MOLECULAR CHARACTERIZATION OF GLUTAMATE RECEPTORS IN FRESHWATER SNAILS

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 谷氨酸是脊椎动物和无脊椎动物系统中共同的神经递质，它主要参与兴奋性神经传递。在无脊椎动物中，谷氨酸通过受体来调节行为，而受体的特性不如脊椎动物。例如，已知谷氨酸通过介导兴奋或抑制的受体来控制肺类软体动物(如池塘蜗牛Lymneea和Helisoma)的取食行为，但负责的受体只有部分特征。在从Lymneea克隆的两个兴奋性受体亚基中，只有一个亚基具有生理特性。由于谷氨酸兴奋海鞘瘤中控制摄食某一阶段的运动神经元，很可能存在一个或多个类似的受体(S)。这些受体的药理学表明与淋巴受体同源，而淋巴受体与大鼠大脑受体同源。这项研究的目的是克隆和测序兴奋性谷氨酸受体，假设存在于三卷螺旋虫和一个密切相关的物种光滑生物的口腔神经节中，因为它是曼氏血吸虫的中间宿主，具有重要的医学意义。在拨款的头两年，使用简并引物聚合酶链式反应获得了代表两个Helisoma兴奋性谷氨酸受体跨膜区的短重叠DNA序列。使用RACE PCR将这些序列延伸到3端，并在此过程中延伸到5端。从AMPA受体引物获得的序列与Lym-eGluR1受体具有显著的序列同源性。用AMPA和KA受体引物获得的序列与海兰GluR7同源。我们计划利用今年最后4个月的资金完成这两个克隆，并从Biomphalaria获得谷氨酸受体序列。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Glutamate is a common neurotransmitter in both vertebrates, where it is involved primarily in excitatory neurotransmission, and invertebrate systems. In invertebrates, glutamate mediates behaviors through receptors that are less well characterized than vertebrate ones. For example, glutamate is known to control the feeding behavior in pulmonate mollusks such as the pond snails Lymnaea and Helisoma through receptors that mediate either excitation or inhibition, but the receptors responsible have only been partially characterized. Only one of two excitatory receptor subunits cloned from Lymnaea have been characterized physiologically. Since glutamate excites motor neurons controlling one phase of feeding in Helisoma, one or more similar receptor(s) is likely to be present. The pharmacology of these receptors suggests homology with the Lymnaea receptors, which have homology with rat brain receptors. The goal of this research is to clone and sequence excitatory glutamate receptors hypothesized to be present in the buccal ganglia of both Helisoma trivolvis, and a closely related species, Biomphalaria glabrata, chosen because of its medical importance as the intermediate host of Schistosoma mansoni. In the first two years of the grant, degenerate primer PCR was used to obtain short overlapping DNA sequences representing the transmembrane regions of two Helisoma excitatory glutamate receptors. RACE PCR was used to extend these sequences to the 3 end, and part of the way to the 5 end. Sequences obtained from AMPA receptor primers have significant sequence identity to the Lym-eGluR1 receptors. Sequences obtained with both AMPA and KA receptor primers are homologous to Aplysia GluR7. We plan to use the last 4 months of funding this year to finish these two clones and to obtain glutamate receptor sequences from Biomphalaria.