Signaling mechanisms of the pro Brain Derived Neurotrophic Factor (proBDNF) and the prodomain BDNF (pBDNF) in neurons

研究概要：神经元是一种可兴奋的细胞，它可以通过电脉冲与其他细胞进行交流，这种电脉冲被称为动作电位。神经元放电活动是编码与记忆和注意力有关的信息所必需的。我研究大脑中一种被称为“持续放电”的神经元活动模式。这种活动是指神经元在没有刺激的情况下保持其活动的特性，是短期记忆的基本机制。这种活动模式必须严格控制，以避免过度兴奋，并确保我们记住新学到的信息。我们需要了解神经元放电活动是如何被调节的，才能理解我们的大脑是如何运作的。我的长期职业目标是阐明与短期记忆有关的调节神经元活动的细胞和分子机制。假设1检验是一组被称为前神经营养因子的分泌因子调节神经元的放电模式。为了验证这一点，我将在老鼠身上使用电生理学、钙成像和行为研究。我的研究将使我对前神经营养因子对与短期记忆相关的神经元活动的作用有新的认识，并对这些因子对神经元的作用机制有新的发现。因为我们对持续放电的调节几乎一无所知，我预计我的研究将对其他研究记忆机制的实验室产生重大影响。我将重点关注两个短期目标来填补一些知识空白：目标1)阐明前eurotrophins proBrain Derived Neurotrophic Factor （proBDNF）作用于皮质神经元的细胞和分子机制，特别关注神经元突触活动。我将测试四个不相互排斥的假设。H1) proBDNF抑制毒蕈碱受体的激活。H2) proBDNF抑制皮层神经元中的TRPC4和TRPC5通道。H3) proBDNF抑制皮质神经元电压门控钙通道（VGCC）。H4) proBDNF通过打开钾离子通道促进皮质神经元的超极化。目的2)详细描述由proBDNF切割产生的肽对与短期记忆和注意相关的神经元活动的影响。在生理条件下，嗜前eurotrophin proBDNF被分裂成两个实体：肽pBDNF和成熟BDNF。20%的人携带pBDNF的突变形式，称为pBDNFMet66。这些肽的标准形式和突变形式的确切功能在很大程度上是未知的。在接下来的五年里，我提出了一系列的实验，以更好地表征pBDNFMet66对皮层神经元突触活动和持续放电的影响。从目标1和目标2中获得的新数据和知识将对神经营养因子领域产生重大影响，并将大大增加我们对记忆形成机制的理解。

Summary of Research: Neurons are excitable cells that can communicate with other cells via electrical impulses, known as action potential. Neuronal firing activity is necessary to encode messages related to memory and attention. I study a neuronal pattern of activity called "persistent firing" in the brain. This activity refers to the property of neurons to sustain their activity while no stimulus is present and it is an essential mechanism for short-term memory. This pattern of activity must be tightly regulated to avoid hyperexcitability and to ensure that we memorize newly learned information. We need to understand how neuronal firing activity is regulated to understand how our brain functions. My long-term career goal is to elucidate cellular and molecular mechanisms regulating neuronal activity related to short-term memory. A hypothesis I test is that a group of secreted factors, known as proneurotrophic factors regulate neuronal firing pattern. To test this, I will employ electrophysiology, calcium imaging and behavioural studies in mice. My research will lead to new knowledge about the role of proneurotrophic factors on neuronal activity related to short-term memory, and new discoveries about the mechanism of action of these factors on neurons. Because we know almost nothing about the regulation of persistent firing, I anticipate that my research will have a significant impact on other laboratories studying the mechanisms of memory. I will focus on two short-term objectives to fill several gaps of knowledge: Objective 1) To elucidate the cellular and molecular mechanisms of action of the proneurotrophins proBrain Derived Neurotrophic Factor (proBDNF) on cortical neurons, with a specific attention on neuronal synaptic activity. I will test four non-mutually exclusive hypotheses. H1) proBDNF inhibits the activation of muscarinic receptors. H2) proBDNF inhibits TRPC4 and TRPC5 channels in cortical neurons. H3) proBDNF inhibits voltage-gated calcium channel (VGCC) in cortical neurons. H4) proBDNF promotes the hyperpolarization of cortical neurons via the opening of potassium channels. Objective 2) To characterize in detail the effect of a peptide resulting from the cleavage of the proBDNF on neuronal activity related to short term memory and attention. In physiological conditions the proneurotrophin proBDNF is cleaved into two entities: a peptide pBDNF and the mature BDNF. 20% of the human population carries a mutated form of the pBDNF known as pBDNFMet66. The exact functions of the standard form and the mutated form of these peptides are largely unknown. Over the next five years, I propose a series of experiments to better characterize the effect of the pBDNFMet66 on synaptic activity and persistent firing in cortical neurons. New data and knowledge obtained from Objective 1 and 2 will have a significant impact on the neurotrophin field and will considerably increase our understanding of mechanisms underlying memory formation.