Selzer P M, Webster P, Duszenko M
Physiologisch-chemisches Institut Universität, Tübingen/Bundesrepublik, Deutschland.
Eur J Cell Biol. 1991 Oct;56(1):104-12.
Trypanosoma brucei bloodstream forms were incubated in a calcium-free medium containing 10 microM ethyleneglycol-bis-(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA). Under these conditions, addition of 5 microM calcium ionophore A23187 led to striking morphological alterations, as judged by light and electron microscopy. The cytoskeleton of trypanosomes consists of a subpellicular corset of microtubules. Characteristically four of these microtubules are attached invariantly to an extension of the endoplasmic reticulum at the flagellar attachment site. Specifically in this area calcium depletion led to the polymerization of additional microtubules and to a retraction of the endoplasmic reticulum extension from its usual position. Additionally, A23187 led to nucleolus segregation, as revealed by immunocytochemistry using antibodies against DNA and fibrillarin, respectively. Nucleolus segregation, but not microtubule accumulation, was also obtained by using 20 microM camptothecin, a specific inhibitor of topoisomerase I. Our data suggest that intracellular calcium regulation might be important for specific depolymerization/polymerization reactions during the course of cell division and the formation of functional ribosomes.
布氏锥虫血流型在含有10微摩尔乙二醇双（β-氨基乙醚）-N，N，N'，N'-四乙酸（EGTA）的无钙培养基中孵育。在这些条件下，添加5微摩尔钙离子载体A23187会导致明显的形态改变，这通过光学显微镜和电子显微镜观察得以判断。锥虫的细胞骨架由微管的亚pellicular紧身衣组成。这些微管中的四个典型地始终附着在内质网在鞭毛附着位点的延伸处。具体而言，在这个区域，钙耗竭导致额外微管的聚合以及内质网延伸从其通常位置缩回。此外，A23187导致核仁分离，分别使用针对DNA和纤维蛋白原的抗体通过免疫细胞化学揭示。使用20微摩尔喜树碱（一种拓扑异构酶I的特异性抑制剂）也获得了核仁分离，但没有微管积累。我们的数据表明，细胞内钙调节对于细胞分裂过程中特定的解聚/聚合反应以及功能性核糖体的形成可能很重要。
