SLC39) metal-transporter family: Characterization of transporter properties
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DOI：
10.1124/mol.106.021521
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发表时间：
2006-07-01
影响因子：
3.6
通讯作者：
Nebert, Daniel W.
中科院分区：
文献类型：
--
作者：
He, Lei;Girijashanker, Kuppuswami;Nebert, Daniel W.
镉是一种广泛存在于环境中的危险金属。我们实验室的成员最近发现了由小鼠SLc39a8基因编码的ZIP8转运蛋白，负责应对镉对睾丸损伤的遗传差异。在小鼠胎儿成纤维细胞(rvZIP8细胞)中，稳定的逆转录病毒感染ZIP8基因导致细胞内镉的内流和积累速度增加10倍。在本研究中，我们发现镉的吸收在pH为7.5，温度为37℃时最大，并被氰化物抑制。在测试的十几种阳离子中，锰(II)是吸收镉的最好的竞争性阳离子。吸收Cd~(2+)的K-m为0.62µM，吸收Mn~(2+)的K-m为2.2µM，说明锰可能是ZIP8的生理底物。镉的吸收与钠、钾或氯离子无关，但强烈依赖于碳酸氢盐的存在。通过对rvZIP8细胞的Western印迹分析，我们发现ZIP8蛋白是糖基化的。在Madin-Darby犬肾脏极化上皮细胞中，利用Z-叠加式共聚焦显微镜，我们发现ZIP8定位于肾顶端，提示ZIP8在锰或镉的摄取和处置中起重要作用。很可能ZIP8是一个Mn2+/HCO3-转运体，穿过质膜的HCO3-梯度是吸收锰的驱动力，而镉可能是一个无赖的搭便车者，取代了锰而导致镉相关疾病。
Cadmium is a dangerous metal distributed widely in the environment. Members of our laboratory recently identified the ZIP8 transporter protein, encoded by the mouse Slc39a8 gene, to be responsible for genetic differences in response to cadmium damage of the testis. Stable retroviral infection of the ZIP8 cDNA in mouse fetal fibroblast cultures (rvZIP8 cells) leads to as much as a 10-fold increase in the rate of intracellular cadmium influx and accumulation. In the present study, we showed that cadmium uptake operated maximally at pH 7.5 and a temperature of 37 degrees C and was inhibited by cyanide. Of more than a dozen cations tested, manganese(II) was the best competitive cation for cadmium uptake. The K-m for Cd2+ uptake was 0.62 mu M, and the K-m for Mn2+ uptake was 2.2 mu M; thus, manganese is probably the physiological substrate for ZIP8. Cadmium uptake was independent of sodium, potassium or chloride ions, but strongly dependent on the presence of bicarbonate. By Western blot analysis of rvZIP8 cells, we showed that ZIP8 protein was glycosylated. Using Z-stack confocal microscopy in Madin-Darby canine kidney polarized epithelial cells, we found that ZIP8 was localized on the apical side implying an important role for manganese or cadmium uptake and disposition. It is likely that ZIP8 is a Mn2+/HCO3- symporter, that a HCO3- gradient across the plasma membrane acts as the driving force for manganese uptake, and that cadmium is a rogue hitchhiker displacing manganese to cause cadmium-associated disease.