Yuan Li-Lian, Chen Xixi
Department of Neuroscience, University of Minnesota, Minneapolis, 55455, USA.
Prog Neurobiol. 2006 Apr;78(6):374-89. doi: 10.1016/j.pneurobio.2006.03.003. Epub 2006 May 22.
Complex computations in the nervous system begin with electrical signals generated in single neurons. Such signals include action potentials mediated by the opening of voltage-dependent ion channels, and synaptic potentials arising from neurotransmitter receptor activation. The amplitude, waveform, and propagation of action potentials and synaptic potentials influence cellular signaling in profound ways, and are largely determined by activities of ion channels in the cell membrane. The location and properties of ion channels therefore play critical roles in shaping electrical signaling in the neuron, which is the foundation for more complex computations at network levels. This review summarizes what we know about the great diversity of K(+) channels found in neuronal dendrites, the subcellular compartment where synaptic signals integrate and where various forms of plasticity occur. Specifically, we discuss the molecular identity, the distribution, kinase modulation, biophysical properties, and functional roles of a variety of K(+) channels including voltage-gated, calcium-activated, and ligand-gated/G-protein coupled K(+) channels. One emerging theme from recent literature is the recognition that K(+) channels are powerful regulators of the function of dendrites. A second theme indicates that this K(+) channel regulation depends on their unique subcellular distribution. In particular, the mechanisms underlying the establishment and maintenance of non-uniform distributions of ion channels are beginning to be understood in greater detail. An especially intriguing aspect of above mechanisms is that they are achieved through protein kinase phosphorylation and may thus be activity-dependent. In parts of this review, we choose to focus on CA1 pyramidal neurons of the rodent hippocampus and the K(+) channels in their dendrites. Being one of the best-characterized cell types in the nervous system, the CA1 pyramidal neuron has long been studied as a prototypic neuron from which general rules of neuronal computation and synaptic plasticity emerge. A great deal of what we know about dendritic K(+) channels comes from studies on CA1 pyramidal neurons. Where available, we also include up-to-date findings on dendritic K(+) channels in other cell types.
神经系统中的复杂计算始于单个神经元产生的电信号。此类信号包括由电压依赖性离子通道开放介导的动作电位，以及神经递质受体激活产生的突触电位。动作电位和突触电位的幅度、波形及传播以深刻的方式影响细胞信号传导，并且在很大程度上由细胞膜中离子通道的活动所决定。因此，离子通道的位置和特性在塑造神经元电信号方面起着关键作用，而神经元电信号是网络层面更复杂计算的基础。本综述总结了我们对神经元树突中发现的大量不同种类钾离子通道的了解，树突是突触信号整合以及发生各种形式可塑性的亚细胞区室。具体而言，我们讨论了包括电压门控、钙激活和配体门控/ G蛋白偶联钾离子通道在内的多种钾离子通道的分子身份、分布、激酶调节、生物物理特性及功能作用。近期文献中一个新出现的主题是认识到钾离子通道是树突功能的强大调节因子。第二个主题表明这种钾离子通道调节取决于它们独特的亚细胞分布。特别是，离子通道非均匀分布的建立和维持所依据的机制正开始得到更详细的了解。上述机制一个特别引人关注的方面是它们通过蛋白激酶磷酸化实现，因此可能依赖于活动。在本综述的部分内容中，我们选择聚焦于啮齿动物海马体的CA1锥体神经元及其树突中的钾离子通道。作为神经系统中特征最明确的细胞类型之一，CA1锥体神经元长期以来一直被作为一种原型神经元进行研究，从中可得出神经元计算和突触可塑性的一般规律。我们对树突钾离子通道的许多了解都来自对CA1锥体神经元的研究。在有可用信息的情况下，我们还纳入了其他细胞类型中树突钾离子通道的最新研究结果。
