Identification and characterization of a novel mammalian Mg2+ transporter with channel-like properties.
Identification and characterization of a novel mammalian Mg2+ transporter with channel-like properties.
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DOI：
10.1186/1471-2164-6-48
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发表时间：
2005-04-01
期刊：
影响因子：
4.4
通讯作者：
Quamme GA
中科院分区：
文献类型：
--
作者：
Goytain A;Quamme GA
细胞内镁含量丰富，受调控程度高，在生物化学功能中起重要作用。尽管有大量证据表明哺乳动物中存在独特的Mg2+转运体，但迄今为止，很少有蛋白质被生物化学鉴定出具有这种作用。我们已经证明，上皮镁的保护在一定程度上是由导致Mg2+运输调节的差异基因表达控制的。我们利用这些知识鉴定出一种受镁调控的新基因。寡核苷酸微阵列分析用于鉴定一个新的人类基因，该基因编码参与Mg2+诱发转运的蛋白质。我们已经指定了这种镁转运蛋白（MagT1）。MagT1是一种新的蛋白质，与其他已知的转运蛋白没有氨基酸序列相同。相应的cDNA包括1005个碱基对的开放阅读框，编码335个氨基酸的蛋白质。它具有五个假定的跨膜（TM）区域，其中有一个裂解位点，一个n -糖基化位点和一些磷酸化位点。根据Northern对小鼠组织的分析，在许多组织中存在2.4千碱基的转录本。当在非洲爪蟾卵母细胞中表达时，MagT1介导饱和Mg2+摄取，Michaelis常数为0.23 mM。通过MagT1运输Mg2+具有变变性，电压依赖性，不表现出任何时间依赖性失活。传输对Mg2+是非常特殊的，因为其他二价阳离子不会引起电流。在表达magt1的卵母细胞中，外部高浓度的某些阳离子（Ni2+、Zn2+、Mn2+）会抑制Mg2+的转运。Ca2+和Fe2+无影响。实时逆转录聚合酶链反应和特异性抗体的Western blot分析表明，低镁培养基培养的肾上皮细胞和低镁饮食小鼠的肾皮质中，MagT1 mRNA和蛋白分别比正常培养基培养的小鼠增加了约2.1倍和32%。因此，很明显，mRNA水平的增加转化为更高的蛋白质表达。这些研究表明，MagT1可能为上皮细胞中的Mg2+运输提供了一种选择性和受调控的途径。
Intracellular magnesium is abundant, highly regulated and plays an important role in biochemical functions. Despite the extensive evidence for unique mammalian Mg2+ transporters, few proteins have been biochemically identified to date that fulfill this role. We have shown that epithelial magnesium conservation is controlled, in part, by differential gene expression leading to regulation of Mg2+ transport. We used this knowledge to identify a novel gene that is regulated by magnesium. Oligonucleotide microarray analysis was used to identify a novel human gene that encodes a protein involved with Mg2+-evoked transport. We have designated this magnesium transporter (MagT1) protein. MagT1 is a novel protein with no amino acid sequence identity to other known transporters. The corresponding cDNA comprises an open reading frame of 1005 base pairs encoding a protein of 335 amino acids. It possesses five putative transmembrane (TM) regions with a cleavage site, a N-glycosylation site, and a number of phosphorylation sites. Based on Northern analysis of mouse tissues, a 2.4 kilobase transcript is present in many tissues. When expressed in Xenopus laevis oocytes, MagT1 mediates saturable Mg2+ uptake with a Michaelis constant of 0.23 mM. Transport of Mg2+ by MagT1 is rheogenic, voltage-dependent, does not display any time-dependent inactivation. Transport is very specific to Mg2+ as other divalent cations did not evoke currents. Large external concentrations of some cations inhibited Mg2+ transport (Ni2+, Zn2+, Mn2+) in MagT1-expressing oocytes. Ca2+and Fe2+ were without effect. Real-time reverse transcription polymerase chain reaction and Western blot analysis using a specific antibody demonstrated that MagT1 mRNA and protein is increased by about 2.1-fold and 32%, respectively, in kidney epithelial cells cultured in low magnesium media relative to normal media and in kidney cortex of mice maintained on low magnesium diets compared to those animals consuming normal diets. Accordingly, it is apparent that an increase in mRNA levels is translated into higher protein expression. These studies suggest that MagT1 may provide a selective and regulated pathway for Mg2+ transport in epithelial cells.
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影响因子：
4.8
作者：
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