Molecular determinants of ACTH receptor for ligand binding

说明书(申请人提供)：促肾上腺皮质激素(ACTH)受体，也称为黑素皮质素-2受体(MC2R)，是黑素皮质素受体家族的一个亚型，在调节和维持肾上腺皮质功能，特别是类固醇合成方面发挥重要作用。人类MC2R(HMC2R)基因突变在家族性糖皮质激素缺乏症患者中被证实。它在童年时表现出发育不良、虚弱、疲惫和可能的肾上腺危机。因此，更好地理解hMG2R的分子基础对于理解hMC2R功能的生理学和病理学具有重要意义。它对于开发有效的治疗策略来治疗重要的人类肾上腺疾病也是至关重要的。HMC2R与其他4个克隆的黑素皮质素受体同源，这4个受体共同构成了7个跨膜区G蛋白偶联受体(GPCR)的亚家族。在过去的几年里，我们和其他研究人员进行了广泛的研究，以确定黑素皮质素家族多肽(包括激动剂a-MSH、ACTH和拮抗剂Agti信号蛋白(ASIP)、Agti相关蛋白(AGRP))与黑素皮质素受体相互作用的分子基础。然而，MC2R与激动剂ACTH和拮抗剂ASIP的结合和作用的分子决定因素仍不清楚。这项建议旨在研究负责配体结合和受体激活的hMC2R的分子决定因素。根据我们以前对其他黑素皮质素受体的研究，我们假设：1)hMC2R的跨膜区在激动剂ACTH结合和受体激活中起重要作用；2)hMC2R的胞外环和跨膜区对拮抗剂ASIP的结合和活性都是至关重要的。为了验证这一假设，我们将利用hMC2R突变和嵌合受体研究来确定hMC2R配体受体相互作用的分子基础。建议的研究将提供重要的信息，以填补我们目前对负责配体结合和受体激活的hMC2R分子决定因素的认识空白。这些信息将有助于建立一个基础，在此基础上建立一个全面的了解信号事件，这些信号事件调节ACTH介导的肾上腺功能在生理和疾病状态。

DESCRIPTION (provided by applicant): The adrenocorticotropic hormone (ACTH) receptor, also known as the melanocortin-2 receptor (MC2R), is a subtype of the melanocortin receptor family, which plays an important role in regulating and maintaining adrenocortical function, specifically steroidogenesis. Mutations of the human MC2R (hMC2R) gene have been demonstrated in human with familial glucocorticoid deficiency. It presents in childhood with failure-to thrive, weakness, fatigue and possible adrenal crisis. Therefore, a better understanding of the molecular basis of hMG2R is important to understanding the physiology and pathology of hMC2R function. It is also critical in developing effective therapeutic strategies for the treatment of important human adrenal disorders. The hMC2R is homologous to the other 4 cloned melanocortin receptors, which together form a distinct subfamily of 7 transmembrane domain G protein-coupled receptors (GPCR). Within the past several years we and other investigators have performed extensive studies to determine the molecular basis of ligand receptor interaction between the melanocortin family of peptides (including agonist a-MSH, ACTH, and antagonist Agouti signaling protein (ASIP), Agouti-related protein (AGRP)) and the melanocortin receptors. However, the molecular determinants of MC2R responsible for agonist ACTH and antagonist ASIP binding and action remain unclear. This proposal is directed towards examining the molecular determinants of hMC2R responsible for ligand binding and receptor activation. Based on our previous work with other melanocortin receptors, we hypothesize that: 1) transmembrane domains of hMC2R play important roles in agonist ACTH binding and receptor activation and 2) both extracellular loops and transmembrane domains of hMC2R are crucial for antagonist ASIP binding and activity. To test this hypothesis we will utilize the hMC2R mutagenesis and chimeric receptor studies to determine the molecular basis of hMC2R ligand receptor interaction. The proposed studies will provide important information needed to fill in the gap in our current knowledge of the molecular determinants of hMC2R responsible for ligand binding and receptor activation. The information will serve to establish a foundation on which to build a comprehensive understanding of the signaling events that regulate ACTH mediated adrenal function in physiologic and diseased states.