RANTES stimulates Ca2+ mobilization and inositol trisphosphate (IP3) formation in cells transfected with G protein-coupled receptor 75.
OBJECTIVE
RANTES is an inflammatory chemokine with a critical role in T-lymphocyte activation and proliferation. Its effects are mediated through G protein-coupled heptahelical receptors (GPCRs). We show for the first time that RANTES activates the orphan G protein-coupled receptor 75 (GPR75).


METHODS
To identify a ligand for GPR75 we have used three different and independent methods, namely luciferase assay, bioluminescence assay and IP3 accumulation assay.


RESULTS
Treatment of cells expressing GPR75 with subnanomolar concentrations of RANTES led to stimulation of the luciferase activity in a reporter-gene assay, an increase in inositol trisphosphate, and intracellular Ca2+. The latter effect was blocked by the phospholipase-C inhibitor (PLC) U73122 indicating that Gq proteins mediate GPR75 signaling. RANTES enhanced the phosphorylation of AKT and mitogen-activated protein kinase (MAPK) in GPR75-transfected cells and this effect was blocked by the PLC inhibitor U73122 and the phosphatidylinositol 3-kinase (PI3K) inhibitor, wortmannin. The hippocampal cell line HT22, which expresses GPR75 endogenously, but not the other known RANTES receptors, was used to study the effects of RANTES and GPR75 on neuronal survival. Treatment of HT22 cells with RANTES significantly reduced the neurotoxicity of amyloid-beta peptides, by activating PLC and PI3K.


CONCLUSIONS
This demonstrate clearly and undoubtedly the ability of RANTES to act on GPR75. Defects in the RANTES/GPR75-signaling pathway may contribute to neuroinflammatory and neurodegenerative processes as observed in Alzheimer's disease.
Ignatov
A
A
Zentrum für Molekulare Neurobiologie Hamburg, Universität Hamburg, Hamburg, Germany. atanas.ignatov@medizin.uni-magdeburg.de
Robert
J
J
Gregory-Evans
C
C
Schaller
H C
HC
D016229:Amyloid beta-Peptides / Q000494:pharmacology; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D018946:Chemokine CCL5 / Q000494:pharmacology*; D006224:Cricetinae; D003412:Cricetulus; D004305:Dose-Response Relationship, Drug; D004963:Estrenes / Q000494:pharmacology; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D007293:Inosine Triphosphate / Q000096:biosynthesis*; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008163:Luminescent Measurements / Q000379:methods; D008297:Male; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D011760:Pyrrolidinones / Q000494:pharmacology; D043562:Receptors, G-Protein-Coupled / Q000235:genetics* / Q000378:metabolism; D014162:Transfection; D000077191:Wortmannin
D016229:Amyloid beta-Peptides; D000730:Androstadienes; D018946:Chemokine CCL5; D004963:Estrenes; C120151:GPR75 protein, human; D011760:Pyrrolidinones; D043562:Receptors, G-Protein-Coupled; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D007293:Inosine Triphosphate; D008156:Luciferases; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D002118:Calcium; D000077191:Wortmannin