Receptor for the chemotactic and inflammatory peptide anaphylatoxin C5a, stimulating chemotaxis, granule enzyme release, intracellular calcium release and superoxide anion production (PubMed:11773063). Also acts as a receptor for dearginated forms of C3a, C4a and C5a anaphylatoxin peptides (ASP/C3adesArg, C4adesArg and C5adesArg, respectively) (PubMed:12540846, PubMed:15833747, PubMed:19615750). Ligand binding causes a conformation change that triggers signaling via guanine nucleotide-binding proteins (G proteins) and modulates the activity of downstream effectors, such as adenylate cyclase (PubMed:12540846). C5AR1 is coupled to G(i)/G(o) (GNAI1 or GNAO1) G alpha proteins and mediates inhibition of adenylate cyclase (PubMed:12540846). {ECO:0000269|PubMed:11773063, ECO:0000269|PubMed:12540846, ECO:0000269|PubMed:15833747, ECO:0000269|PubMed:19615750}. This is the function of C5AR2 (complement C5a receptor 2, Ensembl gene identifier ENSG00000134830).