BASIS FOR NA+ MODULATION OF ALPHA2 RECEPTOR FUNCTION

NA 调节 ALPHA2 受体功能的基础

• 批准号: 2215815
• 负责人: LEE E LIMBIRD
• 金额: $ 27.99万
• 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 1995-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2215815
• 关键词: SDS polyacrylamide gel electrophoresis; affinity labeling; allosteric site; alpha adrenergic receptor; amiloride; animal tissue; chemical structure function; covalent bond; guanine nucleotide binding protein; iodine; ion transport; laboratory rabbit; lipid bilayer membrane; protein transport; proteolysis; radiotracer; receptor binding; sodium; stoichiometry

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.

这项提案的长期目标是了解分子基础 肾上腺素通过α-肾上腺素能神经 药理学α-2-亚型的受体。 我们将解决这个问题 长期目标是通过关注钠离子（Na+） 影响α-2-受体-激动剂相互作用， α 2受体诱导的功能。 目前的具体目标 建议是1）将α-2-受体纯化至同质，2）评估 Na+对纯化的α-2-受体的影响是否被传递 通过GTP结合蛋白异源三聚体的β γ异源二聚体（Gi： α-γ射线）调节α-2-受体功能，或者， 或者，通过Na+/H+反向转运蛋白，3）重建 α-2-肾上腺素能受体与假定的Na+效应成分， 脂质囊泡制剂，以测试#2和4中得出的结论） 利用透化血小板来确定Gi是否代表 α-2-受体与Na+/H+交换机制之间的界面 和/或磷脂酶A-2活性，推测其参与 肾上腺素引起的血小板分泌。 α-2受体是一种激素和神经递质 与腺苷酸环化酶抑制相关的受体群 活动 大量证据表明， cAMP水平的降低不足以“发出”生理信号， 影响，但其他重要的生化变化也必须引起 这些受体群体。 可抑制cAMP蓄积的受体 都被Na+所调控。 我们的研究主要集中在 Na+的这种作用的基础，应该提供基本的新见解， α-2-肾上腺素能受体如何引发其生理效应， 特别是，什么是备用信号机制所利用的 受体与腺苷酸环化酶活性的抑制有关。 我们用于评估α-2受体激发功能的模型系统，即 肾上腺素诱导的血小板聚集和分泌，将 对理解正常和病理的特殊意义 止血，因为血小板栓形成是防止过度 失血，但当发生不当时，会形成血栓， 诱发中风或心肌梗死。