Cellular Biology Of Host/parasite Interactions

宿主/寄生虫相互作用的细胞生物学

基本信息

批准号：
7964301
负责人：
David (Ted) Hackstadt
金额：
$ 119.3万
依托单位：
NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES
依托单位国家：
美国
项目类别：
财政年份：
资助国家：
美国
起止时间：
至
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/7964301
关键词：
Actins Affinity Anabolism Animals Area Atherosclerosis Bacterial Infections Basic Science Blindness Carcinoma Cell Cycle Regulation Cell membrane Cells Cellular biology Centrosome Chlamydia Chlamydia Infections Chlamydia trachomatis Chlamydophila pneumoniae Chlamydophila psittaci Cholesterol Chromatin Chromosomal Instability Cytoplasm DNA DNA Structure Defect Development Dynein ATPase Eligibility Determination Endosomes Epidemiology Escherichia coli Event Failure Gene Expression Genetic Transcription Golgi Apparatus Growth Histone H1 Histone H1(s)Histones Human Immunologics Infection Intervention Link Malignant Neoplasms Malignant neoplasm of cervix uteri Medical Membrane Membrane Proteins Microtubule-Organizing Center Microtubules Minus End of the Microtubule Modification Molecular Molecular and Cellular Biology Motor Mutation Oncogenes Outcome Parasites Pathway interactions Play Positioning Attribute Process Proteins Proteomics RNA Recycling Regulation Role Screening procedure Sexually Transmitted Diseases Specificity Sphingomyelins Staging Study Section Time Trachoma Transferrin Translations Type III Secretion System Pathway Tyrosine Upper Respiratory Infections Vacuole Viral Weight extracellular human disease improved insight isoprenoid mevalonate novel pathogen protein protein interaction receptor response trafficking tumor

项目摘要

Chlamydia trachomatis is the etiological agent of several significant diseases of humans including trachoma, the leading cause of infectious blindness worldwide. It is also the most common cause of sexually transmitted disease in the USA. Other species of medical importance include C. pneumoniae, a causative agent of upper respiratory tract infections and possibly associated with atherosclerosis, and C. psittaci, which is primarily a pathogen of animals but occasionally is transmitted to humans. The Host-Parasite Interactions Section studies the fundamental cellular and molecular biology of intracellular pathogens. Efforts have been primarily with the genus Chlamydia and include two basic research areas: i.) the cellular interactions that promote entry and intracellular growth; primarily those controlled by secreted chlamydial effector proteins and ii.) global regulation of chlamydial gene expression by histone-like proteins. Establishment of a protected intracellular niche is a critical stage of the chlamydial developmental cycle. We have therefore focused much of our efforts over the last several years upon events occurring within these early stages of infection. Many of these events are unique among intracellular pathogens but common to the genus Chlamydia. The experimental approaches are heavily weighted toward cell biology, proteomics, and functional analysis of protein-protein interactions. An improved understanding of the distinct developmental stages and the cellular responses to them may suggest novel means of chemotherapeutic or immunologic intervention of chlamydial diseases. Chlamydiae occupy a unique vacuolar niche within the host cell. The chlamydial inclusion, unlike vacuoles containing other intracellular pathogens, is not interactive with endocytic vesicular trafficking pathways but is instead fusogenic with an incompletely understood exocytic pathway which delivers sphingomyelin and cholesterol from the Golgi apparatus to the plasma membrane. Entry into this pathway is an active process on the part of the chlamydiae as both de novo transcription and translation are required. Virtually all of these interactions are specific and localized to the inclusion. This specificity strongly suggests modification of the exposed inclusion membrane. Examples of cis-acting modifications to the nascent inclusion membrane include: evasion of lysosomal fusion, interactions with microtubules to deliver the nascent inclusion to the peri-Golgi region and microtubule organizing center, initiation of fusion with exocytic vesicular traffic from the Golgi apparatus, and recruitment of, but not fusion with, recycling endosomes containing transferrin and its receptor. Many of these interactions are temporally associated with the exposure of inclusion membrane proteins to the host cell cytoplasm by a chlamydial type III secretion system. Another example of a chlamydial proteins controlling localized events could include the recruitment of actin to promote entry. A type III secreted protein, termed Tarp, is translocated and tyrosine phosphorylated while EBs are still extracellular. Tarp has been associated with the actin recruitment which is required for chlamydial internalization. Chlamydial Tarp and the inclusion membrane proteins define at least two distinct stages in chlamydial development where secreted effectors may play important roles in defining the outcome of infection. In the case of Tarp, a pre-existing effector protein is secreted across the plasma membrane from extracellular EBs, while inclusion membrane proteins require de novo synthesis and are secreted across the inclusion membrane from the RBs within. Identification of secreted effector molecules and their functions will continue to provide insights into the many adaptations chlamydiae utilize as successful pathogens. Nascent chlamydial inclusions migrate towards the minus end of microtubules and aggregate at the MTOC utilizing the minus-end-directed microtubule motor dynein. This interaction leads to disruption of normal centrosomal positioning leading to centrosome number defects. The association of the chlamydial inclusion membrane with centrosomes leads to failures in centrosomal partitioning and/or cytokinesis.Centrosome supernumerary defects have been implicated in chromosome instability and loss of cell cycle control in early tumors and most aggressive carcinomas. The hypothesis that bacterial infections can contribute to cancer has endured for some time, but unlike viral induced cancers, specific oncogenes and molecular mechanisms have not been clearly established. The interaction of chlamydiae with dynein and centrosomes suggests a mechanism by which chlamydial infection, through induction of abnormal centrosome numbers, may be a contributing factor in chromosome instability ultimately leading to transformation and tumor development. Chlamydial histone H1-like proteins, Hc1 and Hc2, act as globalregulators of chlamydial gene expression by virtue of dramatic effects on DNA structure. The chlamydial histones are transcribed late in the developmental cycle as RBs differentiate to EBs. The mechanisms of histone release from the chlamydial chromatin at the initiation of development had been unknown. By utilizing a heterologous screening protocol in E. coli, we identified two novel means of regulation of histone activity. The affinity of histone for DNA appears to be disrupted early in infection by the synthesis of a small metabolite in the non-mevalonate pathway of isoprenoid biosynthesis. In the course of the screening procedure, we also identified a small regulatory RNA that specifically inhibits translation of Hc1.

沙眼衣原体是多种人类重大疾病的病原体，其中包括沙眼，它是全世界传染性失明的主要原因。它也是美国性传播疾病的最常见原因。其他具有医学重要性的物种包括肺炎衣原体（上呼吸道感染的病原体，可能与动脉粥样硬化有关）和鹦鹉热衣原体（主要是动物的病原体，但偶尔会传播给人类）。宿主-寄生虫相互作用部分研究细胞内病原体的基本细胞和分子生物学。主要致力于衣原体属，包括两个基础研究领域：i.) 促进进入和细胞内生长的细胞相互作用；主要由分泌的衣原体效应蛋白控制；ii.) 组蛋白样蛋白对衣原体基因表达的全局调节。受保护的细胞内生态位的建立是衣原体发育周期的关键阶段。因此，我们在过去几年中将大部分精力集中在感染早期阶段发生的事件上。其中许多事件在细胞内病原体中是独特的，但对于衣原体属来说是常见的。实验方法主要侧重于细胞生物学、蛋白质组学和蛋白质-蛋白质相互作用的功能分析。对不同发育阶段及其细胞反应的进一步了解可能会提出衣原体疾病化疗或免疫干预的新方法。衣原体在宿主细胞内占据独特的液泡生态位。与含有其他细胞内病原体的液泡不同，衣原体包涵体不与内吞性囊泡运输途径相互作用，而是与不完全了解的胞吐途径融合，该途径将鞘磷脂和胆固醇从高尔基体传递到质膜。对于衣原体而言，进入该途径是一个活跃的过程，因为需要从头转录和翻译。事实上，所有这些相互作用都是特定的并且局限于包容性。这种特异性强烈表明对暴露的包涵体膜进行了修饰。对新生包涵体膜进行顺式作用修饰的例子包括：逃避溶酶体融合、与微管相互作用以将新生包涵体递送至高尔基体周围区域和微管组织中心、与来自高尔基体的胞吐囊泡运输启动融合，以及募集含有转铁蛋白及其受体的再循环内体，但不与之融合。许多这些相互作用在时间上与衣原体 III 型分泌系统将包涵膜蛋白暴露于宿主细胞细胞质相关。衣原体蛋白控制局部事件的另一个例子可能包括招募肌动蛋白以促进进入。一种称为 Tarp 的 III 型分泌蛋白被易位并被酪氨酸磷酸化，而 EB 仍处于细胞外。 Tarp 与衣原体内化所需的肌动蛋白募集有关。衣原体 Tarp 和包涵膜蛋白定义了衣原体发育的至少两个不同阶段，其中分泌的效应器可能在确定感染结果中发挥重要作用。就 Tarp 而言，预先存在的效应蛋白从细胞外 EB 跨质膜分泌，而包涵膜蛋白需要从头合成，并从内部 RB 跨包涵膜分泌。分泌效应分子及其功能的鉴定将继续为衣原体作为成功病原体利用的许多适应性提供见解。新生衣原体包涵体向微管的负端迁移，并利用负端定向的微管运动动力蛋白在 MTOC 处聚集。这种相互作用会导致正常中心体定位的破坏，从而导致中心体数量缺陷。衣原体包涵体膜与中心体的结合导致中心体分隔和/或胞质分裂的失败。中心体多余缺陷与早期肿瘤和大多数侵袭性癌症中的染色体不稳定和细胞周期控制丧失有关。细菌感染可导致癌症的假说已经存在了一段时间，但与病毒诱发的癌症不同，具体的癌基因和分子机制尚未明确确定。衣原体与动力蛋白和中心体的相互作用表明，衣原体感染通过诱导异常中心体数量可能是染色体不稳定的一个促成因素，最终导致转化和肿瘤发展。衣原体组蛋白 H1 样蛋白 Hc1 和 Hc2 通过对 DNA 结构产生显着影响，充当衣原体基因表达的全局调节因子。当 RB 分化为 EB 时，衣原体组蛋白在发育周期后期转录。发育初期衣原体染色质释放组蛋白的机制尚不清楚。通过利用大肠杆菌中的异源筛选方案，我们确定了两种调节组蛋白活性的新方法。组蛋白与 DNA 的亲和力似乎在感染早期因类异戊二烯生物合成的非甲羟戊酸途径中小代谢物的合成而被破坏。在筛选过程中，我们还鉴定了一种特异性抑制 Hc1 翻译的小调控 RNA。