Optical control of ERK and AKT signaling promotes axon regeneration and functional recovery of PNS and CNS in Drosophila.
Optical control of ERK and AKT signaling promotes axon regeneration and functional recovery of PNS and CNS in Drosophila.
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DOI：
10.7554/elife.57395
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发表时间：
2020-10-06
期刊：
影响因子：
7.7
通讯作者：
Zhang K
中科院分区：
文献类型：
--
作者：
Wang Q;Fan H;Li F;Skeeters SS;Krishnamurthy VV;Song Y;Zhang K
神经再生是一个动态的过程，它协同多个信号通路的功能结果。基于通道视紫红质的光遗传学显示了刺激神经修复的可行性，但并不限制特定的信号级联。在这里，我们利用光遗传系统，光学Raf和光学AKT，来描述ERK和AKT信号通路在活的果蝇幼虫神经再生中的作用。我们发现，激活视神经生长因子或视AKT不仅可以促进周围神经系统中再生能力强和功能不强的感觉神经元的轴突再生，而且还可以进行时间调节和适当引导轴突再生。此外，在再生过程中，光Raf和光AKT的信号动力学不同，分别表现为门控反应和分级反应。重要的是，在中枢神经系统中，它们的激活促进轴突再生和热伤害性行为的功能恢复。我们的结论是，非神经元光遗传学针对受损的神经元和信号子电路，提供了一种新的策略，以提高精确度干预神经损伤。大多数细胞都有一个内置的再生信号程序，允许它们分裂和修复。但是，在被称为神经元的中枢神经系统细胞中，这个程序是无效的。这就是为什么影响大脑和脊髓的事故和疾病会造成永久性损害。重新激活神经元的再生可以帮助它们修复，但这并不容易。某些小分子可以重新启动修复信号程序。不幸的是，这些分子很容易在组织中扩散，扩散到全身，从而很难瞄准个别受损的细胞。这既阻碍了对神经元修复的研究，也使旨在修复神经系统损伤的治疗更有可能产生副作用。目前还不清楚是否有可能重新激活单个神经元的再生信号。解决这个问题的一种方法是使用光遗传学。这项技术使用基因工程将对光敏感的蛋白质与负责在细胞内传递信号的蛋白质融合在一起。当特定波长的光照射到光敏蛋白时，融合的信号蛋白就会启动，导致它们控制的任何蛋白的激活，例如那些参与再生的蛋白。Wang等人。使用光遗传工具来确定光是否可以帮助修复果蝇幼虫的神经元。首先，用强激光破坏一只果蝇幼虫的单个神经元，该幼虫已被转基因，因此蓝光将激活其神经元中的再生程序。然后，Wang等人提出了自己的观点。用暗淡的蓝光照亮细胞，开启再生程序。这不仅允许神经元自我修复，还允许光线引导其再生。通过将蓝光聚焦在神经元受损的一端，可以在细胞再生时引导细胞的生长方向。果蝇和哺乳动物的再生计划涉及类似的信号蛋白，但蓝光不能很好地穿透到哺乳动物组织中。这意味着，在哺乳动物进行神经元修复实验之前，可能有必要对可植入的LED进行进一步研究。无论如何，集中治疗单个神经元的能力为神经系统再生的未来研究铺平了道路，而光和遗传学的结合可能会揭示更多关于修复信号如何工作的信息。
Neuroregeneration is a dynamic process synergizing the functional outcomes of multiple signaling circuits. Channelrhodopsin-based optogenetics shows the feasibility of stimulating neural repair but does not pin down specific signaling cascades. Here, we utilized optogenetic systems, optoRaf and optoAKT, to delineate the contribution of the ERK and AKT signaling pathways to neuroregeneration in live Drosophila larvae. We showed that optoRaf or optoAKT activation not only enhanced axon regeneration in both regeneration-competent and -incompetent sensory neurons in the peripheral nervous system but also allowed temporal tuning and proper guidance of axon regrowth. Furthermore, optoRaf and optoAKT differ in their signaling kinetics during regeneration, showing a gated versus graded response, respectively. Importantly in the central nervous system, their activation promotes axon regrowth and functional recovery of the thermonociceptive behavior. We conclude that non-neuronal optogenetics targets damaged neurons and signaling subcircuits, providing a novel strategy in the intervention of neural damage with improved precision. Most cells have a built-in regeneration signaling program that allows them to divide and repair. But, in the cells of the central nervous system, which are called neurons, this program is ineffective. This is why accidents and illnesses affecting the brain and spinal cord can cause permanent damage. Reactivating regeneration in neurons could help them repair, but it is not easy. Certain small molecules can switch repair signaling programs back on. Unfortunately, these molecules diffuse easily through tissues, spreading around the body and making it hard to target individual damaged cells. This both hampers research into neuronal repair and makes treatments directed at healing damage to the nervous system more likely to have side-effects. It is unclear whether reactivating regeneration signaling in individual neurons is possible. One way to address this question is to use optogenetics. This technique uses genetic engineering to fuse proteins that are light-sensitive to proteins responsible for relaying signals in the cell. When specific wavelengths of light hit the light-sensitive proteins, the fused signaling proteins switch on, leading to the activation of any proteins they control, for example, those involved in regeneration. Wang et al. used optogenetic tools to determine if light can help repair neurons in fruit fly larvae. First, a strong laser light was used to damage an individual neuron in a fruit fly larva that had been genetically modified so that blue light would activate the regeneration program in its neurons. Then, Wang et al. illuminated the cell with dim blue light, switching on the regeneration program. Not only did this allow the neuron to repair itself, it also allowed the light to guide its regeneration. By focusing the blue light on the damaged end of the neuron, it was possible to guide the direction of the cell's growth as it regenerated. Regeneration programs in flies and mammals involve similar signaling proteins, but blue light does not penetrate well into mammalian tissues. This means that further research into LEDs that can be implanted may be necessary before neuronal repair experiments can be performed in mammals. In any case, the ability to focus treatment on individual neurons paves the way for future work into the regeneration of the nervous system, and the combination of light and genetics could reveal more about how repair signals work.