Endolysosomal-nuclear communication mediated through V-ATPase and NHE9 dependent epigenetic signaling

肿瘤暴露在不断变化的营养环境中，这会产生代谢压力， 它们的生长和增殖。因此，癌细胞进化出表型适应性来对抗这一点。 需要表观遗传和转录重编程的营养流。这些表型适应也可以 影响肿瘤细胞对化疗剂的敏感性。细胞质细胞器如何参与营养 信号对核表观基因组的影响仍然是一个基本的问题，因为这些 途径是抗癌药物开发的候选治疗靶点。V-ATP酶是一种 进化上保守的多聚体质子泵，酸化内溶酶体区室以调节 细胞内pH和激活必需营养信号通路。Na+/H+交换器（NHE）因子， 特别是NHE 9，拮抗V-ATP酶依赖性内体酸化。NHE 9在许多细胞中过度表达， 最近的研究表明，NHE 9在胶质母细胞瘤（GBM）中的过表达有助于 直接导致肿瘤发生。有趣的是，芽殖酵母的基因筛选同时鉴定出了V-ATPase和 酵母NHE 9直系同源物，Nhx 1，作为组蛋白H3和H4（H3/H4）乙酰化的调节剂， 机制等我们的初步数据表明，人GBM细胞中的V-ATP酶信号也调节 H3/H4乙酰化，从而证明V-ATP酶是进化上保守的表观遗传调节因子。 该项目将测试V-ATP酶和Nhx 1/NHE 9调节内溶酶体的创新假设， 核通讯需要表观遗传适应改变营养状态。使用酵母和人类 GBM模型，我们将执行以下具体目标。在目标I中，我们将确定关键的营养信号 V-ATP酶下游的途径控制全球H3/H4乙酰化，然后我们将确定这是否 涉及去乙酰化酶的沉默调节蛋白家族的抑制，或者是否涉及非沉默调节蛋白机制。我们将测试 特别是如果V-ATP酶依赖性H3/H4乙酰化调节ATP依赖性染色质的结合 对代谢基因转录重要的重塑酶。在目标II中，我们将确定V-ATP酶是否 依赖性H3/H4乙酰化控制DNA对烷化剂（包括GBM）的损伤反应 护理标准化疗剂替莫唑胺（TMZ），通过锚定ATP依赖性核小体 将酶重塑到染色质上。在项目完成后，我们将定义一个新的范例， 内溶酶体区室调节对代谢基因至关重要的核表观遗传途径， 表达和对遗传毒性应激的敏感性。

Tumors are exposed to constantly changing nutrient environments which creates metabolic stress that impairs their growth and proliferation. Consequently, cancer cells evolve phenotypic adaptations to contend with this nutrient flux that require epigenetic and transcriptional reprogramming. These phenotypic adaptations also can affect tumor cell sensitivity to chemotherapeutic agents. How cytoplasmic organelles involved in nutrient signaling exert their effects on the nuclear epigenome remains a fundamental problem to define since these pathways are candidate therapeutic targets for anticancer drug development. The V-ATPase is an evolutionarily conserved multimeric proton pump that acidifies the endolysosomal compartment to regulate intracellular pH and activate essential nutrient signaling pathways. Na+/H+ exchanger (NHE) factors, specifically NHE9, antagonize V-ATPase dependent endosomal acidification. NHE9 is overexpressed in many tumors, and recent studies have demonstrated that NHE9 overexpression in glioblastoma (GBM) contributes directly to tumorigenesis. Intriguingly, genetic screens in budding yeast identified both the V-ATPase and the yeast NHE9 ortholog, Nhx1, as regulators of histone H3 and H4 (H3/H4) acetylation through unknown mechanisms. Our preliminary data demonstrate that V-ATPase signaling in human GBM cells also regulates H3/H4 acetylation, thus demonstrating that the V-ATPase is an evolutionarily conserved epigenetic regulator. This project will test the innovative hypothesis that the V-ATPase and Nhx1/NHE9 regulate the endolysosomal- nuclear communication required for epigenetic adaptation to altered nutrient states. Using yeast and human GBM models, we will perform the following Specific Aims. In Aim I, we will identify the key nutrient signaling pathways downstream of the V-ATPase controlling global H3/H4 acetylation, and then we will determine if this involves repression of the sirtuin family of deacetylases or if it involves non-sirtuin mechanisms. We will test specifically if V-ATPase dependent H3/H4 acetylation regulates the binding of ATP-dependent chromatin remodeling enzymes important for transcription of metabolic genes. In Aim II, we will determine if V-ATPase dependent H3/H4 acetylation controls the DNA damage response to alkylating agents, including the GBM standard of care chemotherapeutic agent temozolomide (TMZ), by anchoring ATP-dependent nucleosome remodeling enzymes onto chromatin. Upon the project's completion, we will have defined a novel paradigm by which the endolysosomal compartment regulates nuclear epigenetic pathways critical for metabolic gene expression and sensitivity to genotoxic stress.