Physiological roles of Kv1.1 RNA editing

描述（由申请人提供）：电压门控钾通道在大脑电信号形成中起重要作用。电压门控钾通道的Kv1.1亚型与动作电位传播的调节有关，Kv1.1基因的突变与1型发作性共济失调（EA1）有关，EA1是一种主要的人类神经系统疾病，临床表现多种多样，包括应激性共济失调、肌无力、神经肌强直和癫痫。编码Kv1.1通道亚基的RNA转录本受到腺苷-肌苷RNA编辑事件的影响，其中基因组编码的异亮氨酸密码子（AUU）在成熟mRNA中转化为缬氨酸密码子（IUU），从而改变编码通道蛋白400位的氨基酸特性。这种氨基酸残基位于高度

DESCRIPTION (provided by applicant): Voltage-gated potassium channels play an important role in shaping electrical signals in the brain. The Kv1.1- subtype of voltage-gated potassium channel has been implicated in modulating action potential propagation and mutations within the Kv1.1 gene are associated with episodic ataxia type-1 (EA1), a dominant human neurological disorder with widely variable clinical manifestations, including stress-induced ataxia, myokymia, neuromyotonia, and epilepsy. RNA transcripts encoding the Kv1.1 channel subunit are subject to an adenosine-to- inosine RNA editing event in which a genomically-encoded isoleucine codon (AUU) is converted to a valine codon (IUU) in the mature mRNA to alter the amino acid identity at position 400 of the encoded channel protein. This amino acid residue lies in the highly conserved ion-conducting pore of the channel and RNA editing is known to alter the rate of potassium channel inactivation in heterologous expression systems. To determine the physiological importance of this non-synonymous amino acid alteration, we have developed genetically- modified mouse lines that solely express either the non-edited (I) or edited (V) channel isoforms. In preliminary analyses, non-edited Kv1.1 (I)-expressing mice displayed phenotypic characteristics consistent with EA1, suggesting that modulation of Kv1.1 activity through editing is an important regulator of motor control and seizure susceptibility. The proposed studies will focus upon molecular, behavioral and neurophysiological characterization of Kv1.1 mutant animals with a particular focus on EA1-like phenotypes that have been observed in preliminary studies for non-edited Kv1.1 (I) mice. These studies will also determine the relationship between Kv1.1 editing compared to an established mouse model of EA1, engineered to bear a human mutation associated with this disorder. The initial characterization will quantify potential compensatory changes in gene expression for proteins involved in Kv1.1 signaling, as well as determine the time-frame in which homozygous Kv1.1 (I) animals die of an incompletely penetrant lethality, providing insights into the developmental importance of Kv1.1 editing. Behavioral analyses of various aspects of locomotor coordination will be performed under both control and stressed conditions since the motor dysfunction observed in EA1 is exacerbated by stress. In order to assess alterations in brain electrical activity for mutant Kv1.1 mice, electroencephalography (EEG) studies will monitor spontaneous seizures and chemical convulsants will be used to determine induced-seizure thresh- olds. To assess whether previously characterized EA1 mutations alter Kv1.1 function by missense amino acid incorporation or disruption of editing, we will use both in vitro and in vivo model systems to quantify editing profiles for EA1 mutants. Finally, we will employ electrophysiological techniques on Purkinje neurons in cerebellar slices to examine potential alterations in Kv1.1 channel kinetics. It is anticipated that the proposed studies will not only provide critical insights into he importance of RNA editing for the regulation of Kv1.1 function, but also into how altered editing for Kv1.1 transcripts may result in locomotor and neurological dysfunction.