D'Amore T, Lo T C
Biochem Cell Biol. 1986 Nov;64(11):1081-91. doi: 10.1139/o86-143.
This review discusses some of the approaches and general criteria that we have used to examine the properties of the hexose transport system in undifferentiated L6 rat myoblasts. These approaches include studying the kinetics of hexose transport in whole cells and plasma membrane vesicles, the effects of various inhibitors on hexose transport, the isolation and characterization of hexose transport mutants, and the use of cytochalasin B (CB) to identify the transport component(s). Transport kinetics indicated that two transport systems are present in these cells. 2-Deoxy-D-glucose is transported primarily by the high affinity system, whereas 3-O-methyl-D-glucose is transported by the low affinity system. Furthermore, these two transport systems are inactivated to different extents by CB. CB has a higher binding affinity for the low affinity hexose transport system. The inhibitory effect of various hexose analogues also revealed the presence of two hexose transport systems. The effects of various ionophores and energy uncouplers on hexose transport suggest that the high affinity system is an active transport process, whereas the low affinity system is of the facilitated diffusion type. The high affinity system is also sensitive to sulfhydryl reagents, whereas the low affinity system is not. Further evidence for the presence of two transport systems comes from the characterization of hexose transport mutants. Two of the mutants isolated are shown to be defective in the high affinity transport system, but not in the low affinity transport system. These mutants are also defective in the CB low affinity binding site. Based on our results a tentative working model for hexose transport in L6 rat myoblasts is presented.
本综述讨论了我们用于研究未分化的L6大鼠成肌细胞中己糖转运系统特性的一些方法和一般标准。这些方法包括研究全细胞和质膜囊泡中己糖转运的动力学、各种抑制剂对己糖转运的影响、己糖转运突变体的分离和表征，以及使用细胞松弛素B（CB）来鉴定转运成分。转运动力学表明这些细胞中存在两种转运系统。2-脱氧-D-葡萄糖主要通过高亲和力系统转运，而3-O-甲基-D-葡萄糖通过低亲和力系统转运。此外，这两种转运系统被CB灭活的程度不同。CB对低亲和力己糖转运系统具有更高的结合亲和力。各种己糖类似物的抑制作用也揭示了两种己糖转运系统的存在。各种离子载体和能量解偶联剂对己糖转运的影响表明，高亲和力系统是一种主动转运过程，而低亲和力系统是易化扩散类型。高亲和力系统也对巯基试剂敏感，而低亲和力系统则不敏感。两种转运系统存在的进一步证据来自己糖转运突变体的表征。分离出的两个突变体在高亲和力转运系统中存在缺陷，但在低亲和力转运系统中没有缺陷。这些突变体在CB低亲和力结合位点也存在缺陷。基于我们的结果，提出了一个关于L6大鼠成肌细胞中己糖转运的初步工作模型。
