Mitochondrial control of protein translation in Fragile X

摘要 脆性X智力低下蛋白编码基因(Fmr1)功能丧失的研究结果 在不受调控的mRNA翻译和异常突触形态中。我们发现体内的线粒体 Fmr1/y小鼠的神经元有一个内膜泄漏，破坏了ATP的合成和 有助于复制表型，这是未成熟、分裂细胞的标志。以前的工作 在心肌细胞中的研究表明，发育成熟依赖于一个 线粒体膜渗漏。我们现在发现，ATP合成酶c-亚基轻度耗尽到 用三磷酸腺苷合成酶相互作用剂减少泄漏或抑制c-亚基泄漏 Fmr1-/y小鼠神经元和人成纤维细胞的mRNA翻译。防泄漏改变了 有利于氧化磷酸化的代谢。发育代谢开关可能是 依赖于刺激诱导的翻译延长因子2(EF2)的磷酸化，一种事件 这在Fmr1-/y突触中是缺乏的。我们的数据支持线粒体内膜的作用 在决定蛋白质翻译的速度和类型方面的效率。我们建议增加 封闭三磷酸腺苷合成酶c-亚基泄漏诱导的氧化磷酸化效率 突触刺激使EF2磷酸化后，通道产生线粒体ATP 改变突触蛋白质组。因此，我们将确定药理试剂是否 从Fmr1-/y分离的线粒体的记录中将减少内膜泄漏 突触以及这些试剂是否逆转了导致 Fmr1-/Y小鼠c-亚基表达增加和线粒体膜内漏 (目标1)。接下来我们将评估突触的形成和可塑性(目标2)和行为(目标3) 用地塞米松(Dex)和辅酶Q10封闭培养的神经元或体内的渗漏。德克斯是 一种细胞死亡调节剂，与三磷酸腺苷合成酶的OSCP/b亚单位结合并关闭三磷酸腺苷 合酶泄漏，不影响免疫系统。它可以轻易地穿过血脑屏障， 增强神经元中的ATP生成，最近在患者中进行了研究。因此，Dex和 如果成功，CoQ10具有极好的翻译潜力。最后，我们将杂交Fmr1-/Y 携带转基因三磷酸腺苷合成酶c亚单位环的小鼠以确定 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，所需的 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.