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Functional characterisation of orphan g protein-coupled receptors and their validation as drug targets

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Potentially novel drug targets for pain

G-protein coupled receptors (GPCRs) form part of key cellular signalling pathways and certain members of this group play an important role in the onset of pathological states such as pain. However, scientists have yet to elucidate the function of the entire group and a number of GPCRs pose significant questions in regards to their role.


A number of GPCRs have yet to be fully characterized. In other words their natural ligands and function have not been determined. These orphan receptors are the topic of extensive study within the framework of the ORPHAN RECEPTORS project. Two such GPCRs, GPR7 and GPR8 were studied extensively as part of the project. Further information on the nature of their ligands and their expression patterns would be instrumental in deciding on their pharmaceutical potential as targets for drug discovery. Tissue distribution studies of the receptors' ligands, also identified as part of the project, showed high level presence in brain tissue and in a number of cancers. These high levels of ligands in certain tissues were indicative of potentially increased levels of expression of the receptors in those tissues. Further analysis indeed revealed elevated levels of GPR7 and GPR8 expression in certain brain regions such as the hippocampus and amygdala. The similarities in tissue distribution suggest similar roles for both GPCRs although it is likely that each plays a distinct role in the signalling pathway. Based on the distribution pattern of GPR7, researchers believe that it might be implicated in pain and eating disorders. Although further studies are needed, this constitutes a significant development towards the discovery of novel drug targets of interest in the short term.

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