The role of GPR56 in platelet function

项目摘要/摘要 黏附G蛋白偶联受体(AGPCRs)是GPCR超家族的第二大亚类， 由33个成员组成，可细分为9个亚科。这一亚群中的大多数受体 具有不同长度的N-末端，其具有GPCR型自蛋白分解诱导(GAIN)结构域，该结构域介导自 裂解成两个裂解的受体原基，N末端片段(NTF)和细胞质C末端 片段(CTF)，它们在质膜上保持非共价相互联系。此前，我们 已经发现，NTF的尿素解离揭示了一个神秘的N-末端茎，包括被拴住的茎 多肽激动区，作用于七个跨膜(7TM)，激活G蛋白信号。虽然 AGPCRNTF的生化解离为研究拴系肽激动剂提供了宝贵的信息。 机制，但支持这一点的生理机制仍不清楚。我们假设一个剪切力 诱导机制可能是将NTF解离，揭示拴系肽激动剂激活aGPCR的作用。我们 已经发现了内源性表达aGPCRGPR56的血小板，GPR56已知与胶原蛋白相互作用， 是研究我们提出的从GPR56中去除NTF的剪切力诱导机制的理想模型。 该模型也有助于进一步阐明GPR56在血小板功能中的作用，特别是在止血方面。 和血栓形成。除了体外剪切力分离方法外，体外和体内小鼠模型 止血和血栓形成的知识将被用来帮助理解和验证潜在的机制 GPR56的激活模式。重要的是，这个项目强调了一种栓系多肽激动剂的用途。 机制作为研究aGPCR激活和识别内源性细胞系统上的新受体的工具。 了解aGPCR在血小板中的激活机制，如GPR56，可能会带来新的治疗方法 治疗异常的血小板相关疾病、出血和血栓并发症的药物设计。

PROJECT SUMMARY/ABSTRACT Adhesion G protein-coupled receptors (aGPCRs) are the second largest subset of the GPCR superfamily, comprising of 33 members that can be subdivided into nine subfamilies. Majority of the receptors in this subset have varying length of the N-termini with a GPCR-autoproteolysis-inducing (GAIN) domain that mediates self- cleavage into two cleaved receptor protomers, the N-terminal fragment (NTF) and the cytoplasmic C-terminal fragment (CTF), that remain noncovalently associate with each other on the plasma membrane. Previously, we had identified that urea-dissociation of the NTF unveils a cryptic N-terminal stalk, encompassing the tethered peptide agonist region, that acts on the seven transmembrane (7TM) to activate G protein signaling. Although the biochemical dissociation of the NTF of aGPCR, provided invaluable insight into a tethered-peptide-agonist mechanism, the physiological mechanism that supports this remains unknown. We postulate that a shear-force induced mechanism would dissociate the NTF to reveal the tethered-peptide agonist to activate aGPCR. We have identified platelets that endogenously express aGPCR, GPR56, which is known to interact with collagen, to be an ideal model to investigate our proposed shear-force induced mechanism of NTF removal from GPR56. This model will also facilitate in further elucidating the role of GPR56 in platelet function, especially in hemostasis and thrombosis. In addition to the in vitro shear-force dissociation approaches, ex vivo and in vivo mouse models of hemostasis and thrombosis will be employed to aid in understanding and validating the underlying mechanism of GPR56 mode of activation. Importantly this project underlies the utility of a tethered-peptide-agonist mechanism as a tool to study aGPCR activation and identify novel receptors on an endogenous cell system. Understanding the mechanism of aGPCR, such as GPR56, activation in platelets may lead to new therapeutic drug design to treat aberrant platelet-related disorders, bleeding and thrombotic-complications.