From Structure to Function: Development of Relaxin‐3 Analogs and their Role in RXFP3 Signaling

Relaxin‐3 is a two‐chain neuropeptide of the insulin/relaxin superfamily and the cognate ligand for the G protein‐coupled receptor RXFP3. Since its discovery, the relaxin‐3/RXFP3 signaling system has emerged as a key regulator of feeding behavior, stress responses, arousal, addiction, and cognitive function. Recent structural studies, including the first cryo‐electron microscopy structures of RXFP3 bound to relaxin‐3 and small molecules, have provided significant insights into ligand–receptor interactions. Together with mutagenesis and pharmacological studies, these advances have facilitated the design of diverse RXFP3 ligands, ranging from simplified and/or stapled single‐chain analogs of relaxin‐3 to grafted scaffolds and small‐molecule modulators. Such tools have been instrumental for probing relaxin‐3 biology in vivo and highlight the system's therapeutic potential for treating anxiety, depression, obesity, binge eating, and alcohol use disorder. However, challenges remain, particularly regarding blood–brain barrier penetration, receptor subtype selectivity, pharmacokinetic optimization, and safe long‐term modulation. This review summarizes current knowledge of relaxin‐3 structure, receptor interactions, and pharmacology and highlights how advances in peptide chemistry, structural biology, and small‐molecule design are enabling the rational development of RXFP3‐targeted therapeutics.

• Publication year

  2025

• Venue

  ChemBioChem

• Publication date

  2025-11-08

• Fields of study

  Medicine, Chemistry

• Identifiers
  DOI 10.1002/cbic.202500664PMID 41204779
• External record

  Open on Semantic Scholar

• Source metadata

  Semantic Scholar, PubMed

• No claims are published for this paper.

• No concepts are published for this paper.

• Molecular mechanism underlying non-discriminatory recognition of relaxin-3 by RXFP3 and RXFP4

  2025cited by this paper
• Development of Diphenyl-1,2,4-Oxadiazole Analogues as Allosteric Modulators of the RXFP3 Receptor: Evaluation of Importance of the N-Substituted-2-Pyrrolidone Moiety in RLX-33.

  2025cited by this paper
• Mechanisms of biased agonism by Gαi/o-biased stapled peptide agonists of the relaxin-3 receptor

  2024cited by this paper
• Localisation of the relaxin-family peptide 3 receptor to enteroendocrine cells of the intestine in RXFP3-Cre/tdTomato mice.

  2024cited by this paper
• Relaxin family peptide receptor 3 (RXFP3) expressing cells in the zona incerta/lateral hypothalamus augment behavioural arousal

  2024cited by this paper
• Efficient systemic CNS delivery of a therapeutic antisense oligonucleotide with a blood-brain barrier-penetrating ApoE-derived peptide.

  2024cited by this paper
• Accurate structure prediction of biomolecular interactions with AlphaFold 3

  2024cited by this paper
• Novel RXFP3 negative allosteric modulator RLX‐33 reduces alcohol self‐administration in rats

  2023cited by this paper
• Ligand recognition mechanism of the human relaxin family peptide receptor 4 (RXFP4)

  2023cited by this paper
• The blood–brain barrier: Structure, regulation and drug delivery

  2023cited by this paper
• Noncovalent Peptide Stapling Using Alpha-Methyl-l-Phenylalanine for α-Helical Peptidomimetics.

  2023cited by this paper
• Discovery and Characterization of the First Nonpeptide Antagonists for the Relaxin-3/RXFP3 System.

  2022cited by this paper
• Indole-Containing Amidinohydrazones as Nonpeptide, Dual RXFP3/4 Agonists: Synthesis, Structure-Activity Relationship, and Molecular Modeling Studies.

  2021cited by this paper
• High-Throughput Screening Campaign Identified a Potential Small Molecule RXFP3/4 Agonist

  2021cited by this paper
• Involvement of the Nucleus Incertus and Relaxin-3/RXFP3 Signaling System in Explicit and Implicit Memory

  2021cited by this paper
• Strategies for delivering therapeutics across the blood–brain barrier

  2021cited by this paper
• Mapping Cell Types and Efferent Pathways in the Ascending Relaxin-3 System of the Nucleus Incertus

  2020cited by this paper
• Effects of C-Terminal B-Chain Modifications in a Relaxin 3 Agonist Analogue.

  2020cited by this paper
• Exploring the Use of Helicogenic Amino Acids for Optimising Single Chain Relaxin-3 Peptide Agonists

  2020cited by this paper
• Development of Relaxin-3 Agonists and Antagonists Based on Grafted Disulfide-Stabilized Scaffolds

  2020cited by this paper
• High-throughput screening campaign identifies a small molecule agonist of the relaxin family peptide receptor 4

  2020cited by this paper
• RLN3/RXFP3 Signaling in the PVN Inhibits Magnocellular Neurons via M-like Current Activation and Contributes to Binge Eating Behavior

  2020cited by this paper
• Single chain peptide agonists of relaxin receptors.

  2019cited by this paper
• Intranasal administration of a stapled relaxin‐3 mimetic has anxiolytic‐ and antidepressant‐like activity in rats

  2019cited by this paper
• Discovery of a small molecule RXFP3/4 agonist that increases food intake in rats upon acute central administration.

  2019cited by this paper
• Distinct but overlapping binding sites of agonist and antagonist at the relaxin family peptide 3 (RXFP3) receptor

  2018cited by this paper
• Differential effects of relaxin-3 and a selective relaxin-3 receptor agonist on food and water intake and hypothalamic neuronal activity in rats.

  2018cited by this paper
• Binding conformation and determinants of a single-chain peptide antagonist at the relaxin-3 receptor RXFP3

  2018cited by this paper
• Distribution, physiology and pharmacology of relaxin‐3/RXFP3 systems in brain

  2017cited by this paper
• Relaxin‐3 inputs target hippocampal interneurons and deletion of hilar relaxin‐3 receptors in “floxed‐RXFP3” mice impairs spatial memory

  2017cited by this paper
• Relaxin family peptides: structure–activity relationship studies

  2017cited by this paper
• Development of a selective agonist for relaxin family peptide receptor 3

  2017cited by this paper
• Inhibition of oxytocin and vasopressin neuron activity in rat hypothalamic paraventricular nucleus by relaxin‐3–RXFP3 signalling

  2017cited by this paper
• Central amygdala relaxin‐3/relaxin family peptide receptor 3 signalling modulates alcohol seeking in rats

  2017cited by this paper
• Development of a Single-Chain Peptide Agonist of the Relaxin-3 Receptor Using Hydrocarbon Stapling.

  2016cited by this paper
• Comparative Distribution of Relaxin-3 Inputs and Calcium-Binding Protein-Positive Neurons in Rat Amygdala

  2016cited by this paper
• Role of relaxin-3/RXFP3 system in stress-induced binge-like eating in female rats.

  2016cited by this paper
• Stapled B chain analogues of relaxin‐3 retain biological activity

  2016cited by this paper
• Altered relaxin family receptors RXFP1 and RXFP3 in the neocortex of depressed Alzheimer’s disease patients

  2016cited by this paper
• Solution structure, aggregation behavior, and flexibility of human relaxin-2.

  2015cited by this paper
• Relaxin-3 Receptor (RXFP3) Signalling Mediates Stress-Related Alcohol Preference in Mice

  2015cited by this paper
• Synthesis and pharmacological characterization of a europium-labelled single-chain antagonist for binding studies of the relaxin-3 receptor RXFP3

  2015cited by this paper
• Relaxin-3 mRNA levels in nucleus incertus correlate with alcohol and sucrose intake in rats.

  2014cited by this paper
• Relaxin-3/RXFP3 networks: an emerging target for the treatment of depression and other neuropsychiatric diseases?

  2014cited by this paper
• Viral-mediated delivery of an RXFP3 agonist into brain promotes arousal in mice.

  2013cited by this paper
• Central relaxin-3 receptor (RXFP3) activation decreases anxiety- and depressive-like behaviours in the rat.

  2013cited by this paper
• Relaxin-3/RXFP3 Signaling and Neuroendocrine Function – A Perspective on Extrinsic Hypothalamic Control

  2013cited by this paper
• Elucidation of relaxin-3 binding interactions in the extracellular loops of RXFP3

  2013cited by this paper
• Relaxin-3/RXFP3 system regulates alcohol-seeking

  2013cited by this paper
• Relaxin‐3 innervation of the intergeniculate leaflet of the rat thalamus – neuronal tract‐tracing and in vitro electrophysiological studies

  2013cited by this paper
• Minimization of human relaxin-3 leading to high-affinity analogues with increased selectivity for relaxin-family peptide 3 receptor (RXFP3) over RXFP1.

  2012cited by this paper
• Relaxin‐3 null mutation mice display a circadian hypoactivity phenotype

  2012cited by this paper
• Modulation of feeding by chronic rAAV expression of a relaxin-3 peptide agonist in rat hypothalamus

  2012cited by this paper
• Relaxin-3 systems in the brain--the first 10 years.

  2011cited by this paper
• Relaxin-3/INSL7 Regulates the Stress-response System in the Rat Hypothalamus

  2011cited by this paper
• Design, synthesis, and characterization of a single-chain peptide antagonist for the relaxin-3 receptor RXFP3.

  2011cited by this paper
• Distribution of relaxin‐3 and RXFP3 within arousal, stress, affective, and cognitive circuits of mouse brain

  2010cited by this paper
• Swim stress excitation of nucleus incertus and rapid induction of relaxin-3 expression via CRF1 activation.

  2010cited by this paper
• Regulation of relaxin 3 gene expression via cAMP‐PKA in a neuroblastoma cell line

  2009cited by this paper
• Modulation of hippocampal theta oscillations and spatial memory by relaxin-3 neurons of the nucleus incertus.

  2009cited by this paper
• The human insulin superfamily of polypeptide hormones.

  2009cited by this paper
• RELAXIN AND RELATED PEPTIDES: FIFTH INTERNATIONAL CONFERENCE Probing the Functional Domains of Relaxin-3 and the Creation of a Selective Antagonist for RXFP3/GPCR135 over Relaxin Receptor RXFP1/LGR7

  2009cited by this paper
• Localization of relaxin‐3 in brain of Macaca fascicularis: Identification of a nucleus incertus in primate

  2009cited by this paper
• Structure of human insulin-like peptide 5 and characterization of conserved hydrogen bonds and electrostatic interactions within the relaxin framework.

  2009cited by this paper
• The A-chain of Human Relaxin Family Peptides Has Distinct Roles in the Binding and Activation of the Different Relaxin Family Peptide Receptors*

  2008cited by this paper
• Structure of the R3/I5 Chimeric Relaxin Peptide, a Selective GPCR135 and GPCR142 Agonist*

  2008cited by this paper
• Relaxin-3 in GABA projection neurons of nucleus incertus suggests widespread influence on forebrain circuits via G-protein-coupled receptor-135 in the rat.

  2007cited by this paper
• The Relaxin Family Peptide Receptor 3 Activates Extracellular Signal-Regulated Kinase 1/2 through a Protein Kinase C-Dependent Mechanism

  2007cited by this paper
• R3(BDelta23 27)R/I5 chimeric peptide, a selective antagonist for GPCR135 and GPCR142 over relaxin receptor LGR7: in vitro and in vivo characterization.

  2007cited by this paper
• Relaxin-3: improved synthesis strategy and demonstration of its high-affinity interaction with the relaxin receptor LGR7 both in vitro and in vivo.

  2006cited by this paper
• Solution Structure and Characterization of the LGR8 Receptor Binding Surface of Insulin-like Peptide 3*

  2006cited by this paper
• Solution Structure and Novel Insights into the Determinants of the Receptor Specificity of Human Relaxin-3*

  2006cited by this paper
• Chronic Intracerebroventricular Administration of Relaxin-3 Increases Body Weight in Rats

  2006cited by this paper
• Central relaxin-3 administration causes hyperphagia in male Wistar rats.

  2005cited by this paper
• INSL5 Is a High Affinity Specific Agonist for GPCR142 (GPR100)*

  2005cited by this paper
• Relaxin-3/Insulin-Like Peptide 5 Chimeric Peptide, a Selective Ligand for G Protein-Coupled Receptor (GPCR)135 and GPCR142 over Leucine-Rich Repeat-Containing G Protein-Coupled Receptor 7

  2005cited by this paper
• Neurons expressing relaxin 3/INSL 7 in the nucleus incertus respond to stress

  2005cited by this paper
• Evolution of the Signaling System in Relaxin‐Family Peptides

  2005cited by this paper
• Evolution of the relaxin-like peptide family

  2005cited by this paper
• Identification of Relaxin-3/INSL7 as an Endogenous Ligand for the Orphan G-protein-coupled Receptor GPCR135*

  2003cited by this paper
• Human gene 2 relaxin chain combination and folding.

  2003cited by this paper
• H3 Relaxin Is a Specific Ligand for LGR7 and Activates the Receptor by Interacting with Both the Ectodomain and the Exoloop 2*

  2003cited by this paper
• Identification of Relaxin-3/INSL7 as a Ligand for GPCR142*

  2003cited by this paper
• Human Relaxin Gene 3 (H3) and the Equivalent Mouse Relaxin (M3) Gene

  2002cited by this paper
• Restricted, but abundant, expression of the novel rat gene‐3 (R3) relaxin in the dorsal tegmental region of brain

  2002cited by this paper
• The Relaxin Receptor-binding Site Geometry Suggests a Novel Gripping Mode of Interaction*

  2000cited by this paper
• The three subfamilies of leucine-rich repeat-containing G protein-coupled receptors (LGR): identification of LGR6 and LGR7 and the signaling mechanism for LGR7.

  2000cited by this paper
• A novel complex of a phenolic derivative with insulin: Structural features related to the T → R transition

  1996cited by this paper
• The receptor-binding site of human relaxin II. A dual prong-binding mechanism.

  1992cited by this paper
• The Chemistry of Imines.

  1963cited by this paper
• A c c ep t ed M anu sc r i p t

  year unknowncited by this paper

• No citing papers are available for this paper.