Molecular mechanisms underlying axonal local protein synthesis in neurons

生长锥体内的翻译机。用抗核糖体蛋白抗体进行免疫细胞化学染色，观察生长锥内核糖体的存在。虽然人们普遍认为轴突中没有核糖体，但在培养的背根节神经元和海马神经元的生长锥中发现了针对核糖体蛋白的免疫反应。此外，在这些神经元的生长锥中还发现了几个平移因子。利用原子力显微镜对生长锥进行了精确的形态分析，确定了生长锥内局部平移的触发器，脑源性神经营养因子(BDNF)和WNT3a是生长锥局部平移的触发因子。除了~(35)S甲硫氨酸掺入，嘌呤霉素-抗嘌呤霉素免疫细胞化学方法显示，这些因子激活了生长锥中新的蛋白质合成。这些结果表明生长锥中存在翻译机制，并强烈表明某些生长因子在生长锥中发生局部蛋白质合成。

Translation machinery in growth cone. Existence of ribosomes in growth cone was investigated by immunocytochemistry with anti-ribosomalprotein antibodies. Although it is widely believed that there is no ribosomes in axon, immunoreactivityagainst ribosomal proteins was recognized in growth cone of cultured dorsal root ganglia neurons and ofhippocampal neurons. In addition, several translation factors were found in growth cone of theseneurons. Precise morphological analysis of growth cone was performed by using atomic forcemicroscopy.Triggers of local translation in growth cone.Brain-derived neurotrophic factor (BDNF) and Wnt3a were identified as a trigger of local translation ingrowth cone. In addition to the [35S]methionin incorporation, puromycin-anti-puromycin immunocytochemistry method revealed that these factors activate novel protein synthesis in growth cones.These results indicate the existence of translational machinery in growth cone and strongly suggest thatlocal protein synthesis occurs in growth cones in response to certain growth factors.