Morriswood Brooke, Schmidt Katy
Max F. Perutz Laboratories, University of Vienna, Medical University of Vienna, Vienna, Austria
Department of Cell Biology and Ultrastructure Research, Center for Anatomy and Cell Biology, Medical University of Vienna, Vienna, Austria
Eukaryot Cell. 2015 Nov;14(11):1081-93. doi: 10.1128/EC.00094-15. Epub 2015 Aug 28.
The parasite Trypanosoma brucei lives in the bloodstream of infected mammalian hosts, fully exposed to the adaptive immune system. It relies on a very high rate of endocytosis to clear bound antibodies from its cell surface. All endo- and exocytosis occurs at a single site on its plasma membrane, an intracellular invagination termed the flagellar pocket. Coiled around the neck of the flagellar pocket is a multiprotein complex containing the repeat motif protein T. brucei MORN1 (TbMORN1). In this study, the phenotypic effects of TbMORN1 depletion in the mammalian-infective form of T. brucei were analyzed. Depletion of TbMORN1 resulted in a rapid enlargement of the flagellar pocket. Dextran, a polysaccharide marker for fluid phase endocytosis, accumulated inside the enlarged flagellar pocket. Unexpectedly, however, the proteins concanavalin A and bovine serum albumin did not do so, and concanavalin A was instead found to concentrate outside it. This suggests that TbMORN1 may have a role in facilitating the entry of proteins into the flagellar pocket.
布氏锥虫这种寄生虫生活在受感染哺乳动物宿主的血液中，完全暴露于适应性免疫系统之下。它依靠非常高的内吞速率来清除其细胞表面结合的抗体。所有的内吞作用和外排作用都发生在其质膜上的一个单一部位，即一个被称为鞭毛袋的细胞内陷结构。围绕鞭毛袋颈部盘绕着一个多蛋白复合物，其中包含重复基序蛋白布氏锥虫MORN1（TbMORN1）。在本研究中，分析了TbMORN1缺失对布氏锥虫哺乳动物感染形式的表型影响。TbMORN1的缺失导致鞭毛袋迅速扩大。葡聚糖是一种用于液相内吞作用的多糖标记物，在扩大的鞭毛袋内积累。然而，出乎意料的是，伴刀豆球蛋白A和牛血清白蛋白这两种蛋白质却没有如此，相反，发现伴刀豆球蛋白A集中在鞭毛袋外部。这表明TbMORN1可能在促进蛋白质进入鞭毛袋方面发挥作用。
