Mechanisms of Adhesion GPCR Action

总结/摘要： G蛋白偶联受体（GPCRs）是跨细胞传递化学或激素刺激信息的一种受体 膜以激活异源三聚体G蛋白，从而引发生理/细胞反应。粘附G 蛋白偶联受体（aGPCR）包含33个成员的GPCR亚家族，其已经成为 由于对这些受体在体内的作用的理解不断扩大， 发育障碍和成人癌症。尽管进行了大量的研究， 在我们最近的工作之前，从未有任何aGPCR家族成员激活G蛋白。我们 利用我们开发的一种新技术， 蛋白α亚基和两个粘附GPCR介导的成功重建G蛋白活化 （GPR 56和GPR 110）。我们确定了GPR 56和GPR 110激活的G蛋白亚型， 两种受体的胞外片段抑制受体部分的G蛋白激活活性 插入膜中的结构域（TM或跨膜结构域）。受体激活发生在 抑制性细胞外片段从TM结构域解离，可能是通过蛋白质配体的作用， 这一作用暴露了作用于自身的TM结构域的一小部分 以正调控方式（系留激动剂）。这些初步数据使我们提出， 粘附GPCR类在受系留激动剂调节方面具有共同的作用机制。我们 寻求验证GPR 56、GPR 114和第VI组粘附GPCR的机制，并执行详细的 研究以确定系留激动剂的确切组成及其与TM结构域接合的方式。 我们将进行研究，调查受体的天然配体的作用方式，以揭示拴系的 激动剂，同时我们从分子上鉴定真正的受体配体。小分子化学文库的筛选 将进行鉴定合成的粘附GPCR调节剂。这些化合物将极大地帮助我们 机制研究作为研究工具，并可能发现使用的线索，以阻止病理生理作用， 疾病背景下的粘附GPCR。了解粘附GPCR的作用机制是一个预 这是开发用于越来越多的归因于该GPCR类别的疾病的疗法所必需的。 我们的工作致力于阐明粘附GPCR作用的机制。

Summary/Abstract: G protein Coupled Receptors (GPCRs) transduce information from chemical or hormonal stimuli across the cell membrane to activate heterotrimeric G proteins and thereby elicit physiological/cellular responses. Adhesion G Protein Coupled Receptors (aGPCRs) comprise a 33-member sub-family of GPCRs that have become subjects of intense investigation due to an expanding understanding of the roles these receptors have in developmental disorders and adult cancers. Despite the intense study, direct measurements of heterotrimeric G protein activation by any aGPCR family member had never been made until our very recent work. We leveraged a new technology that we developed to purify large quantities of all classes of heterotrimeric G protein α subunits and successfully reconstituted G protein activation mediated by two adhesion GPCRs (GPR56 and GPR110). We determined the G protein subtypes that GPR56 and GPR110 activate and found that the extracellular fragments of both receptors inhibit the G protein activating activity of the receptor portion that is intercalated in the membrane (TM or Trans-membrane domain). Receptor activation occurs when the inhibitory extracellular fragment is dissociated from the TM domain, perhaps by the action of protein ligands in the extracellular space that bind to it. This act unmasks a short portion of the TM domain that acts upon itself in positive regulatory fashion (a tethered agonist). These preliminary data lead us to propose that the entire adhesion GPCR class shares a common mechanism of action in being regulated by tethered agonists. We seek to verify the mechanism for GPR56, GPR114, and the Group VI adhesion GPCRs and perform detailed studies to define the exact composition of the tethered agonist and the way that it engages the TM domain. We will conduct studies to investigate the way that natural ligands of the receptors act to reveal the tethered agonist while we molecularly identify authentic receptor ligands. Screens of small molecule chemical libraries will be conducted to identify synthetic adhesion GPCR modulators. These compounds will greatly aid our mechanistic studies as research tools and may find use as leads to block the pathophysiologic actions of adhesion GPCRs in disease contexts. Understanding the mechanism of action of adhesion GPCRs is a pre- requisite to the development of therapies for the increasing number of diseases ascribed to this GPCR-class. Our work strives to elucidate the mechanism of adhesion GPCR action.