Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307, Dresden, Germany.
D'Or Institute for Research and Education (IDOR), Rua Diniz Cordeiro, 30, 22281-100, Rio de Janeiro, Brazil.
Sci Rep. 2019 Feb 21;9(1):2433. doi: 10.1038/s41598-019-38637-0.
Long-distance axonal trafficking plays a critical role in neuronal function and transport defects have been linked to neurodegenerative disorders. Various lines of evidence suggest that the small GTPase Rab5 plays a role in neuronal signaling via early endosomal transport. Here, we characterized the motility of Rab5 endosomes in primary cultures of mouse hippocampal pyramidal cells by live-cell imaging and showed that they exhibit bi-directional long-range motility in axons, with a strong bias toward retrograde transport. Characterization of key Rab5 effectors revealed that endogenous Rabankyrin-5, Rabenosyn-5 and APPL1 are all present in axons. Further analysis of APPL1-positive endosomes showed that, similar to Rab5-endosomes, they display more frequent long-range retrograde than anterograde movement, with the endosomal levels of APPL1 correlated with faster retrograde movement. Interestingly, APPL1-endosomes transport the neurotrophin receptor TrkB and mediate retrograde axonal transport of the kinase Akt1. FRET analysis revealed that APPL1 and Akt1 interact in an endocytosis-dependent manner. We conclude that Rab5-APPL1 endosomes exhibit the hallmarks of axonal signaling endosomes to transport Akt1 in hippocampal pyramidal cells.
长距离轴突运输在神经元功能中起着至关重要的作用,运输缺陷与神经退行性疾病有关。各种证据表明,小分子 GTPase Rab5 通过早期内体运输在神经元信号转导中发挥作用。在这里,我们通过活细胞成像对原代培养的小鼠海马锥体神经元中的 Rab5 内体的迁移进行了表征,并表明它们在轴突中表现出双向的长程迁移,具有强烈的逆行运输偏向性。对关键 Rab5 效应物的表征表明,内源性 Rabankyrin-5、Rabenosyn-5 和 APPL1 均存在于轴突中。对 APPL1 阳性内体的进一步分析表明,与 Rab5 内体类似,它们显示出更频繁的长程逆行运动而不是顺行运动,APPL1 内体的水平与更快的逆行运动相关。有趣的是,APPL1 内体运输神经营养因子受体 TrkB,并介导激酶 Akt1 的逆行轴突运输。FRET 分析显示 APPL1 和 Akt1 以依赖于内吞作用的方式相互作用。我们的结论是,Rab5-APPL1 内体在海马锥体神经元中表现出轴突信号转导内体的特征,以运输 Akt1。