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

Pur α在神经元细胞质中强烈表达，参与细胞功能的多个方面。之前，我们报道过该蛋白控制BC1 RNA的表达及其随后在树突内的分布，并且pur α与多核糖体有关。在这里，我们报道，在EDTA治疗后，pur - α从mRNA/蛋白复合物（mRNPs）的多核糖体中释放出来，该复合物还含有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。由于抗pur α抗体对这些蛋白的共免疫沉淀被Rnase处理消除，pur α可能以rna依赖的方式协助mRNP组装，并与其他rna结合蛋白合作将mRNP靶向多核糖体。含有mStaufen-和fmrp的mRNPs的免疫沉淀提供了额外的证据，证明抗pur α检测到分布在体树突室的结构或功能相关的mRNA亚群。此外，mRNPs似乎位于具有运动蛋白马达的粗内质网（rER）上。基于我们目前的发现，我们提出这种内质网结构可能形成了分子机制，介导和调节多核糖体沿着微管和肌动蛋白丝的多步运输，以及在体树突室中的局部翻译。最近，对mRNPs蛋白质成分的研究表明，涉及mRNA代谢或mRNA转运和翻译的蛋白质数量被包括在内。此外，一些树突mrna也与这些复合物相关。pur α蛋白与其他蛋白在神经元树突mRNA转运过程中所起的生物学作用值得进一步研究。

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.