Identification and Functional Characterization of the First Nucleobase Transporter in Mammals
Identification and Functional Characterization of the First Nucleobase Transporter in Mammals
复制标题
哺乳动物中第一个核碱基转运蛋白的鉴定和功能表征
DOI：
10.1074/jbc.m109.032961
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
H. Yuasa
中科院分区：
文献类型：
--
作者：
Syunsuke Yamamoto;Katsuhisa Inoue;Tomoaki Murata;Syunsuke Kamigaso;Tomoya Yasujima;Jun;Y. Yoshida;Kin;H. Yuasa
核碱基是构成核苷和核酸的重要化合物。尽管长期以来人们一直认为特定的转运蛋白参与肠道吸收和其他组织的摄取，但迄今为止尚未在哺乳动物中鉴定出它们的分子实体。在这里，我们描述了大鼠 Slc23a4 作为第一个钠依赖性核碱基转运蛋白 (rSNBT1) 的鉴定。 rSNBT1 mRNA 仅在小肠中高表达。当在 HEK293 细胞中瞬时表达时，rSNBT1 可以最有效地转运尿嘧啶。 rSNBT1 介导的尿嘧啶转运是钠依赖性的，并且米氏常数为 21.2 μm 可饱和。胸腺嘧啶、鸟嘌呤、次黄嘌呤和黄嘌呤也被转运，但腺嘌呤却未被转运。对 rSNBT1 介导的尿嘧啶转运的抑制作用的研究还表明，rSNBT1 可以识别几种核碱基类似物（例如 5-氟尿嘧啶），但胞嘧啶和核苷不能识别或识别能力较差。此外，当在极化的Madin-Darby犬肾II细胞中稳定表达时，与绿色荧光蛋白融合的rSNBT1主要定位于顶膜。 rSNBT1 的这些特征几乎完全与参与肠道尿嘧啶摄取的载体介导的转运系统的特征完全一致。因此，rSNBT1 很可能是其分子实体，或者至少对此负有部分责任。研究还发现，与 rSNBT1 基因同源的基因在人类中存在遗传缺陷。这可能在核碱基的运输和代谢中具有生物学和进化意义。本研究为治疗用途的核碱基及其类似物的特定转运和代谢提供了新的见解。
Nucleobases are important compounds that constitute nucleosides and nucleic acids. Although it has long been suggested that specific transporters are involved in their intestinal absorption and uptake in other tissues, none of their molecular entities have been identified in mammals to date. Here we describe identification of rat Slc23a4 as the first sodium-dependent nucleobase transporter (rSNBT1). The mRNA of rSNBT1 was expressed highly and only in the small intestine. When transiently expressed in HEK293 cells, rSNBT1 could transport uracil most efficiently. The transport of uracil mediated by rSNBT1 was sodium-dependent and saturable with a Michaelis constant of 21.2 μm. Thymine, guanine, hypoxanthine, and xanthine were also transported, but adenine was not. It was also suggested by studies of the inhibitory effect on rSNBT1-mediated uracil transport that several nucleobase analogs such as 5-fluorouracil are recognized by rSNBT1, but cytosine and nucleosides are not or only poorly recognized. Furthermore, rSNBT1 fused with green fluorescent protein was mainly localized at the apical membrane, when stably expressed in polarized Madin-Darby canine kidney II cells. These characteristics of rSNBT1 were almost fully in agreement with those of the carrier-mediated transport system involved in intestinal uracil uptake. Therefore, it is likely that rSNBT1 is its molecular entity or at least in part responsible for that. It was also found that the gene orthologous to the rSNBT1 gene is genetically defective in humans. This may have a biological and evolutional meaning in the transport and metabolism of nucleobases. The present study provides novel insights into the specific transport and metabolism of nucleobases and their analogs for therapeutic use.
小鼠中嘌呤分解代谢酶的最高水平存在于近端小肠中。
DOI：
--
发表时间：
1993
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
Mohamedali,KA;Guicherit,OM;Kellems,RE;Rudolph,FB
通讯作者：
Rudolph,FB
DOI：
10.1073/pnas.86.23.9412
发表时间：
1989-12-01
影响因子：
11.1
作者：
WU, XW;LEE, CC;CASKEY, CT
通讯作者：
CASKEY, CT