Hediger M A, Ikeda T, Coady M, Gundersen C B, Wright E M
Proc Natl Acad Sci U S A. 1987 May;84(9):2634-7. doi: 10.1073/pnas.84.9.2634.
The expression of the rabbit intestinal brushborder Na/glucose cotransporter has been studied in Xenopus oocytes. Poly(A)+ RNA isolated from the intestinal mucosa was injected into oocytes, and the expression of the transporter in the oocyte plasma membrane was assayed by measuring the Na-dependent phlorizin-sensitive uptake of methyl alpha-D-[14C]glucopyranoside (MeGlc). Expression of the glucose carrier was detected 3-7 days after mRNA injection, and the rate of glucose transport was proportional to the amount of mRNA injected. mRNA (50 ng) increased the maximum velocity (Vmax) of MeGlc uptake by as much as 10-fold over background. The total mRNA was fractionated by preparative agarose gel electrophoresis and each fraction was assayed for its ability to induce transport activity. The mRNA encoding the Na/glucose cotransporter was found in a single fraction of approximately 2.3 kilobases (kb), which contained 3% of the total mRNA. A similar mRNA fraction (2.0-2.6 kb) isolated from colon did not induce expression of this transporter. In vitro translation of the fractionated intestinal mRNA showed enhanced synthesis of two protein bands at 57 and 63 kDa. The mRNA encoding the cotransporter is smaller (2.3 kb) than that (2.6-2.9 kb) encoding the 55-kDa facilitated glucose carrier in human hepatoma cells and rat brain.
已在非洲爪蟾卵母细胞中研究了兔肠刷状缘钠/葡萄糖共转运蛋白的表达。从肠黏膜分离的聚腺苷酸（poly(A)+）RNA被注射到卵母细胞中，通过测量α-D-[14C]吡喃葡萄糖苷（MeGlc）的钠依赖性根皮苷敏感摄取来检测卵母细胞质膜中共转运蛋白的表达。在mRNA注射后3至7天检测到葡萄糖载体的表达，并且葡萄糖转运速率与注射的mRNA量成比例。50 ng的mRNA使MeGlc摄取的最大速度（Vmax）比背景提高了多达10倍。通过制备性琼脂糖凝胶电泳对总mRNA进行分级分离，并对每个级分诱导转运活性的能力进行检测。编码钠/葡萄糖共转运蛋白的mRNA存在于一个约2.3千碱基（kb）的单一级分中，该级分占总mRNA的3%。从结肠分离的类似mRNA级分（2.0 - 2.6 kb）未诱导该共转运蛋白的表达。分级分离的肠mRNA的体外翻译显示在57和63 kDa处有两条蛋白带的合成增强。编码共转运蛋白的mRNA（2.3 kb）比人肝癌细胞和大鼠脑中编码55 kDa易化葡萄糖载体的mRNA（2.6 - 2.9 kb）小。
