Valetti C, Wetzel D M, Schrader M, Hasbani M J, Gill S R, Kreis T E, Schroer T A
Department of Cell Biology, University of Geneva, Geneva 1211, Switzerland.
Mol Biol Cell. 1999 Dec;10(12):4107-20. doi: 10.1091/mbc.10.12.4107.
The flow of material from peripheral, early endosomes to late endosomes requires microtubules and is thought to be facilitated by the minus end-directed motor cytoplasmic dynein and its activator dynactin. The microtubule-binding protein CLIP-170 may also play a role by providing an early link to endosomes. Here, we show that perturbation of dynactin function in vivo affects endosome dynamics and trafficking. Endosome movement, which is normally bidirectional, is completely inhibited. Receptor-mediated uptake and recycling occur normally, but cells are less susceptible to infection by enveloped viruses that require delivery to late endosomes, and they show reduced accumulation of lysosomally targeted probes. Dynactin colocalizes at microtubule plus ends with CLIP-170 in a way that depends on CLIP-170's putative cargo-binding domain. Overexpression studies using p150(Glued), the microtubule-binding subunit of dynactin, and mutant and wild-type forms of CLIP-170 indicate that CLIP-170 recruits dynactin to microtubule ends. These data suggest a new model for the formation of motile complexes of endosomes and microtubules early in the endocytic pathway.
物质从外周早期内体向晚期内体的流动需要微管，并且被认为是由向负端移动的动力蛋白胞质动力蛋白及其激活剂发动蛋白所促进的。微管结合蛋白CLIP - 170也可能通过提供与内体的早期连接而发挥作用。在这里，我们表明在体内干扰发动蛋白功能会影响内体动力学和运输。通常双向的内体运动被完全抑制。受体介导的摄取和循环正常发生，但细胞对需要递送至晚期内体的包膜病毒感染的敏感性降低，并且它们显示溶酶体靶向探针的积累减少。发动蛋白以一种依赖于CLIP - 170假定的货物结合结构域的方式与CLIP - 170共定位于微管正端。使用发动蛋白的微管结合亚基p150(Glued)以及CLIP - 170的突变体和野生型形式进行的过表达研究表明，CLIP - 170将发动蛋白招募至微管末端。这些数据提示了内吞途径早期内体与微管的运动复合物形成的新模型。
