The Relationship between Dendritic Branch Dynamics and CPEB-Labeled RNP Granules Captured in Vivo.
The Relationship between Dendritic Branch Dynamics and CPEB-Labeled RNP Granules Captured in Vivo.
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DOI：
10.3389/neuro.04.010.2009
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发表时间：
2009
影响因子：
3.5
通讯作者：
Cline HT
中科院分区：
文献类型：
--
作者：
Bestman JE;Cline HT
胞浆多聚腺苷酸化元件结合蛋白(CPEB)是一种RNA结合蛋白，参与树突状突起的mRNA递送和活性依赖的多聚腺苷诱导的mRNAs翻译。CPEB影响学习和记忆，影响神经元形态和突触可塑性。在神经元中，CPEB主要集中在分布于树突和突触附近的核糖核蛋白(RNP)颗粒中，提示RNP颗粒的转运对CPEB的功能具有重要意义。我们用荧光蛋白标记了全长CPEB和一个非活性突变体CPEB，然后用双光子时间推移显微镜对活的非洲爪哇蝌蚪顶盖中的神经元进行了快速树突动力学和RNP分布的成像。虽然失活的CPEB突变体在树突状突起转运mRNA，但其表达干扰了CPEB依赖的翻译，因为它不能激活触发的mRNA聚腺苷酸化。在树突中，活性的和非活性的含CPEB的RNP颗粒的分布没有区别；RNP颗粒致密，其位置与快速树突分支动力学的位置或树突分支的最终命运无关。由于CPEB对活性依赖信号的敏感性不会改变其树突分布，这表明树枝上的活性部位不是RNP颗粒定位的目标。然而，非活性的CPEB在末梢树突状分支的颗粒中积累，支持这样的假设，即激活后CPEB及其mRNA货物从颗粒中释放出来，然后可用于树突状细胞的翻译。
Cytoplasmic Polyadenylation Element Binding protein (CPEB) is an RNA binding protein involved in dendritic delivery of mRNA and activity-dependent, polyadenylation-induced translation of mRNAs in the dendritic arbor. CPEB affects learning and memory and impacts neuronal morphological and synaptic plasticity. In neurons, CPEB is concentrated in ribonucleoprotein (RNP) granules that distribute throughout the dendritic arbor and localize near synapses, suggesting that the trafficking of RNP granules is important for CPEB function. We tagged full-length CPEB and an inactive mutant CPEB with fluorescent proteins, then imaged rapid dendritic branch dynamics and RNP distribution using two-photon time-lapse microscopy of neurons in the optic tectum of living Xenopus laevis tadpoles. Though the inactive CPEB mutant transports mRNA in the dendritic arbor, its expression interferes with CPEB-dependent translation because it is incapable of activity-triggered mRNA polyadenylation. In dendrites, the distributions of the active and inactive CPEB-containing RNP granules do not differ; the RNP granules are dense and their positions do not correlate with sites of rapid dendritic branch dynamics or the eventual fate of the dendritic branches. Because CPEB's sensitivity to activity-dependent signaling does not alter its dendritic distribution, it indicates that active sites in the dendritic arbor are not targeted for RNP granule localization. Nevertheless, inactive CPEB accumulates in granules in terminal dendritic branches, supporting the hypothesis that upon activation CPEB and its mRNA cargo are released from granules and are then available for dendritic translation.