ATM, REACTIVE OXYGEN, AND CELLULAR RESPONSES TO HYPOXIA

描述（由申请人提供）：细胞对DNA损伤和其他应激的反应是细胞活力和诱变的重要决定因素，并影响多种人类疾病的发展。低血糖和氧化应激在许多人类疾病的发病机制中也很重要，从癌症到心血管疾病，从神经系统疾病到衰老。信号转导途径的诱导是细胞对这些应激反应的一个重要方面，近年来在阐明这些信号转导途径中的生物化学步骤方面取得了重大进展。阐明这些步骤能够调节这些反应，这可以加强研究，并有可能导致开发新的药物来预防和治疗这些疾病。ATM蛋白激酶是调节细胞对DNA断裂反应的中心信号分子。ATM基因突变的患者具有称为共济失调-毛细血管扩张的破坏性临床病症，并且具有多种医学问题，包括神经变性、免疫缺陷、癌症易感性、胰岛素抵抗和毛细血管扩张发展。这里提出的论点，在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。一个新的建议，活性氧的水平增加，导致线粒体异常，和异常的细胞反应缺氧应力有助于或导致许多或所有的病理生理状态与共济失调毛细血管扩张症患者。初步数据证实，在缺乏ATM功能的细胞中活性氧水平增加，并且在缺乏ATM的小鼠和人类细胞和组织中鉴定出线粒体异常。有趣的是，自噬相关基因beclin的单个等位基因的丢失部分挽救了缺乏ATM的小鼠中活性氧、线粒体和癌症易感性的异常。实验提出进一步探讨ATM丢失导致线粒体和活性氧水平异常的机制，以及如何beclin杂合性挽救这些异常。初步数据还表明，缺乏ATM功能的细胞对缺氧应激的反应异常。实验拟探讨ATM损失的机制，可能通过其对线粒体和活性氧的影响，影响细胞对缺氧应激的反应。将研究ATM在调节Hif-11或Hif-21信号通路中的作用。成功完成拟议的实验可能会导致对ATM蛋白意想不到的细胞功能的新见解，并为有助于癌症发展，神经变性和代谢异常的常见机制建立新的范式。

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.