Iron, manganese, and cobalt transport by Nramp1 (Slc11a1) and Nramp2 (Slc11a2) expressed at the plasma membrane
Iron, manganese, and cobalt transport by Nramp1 (Slc11a1) and Nramp2 (Slc11a2) expressed at the plasma membrane
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DOI：
10.1182/blood-2003-02-0425
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发表时间：
2003-09-01
期刊：
影响因子：
20.3
通讯作者：
Gros, P
中科院分区：
文献类型：
--
作者：
Forbes, JR;Gros, P
Nramp 1基因（Slc 11 a1）突变导致对细胞内病原体感染的易感性。Nramp 1蛋白在巨噬细胞和中性粒细胞的吞噬体膜上表达，是Nramp 2（Slc 11 a2）铁转运蛋白的一部分。Nramp 1在吞噬体膜上的转运机制仍然存在争议。通过将血凝素表位插入到预测的TM 7/8环中修饰的Nramp 1蛋白在中国仓鼠卵巢细胞的质膜上表达，如通过免疫荧光和表面生物素化所证明的。使用金属敏感荧光体钙黄绿素和Fura 2在Nramp 1 HA转染子中的实验表明，Nramp 1 HA可以介导Fe 2+、Mn 2+和Co 2+的摄取。在使用放射性同位素Fe-55（2+）和Mn-54（2+）的运输研究中也得到了类似的结果。Nramp 1HA运输依赖于时间，温度和酸性pH值，发生质子梯度。这些实验表明，与Fe 2+相比，Nramp 1HA可能是更有效的Mn 2+转运蛋白，并且与Nramp 2 HA相比，Nramp 1HA可能是更有效的Mn 2+转运蛋白。Nramp 1HA和Nramp 2 HA的膜拓扑结构和运输特性是不可区分的，这表明Nramp 1二价金属在吞噬体膜的运输是机械相似的Nramp 2在酸化的内体膜。这些结果阐明了Nramp 1有助于吞噬细胞防御感染的机制。
Mutations in the Nramp1 gene (Slc11a1) cause susceptibility to infection by intracellular pathogens. The Nramp1 protein is expressed at the phagosomal membrane of macrophages and neutrophils and is a paralog of the Nramp2 (Slc11a2) iron transporter. The Nramp1 transport mechanism at the phagosomal membrane has remained controversial. An Nramp1 protein modified by insertion of a hemagglutinin epitope into the predicted TM7/8 loop was expressed at the plasma membrane of Chinese hamster ovary cells as demonstrated by immunofluorescence and surface biotinylation. Experiments in Nramp1 HA transfectants using the metal-sensitive fluorophors calcein and Fura2 showed that Nramp1 HA can mediate Fe2+, Mn2+, and Co2+ uptake. Similar results were obtained in transport studies using radioisotopic Fe-55(2+) and Mn-54(2+). Nramp1HA transport was dependent on time, temperature, and acidic pH, occurring down the proton gradient. These experiments suggest that Nramp1HA may be a more efficient transporter of Mn2+ compared to Fe2+ and a more efficient Mn2+ transporter than Nramp2HA. The membrane topology and transport properties of Nramp1HA and Nramp2HA were indistinguishable, suggesting that Nramp1 divalent-metal transport at the phagosomal membrane is mechanistically similar to that of Nramp2 at the membrane of acidified endosomes. These results clarify the mechanism by which Nramp1 contributes to phagocyte defenses against infections.