BASIC FOR NA+ MODULATION OF ALPHA2-RECEPTOR FUNCTION

ALPHA2 受体功能 NA 调节的基础

• 批准号: 3337987
• 负责人: LEE E LIMBIRD
• 金额: $ 21.94万
• 依托单位: VANDERBILT UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1979
• 资助国家: 美国
• 起止时间: 1979-12-01 至 1990-12-23
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3337987
• 关键词: Anura; G protein; adenylate cyclase; adrenergic agents; alpha adrenergic receptor; antiport; beta adrenergic receptor; catecholamines; cholinergic agents; chromatography; crosslink; enzyme complex; enzyme induction /repression; erythropoiesis; guanine nucleotides; heart function; heart pharmacology; hormone receptor; laboratory rat; myocardium; radiotracer; sodium; stoichiometry; tritium

The long-term goal of this proposal is to understand the molecular basis for physiological effects elicited by epinephrine via alpha-adrenergic receptors of the pharmacological alpha-2-subtype. We will address this long-term goal by focusing on the manner in which sodium ion (Na+) influences alpha-2-receptor-agonist interactions and alpha-2-receptor-induced function. The specific aims of the present proposal are to 1) purify the alpha-2-receptor to homogeneity, 2) evaluate whether the effects of Na+ on the purified alpha-2-receptor are conveyed via the betagamma heterodimer of the GTP-binding protein heterotrimer (Gi: alphabetagamma) which modulates alpha-2-receptor functions or, alternatively, via a Na+/H+ antiporter, 3) reconstitute the alpha-2-adrenergic receptor with the putative Na+-effector component in lipid vesicle preparations to test the conclusions drawn in #2 and 4) utilize permeabilized platelets to determine whether Gi represents the interface between the alpha-2-receptor and the Na+/H+ exchange mechanism and/or phospholipase A-2 activity postulated to be involved in epinephrine-provoked platelet secretion. Alpha-2-receptors are one of a number of hormone and neurotransmitter receptor populations which are linked to inhibition of adenylate cyclase activity. A number of lines of evidence suggest that the resultant decreases in cAMP levels are not sufficient to "signal" a physiological effect, but that other important biochemical changes must also be evoked by these receptor populations. Receptors which can inhibit cAMP accumulation are all known to be modulated by Na+. Our studies, which focus on the basis for this role of Na+, should provide fundamental new insights into how alpha-2-adrenergic receptors elicit their physiological effects, in particular, and what are the alternate signaling mechanisms utilized by receptors linked to inhibition of adenylate cyclase activity, in general. Our model system for assessment of alpha-2-receptor-provoked function, i.e. epinephrine-induced platelet aggregation and secretion, will be of particular significance in understanding normal and pathological hemostasis, since platelet plug formation is necessary to prevent excessive blood loss but, when occurring inappropriately, forms thrombi that can precipitate strokes or myocardial infarction.

该提案的长期目标是了解分子基础 用于肾上腺素通过α-肾上腺素能引起的生理效应 药理学α-2-亚型受体。 我们将解决这个问题 通过关注钠离子 (Na+) 的方式来实现长期目标 影响α2-受体激动剂相互作用和 α-2-受体诱导的功能。 当前的具体目标 建议 1) 纯化 α-2-受体以达到同质性，2) 评估 Na+对纯化的α-2-受体是否有影响 通过 GTP 结合蛋白异三聚体的 βγ 异二聚体 (Gi: Alpha-2-受体功能的alpha-2-受体功能或， 或者，通过 Na+/H+ 反向转运蛋白，3) 重建 α-2-肾上腺素能受体与推定的 Na+ 效应成分 脂质囊泡制剂来测试 #2 和 4 中得出的结论） 利用透化血小板来确定 Gi 是否代表 α2-受体和 Na+/H+ 交换机制之间的界面 和/或磷脂酶 A-2 活性推测参与 肾上腺素引起的血小板分泌。 Alpha-2-受体是多种激素和神经递质之一 与腺苷酸环化酶抑制相关的受体群 活动。 一系列证据表明，由此产生的 cAMP 水平的降低不足以“发出”生理信号 效应，但其他重要的生化变化也必须由 这些受体群体。 抑制cAMP积累的受体 已知均受 Na+ 调节。 我们的研究重点是 Na+ 的这一作用的基础，应该提供基本的新见解 α-2-肾上腺素能受体如何引起其生理效应 特别是，以及所使用的替代信号机制是什么 一般来说，受体与腺苷酸环化酶活性的抑制有关。 我们用于评估 α2 受体激发功能的模型系统，即 肾上腺素诱导血小板聚集和分泌， 对于理解正常和病理有特殊意义 止血，因为血小板栓塞的形成对于防止过度出血是必要的 失血，但如果发生不当，会形成血栓， 诱发中风或心肌梗塞。