Department of Cell Biology, University of Geneva Sciences III Geneva, Switzerland.
School of Life Sciences, Swiss Institute for Experimental Cancer Research (ISREC), Swiss Federal Institute of Technology (EPFL) Lausanne, Switzerland.
Bioessays. 2018 Apr;40(4):e1700241. doi: 10.1002/bies.201700241. Epub 2018 Mar 6.
The cartwheel is a striking structure critical for building the centriole, a microtubule-based organelle fundamental for organizing centrosomes, cilia, and flagella. Over the last 50 years, the cartwheel has been described in many systems using electron microscopy, but the molecular nature of its constituent building blocks and their assembly mechanisms have long remained mysterious. Here, we review discoveries that led to the current understanding of cartwheel structure, assembly, and function. We focus on the key role of SAS-6 protein self-organization, both for building the signature ring-like structure with hub and spokes, as well as for their vertical stacking. The resemblance of assembly intermediates in vitro and in vivo leads us to propose a novel registration step in cartwheel biogenesis, whereby stacked SAS-6-containing rings are put in register through interactions with peripheral elements anchored to microtubules. We conclude by evoking some avenues for further uncovering cartwheel and centriole assembly mechanisms.
车轮结构非常引人注目，对于构建中心粒至关重要，中心粒是一种基于微管的细胞器，对于组织中心体、纤毛和鞭毛至关重要。在过去的 50 年中，使用电子显微镜已经在许多系统中描述了车轮结构，但它的组成构建块的分子性质及其组装机制长期以来一直是个谜。在这里，我们回顾了导致目前对车轮结构、组装和功能的理解的发现。我们专注于 SAS-6 蛋白自我组织的关键作用，既用于构建带有轮毂和辐条的标志性环状结构，也用于它们的垂直堆叠。体外和体内组装中间体的相似性使我们提出了车轮发生过程中的一个新的注册步骤，即通过与锚定在微管上的外围元件的相互作用，将堆叠的含有 SAS-6 的环进行注册。最后，我们提出了一些进一步揭示车轮和中心粒组装机制的途径。
