CAREER: The Molecular Mechanisms of Cold-Induced Mitochondrial Biogenesis

温度对动物的生理机能有深远的影响。响应于温度降低而发生的一种修饰是某些组织中线粒体密度的增加。这个过程对于维持动物的有氧代谢能力至关重要，但关于它是如何调节的，以及为什么它发生在某些组织中，而不是其他组织，仍然存在问题。本项目将解决这些问题，使用三棘鱼Gasterosteus aculetaus作为模式生物。 这项调查将测试的假设，即活性氧（ROS）是由线粒体在低温下产生的，并需要诱导控制线粒体生物合成的基因的表达。膜流动性随着温度的下降而降低，并可能破坏电子传递链蛋白的活性，导致ROS的形成。这些ROS可以直接调节线粒体生物基因的表达，或者高水平的ROS可以刺激一氧化氮合酶的活性，产生一氧化氮并触发线粒体生物合成。这两种可能性都将得到检验。Stickleback将在实验室中保持在20摄氏度，然后转移到5摄氏度，并保持六周。在整个驯化期间，将收获动物用于测量ROS、线粒体蛋白、基因表达和一氧化氮合酶活性的水平。将在几种组织类型中测量这些参数，包括经历线粒体生物合成的组织（氧化骨骼肌）和可能不经历线粒体生物合成的组织（肝脏）。不同组织类型对低温反应的差异可能阐明了线粒体生物发生的组织特异性机制。如果ROS和/或NO水平在冷适应的早期阶段增加，则将用ROS和/或NO形成的抑制剂处理动物。如果需要这些自由基物质中的任一种来诱导线粒体生物发生，则抑制它们的产生应防止线粒体密度响应于低温而增加。这项工作的结果将导致更好地了解线粒体生物发生的分子机制。这是一个至关重要的过程，对所有生物体的健康至关重要。这项研究将涉及本科生和研究生阿拉斯加原住民学生通过与阿拉斯加大学的阿拉斯加原住民科学和工程计划的合作。这些学生还将帮助在当地农村学校开展一项推广计划，让学生学习动物在寒冷环境中生存的各种策略，重点是生理，细胞和分子适应。学生将了解动物（即使是在当地环境中发现的动物）在解决生物学基本问题方面的重要作用。

Temperature has a profound effect on the physiology of animals. One modification that occurs in response to a decrease in temperature is an increase in mitochondrial density in some tissues. This process is critical for maintaining aerobic metabolic capacity in animals, yet questions remain about how it is regulated, and why it occurs in some tissues, yet not others. This project will address these questions, using the threespine stickleback Gasterosteus aculetaus as a model organism. This investigation will test the hypothesis that reactive oxygen species (ROS) are produced by mitochondria in response to cold temperature and are required to induce the expression of genes controlling mitochondrial biogenesis. Membrane fluidity decreases as temperature declines and may disrupt the activity of the electron transport chain proteins of the mitochondrion, leading to the formation of ROS. These ROS may directly regulate mitochondrial-biogenic gene expression, or alternatively, high levels of ROS may stimulate the activity of nitric oxide synthase which produces nitric oxide and triggers mitochondrial biogenesis. Both of these possibilities will be tested. Sticklebacks will be maintained at 20 degrees C in the laboratory and then shifted to 5 degrees C and held over a period of six weeks. Throughout the acclimation period, animals will be harvested for measuring levels of ROS, mitochondrial proteins, gene expression, and nitric oxide synthase activity. These parameters will be measured in several tissue types, including those that undergo mitochondrial biogenesis (oxidative skeletal muscle), and those that may not (liver). The differences in response to cold temperature among different tissue types may elucidate the mechanisms underlying the tissue specificity of mitochondrial biogenesis. If ROS and/or NO levels increase during the early stages of cold acclimation, then animals will be treated with inhibitors of ROS and/or NO formation. If either of these free radical species are required to induce mitochondrial biogenesis, then inhibiting their production should prevent increases in mitochondrial density in response to cold temperature. The results from this work will lead to a greater understanding of the molecular mechanisms governing mitochondrial biogenesis. This is a vital process, essential to the health of all organisms. This research will involve undergraduate and graduate Alaska Native students through a collaboration with the Alaska Native Science and Engineering Program at the University of Alaska. These students will also help to develop an outreach program at a local rural school which engages students in learning about the variety of strategies that animals use to survive at cold temperature, with an emphasis on physiological, cellular and molecular adaptations. Students will learn the important role of animals, even those found in local environments, for addressing fundamental questions in biology.