Anti-Complement receptor C5aR (CD88) Antibody, clone S5/1 clone S5/1, from mouse

C5a anaphylatoxin chemotactic receptor 1 (UniProt: P21730; also known as C5a anaphylatoxin chemotactic receptor, C5a-R, C5aR, CD88) is encoded by the C5AR1 (also known as C5AR, C5R1) gene (Gene ID: 728) in human. C5aR is a multi-pass membrane protein that serves as a receptor for the chemotactic and inflammatory peptide anaphylatoxin C5a. It exists as a homodimer, but can also form higher-order oligomers. C5a interacts with at least two sites on the receptor: a high-affinity site on the extracellular N-terminus, and a second site in the transmembrane region, which activates downstream signaling events. Receptor activation stimulates chemotaxis, granule enzyme release, and intracellular calcium release and superoxide anion production. Chemotaxis inhibitory protein of Staphylococcus aureus (CHIPS), a 121-residue protein, is reported to bind to the N-terminus of the C5aR (aa 1-35) with nanomolar affinity and inhibits C5a-mediated responses in human leukocytes. Sulfation at Tyrosine 14 is shown to be important for CHIPS binding. Upon C5a binding, C5aR) undergoes rapid phosphorylation on the six serine residues present in the C-terminal region followed by desensitization and internalization. The key residues involved in this process are Serine 334 and Serine 338. Phosphorylated C5aR is shown to co-localize with beta-arrestin 1 and 2 in cytoplasmic vesicles. Although C5aR activation is able to promote a loose association with beta-arrestins, but phosphorylation of either Serine 334)/338 or Serine 327)/338 is reported to be essential for the formation of a persistent complex. (Ref.: Ippel, JH., et al., (2009). J. Biol. Chem. 284(18); 12363 12372; Braun, L., et al. (2003). J. Biol. Chem. 278(6); 4277-4285).