Audebert S, Koulakoff A, Berwald-Netter Y, Gros F, Denoulet P, Eddé B
Laboratoire de Biochimie Cellulaire, Collège de France (and Université Pierre et Marie Curie), Paris.
J Cell Sci. 1994 Aug;107 ( Pt 8):2313-22. doi: 10.1242/jcs.107.8.2313.
Polyglutamylation is an important posttranslational modification of tubulin that is very active in nerve cells, where it accounts for the main factor responsible for tubulin heterogeneity. In the present work, we have analyzed quantitative and qualitative changes in glutamylated alpha- and beta-tubulin occurring during neuronal differentiation in culture. Glutamylated alpha- and beta-tubulin both markedly accumulate during this process with a time course remarkably similar to that observed in vivo during brain development. However, the characteristics of the glutamylation of the two subunits are not exactly the same. Glutamylated alpha-tubulin is already abundant in very young neurons and displays, at this stage, a wide range of its degree of glutamylation (1 to 6 glutamyl units present in the lateral polyglutamyl chain), which remains unchanged during the entire period of the culture. Glutamylated beta-tubulin is present at very low levels in young neurons and its accumulation during differentiation is accompanied by a progressive increase in its degree of glutamylation from 2 to 6 glutamyl units. Posttranslational incorporation of [3H]glutamate into alpha- and beta-tubulin decreases during differentiation, as well as the rate of the reverse deglutamylation reaction, suggesting that accumulation of glutamylated tubulin is accompanied by a decrease in the turnover of glutamyl units onto tubulin. Neuronal differentiation is also accompanied by an increase of other posttranslationally modified forms of tubulin, including acetylated and non-tyrosinatable alpha-tubulin, which can occur in combination with polyglutamylation and contributes to increase the complexity of tubulin in mature neurons.
多聚谷氨酰胺化是微管蛋白重要的翻译后修饰，在神经细胞中非常活跃，是导致微管蛋白异质性的主要因素。在本研究中，我们分析了培养的神经元分化过程中，谷氨酰胺化的α-和β-微管蛋白的定量和定性变化。在此过程中，谷氨酰胺化的α-和β-微管蛋白均显著积累，其时间进程与体内大脑发育过程中观察到的非常相似。然而，两个亚基的谷氨酰胺化特征并不完全相同。谷氨酰胺化的α-微管蛋白在非常年轻的神经元中就已大量存在，并且在此阶段，其谷氨酰胺化程度范围很广（侧链多聚谷氨酰胺链中存在1至6个谷氨酰胺单元），在整个培养期间保持不变。谷氨酰胺化的β-微管蛋白在年轻神经元中的含量非常低，其在分化过程中的积累伴随着谷氨酰胺化程度从2个谷氨酰胺单元逐渐增加到6个谷氨酰胺单元。在分化过程中，[3H]谷氨酸向α-和β-微管蛋白的翻译后掺入减少，同时反向去谷氨酰胺化反应的速率也降低，这表明谷氨酰胺化微管蛋白的积累伴随着微管蛋白上谷氨酰胺单元周转的减少。神经元分化还伴随着微管蛋白其他翻译后修饰形式的增加，包括乙酰化和不可酪氨酸化的α-微管蛋白，它们可以与多聚谷氨酰胺化同时发生，并有助于增加成熟神经元中微管蛋白的复杂性。
