Control of Metabolism and Energy-Sensing Pathways by c-Myc

描述(申请人提供)：T恶性转化与许多表型改变有关，其中一些促进增殖。参与这些变化的许多信号通路最终会聚到c-Myc(Myc)癌蛋白上，c-Myc是一种具有数百个遗传靶点的bHLH-ZIP转录因子。事实上，Myc本身的初级去调控在许多癌症中都会发生。Myc转化细胞的快速生长和增殖与合成代谢途径的上调有关，合成代谢途径提供维持这些活性所需的大分子前体。目前认为，Myc通过将糖酵解和TCA循环中间产物转移到这些合成代谢途径中，同时增加ATP合成速率来满足细胞不断增加的能量需求，从而改变代谢。这可能部分解释了为什么许多肿瘤表现为有氧糖酵解(Warburg效应)。我们最近发现，Myc也是维持线粒体电子传输链(ETC)复合体I和V的结构和功能所必需的，从而解释了Myc缺陷细胞严重耗尽ATP的原因。在这些发现的基础上，我们还观察到Myc通过上调主要的线粒体蛋白脱乙酰酶sirtuin 3(SIRT3)在翻译后水平上调节线粒体蛋白质的功能。因此，在特定的目标1中，我们建议通过确定SIRT3的主要蛋白质靶标如何被Myc和乙酰化改变来确定SIRT3和Myc如何协同调节线粒体的结构和功能。我们还提供了证据表明，在Myc失活和ATP耗竭的反应中，能量敏感的AMP依赖的蛋白激酶(AMPK)被激活，以抑制能量利用的合成代谢过程，恢复ATP水平。因此，在特定的目标2中，我们将确定Myc和AMPK如何沟通，以平衡新陈代谢和ATP水平。最后，我们提供的证据表明，Myc和相关的Myc家族成员bHLH-ZIP蛋白ChREBP也通过协调调节迄今尚未完全确定的糖酵解和脂肪生成基因进行沟通，并且ChREBP作为促合成因子的表达与抗合成代谢的AMPK的表达呈负相关。因此，具体目标3将描述Myc和ChREBP在能量产生过程中的协同作用，特别是与糖酵解和脂肪生成有关的过程。这一应用的压倒一切的假设是，Myc与能量感受通路、糖酵解、脂肪生成以及线粒体功能的直接和翻译后控制进行沟通和调节，以此作为控制细胞增殖的一种手段。拟议的研究将利用最先进的方法和补充体外和体内模型。这三位合作研究人员在Myc生物学(Prochownik)、线粒体sirtuins和脂肪酸代谢(Goetzman)以及糖酵解和产脂基因调控(Scott)方面拥有强大和协同的合作关系以及特定领域的专业知识。

DESCRIPTION (provided by applicant): T Malignant transformation is associated with numerous phenotypic alterations, some of which promote proliferation. Many of the signaling pathways involved in these changes ultimately converge upon the c- Myc (Myc) oncoprotein, a bHLH-ZIP transcription factor with hundreds of genetic targets. Indeed, primary de-regulation of Myc itself occurs in many cancers. The rapid growth and proliferation of Myc-transformed cells is associated with the up-regulation of anabolic pathways which supply the macromolecular precursors necessary to maintain these activities. It is currently believed that Myc alters metabolism by diverting glycolytic and TCA cycle intermediates into these anabolic pathways while concurrently increasing ATP synthetic rates to meet increased cellular energy demands. This may partly explain why many tumors display aerobic glycolysis (The Warburg Effect). We have recently shown that Myc is also needed to maintain the structure and function of mitochondrial electron transport chain (ETC) Complexes I and V, thus explaining why Myc-deficient cells are severely ATP-depleted. In extension of these findings, we have also observed that Myc regulates mitochondrial protein function at the post-translational level through its up-regulation of sirtuin 3 (Sirt3), the major mitochondrial protein deacetylase. Therefore, in Specifi Aim 1, we propose to determine how Sirt3 and Myc cooperatively regulate mitochondrial structure and function by determining how the major protein targets of Sirt3 are altered by Myc and acetylation. We also provide evidence that, in response to Myc inactivation and ATP depletion, the energy-sensing AMP-dependent protein kinase (AMPK) is activated to dampen energy-utilizing anabolic processes and restore ATP levels. Therefore, in Specific Aim 2, we will determine how Myc and AMPK communicate to balance metabolism and ATP levels. Finally, we provide evidence that Myc and the related Myc family member bHLH-ZIP protein, ChREBP, also communicate by coordinately regulating an as yet incompletely defined repertoire of glycolytic and lipogenic genes and that ChREBP expression as a pro-anabolic factor is inversely correlated with that of anti-anabolic AMPK. Therefore, Specific Aim 3 will characterize Myc's and ChREBP's cooperating roles in energy-generating processes particularly those related to glycolysis and lipogenesis. The overriding hypothesis of this application is that Myc communicates with and regulates energy sensing pathways, glycolysis, lipogenesis and the direct and post-translational control of mitochondrial function as a means of controlling cell proliferation. The proposed studies will utilize state-of-the-art methodologies and complementing in vitro and in vivo models. The three co-investigators possess strong and synergistic collaborative ties as well as specific areas of expertise in Myc biology (Prochownik), mitochondrial sirtuins and fatty acid metabolism (Goetzman), and glycolytic and lipogenic gene regulation (Scott).