Department of Molecular Biology, School of Osteopathic Medicine, University of Medicine and Dentistry of New Jersey, Stratford, New Jersey 08084, USA.
J Cell Physiol. 2013 Sep;228(9):1943-8. doi: 10.1002/jcp.24361.
Hexokinase II (HK2), the enzyme that catalyzes the first committed step of glycolysis, is overexpressed in many cancers, as is the central signaling kinase Akt. Akt activity promotes HK2 association with the mitochondria, as well as glucose uptake by cancer cells. In HeLa cervical cancer cells, Akt inhibitor IV (Ai4) increased nuclear HK2 localization, while in MDA-MB-231 breast cancer cells, Ai4 merely induced cytoplasmic redistribution without increased nuclear accumulation. Small interfering RNA (siRNA) directed against Akt confirmed the effect in HeLa cells. Next, we treated the cells with clotrimazole (CTZ), which detaches HK2 from the mitochondria, or leptomycin B (LMB), which promotes HK2 nuclear accumulation, and determined the effect on HK2 subcellular distribution. In both cell lines, CTZ detached HK2 from the mitochondria, without substantially increasing nuclear HK2, while LMB increased nuclear HK2, without redistributing cytoplasmic HK2. Contrary to expectations, Akt inhibition promoted glucose uptake in both cell lines, suggesting that Akt inhibition may increase glucose uptake by detaching HK2 from the mitochondria. In both cell lines, CTZ and LMB increased glucose uptake. However, the results in the HeLa cells showed greater effects: CTZ increased glucose uptake to a similar degree to Ai4, while LMB was far more effective than either. These data suggest that both detachment of HK2 from the mitochondria and increased nuclear HK2 are important for Ai4-induced increased glucose uptake.
己糖激酶 II（HK2）是糖酵解第一步的关键酶，在许多癌症中过度表达，中央信号激酶 Akt 也是如此。Akt 的活性促进 HK2 与线粒体的结合，以及癌细胞对葡萄糖的摄取。在宫颈癌 HeLa 细胞中，Akt 抑制剂 IV（Ai4）增加了核 HK2 的定位，而在 MDA-MB-231 乳腺癌细胞中，Ai4 只是诱导细胞质重新分布，而没有增加核积累。针对 Akt 的小干扰 RNA（siRNA）在 HeLa 细胞中证实了这种作用。接下来，我们用克霉唑（CTZ）处理细胞，CTZ 将 HK2 从线粒体上分离，或用莱普霉素 B（LMB）处理细胞，LMB 促进 HK2 核积累，并确定对 HK2 亚细胞分布的影响。在这两种细胞系中，CTZ 将 HK2 从线粒体上分离，而不会显著增加核内 HK2，而 LMB 增加核内 HK2，而不会重新分布细胞质内的 HK2。出乎意料的是，Akt 抑制在两种细胞系中都促进了葡萄糖摄取，这表明 Akt 抑制可能通过将 HK2 从线粒体上分离来增加葡萄糖摄取。在这两种细胞系中，CTZ 和 LMB 都增加了葡萄糖摄取。然而，HeLa 细胞中的结果显示出更大的效果：CTZ 增加葡萄糖摄取的程度与 Ai4 相似，而 LMB 比 Ai4 更有效。这些数据表明，HK2 从线粒体上的分离和核内 HK2 的增加对于 Ai4 诱导的葡萄糖摄取增加都是重要的。
