Evolution of Potassium Channels and Nerve Networks in Cnidaria

刺胞动物钾通道和神经网络的进化

• 批准号: RGPIN-2015-04421
• 负责人: Gallin, Warren
• 金额: $ 1.75万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=612959
• 关键词: Evolution; Potassium; Channels; Nerve; Networks

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.

所有动物都有神经系统——由可兴奋细胞组成的组织，在身体不同部位之间传输和整合信息。不同生物体的神经系统结构和活动差异很大，从相对分散的刺胞动物的神经网络到两侧对称动物的许多解剖学上不同的集中神经系统。然而，所有动物神经系统的所有细胞都具有电响应性。离子通道蛋白，两种配体门控蛋白，对突触处的神经递质和突触外调节信号作出反应，以及电压门控蛋白，对膜电位的变化作出反应，调节膜电位。该提案描述了一项旨在识别和表征刺胞动物 Polyorchis penicillatus 中电压门控钾通道的计划。 进化的自然过程产生了大量序列不同但具有一个共同特性的同源物——所有变体在它们产生的生物体的背景下都具有功能。我们建议从 P. penicillatus 中分离出总共 15 个电压门控钾通道 cDNA（除了迄今为止已分离出的 6 个）。当通道被克隆和测序后，我们将使用电压钳技术在非洲爪蟾的卵母细胞中单独表达它们，以确定它们的电生理特性，并将它们的序列和活性与来自其他生物体的已知通道进行比较。这些比较将使我们能够制定有关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学表征的组合来测试该假设。与此同时，我们将为每个通道制备抗体，并绘制它们在水母成体水母中的位置，作为了解刺胞动物神经网络与其他生物体神经系统之间的异同的第一步。 P. penicillatus 是这些研究的一个不错的选择。成体是一种自由生活的水母，与其他刺胞动物模式生物、无柄水螅水螅和无柄海葵不同。因此，它的神经系统已经进化到有利于活动而不是固着的生活方式。它足够大，以至于对其神经系统不同组成部分的电生理学研究已被证明是简单的。我们对 P. penicillatus 的神经网络的解剖结构有透彻的了解。六种不同的电压门控钾通道已被分离并进行电生理学表征。这些调查的结果证明了我们对该计划采取的总体方法的可行性、力量和有效性。