Lange K, Brandt U
Institut für Pharmakologie, Freie Universität Berlin, FRG.
FEBS Lett. 1990 Feb 26;261(2):459-63. doi: 10.1016/0014-5793(90)80615-p.
The recently proposed mechanistic concept of a receptor-regulated entrance compartment for hexose transport formed by microvilli on 3T3-L1 adipocytes predicted a preferential localization of glucose transporters in these structures. The cytochalasin B-binding technique was used to determine in basal and insulin-stimulated cells the distribution of glucose transporters between plasma membranes, low density microsomes (LDM) and two cell surface-derived membrane fractions prepared by a hydrodynamic shearing technique. The shearing procedure applied prior to homogenization yielded a low density surface-derived vesicle (LDSV) fraction which contained nearly 60% of the cellular glucose transporters and the total insulin-sensitive transporter pool. The rest of the glucose transporter population was localized within the plasma membrane (5%) and the LDM fraction (37%). Pretreatment of the cells with insulin (20 mU/ml for 10 min) reduced the transporter content of the LDSV fraction by 40% and increased that of the plasma membrane fraction 4-fold. The transporter containing LDSV fraction was clearly differentiated from the LDM fraction by its low specific galactosyltransferase activity and its insulin-sensitivity. Scanning electron microscopy revealed that the LDSV fraction contained a rather uniform population of spherical vesicles of 100-200 nm in diameter.
最近提出的一种机制概念认为，3T3-L1脂肪细胞上的微绒毛形成了用于己糖转运的受体调节进入区室，这预测了葡萄糖转运蛋白在这些结构中的优先定位。使用细胞松弛素B结合技术来确定基础状态和胰岛素刺激状态下的细胞中，葡萄糖转运蛋白在质膜、低密度微粒体（LDM）以及通过流体动力学剪切技术制备的两个细胞表面衍生膜组分之间的分布。在匀浆前应用的剪切程序产生了一个低密度表面衍生囊泡（LDSV）组分，其包含近60%的细胞葡萄糖转运蛋白和全部胰岛素敏感转运蛋白池。其余的葡萄糖转运蛋白群体定位于质膜（5%）和LDM组分（37%）中。用胰岛素（20 mU/ml，处理10分钟）预处理细胞，使LDSV组分中的转运蛋白含量降低了40%，并使质膜组分中的转运蛋白含量增加了4倍。含有转运蛋白的LDSV组分通过其低特异性半乳糖基转移酶活性和胰岛素敏感性与LDM组分明显区分开来。扫描电子显微镜显示，LDSV组分包含直径为100 - 200 nm的相当均匀的球形囊泡群体。
