Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, UK.
EMBO J. 2010 Mar 3;29(5):992-1006. doi: 10.1038/emboj.2009.410. Epub 2010 Jan 28.
Cargo transport by microtubule-based motors is essential for cell organisation and function. The Bicaudal-D (BicD) protein participates in the transport of a subset of cargoes by the minus-end-directed motor dynein, although the full extent of its functions is unclear. In this study, we report that in Drosophila zygotic BicD function is only obligatory in the nervous system. Clathrin heavy chain (Chc), a major constituent of coated pits and vesicles, is the most abundant protein co-precipitated with BicD from head extracts. BicD binds Chc directly and interacts genetically with components of the pathway for clathrin-mediated membrane trafficking. Directed transport and subcellular localisation of Chc is strongly perturbed in BicD mutant presynaptic boutons. Functional assays show that BicD and dynein are essential for the maintenance of normal levels of neurotransmission specifically during high-frequency electrical stimulation and that this is associated with a reduced rate of recycling of internalised synaptic membrane. Our results implicate BicD as a new player in clathrin-associated trafficking processes and show a novel requirement for microtubule-based motor transport in the synaptic vesicle cycle.
基于微管的马达的货物运输对于细胞组织和功能至关重要。双尾蛋白（BicD）蛋白参与了由负向导向的动力蛋白 dynein 运输的一组货物，但它的全部功能尚不清楚。在这项研究中，我们报告说，在果蝇合子中，BicD 的功能仅在神经系统中是必需的。网格蛋白重链（Chc）是网格蛋白包被小窝和囊泡的主要成分，是从头部提取物中与 BicD 最丰富的共沉淀蛋白。BicD 直接与 Chc 结合，并与网格蛋白介导的膜运输途径的成分在遗传上相互作用。Chc 的定向运输和亚细胞定位在 BicD 突变体突触小泡中受到强烈干扰。功能测定表明，BicD 和动力蛋白对于维持正常的神经递质传递水平是必需的，特别是在高频电刺激期间，这与内化突触膜的回收速率降低有关。我们的结果表明 BicD 是网格蛋白相关运输过程中的一个新参与者，并显示微管基马达运输在突触小泡循环中的一个新的要求。
