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：
8651736
负责人：
ROBERTO DOCAMPO
金额：
$ 22.35万
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 2016-06-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8651736
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 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 Tropical Disease 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 neglect overexpression public health relevance receptor success tool tripolyphosphate uptake

项目摘要

Abstract 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.

抽象的布氏锥虫群寄生虫是昏睡病或非洲锥虫病的病原体。据世界卫生组织称，撒哈拉以南非洲地区有超过 6000 万人面临感染风险感染，每年发生数千例。非洲锥虫病再次出现自 20 世纪 70 年代以来，化疗仍然不能令人满意，尤其是对于晚期病例。 T. brucei 位于此外，锥虫最适合分子和遗传实验，并且其强大的遗传工具已经开发出来。在生理条件下，线粒体对 Ca2+ 的吸收是通过单端口机制由负内膜电位驱动电泳，无需直接与 ATP 水解或其他离子的运输耦合。这个 MCU 被发现已有 50 多年历史（1961- 1962）在啮齿动物线粒体中，这种 Ca2+ 选择性通道的生物物理特性得到了广泛的研究从那时起就具有特征。在哺乳动物线粒体中发现 MCU 后的许多年里，认为不太复杂的生命形式，如植物、昆虫和其他无脊椎动物，或单细胞生物例如酵母，缺乏特定的线粒体钙吸收途径。直到 1989 年我们报道说，克氏锥虫（恰加斯病的病原体）的上鞭毛体拥有一个 MCU 与哺乳动物线粒体相似的特征：电传输、对线粒体的敏感性钌红，与阳离子的亲和力低。锥虫中存在 MCU 的证据，但其酵母中的缺失是发现 MCU 分子身份的关键。哺乳动物线粒体在细胞内 Ca2+ 稳态中具有核心作用，并且已明确线粒体内 Ca2+ 当胞质 Ca2+ 增加几微摩尔时，浓度可达到数十或数百微摩尔值。这是因为线粒体暴露于靠近 Ca2+ 的位点的高浓度微域中。 Ca2+ 在内质网释放，或释放到质膜上的 Ca2+ 通道。此 Ca2+ 吸收量为对于塑造细胞质 Ca2+ 增加的幅度和时空模式很重要，调节导致 ATP 生成的三种线粒体内脱氢酶的活性，以及 ATP合酶的活性。然而，过量的 Ca2+ 吸收有利于“渗透性”的形成。过渡孔”导致细胞质中促凋亡因子的释放和细胞死亡。有趣的是，T. 布氏线粒体也暴露于酸性钙体附近的高 Ca2+ 水平，酸性钙我们于 1994 年在 T. brucei 中发现的储存室，其中含有肌醇 1,4,5- 用于 Ca2+ 释放的三磷酸受体 (IP3R)。我们的假设是 T. brucei 可用于研究 MCU 和线粒体 Ca2+ 摄取的重要性，线粒体和线粒体之间的关系酸性钙体，以及线粒体 Ca2+ 摄取复合物的其他成分的存在被假设存在。