Receptor for the chemotactic and inflammatory peptide anaphylatoxin C5a (PubMed:1847994, PubMed:8182049, PubMed:7622471, PubMed:9553099, PubMed:10636859, PubMed:15153520, PubMed:29300009). The ligand 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 (PubMed:8182049, PubMed:7622471, PubMed:9553099). Receptor activation stimulates chemotaxis, granule enzyme release, intracellular calcium release and superoxide anion production (PubMed:10636859, PubMed:15153520). Homodimer. May also form higher-order oligomers (PubMed:12835319). Interacts (when phosphorylated) with ARRB1 and ARRB2; the interaction is associated with internalization of C5aR (PubMed:12464600). Interacts (via N-terminal domain) with S.aureus chemotaxis inhibitory protein (CHIPS); the interaction blocks the receptor and may thus inhibit the immune response (PubMed:15153520, PubMed:15542591, PubMed:21706042). Phosphorylated C5aR colocalizes with ARRB1 and ARRB2 in cytoplasmic vesicles. Sulfation plays a critical role in the association of C5aR with C5a, but no significant role in the ability of the receptor to transduce a signal and mobilize calcium in response to a small a small peptide agonist (PubMed:11342590). Sulfation at Tyr-14 is important for CHIPS binding (PubMed:21706042). Phosphorylated on serine residues in response to C5a binding, resulting in internalization of the receptor and short-term desensitization to the ligand. The key residues involved in this process are Ser-334 and Ser-338. Belongs to the G-protein coupled receptor 1 family.