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. 2015 Dec 9;172(24):5744–5869. doi: 10.1111/bph.13348
Nomenclature RXFP1 receptor RXFP2 receptor RXFP3 receptor RXFP4 receptor
HGNC, UniProt RXFP1, Q9HBX9 RXFP2, Q8WXD0 RXFP3, Q9NSD7 RXFP4, Q8TDU9
Rank order of potency relaxin (RLN2, P04090) = relaxin‐1 (RLN1, P04808) >relaxin‐3 (RLN3, Q8WXF3) [1812] INSL3 (INSL3, P51460) >relaxin (RLN2, P04090) ≫relaxin‐3 (RLN3, Q8WXF3) [1022, 1812] relaxin‐3 (RLN3, Q8WXF3) >relaxin‐3 (B chain) (RLN3, Q8WXF3) >relaxin (RLN2, P04090) [1119] INSL5 (INSL5, Q9Y5Q6) = relaxin‐3 (RLN3, Q8WXF3) >relaxin‐3 (B chain) (RLN3, Q8WXF3) [1117, 1118]
Endogenous antagonists – – INSL5 (INSL5, Q9Y5Q6) (pK i 7) [2129] –
Antagonists B‐R13/17K H2 relaxin (pEC50 5.7–6.7) [788, 1382], LGR7‐truncate [1687] – R3(BΔ23‐27)R/I5 chimeric peptide (pIC50 9.2) [1018] R3(BΔ23‐27)R/I5 chimeric peptide (pIC50 8–8.6) [714, 1018]
Selective antagonists – A(9‐26)INSL3 (pK i 9.1) [787], A(10‐24)INSL3 (pK i 8.7) [787], A(C10/15S)INSL3 (pK i 8.6) [2118], INSL3 B chain dimer analogue 8 (pK i 8.5) [1710], A(Δ10/15C)INSL3 (pK i 8.3) [2118], cyclic INSL3 B‐chain analogue 6 (pK i 6.7) [1708], INSL3 B‐chain analogue (pK i 5.1) [411], (des 1‐8) A‐chain INSL3 analogue [253] minimised relaxin‐3 analogue 3 (pK i 7.6) [1706], R3‐B1‐22R (pIC50 7.4) [714] minimised relaxin‐3 analogue 3 (pIC50 6.6) [1706]
Selective allosteric modulators ML290 (Agonist) (pEC50 7) [2057, 2060] – – –
Labelled ligands [33P]relaxin (human) (Agonist) (pK d 9.3–9.7) [678, 1812], [125I]relaxin (human) (Agonist) [125I]INSL3 (human) (Agonist) (pK d 10) [1340], [33P]relaxin (human) (Agonist) (pK d 9–9.2) [678, 1812] [125I]relaxin‐3 (human) (Agonist) (pK d 9.5) [1119], [125I]relaxin‐3‐B/INSL5 A chimera (Agonist) (pK d 9.3) [1117] [125I]relaxin‐3 (human) (Agonist) (pK d 8.7–9.7) [1118], [125I]relaxin‐3‐B/INSL5 A chimera (Agonist) (pK d 8.9) [1117], europium‐labelled INSL5 (pK d 8.3) [714]
Comments europium‐labelled relaxin is a fluorescent ligand for this receptor (K d=0.5nM) [1707]. europium‐labelled INSL3 is a fluorescent ligand for this receptor (K d=1nM) [1709]. europium‐labelled relaxin‐3‐B/INSL5 A chimera and R3‐B1‐22R are fluorescent ligands for this receptor (K d=5nM and 28nM) [714, 715]. europium‐labelled relaxin‐3‐B/INSL5 A chimera is a fluorescent probe at this receptor (K d=5nM) [714]. europium‐labelled mouse INSL5 is a fluorescent ligand at this receptor (K d=5nM) [120].