Studies on the role of Pur α in BC1 RNA transport in neuronal dendrites

Pur α参与细胞功能的各个方面，在神经元细胞质中强烈表达。以前，我们已经报道，这种蛋白质控制BC 1 RNA的表达和随后的分布在树突，和pur α与多聚核糖体。在这里，我们报告说，用EDTA处理后，pur α从mRNA/蛋白质复合物（mRNP）中的多聚核糖体释放，其中还含有mStaufen，脆性X智力迟钝蛋白（FMRP），肌球蛋白Va和其他功能未知的蛋白质。由于RNA酶处理消除了抗pur α抗体对这些蛋白质的共免疫沉淀，因此pur α可能以RNA依赖性方式协助mRNP组装，并与其他RNA结合蛋白合作参与将mRNP靶向多核糖体。含有mStaufen和FMRP的mRNP的免疫沉淀提供了额外的证据，即抗pur α检测到分布在体树突区室中的结构或功能相关的mRNA亚群。此外，mRNP似乎驻留在粗面内质网（rER）配备驱动蛋白电机。基于我们目前的研究结果，我们提出，这种rER结构可能形成的分子机制，介导和调节多聚核糖体沿着微管和肌动蛋白丝的多步运输，以及本地化的翻译在somatodendritic compartment.More最近，对mRNP的蛋白质组分的研究表明，涉及的mRNA的代谢或mRNA的运输和翻译的蛋白质的数量包括在内。此外，一些树突状的mRNA也与这些复合物。进一步研究pur α蛋白与其他蛋白在神经元树突mRNA转运过程中的生物学作用具有重要意义。

Pur alpha, which is involved in diverse aspects of cellular functions, is strongly expressed in neuronal cytoplasm. Previously, we have reported that this protein controls BC1 RNA expression and its subsequent distribution within dendrites, and that pur alpha is associated with polyribosomes. Here, we report that, following treatment with EDTA, pur alpha was released from polyribosomes in mRNA/ protein complexes (mRNPs), which also contained mStaufen, Fragile X Mental Retardation Protein (FMRP), myosin Va and other proteins with unknown functions. As the coimmunoprecipitation of these proteins by an anti-pur alpha antibody was abolished by Rnase treatment, pur alpha may assist mRNP assembly in an RNA-dependent manner, and be involved in targeting mRNPs to polyribosomes in cooperation with other RNA-binding proteins. The immunoprecipitation of mStaufen- and FMRP-containing mRNPs provided additional evidence that the anti-pur alpha detected structurally or functionally related mRNA subsets which are distributed in the somatodendritic compartment. Furthermore, mRNPs appear to reside on rough endoplasmic reticulum (rER) equipped with a kinesin motor. Based on our present findings, we propose that this rER structure may form the molecular machinery that mediates and regulates multi-step transport of polyribosomes along microtubules and actin filaments, as well as localized translation in the somatodendritic compartment.More recently, studies on protein components of the mRNPs revealed that number of proteins implicated in metabolism of mRNAs or mRNA transport and translation were included. Moreover, several dendritic mRNAs were also associated with these complexes. It would be intriguing to further study the biological roles of pur alpha protein, together with other proteins, played in the process of mRNA transport in the neuronal dendrites.