title: Structural Insights into the Activation of Human Relaxin Family Peptide Receptor 1 by Small-Molecule Agonists.
abstract: The GPCR relaxin family peptide receptor 1 (RXFP1) mediates the action of relaxin peptide hormone, including its tissue remodeling and antifibrotic effects. The peptide has a short half-life in plasma, limiting its therapeutic utility. However, small-molecule agonists of human RXFP1 can overcome this limitation and may provide a useful therapeutic approach, especially for chronic diseases such as heart failure and fibrosis. The first small-molecule agonists of RXFP1 were recently identified from a high-throughput screening, using a homogeneous cell-based cAMP assay. Optimization of the hit compounds resulted in a series of highly potent and RXFP1 selective agonists with low cytotoxicity, and excellent in vitro ADME and pharmacokinetic properties. Here, we undertook extensive site-directed mutagenesis studies in combination with computational modeling analysis to probe the molecular basis of the small-molecule binding to RXFP1. The results showed that the agonists bind to an allosteric site of RXFP1 in a manner that closely interacts with the seventh transmembrane domain (TM7) and the third extracellular loop (ECL3). Several residues were determined to play an important role in the agonist binding and receptor activation, including a hydrophobic region at TM7 consisting of W664, F668, and L670. The G659/T660 motif within ECL3 is crucial to the observed species selectivity of the agonists for RXFP1. The receptor binding and activation effects by the small molecule ML290 were compared with the cognate ligand, relaxin, providing valuable insights on the structural basis and molecular mechanism of receptor activation and selectivity for RXFP1.
authors: NIH Chemical Genomics Center, National Center for Advancing Translational Sciences, National Institutes of Health , 9800 Medical Center Drive, Rockville, Maryland 20850, United States.
authors: Xin
authors: X
authors: Hu
authors: Courtney
authors: C
authors: Myhr
authors: Zaohua
authors: Z
authors: Huang
authors: NIH Chemical Genomics Center, National Center for Advancing Translational Sciences, National Institutes of Health , 9800 Medical Center Drive, Rockville, Maryland 20850, United States.
authors: Jingbo
authors: J
authors: Xiao
authors: NIH Chemical Genomics Center, National Center for Advancing Translational Sciences, National Institutes of Health , 9800 Medical Center Drive, Rockville, Maryland 20850, United States.
authors: Elena
authors: E
authors: Barnaeva
authors: Brian A
authors: BA
authors: Ho
authors: Irina U
authors: IU
authors: Agoulnik
authors: NIH Chemical Genomics Center, National Center for Advancing Translational Sciences, National Institutes of Health , 9800 Medical Center Drive, Rockville, Maryland 20850, United States.
authors: Marc
authors: M
authors: Ferrer
authors: NIH Chemical Genomics Center, National Center for Advancing Translational Sciences, National Institutes of Health , 9800 Medical Center Drive, Rockville, Maryland 20850, United States.
authors: Juan J
authors: JJ
authors: Marugan
authors: NIH Chemical Genomics Center, National Center for Advancing Translational Sciences, National Institutes of Health , 9800 Medical Center Drive, Rockville, Maryland 20850, United States.
authors: Noel
authors: N
authors: Southall
authors: Alexander I
authors: AI
authors: Agoulnik
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D057809:HEK293 Cells; D006801:Humans; D008251:Macaca; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding / Q000502:physiology; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D051381:Rats; D043562:Receptors, G-Protein-Coupled / Q000819:agonists* / Q000737:chemistry / Q000378:metabolism*; D018000:Receptors, Peptide / Q000819:agonists* / Q000737:chemistry / Q000378:metabolism*; D012065:Relaxin / Q000378:metabolism* / Q000494:pharmacology; D013552:Swine
chemical_list: C417543:RXFP1 protein, human; D043562:Receptors, G-Protein-Coupled; D018000:Receptors, Peptide; D012065:Relaxin