The Toxoplasma apicoplast and calcium signaling

弓形虫顶端质体和钙信号传导

• 批准号: 9229418
• 负责人: Silvia N Moreno
• 金额: $ 37.5万
• 依托单位: UNIVERSITY OF GEORGIA
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-11-10 至 2021-10-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9229418
• 关键词: Affect; Algae; Amino Acids; Animals; Antiparasitic Agents; Apicomplexa; Biological Models; Biological Process; Calcium; Calcium Signaling; Cations; Cells; Communication; Complement; Coupled; Cyanobacterium; Defect; Development; Diagnostic; Down-Regulation; Electrophysiology (science); Endosomes; Environment; Enzymes; Gated Ion Channel; Genes; Goals; Growth; Homeostasis; Ion Channel; Ion Channel Gating; Ions; Laboratories; Life; Lysosomes; Mammalian Cell; Medical; Membrane; Metals; Modeling; Mutation; NAADP; Organelles; Parasites; Pathway interactions; Physiological; Physiology; Plants; Plastids; Play; Process; Property; Proteins; Regulation; Reporting; Role; Second Messenger Systems; Signal Transduction; Therapeutic; Toxoplasma; Toxoplasma gondii; Transmembrane Domain; Vaccines; Vacuole; Work; biophysical techniques; calcium indicator; chemotherapy; fitness; microorganism; mutant; novel; novel therapeutics; pathogen; receptor; therapeutic target; uptake; voltage

Apicomplexan parasites include a number of pathogens of medical and veterinary importance and our long- term goal is to identify novel molecules and pathways in these microorganisms that could be targets for chemotherapy, diagnostic applications, or vaccines. Many of these parasites rely for their survival on biosynthetic pathways that occur in a remnant plastid known as the apicoplast. A large number of these anabolic pathways are essential for the life of the parasite. Our laboratory recently found a two-pore channel (TPC) that localizes to the apicoplast membrane(s) and is essential for growth of Toxoplasma gondii. Two-pore channels belong to the superfamily of voltage-gated ion channels and are characterized by the presence of two sets of six-transmembrane domains (TMDs). This was an important discovery because it exposed a completely untapped question, which is the role of ions like Ca2+ on the activity of essential anabolic enzymes of the organelle and how this impacts parasite fitness. In addition, and more importantly, ion channels are targets of many therapeutically useful agents and they remain significantly under-exploited as therapeutic targets, even more so as antiparasitic agents. The apicoplast, the product of a secondary endosymbiosis process, is an organelle surrounded by membranes derived from the cyanobacterium that gave origin to the plastid, the endosymbiotic alga, and the host endosomal compartment. Metal ions play essential roles for the activity of more than one third of all enzymes and considering the large number of essential activities present in the apicoplast, it is likely that ions will be highly regulated in the organelle. No ion transporters or channels have been reported in the apicoplast until now. This makes our recent discovery of a two-pore channel localized to the apicoplast a unique finding and also an unexpected opportunity for the development of new therapies. TPCs are found in both animal and plant cells where they localize to acidic organelles such as endosomes, lysosomes and vacuoles. TPCs function as Ca2+ channels in mammalian cells and are activated by the second messenger nicotinic acid adenine dinucleotide phosphate (NAADP). The Toxoplasma TPC localization to the plastid is unique to Apicomplexa and highlights a novel and potentially specific role for the organelle multiple functions. We silenced the T. gondii TgTPC gene and found that the mutants display a severe growth defect that can be rescued by complementation with a functional channel. Our hypothesis is that the TPC is a non-selective channel that upon voltage gating is able to conduct cations but in the environment of the cell it probably prefers Ca2+. This hypothesis implies that the apicoplast contains Ca2+, an idea supported by preliminary evidence. We propose a model in which the apicoplast through the TPC and Ca2+ communicates with other organelles via other potential Ca2+ channels. Two other candidate Ca2+ channels will be studied. Our goal is to define the physiological function of TgTPC using sophisticated biophysical approaches in the context of several model systems. We will combine this with live cell studies to determine how their activity influences the physiology of the apicoplast and other intracellular organelles and the fitness of the parasite.

Apicomplexan寄生虫包括许多医学和兽医的病原体，我们的长期 术语目标是在这些微生物中识别新的分子和途径，这可能是目标的目标 化学疗法，诊断应用或疫苗。 这些寄生虫中的许多依赖于它们在残留物质中发生的生物合成途径的生存 被称为apicoplast。这些合成代谢途径中有许多对于寄生虫的寿命至关重要。 我们的实验室最近发现了一个定位于apicoplast膜的两孔通道（TPC），并且IS 对于弓形虫的生长至关重要。两孔通道属于电压门控离子的超家族 通道，其特征是存在两组六跨膜结构域（TMDS）。这是 一个重要的发现，因为它暴露了一个完全未开发的问题，这是Ca2+等离子的作用 关于细胞器必需合成代谢酶的活性以及这如何影响寄生虫适应性。在 此外，更重要的是，离子通道是许多治疗用剂的靶标，它们是 作为治疗靶标的探索量明显不足，甚至是抗寄生虫。 apicoplast是继发性内共生过程的产物，是一个被包围的细胞器 源自质体的蓝细菌，质体，内共生藻类和 宿主内体隔室。金属离子在超过三分之一以上的活动中起着重要的作用 酶并考虑了Apicoplast中存在的大量基本活动，可能是离子 将在细胞器中受到高度调节。尚未在Apicoplast中报道过离子转运蛋白或通道 到目前为止。 这使得我们最近发现的两孔频道本地定位在popicoplast上是一个独特的发现， 这也是开发新疗法的意外机会。在动物和 植物细胞将其定位于酸性细胞器，例如内体，溶酶体和液泡。 TPC 在哺乳动物细胞中充当Ca2+通道，并被第二信使烟酸激活 腺苷二核苷酸磷酸盐（NAADP）。在质体中的毒品TPC定位是独有的 apicomplexa并突出了细胞器多个功能的新颖且潜在的特定作用。 我们沉默了T. gondii tgtpc基因，发现突变体显示出严重的生长缺陷，可以 通过与功能通道的补充来挽救。我们的假设是TPC是非选择性的 渠道，电压门控能够进行阳离子，但在电池的环境中可能是 喜欢Ca2+。该假设意味着apicoplast包含Ca2+，这是由初步支持的想法 证据。我们提出了一个模型，其中apicoplast通过TPC和Ca2+与其他 通过其他潜在CA2+通道的细胞器。将研究另外两个候选CA2+通道。 我们的目标是使用复杂的生物物理来定义TGTPC的生理功能 在几个模型系统的背景下进行接近。我们将将其与现场细胞研究结合到 确定其活性如何影响凋亡和其他细胞内的生理 细胞器和寄生虫的健身。