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

2007年，我们发现内质网（ER）腔内发生Nε-赖氨酸乙酰化。 从最初的发现开始，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 和两种乙酰转移酶 ATase1 和 ATase2）并发现了一个新的片段 ER 生物学。具体来说，我们发现内质网乙酰化机制调节内质网内的蛋白质稳态 通过维持质量控制/分泌参与之间的平衡来调节和分泌途径 途径和网状噬菌体。通过结合生物化学和高清质谱分析，我们 发现SLC25A1和SLC13A5是AT-1的重要“代谢伙伴”。 AT-1/SLC33A1、SLC25A1 或 SLC13A5 的纯合突变与发育迟缓相关 大脑的疾病和早期形式的脑病，而杂合突变与类似的形式相关 遗传性感觉和自主神经病（HSAN），包括特定形式的痉挛性截瘫。 重要的是，这些突变要么引入过早的终止密码子，要么导致密码子功能丧失。 运输者。此外，AT-1/SLC33A1、SLC25A1 或 SLC13A5 的基因重复事件也相关 患有自闭症谱系障碍 (ASD)、智力障碍和早衰样畸形。为了扩大我们的 研究中，我们生成了神经元特异性（AT-1 nTg、SLC25A1 nTg 和 SLC13A5 nTg）和系统性（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个统一的代谢途径的结论，该途径是 整个生命周期密切相关的神经退行性疾病和神经发育疾病。为了补充 通过以上研究并剖析了 AT-1 下游两种 ATase 的具体作用，我们还生成了 Atase1-/- 和 Atase2-/- 小鼠。它们的表型支持这样的观点：这两种基于内质网的乙酰转移酶 已经进化到扮演部分不同的角色。这项研究的一般假设是 SLC25A1， SLC13A5 和 AT-1 协同作用，调节分泌途径的参与和诱导 网状食食症。具体目标 1 将检验 ER 乙酰化机制是下游的假设 由 AT-1、SLC25A1 或 SLC13A5。具体目标 2 将使用我们新生成的 Atase1-/- 和 Atase2-/- 小鼠来测试以下假设： ATase1 和 ATase2 具有部分不同的生物学功能。具体目标 3 将检验以下假设： 新鉴定的 AT-1 下游靶标的特定结构特征允许对网状噬菌体进行微调。在 结论是，这个提议是我们实验室的新发现的结果；它将帮助我们剖析 整个生命周期严重神经退行性和神经发育疾病的分子机制及其 将使我们能够剖析内质网的基本分子和生化功能，这些功能将影响其他领域 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.