The RXFP4 receptor belongs to the Relaxin Family Peptide Receptors family. It was originally cloned as orphan receptor GPR100 and GPR142 but subsequently has been shown to be the physiological target for INSL3 (insulin-like peptide 3); it also responds to relaxin-3 at high affinity. Human RXFP4 is expressed in heart, skeletal muscle, kidney, liver and placenta and has been shown to be Gi-coupled. This cell line couples via Ga16 to the calcium pathway. Although to our knowledge RXFP4 has yet to be used as a drug discovery target, this cell line will provide utility for counter-screening compounds targeted to other members of this family that may have therapeutic utility for a wide range of diseases including cardiac and renal failure (RXFP1), asthma (RXFP1), scleroderma (RXFP1), infertility and contraception (RXFP2), anti-anxiety and anti-obesity (RXFP3).