Cholesterol Uptake by Cryptosporidium

隐孢子虫摄取胆固醇

• 批准号: 7749888
• 负责人: Isabelle Coppens
• 金额: $ 20.5万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-06-25 至 2011-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7749888
• 关键词: 3-hydroxy-3-methylglutaryl-coenzyme A; AIDS/HIV problem; ATP-Binding Cassette Transporters; Abbreviations; Acquired Immunodeficiency Syndrome; Amino Acids; Binding; Biological Models; Brush Border; Cell membrane; Cells; Cholesterol; Cholesterol Esters; Cholesterol Homeostasis; Collection; Complement component C1s; Complex; Cryptosporidiosis; Cryptosporidium; Cytoplasm; Data; Development; Disease; Drug Delivery Systems; Drug resistance; Endocytosis; Endoplasmic Reticulum; Ensure; Enterocytes; Environment; Epithelial; Epithelial Cells; Excision; Exhibits; Gastrointestinal tract structure; Genes; Goals; Growth; Homologous Gene; Immunocompromised Host; Individual; Infection; Intake; Intercept; Intestines; Invaded; Life; Light; Lipids; Lipoproteins; Location; Low Density Lipoprotein Receptor; Low-Density Lipoproteins; Mammalian Cell; Mammals; Membrane; Modification; Molecular; Movement; Nature; Nuclear Pore Complex; Nucleotides; Nutrient; Oocysts; Opportunistic Infections; Organelles; Organism; Parasites; Pathogenicity; Pathway interactions; Patients; Plasma; Plasmodium; Proteins; Relative (related person); Reliance; Reproduction; Resources; Role; Serum; Site; Small Intestines; Source; Sporozoites; Staging; Starvation; Steroids; Sterol O-Acyltransferase; Sterols; Surface; Thin Layer Chromatography; Toxoplasma gondii; Vacuole; Water; base; chemotherapy; cholesterol absorption; cholesterol biosynthesis; cholesterol trafficking; citrate carrier; dehydroergosterol; drug standard; experience; extracellular; inter-alpha-inhibitor; intraepithelial; meetings; microbial; novel; novel strategies; oxysterol binding protein; parasite genome; pathogen; permease; public health relevance; receptor mediated endocytosis; stem; uptake

DESCRIPTION (provided by applicant): Cryptosporidiosis is universally recognized as one of the most serious opportunistic infections that complicates AIDS. Cryptosporidium infection begins with microbial invasion of small intestinal epithelial cells (enterocytes), in which the parasite creates a peculiar niche that sequesters itself from the intestinal lumen and the host cell's cytoplasm. After amplification, endogenous parasites escape from the parasitophorous vacuole and spread throughout the epithelial surfaces of the gastrointestinal tract. No consistently reliable chemotherapy is available for the treatment of cryptosporidiosis. The need for identifying novel drug targets is imperative. Interactions of Cryptosporidium with enterocytes remain poorly characterized. Undeniably, this parasite must depend on various host cell resources since it has lost the ability to synthesize most basic metabolites. We demonstrated that Cryptosporidium developing in enterocytes contains significant amounts of cholesterol though it lacks the genes for cholesterol biosynthesis and modification. The parasite critically relies on host cholesterol for normal development since removal of cholesterol either from the medium or host cell intracellular pools, arrests its reproduction. Our overall goal is to decipher the mechanism/s for host cholesterol acquisition by Cryptosporidium. We hypothesize that the choice of enterocytes as the major sites for parasite replication may stem from the unique cholesterol transport and synthesis activities of these cells. Cryptosporidium must be equipped to intercept host cholesterol, either provided exogenously by the plasma and/or the gut, or synthesized in enterocytes. Specific Aim 1 will define the preferential source of host derived-cholesterol for Cryptosporidium and analyze the mechanisms of cholesterol delivery from the host enterocyte to the PV. We will investigate the contribution of i) the plasma low-density lipoprotein receptor-mediated endocytosis, ii) the micellar cholesterol absorption by the permease Niemann-Pick C1-like 1, and iii) the cholesterol biosynthetic pathway, to parasite growth. We documented the presence of sterols on the parasite's plasma membrane and organelles indicating that Cryptosporidium is able to internalize host cholesterol to its cell interior. Specific Aim 2 will decipher the molecular machinery developed by Cryptosporidium to transport cholesterol from the parasite surface to organelles. We will focus on the characterization of two classes of surface-exposed sterol transporters, the ATP-binding cassette G1 transporter and Niemann-Pick C1 protein present in the parasite, for cholesterol trafficking. Our long-term objective is to provide novel approaches to treat cryptosporidiosis, based on blocking the parasite's intracellular development through cholesterol starvation. Exploration of the peculiarities of cholesterol uptake by Cryptosporidium will expose new vulnerabilities. Cryptosporidium may also provide a useful model system for throwing light on cholesterol homeostatic and dysregulatory pathways in mammalian enterocytes. PUBLIC HEALTH RELEVANCE: Cryptosporidium is one of the most troublesome agents of water-borne disease that cause life-threatening disease in HIV/AIDS patients. This parasite develops inside intestinal epithelial cells where it remains protected from the hostile gut environment and is supplied with host nutrients. We will study the mechanisms by which the parasite scavenges host cholesterol, in order to specifically interfere with the pathogen's supply of this essential lipid, thereby causing its growth arrest through starvation.

描述（由申请人提供）：隐孢子虫病被普遍认为是使艾滋病复杂化的最严重的机会性感染之一。隐孢子虫感染始于微生物入侵小肠上皮细胞（肠上皮细胞），其中寄生虫创建了一个特殊的生态位，将自身与肠腔和宿主细胞的细胞质隔离。扩增后，内源性寄生虫从寄生液泡中逸出并扩散到胃肠道的上皮表面。没有一致可靠的化疗方法可用于治疗隐孢子虫病。确定新药物靶点的需求势在必行。隐孢子虫与肠上皮细胞的相互作用仍知之甚少。不可否认，这种寄生虫必须依赖各种宿主细胞资源，因为它已经失去了合成最基本代谢物的能力。我们证明，在肠细胞中发育的隐孢子虫含有大量胆固醇，尽管它缺乏胆固醇生物合成和修饰的基因。该寄生虫严重依赖宿主胆固醇来正常发育，因为从培养基或宿主细胞胞内库中去除胆固醇会阻止其繁殖。我们的总体目标是破译隐孢子虫获取宿主胆固醇的机制。我们假设，选择肠上皮细胞作为寄生虫复制的主要位点可能源于这些细胞独特的胆固醇转运和合成活性。隐孢子虫必须具备拦截宿主胆固醇的能力，这些胆固醇要么由血浆和/或肠道外源提供，要么在肠细胞中合成。具体目标 1 将定义隐孢子虫宿主衍生胆固醇的优先来源，并分析胆固醇从宿主肠上皮细胞传递到 PV 的机制。我们将研究 i) 血浆低密度脂蛋白受体介导的内吞作用，ii) 渗透酶 Niemann-Pick C1-like 1 对胶束胆固醇的吸收，以及 iii) 胆固醇生物合成途径对寄生虫生长的贡献。我们记录了寄生虫质膜和细胞器上甾醇的存在，表明隐孢子虫能够将宿主胆固醇内化到其细胞内部。具体目标 2 将破译隐孢子虫开发的将胆固醇从寄生虫表面运输到细胞器的分子机制。我们将重点关注两类表面暴露的甾醇转运蛋白的表征，即寄生虫中存在的 ATP 结合盒 G1 转运蛋白和 Niemann-Pick C1 蛋白，用于胆固醇运输。我们的长期目标是提供治疗隐孢子虫病的新方法，其基础是通过胆固醇饥饿阻断寄生虫的细胞内发育。探索隐孢子虫吸收胆固醇的特性将暴露新的弱点。隐孢子虫还可能提供一个有用的模型系统，用于阐明哺乳动物肠细胞中胆固醇稳态和失调途径。公共卫生相关性：隐孢子虫是最麻烦的水传播疾病病原体之一，可导致艾滋病毒/艾滋病患者罹患危及生命的疾病。这种寄生虫在肠上皮细胞内发育，在那里它受到保护，免受恶劣的肠道环境的影响，并获得宿主的营养物质。我们将研究寄生虫清除宿主胆固醇的机制，以便特异性干扰病原体对这种必需脂质的供应，从而通过饥饿导致其生长停滞。