Chemoreception in Paramecium

从刺激中捕获能量并启动一个 神经系统中的反应信号称为感觉信号 转导 在化学感觉通路中，包括味觉和 气味，化学刺激分子通常通过结合 感受器膜上的高度特异性受体位点 cell. 这种绑定以某种方式耦合到一个特性 细胞膜的变化引发电信号。 它 在许多情况下，转导过程可能涉及 内部信使分子或离子，如环 核苷酸、钙或脂质代谢物。 微观 水生单细胞生物草履虫显示简单 化学感受行为，有许多有趣的突变株， 它的细胞膜有几个类似于兴奋的性质， 神经细胞这是一个非常成功的模式系统， 阐明了化学感受接受的某些方面。 该项目将探讨结构，功能， 草履虫的化学感受器位点的分布，以及它们如何 与传导过程中的内部钙水平相互作用 过程 其中一个重要的刺激分子是环状的 核苷酸化合物，cAMP，与众所周知的ATP密切相关 具有重要的代谢功能。 分子遗传学将是 用于克隆和测序膜蛋白的基因 作为cAMP的结合受体位点。 一旦基因 序列预测，抗体较短的肽序列 在该基因内将被用来探测受体结构， 分布，并预测的功能域的 受体分子 将使用染料测量钙水平， 正常和突变菌株将用于表征 由ATP驱动的“分子泵”的性质， 钙 从这个新的模型系统的发现将有相当大的 对化学感受工作的影响，因为很少有化学感受 受体的特征还没有得到描述， 已经出现了。 结果，沿着那些对钙 泵，可能对神经科学家也很重要， 一般来说，由于许多机制可能类似于那些 在神经元之间的功能性突触接触中发现。

The capture of energy from a stimulus and the initiation of a response signal in the nervous system is termed sensory transduction. In the chemosensory pathways, including taste and smell, chemical stimulant molecules often act by binding to highly specific receptor sites on the membrane of the sensory cell. This binding is in some way coupled to a characteristic change in the membrane that initiates an electrical signal. It is likely that in many cases the transduction process involves internal messenger molecules or ions, such as cyclic nucleotides,calcium, or lipid metabolites. The microscopic aquatic single-celled organism Paramecium shows simple chemosensory behavior, has many interesting mutant strains, and its cell membrane has several properties similar to excitable nerve cells. It has been a very successful model system for clarifying some aspects of chemosensory reception. This project will explore the structure, function, and distribution of chemoreceptor sites in Paramecium, and how they interact with levels of internal calcium in the transduction process. One of the important stimulus molecules is a cyclic nucleotide compound, cAMP, closely related to the well-known ATP that has vital metabolic functions. Molecular genetics will be used to clone and sequence the gene for the membrane protein thatacts as the binding receptor site for cAMP. Once the gene sequence is predicted, antibodies to shorter peptide sequences within that gene will be made to probe receptor structure and distribution, and to predict the functional domains of the receptor molecule. Calcium levels will be measured using dyes, and normal and mutant strains will be used to characterize the nature of the "molecular pump" driven by ATP that extrudes calcium. Findings from this novel model system will have considerable impact on chemosensory work, because very few chemosensory receptors have yet been characterized, and no common patterns have emerged yet. The results, along with those on the calcium pump, are likely to be important also to neuroscientists in general, since many of the mechanisms may be similar to those found in the functioning synaptic contacts between neurons.