利用双荧光报告基因对活癌细胞中葡萄糖转运蛋白1(GLUT1)转运的可视化研究

Visualization of GLUT1 Trafficking in Live Cancer Cells by the Use of a Dual-Fluorescence Reporter.

作者信息

Li Zhen-Yan, Shi Yu-Ling, Liang Guo-Xiong, Yang Jie, Zhuang Song-Kuan, Lin Jie-Bin, Ghodbane Abdelmoumin, Tam Man-Seng, Liang Zu-Jian, Zha Zhen-Gang, Zhang Huan-Tian

机构信息

Institute of Orthopedic Diseases and Department of Bone and Joint Surgery, the First Affiliated Hospital, Jinan University, Guangzhou, Guangdong 510630, China.

Department of Orthopedics, the Third Affiliated Hospital, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong 510405, China.

出版信息

ACS Omega. 2020 Jun 23;5(26):15911-15921. doi: 10.1021/acsomega.0c01054. eCollection 2020 Jul 7.

Abstract

Glucose metabolism is an essential process for energy production and cell survival for both normal and abnormal cellular metabolism. Several glucose transporter/solute carrier 2A (GLUT/SLC2A) superfamily members, including glucose transporter 1 (GLUT1), have been shown to mediate the cellular uptake of glucose in diverse cell types. GLUT1-mediated glucose uptake is a transient and rapid process; thus, the real-time monitoring of GLUT1 trafficking is pivotal for a better understanding of GLUT1 expression and GLUT1-dependent glucose uptake. In the present study, we established a rapid and effective method to visualize the trafficking of GLUT1 between the plasma membrane (PM) and endolysosomal system in live cells using an mCherry-EGFP-GLUT1 tandem fluorescence tracing system. We found that GLUT1 localized at the PM exhibited both red (mCherry) and green (EGFP) fluorescence (yellow when overlapping). However, a significant increase in red punctate fluorescence (mCherry is resistant to acidic pH), but not green fluorescence (EGFP is quenched by acidic pH), was observed upon glucose deprivation, indicating that the mCherry-EGFP-GLUT1 functional protein was trafficked to the acidic endolysosomal system. Besides, we were able to calculate the relative ratio of mCherry to EGFP by quantification of the translocation coefficient, which can be used as a readout for GLUT1 internalization and subsequent lysosomal degradation. Two mutants, mCherry-EGFP-GLUT1-S226D and mCherry-EGFP-GLUT1-ΔC4, were also constructed, which indirectly confirmed the specificity of mCherry-EGFP-GLUT1 for monitoring GLUT1 trafficking. By using a series of endosomal (Rab5, Rab7, and Rab11) and lysosomal markers, we were able to define a model of GLUT1 trafficking in live cells in which upon glucose deprivation, GLUT1 dissociates from the PM and experiences a pH gradient from 6.8-6.1 in the early endosomes to 6.0-4.8 in the late endosomes and finally pH 4.5 in lysosomes, which is appropriate for degradation. In addition, our proof-of-concept study indicated that the pmCherry-EGFP-GLUT1 tracing system can accurately reflect endogenous changes in GLUT1 in response to treatment with the small molecule, andrographolide. Since targeting GLUT1 expression and GLUT1-dependent glucose metabolism is a promising therapeutic strategy for diverse types of cancers and certain other glucose addiction diseases, our study herein indicates that pmCherry-EGFP-GLUT1 can be utilized as a biosensor for GLUT1-dependent functional studies and potential small molecule screening.

摘要

葡萄糖代谢是正常和异常细胞代谢中能量产生和细胞存活的重要过程。包括葡萄糖转运蛋白1(GLUT1)在内的几种葡萄糖转运蛋白/溶质载体2A(GLUT/SLC2A)超家族成员已被证明可介导多种细胞类型对葡萄糖的摄取。GLUT1介导的葡萄糖摄取是一个短暂而快速的过程;因此,实时监测GLUT1的转运对于更好地理解GLUT1的表达和GLUT1依赖性葡萄糖摄取至关重要。在本研究中,我们建立了一种快速有效的方法,使用mCherry-EGFP-GLUT1串联荧光追踪系统在活细胞中可视化GLUT1在质膜(PM)和内溶酶体系统之间的转运。我们发现定位于PM的GLUT1同时呈现红色(mCherry)和绿色(EGFP)荧光(重叠时为黄色)。然而,在葡萄糖剥夺后,观察到红色点状荧光显著增加(mCherry对酸性pH具有抗性),而绿色荧光没有增加(EGFP在酸性pH下被淬灭),这表明mCherry-EGFP-GLUT1功能蛋白被转运到酸性内溶酶体系统。此外,我们能够通过量化转运系数来计算mCherry与EGFP的相对比率,该系数可作为GLUT1内化和随后溶酶体降解的读数。我们还构建了两个突变体,mCherry-EGFP-GLUT1-S226D和mCherry-EGFP-GLUT1-ΔC4,间接证实了mCherry-EGFP-GLUT1用于监测GLUT1转运的特异性。通过使用一系列内体(Rab5、Rab7和Rab11)和溶酶体标记物,我们能够定义活细胞中GLUT1转运的模型,即在葡萄糖剥夺后,GLUT1从PM解离,并经历从早期内体中的pH 6.8 - 6.1到晚期内体中的pH 6.0 - 4.8,最终到溶酶体中的pH 4.5的pH梯度,这适合于降解。此外我们的概念验证研究表明,pmCherry-EGFP-GLUT1追踪系统可以准确反映小分子穿心莲内酯处理后GLUT1的内源性变化。由于靶向GLUT1表达和GLUT1依赖性葡萄糖代谢是多种癌症和某些其他葡萄糖成瘾性疾病的一种有前景的治疗策略,我们在本文中的研究表明,pmCherry-EGFP-GLUT1可作为一种生物传感器用于GLUT1依赖性功能研究和潜在小分子筛选。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/6b60/7345384/e8729265b6e9/ao0c01054_0001.jpg

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