Divergent Calcium Channels of the Apicomplexan parasite Toxoplasma gondii

顶复门寄生虫弓形虫的不同钙通道

• 批准号: 10681807
• 负责人: Silvia N Moreno
• 金额: $ 62.48万
• 依托单位: UNIVERSITY OF GEORGIA
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-02-07 至 2028-01-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10681807
• 关键词: Address; Affinity; Animals; Antiparasitic Agents; Bacteria; Bacterial Adhesins; Biochemical; Biological; Biological Process; Biology; Calcium; Calcium Channel; Calcium Signaling; Candidate Disease Gene; Cell Differentiation process; Cell membrane; Cell physiology; Cells; Characteristics; Clinical; Collaborations; Complex; Cryptosporidiosis; Cytosol; Data; Defect; Dihydropyridines; Disease; Drug Targeting; Electrophysiology (science); Elements; Endoplasmic Reticulum; Environment; Event; Fertilization; Fetus; Gene Expression; Genes; Genetic; Growth; HIV; Image; Immunocompromised Host; Individual; Infection; Invaded; Ion Channel; Ions; Knowledge; Life; Lipid Bilayers; Lytic Phase; Malaria; Mammalian Cell; Modeling; Molecular; Morbidity - disease rate; Muscle Contraction; Names; Neurotransmitters; Nifedipine; Parasites; Parasitology; Pathogenesis; Pathogenicity; Pathology; Pathway interactions; Persons; Physiological; Plants; Play; Population; Proteins; Proteomics; Publishing; Regulation; Research; Role; Rupture; Signal Pathway; Signal Transduction; Source; System; Techniques; Therapeutic; Tissues; Toxoplasma gondii; Toxoplasmosis; Training; Travel; Virulence; Work; cell motility; extracellular; fungus; insight; member; molecular sequence database; mortality; novel; novel therapeutics; opportunistic pathogen; organ transplant recipient; pathogen; receptor; therapeutic target; tool; trait; voltage

PROJECT SUMMARY/ABSTRACT Ca2+ ions impact almost every aspect of cellular life. Ca2+ signaling begins with the opening of Ca2+ channels in either the plasma membrane (PM) or the endoplasmic reticulum (ER) and results in a dramatic increase in the physiologically low (<100 nM) cytosolic Ca2+ levels. The temporal and spatial Ca2+ levels are exquisitely regulated and enable the precise and specific activation of critical biological processes like changes in gene expression, cell differentiation, muscle contraction, fertilization, or secretion of neurotransmitters to name a few. Ca2+ signaling regulates pathogenic pathways of apicomplexan parasites like Toxoplasma gondii which infects approximately one third of the world’s population. T. gondii is an opportunistic pathogen of immunocompromised patients like HIV-infected individuals, fetuses, and organ transplant recipients. As an obligate intracellular pathogen, T. gondii replicates inside cells and the clinical manifestations of toxoplasmosis are a direct result of its growth within cells and its dissemination. T. gondii relies on Ca2+ signals for the stimulation of specific features of its infection cycle and several Ca2+ signaling elements play essential roles in its parasitic cycle. However, the fundamental elements that initiate Ca2+ signals in T. gondii are largely unknown yet are likely essential for its viability and virulence. Discovery and characterization of the molecules that initiate Ca2+ signaling in T. gondii are hence central for the understanding of its pathogenesis. Active egress of T. gondii from host cells is critical for dissemination of the infection and our prior work has provided conclusive evidence that there is a cytosolic Ca2+ peak preceding egress. This parasitic cytosolic increase arises from release from intracellular stores, likely the endoplasmic reticulum. It is puzzling, however, that intracellular parasites replicate surrounded by the low host cytosolic Ca2+ but still store sufficient Ca2+ in their ER to trigger egress. Upon host cell rupture, extracellular Ca2+ influx across the PM contributes to a second Ca2+ peak enhancing motility of parasites, which then exit and seek another host cell to invade. Our hypothesis is that PM Ca2+ entry is essential for refilling of intracellular Ca2+ stores, and both intra and extracellular sources are necessary for triggering the cascade of molecular events that lead to the stimulation of parasitic functions like motility, secretion of adhesins, invasion of host cells, egress and dissemination. In this proposal we aim to characterize the proteins that enable PM Ca2+ influx. There is almost no information about the functional characteristics and roles of Ca2+ channels in T. gondii. This lack of knowledge could be due to lack of appropriate tools, techniques, and training in electrophysiology within the molecular parasitology field. We address this void with a collaboration with a mammalian electrophysiologist and a modeler. Channels are critical for the successful unicellular life of parasites, and they could be targeted by many therapeutically useful agents. Ion channels remain significantly under-exploited as therapeutic targets, even more so as antiparasitic agents.

项目概要/摘要 Ca2+ 离子几乎影响细胞生命的各个方面。 Ca2+ 信号传导始于 Ca2+ 通道的开放 在质膜 (PM) 或内质网 (ER) 中，导致 生理学低 (<100 nM) 胞质 Ca2+ 水平。时空 Ca2+ 水平精美 调节并实现关键生物过程（如基因变化）的精确和特异性激活 表达、细胞分化、肌肉收缩、受精或神经递质的分泌 很少。 Ca2+ 信号传导调节顶复门寄生虫（如弓形虫）的致病途径 感染世界上大约三分之一的人口。弓形虫是一种机会致病菌 免疫功能低下的患者，如艾滋病毒感染者、胎儿和器官移植受者。作为一个 专性细胞内病原体弓形虫在细胞内复制及其临床表现 弓形虫病是其在细胞内生长和传播的直接结果。弓形虫依赖 Ca2+ 信号 对于刺激其感染周期的特定特征，一些 Ca2+ 信号元件起着至关重要的作用 其寄生循环中的作用。然而，弓形虫中启动 Ca2+ 信号的基本元素主要是 未知但可能对其生存能力和毒力至关重要。分子的发现和表征 因此，在弓形虫中启动 Ca2+ 信号传导对于理解其发病机制至关重要。活跃出口 从宿主细胞中分离弓形虫对于感染的传播至关重要，我们之前的工作已经证明 确凿的证据表明在流出之前存在胞质 Ca2+ 峰值。这种寄生细胞质增加 来自细胞内储存的释放，可能是内质网。然而令人费解的是， 细胞内寄生虫在宿主胞质 Ca2+ 含量较低的情况下进行复制，但仍能在其体内储存足够的 Ca2+ ER 触发出口。宿主细胞破裂后，细胞外 Ca2+ 穿过 PM 流入，导致第二次 Ca2+ 峰值增强寄生虫的运动性，然后寄生虫退出并寻找另一个宿主细胞进行入侵。我们的假设 PM Ca2+ 进入对于补充细胞内 Ca2+ 储备以及细胞内和细胞外来源至关重要 对于触发导致寄生功能刺激的分子事件级联是必要的 如运动、粘附素的分泌、宿主细胞的侵入、排出和传播。在本提案中，我们的目标是 表征使 PM Ca2+ 流入的蛋白质。几乎没有关于功能的信息 弓形虫Ca2+通道的特征和作用。这种知识的缺乏可能是由于缺乏适当的 分子寄生虫学领域的电​​生理学工具、技术和培训。我们解决这个问题 与哺乳动物电生理学家和建模师的合作无效。渠道对于企业来说至关重要 寄生虫成功的单细胞生命，并且它们可以成为许多治疗上有用的药物的目标。离子 通道作为治疗靶点的开发仍然严重不足，作为抗寄生虫药物更是如此。