Modulation Of Neuronal Channels & Receptors in the Brain

神经元通道的调节

• 批准号: 7007493
• 负责人: JERREL L YAKEL
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF ENVIRONMENTAL HEALTH SCIENCES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/7007493
• 关键词: Alzheimer' s disease; Xenopus oocyte; acetylcholine; calcium channel; electrophysiology; hippocampus; interneurons; intracellular membranes; laboratory rat; membrane channels; neural degeneration; neural transmission; neurotransmitter receptor; nicotinic receptors; polymerase chain reaction; receptor expression; serotonin; serotonin receptor; tissue /cell culture; voltage /patch clamp

Summary of Work: Neuronal communication between cells in the nervous system occurs at the synapse, where the release of neurotransmitter by the presynaptic terminal diffuses across the synaptic cleft and binds to and activates various ligand-gated ion channels on the postsynaptic membrane. To understand the basic mechanisms and regulation of synaptic transmission in the CNS, the lab is focusing on the function and regulation of the ligand-gated ion channels gated by acetylcholine (Ach; this is referred to as the nicotinic receptor) and serotonin (i.e., the 5-HT3 receptor, or 5-HT3R) in the hippocampus. The hippocampus is implicated in memory formation in humans and animals, and is an important site in relation to a variety of neurodegenerative diseases such as Alzheimer's. Therefore, conditions or agents that may have an effect on the development of the hippocampus can have severe consequences in terms of cognitive deficits. In 1997, we discovered that hippocampal inhibitory interneurons contain functional somato-dendritic nicotinic receptors; since then three other leading laboratories have confirmed and extended our findings. To understand how the nicotinic receptors are regulating hippocampal function, we are currently focusing on the cellular and molecular aspects of these channels. As there are more than ten different nicotinic receptor subunits known to be expressed in the mammalian brain, we have been using patch-clamp electrophysiological studies in conjunction with single-cell RT-PCR studies in order to investigation the cellular expression patterns of these different nicotinic receptor subunits from cells where we can also functional study the protein. We have discovered that different populations of neurons within the hippocampus express different nicotinic receptor subunits; as the properties of the responses is also different, we have been successful at correlating the expression patterns with functional properties. We are also quantifying the molecular properties of the channels because the exact molecular makeup will determine different aspects of receptor function. For example we have been studied the single-channel properties of nicotinic receptors and find that there are two different channels present in hippocampal interneurons. The properties of these channels has allowed us to make estimates of molecular structure. Finally we are using focal uncaging of nicotinic ligands in order to map the location of functional receptors on the hippocampal interneurons. All of these approaches in general will allow us to determine better what the molecular makeup of the nicotinic receptors are, but also how functional receptors are distributed. Such information is critical to understand how this receptor control hippocampal activity. Although the nicotinic and 5-HT3R channels are known to be involved in a variety of physiological processes, the precise nature of these actions are not currently known, and our findings may help to understand the role that Ach and 5-HT have in regulating hippocampal neuronal activity and possibly cognitive processes. For example, approximately 25% of pregnant women smoke and exposure to nicotine in utero, both in rats and humans, is known or suspected to cause a variety of developmental abnormalities, including brain damage and cognitive impairment. Nicotine may also have positive physiological effects. For example patients with Alzheimer's disease have fewer nicotinic binding sites in the hippocampus, and nicotine alleviates some symptoms in Alzheimer's patients. Mutations in a nicotinic receptor subtype has also been linked to a rare form of epilepsy. The 5-HT3R is also known to serve important functional roles in the CNS; e.g., 5-HT3 ligands may be powerful anxiolytic agents, useful for the relief of migraines, and powerful cognition-enhancing agents. Besides our work in the hippocampus, we have found that subunits of the 5-HT3 and nicotinic receptors can co-assemble to form a novel type of heteromeric ion channel with an enhanced permeability to calcium; this is the first such evidence of promiscuous co-assembly of receptor subunits from different neurotransmitter receptors. We are currently exploring whether this co-assembly may play a significant role in regulating neuronal activity in the brain. Interestingly, as hippocampal inhibitory interneurons selectively express both functional 5-HT3 and nicotinic receptors, it is possible that 5-HT3 and nicotinic subunits may therefore co-assemble in these neurons, resulting in a channel highly permeable to calcium that in turn regulates neuronal activity and therefore the release of GABA from these neurons.

工作摘要：神经系统中细胞之间的神经元通讯发生在突触处，突触前末端释放的神经递质扩散穿过突触间隙，并结合并激活突触后膜上的各种配体门控离子通道。为了了解中枢神经系统突触传递的基本机制和调节，实验室重点研究由乙酰胆碱（Ach；这被称为烟碱受体）和血清素（即，海马体中的 5-HT3 受体（或 5-HT3R）。海马体与人类和动物的记忆形成有关，并且是与阿尔茨海默病等多种神经退行性疾病相关的重要部位。因此，可能影响海马体发育的条件或因素可能会对认知缺陷产生严重后果。 1997年，我们发现海马抑制性中间神经元含有功能性体细胞树突烟碱受体；此后，其他三个领先的实验室也证实并扩展了我们的发现。为了了解烟碱受体如何调节海马功能，我们目前关注这些通道的细胞和分子方面。由于已知在哺乳动物大脑中表达有十多种不同的烟碱受体亚基，因此我们一直使用膜片钳电生理学研究与单细胞 RT-PCR 研究相结合，以研究这些不同烟碱受体的细胞表达模式从细胞中提取受体亚基，我们还可以对蛋白质进行功能研究。我们发现海马体内不同的神经元群表达不同的烟碱受体亚基；由于响应的属性也不同，我们已经成功地将表达模式与功能属性相关联。我们还量化了通道的分子特性，因为确切的分子组成将决定受体功能的不同方面。例如，我们研究了烟碱受体的单通道特性，发现海马中间神经元中存在两种不同的通道。这些通道的特性使我们能够估计分子结构。最后，我们使用烟碱配体的局灶解笼来绘制海马中间神经元上功能受体的位置。所有这些方法总体上将使我们能够更好地确定烟碱受体的分子组成，以及功能性受体的分布方式。这些信息对于理解这种受体如何控制海马活动至关重要。尽管已知烟碱通道和 5-HT3R 通道参与多种生理过程，但这些作用的确切性质目前尚不清楚，我们的研究结果可能有助于理解 Ach 和 5-HT 在调节海马中的作用神经元活动和可能的认知过程。例如，大约 25% 的孕妇在子宫内吸烟和接触尼古丁（无论是大鼠还是人类），已知或怀疑会导致各种发育异常，包括脑损伤和认知障碍。尼古丁还可能具有积极的生理作用。例如，阿尔茨海默病患者的海马体中烟碱结合位点较少，尼古丁可以缓解阿尔茨海默病患者的一些症状。烟碱受体亚型的突变也与一种罕见的癫痫有关。 5-HT3R 也被认为在 CNS 中发挥重要的功能作用。例如，5-HT3配体可能是强效抗焦虑剂，可用于缓解偏头痛，也是强效认知增强剂。除了我们在海马体中的工作外，我们还发现 5-HT3 和烟碱受体的亚基可以共同组装形成一种​​新型异聚离子通道，其对钙的渗透性增强；这是来自不同神经递质受体的受体亚基混杂共同组装的第一个证据。我们目前正在探索这种共组装是否可能在调节大脑神经元活动中发挥重要作用。有趣的是，由于海马抑制性中间神经元选择性表达功能性 5-HT3 和烟碱受体，因此 5-HT3 和烟碱亚基可能在这些神经元中共同组装，形成一个对钙高度渗透的通道，进而调节神经元活动因此这些神经元会释放 GABA。