Subcellular localization of hexokinases I and II directs the metabolic fate of glucose.
Subcellular localization of hexokinases I and II directs the metabolic fate of glucose.
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己二酶I和II的亚细胞定位指导葡萄糖的代谢命运。
DOI：
10.1371/journal.pone.0017674
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发表时间：
2011-03-09
期刊：
影响因子：
3.7
通讯作者：
Ribalet B
中科院分区：
文献类型：
--
作者：
John S;Weiss JN;Ribalet B
葡萄糖代谢的第一步是己糖激酶族(HKS)将葡萄糖转化为葡萄糖6-磷酸(G-6-P)，该家族有4种异构体。最常见的两种亚型HKI和HKII有重叠的组织表达，但亚细胞分布不同，HKI主要与线粒体相关，HKII与线粒体和细胞质隔室都相关。在这里，我们验证了这样的假设：这些不同的亚细胞分布与不同的代谢作用有关，线粒体结合的HK将G-6-P导向糖酵解(分解代谢使用)，胞浆HKII调节糖原形成(合成代谢使用)。为了研究HKS在活细胞中的亚细胞转位，我们在CHO细胞中表达了与YFP相连的HKI和HKII。我们同时使用基于FRET的细胞内葡萄糖生物传感器FLIPglu-600 mm记录了葡萄糖处理的影响，并使用GFP标记的糖原相关蛋白PTG记录了糖原形成的影响。我们的结果表明，HKI仍然强烈地与线粒体结合，而HKII对葡萄糖、G-6-P和Akt的反应是在线粒体和胞浆之间移位，而不是对ATP的反应。代谢测量表明，HKI只促进糖酵解，而HKII具有更复杂的作用，当与线粒体结合时促进糖酵解，当位于胞浆中时促进糖原合成。去除葡萄糖后糖原的分解导致HKII抑制和线粒体解离，这可能是由糖原衍生的G-6-P增加所介导的。这些发现表明，葡萄糖的分解代谢与合成代谢的命运是由细胞外葡萄糖通过细胞内葡萄糖、G-6-P和Akt等信号分子通过调节和亚细胞内转位来动态调节的。相比之下，HKI的活动和调控对这些因素的敏感性要低得多，主要致力于糖酵解。这可能是HK允许细胞适应不断变化的代谢条件以维持能量平衡和避免损伤的重要机制。
The first step in glucose metabolism is conversion of glucose to glucose 6-phosphate (G-6-P) by hexokinases (HKs), a family with 4 isoforms. The two most common isoforms, HKI and HKII, have overlapping tissue expression, but different subcellular distributions, with HKI associated mainly with mitochondria and HKII associated with both mitochondrial and cytoplasmic compartments. Here we tested the hypothesis that these different subcellular distributions are associated with different metabolic roles, with mitochondrially-bound HK's channeling G-6-P towards glycolysis (catabolic use), and cytoplasmic HKII regulating glycogen formation (anabolic use). To study subcellular translocation of HKs in living cells, we expressed HKI and HKII linked to YFP in CHO cells. We concomitantly recorded the effects on glucose handling using the FRET based intracellular glucose biosensor, FLIPglu-600 mM, and glycogen formation using a glycogen-associated protein, PTG, tagged with GFP. Our results demonstrate that HKI remains strongly bound to mitochondria, whereas HKII translocates between mitochondria and the cytosol in response to glucose, G-6-P and Akt, but not ATP. Metabolic measurements suggest that HKI exclusively promotes glycolysis, whereas HKII has a more complex role, promoting glycolysis when bound to mitochondria and glycogen synthesis when located in the cytosol. Glycogen breakdown upon glucose removal leads to HKII inhibition and dissociation from mitochondria, probably mediated by increases in glycogen-derived G-6-P. These findings show that the catabolic versus anabolic fate of glucose is dynamically regulated by extracellular glucose via signaling molecules such as intracellular glucose, G-6-P and Akt through regulation and subcellular translocation of HKII. In contrast, HKI, which activity and regulation is much less sensitive to these factors, is mainly committed to glycolysis. This may be an important mechanism by which HK's allow cells to adapt to changing metabolic conditions to maintain energy balance and avoid injury.