Brant A M, Martin S, Gould G W
Division of Biochemistry, University of Glasgow, Scotland, U.K.
Biochem J. 1994 Nov 15;304 ( Pt 1)(Pt 1):307-11. doi: 10.1042/bj3040307.
We have expressed the liver-type facilitative glucose transporter, GLUT2, in the insulin-sensitive 3T3-L1 adipocyte clonal cell line in an effort to address the importance of transporter isoform and cellular environment on the ability of insulin to mediate glucose-transporter translocation. Analysis of non-differentiated fibroblastic cell clones transfected with the GLUT2 cDNA identified the presence of this isoform in several independent clones. These clones exhibited increased deoxyglucose and fructose transport rates compared with control cells. Upon differentiation, the fibroblastic clones selected for study achieved > 95% phenotypic conversion into adipocytes. Expression of the GLUT2 protein was maintained throughout the differentiation protocol. Subcellular fractionation revealed that in response to insulin, unlike the native GLUT4, GLUT2 protein did not undergo significant translocation to the plasma membrane; furthermore, the subcellular distribution of the expressed GLUT2 was quite distinct from that of the endogenous GLUT4. 3T3-L1 adipocytes expressing GLUT2 only exhibited a 2-fold increase in insulin-stimulated fructose uptake, further suggesting that GLUT2 does not undergo insulin-stimulated translocation.
我们已在胰岛素敏感的3T3-L1脂肪细胞克隆细胞系中表达了肝型易化葡萄糖转运体GLUT2，以探讨转运体异构体和细胞环境对胰岛素介导葡萄糖转运体转位能力的重要性。对用GLUT2 cDNA转染的未分化成纤维细胞克隆进行分析，在几个独立克隆中鉴定出了这种异构体的存在。与对照细胞相比，这些克隆表现出脱氧葡萄糖和果糖转运速率增加。分化后，选择用于研究的成纤维细胞克隆实现了>95%向脂肪细胞的表型转化。在整个分化过程中，GLUT2蛋白的表达得以维持。亚细胞分级分离显示，与天然的GLUT4不同，响应胰岛素时，GLUT2蛋白不会发生显著的向质膜转位；此外，所表达的GLUT2的亚细胞分布与内源性GLUT4的亚细胞分布截然不同。仅表达GLUT2的3T3-L1脂肪细胞在胰岛素刺激的果糖摄取方面仅增加了2倍，进一步表明GLUT2不会发生胰岛素刺激的转位。
