Sorbonne Université, University Pierre and Marie Curie-Université Paris 6, Institut de Biologie Paris Seine, Unité de Neuroscience Paris Seine, Centre National de la Recherche Scientifique, Unité Mixte Recherche 8246, Institut National de la Santé et de la Recherche Médicale U1130, Paris, France.
Department of Genetics and Developmental Biology, Institut Curie, Paris, France.
J Cell Biol. 2019 Oct 7;218(10):3290-3306. doi: 10.1083/jcb.201805128. Epub 2019 Sep 19.
Neuronal connectivity relies on molecular motor-based axonal transport of diverse cargoes. Yet the precise players and regulatory mechanisms orchestrating such trafficking events remain largely unknown. We here report the ATPase Fignl1 as a novel regulator of bidirectional transport during axon navigation. Using a yeast two-hybrid screen and coimmunoprecipitation assays, we showed that Fignl1 binds the kinesin Kif1bβ and the dynein/dynactin adaptor Bicaudal D-1 (Bicd1) in a molecular complex including the dynactin subunit dynactin 1. Fignl1 colocalized with Kif1bβ and showed bidirectional mobility in zebrafish axons. Notably, Kif1bβ and Fignl1 loss of function similarly altered zebrafish motor axon pathfinding and increased dynein-based transport velocity of Rab3 vesicles in these navigating axons, pinpointing Fignl1/Kif1bβ as a dynein speed limiter complex. Accordingly, disrupting dynein/dynactin activity or Bicd1/Fignl1 interaction induced motor axon pathfinding defects characteristic of Fignl1 gain or loss of function, respectively. Finally, pharmacological inhibition of dynein activity partially rescued the axon pathfinding defects of Fignl1-depleted larvae. Together, our results identify Fignl1 as a key dynein regulator required for motor circuit wiring.
神经元连接依赖于多种货物的基于分子马达的轴突运输。然而，精确调节这种运输事件的特定参与者和调节机制在很大程度上仍是未知的。我们在这里报告了 Fignl1 作为轴突导航过程中双向运输的新调节因子。使用酵母双杂交筛选和共免疫沉淀测定，我们表明 Fignl1 在包括动力蛋白 dynactin 1 的分子复合物中与驱动蛋白 Kif1bβ 和 dynein/dynactin 衔接子 Bicaudal D-1 (Bicd1) 结合。Fignl1 与 Kif1bβ 共定位，并在斑马鱼轴突中表现出双向流动性。值得注意的是，Kif1bβ 和 Fignl1 的功能丧失同样改变了斑马鱼运动轴突的轨迹，并增加了这些导航轴突中 Rab3 囊泡的基于 dynein 的运输速度，这表明 Fignl1/Kif1bβ 是 dynein 速度限制复合物。因此，破坏 dynein/dynactin 活性或 Bicd1/Fignl1 相互作用分别诱导了具有 Fignl1 功能获得或丧失特征的运动轴突轨迹缺陷。最后，dynein 活性的药理学抑制部分挽救了 Fignl1 耗尽幼虫的轴突轨迹缺陷。总之，我们的结果确定了 Fignl1 作为运动回路布线所需的关键 dynein 调节剂。
