Absalon Sabrina, Blisnick Thierry, Bonhivers Mélanie, Kohl Linda, Cayet Nadège, Toutirais Géraldine, Buisson Johanna, Robinson Derrick, Bastin Philippe
Trypanosome Cell Biology Unit, Pasteur Institute and CNRS, 25 rue du Docteur Roux, 75015 Paris, France.
J Cell Sci. 2008 Nov 15;121(Pt 22):3704-16. doi: 10.1242/jcs.035626. Epub 2008 Oct 21.
In trypanosomes, the flagellum is rooted in the flagellar pocket, a surface micro-domain that is the sole site for endocytosis and exocytosis. By analysis of anterograde or retrograde intraflagellar transport in IFT88RNAi or IFT140RNAi mutant cells, we show that elongation of the new flagellum is not required for flagellar pocket formation but is essential for its organisation, orientation and function. Transmission electron microscopy revealed that the flagellar pocket exhibited a modified shape (smaller, distorted and/or deeper) in cells with abnormally short or no flagella. Scanning electron microscopy analysis of intact and detergent-extracted cells demonstrated that the orientation of the flagellar pocket collar was more variable in trypanosomes with short flagella. The structural protein BILBO1 was present but its localisation and abundance was altered. The membrane flagellar pocket protein CRAM leaked out of the pocket and reached the short flagella. CRAM also accumulated in intracellular compartments, indicating defects in routing of resident flagellar pocket proteins. Perturbations of vesicular trafficking were obvious; vesicles were observed in the lumen of the flagellar pocket or in the short flagella, and fluid-phase endocytosis was drastically diminished in non-flagellated cells. We propose a model to explain the role of flagellum elongation in correct flagellar pocket organisation and function.
在锥虫中，鞭毛根植于鞭毛袋，这是一个表面微区，是内吞作用和外排作用的唯一部位。通过分析IFT88RNAi或IFT140RNAi突变细胞中的顺行或逆行鞭毛内运输，我们发现新鞭毛的伸长对于鞭毛袋的形成不是必需的，但对于其组织、定向和功能至关重要。透射电子显微镜显示，在鞭毛异常短或没有鞭毛的细胞中，鞭毛袋呈现出改变的形状（更小、扭曲和/或更深）。对完整细胞和用去污剂处理的细胞进行扫描电子显微镜分析表明，在鞭毛短的锥虫中，鞭毛袋环的定向更具变异性。结构蛋白BILBO1存在，但其定位和丰度发生了改变。膜鞭毛袋蛋白CRAM从袋中泄漏出来并到达短鞭毛。CRAM也在细胞内区室中积累，表明驻留鞭毛袋蛋白的运输存在缺陷。囊泡运输的扰动很明显；在鞭毛袋腔或短鞭毛中观察到囊泡，并且在无鞭毛细胞中液相内吞作用急剧减少。我们提出一个模型来解释鞭毛伸长在正确的鞭毛袋组织和功能中的作用。
