Molecular Components of A-type K+ channels

快速瞬态a型K+电流（IA），如阈下激活的神经元体树突a型K+电流（ISA）和心室肌细胞快速瞬态外向K+电流（Ito）对大脑和心脏的正常功能至关重要。在病理状态下，这些电流的异常可导致疾病状态，正如最近在颞叶癫痫患者中发现的那样。该项目解决了负责在哺乳动物神经元中产生这些电流的离子通道的分子性质。它试图建立这些通道的分子组成，并阐明鉴定的成分的生理意义。该基金支持的工作导致发现了一个与ISA通道相关的新蛋白家族，称为dppl，其中两个成员目前已知为DPPX（或DPP6）和DPP10。目前认为，神经元中的ISA通道是三元复合物，包括Kv4家族的主要或成孔亚基以及两种相关蛋白KChIPs和dppl。该应用主要集中在CA1海马锥体细胞，该神经元在空间学习和癫痫发病中起重要作用，并显著表达Kv4蛋白Kv4.2和DPPL、DPPX。本研究旨在验证DPPX是CA1神经元中Kv4通道重要组成部分的假设，确定通道的合理分布、生物物理特性和动态调节。Aim 1将利用在上一个资助期内获得的高特异性抗体来研究DPPX在CA1神经元树突中的定位及其与其他Kv4通道成分的关系。Aim 2将利用DPPX基因敲除小鼠来研究DPPX消融对CA1神经元中Kv4通道分布和功能的影响。Aim 3探讨了DPPX对Kv4通道的作用方面，这些方面迄今为止很少受到关注：这种辅助亚基对蛋白激酶通道调节的影响，以及对质膜通道运输和表达的控制，以检验DPPX调节质膜上Kv4通道稳定性的假设。编码DPPX的基因突变与自闭症有关，这强调了了解这些蛋白质功能的重要性。

Fast transient A-type K+ currents (IA), such as the subthreshold-activating somato-dendritic A-type K+ currents in neurons (ISA) and the fast transient outward K+ current in cardiac ventricular myocytes (Ito) are essential for the proper functioning of the brain and the heart. During pathological conditions, abnormalities in these currents can contribute to disease conditions, as recently found in a patient with temporal lobe epilepsy. This project addresses the molecular nature of the ion channels responsible for the generation of these currents in mammalian neurons. It seeks to establish the molecular composition of these channels and to elucidate the physiological significance of the identified components. Work supported by this grant led to the discovery of a novel family of proteins that associates with ISA channels known as DPPLs, of which two members are currently known DPPX (or DPP6) and DPP10. It is now believed that ISA channels in neurons are ternary complexes that include principal or pore-forming subunits of the Kv4 family and two types of associated proteins KChIPs and DPPLs. This application is focused in CA1 hippocampal pyramidal cells, neurons that are important in spatial learning and in the pathogenesis of epilepsy, and prominently express one Kv4 protein Kv4.2 and one DPPL, DPPX. The goal of the proposal is to test the hypothesis that DPPX is an important component of Kv4 channels in CA1 neurons, determining the proper distribution, biophysical properties and dynamic modulation of the channels. Aim 1 will utilize highly specific antibodies raised during the last funding period to investigate the localization of DPPX in CA1 neuron dendrites and its relationship to the other Kv4 channel components. Aim 2 will utilize DPPX knockout mice also developed during the last funding period to investigate the effects of DPPX ablation on the distribution and function of Kv4 channels in CA1 neurons. Aim 3 explores aspects of DPPX actions on Kv4 channels that have thus far received little attention: the effects of this auxiliary subunit on channel modulation by protein kinases and in controlling channel trafficking and expression in the plasma membrane, to test the hypothesis that DPPX regulates the stability of Kv4 channels at the plasma membrane. Mutations in the gene encoding DPPX have been associated with autism, underscoring the importance of understanding the function of these proteins.