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 agreed by the NC-IUPHAR Subcommittee on Relaxin family peptide receptors [1,13]) 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: relaxin-1 (RLN1, P04808), relaxin (RLN2, P04090), relaxin-3 (RLN3, Q8WXF3) (also known as INSL7), insulin-like peptide 3 (INSL3 (INSL3, P51460)) and INSL5 (INSL5, Q9Y5Q6).

Species homologues of relaxin have distinct pharmacology – relaxin (RLN2, P04090) interacts with RXFP1, RXFP2 and RXFP3, whereas mouse and rat relaxin selectively bind to and activate RXFP1 [40] and porcine relaxin may have a higher efficacy than human relaxin (RLN2, P04090) [14]. Relaxin-3 (RLN3, Q8WXF3) has differential affinity for RXFP2 receptors between species; mouse and rat RXFP2 have a higher affinity for relaxin-3 (RLN3, Q8WXF3) [39]. 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 [14,51]. The unique N-terminal LDLa module of RXFP1 and RXFP2 is essential for receptor signalling [41].


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:

Roger Summers, Ross Bathgate, Thomas Dschietzig, Michelle Halls, Richard Ivell, Barbara Sanborn, David Sherwood, Steve Sutton. Relaxin family peptide receptors. Accessed on 24/05/2016. IUPHAR/BPS Guide to PHARMACOLOGY,

Concise Guide to PHARMACOLOGY citation:

Alexander SPH, Davenport AP, Kelly E, Marrion N, Peters JA, Benson HE, Faccenda E, Pawson AJ, Sharman JL, Southan C, Davies JA and CGTP Collaborators (2015) The Concise Guide to PHARMACOLOGY 2015/16: G protein-coupled receptors. Br J Pharmacol. 172: 5744-5869.