Spastic paraplegia, neurodegeneration and autism: possible role for AT- 1/SLC33A1?

我们在2007年发现N-ε-赖氨酸乙酰化发生在内质网(ER)的管腔内。 从最初的发现，我们继续发现了整个ER乙酰化机制(一个膜 转运蛋白AT-1/SLC33A1和两个乙酰转移酶ATase1和ATase2)，并发现了一段新的 呃生物学。具体地说，我们发现内质网乙酰化机制调节内质网内的蛋白平衡 和分泌途径，通过维持分泌的质量控制/参与之间的平衡 途径和网状吞噬。通过生物化学和高清晰度质谱学的结合，我们 发现SLC25A1和SLC13A5是AT-1的重要“代谢伙伴”。 AT-1/SLC33A1、SLC25A1或SLC13A5纯合突变与发育迟缓相关 大脑和早期形式的脑病，而杂合突变与相似的形式有关 遗传性感觉和自主神经疾病(HSAN)，包括特殊形式的痉挛截瘫。 重要的是，这些突变要么引入过早的终止密码子，要么导致 传送者。此外，AT-1/SLC33A1、SLC25A1或SLC13A5的基因重复事件也存在关联 患有自闭症谱系障碍(ASD)、智力残疾和早衰症样变形症。为了扩大我们的 研究中，我们产生了神经元特异性的(AT-1 NTG、SLC25A1 NTG和SLC13A5 NTG)和全身性(AT-1 STG， SLC25A1 stg和SLC13A5 stg)过表达小鼠。这些动物表现出重要的表型。 相似之处，支持我们已经确定了一条统一的代谢途径的结论，该途径的基础是 一生中密切相关的神经退行性疾病和神经发育疾病。为了补充 以上研究和剖析了两个ATase的具体作用，下游的AT-1，我们也产生了 Atase1-/-和Atase2-/-小鼠。它们的表型支持这两种基于内质网的乙酰基转移酶的观点 已经进化到扮演部分不同的角色。本研究的一般假设是SLC25A1， SLC13A5和AT-1协同作用调节分泌途径的参与和诱导 网瘾。特定目标1将检验ER乙酰化机制是下游的假设 AT-1、SLC25A1或ASC25A1重复导致乙酰辅酶A胞浆到内质网功能障碍的靶点 SLC13A5。特定目标2将使用我们新产生的Atase1-/-和Atase2-/-小鼠来测试假设 ATase1和ATase2具有部分不同的生物学功能。具体目标3将检验这一假设 新发现的AT-1下游靶标的特殊结构特征允许微调网状噬菌体。在……里面 结论，这项建议是我们实验室新发现的结果；它将帮助我们剖析 严重神经退行性疾病和神经发育性疾病的终身分子机制及其意义 将使我们能够剖析ER的基本分子和生化功能，这些功能将影响到 生物医学研究。

We discovered that Nε-lysine acetylation occurs in the lumen of the endoplasmic reticulum (ER) in 2007. From that initial finding, we went on to discover the entire ER acetylation machinery (one membrane transporter, AT-1/SLC33A1, and two acetyltranferases, ATase1 and ATase2) and uncover a novel piece of ER biology. Specifically, we discovered that the ER acetylation machinery regulates proteostasis within the ER and secretory pathway by maintaining the balance between quality control/engagement of the secretory pathway and reticulophagy. By using a combination of biochemistry and high-definition mass spectrometry, we discovered that SLC25A1 and SLC13A5 act as important “metabolic partners” of AT-1. Homozygous mutations in AT-1/SLC33A1, SLC25A1 or SLC13A5 are associated with developmental delay of the brain and early forms of encephalopathy while heterozygous mutations are associated with similar forms of hereditary sensory and autonomic neuropathies (HSANs), including specific forms of spastic paraplegias. Important, these mutations either introduce a premature STOP codon or cause loss-of-function of the transporters. Furthermore, gene duplication events of AT-1/SLC33A1, SLC25A1 or SLC13A5 are associated with autism spectrum disorder (ASD), intellectual disability, and progeria-like dysmorphism. To expand our studies, we generated neuron-specific (AT-1 nTg, SLC25A1 nTg, and SLC13A5 nTg) and systemic (AT-1 sTg, SLC25A1 sTg, and SLC13A5 sTg) overexpressing mice. These animals display important phenotypic similarities, supporting the conclusion that we have identified a unified metabolic pathway that is at the basis of closely related neurodegenerative and neurodevelopmental diseases across lifespan. To complement the above studies and dissect the specific role of the two ATases, down-stream of AT-1, we have also generated Atase1-/- and Atase2-/- mice. Their phenotype supports the idea that these two ER-based acetyltransferases have evolved to play partially divergent roles. The GENERAL HYPOTHESIS of this research is that SLC25A1, SLC13A5, and AT-1 act in concert to regulate engagement of the secretory pathway and induction of reticulophagy. Specific Aim 1 will test the hypothesis that the ER acetylation machinery is the downstream target of a dysfunctional cytosol-to-ER flux of acetyl-CoA caused by the duplication of AT-1, SLC25A1 or SLC13A5. Specific Aim 2 will use our newly generated Atase1-/- and Atase2-/- mice to test the hypothesis that ATase1 and ATase2 have partially different biological functions. Specific Aim 3 will test the hypothesis that specific structural features of newly identified AT-1 downstream targets allow fine tuning of reticulophagy. In conclusion, this proposal is the result of novel discoveries made in our laboratory; it will help us dissect the molecular mechanisms of severe neurodegenerative and neurodevelopmental diseases across lifespan and it will allow us dissect essential molecular and biochemical functions of the ER that will impact other areas of biomedical research.