Biochemical and functional characterization of the rat liver glucose-transport system. Comparisons with the adipocyte glucose-transport system.
Biochemical and functional characterization of the rat liver glucose-transport system. Comparisons with the adipocyte glucose-transport system.
复制标题
大鼠肝脏葡萄糖转运系统的生化和功能特征。
DOI：
10.1042/bj2400115
复制
发表时间：
1986
期刊：
影响因子：
--
通讯作者：
Matthaei,S
中科院分区：
文献类型：
--
作者：
Ciaraldi,TP;Horuk,R;Matthaei,S
在从相同动物制备的细胞中比较了大鼠脂肪细胞和肝细胞中葡萄糖转运系统的性质。在脂肪细胞中引起3-O-甲基葡萄糖转运大刺激的激素和其他药物在肝细胞中没有急性效应。肝细胞显示出较低的亲和力3-O-甲基葡萄糖（20 mM）和替代底物比脂肪细胞（6 mM），而抑制剂的亲和力在两种细胞类型是相似的。葡萄糖转运蛋白的浓度和分布通过结合至亚细胞组分的D-葡萄糖可降解[3 H]细胞松弛素B的Scatchard分析来确定。在肝脏中，大多数转运蛋白位于质膜（42 +/- 5 pmol/mg蛋白）中，少量（4 +/- 3 pmol/mg）位于低密度微粒体部分（“微粒体”）中，与脂肪细胞中的情况相反。用光化学交联剂羟基琥珀酰亚胺基-4-叠氮苯甲酸酯共价标记[3 H]细胞松弛素B，并用SDS/聚丙烯酰胺凝胶电泳分析葡萄糖转运蛋白。在质膜和低密度微粒体中均观察到分子量为40-50 kDa的单一D-葡萄糖可降解峰。通过等电聚焦进一步表征了该峰，并显示低密度微粒体和质膜中pI 6.05处特异性[3 H]细胞松弛素B结合的单一峰，而脂肪细胞膜中pI 6.4和5.6处的峰。总的来说：肝细胞中的葡萄糖转运系统比脂肪细胞中的葡萄糖转运系统具有更低的亲和力和更高的能力，并且也不被胰岛素精确地调节;葡萄糖转运蛋白在肝脏中的亚细胞分布表明很少有细胞内转运蛋白可用于易位;肝脏转运蛋白的分子量与脂肪细胞转运蛋白的分子量相似;与脂肪细胞中的多种形式相比，肝脏葡萄糖转运蛋白以单电荷形式（pI 6.05）存在。这种电荷的差异可能反映了两种细胞类型之间分子结构的重要功能差异。
The properties of the glucose-transport systems in rat adipocytes and hepatocytes were compared in cells prepared from the same animals. Hormones and other agents which cause a large stimulation of 3-O-methylglucose transport in adipocytes were without acute effect in hepatocytes. Hepatocytes displayed a lower affinity for 3-O-methylglucose (20 mM) and alternative substrates than adipocytes (6 mM), whereas inhibitor affinities were similar in both cell types. The concentration and distribution of glucose transporters were determined by Scatchard analysis of D-glucose-inhibitable [3H]cytochalasin B binding to subcellular fractions. In liver, most of the transporters were located in the plasma membrane (42 +/- 5 pmol/mg of protein) with a small amount (4 +/- 3 pmol/mg) in the low-density microsomal fraction (‘microsomes’), the reverse of the situation in adipocytes. Glucose transporters were covalently labelled with [3H]cytochalasin B by using the photochemical cross-linking agent hydroxysuccinimidyl-4-azidobenzoate and analysed by SDS/polyacrylamide-gel electrophoresis. A single D-glucose-inhibitable peak with a molecular mass of 40-50 kDa was seen in both plasma membrane and low-density microsomes. This peak was further characterized by isoelectric focusing and revealed a single peak of specific [3H]cytochalasin B binding at pI 6.05 in both low-density microsomes and plasma membrane, compared with peaks at pI 6.4 and 5.6 in adipocyte membranes. In summary: the glucose-transport system in hepatocytes has a lower affinity and higher capacity than that in adipocytes, and is also not accurately modulated by insulin; the subcellular distribution of glucose transporters in the liver suggests that few intracellular transporters would be available for translocation; the liver transporter has a molecular mass similar to that of the adipocyte transporter; the liver glucose transporter exists as a single charged form (pI 6.05), compared with the multiple forms in adipocytes. This difference in charge could reflect a functionally important difference in molecular structure between the two cell types.