Ishikawa Hiroaki, Marshall Wallace F
Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94143.
Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94143
Mol Biol Cell. 2017 Nov 7;28(23):3447-3456. doi: 10.1091/mbc.E17-06-0384. Epub 2017 Sep 20.
Cilia and flagella are microtubule-based organelles that protrude from the surface of most cells, are important to the sensing of extracellular signals, and make a driving force for fluid flow. Maintenance of flagellar length requires an active transport process known as intraflagellar transport (IFT). Recent studies reveal that the amount of IFT injection negatively correlates with the length of flagella. These observations suggest that a length-dependent feedback regulates IFT. However, it is unknown how cells recognize the length of flagella and control IFT. Several theoretical models try to explain this feedback system. We focused on one of the models, the "time-of-flight" model, which measures the length of flagella on the basis of the travel time of IFT protein in the flagellar compartment. We tested the time-of-flight model using dynein mutant cells, which show slower retrograde transport speed. The amount of IFT injection in dynein mutant cells was higher than that in control cells. This observation does not support the prediction of the time-of-flight model and suggests that uses another length-control feedback system rather than that described by the time-of-flight model.
纤毛和鞭毛是以微管为基础的细胞器，从大多数细胞表面伸出，对细胞外信号的感知很重要，并为流体流动提供驱动力。维持鞭毛长度需要一种称为鞭毛内运输（IFT）的主动运输过程。最近的研究表明，IFT注入量与鞭毛长度呈负相关。这些观察结果表明，一种长度依赖性反馈调节IFT。然而，细胞如何识别鞭毛长度并控制IFT尚不清楚。有几个理论模型试图解释这种反馈系统。我们重点研究了其中一个模型，即“飞行时间”模型，该模型根据IFT蛋白在鞭毛区室中的传播时间来测量鞭毛长度。我们使用动力蛋白突变细胞测试了“飞行时间”模型，这些细胞显示逆行运输速度较慢。动力蛋白突变细胞中的IFT注入量高于对照细胞。这一观察结果不支持“飞行时间”模型的预测，并表明细胞使用的是另一种长度控制反馈系统，而不是“飞行时间”模型所描述的那种。
