Design, Synthesis, and Characterization of a Single-Chain Peptide Antagonist for the Relaxin-3 Receptor RXFP3

• Published in: Journal of the American Chemical Society 2011-04, Vol.133 (13), p.4965-4974
• Main Authors: Haugaard-Kedström, Linda M, Shabanpoor, Fazel, Hossain, Mohammed Akhter, Clark, Richard J, Ryan, Philip J, Craik, David J, Gundlach, Andrew L, Wade, John D, Bathgate, Ross A. D, Rosengren, K. Johan
• Format: Article
• Language: English
• Subjects: Animals; Biochemistry; Biokemi; Cell Line; CHO Cells; Cricetinae; Cricetulus; Humans; Ligands; Male; Models, Molecular; Rats; Rats, Sprague-Dawley; Receptors, G-Protein-Coupled - antagonists & inhibitors; Receptors, G-Protein-Coupled - chemistry; Relaxin - analogs & derivatives; Relaxin - chemistry; Relaxin - pharmacology; Structure-Activity Relationship
• ISSN: 0002-7863; 1520-5126; 1520-5126
• DOI: 10.1021/ja110567j

Relaxin-3 is a two-chain disulfide-rich peptide that is the ancestral member of the relaxin peptide family and, together with its G protein-coupled receptor RXFP3, is highly expressed in the brain. Strong evolutionary conservation of relaxin-3 suggests a critical biological function and recent studies have demonstrated modulation of sensory, neuroendocrine, metabolic, and cognitive systems. However, detailed studies of central relaxin-3-RXFP3 signaling have until now been severely hampered by the lack of a readily available high-affinity antagonist for RXFP3. Previous studies have utilized a complex two-chain chimeric relaxin peptide, R3(BΔ23−27)R/I5, in which a truncated relaxin-3 B-chain carrying an additional C-terminal Arg residue was combined with the insulin-like peptide 5 (INSL5) A-chain. In this study we demonstrate that, by replacing the native Cys in this truncated relaxin-3 B-chain with Ser, a single-chain linear peptide of 23 amino acids that retains high-affinity antagonism for RXFP3 can be achieved. In vivo studies demonstrate that this peptide, R3 B1−22R, antagonized relaxin-3/RXFP3 induced increases in feeding in rats after intracerebroventricular injection. Thus, R3 B1−22R represents an excellent tool for biological studies probing relaxin pharmacology and a lead molecule for the development of synthetically tractable, single-chain RXFP3 modulators for clinical use.