Missense mutations in SGLT1 cause glucose-galactose malabsorption by trafficking defects
Missense mutations in SGLT1 cause glucose-galactose malabsorption by trafficking defects
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DOI：
10.1016/s0925-4439(98)00109-4
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发表时间：
1999-02-24
影响因子：
6.2
通讯作者：
Wright, EM
中科院分区：
文献类型：
--
作者：
Lam, JT;Martín, MG;Wright, EM
葡萄糖-半乳糖吸收不良（GGM）是一种由Na+/葡萄糖协同转运蛋白（SGLT 1）缺陷引起的常染色体隐性遗传疾病。新生儿在任何含葡萄糖和/或半乳糖的饮食中出现重度腹泻[1]。这项研究的重点是瑞士和多米尼加血统的患者。采用单链构象多态性分析筛选SGLT 1的所有15个外显子，并对异常PCR产物进行测序。发现两个错义突变，Gly 318 Arg和Ala 468 Val。SGLT 1突变体在非洲爪蟾卵母细胞中表达，用于放射性示踪剂摄取、电生理实验和Western印迹。突变体对[C-14] α-甲基-D-葡萄糖苷的摄取比野生型低5%或更低。双电极电压钳实验证实了转运缺陷，因为从两种突变体中均不能引起明显的糖诱导电流[2]。细胞蛋白质的Western印迹显示，每种SGLT 1突变蛋白的水平与野生型相当，并且两者都是核心糖基化的，Prestaady状态电流测量表明质膜中不存在SGLT 1。我们认为，复合杂合子错义突变G318 R和A468 V导致GGM在这个病人的缺陷贩运的突变蛋白质从内质网到质膜。(C)1999 Elsevier Science B. V.保留所有权利。
Glucose-galactose malabsorption (GGM) is an autosomal recessive disorder caused by defects in the Na+/glucose cotransporter (SGLT1). Neonates present with severe diarrhea while on any diet containing glucose and/or galactose [1]. This study focuses on a patient of Swiss and Dominican descent. All 15 exons of SGLT1 were screened using single stranded conformational polymorphism analyses, and aberrant PCR products were sequenced. Two missense mutations, Gly318Arg and Ala468Val, were identified. SGLT1 mutants were expressed in Xenopus laevis oocytes for radiotracer uptake, electrophysiological experiments, and Western blotting. Uptakes of [C-14]alpha-methyl-D-glucoside by the mutants were 5% or less than that of wild-type. Two-electrode voltage-clamp experiments confirmed the transport defects, as no noticeable sugar-induced current could be elicited from either mutant [2]. Western blots of cell protein showed levels of each SGLT1 mutant protein comparable to that of wild-type, and that both were core-glycosylated, Presteady-state current measurements indicated an absence of SGLT1 in the plasma membrane. We suggest that the compound heterozygote missense mutations G318R and A468V lead to GGM in this patient by defective trafficking of mutant proteins from the endoplasmic reticulum to the plasma membrane. (C) 1999 Elsevier Science B.V. All rights reserved.