Formyl peptide receptor-mediated ERK1/2 activation occurs through G(i) and is not dependent on beta-arrestin1/2.
Formyl peptide receptor (FPR) and C5a receptor (C5aR) are chemoattractant G protein-coupled receptors (GPCRs) involved in the innate immune response against bacterial infections and tissue injury. Like other GPCRs, they recruit beta-arrestin1/2 to the plasma membrane and activate the extracellular signal-regulated kinases 1 and 2 (ERK1/2). Previous studies with several GPCRs have suggested that beta-arrestins play an important role as signal transducers by scaffolding signaling molecules such as ERK1/2. This function of the beta-arrestins was not discovered until several years after their role in desensitization and endocytosis had been reported. In this study, we investigated the role of the beta-arrestins in the activation of ERK1/2 and receptor endocytosis. We took advantage of previously described mutants of FPR that have defects in G(i) coupling or beta-arrestin recruitment. The results obtained with the mutant FPRs, as well as experiments using an inhibitor of G(i) and cells overexpressing beta-arrestin2, showed that activation of ERK1/2 takes place through G(i) and is not affected by beta-arrestins. However, overexpression of beta-arrestin2 does enhance FPR sequestration from the cell surface, suggesting a role in desensitization, as shown for many other GPCRs. Experiments with CHO C5aR cells showed similar sensitivity to the G(i) inhibitor as CHO FPR cells, suggesting that the predominant activation of ERK1/2 through G protein may be a common characteristic among chemoattractant receptors.
Department of Microbiology, Montana State University, 109 Lewis Hall, Bozeman, MT 59717-3520, USA.
Jeannie M
JM
Gripentrog
Heini M
HM
Miettinen
D000818:Animals; D019390:Arrestins / Q000378:metabolism; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D004705:Endocytosis / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D050505:Mutant Proteins / Q000378:metabolism; D041681:NIH 3T3 Cells; D037342:Pertussis Toxin / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D044087:Receptor, Anaphylatoxin C5a / Q000378:metabolism; D044042:Receptors, Formyl Peptide / Q000378:metabolism*; D013997:Time Factors; D014162:Transfection; D000071557:beta-Arrestins
D019390:Arrestins; D008024:Ligands; D050505:Mutant Proteins; D044087:Receptor, Anaphylatoxin C5a; D044042:Receptors, Formyl Peptide; D000071557:beta-Arrestins; D037342:Pertussis Toxin; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D019206:GTP-Binding Protein alpha Subunits, Gi-Go