The COPA vesicle protein and pathogenesis of spinal muscular atrophy

描述（由申请人提供）：我们发现SMN蛋白与α-COP结合，α-COP是七聚体COPI囊泡的最大成分。在这个项目中要研究的假设是SMA的发病机制是由于这种货物运输复合物不能维持运动神经元的功能完整性。我们探索SMN蛋白与α-COP的相互作用在神经突发育和维持中的作用。重要的是，我们观察到α-COP的过表达恢复了SMN耗尽的NSC 34细胞中的神经突发育。新的数据表明，低水平的SMN改变内质网-高尔基体运输的功能，这表明以前未被认识到的影响，这一蛋白质加工途径。我们最近报道，α-COP复合物包含来自分化的NSC-34细胞的总转录组的约800个特异性RNA。这些mRNA的高比例在其3'非翻译区中含有G-四链体基序，其已被指定在神经突定位中起作用。我们的目标是确定依赖于SMN与COPI复合物相关的mRNA，从而能够研究α-COP和SMN在将这些RNA运输到轴突中的作用，并表征其对神经元发育的需求。为了研究SMN与α-COP相互作用的生物生理学意义以及随后的机制研究，我们产生了α-COP蛋白水平降低的新型转基因小鼠，预测这将导致运动单位功能障碍。我们还创建了过表达标记的人α- COP的转基因菌株。这些小鼠将与具有低水平SMN的SMA模型小鼠杂交，以检验以下假设：增加的α-COP和COPI囊泡水平促进SMN依赖性货物递送至轴突并恢复运动技能和延长寿命。这些实验小鼠模型将是研究神经变性机制以及蛋白质和特定RNA向轴突和轴突内转运的重要资源。COPI通路的药理学诱导可能代表治疗SMA的新方法。

DESCRIPTION (provided by applicant): We discovered that the SMN protein binds to alpha-COP, the largest constituent of the heptameric COPI vesicle. The hypothesis to be investigated in this project is that pathogenesis of SMA results from inability of this cargo transport complex to sustain the functional integrity of motor neurons. We explore the role of the SMN protein's interaction with alpha-COP in neurite development and maintenance. Importantly, we observed that over-expression of alpha-COP restores neurite development in SMN depleted NSC34 cells. New data reveal that low levels of SMN alter the functionality of endoplasmic reticulum-Golgi trafficking, suggesting a previously unrecognized effect on this protein processing pathway. We recently reported that the alpha-COP complex incorporates ~800 specific RNAs from the total transcriptome of differentiated NSC-34 cells. A high fraction of these mRNAs contain in their 3' untranslated regions a G-quadruplex motif, which has been assigned a role in neurite localization. Our goal is to identify the mRNAs that depend on SMN for association with the COPI complex, enabling studies of the roles of alpha-COP and SMN in the trafficking of these RNAs into the axon and characterization of their requirement for neuronal development. To examine the biological physiologic significance of the interaction of SMN with alpha-COP and subsequent mechanistic studies, we generated novel transgenic mice with reduced levels of alpha-COP protein, with the prediction this will result in motor unit dysfunction. We also have created a transgenic strain that over-expresses tagged human alpha- COP. These mice will be crossed with SMA model mice with low levels of SMN to test the hypothesis that increased levels of alpha-COP and COPI vesicles promote SMN dependent cargo delivery to the axon and restore motor skills and increase lifespan. These experimental mouse models will be important resources to study the mechanism of neurodegeneration and the transport of proteins and specific RNAs to and within the axon. Pharmacologic induction of the COPI pathway may represent a novel means to treat SMA.