Neuron-specific deamidation of translational repressor 4E-BP2 in postnatal brain

大脑发育、学习、记忆和感知依赖于一个复杂的蛋白质网络，该网络协调人类大脑的高级认知功能。调节这些分子功能的重要生物过程是蛋白质合成，也称为翻译。翻译控制调节神经元之间连接强度的机制，这一过程称为突触可塑性。抑制翻译会阻碍长期记忆的形成，而刺激翻译则会促进记忆的形成。翻译是一个严格规范的过程。通过mTORC 1（雷帕霉素复合物1（mTORC 1）的机械靶点）调节的关键翻译控制途径涉及大脑发育，突触可塑性，学习和记忆。mTORC 1通过其主要下游靶点4 E结合蛋白2（4 E-BP 2）调节大脑中的翻译。最近的研究表明，4 E-BP 2经历自发的脑特异性天冬酰胺脱酰胺。然而，脑中4 E-BP 2脱酰胺的潜在机制和该过程的功能意义仍然未知。 我们的初步数据表明，脱酰胺形式的4 E-BP 2比野生型形式更不稳定，并且其稳定性响应于mTORC 1的抑制而增加。鉴于mTORC 1活性在出生后降低，这种机制可能解释了在出生后早期大脑发育过程中脱酰胺4 E-BP 2的积累。此外，我们发现当脱酰胺的4 E-BP 2在神经元中过表达时，翻译景观发生改变，表明4 E-BP 2的翻译后修饰可能调节mTORC 1/4 E-BP 2通路的输出并影响脑中mRNA的翻译。 在拟议的项目中，我们将进一步研究4 E-BP 2脱酰胺的机制，并研究其对脑功能的影响。具体来说，我们将产生表达脱酰胺但不表达野生型4 E-BP 2的转基因小鼠，并研究神经元活动和行为如何受到影响。我们将采用生物化学，电生理学，成像和行为学方法来研究4 E-BP 2脱酰胺对大脑在发育过程中和成年期的影响。 这项工作将为4 E-BP 2脱酰胺作用的作用和机制提供基本的见解，共同推进我们对翻译控制如何塑造大脑功能的理解。

Brain development, learning, memory, and perception rely on an intricate network of proteins that orchestrates higher cognitive functions of the human brain. An important biological process regulating the function of these molecules is protein synthesis, also termed translation. Translation controls the mechanisms regulating the strength of connection between neurons, a process called synaptic plasticity. Inhibition of translation blocks the formation of long-term memory and stimulation of translation promotes memory formation. Translation is a tightly regulated process. A key translational control pathway, regulated via the mTORC1 (mechanistic Target of Rapamycin Complex 1 (mTORC1)), is implicated in brain development, synaptic plasticity, learning, and memory. mTORC1 regulates translation in the brain via its major downstream target, 4E-binding protein 2 (4E-BP2). Recent studies have revealed that 4E-BP2 undergoes spontaneous brain-specific asparagine deamidation. However, the mechanisms underlying 4E-BP2 deamidation in the brain and the functional significance of this process remain unknown. Our preliminary data indicate that deamidated form of 4E-BP2 is less stable than wild-type form and its stability is increased in response to inhibition of mTORC1. Given that mTORC1 activity is reduced postnatally, this mechanism might explain the accumulation of deamidated 4E-BP2 during early postnatal brain development. Additionally, we found that translational landscape is altered when deamidated 4E-BP2 is overexpressed in neurons, suggesting that posttranslational modification of 4E-BP2 might regulate the output of mTORC1/4E-BP2 pathway and affect translation of mRNAs in the brain. In the proposed project, we will further investigate the mechanisms underlying 4E-BP2 deamidation and study its effect on brain functions. Specifically, we will generate genetically-modified mice expressing deamidated but not wild-type form of 4E-BP2, and study how neuronal activity and behaviours are affected. We will employ biochemical, electrophysiological, imaging and behavioral approaches to study the impact of 4E-BP2 deamidation on the brain during development and in adulthood. The proposed work will provide fundamental insights into the roles and mechanisms of 4E-BP2 deamidation, altogether advancing our understanding of how translational control shapes brain functions.