Subcellular organization of Adhesion G-Protein Coupled Receptor (aGPCR) signalling.

点击翻译按钮获取中文摘要

The long-term objectives of my research program are to understand G-protein coupled receptor function. G-protein-coupled receptors (GPCRs) sense and traduce signals from numerous effector molecules and play an essential role in coordinating the ability of cells to rapidly respond to its environment. Specifically, my research is focused on understanding function of non-canonically activated G-protein coupled receptors (GPCRs). This proposal will focus on the Adhesion G-protein-coupled Receptor-G1 (ADGRG1; also known as GPR56). ADGRG1 is a member of the autocatalytically activated Adhesion Family of GPCRs. ADGRG1 undergoes an auto-catalytic event at a site called the GPCR proteolysis site (GPS), that results in the cell surface expression of a heterodimer consisting of 2 chains, a large extracellular N-terminal fragment (ADGRG1-NT) and a membrane-bound C-terminal fragment (ADGRG1-CT) which remain associated and non-covalently linked. It is believed that the ADGRG-NT is removed from ADGRG-CT through binding to extracellular matrix components and shear force resulting in ADGRG1-CT disinhibition, release and engagement of a tethered ligand and receptor signalling through G--proteins and ß--arrestin. The unique proteolytic mode of activation for ADGRG1 results in irreversible activation and these receptors are often described as "one and done" GPCRs. This is in contrast to the reversible binding of a soluble hormone that activates most well studies GPCRs such as the ß2--adrenergic receptor (ß2-AR) or the angiotensin II receptor type 1 (AT1) that are frequently recycled back to the cell surface following internalization and dissociation of the ligand from the receptor. It follows that adhesion GPCRs might engage intracellular sorting mechanisms and compartmentalized signalling that are distinct from those for soluble hormone binding GPCRs. Overarching hypothesis: ADGRG1 engages intracellular vesicular trafficking and signalling pathways that are distinct from other hormone activated GPCRs such as ß2-AR and AT1 as a result of irreversible auto-catalytic activation. In order to understand ADGRG1 signalling and trafficking, in the short-term, we will: Aim 1. Define ADGRG1 C-terminal tail amino acid sequences regulating interaction with the ß--arrestins. Aim 2. Define the vesicular trafficking route for internalization of ADGRG1 and the vesicular trafficking route for de-novo synthesized receptor trafficking to the cell membrane. Aim 3. Define the cell surface and endosomal signalling repertoire for ADGRG1. Significance: These studies will address fundamental questions regarding the signaling and vesicular transport mechanisms of a non-canonically activated GPCR. Given the important physiological roles and unique mechanisms of activation of this class of receptors, it is likely that these studies will reveal the diversity of pathways and mechanisms regulating the signaling and endocytic fate of GPCRs.