Weiss L M
Department of Medicine, Albert Einstein College of Medicine, 1300 Morris Park Avenue Room 504 Forchheimer Building, Bronx, New York, NY 10461, USA.
Acta Trop. 2001 Feb 23;78(2):89-102. doi: 10.1016/s0001-706x(00)00178-9.
Microsporidia are eukaryotic spore forming obligate intracellular protozoan parasites first recognized over 100 years ago. These organisms infect all of the major animal groups and are now recognized as opportunistic pathogens of humans. Microsporidian spores are common in the environment and microsporidia pathogenic to humans have been found in water supplies. The genera Nosema, Vittaforma, Brachiola, Pleistophora, Encephalitozoon, Enterocytozoon, Septata (reclassified to Encephalitozoon) and Trachipleistophora have been found in human infections. These organisms have the smallest known eukaryotic genomes. Microsporidian ribosomal RNA sequences have proven useful as diagnostic tools as well as for phylogenetic analysis. Recent phylogenetic analysis suggests that Microsporidia are related to the fungi. These organisms are defined by the presence of a unique invasion organelle consisting of a single polar tube that coils around the interior of the spore. All microsporidia exhibit the same response to stimuli, that is, the polar tube discharges from the anterior pole of the spore in an explosive reaction. If the polar tube is discharged next to a cell, it can pierce the cell and transfer its sporoplasm into the cell. A technique was developed for the purification of polar tube proteins (PTPs) using differential extraction followed by reverse phase HPLC. This method was used to purify the PTPs from Glugea americanus, Encephalitozoon cuniculi, Enc. hellem and Enc. intestinalis. These PTPs demonstrate conserved characteristics such as solubility, hydrophobicity, mass, proline content and immunologic epitopes. The major PTP gene from Enc. cuniculi and Enc. hellem has been cloned and expressed in vitro. The gene sequences support the importance of ER and in the formation of the polar tube as suggested by morphologic studies. Analysis of the cloned proteins also indicates that secondary structural characteristics are conserved. These characteristics are probably important in the function of this protein during the eversion/assembly of the polar tube and in providing elasticity and resiliency for sporoplasm passage.
微孢子虫是形成孢子的真核生物，属于专性细胞内原生动物寄生虫，100多年前首次被发现。这些生物感染所有主要动物群体，现在被认为是人类的机会性病原体。微孢子虫孢子在环境中很常见，在供水系统中也发现了对人类致病的微孢子虫。在人类感染中发现了Nosema、Vittaforma、Brachiola、Pleistophora、Encephalitozoon、Enterocytozoon、Septata（重新分类为Encephalitozoon）和Trachipleistophora属。这些生物拥有已知最小的真核生物基因组。微孢子虫核糖体RNA序列已被证明可作为诊断工具以及用于系统发育分析。最近的系统发育分析表明微孢子虫与真菌有关。这些生物的特征是存在一个独特的入侵细胞器，由一根围绕孢子内部盘绕的单极管组成。所有微孢子虫对刺激都表现出相同的反应，即极管以爆发反应从孢子的前端排出。如果极管在细胞旁边排出，它可以刺穿细胞并将其孢质转移到细胞中。开发了一种使用差异提取随后进行反相高效液相色谱法来纯化极管蛋白（PTP）的技术。该方法用于从美洲Glugea、兔脑炎微孢子虫、海伦脑炎微孢子虫和肠脑炎微孢子虫中纯化PTP。这些PTP表现出保守的特性，如溶解性、疏水性、质量、脯氨酸含量和免疫表位。来自兔脑炎微孢子虫和海伦脑炎微孢子虫的主要PTP基因已被克隆并在体外表达。基因序列支持了内质网在极管形成中的重要性，这正如形态学研究所表明的那样。对克隆蛋白的分析也表明二级结构特征是保守的。这些特征可能在极管外翻/组装过程中该蛋白的功能以及为孢质通过提供弹性和韧性方面很重要。
