School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore.
Cell Mol Life Sci. 2018 Feb;75(4):597-606. doi: 10.1007/s00018-017-2629-3. Epub 2017 Aug 29.
Primary cilium is a rod-like plasma membrane protrusion that plays important roles in sensing the cellular environment and initiating corresponding signaling pathways. The sensory functions of the cilium critically depend on the unique enrichment of ciliary residents, which is maintained by the ciliary diffusion barrier. It is still unclear how ciliary cargoes specifically enter the diffusion barrier and accumulate within the cilium. In this review, the organization and trafficking mechanism of the cilium are compared to those of the nucleus, which are much better understood at the moment. Though the cilium differs significantly from the nucleus in terms of molecular and cellular functions, analogous themes and principles in the membrane organization and cargo trafficking are notable between them. Therefore, knowledge in the nuclear trafficking can likely shed light on our understanding of the ciliary trafficking. Here, with a focus on membrane cargoes in mammalian cells, we briefly review various ciliary trafficking pathways from the Golgi to the periciliary membrane. Models for the subsequent import translocation across the diffusion barrier and the enrichment of cargoes within the ciliary membrane are discussed in detail. Based on recent discoveries, we propose a Rab-importin-based model in an attempt to accommodate various observations on ciliary targeting.
纤毛是一种杆状的质膜突起，在感知细胞环境和启动相应的信号通路方面发挥着重要作用。纤毛的感觉功能取决于纤毛居民的独特富集，这是由纤毛扩散屏障维持的。目前尚不清楚纤毛货物是如何特异性地进入扩散屏障并在纤毛内积累的。在这篇综述中，纤毛的组织和运输机制与核进行了比较，目前对核的了解要好得多。尽管纤毛在分子和细胞功能上与核有很大的不同，但它们在膜组织和货物运输方面有类似的主题和原则。因此，核运输方面的知识可能有助于我们理解纤毛运输。在这里，我们主要关注哺乳动物细胞中的膜货物，简要回顾了从高尔基体到纤毛周围膜的各种纤毛运输途径。详细讨论了随后穿过扩散屏障的导入易位和货物在纤毛膜内的富集模型。基于最近的发现，我们提出了一个基于 Rab-importin 的模型，试图容纳关于纤毛靶向的各种观察结果。
