Molecular Mechanisms of AgRP Signaling

项目摘要 在大脑中，控制新陈代谢功能和摄食行为的关键焦点是 黑素皮质素受体MC3R和MC4R。这些受体与两种配体反应， α-黑素细胞刺激素(a-MSH)和刺鼠相关蛋白(AgRP)， 它们以相反的方式促进正负能量平衡， 分别进行了分析。最近的研究证明了AgRP释放的深远重要性 神经元在代谢和体重动态平衡中的作用。这项计划的目标是 了解AgRP作用的分子基础，从而实现新的治疗策略 与肥胖和代谢性疾病有关的各种情况。我们实验室的新发现 极大地改变了我们对α-MSH和AgRP作用的理解。海流 范式假设，这些分子的作用是刺激或抑制 夏令营第二信使。然而，使用蛋白质设计，我们证明了AgRP MCR结合核心外片段的突变对 长期喂养，同时完全离开受体亲和力和cAMP抑制 与野生型相比没有变化。此外，新的合作结果发现，AgRP 通过cAMP促进内向整流钾通道的开放 独立的机制，这种作用直接依赖于这些外周AgRP 细分市场。本应用程序的目标1将通过确定AgRP如何 序列和构象驱动钾通道电流。这将会被测试 通过蛋白质设计、核磁共振结构测定，以及与新人类 全外显子组分析鉴定AgRP肥胖连锁突变。Aim 2将研究如何 Syndecan-3，一种带负电荷的膜结合蛋白多糖，促进AgRP 发信号。这将通过生物物理实验和通过 将设计的蛋白质用于野生型和野生型的比较研究 Syndecan-3基因敲除小鼠，随后进行喂养试验和脑组织成像。目标3 将在AgRP设计上展开努力，以生产稳定的蛋白质来测试其作用 蛋白分解抵抗促进AgRP的长期作用，并作为治疗的先导 癌症恶病质，一种以极度食欲不振和消瘦为特征的消瘦状态 组织退化。

Project Summary In the brain, key focal points for control of metabolic function and feeding behavior are melanocortin receptors MC3R and MC4R. These receptors respond to two ligands, alpha-melanocyte stimulating hormone (a-MSH) and the agouti-related protein (AgRP), which act in opposite ways to promote negative and positive energy balance, respectively. Recent research demonstrates the profound importance of AgRP releasing neurons in metabolism and body weight homeostasis. The goal of this program is to understand the molecular basis of AgRP action, thus enabling new strategies for treating diverse conditions linked to obesity and metabolic diseases. New findings from our lab are significantly reshaping our understanding of a-MSH and AgRP action. The current paradigm posits that these molecules act to stimulate or suppress production of the cAMP second messenger. However, using protein design, we demonstrated that AgRP mutations in segments outside of the MCR binding core exert a profound influence on long term feeding, while leaving receptor affinity and cAMP suppression completely unchanged relative to wild-type. Moreover, new collaborative results find that AgRP promotes the opening of inward rectifying potassium channels through a cAMP independent mechanism, an effect that is directly dependent on these peripheral AgRP segments. Aim 1 of this application will expand these studies by identifying how AgRP sequence and conformation drive potassium channel currents. This will be tested through protein design, NMR structure determination, as well as with a new human AgRP obesity-linked mutant identified by whole exome analysis. Aim 2 will examine how syndecan-3, a negatively charged, membrane bound proteoglycan, facilitates AgRP signaling. This will be accomplished with biophysical experiments and through comparison studies where designed proteins are administered to wild-type and syndecan-3 knockout mice, followed by feeding trials and brain tissue imaging. Aim 3 will expand on AgRP design efforts to produce stable proteins to test the role of proteolytic resistance in promoting long-term AgRP action, and as leads for treating cancer cachexia, a wasting condition characterized by extreme loss of appetite and lean tissue degradation.