Mitochondrial control of protein translation in Fragile X

摘要 编码脆性X智力低下蛋白（FMRP）的基因（Fmr 1）功能丧失导致 不受控制的mRNA翻译和异常的突触形态。我们发现， Fmr 1-/y小鼠的神经元具有破坏ATP合成的内膜渗漏， 有助于复制表型，这是不成熟的分裂细胞的标志。以前的工作 在心肌细胞中的研究表明，发育成熟依赖于关闭一个 线粒体膜渗漏。我们现在发现ATP合酶c亚基的轻度缺失， 减少渗漏或用ATP合酶相互作用剂抑制c-亚基渗漏 Fmr 1-/y小鼠神经元和人成纤维细胞中的mRNA翻译。泄漏抑制改变 代谢有利于氧化磷酸化。发育代谢开关可能是 依赖于刺激诱导的翻译延伸因子2（EF 2）磷酸化， 这是在Fmr 1-/y突触中缺乏的。我们的数据支持线粒体内膜 确定蛋白质翻译的速率和类型的效率。我们建议增加 ATP合成酶c亚基泄漏关闭诱导的氧化磷酸化效率 通道响应突触刺激产生线粒体ATP以磷酸化EF 2 改变突触蛋白质组。因此，我们将确定， 减少内膜泄漏将在从Fmr 1-/y分离的线粒体记录中起到这样的作用 突触，如果这些试剂逆转ATP合酶化学计量的变化， 在Fmr 1-/Y小鼠中增加的c-亚基表达和线粒体内膜渗漏 (Aim#1）。我们将评估突触形成和可塑性（目标#2）和行为（目标#3）， 使用右旋普拉克索（Dex）和辅酶Q10在培养的神经元中或在体内封闭渗漏。德克斯是 一种与ATP合酶的OSCP/B亚单位结合并关闭ATP的细胞死亡调节剂 合成酶泄漏而不影响免疫系统。它很容易穿过血脑屏障， 增强神经元中ATP的产生，最近在患者中进行了研究。因此，Dex和 辅酶Q10如果成功，具有很好的翻译潜力。最后，我们将杂交Fmr 1-/Y 小鼠与携带遗传修饰的ATP合酶c亚基环的小鼠，以确定 内膜渗漏的遗传减少挽救了FX突触表型。我们建议 FMRP调节线粒体代谢的刺激依赖性变化， 正常的突触发育和可塑性。

Abstract Loss of function of the gene (Fmr1) encoding Fragile X mental retardation protein (FMRP) results in unregulated mRNA translation and aberrant synaptic morphology. We find that mitochondria in neurons of the Fmr1-/y mouse have an inner membrane leak that undermines ATP synthesis and contributes to a replicative phenotype that is a hallmark of immature, dividing cells. Previous work in cardiomyocytes showed that developmental maturation is dependent on closure of a mitochondrial membrane leak. We now find that mild depletion of ATP synthase c-subunit to reduce the leak or inhibition of the c-subunit leak with ATP synthase interacting agents decreases mRNA translation in Fmr1-/y mouse neurons and human fibroblasts. Leak inhibition alters metabolism in favor of oxidative phosphorylation. The developmental metabolic switch may be dependent on stimulus-induced phosphorylation of translation elongation factor 2 (EF2), an event which is lacking in Fmr1-/y synapses. Our data support a role for mitochondrial inner membrane efficiency in determining the rate and type of protein translation. We suggest that increased oxidative phosphorylation efficiency induced by closure of the ATP synthase c-subunit leak channel produces mitochondrial ATP in response to synaptic stimulation to phosphorylate EF2 and change the synaptic proteome. Thus, we will determine if pharmacological reagents that decrease inner membrane leak will do so in recordings of mitochondria isolated from Fmr1-/y synapses and if these reagents reverse the change in ATP synthase stoichiometry that causes increased c-subunit expression and inner mitochondrial membrane leak in the Fmr1-/Y mouse (Aim#1). We will assess synapse formation and plasticity (Aim #2) and behavior (Aim #3) following closure of the leak in cultured neurons or in vivo using dexpramipexole (Dex) and CoQ10. Dex is a cell death modulator that binds to the OSCP/b subunit of ATP synthase and closes the ATP synthase leak without affecting the immune system. It readily crosses the blood brain barrier, enhances ATP production in neurons and was recently studied in patients. Thus, both Dex and CoQ10 have excellent translational potential if successful. Finally, we will cross breed Fmr1-/Y mice with mice harboring a genetically modified ATP synthase c-subunit ring to determine if genetic reduction of the inner membrane leak rescues the FX synaptic phenotype. We suggest that FMRP regulates a stimulus-dependent change in mitochondrial metabolism required for normal synaptic development and plasticity.