CRCNS: PKMzeta-Dependent Protein Synthesis Maintains Synaptic Plasticity

描述（由申请人提供）：我们都有可以追溯到我们年轻时的记忆;我们记得我们4岁时住过的房子;我们记得一位最喜欢的老师。存储这些记忆的机制被认为是特定神经元回路内突触连接的长期可塑性。然而，这种假定的记忆细胞基础依赖于蛋白质，这些蛋白质的寿命通常比记忆短得多。这正是长期记忆和突触可塑性的一个基本问题：如何在不断降解的蛋白质的基础上储存人类一生的记忆？最近研究表明，脑特异性PKC亚型蛋白激酶M β（PKM β）在维持突触的晚期长时程增强（L-LTP）和长时程记忆中起着独特的作用。然而，这一重要的观察结果并不能解释PKM β如何克服蛋白质周转和扩散的自然降解作用。该建议的中心假设是PKM β通过其自身合成的控制，可以形成双稳态系统，该系统可以解释突触特异性长期可塑性和记忆的维持。在这里，我们建议在一个生物物理模型中用数学公式表示这个假设，并分析这个模型，以便提出可检验的实验预测。然后，我们将直接测试这些预测PKM β介导的持久性突触增强，使用新的技术来测试的理论。智力优势：这一发现，PKM的突触可塑性和长期记忆的维持是必要的和足够的，从根本上改变了学习和记忆领域，但需要了解的机制，实际上可以实现长期的可塑性和记忆的持久性。本建议使用理论和实验相结合的方法解决这些问题。这种双稳定性依赖于翻译调节的理论不仅对神经科学而且对一般生物学来说都是新颖的。我们的合作是唯一有资格进行拟议的工作，因为Shouval实验室在与实验组合作建模突触可塑性方面有丰富的经验，Sacktor实验室开创了PKM？并且对所提出的技术具有丰富的经验。实验技术包括两个新的方法，必要的测试的预测。首先，我们建议测试该模型对L-LTP中蛋白质翻译的预测，不是通过可能具有毒性和间接作用的一般蛋白质合成抑制剂，而是通过使用针对PKM β mRNA翻译起始位点的反义寡核苷酸来特异性地阻断诱导和维持中的PKM β合成。其次，由于PKM β介导的增强作用既高度稳定又快速可逆，因此我们将使用为研究L-LTP维持而优化的快速流动海马切片室来测试模型的关键预测。在计算生物学中，所提出的依赖于双稳态的随机模拟也是新颖的。更广泛的影响：作为第一个被证明的大脑中经验依赖性长期信息存储的分子机制，PKM激酶具有重要的临床意义，并且在过去的一年中已被证明有助于多种神经和精神疾病的生物学，包括创伤后应激障碍，中枢神经性疼痛和药物滥用。为了帮助许多实验室对PKM模型的兴趣迅速增长，我们将使我们的模型可供更大的社区使用，允许其他科学家测试，修改并将他们的发现纳入模型，从而加快科学发现的步伐。因为NSF的一个重要目标是整合研究和教育，我们将培养多样化的学生。我们的实验室已经培训了本科生，Shouval实验室每年夏天都会通过一个REU项目（PI S。考克斯，赖斯），和UT系统赠款（PI H。Shouval）和当地本科生，而Sacktor实验室在指导当地弱势高中生方面有着悠久的历史（例如，通过英特尔计划）。这两个实验室都致力于公共宣传;例如，一篇关于PKM记忆和记忆的文章登上了《纽约时报》的头版。我们渴望将这种类型的推广扩展到生物科学理论与实验之间的相互作用领域。

DESCRIPTION (provided by applicant): We all have memories that date back to our youth; we remember the house we lived in at age 4; we remember a favorite schoolteacher. The mechanism for storing these memories is believed to be the long-term plasticity of synaptic connections within specific neuronal circuits. However, this putative cellular basis of memory relies on proteins that typically have lifetimes far shorter than the memory. Here exactly lies a fundamental problem of long-term memory and synaptic plasticity: How can memories be stored for a human lifetime on the basis of proteins that are continuously degrading? Recently, it was shown that the brain-specific PKC isoform, protein kinase Mζ(PKMζ), plays a unique role in maintaining both late long-term potentiation (L-LTP) of synapses and long-term memory. This crucial observation, however, does not explain how PKMζcan overcome the natural degrading effect of protein turnover and diffusion. The central hypothesis of this proposal is that PKMζ, through its control of its own synthesis, can form a bi-stable system, which can account for the maintenance of synapse specific long-term plasticity and memory. Here we propose to mathematically formulate this hypothesis within a biophysical model, and to analyze this model so as to propose testable experimental predictions. We then will directly test these predictions on PKMζ-mediated persistent synaptic potentiation, using novel techniques tailored for testing the theory. Intellectual Merit: The finding that PKMζ is both necessary and sufficient for the maintenance of synaptic plasticity and long-term memory has fundamentally changed the field of learning and memory, but much needs to be learned about the mechanisms that can actually accomplish the persistence of long-term plasticity and memory. This proposal addresses these questions using a combined theoretical and experimental approach. Such a theory in which bi-stability depends on regulation of translation is novel not only for neuroscience but also for biology in general. Our collaboration is uniquely qualified to carry out the proposed work because the Shouval lab has ample experience in modeling synaptic plasticity in collaboration with experimental groups, and the Sacktor lab has pioneered the science of PKM??and has ample experience with the proposed techniques. The experimental techniques include two new methodologies necessary for testing the predictions. First, we propose to test the model's predictions on protein translation in L-LTP, not by general protein synthesis inhibitors that may have issues of toxicity and indirect effects, but by use of antisense oligodeoxynucleotides directed to the translation start site of PKMζmRNA to specifically block PKMζ synthesis in induction and maintenance. Second, because PKMζ-mediated potentiation is both highly stable and yet rapidly reversible, we will use a fast-flow hippocampal slice chamber optimized for the study of the maintenance of L-LTP to test key predictions of the model. The proposed stochastic simulations of translation-dependent bi-stability are also novel in computational biology. Broader Impact: As the first demonstrated molecular mechanism of experience-dependent, long-term information storage in the brain, PKMζ has significant clinical implications, and within the last year has been shown to contribute to in the biology of a variety of neurological and psychiatric diseases, including post-traumatic stress disorder, central neuropathic pain, and drug abuse. In order to assist the rapidly growing interest in PKMζ in many labs, we will make our model accessible to the larger community, allowing for other scientists to test, modify, and incorporate their findings into the model, thus accelerating the pace of scientific discovery. Because an important goal for NSF is to integrate research and education, we will train a diverse pool of students. Our labs already train undergraduates, the Shouval lab takes undergraduates each summer through an REU program (PI S. Cox, Rice), and a UT system grant (PI H. Shouval), and local undergraduates throughout the year, and the Sacktor lab has had a long history of mentoring local disadvantaged high school students (e.g., through the Intel program). Both labs are dedicated to public outreach; for example, an article on PKMζ and memory was on the front page of The New York Times. We are eager to extend this type of outreach to the domain of the interaction between theory and experiment in biological sciences.