Characterization of potassium channels in the human parasite Trypanosoma cruzi

人类寄生虫克氏锥虫钾通道的表征

• 批准号: 8353272
• 负责人: Veronica Jimenez
• 金额: $ 9.12万
• 依托单位: UNIVERSITY OF GEORGIA
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-05-01 至 2013-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8353272
• 关键词: Ablation; Benznidazole; Blood Circulation; Calcium-Activated Potassium Channel; Cell Proliferation Regulation; Cell membrane; Cell physiology; Cells; Chagas Disease; Complement; Complex; Congestive Heart Failure; Disease; Electrodes; Environment; Epidemiology; FDA approved; Feces; Financial compensation; Heart Diseases; Homologous Gene; Human; Immigration; Immunofluorescence Immunologic; Insect Vectors; Insecta; Ion Channel; Ions; Kidney; Knock-out; Laboratories; Latin America; Life; Life Cycle Stages; Light; Lipids; Liposomes; Maintenance; Membrane; Membrane Potentials; Modification; Molecular; Molecular Profiling; Nifurtimox; Oocytes; Osmolar Concentration; Osmoregulation; Parasites; Pathology; Pharmaceutical Preparations; Physiological; Play; Potassium Channel; Poverty; Process; Property; Proteins; Regulation; Role; Site; Site-Directed Mutagenesis; Staging; Stress; Trypanosoma cruzi; Urine; Work; Xenopus laevis; cellular imaging; coping; environmental change; extracellular; genetic manipulation; gutted vector; in vivo; inward rectifier potassium channel; mitochondrial membrane; new therapeutic target; overexpression; patch clamp; public health relevance; reconstitution; response; rural area; success; therapeutic target; vector; voltage clamp

DESCRIPTION (provided by applicant): Chagas disease is a zoonotic tropical pathology, caused by the protozoan parasite Trypanosoma cruzi. Endemic in Latin America, it is one of the leading causes of congestive heart failure in the world. Historically associated with poverty in rural areas, immigration and relocation of the vectors are changing the epidemiology of the disease, as evidenced by a substantial increase in the number of cases in the US. Treatment is restricted to nifurtimox and benznidazole, both of which are relatively toxic, have limited efficac and are not approved by the FDA. Our laboratory has been working on the rational search for chemotherapeutic treatments for Chagas disease that can selectively target the parasite without compromising human cells. Ion channels are potential targets for selective drugs against a broad range of diseases because they are responsible for essential cellular functions like plasma membrane and mitochondrial membrane potential maintenance, pH regulation, cell proliferation, and adaptation to environmental changes including osmoregulation. During its life cycle, the parasite encounters extreme fluctuations in ionic concentrations, osmolarities and pHs. Previous studies in our laboratory suggested that in T. cruzi, K+ channels are important components of the regulatory mechanisms that maintain the plasma membrane potential, intracellular pH and osmolarity. It has also been demonstrated that trypomastigotes, the infective forms of the parasite, are particularly sensitive to changes in extracellular K+ concentration while epimastigotes and amastigotes are less responsive to this ion. In T. cruzi, we have identified sequences encoding for putative inward rectifier (TcKir) and calcium-activated K+ channels (TcCAKC). They have conserved functional domains, but limited identity with human homologs (<15%) making them potential selective pharmacological targets against the parasite. We propose that ion channels play an important role in sensing and adaptation to environmental conditions in T. cruzi. We propose that different types of K+ channels integrate a homeostatic network that allows the parasite to detect and respond to changes in osmotic and ionic conditions. Fundamental processes like differentiation and invasion can be regulated by modification of the ionic concentrations determining the success of the parasite in infecting new hosts. Analysis of T. cruzi potassium channels expression profiles and localization, complemented with electrophysiological studies will shed light about how these proteins work. Genetic manipulation of the level of expression and phenotypic analysis in vivo will demonstrate the physiological role of potassium channels in the parasite and will help to establish their potential as therapeutic targets. Public Health Relevance: Chagas disease is a tropical pathology, caused by the parasite Trypanosoma cruzi. Endemic in Latin America, it is one of the leading causes of heart disease in the world. Historically associated with poverty in rural areas, immigration and relocation of th insect that transmits the disease are changing the epidemiology, as evidenced by a substantial increase in the number of cases in the US. Only two drugs are available for the treatment of Chagas disease, both of which are relatively toxic and have limited efficacy. We have been working on the rational search for chemotherapeutic alternatives that can selectively target the parasite without compromising human cells. Understanding of the adaptation and survival mechanisms that the parasite uses to cope with environmental changes will contribute to the identification of new therapeutic targets.

描述（由申请人提供）：恰加斯病是一种人畜共患的热带疾病，由原生动物寄生虫克氏锥虫引起。它在拉丁美洲流行，是世界上导致充血性心力衰竭的主要原因之一。从历史上看，该病与农村地区的贫困有关，病媒的移民和重新安置正在改变该病的流行病学，美国病例数量的大幅增加就是证据。治疗仅限于硝呋替莫和苯并硝唑，这两种药物都是相对有毒的，疗效有限，并且没有得到FDA的批准。我们的实验室一直致力于寻找恰加斯病的化疗方法，可以选择性地针对寄生虫而不损害人体细胞。离子通道是治疗多种疾病的选择性药物的潜在靶点，因为它们负责基本的细胞功能，如质膜和线粒体膜电位维持、pH调节、细胞增殖以及对环境变化的适应，包括渗透调节。在其生命周期中，寄生虫会遇到离子浓度、渗透压和ph值的极端波动。我们实验室之前的研究表明，克氏t细胞中，K+通道是维持质膜电位、细胞内pH和渗透压的调节机制的重要组成部分。研究还表明，这种寄生虫的感染形式——锥马鞭毛虫对细胞外K+浓度的变化特别敏感，而粘马鞭毛虫和无尾鞭毛虫对这种离子的反应较弱。在T. cruzi中，我们已经确定了编码假定的内向整流（TcKir）和钙活化K+通道（TcCAKC）的序列。它们具有保守的功能域，但与人类同源物的同一性有限（<15%），使它们成为对抗寄生虫的潜在选择性药理靶点。我们认为离子通道在T. crozi对环境条件的感知和适应中起着重要作用。我们提出，不同类型的K+通道整合了一个稳态网络，使寄生虫能够检测和响应渗透和离子条件的变化。分化和入侵等基本过程可以通过离子浓度的改变来调节，离子浓度的改变决定了寄生虫感染新宿主的成功。分析克氏T. crozi钾通道的表达谱和定位，辅以电生理学研究，将揭示这些蛋白是如何工作的。体内表达水平的遗传操作和表型分析将证明钾通道在寄生虫中的生理作用，并将有助于确定其作为治疗靶点的潜力。