CELL AND DEVELOPMENTAL BIOLOGY OF TRYPANOSOMATID PARASITES

人类病原体利什曼原虫的细胞和发育生物学， 相关的锥虫寄生虫作为模型进行了研究， 和细胞外寄生。 重点放在表征 寄生虫独特表膜的基本功能和基因结构 酶和相关蛋白质，以确定其在寄生虫中的作用 生存和发展。 从L. donovani（Ld）3 '-核苷酸酶/核酸酶（e'-NT/Nu）基因 将该基因的位点定位到单个约2.5Mb大小的Ld上 染色体，这也是目前在各种其他致病 利什曼原虫。 因此，该基因的基本结构已被 跨物种线保存。 营养诱导的过度表达 Ld 3 '-NT/Nu酶活性受两种酶的调节， 转录介导的事件和翻译后修饰 新合成的蛋白质 在同源游离体中 转染-表达研究中，Ld表面膜3 'NT/Nu为 转化为并表达为可溶的、酶活性的 通过从其跨膜锚结构域中删除跨膜结构域， 基因 在其他研究中，独特的Ld表面膜酸的基因 磷酸酶（MbAcP）的鉴定和表征。 一个MbAcP 用基因探针将该基因定位在一个约1.45 Mb大小的Ld染色体也存在于各种不同的染色体中， 致病性利什曼原虫物种表明，这种基本结构 基因在物种间也是保守的。 我们最近还 鉴定了一种新的38 kDa的表面膜核酸酶，存在于Ld pro 和无鞭毛体 根据其表面局部化和本构关系， 表达，我们认为这种酶必须发挥重要作用， 寄生虫获得宿主衍生的核碱基。 最后，基因 对编码钙网蛋白的利什曼同系物进行了表征。其 表达的蛋白质具有多种功能，包括高Ca++ 结合和自身激酶活性，最重要的是， 同源利什曼醛的磷酸化非依赖性结合活性 RNA。 后者表明钙网蛋白可能在RNA中起作用， 处理、运输或保护这些寄生虫。

The cell and developmental biology of the human pathogen, Leishmania, and related trypanosomatid parasites are investigated as models of both intra and extracellular parasitism. Emphasis is placed on characterizing the basic functions and gene structure of unique parasite surface membrane enzymes and related proteins toward defining their roles in parasite survival and development. A probe from the L. donovani(Ld)3'-nucleotidase/nuclease (e'-NT/Nu) gene was used to map the locus of this gene to a single about 2.5 Mb sized Ld chromosome which was also present in a variety of other pathogenic Leishmania species. Thus, the basic structure of this gene has been conserved across species lines. The nutrient-induced over-expression of Ld 3'-NT/Nu enzyme activity ws shown to be regulated by both transcriptionally mediated events and posttranslational modification of the newly synthesized protein. In homologous episomal transfection-expression studies, the Ld surface membrane 3'NT/Nu was converted into, and expressed as, a soluble, enzymatically active secretory protein by deleting the transmembrane anchor domain from its gene. In other studies, the gene for the unique Ld surface membrane acid phosphatase (MbAcP) was identified and characterized. An MbAcP gene-probe was used to map the locus of this gene to a single about 1.45 Mb sized Ld chromosome which was also present in various different pathogenic Leishmania species indicating that the basic structure of this gene has also been conserved across species boundaries. We also recently identified a new 38 kDa surface membrane nuclease present in both Ld pro and amastigotes. Based on its surface localization and constitutive expression, we assume that this enzyme must play an essential role in parasite acquisition of host-derived nucleo-bases. Finally, the gene encoding the leishmanial homolog of calreticulin was characterized. Its expressed protein possessed multiple functions including both high Ca++ binding and autokinase activities and, most significantly, phosphorylation-independent binding activity for homologous leishmanial RNAs. The latter suggests that calreticulin may play a role in RNA processing, transport or protection in these parasites.