Targeting alpha7 nAChR for Therapeutic Effects

靶向 α7 nAChR 以获得治疗效果

• 批准号: 6984700
• 负责人: ROGER L PAPKE
• 金额: $ 32.47万
• 依托单位: UNIVERSITY OF FLORIDA
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-05-01 至 2009-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6984700
• 关键词: Xenopus; Xenopus oocyte; binding sites; chemical models; drug discovery /isolation; inhibitor /antagonist; neuropharmacology; nicotine; nicotinic receptors; receptor binding; receptor expression; receptor sensitivity; stimulant /agonist; tropanes

DESCRIPTION (provided by applicant): The a7 neuronal nicotinic acetylcholine receptor is an important therapeutic target, relevant to Alzheimer's Disease, stroke, and schizophrenia. Understanding how this receptor responds to natural and experimental agonists is crucial for the therapeutic targeting of a7. We have shown that stimulation of a7 receptors by relatively low agonist concentrations can support an equilibration between activation and desensitization, resulting in a functional modality that we hypothesize to be the basis for therapeutic effects. In this continuation we will study how a7-selective agonists both activate this receptor and, in some cases, produce down-regulation of function through secondary inhibitory or desensitizing effects. Our experiments utilize structurally diverse a7-selective agonists including large molecules such as benzylidene anabaseines (BA) and indole tropanes (IT) and smaller probes for receptor selectivity such as choline and tropane. Our data suggest that BA compounds with residual inhibitory effects interact with hydrophobic residues on the margins of the ACh binding site. We will test that hypothesis through the use of site-directed mutants and new experimental agonists. We will develop novel compounds including additional indole-tropanes (IT) to evaluate as agonists and use as experimental probes. The prototype for the IT compounds is tropisetron, a 5HT3 receptor antagonist and a7-selective agonist. Our preliminary studies show that while the indole moiety in tropisetron has activity with 5HT3 receptors, the tropane group is, on its own, an a7 agonist. Indole conjugation appears to make tropisetron a more potent, though less efficacious, agonist for a7 than the small agonist tropinone. We hypothesize that, based either on intramolecular effects or specific interactions between the drug and amino acids in or near the agonist binding site, substitutions of the indole will modify the properties of IT agonists in ways that will be predictable based on our previous studies of BA compounds and models of the receptor binding site. The structurally diverse BA and IT agonists are much larger molecules than the endogenous agonists, ACh and choline, and are likely to have binding sites that include more points of contact on the receptor than the binding site of ACh. We will conduct scanning cysteine accessibility experiments to identify the binding sites for large and small molecular probes, utilizing both selective and nonselective agonists as well as competitive antagonists. We will define both the ligand and protein basis through which certain drugs achieve selectivity for a7 receptors. Taken together, our studies will define effective ways to activate a7 receptors with potentially therapeutic agents and will also provide insights into how new agents may be designed to selectively activate this receptor with minimized inhibitory side-effects due to receptor desensitization or the non-selective activation of other receptor subtypes.

描述（由申请人提供）：A7神经元烟碱乙酰胆碱受体是重要的治疗靶点，与阿尔茨海默氏病，中风和精神分裂症有关。了解该受体对自然和实验激动剂的反应对于A7的治疗靶向至关重要。我们已经表明，通过相对较低的激动剂浓度对A7受体的刺激可以支持激活和脱敏之间的平衡，从而导致了我们假设的功能模态，这是治疗效应的基础。在这种延续中，我们将研究A7选择性激动剂如何激活该受体，在某些情况下，通过继发性抑制或脱敏作用来下调功能。我们的实验利用结构上多样的A7选择性激动剂，包括大分子，例如苄基二氮，BA）和吲哚tropanes（IT）（IT）以及较小的受体选择性探针，例如胆碱和tropane。我们的数据表明，具有残留抑制作用的BA化合物与ACH结合位点边缘的疏水残基相互作用。我们将通过使用定位突变体和新的实验激动剂来检验该假设。我们将开发新的化合物，包括额外的吲哚 - 肌化（IT），以评估为激动剂并用作实验探针。 IT化合物的原型是Tropisetron，一种5HT3受体拮抗剂和A7选择性激动剂。我们的初步研究表明，虽然热带酮中的吲哚部分具有5HT3受体的活性，但Tropane组本身是A7激动剂。吲哚结合似乎使Tropisetron比小型激动剂肌酮更有效，尽管有效，但对A7的激动剂。我们假设，基于分子内效应或激动剂结合位点或附近药物与氨基酸之间的特定相互作用，吲哚的取代将根据我们先前对受体结合位点的BA化合物和模型的研究来修改IT激动剂的性质。与内源性激动剂（ACH和胆碱）相比，结构上不同的Ba和IT激动剂的分子要大得多，并且可能具有与ACH的结合位点包含更多接触点的结合位点。我们将进行扫描半胱氨酸可及性实验，以识别大小分子探针的结合位点，利用选择性和非选择性激动剂以及竞争性拮抗剂。我们将定义某些药物对A7受体的选择性的配体和蛋白质基础。综上所述，我们的研究将定义有效的方法来激活具有潜在治疗剂的A7受体，还将提供有关如何设计新药物以选择性地激活该受体的抑制性副作用或由于受体脱敏或其他受体子类型的非选择性激活而产生的。