Squid Giant Axon Contains Neurofilament Protein mRNA but does not Synthesize Neurofilament Proteins.
Squid Giant Axon Contains Neurofilament Protein mRNA but does not Synthesize Neurofilament Proteins.
复制标题
鱿鱼巨轴突含有神经丝蛋白 mRNA，但不合成神经丝蛋白。
DOI：
10.1007/s10571-016-0382-z
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发表时间：
2017
影响因子：
4
通讯作者：
Pant,HarishC
中科院分区：
文献类型：
--
作者：
Gainer,Harold;House,Shirley;Kim,DongSun;Chin,Hemin;Pant,HarishC
当分离的鱿鱼巨大轴突在放射性氨基酸中孵育时，在轴质中发现大量新合成的蛋白质。这些蛋白在非轴突雪旺细胞中被翻译，随后转移到巨大的轴突中。关于在巨大的轴突中是否有蛋白质合成的问题很难解决，因为轴突内可能合成的蛋白质的少量贡献与从雪旺细胞提供的大量蛋白质很难区分。在本文中，我们通过研究内源性神经丝（NF）蛋白在轴突中的合成来重新审视这一问题。我们实验室之前的研究表明，NF mRNA和蛋白存在于鱿鱼巨轴突中，但不存在于周围的外轴突胶质中。因此，如果分离的鱿鱼轴突可以证明含有新合成的NF蛋白，那么它不可能来自外轴突胶质。本文实验结果表明，鱿鱼巨轴突神经元细胞体中含有丰富的3h标记的NF蛋白，但巨轴突中尽管存在NF mRNA，但未检测到标记的NF蛋白。这支持了胶质-轴突蛋白转移假说，该假说认为鱿鱼巨轴突通过雪旺细胞转移而非轴突内蛋白合成获得新合成的蛋白，并进一步表明轴突内的NF mRNA处于翻译抑制状态。
When isolated squid giant axons are incubated in radioactive amino acids, abundant newly synthesized proteins are found in the axoplasm. These proteins are translated in the adaxonal Schwann cells and subsequently transferred into the giant axon. The question as to whether any de novo protein synthesis occurs in the giant axon itself is difficult to resolve because the small contribution of the proteins possibly synthesized intra-axonally is not easily distinguished from the large amounts of the proteins being supplied from the Schwann cells. In this paper, we reexamine this issue by studying the synthesis of endogenous neurofilament (NF) proteins in the axon. Our laboratory previously showed that NF mRNA and protein are present in the squid giant axon, but not in the surrounding adaxonal glia. Therefore, if the isolated squid axon could be shown to contain newly synthesized NF protein de novo, it could not arise from the adaxonal glia. The results of experiments in this paper show that abundant 3H-labeled NF protein is synthesized in the squid giant fiber lobe containing the giant axon’s neuronal cell bodies, but despite the presence of NF mRNA in the giant axon no labeled NF protein is detected in the giant axon. This lends support to the glia–axon protein transfer hypothesis which posits that the squid giant axon obtains newly synthesized protein by Schwann cell transfer and not through intra-axonal protein synthesis, and further suggests that the NF mRNA in the axon is in a translationally repressed state.