School of Natural Sciences, Linnaeus University, SE-391 82 Kalmar, Sweden.
J Am Chem Soc. 2011 Apr 6;133(13):4965-74. doi: 10.1021/ja110567j. Epub 2011 Mar 8.
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.
松弛素-3 是一种二硫键丰富的两链肽，是松弛素肽家族的原始成员，与 G 蛋白偶联受体 RXFP3 一起在大脑中高度表达。松弛素-3 的强烈进化保守性表明其具有关键的生物学功能，最近的研究表明它可以调节感觉、神经内分泌、代谢和认知系统。然而，由于缺乏对 RXFP3 具有高亲和力的拮抗剂，中枢松弛素-3-RXFP3 信号的详细研究至今受到严重阻碍。以前的研究使用了一种复杂的二链嵌合松弛素肽 R3(BΔ23-27)R/I5，其中包含一个带有额外 C 末端 Arg 残基的截断松弛素-3 B 链与胰岛素样肽 5（INSL5）A 链结合。在这项研究中，我们证明通过用 Ser 替换该截断松弛素-3 B 链中的天然 Cys，可以实现保留对 RXFP3 高亲和力拮抗作用的 23 个氨基酸的单链线性肽。体内研究表明，这种肽 R3 B1-22R 可以拮抗脑室内注射后松弛素-3/RXFP3 诱导的大鼠摄食增加。因此，R3 B1-22R 代表了研究松弛素药理学的极好工具，也是开发用于临床的合成上易于处理的单链 RXFP3 调节剂的先导分子。
