GENETIC ANALYSIS OF NICOTINE ADAPTATION IN C ELEGANS

烟草的使用与多种人类疾病有关，包括心脏病、肺气肿和癌症，这些疾病加在一起每年导致数百万人过早死亡。尼古丁的成瘾特性是持续和强制使用烟草的主要原因。尼古丁成瘾被认为是由于大脑中烟碱型乙酰胆碱受体活性和表达的长期适应性变化造成的。然而，这些适应过程背后的分子和神经机制仍然知之甚少。这项研究的目的是在一个简单的动物模型-线虫秀丽线虫中进行遗传分析，以探索尼古丁适应的分子基础。线虫非常适合神经系统功能的分子分析：它有一个简单且具有良好特性的神经系统，其世代时间短，基因组小且大量测序，以及可进行种系转化，使其成为经典和分子遗传学研究的理想选择。线虫对尼古丁的反应显著且易于测量，长期接触尼古丁会导致对尼古丁的耐受和依赖，其行为由神经肌肉和神经元尼古丁受体共同控制。在这个项目中，线虫中尼古丁适应所需的基因将通过筛选适应缺陷突变来识别。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。蛋白激酶C缺陷突变体的研究表明，烟碱受体亚单位的PKC磷酸化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检验。这项工作的最终目标是为神经元中尼古丁适应的一般分子机制提供一个模型，并识别参与其他动物(包括脊椎动物)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.