ATM, REACTIVE OXYGEN, AND CELLULAR RESPONSES TO HYPOXIA

描述(申请人提供)：细胞对DNA损伤和其他压力的反应是细胞存活和突变的重要决定因素，并影响一系列人类疾病的发展。低氧和氧化应激在许多人类疾病的发病机制中也是重要的，从癌症到心血管疾病，从神经疾病到衰老。信号转导通路的诱导是细胞对这些胁迫反应的一个重要方面，近年来在阐明这些信号转导通路中的生化步骤方面取得了重大进展。澄清这些步骤可以对这些反应进行调整，从而加强研究，并有可能导致开发预防和治疗这些疾病的新药。ATM蛋白激酶是调节细胞对DNA断裂反应的中心信号分子。ATM基因突变的患者有一种破坏性的临床疾病，称为共济失调-毛细血管扩张，并有各种医学问题，包括神经退化、免疫缺陷、癌症易感性、胰岛素抵抗和毛细血管扩张的发展。这里提出的论点是，这些患者的多效性异常可能不仅仅是由于DNA损伤反应异常。提出了一种新的观点，即线粒体异常引起的活性氧水平升高和细胞对低氧应激反应的异常导致了共济失调-毛细血管扩张症患者的许多或全部病理生理状态。提供的初步数据证实，在缺乏ATM功能的细胞中，活性氧的水平增加，在缺乏ATM的细胞和组织中发现线粒体异常。有趣的是，自噬相关基因BECLIN的单个等位基因的缺失，部分挽救了缺乏ATM的小鼠体内活性氧物种、线粒体和癌症易感性的异常。建议进行实验，以进一步探索ATM丢失导致线粒体异常和活性氧水平异常的机制，以及Beclin杂合性如何拯救这些异常。初步数据还显示，缺乏ATM功能的细胞对低氧应激的异常反应。有人建议通过实验来探索ATM丢失的机制，可能是通过影响线粒体和活性氧物种，影响细胞对低氧应激的反应。ATM在调节Hif-11或Hif-21信号通路中的作用将被研究。这项拟议的实验的成功完成可能导致对ATM蛋白意想不到的细胞功能的新见解，并为导致癌症发展、神经退化和代谢异常的常见机制建立新的范例。

DESCRIPTION (provided by applicant): Cellular responses to DNA damage and other stresses are important determinants of cell viability and mutagenesis and impact the development of a wide range of human diseases. Hypoxic and oxidative stresses are also important in the pathogenesis of many human diseases, ranging from cancer to cardiovascular disease to neurological disorders to aging. Induction of signal transduction pathways is a critical aspect of cellular responses to these stresses and significant advances have been made in recent years elucidating the biochemical steps in such signaling pathways. Clarification of such steps enables modulation of these responses, which can enhance research studies and have the potential to lead to development of new medicines to prevent and treat these diseases. The ATM protein kinase is a central signaling molecule in modulating cellular responses to DNA breakage. Patients with mutated ATM genes have a devastating clinical disorder known as Ataxia-telangiectasia and have a variety of medical problems, including neurodegeneration, immunodeficiency, cancer predisposition, insulin resistance, and telangiectasia development. Arguments are put forth here that the pleiotropic abnormalities in these patients may not simply be due to DNA damage response abnormalities. A novel proposal is made that increased levels of reactive oxygen species, resulting from mitochondrial abnormalities, and abnormalities in cellular responses to hypoxic stresses contribute to or cause many or all of the pathophysiologic states seen in patients with Ataxia-telangiectasia. Preliminary data is presented confirming increased levels of reactive oxygen species in cells lacking ATM function and mitochondrial abnormalities are identified in mouse and human cells and tissues lacking ATM. Interestingly, loss of a single allele of the autophagy-related gene, beclin, partially rescued the abnormalities in reactive oxygen species, mitochondria, and cancer predisposition in mice lacking ATM. Experiments are proposed to further explore the mechanisms by which ATM loss leads to abnormalities in mitochondria and levels of reactive oxygen species and how beclin heterozygosity rescues these abnormalities. Preliminary data also demonstrated abnormal responses to hypoxic stress in cells lacking ATM function. Experiments are proposed to explore the mechanisms by which ATM loss, perhaps through its impact on mitochondria and reactive oxygen species, affects cellular responses to hypoxic stress. The role of ATM in modulating either the Hif-11 or Hif-21 signaling pathways will be investigated. Successful completion of the proposed experiments could lead to new insights into unexpected cellular functions of the ATM protein and establish new paradigms for common mechanisms that contribute to cancer development, neurodegeneration, and metabolic abnormalities.