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

2007年，我们发现Nε-赖氨酸乙酰化发生在内质网（ER）的内腔。 从最初的发现，我们继续发现整个ER乙酰化机制（一个膜 转运蛋白AT-1/SLC 33 A1和两种乙酰转移酶ATase 1和ATase 2），并揭示了一种新的 ER生物学。具体来说，我们发现ER乙酰化机制调节ER内的蛋白稳态 通过维持质量控制/分泌途径的参与之间的平衡， 通路和网状吞噬。通过结合使用生物化学和高清晰度质谱，我们 发现SLC 25 A1和SLC 13 A5作为AT-1的重要“代谢伙伴”。 AT-1/SLC 33 A1、SLC 25 A1或SLC 13 A5的纯合突变与发育迟缓相关 而杂合突变与类似形式的脑病有关 遗传性感觉和自主神经病变（HSAN），包括痉挛性截瘫的特殊形式。 重要的是，这些突变要么引入提前终止密码子，要么导致转录因子的功能丧失。 运输机此外，AT-1/SLC 33 A1、SLC 25 A1或SLC 13 A5的基因重复事件与 自闭症谱系障碍（ASD），智力残疾和早衰样畸形。扩大我们 在研究中，我们产生了神经元特异性（AT-1 nTg，SLC 25 A1 nTg，和SLC 13 A5 nTg）和系统性（AT-1 sTg， SLC 25 A1 sTg和SLC 13 A5 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，这是基础， 与整个生命周期中的神经退行性疾病和神经发育疾病密切相关。以补充 上述研究和解剖的具体作用的两个AT酶，下游的AT-1，我们还产生了 Atase 1-/-和Atase 2-/-小鼠。它们的表型支持这两种基于ER的乙酰转移酶 已经进化到扮演部分不同的角色。本研究的一般假设是SLC 25 A1， SLC 13 A5和AT-1协同作用以调节分泌途径的参与和诱导细胞凋亡。 网状吞噬具体目标1将测试ER乙酰化机制是下游的假设。 靶向由AT-1、SLC 25 A1或 SLC13A5。Specific Aim 2将使用我们新产生的Atase 1-/-和Atase 2-/-小鼠来测试以下假设： ATase 1和ATase 2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下游靶点的特定结构特征允许精细调节网状吞噬作用。在 结论，这个建议是我们实验室新发现的结果;它将帮助我们剖析 严重的神经退行性和神经发育疾病的分子机制， 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ER的其他领域。 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.