Biochemistry Department G Moruzzi, Alma Mater Studiorum-University of Bologna, Bologna, Italy.
PLoS One. 2012;7(7):e41246. doi: 10.1371/journal.pone.0041246. Epub 2012 Jul 30.
GLUT1 is the predominant glucose transporter in leukemia cells, and the modulation of glucose transport activity by cytokines, oncogenes or metabolic stresses is essential for their survival and proliferation. However, the molecular mechanisms allowing to control GLUT1 trafficking and degradation are still under debate. In this study we investigated whether plasma membrane cholesterol depletion plays a role in glucose transport activity in M07e cells, a human megakaryocytic leukemia line. To this purpose, the effect of cholesterol depletion by methyl-β-cyclodextrin (MBCD) on both GLUT1 activity and trafficking was compared to that of the cytokine Stem Cell Factor (SCF). Results show that, like SCF, MBCD led to an increased glucose transport rate and caused a subcellular redistribution of GLUT1, recruiting intracellular transporter molecules to the plasma membrane. Due to the role of caveolae/lipid rafts in GLUT1 stimulation in response to many stimuli, we have also investigated the GLUT1 distribution along the fractions obtained after non ionic detergent treatment and density gradient centrifugation, which was only slightly changed upon MBCD treatment. The data suggest that MBCD exerts its action via a cholesterol-dependent mechanism that ultimately results in augmented GLUT1 translocation. Moreover, cholesterol depletion triggers GLUT1 translocation without the involvement of c-kit signalling pathway, in fact MBCD effect does not involve Akt and PLCγ phosphorylation. These data, together with the observation that the combined MBCD/SCF cell treatment caused an additive effect on glucose uptake, suggest that the action of SCF and MBCD may proceed through two distinct mechanisms, the former following a signalling pathway, and the latter possibly involving a novel cholesterol dependent mechanism.
GLUT1 是白血病细胞中主要的葡萄糖转运体，细胞因子、癌基因或代谢应激对葡萄糖转运活性的调节对于它们的存活和增殖至关重要。然而，控制 GLUT1 运输和降解的分子机制仍存在争议。在这项研究中，我们研究了胆固醇耗竭是否在人类巨核细胞白血病细胞系 M07e 中的葡萄糖转运活性中起作用。为此，将胆固醇耗竭（通过甲基-β-环糊精，MBCD）对 GLUT1 活性和运输的影响与细胞因子干细胞因子（SCF）的影响进行了比较。结果表明，与 SCF 一样，MBCD 导致葡萄糖转运率增加，并导致 GLUT1 亚细胞重新分布，将细胞内转运分子募集到质膜。由于 caveolae/脂筏在许多刺激物刺激 GLUT1 中的作用，我们还研究了 GLUT1 在非离子去污剂处理和密度梯度离心后获得的级分中的分布，MBCD 处理后仅略有变化。数据表明，MBCD 通过依赖胆固醇的机制发挥作用，最终导致 GLUT1 易位增加。此外，胆固醇耗竭触发 GLUT1 易位而不涉及 c-kit 信号通路，因为事实上 MBCD 效应不涉及 Akt 和 PLCγ 磷酸化。这些数据，加上观察到 MBCD/SCF 细胞联合处理对葡萄糖摄取有相加作用，表明 SCF 和 MBCD 的作用可能通过两种不同的机制进行，前者遵循信号通路，后者可能涉及新的胆固醇依赖机制。
