Urwyler Simon, Studer Erwin, Renggli Christina Kunz, Roditi Isabel
Institut für Zellbiologie, Universität Bern, Bern, Switzerland.
Mol Microbiol. 2007 Jan;63(1):218-28. doi: 10.1111/j.1365-2958.2006.05492.x.
A 'two coat' model of the life cycle of Trypanosoma brucei has prevailed for more than 15 years. Metacyclic forms transmitted by infected tsetse flies and mammalian bloodstream forms are covered by variant surface glycoproteins. All other life cycle stages were believed to have a procyclin coat, until it was shown recently that epimastigote forms in tsetse salivary glands express procyclin mRNAs without translating them. As epimastigote forms cannot be cultured, a procedure was devised to compare the transcriptomes of parasites in different fly tissues. Transcripts encoding a family of glycosylphosphatidyl inositol-anchored proteins, BARPs (previously called bloodstream alanine-rich proteins), were 20-fold more abundant in salivary gland than midgut (procyclic) trypanosomes. Anti-BARP antisera reacted strongly and exclusively with salivary gland parasites and a BARP 3' flanking region directed epimastigote-specific expression of reporter genes in the fly, but inhibited expression in bloodstream and procyclic forms. In contrast to an earlier report, we could not detect BARPs in bloodstream forms. We propose that BARPs form a stage-specific coat for epimastigote forms and suggest renaming them brucei alanine-rich proteins.
布氏锥虫生命周期的“双层被膜”模型已流行了15年多。由受感染采采蝇传播的循环后期形态以及哺乳动物血液中的形态都被可变表面糖蛋白所覆盖。直到最近有研究表明采采蝇唾液腺中的前鞭毛体形态表达前环素mRNA但不进行翻译，在此之前人们一直认为所有其他生命周期阶段都有前环素被膜。由于前鞭毛体形态无法培养，因此设计了一种程序来比较不同蝇组织中寄生虫的转录组。编码糖基磷脂酰肌醇锚定蛋白家族（BARPs，以前称为血液富含丙氨酸蛋白）的转录本在唾液腺中的丰度比中肠（前循环期）锥虫高20倍。抗BARP抗血清与唾液腺寄生虫强烈且特异性地反应，并且BARP 3'侧翼区域在蝇中指导报告基因的前鞭毛体特异性表达，但抑制其在血液和前循环期形态中的表达。与早期报告不同，我们在血液形态中未检测到BARPs。我们提出BARPs构成前鞭毛体形态的阶段特异性被膜，并建议将它们重新命名为布氏富含丙氨酸蛋白。
