基于细胞器的AMPK的区域化调控与代谢稳态调控

The cellular organelles play vital roles in cellular metabolic regulation, mediating a wide variety of metabolic processes. It has been increasingly appreciated that organelles intimately crosstalk with each other. However, the molecular mechanisms underlying their responses to intracellular or extracellular metabolic stresses remain obscure. AMPK is a master regulator of metabolic homeostasis; it is activated after phosphorylated by LKB1, in addition to others, when cellular energy is decreased or in response to deprivation of nutrients such as glucose. We have found that AXIN is the scaffold for bridging LKB1 to AMPK inside the cell (Cell Metabolism, 2013), and that AMPK is activated on the surface of lysosomes in response to decreased glucose levels through the lysosomal pathway (Cell Metabolism, 2014, 2016). We have also found that the lysosomal AMPK pathway is to sense glucose in addition to its canonical role in energy sensing (Nature, 2017). Our further studies, i.e. preliminary results for this proposal, showed that a family of cation channels located on the ER surface regulates lysosomal AMPK activation at ER-lysosome contact sites, and that the lysosomally activated AMPK is able to phosphorylate ER-localized SREBP1, a critical regulator of cholesterol synthesis, suggesting that there is a major cross-talk between the lysosome and ER in mediating AMPK activation in response to lowered glucose. In addition, we have obtained new data that indicate different pools of AMPK modulate differently compartmentalized substrates in response to different severities of nutrient/energy stresses or mitochondria-damaging drugs. Detailed characterization of which would provide a comprehensive understanding of distinct roles of AMPK in maintaining metabolic homeostasis under different challenges. In this proposal, we aim to further explore the molecular mechanisms for AMPK activation in the glucose sensing process, and elucidate how the compartmentalized AMPK pools regulate distinct substrates distributed among different organelles such as ER, lysosomes and mitochondria. This study will also help identify novel target for the prevention and treatment of metabolic diseases.

细胞器在细胞代谢中起重要作用，并通过彼此的相互作用介导了众多的代谢过程。然而，它们如何响应胞内胞外的各种应激状态并维持代谢稳态还尚未清楚。我们之前发现了AMPK——一种在维持代谢稳态中至关重要的激酶——在葡萄糖水平下降时的激活是在溶酶体表面进行的，还发现这一过程的溶酶体路径即是葡萄糖感知通路。进一步的研究（前期工作）表明，AMPK的激活事实上发生在内质网-溶酶体接触区域内，且需要内质网上的阳离子通道的参与，以及激活的AMPK能够抑制内质网上相关的胆固醇合成，这表明溶酶体与内质网通过相互作用维持代谢平衡。我们还发现，不同物质或能量的应激状态能够引起不同细胞器定位的AMPK的激活，相应地调节定位在不同细胞器上的底物。本项目拟深入阐明内质网、溶酶体、线粒体等细胞器及其互作在感受葡萄糖水平及其他应激中维持代谢稳态的分子机制和生理意义，为预防和治疗代谢性疾病提供重要的线索和依据。

细胞器在细胞代谢中起重要作用，并通过彼此的相互作用介导了众多的代谢过程。然而，它们如何响应胞内胞外的各种应激状态并维持代谢稳态还尚未清楚。本项目基于我们之前发现的低葡萄糖感知和AMPK激活过程中涉及溶酶体、内质网和线粒体等细胞器互作的“时空性”特征的发现，拟进一步探索其它生理、药理状态下AMPK的激活机制和其与不同细胞器的联系，并在此基础上研究其对整体代谢模式的调节，从而为预防和治疗代谢性疾病提供重要的线索和依据。项目执行以来，顺利完成了既定目标，如发现了溶酶体上的葡萄糖感受器醛缩酶不只介导了低葡萄糖水平的感知和AMPK的激活，还控制着高葡萄水平的感知，并在此基础上行使对mTOR的直接激活。还发现了临床剂量的二甲双胍在溶酶体上激活AMPK，并鉴定了其靶蛋白PEN2，后者能够模拟低葡萄糖状态，启动溶酶体上的AMPK激活途径等。这些发现以5篇SCI论文发表在Nature、Cell Research和Nature Cell Biology等杂志，被同行专家在多篇评论性论文中评价为“有多方面的重要意义”和“代表了重大突破”。课题负责人在自然学术会议——细胞代谢国际会议、美国癌症研究协会年会、中国生物化学与分子生物学会全国学术会议、BioArt生命科学前沿学者论坛等国内外会议上做特邀学术报告。课题负责人林圣彩于2021年获评中国科学院院士，课题骨干张宸崧于2019年获得基金委优秀青年科学基金资助，2位博士后出站，3位博士毕业并获得学位，4位硕士毕业并获得学位。