Alpha-Conotoxin MII: A Selective Nicotinic Receptor Probe

描述(申请人提供)：尼古丁通过烟碱型乙酰胆碱受体(NAChRs)家族产生行为效应。尼古丁诱发的多巴胺释放被认为在建立和维持尼古丁依赖方面发挥了重要作用，这种依赖阻碍了人们继续使用烟草产品，尽管它们对健康的危害是众所周知的。甲芋螺毒素MII是从掠食性圆锥蜗牛中分离出来的一种毒素，它区分尼古丁受体的亚群。在这笔赠款的第一个资助期，我们使用α-CtxMII来识别和分析调节尼古丁引起的多巴胺释放的nAChR群体。我们还开始研究长期接触尼古丁对这些受体的影响，以及它们在帕金森病模型中是如何受到影响的。为了增强α-CtxMII的实用性，我们还设计了一些变体，这些变体具有新的性质或增加了它对特定nAChR群体的选择性。目前提案中概述的实验将进一步扩展这些研究。1)慢性治疗和尼古丁亚基突变将被用来(单独和联合)研究前一个资助期中描述的nAChR种群如何相互作用，以及与它们调节的神经递质系统之间的相互作用。2)新的α-CtxMII衍生物的开发有两个目标。首先，制备α3β2-nAChR亚型选择性衍生物(目前我们还没有这样的化合物，但这是一个自然表达的nAChR亚型，需要进一步研究)。第二，生产基于α-CtxMII的放射性标记，该标记保留了[1251]α-CtxMII的原始选择性(这是在以前的资助时期开发的)，但具有改进的分析性能。这将提高我们测量和研究这些重要的nAChRs的能力。3)对α-7亚型nAChRs具有选择性的α-芋螺毒素Arib衍生物的合成和表征。我们打算开发一系列有用的、高度选择性的工具来研究这种自然产生的nAChR亚型。拟议的研究将进一步深入了解自然产生的nAChRs的位置、数量和功能作用，以及它们之间的相互作用。很可能，这种理解的增加将反过来阐明哪些nAChR亚型与尼古丁依赖有关，从而有助于开发更有效的戒烟辅助手段。这些洞察力也可能指导其他疾病的尼古丁疗法的设计。

DESCRIPTION (provided by applicant): Nicotine produces behavioral effects through a diverse family of nicotinic acetylcholine receptors (nAChRs). Nicotine-evoked dopamine release is thought to play an important role in the establishment and maintenance of nicotine dependence, which undelies peoples' continued use of tobacoo products, despite their well-known dangers to health. alpha-conotoxin MII is a toxin isolated from the predatory cone-snail Conus magus, which distinguishes between subsets of nicotinic receptors. In the first funding periods of this grant, we used alpha-CtxMII to identify and analyse the nAChR populations that modulate nicotine-evoke dopamine release. We also began to study the effects of chronic nicotine exposure on these receptors, and how they are affected in models of Parkinson's Disease. In order to enhance the usefulness of alpha-CtxMII, we have also engineered variants which have incorporate new properties or increased its selectivity for particular nAChR populations. Experiments outlined in the current proposal will extend these studies further. 1) Chronic treatment and nicotinic subunit mutation will be used (alone, and in combination) to investigate how the nAChR populations characterized in the previous funding period interact with each other, and with the neurotransmitter systems that they modulate. 2) New alpha-CtxMII derivatives will be developed with two aims. First, to make alpha3beta2-nAChR subtype selective derivatives (we do not have such a compound at present, but this is a natually-expressed nAChR subtype that requires further study). Second, to produce alpha-CtxMII-based radiolabels that retain the original selectivity of [125l]alpha-CtxMII (which was developed in the previous funding periods), but with improved assay performance. This will improve out ability to measure and study these important nAChRs. 3) Synthesize and characterize derivatives of alpha-conotoxin ArIB, which has selectivity for alpha7-subtype nAChRs. We intend to develop a series of useful, highly-selective tools for the study of this naturally-occurring nAChR subtype. The proposed studies will provide further insights into the locations, numbers and functional roles of naturally-occurring nAChRs, and the interactions between them. It is likely that this increased understanding will, in turn, illuminate which nAChR subtypes are implicated in nicotine dependence, and thus assist in attempts to develop more-effective smoking cessation aids. These insights may also guide the design of nicotinic therapies for other conditions.