GLUTX1, a novel mammalian glucose transporter expressed in the central nervous system and insulin-sensitive tissues
GLUTX1, a novel mammalian glucose transporter expressed in the central nervous system and insulin-sensitive tissues
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DOI：
10.1074/jbc.275.7.4607
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发表时间：
2000-02-18
影响因子：
4.8
通讯作者：
Thorens, B
中科院分区：
文献类型：
--
作者：
Ibberson, M;Uldry, M;Thorens, B
基于与GLUT 1 -5的同源性，我们分离了一种新的葡萄糖转运蛋白GLUTX 1的cDNA。该cDNA编码478个氨基酸的蛋白质，与大鼠GLUT 1 -5具有29 - 32%的同一性，与植物和细菌己糖转运蛋白具有32-36%的同一性。与GLUT 1 -5不同，GLUTX 1在跨膜结构域（TM）1和TM 2之间有一个短的细胞外环，在TM 9和TM 10之间有一个长的细胞外环，其中含有唯一的N-糖基化位点。当在非洲爪蟾卵母细胞中表达时，GLUTX 1仅在抑制氨基末端区域中存在的双亮氨酸内化基序后才表现出强的运输活性。细胞松弛素B抑制转运活性，D-果糖和D-半乳糖部分竞争转运活性。葡萄糖的Michaelis-Menten常数约为2 mM，当在网织红细胞裂解物中翻译时，GLUTX 1作为35-kDa蛋白迁移，在微粒体膜存在下糖基化，在HEK 293 T细胞中瞬时表达的GLUTX 1的蛋白质印迹分析揭示了分子量为37-50 kDa的弥散带，其可以转化为类似于35 - 50 kDa的蛋白质。酶促去糖基化后的kDa多肽。免疫荧光显微镜检测GLUTX 1转染HEK 293 T细胞显示细胞内染色。双亮氨酸内化基序的突变诱导GLUTX 1在细胞表面的表达，在睾丸、下丘脑、小脑、脑干、海马和肾上腺中检测到GLUTX 1 mRNA。我们假设，以与GLUT 4相似的方式，GLUTX 1在体内细胞表面的表达可能是由激素或其他刺激诱导的。
Based on homology with GLUT1-5, we have isolated a cDNA for a novel glucose transporter, GLUTX1. This cDNA encodes a protein of 478 amino acids that shows between 29 and 32% identity with rat GLUT1-5 and 32-36% identity with plant and bacterial hexose transporters. Unlike GLUT1-5, GLUTX1 has a short extracellular loop between transmembrane domain (TM) 1 and TM2 and a long extracellular loop between TM9 and TM10 that contains the only N-glycosylation site. When expressed in Xenopus oocytes, GLUTX1 showed strong transport activity only after suppression of a dileucine internalization motif present in the amino-terminal region. Transport activity was inhibited by cytochalasin B and partly competed by D-fructose and D-galactose. The Michaelis-Menten constant for glucose was approximately 2 mM, When translated in reticulocytes lysates, GLUTX1 migrates as a 35-kDa protein that becomes glycosylated in the presence of microsomal membranes, Western blot analysis of GLUTX1 transiently expressed in HEK293T cells revealed a diffuse band with a molecular mass of 37-50 kDa that could be converted to a similar to 35-kDa polypeptide following enzymatic deglycosylation. Immunofluorescence microscopy detection of GLUTX1 transfected into HEK293T cells showed an intracellular staining. Mutation of the dileucine internalization motif induced expression of GLUTX1 at the cell surface, GLUTX1 mRNA was detected in testis, hypothalamus, cerebellum, brainstem, hippocampus, and adrenal gland, We hypothesize that, in a similar fashion to GLUT4 in vivo cell surface expression of GLUTX1 may be inducible by a hormonal or other stimulus.