Cellular physiology of epilepsy-associated KCNQ2 channels

描述(申请人提供)：KCNQ通道家族包括五个基因，称为KCNQ1-5。大多数家庭成员都需要神经系统或心血管系统的正常功能，因为KCNQ基因的功能突变会导致LQTS综合征(KCNQ1)、进行性听力损失(Kcnq4)和良性家族性新生儿惊厥(BFNC)，这是一种儿童癫痫(KCNQ2、Kcnq3)。KCNQ2/3异构体通道被认为是M电流的中介，M电流是一种亚阈值激活钾电导，控制中枢神经系统神经元的兴奋性。然而，与KCNQ3通道不同的是，与BFNC相关的90%以上的突变被映射到KCNQ2基因位点，KCNQ2基因敲除小鼠在出生后24小时内死亡。因此，KCNQ2可能是大脑中主要的KCNQ亚基，也可能在其他生理过程中发挥独特的作用。我们的长期目标是了解KCNQ通道的体内功能以及这些通道的突变如何导致癫痫发生。该项目的总体目标是确定KCNQ2通道在控制神经元内在兴奋性中的作用。为了实现我们的目标，我们将结合药理学、蛋白质工程、遗传学和电生理学。使用这些方法，我们将首先利用最近发现的KCNQ2特异性抑制剂来确定KCNQ2通道对跨发育的M电流的功能贡献。我们随后将使用功能增益突变和新的药理学来测试KCNQ2通道是否构成大脑中的多个电导。最后，我们将利用KCNQ2条件性基因敲除小鼠来测试KCNQ2通道在调节静息和活性膜特性中的作用。这些研究将在小鼠脑片上进行，使用电流和电压钳记录。我们将使用海马体作为一个模型脑区，因为它与癫痫以及学习和记忆有关。这些研究的结果将提供对一个重要的钾通道的洞察，该通道在限制大脑中不受控制的神经元活动和癫痫发作方面发挥着基础性作用。 公共卫生相关性：钾通道KCNQ2功能障碍导致儿童癫痫良性家族性新生儿惊厥，但这些通道影响神经元活动的机制尚不清楚。我们的目标是揭开KCNQ2通道在正常大脑中所起的确切生理作用。这些工作将提供对防止癫痫发生的内在机制的更好理解，并可能导致新型抗癫痫药物的开发。

DESCRIPTION (provided by applicant): The KCNQ channel family includes five genes, known as Kcnq1-5. Most family members are required for proper function of either the nervous or cardiovascular system as loss of function mutations in Kcnq genes lead to LQTS syndrome (Kcnq1), progressive hearing loss (Kcnq4) and benign familial neonatal convulsions (BFNC), a pediatric epilepsy (Kcnq2, Kcnq3). KCNQ2/3 heteromeric channels are thought to mediate the M-current, a sub-threshold activating potassium conductance that controls the excitability of CNS neurons. However, unlike KCNQ3 channels, more than 90% of mutations related to the BFNC are mapped to the Kcnq2 gene locus and Kcnq2 knockout mice die within 24 hours after birth. Thus, Kcnq2 may either be the primary KCNQ subunit in the brain or it may play a unique role in additional physiological processes. Our long-term goal is to understand the in vivo functions of KCNQ channels and how mutations in these channels lead to epileptogenesis. The overall goal of this project is to determine the role of KCNQ2 channels in controlling intrinsic neuronal excitability. To achieve our objective we will combine pharmacology, protein engineering, genetics, and electrophysiology. Using these approaches we will first establish the functional contribution of KCNQ2 channels to the M-current across development using a recently identified KCNQ2-specific inhibitor. We will subsequently test whether KCNQ2 channels underlie multiple conductances in the brain using gain-of-function mutations and novel pharmacology. Lastly, we will test the role of KCNQ2 channels in regulating resting and active membrane properties using Kcnq2 conditional knockout mice. These studies will be conducted in mouse brain slices using current- and voltage-clamp recordings. We will use hippocampus as a model brain area because it is implicated in epilepsy and learning and memory. The results from these studies will provide insight into an important potassium channel that plays a fundamental role in limiting unchecked neuronal activity and seizures in the brain. PUBLIC HEALTH RELEVANCE: Dysfunction of the potassium channel KCNQ2 leads to the pediatric epilepsy benign familial neonatal convulsions, but the mechanisms by which these channels affect neuronal activity are not well-understood. Our goal is to unravel the precise physiological role KCNQ2 channels play in the normal brain. Such work will provide an improved understanding of innate mechanisms that prevent epileptogenesis and could lead to the development of novel anti-epileptic drugs.