TRYPANOSOME VARIANT SURFACE GLYCOPROTEIN

锥虫变体表面糖蛋白

• 批准号: 3131325
• 负责人: PAUL T ENGLUND
• 金额: $ 24.59万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1984
• 资助国家: 美国
• 起止时间: 1984-05-01 至 1997-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3131325
• 关键词: Trypanosoma; cell free system; enzyme mechanism; ethanolamines; fatty acid analog; fatty acid binding protein; fatty acylation; gene mutation; genetic recombination; glycolipids; glycoproteins; intracellular transport; laboratory mouse; laboratory rat; lipid biosynthesis; membrane lipids; microorganism culture; microorganism genetics; microorganism metabolism; molecular cloning; myristates; phosphatidylinositols; phospholipase C; protein purification; protozoal antigen; surface antigens; transfection; transferase

African trypanosomes are parasitic protozoa which are responsible for human and animal diseases. They inhabit their host's bloodstream, and they evade immune defenses by antigenic variation. Antigenic variation is mediated by the variant surface glycoprotein (VSG), which forms a coat covering the entire cell. During antigenic variation, the parasite synthesizes a new VSG, with a different amino acid sequence, exchanging its old coat for a new one. Trypanosomes have the genetic potential to synthesize hundreds of different VSG molecules, and therefore they can maintain a chronic infection. This research involves the biochemistry of VSG, focusing particularly on the myristate-containing glycosyl phosphatidylinositol (GPI) which anchors it to the plasma membrane. The GPI is synthesized as a precursor, glycolipid A, which is linked to the C-terminus of the newly-made VSG. Previous studies, using a cell free system, have revealed the pathway for biosynthesis of glycolipid A and the remodeling mechanism by which myristate is incorporated into this structure. Proposed studies consist of further analysis of the mechanism by which myristate is incorporated into the GPI and also the mechanism for incorporation of its phosphoethanolamine. Other studies will focus on trypanosome myristate metabolism, with special emphasis on mechanisms of myristate uptake and intracellular transport to the site of GPI biosynthesis. There will be additional investigations of myristate analogs which are selectively toxic to African trypanosomes, possible because they interfere with VSG biosynthesis or function. Earlier studies on GPI biosynthesis and myristoylation have involved crude membrane fractions; however, a more comprehensive understanding of these processes will require enzyme purification. Purification will also allow cloning of the genes regulating GPI biosynthesis and myristoylation, and new genetic techniques will allow specific mutation of these genes in trypanosomes. This genetic analysis will allow biological studies of the effect of defective GPI biosynthesis or myristoylation. The same genetic approach will be applied to GPI-specific phospholipase C (GPI-PLC), an enzyme which cleaves the VSG anchor.

非洲锥虫是寄生原生动物，负责 人类和动物疾病。 他们居住在宿主的血液中， 他们通过抗原变异来逃避免疫防御能力。 抗原变异 由形成A的变体表面糖蛋白（VSG）介导 覆盖整个牢房的外套。 在抗原变异期间，寄生虫 合成具有不同氨基酸序列的新VSG，交换 它的新外套。 锥虫具有遗传潜力 合成数百个不同的VSG分子，因此可以 保持慢性感染。 这项研究涉及VSG的生物化学，特别关注 含肉豆蔻酸酯的糖基磷脂酰肌醇（GPI） 将其固定在质膜上。 GPI合成为 前体，糖脂A，与C末端有关 新制造的VSG。 以前的研究使用无细胞系统具有 揭示了糖脂A和重塑的生物合成的途径 将肉豆蔻酸酯纳入该结构的机制。 拟议的研究包括对机制的进一步分析 肉豆蔻酸盐已纳入GPI，也是 掺入其磷酸乙醇胺。 其他研究将重点 锥虫肉毒体的新陈代谢，特别强调了机制 肉豆蔻酸酯的摄取和细胞内转运到GPI部位 生物合成。 将对Myristate进行其他调查 对非洲锥虫有选择性毒性的类似物，可能 因为它们会干扰VSG生物合成或功能。 较早 GPI生物合成和肉豆蔻酰化的研究涉及粗略 膜分数；但是，对这些的更全面理解 过程将需要酶纯化。 纯化也将 允许克隆调节GPI生物合成和 肉豆蔻酰化和新的遗传技术将允许特定突变 这些基因在锥虫中。 这种遗传分析将允许 GPI生物合成有缺陷的作用的生物学研究或 Myristoylation。 相同的遗传方法将应用于 GPI特异性磷脂酶C（GPI-PLC），一种裂解VSG的酶 锚。