Hatakeyama Hiroyasu, Kobayashi Ko, Kanzaki Makoto
Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai 980-8579, Japan.
Graduate School of Biomedical Engineering, Tohoku University, Sendai 980-8579, Japan.
iScience. 2022 Mar 26;25(4):104164. doi: 10.1016/j.isci.2022.104164. eCollection 2022 Apr 15.
Quantitative features of GLUT4 glucose transporter's behavior deep inside cells remain largely unknown. Our previous analyses with live-cell imaging of intracellular GLUT4 trafficking demonstrated two crucial early events responsible for triggering insulin-responsive translocation processes, namely, heterotypic fusion and liberation. To quantify the regulation, interrelationships, and dynamics of the initial events more accurately and comprehensively, we herein applied three analyses, each based on our distinct dual-color live-cell imaging approaches. With these approaches, heterotypic fusion was found to be the first trigger for insulin-responsive GLUT4 redistributions, preceding liberation, and to be critically regulated by Akt substrate of 160 kDa (AS160) and actin dynamics. In addition, demonstrating the subcellular regional dependence of GLUT4 dynamics revealed that liberated GLUT4 molecules are promptly incorporated into the trafficking itinerary of transferrin receptors. Our approaches highlight the physiological significance of endosomal "GLUT4 molecule trafficking" rather than "GLUT4 vesicle delivery" to the plasma membrane in response to insulin.
细胞内部深处的葡萄糖转运蛋白4（GLUT4）的行为定量特征在很大程度上仍然未知。我们之前对细胞内GLUT4转运进行的活细胞成像分析表明，有两个关键的早期事件负责触发胰岛素反应性转位过程，即异型融合和释放。为了更准确、全面地量化这些初始事件的调控、相互关系和动态变化，我们在此应用了三种分析方法，每种方法都基于我们独特的双色活细胞成像方法。通过这些方法，我们发现异型融合是胰岛素反应性GLUT4重新分布的第一个触发因素，先于释放，并且受到160 kDa的Akt底物（AS160）和肌动蛋白动态变化的严格调控。此外，对GLUT4动态变化的亚细胞区域依赖性的研究表明，释放的GLUT4分子会迅速融入转铁蛋白受体的转运途径。我们的方法突出了内体“GLUT4分子转运”而非“GLUT4囊泡递送”对胰岛素反应性向质膜转运的生理意义。
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