A promiscuous recognition mechanism between GPR17 and SDF-1 : molecular insights

Recent data and publications suggest a promiscuous behaviour for GPR17, a class-A GPCR operated by different classes of ligands, such as uracil nucleotides, cysteinyl-leukotrienes and oxysterols. This observation, together with the ability of several class-A GPCRs to form homo- and hetero-dimers, is likely to unveil new pathophysiological roles and novel emerging pharmacological properties for some of these GPCRs, including GPR17. This receptor shares structural, phylogenetic and functional properties with some chemokine receptors, CXCRs. Both GPR17 and CXCR2 are operated by oxysterols, and both GPR17 and CXCR ligands have been demonstrated to have a role in orchestrating inflammatory responses and oligodendrocyte precursor cell differentiation to myelinating cells in acute and chronic diseases of the central nervous system. Here, by combining in silico modelling data with in vitro validation in (i) a classical reference pharmacological assay for GPCR activity and (ii) a model of maturation of primary oligodendrocyte precursor cells, we demonstrate that GPR17 can be activated by SDF-1, a ligand of chemokine receptors CXCR4 and CXCR7, and investigate the underlying molecular recognition mechanism. We also demonstrate that cangrelor, a GPR17 orthosteric antagonist, can block the SDF-1-mediated activation of GPR17 in a concentration-dependent manner. The ability of GPR17 to respond to different classes of GPCR ligands suggests that this receptor modifies its function depending on the extracellular mileu changes occurring under specific pathophysiological conditions and advocates it as a strategic target for neurodegenerative diseases with an inflammatory/immune component.