The C5a Receptor (C5aR) C5L2 Is a Modulator of C5aR-mediated Signal Transduction

• Published in: The Journal of biological chemistry Vol. 285; no. 10; pp. 7633 - 7644
• Main Authors: Bamberg, Claire E., Mackay, Charles R., Lee, Hyun, Zahra, David, Jackson, Jenny, Lim, Yun Si, Whitfeld, Peter L., Craig, Stewart, Corsini, Erin, Lu, Bao, Gerard, Craig, Gerard, Norma P.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 05.03.2010; American Society for Biochemistry and Molecular Biology
• Subjects: 7-Helix Receptor; Anaphylatoxin Receptors; Animals; Arrestins - metabolism; beta-Arrestins; Cell Line; Chemotaxis; Chemotaxis, Leukocyte - physiology; Complement; Enzyme Activation; Extracellular Signal-Regulated MAP Kinases - metabolism; G Protein-coupled Receptors (GPCR); Gene Expression Profiling; Humans; Inflammation; Mice; Mice, Inbred C57BL; Models, Molecular; Neutrophil; Neutrophils - cytology; Neutrophils - metabolism; Oligonucleotide Array Sequence Analysis; Receptor, Anaphylatoxin C5a - chemistry; Receptor, Anaphylatoxin C5a - genetics; Receptor, Anaphylatoxin C5a - metabolism; Receptors; Receptors, Chemokine - chemistry; Receptors, Chemokine - genetics; Receptors, Chemokine - metabolism; Signal Transduction; Signal Transduction - physiology; Tissue Distribution; G Protein-coupled Receptors (GPCR); Receptors; Signal Transduction; Anaphylatoxin Receptors; Complement; 7-Helix Receptor; Inflammation; Neutrophil; Chemotaxis
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M109.092106

The complement anaphylatoxin C5a is a proinflammatory component of host defense that functions through two identified receptors, C5a receptor (C5aR) and C5L2. C5aR is a classical G protein-coupled receptor, whereas C5L2 is structurally homologous but deficient in G protein coupling. In human neutrophils, we show C5L2 is predominantly intracellular, whereas C5aR is expressed on the plasma membrane. Confocal analysis shows internalized C5aR following ligand binding is co-localized with both C5L2 and β-arrestin. Antibody blockade of C5L2 results in a dramatic increase in C5a-mediated chemotaxis and ERK1/2 phosphorylation but does not alter C5a-mediated calcium mobilization, supporting its role in modulation of the β-arrestin pathway. Association of C5L2 with β-arrestin is confirmed by cellular co-immunoprecipitation assays. C5L2 blockade also has no effect on ligand uptake or C5aR endocytosis in human polymorphonuclear leukocytes, distinguishing its role from that of a rapid recycling or scavenging receptor in this cell type. This is thus the first example of a naturally occurring seven-transmembrane segment receptor that is both obligately uncoupled from G proteins and a negative modulator of signal transduction through the β-arrestin pathway. Physiologically, these properties provide the possibility for additional fine-tuning of host defense.