GENETIC ANALYSIS OF NICOTINE ADAPTATION IN C ELEGANS

烟草使用与一系列人类疾病有关，包括心脏病、肺气肿和癌症，这些疾病每年共同导致数百万人过早死亡。尼古丁的成瘾性是持续和强迫性吸烟的主要原因。尼古丁成瘾被认为是由于大脑中尼古丁乙酰胆碱受体活性和表达的长期适应性变化。然而，这些适应过程背后的分子和神经元机制仍然知之甚少。本研究的目的是利用简单动物模型秀丽隐杆线虫的遗传分析来研究尼古丁适应的分子基础。秀丽隐杆线虫非常适合于神经系统功能的分子分析：它有一个简单且特征明确的神经系统，其产生时间短，基因组小且大部分测序，以及可获得的种系转化使其成为经典和分子遗传学研究的理想选择。秀丽隐杆线虫对尼古丁表现出显著且容易测量的反应，长期尼古丁暴露导致尼古丁耐受和依赖，这与神经肌肉和神经元尼古丁受体控制的行为有关。在这个项目中，线虫尼古丁适应所需的基因将通过筛选适应缺陷突变体来鉴定。在早期筛选中发现的两个尼古丁适应基因将被克隆，以确定它们的分子功能，并表征它们发挥作用的细胞途径。对蛋白激酶c缺陷突变体的研究表明，PKC磷酸化尼古丁受体亚基是尼古丁适应的一种机制，这一可能性将通过对表达突变受体的转基因蠕虫的分析来验证。这项工作的最终目标是为神经元尼古丁适应的一般分子机制提供一个模型，并在包括脊椎动物在内的其他动物中发现参与尼古丁成瘾的新蛋白质。

Tobacco use has been implicated in a wide range of human diseases, including heart disease, emphysema, and cancer, which together result in millions of premature deaths each year. The addictive properties of nicotine are a major cause of persistent and compulsive tobacco use. Nicotine addiction is thought to result from long-term adaptive changes in the activity and expression of nicotinic acetylcholine receptors in the brain. However, the molecular and neuronal mechanisms that underlie these adaptive processes remain poorly understood. The goal of this research is to use genetic analysis in a simple animal model, the nematode Caenorhabditis elegans, to investigate the molecular basis of nicotine adaptation. C. elegans is highly amenable to molecular analysis of nervous system function: it has a simple and well characterized nervous system, and its short generation time, small and largely sequenced genome, and accessibility to germline transformation make it ideal for classical and molecular genetic studies. C. elegans exhibits a striking and easily measurable response to nicotine, and long- term nicotine exposure leads to nicotine tolerance and dependence with respect to behaviors controlled by both neuromuscular and neuronal nicotinic receptors. In this project, genes required for nicotine adaptation in nematodes will be identified by screening for adaptation-defective mutants. Two nicotine adaptation genes identified in earlier screens will be cloned to determine their molecular functions, and to characterize the cellular pathways in which they function. The possibility, suggested by studies of protein kinase C-defective mutants, that PKC phosphorylation of nicotinic receptor subunits is a mechanism for nicotine adaptation will be tested through the analysis of transgenic worms expressing mutant receptors. The ultimate goal of this work is to provide a model for the general molecular mechanisms underlying nicotine adaptation in neurons, and to identify new proteins that participate in nicotine addiction in other animals, including vertebrates.