Department of Molecular Biosciences, University of Texas, Austin, TX 78751, USA.
J Cell Sci. 2022 Sep 1;135(17). doi: 10.1242/jcs.259444. Epub 2022 Sep 8.
Cilia are multifunctional organelles that originated with the last eukaryotic common ancestor and play central roles in the life cycles of diverse organisms. The motile flagella that move single cells like sperm or unicellular organisms, the motile cilia on animal multiciliated cells that generate fluid flow in organs, and the immotile primary cilia that decorate nearly all cells in animals share many protein components in common, yet each also requires specialized proteins to perform their specialized functions. Despite a now-advanced understanding of how such proteins are transported within cilia, we still know very little about how they are transported from their sites of synthesis through the cytoplasm to the ciliary base. Here, we review the literature concerning this underappreciated topic in ciliary cell biology. We discuss both general mechanisms, as well as specific examples of motor-driven active transport and passive transport via diffusion-and-capture. We then provide deeper discussion of specific, illustrative examples, such as the diverse array of protein subunits that together comprise the intraflagellar transport (IFT) system and the multi-protein axonemal dynein motors that drive beating of motile cilia. We hope this Review will spur further work, shedding light not only on ciliogenesis and ciliary signaling, but also on intracellular transport in general.
纤毛是多功能细胞器，起源于最后一个真核生物共同祖先，并在各种生物的生命周期中发挥核心作用。能使精子或单细胞生物游动的运动性鞭毛、在动物多纤毛细胞上产生液体流动的运动性纤毛，以及装饰动物体内几乎所有细胞的不动性初级纤毛，它们有许多共同的蛋白成分，但每个结构也需要专门的蛋白来执行其特殊功能。尽管我们现在对这些蛋白如何在纤毛内运输有了更深入的了解，但我们对它们如何从合成部位通过细胞质运输到纤毛基部仍然知之甚少。在这里，我们回顾了有关这一被低估的纤毛细胞生物学主题的文献。我们讨论了一般机制，以及通过扩散和捕获进行的马达驱动主动运输和被动运输的具体例子。然后，我们对特定的、说明性的例子进行了更深入的讨论，例如组成内纤毛运输（IFT）系统的各种蛋白亚基和驱动运动性纤毛摆动的多蛋白轴丝动力蛋白。我们希望这篇综述能够激发更多的工作，不仅揭示纤毛发生和纤毛信号转导，而且揭示一般的细胞内运输。
