Pan Junmin, Snell William J
University of Texas Southwestern Medical School, 5323 Harry Hines Blvd, Dallas, TX 75235-9039, USA.
J Cell Sci. 2003 Jun 1;116(Pt 11):2179-86. doi: 10.1242/jcs.00438. Epub 2003 Apr 8.
The assembly and functioning of cilia and flagella depend on a complex system of traffic between the organelles and the cell body. Two types of transport into these organelles have been identified. The best characterized is constitutive: in a process termed intraflagellar transport (IFT), flagellar structural components are continuously carried into cilia and flagella on transport complexes termed IFT particles via the microtubule motor protein kinesin II. Previous studies have shown that the flagella of the unicellular green alga Chlamydomonas exhibit a second type of protein import that is regulated. During fertilization, the Chlamydomonas aurora protein kinase CALK undergoes regulated translocation from the cell body into the flagella. The motor that powers this second, regulated type of movement is unknown. Here, we have examined the cellular properties of the CALK in Chlamydomonas and used a kinesin II mutant to test the idea that the motor protein is essential for regulated translocation of proteins into flagella. We found that the CALK that is transported into flagella of wild-type gametes becomes part of a membrane-associated complex, that kinesin II is essential for the normal localization of this Chlamydomonas aurora protein kinase in unactivated gametes and that the cAMP-induced translocation of the protein kinase into flagella is disrupted in the fla10 mutants. Our results indicate that, in addition to its role in the constitutive transport of IFT particles and their cargo, kinesin II is essential for regulated translocation of proteins into flagella.
纤毛和鞭毛的组装与功能依赖于细胞器与细胞体之间复杂的运输系统。已确定有两种类型的物质运输进入这些细胞器。其中特征最明显的是组成型运输：在一个被称为鞭毛内运输（IFT）的过程中，鞭毛结构成分通过微管运动蛋白驱动蛋白II，持续搭载在被称为IFT颗粒的运输复合体上进入纤毛和鞭毛。先前的研究表明，单细胞绿藻衣藻的鞭毛表现出另一种受调控的蛋白质输入类型。在受精过程中，衣藻极光蛋白激酶CALK会从细胞体向鞭毛进行受调控的易位。驱动这种第二种受调控运动类型的分子尚不清楚。在这里，我们研究了衣藻中CALK的细胞特性，并使用驱动蛋白II突变体来测试这样一种观点，即运动蛋白对于蛋白质向鞭毛的受调控易位至关重要。我们发现，被运输到野生型配子鞭毛中的CALK成为膜相关复合体的一部分，驱动蛋白II对于这种衣藻极光蛋白激酶在未激活配子中的正常定位至关重要，并且在fla10突变体中，cAMP诱导的蛋白激酶向鞭毛的易位受到破坏。我们的结果表明，驱动蛋白II除了在IFT颗粒及其货物的组成型运输中发挥作用外，对于蛋白质向鞭毛的受调控易位也至关重要。
