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

研究概述：神经元是可兴奋的细胞，可以通过电脉冲（称为动作电位）与其他细胞进行交流。神经元放电活动是编码与记忆和注意力相关的信息所必需的。我研究的是大脑中一种叫做“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维持其活动的特性，它是短期记忆的重要机制。这种活动模式必须受到严格的调节，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调节的，以了解我们的大脑如何运作。我的长期职业目标是阐明调节与短期记忆相关的神经元活动的细胞和分子机制。一个假设我测试是一组分泌的因子，称为proneurotrophic因子调节神经元放电模式。为了验证这一点，我将在小鼠身上进行电生理学、钙成像和行为研究。我的研究将导致有关proneurotrophic因子对与短期记忆相关的神经元活动的作用的新知识，以及有关这些因子对神经元的作用机制的新发现。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。我将集中在两个短期目标，以填补几个知识空白：目标1）阐明proneurotrophins proBrain Derived Neurotrophic Factor（proBDNF）对皮质神经元的细胞和分子作用机制，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抑制皮质神经元中的TRPC 4和TRPC 5通道。H3）proBDNF抑制皮质神经元中的电压门控钙通道（VGCC）。H4）proBDNF通过开放钾通道促进皮层神经元的超极化。 目的（2）研究脑源性神经营养因子原（proBDNF）裂解后产生的肽段对短时记忆和注意相关神经元活动的影响。在生理条件下，原神经营养因子proBDNF被切割成两个实体：肽pBDNF和成熟的BDNF。20%的人类携带突变形式的pBDNF，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pBDNFMet 66对突触活动和皮层神经元持续放电的影响。 从目标1和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.