Fnip1 Function in Lymphocyte Development, Activation and Metabolism

描述(申请人提供)：项目摘要相对于静止的淋巴细胞，激活的淋巴细胞和癌细胞在细胞代谢方面都表现出独特的转变，从有效地产生能量的氧化磷酸化转变为有氧糖酵解，后者产生促进细胞分裂所需的生物前体(如脂类、氨基酸和核苷酸)。了解控制这种代谢转换的因素(称为“Warburg效应”)具有非常重要的意义，因为它可能导致有选择地阻断自身免疫性疾病中淋巴细胞激活的新策略，和/或抑制癌细胞存活。在这一应用中，我们建议研究一种名为毛囊相互作用蛋白-1(Fnip1)的新蛋白质，我们的研究表明，在能量应激期间，如在淋巴细胞激活、营养限制和癌基因激活期间，Fnip1对于维持“代谢平衡”是必不可少的。我们在化学诱变筛选中发现了一种新型的缺乏Fnip1的小鼠，这是基于外周血中完全没有B淋巴细胞的基础上的。Fnip1基因缺失的小鼠在前B细胞和不变自然杀伤T细胞(INKT)发育阶段受阻，这些细胞通常依靠c-Myc进行大规模分裂，c-Myc是一种癌基因，可以有效地驱动有氧糖酵解。值得注意的是，Fnip1的缺失也对c-Myc诱导的Burkitt‘s B细胞淋巴瘤小鼠模型中的前B细胞淋巴瘤具有保护作用。尽管Fnip1的功能尚不清楚，但它与毛囊蛋白(一种功能未知的蛋白质)和主要代谢调节因子AMP激酶相互作用，AMP激酶是一种能量敏感分子，可刺激能量产生(氧化磷酸化)以响应能量应激，并抑制由哺乳动物雷帕霉素靶标(MTOR)调控的耗能合成代谢过程。我们的长期目标是确定Fnip1如何发挥作用来控制淋巴细胞的发育、代谢和转化。我们的具体目标是：(1)研究Fnip1在前B细胞发育和代谢中的作用。我们将利用代谢学、代谢流量分析和转录学方法来确定Fnip1的缺失是否抑制了“Warburg效应”；(2)确定Fnip1在B淋巴细胞中发挥作用的分子机制。我们将使用生化、遗传和质谱学方法来确定Fnip1是否是“关闭”mTOR介导的营养消耗和“开启”自噬(细胞器自我消化以产生营养物质)以应对营养缺乏所必需的；以及(3)确定Fnip1在iNKT细胞发育和生存中的作用。我们将确定Fnip1是如何控制这个重要的调节性T细胞亚群的依赖Myc的发育、存活和代谢的。这些研究将解决我们的总体创新假设，即抑制Fnip1通过允许激活的淋巴细胞和/或肿瘤细胞在缺乏足够的能量和生物底物的情况下生长，从而“切断”合成代谢细胞生长和有氧糖酵解之间的基本联系，从而导致“营养耗竭”和细胞死亡。

DESCRIPTION (provided by applicant): Project Summary Relative to resting lymphocytes, both activated lymphocytes and cancer cells exhibit a unique shift in cell metabolism from oxidative phosphorylation, which efficiently produces energy, to aerobic glycolysis, which generates bio-precursors (such as lipids, amino acids, and nucleotides) required to fuel cell division. An understanding of the factors that control this metabolic switch (termed "Warburg effect") is highly significant because it could lead to novel strategies to selectively block lymphocyte activation in autoimmune disease, and/or inhibit cancer cell survival. In this application, we propose to investigate a novel protein called Folliculin Interacting protein-1 (Fnip1) which our studies suggest is essential for maintaining "metabolic balance" during energy stress such as during lymphocyte activation, nutrient restriction, and oncogene activation. We identified an innovative new strain of mice lacking Fnip1 in a chemical mutagenesis screen, based on the complete absence of B lymphocytes in peripheral blood. Fnip1 null mice have blocks in pre-B cell and invariant natural killer T (iNKT) cell development at stages where the cells normally undergo massive division dependent on c- Myc, an oncogene which potently drives aerobic glycolysis. Remarkably, loss of Fnip1 also protects against pre-B cell lymphoma induced by c-Myc in a mouse model of Burkitt's B cell lymphoma. Although the functions of Fnip1 are unknown, it interacts with Folliculin (a protein of unknown function) and the master metabolic regulator AMP kinase, an energy sensing molecule that stimulates energy production (oxidative phosphorylation) in response to energy stress and inhibits energy-consuming anabolic processes regulated by mammalian target of rapamycin (mTOR). Our long-term goals are to determine how Fnip1 functions to control the development, metabolism, and transformation of lymphocytes. Our Specific Aims are: (1) To examine the roles of Fnip1 in pre-B cell development and metabolism. We will utilize metabolomic, metabolic flux analysis, and transcriptomic approaches to determine whether loss of Fnip1 inhibits the "Warburg effect"; (2) To define the molecular mechanisms of Fnip1 function in B lymphocytes. We will use biochemical, genetic, and mass spectrometry approaches to determine whether Fnip1 is essential to "turn off" mTOR mediated nutrient consumption, and "turn on" autophagy (self-digestion of organelles to generate nutrients) in response to nutrient deficit; and (3) To determine the roles of Fnip1 in iNKT cell development and survival. We will define how Fnip1 controls Myc-dependent development, survival and metabolism of this important regulatory T cell subset. These studies will address our overall innovative hypothesis that inhibition of Fnip1 "disconnects" the essential link between anabolic cell growth and aerobic glycolysis, by permitting activated lymphocytes and/or tumor cells to grow in the absence of sufficient energy and bio-substrates, resulting in "nutrient exhaustion" and cell death.