Regulation of Alpha 7 Nicotinic Receptor Assembly in Human Smokers

描述（由申请人提供）：尼古丁是最常见和最具破坏性的滥用药物之一。尽管在过去的20年里，吸烟在这个国家有所减少，但精神病患者的吸烟率并没有减少，特别是精神分裂症患者，其中80%以上的患者吸烟。尼古丁受体是与药物接触的第一个点，使该受体家族的调节成为研究的重要第一目标。α 7烟碱受体（α 7 *）与烟草使用以及精神疾病精神分裂症的认知和感觉处理缺陷有关。这种受体的基因CHRNA 7被选为治疗这种疾病认知缺陷的药物开发中最有前途的靶点。α 7 * 受体的表面表达在精神分裂症患者的死后脑中是低的，但是我们已经发现精神分裂症吸烟者的受体的mRNA和蛋白质的水平是足够的。这表明在精神分裂症患者中受体的组装和运输可能是异常的。该提议将研究低水平α 7 * 表面受体的两种机制：1）显性负剪接变体的表达，和2）RIC 3的表达，RIC 3是与α 7 * 组装相关的蛋白质。我们的数据表明，外显子9/内含子9中的两个多态性可能与缺失外显子9的剪接变体的存在有关。这些变体处于连锁不平衡，代表单个突变等位基因。这些多态性与精神分裂症和精神分裂症患者吸烟相关。缺失外显子9的剪接变体导致读码框改变和提前终止。在卵母细胞模型中，较短的肽在与全长亚基的组装中充当显性阴性。我们的假设是外显子9/内含子9突变影响RNA剪接和缺失外显子9的剪接变体的表达，其阻断了感受态受体的组装和表面结合。另一种假设涉及RIC 3（一种促进组装的蛋白质）的异常表达。这项工作的完成将确定是否假设的机制是在精神分裂症患者死后大脑中看到的低水平的结合操作。烟草制品是最常见和最具破坏性的滥用药物之一，被大量用于精神病患者。潜在的低水平的表面受体可能有助于这些患者吸烟的生物需求。这项提案将研究细胞表面表达的烟碱受体的机制，响应烟草中的尼古丁。

DESCRIPTION (provided by applicant): Nicotine is one of the most common and devastating drugs of abuse. Although smoking has declined in this country over the last twenty years, it has not decreased in the mentally ill, particularly in schizophrenia where more than 80% of these patients smoke. Nicotinic receptors are the first point of contact with the drug, making regulation of this receptor family an important first target for study. The a7 nicotinic receptor (a7*) has been implicated in tobacco use and deficits in cognition and sensory processing in the mental illness schizophrenia. The gene for this receptor, CHRNA7, was selected as the most promising target in drug development for cognitive deficits in this disease. Surface expression of the a7* receptor is low in postmortem brain of schizophrenic patients, but we have found adequate levels of both mRNA and protein for the receptor in schizophrenic smokers. This suggests that the assembly and trafficking of the receptor may be aberrant in schizophrenics. This proposal will investigate two mechanisms for the low levels of a7* surface receptors: 1) expression of a dominant negative splice variant, and 2) expression of RIC3, a protein associated with a7* assembly. Our data indicate that two polymorphisms in exon9/intron 9 may be associated with the presence of a splice variant missing exon 9. The variants are in linkage disequilibrium, representing a single mutant allele. The polymorphisms are associated with both schizophrenia and smoking in schizophrenia. The splice variant, missing exon 9, results in a frame change and premature termination. The shorter peptide acts as a dominant negative in assembly with the full-length subunit in an oocyte model. Our hypothesis is that the exon9/intron9 mutation affects RNA splicing and expression of the splice variant missing exon9, which blocks assembly of a competent receptor and surface binding. An alternative hypothesis involves aberrant expression of RIC3, a protein that facilitates assembly. The completion of this work will determine whether the hypothesized mechanisms are operative in the low levels of binding seen in postmortem brain of schizophrenic subjects. Lay statement: Tobacco products are one of the most common and devastating drugs of abuse, and are heavily used in the mentally ill. Underlying low levels of surface receptors may contribute to a biological need for these patients to smoke. This proposal will study mechanisms for cell surface expression of a nicotinic receptor that responds to the nicotine in tobacco.