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The mitochondrial calcium uniporter of trypanosomes

锥虫线粒体钙单向转运蛋白

基本信息

批准号：
8874884
负责人：
ROBERTO DOCAMPO
金额：
$ 18.75万
依托单位：
UNIVERSITY OF GEORGIA
依托单位国家：
美国
项目类别：
财政年份：
2014
资助国家：
美国
起止时间：
2014-07-01 至 2017-06-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8874884
关键词：
ATP Hydrolysis Abbreviations Address Affinity Africa South of the Sahara African Trypanosomiasis Biochemistry Blood Circulation Calcium Cations Cell Death Cell membrane Chagas Disease Characteristics Circular DNA Complex Coupling Cytosol Endoplasmic Reticulum Eukaryota Generations Genes Genetic Goals Growth and Development function Health Homeostasis ITPR1 gene In Vitro Incidence Infection Infection Control Inositol Insecta Invertebrates Ions Kinetoplast DNA Knock-out Knowledge Life Mammalian Cell Membrane Potentials Metabolic Pathway Mitochondria Mitochondrial DNA Mitochondrial Proteins Modeling Molecular Molecular Genetics Nature Organelles Organism Orthologous Gene Oxidoreductase Parasites Pathogenicity Pathway interactions Pattern Permeability Pharmaceutical Preparations Physiological Plants Proteins RNA Editing RNA Interference Regulation Reporting Risk Rodent Role Ruthenium Red Shapes Site Stress Testing Trypanocidal Agents Trypanosoma Trypanosoma brucei brucei Trypanosoma cruzi Two-Hybrid System Techniques Uniport Work World Health Organization Yeasts biophysical properties calcium uniporter chemotherapy coping design extranuclear DNA genome sequencing in vivo insight mutant neglected tropical diseases overexpression receptor success tool tripolyphosphate uptake

项目摘要

DESCRIPTION (provided by applicant): The T. brucei group of parasites is the causative agent of sleeping sickness or African trypanosomiasis. According to the World Health Organization over 60 million people in sub-Saharan Africa are at risk of infection with an incidence of thousands of cases per year. African trypanosomiasis has been reemerging since the 1970s, and chemotherapy remains unsatisfactory especially for advanced cases. T. brucei is, in addition, the trypanosome most amenable to molecular and genetic experimentation, and for which powerful genetic tools have been developed. Under physiological conditions mitochondrial Ca2+ uptake takes place by the uniport mechanism driven electrophoretically by the negative-inside membrane potential without direct coupling to ATP hydrolysis or transport of other ions. This MCU was found more than 50 years ago (1961- 1962) in rodent mitochondria and the biophysical properties of this Ca2+-selective channel were extensively characterized since then. For many years after the discovery of the MCU in mammalian mitochondria, it was thought that less complex life forms such as plants, insects and other invertebrates, or unicellular organisms such as yeast, lacked a specific mitochondrial calcium uptake pathway. This was until we reported, in 1989, that epimastigotes of Trypanosoma cruzi, the etiologic agent of Chagas disease, possesses a MCU with characteristics similar to those described in mammalian mitochondria: electrogenic transport, sensitivity to ruthenium red, and low affinity for the cation. The evidence of the presence of a MCU in trypanosomes but its absence in yeast was the key to the discovery of the molecular identity of MCU. Mammalian mitochondria have a central role in intracellular Ca2+ homeostasis, and it is well established that intramitochondrial Ca2+ concentration can reach tens or hundreds micromolar values upon cytosolic Ca2+ rises of a few micromolar. This is because mitochondria are exposed to microdomains of high Ca2+ concentration in proximity to sites of Ca2+ release at the endoplasmic reticulum, or to Ca2+ channels at the plasma membrane. This Ca2+ uptake is important for shaping the amplitude and spatio-temporal patterns of cytosolic Ca2+ increases and for regulating the activity of three intramitochondrial dehydrogenases that result in ATP generation, as well as the activity of the ATP synthase. Excessive Ca2+ uptake, however, favors the formation of the "permeability transition pore" leading to the release of proapoptotic factors in the cytosol and cell death. Interestingly, T. brucei mitochondrion is also exposed to high Ca2+ levels in proximity to acidocalcisomes, acidic calcium storage compartments that we discovered in T. brucei in 1994, and that contain the inositol 1,4,5- triphosphate receptor (IP3R) for Ca2+ release. Our hypothesis is that T. brucei could be used to investigate the essentiality of the MCU and mitochondrial Ca2+ uptake, the relation between mitochondria and acidocalcisomes, and the presence of other components of the mitochondrial Ca2+ uptake complex that have been postulated to exist.

描述（由申请人提供）：T。布氏寄生虫群是昏睡病或非洲锥虫病的病原体。据世界卫生组织称，撒哈拉以南非洲有6 000多万人面临感染风险，每年发生数千例病例。非洲锥虫病自20世纪70年代以来重新出现，化疗仍然不能令人满意，特别是对晚期病例。T.此外，布氏锥虫是最适合进行分子和遗传实验的锥虫，已经开发了强大的遗传工具。在生理条件下，线粒体Ca 2+摄取通过膜内负电位驱动的单端口机制发生，而不直接偶联到ATP水解或其他离子的转运。该MCU在50多年前（1961- 1962）在啮齿动物线粒体中被发现，并且从那时起，该Ca 2+选择性通道的生物物理特性被广泛表征。在哺乳动物线粒体中发现MCU后的许多年里，人们认为不太复杂的生命形式，如植物，昆虫和其他无脊椎动物，或单细胞生物，如酵母，缺乏特定的线粒体钙摄取途径。直到1989年，我们报道了查加斯病的病原体克氏锥虫的外鞭毛体具有与哺乳动物线粒体中描述的特征相似的MCU：产电运输，对钌红的敏感性和对阳离子的低亲和力。在锥虫中存在MCU而在酵母中不存在MCU的证据是发现MCU分子身份的关键。哺乳动物线粒体在细胞内Ca 2+稳态中具有中心作用，并且已经确定，当细胞溶质Ca 2+升高几微摩尔时，线粒体内Ca 2+浓度可以达到数十或数百微摩尔值。这是因为线粒体暴露于靠近内质网Ca 2+释放位点的高Ca 2+浓度的微区，或质膜上的Ca 2+通道。这种Ca 2+摄取对于塑造胞质Ca 2+增加的幅度和时空模式以及调节导致ATP产生的三种线粒体内ATP酶的活性以及ATP合酶的活性是重要的。然而，过量的Ca 2+摄取有利于形成“渗透性转换孔”，导致细胞溶质中促凋亡因子的释放和细胞死亡。有趣的是，T。布氏杆菌也暴露于接近酸钙体的高Ca 2+水平，酸钙体是我们在T. 1994年报道了Brucei的一种新的钙通道蛋白，该蛋白含有肌醇1，4，5-三磷酸受体（IP 3R），用于钙离子的释放。我们假设T.布氏杆菌可用于研究MCU和线粒体Ca 2+摄取的重要性，线粒体和酸钙体之间的关系，以及已假定存在的线粒体Ca 2+摄取复合物的其他组分的存在。