Department of Genetics, Human Genetics Institute of New Jersey, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA.
Department of Genetics, Human Genetics Institute of New Jersey, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA.
Curr Biol. 2017 Nov 20;27(22):3430-3441.e6. doi: 10.1016/j.cub.2017.09.066. Epub 2017 Nov 9.
Ciliary microtubules (MTs) are extensively decorated with post-translational modifications (PTMs), such as glutamylation of tubulin tails. PTMs and tubulin isotype diversity act as a "tubulin code" that regulates cytoskeletal stability and the activity of MT-associated proteins such as kinesins. We previously showed that, in C. elegans cilia, the deglutamylase CCPP-1 affects ciliary ultrastructure, localization of the TRP channel PKD-2 and the kinesin-3 KLP-6, and velocity of the kinesin-2 OSM-3/KIF17, whereas a cell-specific α-tubulin isotype regulates ciliary ultrastructure, intraflagellar transport, and ciliary functions of extracellular vesicle (EV)-releasing neurons. Here we examine the role of PTMs and the tubulin code in the ciliary specialization of EV-releasing neurons using genetics, fluorescence microscopy, kymography, electron microscopy, and sensory behavioral assays. Although the C. elegans genome encodes five tubulin tyrosine ligase-like (TTLL) glutamylases, only ttll-11 specifically regulates PKD-2 localization in EV-releasing neurons. In EV-releasing cephalic male (CEM) cilia, TTLL-11 and the deglutamylase CCPP-1 regulate remodeling of 9+0 MT doublets into 18 singlet MTs. Balanced TTLL-11 and CCPP-1 activity fine-tunes glutamylation to control the velocity of the kinesin-2 OSM-3/KIF17 and kinesin-3 KLP-6 without affecting the intraflagellar transport (IFT) kinesin-II. TTLL-11 is transported by ciliary motors. TTLL-11 and CCPP-1 are also required for the ciliary function of releasing bioactive EVs, and TTLL-11 is itself a novel EV cargo. Therefore, MT glutamylation, as part of the tubulin code, controls ciliary specialization, ciliary motor-based transport, and ciliary EV release in a living animal. We suggest that cell-specific control of MT glutamylation may be a conserved mechanism to specialize the form and function of cilia.
纤毛微管（MTs）广泛被翻译后修饰（PTMs）修饰，如微管尾部的谷氨酸化。PTMs 和微管同工型多样性充当“微管密码”，调节细胞骨架的稳定性和 MT 相关蛋白的活性，如驱动蛋白。我们之前表明，在 C. elegans 纤毛中，脱谷氨酰胺酶 CCPP-1 影响纤毛超微结构、TRP 通道 PKD-2 和驱动蛋白-3 KLP-6 的定位以及驱动蛋白-2 OSM-3/KIF17 的速度，而细胞特异性的α-微管同工型调节纤毛超微结构、鞭毛内运输和细胞外囊泡（EV）释放神经元的纤毛功能。在这里，我们使用遗传学、荧光显微镜、运动分析、电子显微镜和感觉行为测定来研究 PTMs 和微管密码在 EV 释放神经元的纤毛特化中的作用。尽管 C. elegans 基因组编码了五个微管酪氨酸连接酶样（TTLL）谷氨酸酶，但只有 ttll-11 特异性调节 EV 释放神经元中 PKD-2 的定位。在 EV 释放的头雄性（CEM）纤毛中，TTLL-11 和脱谷氨酰胺酶 CCPP-1 调节 9+0 MT 二联体向 18 个单 MT 的重塑。平衡的 TTLL-11 和 CCPP-1 活性精细调节谷氨酸化以控制驱动蛋白-2 OSM-3/KIF17 和驱动蛋白-3 KLP-6 的速度，而不影响鞭毛内运输（IFT）驱动蛋白-II。TTLL-11 由纤毛马达运输。TTLL-11 和 CCPP-1 也需要释放生物活性 EV 的纤毛功能，并且 TTLL-11 本身就是一种新型 EV 货物。因此，作为微管密码的一部分，MT 谷氨酸化控制着动物活体中纤毛特化、基于纤毛马达的运输和纤毛 EV 释放。我们认为，MT 谷氨酸化的细胞特异性控制可能是特化纤毛形态和功能的保守机制。
