C3a binds to C3a receptor, a G-protein coupled receptor which couples to Gi upon activation. Like all other members of the superfamily, C3a receptor has seven transmembrane domains with an extracellular N-terminus and intracellular C-terminal tail. The receptor has two glycosylation sites, an unusually large extracellular loop with a sulfated tyrosine residue important for ligand recognition and binding.C3a receptor is expressed in cells of myeloid origin like neutrophils, macrophages and dendritic cells to name a few. It is also detected in astrocytes from inflamed brain, endothelial cells and activated human T cells. mRNA of C3a receptor is detected in lung, liver, kidney, brain heart, muscle and testis.