Tails of the unexpected - an atypical receptor for the chemokine RANTES/CCL5 expressed in brain.

Chemokines and their receptors play a central role in the trafficking of leukocytes within the body, a process which is amenable to antagonism by small molecules and which holds promise as a treatment for clinically important diseases. In the issue of the British Journal of Pharmacology accompanying this commentary, Ignatov and colleagues describe an unexpected role for the chemokine RANTES/CCL5, namely an ability to signal via the orphan G protein-coupled receptor named GPR75. This receptor bears little homology to other chemokine receptors, most strikingly within the putative intracellular domains, with the third loop and C-terminal tail dwarfing those of other known chemokine receptors. This most likely accounts for the atypical pertussis toxin-insensitive signalling induced by RANTES. Intriguingly, this signalling is neuro-protective, inducing the survival of a hippocampal cell line following insult with the neurotoxic amyloid-beta peptide. Since this peptide is implicated in the pathogenesis of Alzheimer's disease, it may be that exploitation of this signalling pathway presents itself as a future therapeutic treatment.