Eisenberg Michael L, Maker Ajay V, Slezak Lori A, Nathan Jaimie D, Sritharan Kumudesh C, Jena Bhanu P, Geibel John P, Andersen Dana K
Department of Surgery, Yale University School of Medicine, USA.
Cell Physiol Biochem. 2005;15(1-4):51-8. doi: 10.1159/000083638.
The hepatic glucose transporter, GLUT2, facilitates bidirectional glucose transport across the hepatocyte plasma membrane under insulin regulation. We studied the interactions of IR and GLUT2 proteins to determine whether they are physically coupled in a receptor-transporter complex. By comparing endosome and plasma membrane IR and GLUT2 ratios before and after feeding, it was determined that IR and GLUT2 are internalized in a fixed ratio. When solubilized hepatocytes were immunoprecipitated with antibodies against either IR or GLUT2, both proteins co-precipitated. The association of IR and GLUT2 was further assessed by confocal microscopy. Sections of fed liver were incubated with fluorescein-tagged anti-GLUT2 or Texas Red-tagged anti-IR. Colocalization was observed both at the plasma membrane and in the cytosol. Fluorescence-resonance energy transfer studies further confirmed this association. We conclude that IR and GLUT2 form a receptor-transporter complex in hepatocytes, which forms a mechanism of insulin-mediated hepatic glucose regulation.
肝脏葡萄糖转运蛋白GLUT2在胰岛素调节下促进葡萄糖双向跨肝细胞质膜转运。我们研究了胰岛素受体（IR）与GLUT2蛋白之间的相互作用，以确定它们是否在受体-转运体复合物中存在物理偶联。通过比较喂食前后内体和质膜中IR与GLUT2的比例，确定IR和GLUT2以固定比例内化。当用抗IR或抗GLUT2抗体对溶解的肝细胞进行免疫沉淀时，两种蛋白都能共沉淀。通过共聚焦显微镜进一步评估IR与GLUT2的关联。用荧光素标记的抗GLUT2或德克萨斯红标记的抗IR孵育喂食后肝脏的切片。在质膜和细胞质中均观察到共定位。荧光共振能量转移研究进一步证实了这种关联。我们得出结论，IR和GLUT2在肝细胞中形成受体-转运体复合物，这构成了胰岛素介导的肝脏葡萄糖调节机制。
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