Subcellular and molecular machinery underlying de novo protein synthesis in regenerating axons

周围神经损伤（创伤、神经性疾病）在人类中很常见，而且常常使人衰弱。虽然周围神经的再生比中枢神经系统好，但恢复往往不完全，定向错误或伴有神经性疼痛。尽管广泛的努力旨在定义损伤反应的性质，但精确的细胞和分子机制仍然定义不清。因此，本提案的主要目标之一是确定损伤反应的细胞和分子机制，以及在啮齿动物神经损伤模型中促进神经再生的细胞和分子机制。所有再生反应的核心是蛋白质合成机制，它不仅需要通知细胞核损伤已经发生，而且需要合成新生长和再生所必需的蛋白质——其中许多是在轴突室局部合成的。根据我们的初步结果（我们发现在轴突中没有真实的粗内质网和高尔基体），我们假设轴突合成蛋白质的机制与染色体蛋白质合成的机制不同。我们试图确定蛋白质共翻译靶向进入内质网所需的所有翻译成分是否确实存在：a)存在于轴突中，b)它们如何在亚细胞水平上组织，以及c)它们如何指导局部蛋白质合成。其次，我们将确定这些蛋白质合成机制的元素是否在受损和再生轴突中增加，然后确定它们的细胞起源。鉴于我们最近的数据，我们证明了神经胶质细胞可以“输出”多核糖体到受损的轴突，我们预计神经胶质细胞在指导轴突蛋白质合成方面具有意想不到的新作用。综上所述，这些结果将揭示轴突响应损伤信号的基本机制，并可能在未来为促进创伤后神经修复的新治疗策略铺平道路。

Peripheral nerve injury (trauma, neuropathic disorders) in humans is common and often debilitating. While peripheral nerves do regenerate better than that of central nervous system, recovery is often incomplete, misdirected or associated with incapacitating neuropathic pain. Despite extensive efforts aimed at defining the nature of an injury response, the precise cellular and molecular mechanisms remain however, poorly defined. Thus, one of the main objectives of this proposal is to define the cellular and molecular mechanisms underlying an injury response, and those that promote nerve regeneration in a rodent model of nerve injury. Central to all regenerative responses is the protein synthetic machinery, which is required not only to inform the nucleus that an injury has occurred but also to synthesize proteins that are essential for new growth and regeneration - a number of which are synthesized locally in the axonal compartment. Based on our preliminary results (where we showed that a bona vide rough endoplasmic reticulum and Golgi apparatus are absent in axons), we hypothesize that axons synthesize proteins through a mechanism that is distinct from that of somal protein synthesis. We seek to determine whether all translational components needed for co-translational targeting of proteins into the ER are indeed: a) present in axons, b) how they are organized at the subcellular level, and c) how they direct local protein synthesis. Secondly, we will determine whether these elements of the proteins synthetic machinery increase in injured and regenerating axons and then determine their cellular origin. In view of our recent data, in which we demonstrated that glia cells can "export" polyribosomes to injured axons, we anticipate an unexpected new role for glia cells in directing protein synthesis in axons. Taken together, these results will shed new light on fundamental mechanisms by which axons respond to injury signals, and in the future may pave the way for novel treatment strategies to promote nerve repair after trauma.