ENDOPLASMIC RETICULUM OF TRYPANOSOMATIDS

描述（由申请人提供）：锥虫表面蛋白（例如，变异表面糖蛋白，布氏锥虫的VSG）对于建立感染是关键的。输入内质网（ER）是这些多肽进入胞外途径的关键步骤。因此，ER蛋白转位是寄生虫体内非常重要的途径。我们的长期目标是表征锥虫ER输入机制，因为ER蛋白输入的最基本特性尚未建立。真核生物的蛋白质转运到ER中依赖于N-末端信号序列、信号识别颗粒（SRP）、SRP受体（5 R）和易位子（由5ec 61 p复合物形成）。蛋白质的输入既可以发生在共进化过程中，也可以发生在进化后，人们普遍认为信号肽在所有的生物家族中是可以互换的。布氏杆菌和利什曼原虫不能有效地（如果有的话）与脊椎动物微粒体输入机制一起操作。我们的近期目标是开发一种能够从锥虫输入蛋白质的体外系统，因为犬微粒体系统对于此目的毫无价值。为此，T.布鲁氏菌将被分离，并优化VSG的进口。一个T的可用性。布氏锥虫微粒体系统将有助于表征（i）锥虫信号肽的特性，（ii）描绘锥虫的生化特性。（iii）鉴定宿主与T.布氏杆菌易位机制。了解锥虫和哺乳动物宿主之间信号肽选择的种属特异性的分子基础是重要的，因为这些信息可能为抗锥虫药物的合理开发提供线索。

DESCRIPTION (provided by the applicant): Trypanosomatid surface proteins (e.g., variant surface glycoprotein, VSG of Trypanosoma brucei) are critical for establishment of infections. Import into the endoplasmic reticulum (ER) is the committed step or entry into the exocytic pathway for these polypeptides. Hence, ER protein translocation is a very important pathway in the parasite. Our long-term objective is to characterize the trypanosomatid ER import machinery, as most fundamental properties of the ER protein import have not been established. Translocation of proteins into the ER of eukaryotes is dependent on an N-terminal signal sequence, signal recognition particle (SRP), SRP receptor (5R), and a translocon (formed by the 5ec61 p complex). Protein import takes place either co-translationally or post-translationally, and it is widely held that signal peptides are interchangeable across all biological families We have found species-specificity in signal sequence recognition: signal peptides from T. brucei and Leishmania do not operate efficiently (if at all) with vertebrate microsomal import machineries. Our immediate goal is to develop an in vitro system that is capable of importing proteins from trypanosomes, since the canine microsomal system is worthless for this purpose. To this end, membranes from T. brucei will be fractionated, and optimized for import of VSG. Availability of a T. brucei microsomal system will facilitate characterization of (i) properties of trypanosome signal peptides, (ii) delineation of the biochemical properties of the T. brucei translocation system, and (iii) identification of molecular differences between host and T. brucei translocation machineries. Understanding the molecular basis of the species-specificity of signal peptide selection between a trypanosome and a mammalian host is important, because the information may provide leads for rationale development of anti-trypanosome drugs.