Graduate School of Frontier Sciences, The University of Tokyo, Kashiwanoha 5-1-5, Kashiwa-shi, Chiba 277-8592, Japan.
Dev Neurobiol. 2011 Jul;71(7):634-49. doi: 10.1002/dneu.20879.
Intracellular transport of neurotrophin receptors together with neurotrophins is one of the key events of neurotrophin signaling for the growth and the survival of neurons. However, the involvement of neurotrophin signaling in the regulation of intracellular transport of neurotrophin receptors has been remained unclear. We visualized the behavior of TrkA, a receptor of nerve growth factor (NGF), by labeling with GFP in PC12 cells. We found remarkable changes of the behavior of TrkA-GFP upon the application of NGF. Before the application, only ~37% of the fluorescent dots of TrkA showed translocations along neurites of PC12 cells. After the application, number of the dots showing the directional movement increased to ~65%. The averaged velocities of the directional movement of TrkA-GFP dots became higher after the application of NGF. We tested the idea whether NGF binding accelerated the translocations of TrkA by simultaneously observing TrkA-GFP and fluorescently labeled NGF, Cy3.5-NGF. The velocity of TrkA-GFP dots associated with Cy3.5-NGF was remarkably higher than that of TrkA-GFP dots without Cy3.5-NGF. On the basis of these observations, we hypothesize that there is a signaling mechanism within a single vesicle that facilitates the intracellular transport of each vesicle containing the activated TrkA.
神经营养因子受体与神经营养因子的细胞内运输是神经营养因子信号转导促进神经元生长和存活的关键事件之一。然而，神经营养因子信号转导在神经营养因子受体的细胞内运输调节中的作用仍不清楚。我们通过在 PC12 细胞中用 GFP 标记神经生长因子（NGF）的受体 TrkA，来观察其行为。我们发现 NGF 应用后 TrkA-GFP 的行为发生了显著变化。在应用 NGF 之前，只有约 37%的 TrkA 荧光斑点沿着 PC12 细胞的轴突发生易位。应用 NGF 后，显示定向运动的斑点数量增加到约 65%。NGF 应用后，TrkA-GFP 斑点的定向运动平均速度升高。我们通过同时观察 TrkA-GFP 和荧光标记的 NGF（Cy3.5-NGF）来测试 NGF 结合是否能加速 TrkA 的易位的想法。与 Cy3.5-NGF 相关联的 TrkA-GFP 斑点的速度明显高于没有 Cy3.5-NGF 的 TrkA-GFP 斑点。基于这些观察，我们假设在单个囊泡内存在一种信号机制，促进了含有激活的 TrkA 的每个囊泡的细胞内运输。
