Elucidating the role of the eIF2alpha kinase PERK in synaptic plasticity and memo

描述（申请人提供）：我们实验室的总体目标是了解突触可塑性和脊椎动物记忆形成的复杂分子机制。我的目标是确定rna依赖性蛋白激酶样内质网（ER） elF2a激酶（PERK）在这些过程中调节翻译的具体作用。PERK主要在胰腺细胞应激反应和全脑缺血中被研究；然而，其在蛋白质合成依赖性海马突触可塑性中的作用尚不清楚。在海马体中，新蛋白的产生已被证明是通过参与mRNA翻译起始的因素在可塑性过程中调节的。翻译起始的一个关键调控步骤是起始前三元复合物elF2-GTP-Met-tRNAiMet的形成，该复合物在mRNA被识别之前必须与40S核糖体结合。在每一轮翻译起始时，鸟嘌呤核苷酸交换因子elF2B需要将elF2-GDP循环到elF2-GTP以再生三元复合物。研究表明，elF2的a亚基磷酸化会抑制elF2B的活性，并最终减少翻译。在特定的细胞应激条件下，如内质网中未折叠蛋白的积累，PERK使elF2a磷酸化，并下调一般蛋白的合成。了解突触可塑性和记忆形成的分子机制对于理解这些过程中的错误如何导致认知障碍至关重要。为此，我建议进行实验研究，旨在探讨PERK在海马依赖行为、突触可塑性和海马长期增强（LTP）、长期抑郁（LTD）和记忆的关键信号转导通路调节中的作用。具体来说，我的目标是解决以下假设：1)mglur诱导的PKC信号调节PERK定向的elF2a磷酸化和PERK依赖的翻译；2)正常海马mGluR-LTD表达需要PERK；3)依赖海马体的学习和记忆形式需要PERK。蛋白质合成的改变已被证明伴随着几种人类神经系统疾病和神经退行性疾病，包括脆性X相关的智力迟钝、阿尔茨海默病（AD）、帕金森病（PD）和结节性硬化症。因此，异常的PERK功能可能是严重、衰弱的神经系统疾病的一个重要因素，而正常的PERK功能可能在参与学习和记忆的分子机制中发挥关键作用。

DESCRIPTION (provided by applicant): The overall goal of our lab is to understand the complex molecular mechanisms underlying synaptic plasticity and vertebrate memory formation. My goal is to determine the specific role that the RNA-dependent protein kinase-like endoplasmic reticulum (ER) elF2a kinase (PERK) plays in regulating translation during these processes. PERK primarily has been studied in pancreatic cellular stress response and global brain ischemia; however, its role in protein synthesis-dependent hippocampal synaptic plasticity is poorly understood. In the hippocampus, the generation of new proteins has been shown to be regulated during plasticity via factors involved in the initiation of mRNA translation. A key regulatory step in the initiation of translation is the formation of the preinitiation ternary complex elF2-GTP-Met-tRNAiMet, which is required to bind to the 40S ribosome prior to recognition of mRNA. Upon each round of translation initiation, the guanine-nucleotide exchange factor, elF2B, is required to recycle elF2-GDP to elF2-GTP to regenerate the ternary complex. It has been shown that phosphorylation of the a subunit of elF2 inhibits elF2B activity and eventually decreases translation. Under specific cellular stress conditions, such as an accumulation of unfolded proteins in the ER, PERK phosphorylates elF2a and functions to downregulate general protein synthesis. Understanding the molecular mechanism underlying synaptic plasticity and memory formation is critical to understanding how errors in these processes can lead to cognitive disorders. To this end, I propose experimental research aimed at examining the role of PERK in hippocampus-dependent behavior, synaptic plasticity and the regulation of signal transduction pathways critical to hippocampal long-term potentiation (LTP), long-term depression (LTD) and memory. Specifically, I aim to address the following hypothesis: 1) mGluR-induced PKC signaling modulates PERK-directed elF2a phosphorylation and PERK- dependent translation; 2) PERK is required for the expression of normal hippocampal mGluR-LTD; and 3) PERK is required for hippocampus-dependent forms of learning and memory. Altered protein synthesis has been shown to accompany several human neurological disorders and neurodegenerative diseases including Fragile X linked mental retardation, Alzheimer's disease (AD), Parkinson's disease (PD) and tuberous sclerosis. Thus, abnormal PERK function could be a significant factor underlying the manifestation in severe, debilitating neurological conditions, whereas normal PERK function could play a key role in the molecular mechanisms involved in learning and memory.