Cellular regulation of Sodium-activated Ion Channels

描述（由申请人提供）：Slack和Slick基因编码Na+激活的K+通道，其调节神经元适应维持突触刺激的速率和神经元动作电位计时的准确性。这些通道也被认为在保护神经元和心肌细胞免受缺氧损伤中起关键作用。在其一般结构中，它们类似于其他电压门控K通道，但具有非常大的（>600个氨基酸）细胞内C末端。Slack的C末端结构域与脆性X智力迟钝蛋白（FMRP）相互作用，FMRP是一种RNA结合蛋白，调节神经元mRNA子集的运输和翻译。本申请中的工作将使用生物化学和电生理学测定来确定Slack和FMRP在体外和体内参与其相互作用的特定区域，并将确定FMRP控制Slack通道门控所需的特定区域。我们还将确定如何在脆性X综合征（Fmr 1-/-）的小鼠模型中改变Na+激活的K+通道的表达。特别地，我们将确定在Fmr 1-/-动物中导致Slack的远端C-末端表达的完全丧失的机制，Slack是FMRP与通道结合所需的区域。平行的电生理和药理学实验将评估这种改变的Slack表达模式对天然神经元中Na+激活的K+通道的功能特性的影响。对Slack和Slick通道的生物学特性和调节的理解将导致对脆性X综合征和相关疾病的缺陷的更清楚的理解，并有望导致新的治疗策略的开发。 公共卫生相关性：最近的证据表明，相对新发现的一类蛋白质（称为钠激活钾通道）的激活通过它们与脆性X智力迟钝蛋白（FMRP）的结合来调节。FMRP的遗传性缺失或缺陷是遗传性智力障碍的主要原因。本申请中的实验将确定该通道-FMRP相互作用的机制和生物学后果。这些信息将用于评估这些通道是否可能是治疗上有用的药物靶点，特别是钠激活钾通道的药理学操作是否可以克服伴随FMRP丧失的神经元活动中的一些损伤。

DESCRIPTION (provided by applicant): The Slack and Slick genes encode Na+-activated K+ channels, which regulate the rate at which neurons adapt to maintained synaptic stimulation and the accuracy of timing of neuronal action potentials. These channels have also been proposed to play a key role in the protection of neurons and cardiomyocytes from hypoxic injury. In their general structure, they resemble other voltage-gated K channels, but have very large (>600 amino acid) intracellular C-termini. The C-terminal domain of Slack interacts with Fragile- X Mental Retardation protein (FMRP), an RNA-binding protein that regulates trafficking and translation of a subset of subset of neuronal mRNAs. The work in this application will use biochemical and electrophysiological assays to determine the specific regions of Slack and FMRP involved in their interactions both in vitro and in vivo, and will determine which specific regions are required for FMRP to control the gating of Slack channels. We shall also determine how the expression of Na+-activated K+ channels is altered in a mouse model of Fragile X syndrome (Fmr1-/-). In particular we shall determine the mechanism that in Fmr1-/- animals causes the total loss of expression of the distal C- terminus of Slack, a region that appears to be required for FMRP binding to the channels. Parallel electrophysiological and pharmacological experiments will evaluate the effects of this altered pattern of Slack expression on the functional properties of Na+- activated K+ channels in native neurons. An understanding of the biological properties and regulation of Slack and Slick channels will lead to a clearer understanding of the deficits in Fragile X syndrome and related disorders and is expected to lead to the development of novel therapeutic strategies. PUBLIC HEALTH RELEVANCE: Recent evidence suggests that activation of a relatively newly discovered class of proteins, termed sodium- activated potassium channels is regulated by their binding to Fragile X Mental Retardation Protein (FMRP). Inherited loss or deficits in FMRP are the leading cause of inherited intellectual disorders. The experiments in this application will determine the mechanisms and biological consequences of this channel-FMRP interaction. This information will be used to evaluate whether these channels are likely to be therapeutically useful drug targets, and in particular, whether pharmacological manipulations of sodium-activated potassium channels can overcome some of the impairments in neuronal activity that accompany loss of FMRP.