Evolution of Potassium Channels and Nerve Networks in Cnidaria

所有动物都有神经系统--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的生物体之间差异很大，从蛇床纲的相对分散的神经网络到比拉特里亚的许多在解剖上不同的集中式神经系统。然而，所有动物神经系统的所有细胞都有电反应。离子通道蛋白，既有配体门控的，它对突触和突触外的神经递质调制信号做出反应，也有电压门控的，它对膜电位的变化做出反应，调节膜电位。这项建议描述了一个程序，旨在识别和特征电压门控钾通道在线虫，多睾吸虫。 进化的自然过程产生了大量的同源基因，它们的序列不同，但有一个共同的性质--所有的变体在产生它们的有机体的背景下都是功能的。我们建议从青霉中分离总共15个电压门控钾通道cDNA(除了迄今已分离到的6个)。当这些通道被克隆和测序后，我们将在非洲爪哇的卵母细胞中单独表达它们，利用电压钳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中已知的通道进行比较。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，我们将使用合成突变和电生理特征相结合的方法进行测试。同时，我们将制备针对每个通道的抗体，并绘制它们在水母成体水母中的位置，作为了解蛇行神经网和其他生物神经系统之间的异同的第一步。 青霉是进行这些研究的一个很好的选择。成体水母是一种自由生活的水母，不同于其他北极熊模式生物，木乃氏水母是一种无柄水母，而线虫是一种无柄海葵。因此，它的神经系统进化成了一种活动的而不是固执的生活方式。它的规模足够大，以至于对其神经系统不同组成部分的电生理研究已经被证明是直截了当的。我们对青霉神经网络的解剖学有透彻的了解。目前已分离出六种不同的电压门控钾通道，并对其进行了电生理特性研究。这些调查的结果证明了我们对这一计划采取的总体方法的可行性、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.