Mechanisms Ensuring Sequence-Dependent GPCR Recycling

 描述(申请人提供)：通过肾上腺素能受体的异常交感信号是许多心血管疾病的主要原因，包括心力衰竭，这是世界上主要的健康问题之一。交感神经的控制主要是通过去甲肾上腺素来实现的，去甲肾上腺素通过存在于心肌细胞表面的肾上腺素能受体传递信号。与此一致的是，多年来，针对肾上腺素能信号通路的药物一直是治疗心血管疾病和心力衰竭的主要药物。肾上腺素能受体激活启动重要的调节事件，导致它们从细胞表面移除，从而降低细胞对交感刺激的敏感性。内体中的一个关键的分类步骤，它要么将受体回收回细胞表面，要么指示它们被降解，然后决定细胞是否以及以多快的速度恢复其敏感性。最近的证据表明，将受体分类到内体上介导循环的特定区域也允许受体与特定的信号复合体相互作用，并启动具有离散功能的信号通路。使用典型的G蛋白偶联受体(GPCRs)，如β2-肾上腺素能受体(B2AR)的研究证实，GPCRs需要其C末端的特定序列，以及一系列与这些序列相互作用的蛋白质，才能进入这一途径并循环。破坏这些相互作用会将B2AR重定向到溶酶体。考虑到许多其他蛋白质可以在没有任何明显要求的情况下通过“大量”循环途径进行循环，为什么会这样，这是一个尚未得到回答的根本问题。这项建议解决了B2AR如何被排除在批量循环途径之外，以及为什么这在肾上腺素能信号转导中是重要的。实验验证了这样一种假设，即特定的内体机械主动地将B2AR排除在大宗循环途径之外，并且这种排除调节了B2AR信号从内体到质膜的偏向。所采取的方法是首先确定将B2AR排除在主体途径之外的机制，然后破坏它以确定对信号传递的影响。更好地了解肾上腺素能受体循环的调节机制，将通过确定潜在的干预切入点，为开发针对心力衰竭的新治疗策略提供平台。此外，由于B2AR是G蛋白偶联受体信号受体家族的典型成员，其成员在结构和功能上显示出强烈的相似性，因此开发的技术和确定的原理将广泛适用于这一临床相关信号受体家族的其他成员。

 DESCRIPTION (provided by applicant): Abnormal sympathetic signaling through adrenergic receptors is a major cause for many cardiovascular diseases, including heart failure, which is one of the leading health problems around the world. Sympathetic control is mediated mainly through norepinephrine, which signals via adrenergic receptors present on the surface of cardiac cells. Consistent with this, drugs targeting the adrenergic signaling pathway have been the mainstay for managing cardiovascular diseases and cardiac failure for many years. Adrenergic receptor activation initiates important regulatory events that cause their removal from the cell surface, which reduces cellular sensitivity to sympathetic stimuli. A critical sortin step in the endosome, which either recycles receptors back to the cell surface or directs them to be degraded, then decides whether and how fast cells recover their sensitivity. Recent evidence suggests that the sorting of receptors to specialized domains on the endosome that mediate recycling also allow receptors to interact with specialized signaling complexes and initiate signaling pathways with discrete functions. Research using prototypical G protein-coupled receptors (GPCRs) like the beta 2-adrenergic receptor (B2AR), has established that GPCRs require specific sequences on their C-termini, as well as a set of proteins that interact with thes sequences, to enter this pathway and recycle. Disrupting these interactions redirects B2AR to the lysosome. Why this is so, considering that many other proteins can recycle via a "bulk" recycling pathway without any apparent requirements, is a fundamental question that has not been answered. This proposal addresses how B2AR is excluded from the bulk recycling pathway, and why this is important in adrenergic signaling. The experiments test the hypothesis that specific endosomal machinery actively excludes B2AR from the bulk recycling pathway, and that this exclusion regulates the bias of B2AR signaling from the endosome vs. the plasma membrane. The approach taken is to first identify the machinery that excludes B2AR from the bulk pathway, and then disrupt it to determine the consequences on signaling. A better understanding of the mechanisms that regulate adrenergic receptor recycling will provide a platform for developing new therapeutic strategies against heart failure by identifying potential entry points for intervention. Further, as B2AR is a prototypical member of the G protein-coupled receptor family of signaling receptors, whose members show strong structural and functional similarities, the techniques developed and the principles identified will be broadly applicable to other members of this clinically relevant family of signaling receptors.