Mechanisms Ensuring Sequence-Dependent GPCR Recycling

 描述（由申请人提供）：通过肾上腺素能受体的异常交感神经信号传导是许多心血管疾病的主要原因，包括心力衰竭，心力衰竭是世界上主要的健康问题之一。交感神经控制主要通过去甲肾上腺素介导，去甲肾上腺素通过心脏细胞表面的肾上腺素能受体发出信号。与此一致，靶向肾上腺素能信号通路的药物多年来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，这降低了细胞对交感神经刺激的敏感性。内体中的一个关键的分选步骤，它要么将受体重新聚集到细胞表面，要么引导它们被降解，然后决定细胞是否以及以多快的速度恢复它们的敏感性。最近的证据表明，将受体分选到介导再循环的内体上的专门结构域也允许受体与专门的信号传导复合物相互作用，并启动具有离散功能的信号传导途径。使用原型G蛋白偶联受体（GPCR）如β 2-肾上腺素能受体（B2 AR）的研究已经确定，GPCR需要其C末端上的特定序列，以及一组与这些序列相互作用的蛋白质，以进入该途径并再循环。破坏这些相互作用将B2 AR重定向到溶酶体。为什么会这样，考虑到许多其他蛋白质可以通过“批量”回收途径回收而没有任何明显的要求，这是一个尚未回答的基本问题。该提案解决了B2 AR如何从批量再循环途径中排除，以及为什么这在肾上腺素能信号传导中很重要。实验测试了以下假设：特定的内体机制主动将B2 AR从大量再循环途径中排除，并且这种排除调节了来自内体相对于质膜的B2 AR信号传导的偏差。所采取的方法是首先确定将B2 AR排除在本体途径之外的机制，然后破坏它以确定信号传导的后果。更好地了解调节肾上腺素能受体再循环的机制将为通过确定潜在的干预切入点来开发新的心力衰竭治疗策略提供平台。此外，由于B2 AR是信号受体的G蛋白偶联受体家族的原型成员，其成员显示出很强的结构和功能相似性，因此开发的技术和鉴定的原理将广泛适用于该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.