Structure and Development of Oocyst and Sporocyst Walls

卵囊和孢子囊壁的结构和发育

• 批准号: 9206440
• 负责人: John C. Samuelson
• 金额: $ 40.73万
• 依托单位: BOSTON UNIVERSITY MEDICAL CAMPUS
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2020-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9206440
• 关键词: Acid Fast Bacillae Staining Method; Acids; Adult; Binding; Binding Proteins; Brain; Cattle; Cell division; Cells; Chemicals; Chickens; Chronic; Coccidia; Complex; Cryptosporidium; Cryptosporidium parvum; Cyst; Development; Diarrhea; Disease; Eimeria; Elements; Felis catus; Fetus; Future; Genes; Genus Mycobacterium; Glucans; Glycoproteins; Goals; Growth; Hand; Haploidy; Histology; Human; Hydrolase; In Vitro; Infant; Infection; Knock-out; Lead; Lectin; Life; Link; Lipid Bilayers; Lipid Binding; Lipids; Meiosis; Membrane; Methods; Modeling; Morphology; Mus; Muscle; Oocysts; Oral; Organic solvent product; Parasites; Pathogenesis; Permeability; Pharmaceutical Preparations; Plant Lectins; Plants; Polymers; Property; Proteins; Reproduction spores; Route; Shapes; Sheep; Sporocysts; Sporozoites; Structure; Surface; Testing; Tetanus Helper Peptide; Thick; Tissues; Toxoplasma; Toxoplasma gondii; Triglycerides; dityrosine; fungus; glucan synthase; immunosuppressed; inhibitor/antagonist; killings; mycobacterial; novel; nuclear division; pathogen; public health relevance; scaffold; sugar; transmission process

 DESCRIPTION (provided by applicant): Coccidian parasites are important human pathogens that cause severe diarrhea in infants (Cryptosporidium parvum) and disseminated infections in fetuses (Toxoplasma gondii). Both Cryptosporidium and Toxoplasma cause chronic infections in immunosuppressed adults. Oocysts are infectious stages of coccidia, which are spread by the fecal-oral route. While numerous proteins have been identified in oocyst walls (e.g. Cryptosporidium oocyst wall proteins (COWPs)), there are no models for how oocyst walls Toxoplasma and Cryptosporidium are assembled. Here we show that the inner layer of the oocyst wall of Toxoplasma is a porous scaffold of fibrils of ß-1,3-glucan, a sugar polymer present in fungal walls. While glucan synthase inhibitors (echinocandins) kill fungi, these drugs arrest the development of oocyst walls of Eimeria, a chicken parasite that closely models Toxoplasma oocysts. The outer layer of the oocyst wall of Toxoplasma contains acid-fast lipids like those that cover the surface of mycobacteria. Organic solvents release oocyst wall lipids, which are triglycerides with polyhydroxy fatty acyl chain like those of the waxy cuticle of plants. The oocyst wall of Cryptosporidium contains acid-fast lipids but does not contain glucan fibrils. Instead the inner layer of the Cryptosporidium wall contains fibrils of a novel sugar polymer. Proposed studies in Aim 1 test a two-layer model of the Cryptosporidium oocyst wall. We will identify glycoproteins in the outer rigid bilayer of wall that also contains acid-fast lipids. We wll determine the chemical composition of fibrils in the inner layer of the oocyst wall and determine whether COWPS are lectins that bind these sugar fibrils. Proposed studies in Aim 2 focus on the structure and development of the oocyst wall of Toxoplasma. We will identify oocyst wall proteins and determine whether those in the outer, acid-fast layer have lipid-binding properties, while those in the inner layer are lectins that bind to fibrils of ß-1,3-glucan. We will test the dea that ß-1,3-glucan, acid-fast lipids, and wall proteins are made in separate secretory compartments during development of the oocyst wall, and we will identify cytoskeletal elements important for secretion and for determining oocyst wall shape. Proposed studies in Specific Aim 3 focus on the structure and development of the sporocyst wall of Toxoplasma. We will test the hypothesis that sporocyst wall of Toxoplasma is structural similar to the Cryptosporidium oocyst wall, which is also acid-fast, is missing fibrils of ß-1,3-glucan, and contains sporozoites. We tet the idea that sporulation (development of the sporocyst wall and sporozoites) differs markedly from vegetative growth by tachyzoites, which is well-characterized. In particular, nuclear division is uncoupled from cell division; sporoblast formation is by binary fission rather than budding (endodyogeny); and each sporozoite develops synchronously but independently from others, using an IMC complex similar to that of tachyzoites.

 描述（由申请人提供）：球虫寄生虫是重要的人类病原体，可引起婴儿严重腹泻（小隐孢子虫）和胎儿播散性感染（弓形虫）。隐孢子虫和弓形虫都会导致免疫抑制的成年人慢性感染。卵囊是球虫的感染阶段，通过粪口途径传播。虽然在卵囊壁中发现了许多蛋白质（例如隐孢子虫卵囊壁蛋白（COWP）），但还没有弓形虫和隐孢子虫卵囊壁如何组装的模型。 在这里，我们发现弓形虫卵囊壁的内层是β-1,3-葡聚糖原纤维的多孔支架，β-1,3-葡聚糖是真菌壁中存在的一种糖聚合物。虽然葡聚糖合酶抑制剂（棘白菌素）可以杀死真菌，但这些药物可以阻止艾美耳球虫卵囊壁的发育，艾美耳球虫是一种与弓形虫卵囊密切相关的鸡寄生虫。弓形虫卵囊壁的外层含有抗酸脂质，就像覆盖分枝杆菌表面的脂质一样。有机溶剂释放卵囊壁脂质，它们是具有多羟基脂肪酰基链的甘油三酯，类似于植物蜡质角质层的甘油三酯。 隐孢子虫的卵囊壁含有抗酸脂质，但不含葡聚糖原纤维。相反，隐孢子虫壁的内层含有一种新型糖聚合物的原纤维。 目标 1 中提出的研究测试了隐孢子虫卵囊壁的两层模型。我们将鉴定壁外刚性双层中的糖蛋白，该双层也含有抗酸脂质。我们将确定卵囊壁内层原纤维的化学成分，并确定 COWPS 是否是与这些糖原纤维结合的凝集素。 目标 2 中拟议的研究重点是弓形虫卵囊壁的结构和发育。我们将鉴定卵囊壁蛋白，并确定外层抗酸层中的蛋白是否具有脂质结合特性，而内层中的蛋白是否是与 ß-1,3-葡聚糖原纤维结合的凝集素。我们将测试在卵囊壁发育过程中，β-1,3-葡聚糖、抗酸脂质和壁蛋白是在单独的分泌室中产生的，并且我们将鉴定对分泌和确定卵囊壁形状重要的细胞骨架元素。 具体目标 3 中提出的研究重点是弓形虫孢子囊壁的结构和发育。我们将检验弓形虫孢子囊壁的结构与隐孢子虫卵囊壁相似的假设，隐孢子虫卵囊壁也是抗酸的，缺少 ß-1,3-葡聚糖原纤维，并且含有子孢子。我们认为孢子形成（孢子囊壁和子孢子的发育）与速殖子的营养生长明显不同，这是有充分特征的。特别是核分裂 与细胞分裂无关；孢子母细胞的形成是通过二元裂变而不是出芽（内生）；每个子孢子都同步发育，但独立于其他子孢子，使用类似于速殖子的 IMC 复合体。