Non-canonical G protein signalling: toward new therapeutic avenues (360G-Wellcome-215229_Z_19_Z)

G protein-coupled receptors (GPCRs) represent the largest family of cell surface proteins. Agonist binding to GPCRs activates G proteins regulating many cellular effectors. Classically, G protein activation occurs at the plasma membrane and is rapidly terminated by beta-arrestin recruitment to the activated GPCRs, promoting G protein uncoupling from receptor, GPCR internalisation and signalling arrest. However, recent studies revealed that upon internalisation, some GPCRs continue to activate G proteins from internal compartments leading to sustained production of second messengers far from the plasma membrane. This different spatiotemporal signalling profile allows distinct cellular functions from the ones occurring at the plasma membrane that can be exploited in the near future to design new pharmacological approaches. My collaborators and I recently observed that for some GPCRs such as the vasopressin type 2 receptor, formation of a GPCR-G protein-beta-arrestin complex (baptised megaplex) in internal compartments is required for non-canonical Gs protein signalling. The initial research programme I propose aims to tackle the following important questions underlying this novel signalling mode: 1. Is G protein selectivity different at intracellular compartments vs at plasma membrane? 2. Is megaplex formation restricted to Gs isoform? 3. What is the specific role of beta-arrestin within the megaplex?