REGULATION OF A 2-ADRENERGIC RECEPTORS/ADENYLATE CYCLASE

去甲肾上腺素和肾上腺素是重要的神经递质 中枢神经系统和阿尔法-2肾上腺素能受体， 它们与腺苷环化酶的抑制相结合，是 分布广泛。临床上，α-2肾上腺素能激动剂 可乐定和呋喃西林也可用于治疗高血压 其他几种疾病。而可乐定被认为是作用于 集中控制血压，其作用机制不是 很好理解。α-2肾上腺素能药物的治疗作用 激动剂通常只有在慢性治疗后才能显现出来， 暗示了适应性变化的参与。因此，一个更好的 对其调控和作用机制的认识 α-2肾上腺素能受体及其与受体的偶联 腺苷环化酶的调节对 开发更好的药物疗法。该计划的总体目标 拟议的研究是为了了解 α-2肾上腺素能受体预培养对细胞的影响 激动剂对随后的α-2肾上腺素能受体结合和 腺苷环化酶的活性。主要有两种 影响有待研究。首先是受体的下调。 环状AMP反应的数目和脱敏。第二, 我们最近观察到，α-2激动剂的预处理 结果Forsklin刺激的环磷酸腺苷增加了20倍 合成，我们称之为“敏化”。对于这两组研究， 所使用的模型系统是HT29细胞系。每种效果 将被表征，然后它的分子机制 调查过了。对于第一个效应，要检验的假设是 α2肾上腺素能受体的作用机制 脱敏：解偶联；受体内化；以及 感受器丢失。我们的初步研究表明，“敏化”是 不是通过环磷酸腺苷介导的。因此，其他机制 已被认为与α-2肾上腺素能受体的作用有关，如 以及其他第二信使系统，将被调查。 更多的实验旨在调查可能的 腺苷环化酶系统的分子变化导致 致敏时可见环化AMP生成增加。

Norepinephrine and epinephrine are important neurotransmitters in the central nervous system, and alpha-2 adrenergic receptors, which are coupled to the inhibition of adenylate cyclase, are widely distributed. Clinically, alpha-2 adrenergic agonists such as clonidine and guanabenz are used to treat hypertension as well as several other disorders. While clonidine is thought to act centrally to control blood pressure, its mechanism of action is not well understood. The therapeutic effects of alpha-2 adrenergic agonists often are evident only after chronic treatment, suggesting the involvement of adaptive changes. Thus, a better understanding of the regulation and the mechanism of action of alpha-2 adrenergic receptors, their coupling to and their regulation of adenylate cyclase has a clear potential for the development of better drug therapies. The overall goal of the proposed research is to understand the molecular basis for the effects of preincubation of cells with an alpha-2 adrenergic agonist on subsequent alpha-2 adrenergic receptor binding and the activity of the enzyme adenylate cyclase. There are two main effects to be studied. The first is the down-regulation of receptor number and desensitization of the cyclic AMP response. Second, we have recently observed that alpha-2 agonist pretreatment results in a 20-fold increase in forskolin stimulated cyclic AMP synthesis, which we call "sensitization". For both sets of studies, the model system to be used is the HT29 cell line. Each effect will be characterized and then its molecular mechanism investigated. For the first effect, the hypothesis to be tested is that the mechanism of alpha-2 adrenergic receptor desensitization: uncoupling; receptor internalization; and receptor loss. Our initial studies indicate that "sensitization" is not mediated through cyclic AMP. Thus, other mechanisms which have been suggested for alpha-2 adrenergic receptor action, as well as other second messenger systems, will be investigated. Additional experiments are aimed at investigating the possible molecular alterations in the adenylate cyclase system which cause the increased cyclic AMP production seen with sensitization.