C5a-stimulated recruitment of beta-arrestin2 to the nonsignaling 7-transmembrane decoy receptor C5L2.
C5L2 (or GPR77) is a high-affinity receptor for the complement fragment C5a and its desarginated product, C5a-desArg. Unlike the classical C5a receptor CD88, C5L2 does not couple to intracellular G-protein-signaling pathways but is thought to function as a decoy receptor. The authors show that stimulation of C5L2 with C5a and C5a-desArg induces redistribution of green fluorescent protein-labeled beta-arrestin2 to cytoplasmic vesicles. C3a and C3a-desArg were inactive in the beta-arrestin translocation assay. Direct interaction of ligand-stimulated C5L2 with beta-arrestin was confirmed using a novel beta-galactosidase fragment complementation assay. In this assay, C5L2 was labeled with a mutationally altered peptide fragment of beta-galactosidase, whereas beta-arrestin2 was labeled with a corresponding deletion mutant of the enzyme. Stable transfection of the modified C5L2 and subsequent stimulation with C5a or C5a-desArg restored beta-galactosidase activity in a dose-dependent manner. The subnanomolar potency of beta-arrestin coupling in the beta-galactosidase fragment complementation assay is in agreement with the affinity of the receptor-ligand interaction. C5L2 is the first example of a 7-transmembrane decoy receptor that couples to beta-arrestin in a ligand-dependent manner. This observation supports the notion that G-protein-signaling and beta-arrestin coupling can be 2 separate activities of 7-transmembrane receptors. Furthermore, the beta-arrestin assays described in this article provide methods of screening for selective C5L2 modulators.
Van Lith
Lambertus H C
LH
Schering-Plough Research Institute, Oss, The Netherlands.
Oosterom
Julia
J
Van Elsas
Andrea
A
Zaman
Guido J R
GJ
D000818:Animals; D019390:Arrestins / Q000235:genetics / Q000378:metabolism*; D016466:CHO Cells; D015936:Complement C5a / Q000235:genetics / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D004305:Dose-Response Relationship, Drug; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D044087:Receptor, Anaphylatoxin C5a; D019707:Receptors, Chemokine / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D000071557:beta-Arrestins
D019390:Arrestins; C417003:C5aR2 protein, human; D044087:Receptor, Anaphylatoxin C5a; D019707:Receptors, Chemokine; D011993:Recombinant Fusion Proteins; D000071557:beta-Arrestins; D015936:Complement C5a; D048049:Extracellular Signal-Regulated MAP Kinases