Relaxin family peptide receptors

Unless otherwise stated all data on this page refer to the human proteins. Gene information is provided for human (Hs), mouse (Mm) and rat (Rn).


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Relaxin family peptide receptors (RXFP, nomenclature as recommended by the NC-IUPHAR committee on relaxin family peptide receptors, [1]) may be divided into two pairs, RXFP1/2 and RXFP3/4. Endogenous agonists at these receptors are a number of heterodimeric peptide hormones analogous to insulin: H1 relaxin (RLN1, P04808), H2 relaxin (RLN2, P04090), H3 relaxin (RLN3, Q8WXF3) (also known as INSL7), insulin-like peptide 3 (INSL3 (INSL3, P51460)) and INSL5 (INSL5, Q9Y5Q6).

Species homologues of relaxin have distinct pharmacology – H2 relaxin (RLN2, P04090) interacts with RXFP1, RXFP2 and RXFP3, whereas mouse and rat relaxin selectively bind to and activate RXFP1 [28] and porcine relaxin may have a higher efficacy than H2 relaxin (RLN2, P04090) [8]. H3 relaxin (RLN3, Q8WXF3) has differential affinity for RXFP2 receptors between species; mouse and rat RXFP2 have a higher affinity for H3 relaxin (RLN3, Q8WXF3) [27]. At least two binding sites have been identified on the RXFP1 and RXFP2 receptors: a high-affinity site in the leucine-rich repeat region of the ectodomain and a somewhat lower-affinity site located in the surface loops of the transmembrane domain [8,35]. The unique N-terminal LDLa module of RXFP1 and RXFP2 is essential for receptor signalling [29].


RXFP1 receptor Show summary » More detailed page

RXFP2 receptor Show summary » More detailed page

RXFP3 receptor Show summary » More detailed page

RXFP4 receptor Show summary » More detailed page


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Further reading

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NC-IUPHAR subcommittee and family contributors

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How to cite this family page

Database page citation:

Relaxin family peptide receptors. Accessed on 23/09/2014. IUPHAR/BPS Guide to PHARMACOLOGY,

Concise Guide to PHARMACOLOGY citation:

Alexander SPH, Benson HE, Faccenda E, Pawson AJ, Sharman JL, Spedding M, Peters JA and Harmar AJ, CGTP Collaborators. (2013) The Concise Guide to PHARMACOLOGY 2013/14: G Protein-Coupled Receptors. Br J Pharmacol. 170: 1459–1581.