Fnip1 Function in Lymphocyte Development, Activation and Metabolism

相对于静止的淋巴细胞，活化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，从有效产生能量的氧化磷酸化，到产生燃料细胞分裂所需的生物前体（如脂质、氨基酸和核苷酸）的有氧糖酵解。了解控制这种代谢开关的因素（称为“Warburg效应”）是非常重要的，因为它可能导致在自身免疫性疾病中选择性阻断淋巴细胞激活和/或抑制癌细胞存活的新策略。在本申请中，我们建议研究一种名为卵泡蛋白相互作用蛋白-1 （Fnip1）的新蛋白，我们的研究表明，在能量应激（如淋巴细胞激活、营养限制和癌基因激活）期间，该蛋白对于维持“代谢平衡”至关重要。基于外周血中B淋巴细胞的完全缺失，我们在化学诱变筛选中发现了一种缺乏Fnip1的创新小鼠新品系。Fnip1缺失小鼠的前b细胞和不变自然杀伤T （iNKT）细胞发育在细胞通常依赖于c- Myc（一种有效驱动有氧糖酵解的致癌基因）进行大量分裂的阶段受到阻滞。值得注意的是，在伯基特B细胞淋巴瘤小鼠模型中，Fnip1的缺失也可以防止c-Myc诱导的前B细胞淋巴瘤。虽然Fnip1的功能尚不清楚，但它与卵泡蛋白（一种功能未知的蛋白质）和主要代谢调节剂AMP激酶相互作用，AMP激酶是一种能量感应分子，在能量应激下刺激能量产生（氧化磷酸化），并抑制哺乳动物雷帕霉素靶蛋白（mTOR）调节的能量消耗合成代谢过程。我们的长期目标是确定Fnip1如何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。我们将利用代谢组学、代谢通量分析和转录组学方法来确定Fnip1的缺失是否会抑制“Warburg效应”；(2)明确Fnip1在B淋巴细胞中作用的分子机制。我们将使用生化、遗传和质谱方法来确定Fnip1是否对“关闭”mTOR介导的营养消耗和“打开”自噬（细胞器自我消化以产生营养物质）以应对营养不足至关重要；(3)确定Fnip1在iNKT细胞发育和存活中的作用。我们将定义Fnip1如何控制myc依赖性的发育、存活和这一重要调节性T细胞亚群的代谢。这些研究将解决我们的整体创新假设，即抑制Fnip1通过允许活化淋巴细胞和/或肿瘤细胞在缺乏足够能量和生物底物的情况下生长，从而“断开”合成代谢细胞生长和有氧糖酵解之间的基本联系，导致“营养耗尽”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.