Koshy Shyny, Alizadeh Parema, Timchenko Lubov T, Beeton Christine
Department of Molecular Physiology and Biophysics, Baylor College of Medicine, USA.
J Vis Exp. 2010 Nov 7(45):2429. doi: 10.3791/2429.
Glucose is the main source of energy for the body, requiring constant regulation of its blood concentration. Insulin release by the pancreas induces glucose uptake by insulin-sensitive tissues, most notably the brain, skeletal muscle, and adipocytes. Patients suffering from type-2 diabetes and/or obesity often develop insulin resistance and are unable to control their glucose homeostasis. New insights into the mechanisms of insulin resistance may provide new treatment strategies for type-2 diabetes. The GLUT family of glucose transporters consists of thirteen members distributed on different tissues throughout the body. Glucose transporter type 4 (GLUT4) is the major transporter that mediates glucose uptake by insulin sensitive tissues, such as the skeletal muscle. Upon binding of insulin to its receptor, vesicles containing GLUT4 translocate from the cytoplasm to the plasma membrane, inducing glucose uptake. Reduced GLUT4 translocation is one of the causes of insulin resistance in type-2 diabetes. The translocation of GLUT4 from the cytoplasm to the plasma membrane can be visualized by immunocytochemistry, using fluorophore-conjugated GLUT4-specific antibodies. Here, we describe a technique to quantify total amounts of GLUT4 translocation to the plasma membrane of cells during a chosen duration, using flow cytometry. This protocol is rapid (less than 4 hours, including incubation with insulin) and allows the analysis of as few as 3,000 cells or as many as 1 million cells per condition in a single experiment. It relies on anti-GLUT4 antibodies directed to an external epitope of the transporter that bind to it as soon as it is exposed to the extracellular medium after translocation to the plasma membrane.
葡萄糖是身体的主要能量来源,需要对其血液浓度进行持续调节。胰腺释放的胰岛素促使胰岛素敏感组织摄取葡萄糖,其中最主要的是大脑、骨骼肌和脂肪细胞。患有2型糖尿病和/或肥胖症的患者常常会出现胰岛素抵抗,无法控制自身的葡萄糖稳态。对胰岛素抵抗机制的新见解可能为2型糖尿病提供新的治疗策略。葡萄糖转运蛋白GLUT家族由13个成员组成,分布于全身不同组织。葡萄糖转运蛋白4(GLUT4)是介导胰岛素敏感组织(如骨骼肌)摄取葡萄糖的主要转运蛋白。胰岛素与其受体结合后,含有GLUT4的囊泡从细胞质转运至质膜,从而促使葡萄糖摄取。GLUT4转运减少是2型糖尿病胰岛素抵抗的原因之一。利用荧光团偶联的GLUT4特异性抗体通过免疫细胞化学方法可观察到GLUT4从细胞质向质膜的转运。在此,我们描述一种使用流式细胞术在选定时间段内定量细胞中GLUT4向质膜转运总量的技术。该方案快速(少于4小时,包括与胰岛素孵育),且在一次实验中每种条件下可分析少至3000个细胞或多至100万个细胞。它依赖于针对转运蛋白外部表位的抗GLUT4抗体,该抗体在转运至质膜后一旦暴露于细胞外介质就会与之结合。