AGING AND G PROTEIN COUPLED RECEPTORS IN HUMAN HEART

心脏的正常功能涉及几个G蛋白偶联的 受体，包括β-肾上腺素能，毒蕈碱，α 1-肾上腺素能， 内皮素和血管紧张素。 由于心脏功能是深刻的 受年龄的影响，与年龄相关的减少也就不足为奇了。 心脏G蛋白偶联受体的反应性已经被 记录在案。 然而，这些下降的分子基础仍然存在， 未知 在过去的十年里，大量的分子 关于通过G蛋白偶联受体的信号传导的信息， 聚集。具体来说，受体磷酸化已经成为一个主要的 GPCR信号传导中的因子。 对β-肾上腺素能和 毒蕈碱受体表明这些受体经历 磷酸化的特定激酶，这一事件破坏受体/G 蛋白质偶联 由受体特异性激酶（G蛋白）催化 受体激酶[GRK]同工酶）和第二信使激活激酶 （蛋白激酶A [PKA]和蛋白激酶C [PKC]同工酶），受体 磷酸化似乎是两者的潜在机制， 同源（激动剂依赖性）和异源（激动剂非依赖性） 脱敏。 拟议的研究将通过以下方式描述机制： 衰老会降低心脏G 蛋白偶联受体 这些研究将在心房 附属物从相对年轻的（小于或等于55 年龄）和老年（大于或等于70岁）患者 心脏手术 我们的策略是首先确定 物种受年龄的影响，然后确定潜在的机制。 第一个具体的目标将测试假设，老化改变了 三种主要成分（受体/G蛋白/效应子）的表达 酶）参与通过心脏G蛋白的信号转导- 偶联受体第二个具体目标将检验以下假设： 衰老减少受体/G蛋白偶联;在这里，我们将研究 激动剂刺激的32 P标记光亲和探针掺入 叠氮苯胺基-GTP转化为受体相关的Ga-亚基。这种方法 以前没有用于评估受体/G蛋白偶联， 老心脏 第三个具体目标将检验衰老 引起已知的蛋白激酶活性增加， 磷酸化G蛋白偶联受体。 私家侦探的范围很广 在G蛋白偶联受体的生物化学和 PI实验室中各种试剂的可用性（GRK同工酶/G 蛋白质/抗体）将PI置于独特的位置， 完成这些研究。

Normal functioning of the heart involves several G protein-coupled receptors, including beta-adrenergic, muscarinic, alpha1-adrenergic, endothelin, and angiotensin. Since cardiac performance is profoundly affected by age, it is not surprising that age-related decreases in the responsiveness of cardiac G protein-coupled receptors have been documented. The molecular bases of these decreases, however, remain unknown. Over the past decade, a considerable amount of molecular information on signaling through G protein-coupled receptors has been amassed. Specifically, receptor phosphorylation has emerged as a major factor in GPCR signaling. Extensive studies with beta-adrenergic and muscarinic receptors indicate that these receptors undergo phosphorylation by specific kinases, and this event disrupts receptor/G protein coupling. Catalyzed by receptor-specific kinases (G protein receptor kinase [GRK] isozymes) and second messenger-activated kinases (protein kinase A [PKA] and protein kinase C [PKC] isozymes), receptor phosphorylation appears to be the underlying mechanism for both homologous (agonist-dependent) and heterologous (agonist-independent) desensitization. The proposed studies will delineate the mechanism by which aging produces a decrease in the responsiveness of cardiac G protein-coupled receptors. These studies will be performed on atrial appendages obtained from relatively young (less than or equal to 55 years) and old (greater than or equal to 70 years) patients during cardiac surgery. Our strategy is to first identify the molecular species affected by age and to then determine the underlying mechanism. The first specific aim will test the hypothesis that aging changes the expression of the three main components (receptors/G proteins/effector enzymes) involved in signal transduction through cardiac G protein- coupled receptors. The second specific aim will test the hypothesis that aging diminishes receptor/G protein coupling; here we will examine agonist-stimulated incorporation of 32P-labeled photoaffinity probe azidoanilido-GTP into receptor-associated Galpha-subunits. This approach has not previously been used to assess receptor/G protein coupling in aged heart. The third specific aim will test the hypothesis that aging causes an increase in the activity of protein kinases known to phosphorylate G protein-coupled receptors. The PI's extensive experience in the biochemistry of G protein-coupled receptors and the availability of various reagents in the PI's laboratory (GRK isozymes/G proteins/antibodies) place the PI in a unique position to successfully complete these studies.