Evolution of Potassium Channels and Nerve Networks in Cnidaria

所有的动物都有神经系统——由可兴奋的细胞组成的组织，在身体的不同部位之间传递和整合信息。神经系统的结构和活动在不同生物之间差别很大，从刺胞动物相对分散的神经网络到两侧动物许多解剖学上不同的集中神经系统。然而，所有动物的神经系统的所有细胞都有电反应。离子通道蛋白对突触和突触外的神经递质调节信号作出反应的配体门控蛋白和对膜电位变化作出反应的电压门控蛋白调节膜电位。本提案描述了一个旨在识别和表征刺胞动物polyyorchis penicillatus中电压门控钾通道的程序。进化的自然过程产生了大量的同源物，它们的序列不同，但有一个共同的特性——所有的变体在它们产生的生物体中都是有功能的。我们计划从青霉霉中分离出15个电压门控钾通道cdna（除了迄今已分离的6个）。当通道被克隆和测序后，我们将在非洲爪蟾卵母细胞中单独表达它们，使用电压箝位技术来确定它们的电生理特性，并将它们的序列和活性与其他生物的已知通道进行比较。这些比较将使我们能够制定关于蛋白质序列和通道活性之间关系的假设，我们将使用合成诱变和电生理表征的组合进行测试。与此同时，我们将准备针对这些通道的抗体，并绘制它们在水母成年水母体内的位置，作为了解刺胞神经网络与其他生物神经系统之间异同的第一步。青霉是这些研究的一个很好的选择。成虫是一种自由生活的水母，不像其他刺胞动物模式生物，水螅（一种无根的水螅）和线虫（一种无根的海葵）。因此，它的神经系统已经进化到有利于运动而不是静止的生活方式。它足够大，对其神经系统不同组成部分的电生理学研究已经证明是直截了当的。我们对青霉菌神经网络的解剖有透彻的了解。六种不同的电压门控钾通道已经被分离出来并进行了电生理表征。这些调查的结果证明了我们对这个项目所采取的整体方法的可行性、有效性和有效性

All animals have nervous systems - tissues formed of excitable cells that transmit and integrate information between different parts of the body. The structure and activity of nervous systems varies widely between organisms, from the relatively dispersed neural networks of the Cnidaria to the many anatomically different centralized nervous systems of the Bilateria. However, all cells of the nervous systems of all animals are electrically responsive. Ion channel proteins, both ligand-gated, which respond to neurotransmitters at the synapse and extra-synaptic modulatory signals, and voltage-gated, which respond to changes in membrane potential, modulate the membrane potential. This proposal describes a program aimed at identifying and characterizing the voltage-gated potassium channels in the cnidarian, Polyorchis penicillatus.***The natural process of evolution gives rise to a large number of homologs that differ in sequence but that have one common property - all the variants are functional in the context of the organisms in which they arise. We propose to isolate a total of 15 voltage-gated potassium channel cDNAs from P. penicillatus (in addition to the 6 that have been isolated to date). When the channels are cloned and sequenced we will express them individually in oocytes of Xenopus laevis to determine their electrophysiological properties, using the voltage clamp technique, and compare their sequences and activities to known channels from other organisms. These comparisons will allow us to formulate hypotheses about the relationship between the protein sequences and the activity of the channels, which we will test using a combination of synthetic mutagenesis and electrophysiological characterization. In parallel, we will prepare antibodies to each of these channels and map their locations in the adult medusa of the jellyfish, as a first step towards understanding the similarities and differences between the cnidarian nerve net and nervous systems from other organisms.***P. penicillatus has been a good choice for these studies. The adult form is a free-living medusa, unlike the other cnidarian model organisms, Hydra magnipapillata, a sessile polyp, and Nematostella vectensis, a sessile anemone. Thus, its nervous system has evolved to facilitate a motile rather than sessile life-style. It is large enough that electrophysiological studies on different components of its nervous system have proven straightforward. We have a thorough knowledge of the anatomy of the neural network in P. penicillatus. Six different voltage-gated potassium channels have already been isolated and electrophysiologically characterized. The results from those investigations have demonstrated the feasibility, power and validity of the overall approach that we are taking to this program.**