PGK1在糖酵解与线粒体功能协作中的机制研究

Phosphoglycerate kinase-1 (PGK1) is an instrumental ATP-generating glycolytic enzyme in the glycolytic pathway that is overexpressed in many types of human cancer. However, its role in tumorigenesis is unclear, as is whether it has other important cellular functions besides its well-established regulation in glycolysis. Our preliminary data revealed that hypoxia stimulation induced translocation of PGK1 to mitochondria. Importantly, mitochondrial PGK1 functions as a protein kinase and phosphorylates pyruvate dehydrogenase kinase 1 (PDK1). In addition, PGK1 depletion inhibits PDK1-regulated mitochondrial pyruvate metabolism and brain tumor growth in mice. We hypothesize that PGK1 coordinately regulates glycolysis and mitochondrial metabolism through its subcellular compartment function. To test this hypothesis, we will pursue three specific aims: (1) To determine the mechanisms that underlie hypoxia-induced mitochondrial PGK1 translocation; (2) to determine the mechanisms that underlie PGK1-regulated PDH inhibition; and (3) to differentiate the functions of cytosolic and mitochondrial PGK1 and determine the role of PDK1/PDH regulation by PGK1 in brain tumor development. The proposed research is significant because it could lead to pharmaceutical approaches to interrupt cancer metabolism by blocking the dual functions of PGK1 as a glycolytic enzyme and protein kinase; this would, in turn, improve the efficacy of human cancer treatment.

PGK1是糖酵解途径中重要的ATP产生酶，在多种肿瘤中高表达。除了在糖酵解途径中的作用外，PGK1是否还有其它细胞功能及其在肿瘤形成中的作用尚不清楚。我们前期研究表明，低氧诱导PGK1发生线粒体易位。重要的是，线粒体PGK1可以作为蛋白激酶磷酸化丙酮酸脱氢酶激酶1（PDK1）。PGK1敲减抑制了PDK1调节的线粒体丙酮酸代谢和小鼠脑肿瘤生长。因此，我们提出假说：不同亚细胞区域的PGK1协作糖酵解和线粒体代谢功能。要验证这一假说，我们将完成以下三个目标：（1）明确低氧诱导PGK1线粒体易位的机制；（2）明确PGK1调控PDH活性的机制；（3）区分胞浆PGK1和线粒体PGK1的细胞功能，并明确PGK1调控PDK1/PDH在脑肿瘤形成中的作用。该项目的重要意义在于为药物研发提供了理论依据，可以通过阻断PGK1的糖酵解活性和激酶活性干扰肿瘤代谢，从而有助于肿瘤治疗。

目前尚不清楚沃伯格效应是如何例证细胞质中的增强的糖酵解与线粒体丙酮酸的代谢抑制之间的协调作用。我们在这里证明缺氧，EGFR激活， K-Ras G12V和B-Raf V600E的表达诱导磷酸甘油酸激酶1的线粒体易位（PGK1）,这是通过ERK依赖的PGK1 S203磷酸化以及PIN1介导的顺反异构化。线粒体PGK1充当蛋白激酶使丙酮酸脱氢酶激酶1(PDHK1）在T338位点磷酸化，该位点激活使PDHK1磷酸化并抑制丙酮酸脱氢酶（PDH）复合体。这减少了线粒体丙酮酸利用，抑制活性氧的产生，增加乳酸的产生，并促进脑肿瘤发生。此外，PGK1 S203和PDHK1 T338磷酸化水平与PDH S293磷酸化失活水平和胶质母细胞瘤患者的不良预后相关。这项工作强调PGK1可以作为蛋白激酶协调糖酵解和三羧酸（TCA）循环，这一功能有助于癌症的代谢和肿瘤发生。