Urotensin-II peptidomimetic incorporating a non-reducible 1,5-triazole disulfide bond reveals a pseudo-irreversible covalent binding mechanism to the urotensin G-protein coupled receptor

作者：Pacifico Salvatore; Kerckhoffs Aidan; Fallow Andrew J; Foreman Rachel E; Guerrini Remo; McDonald John; Lambert David G^*; Jamieson Andrew G^*

来源：Organic and Biomolecular Chemistry, 2017, 15(21): 4704-4710.

DOI：10.1039/c7ob00959c

The urotensin-II receptor (UTR) is a class A GPCR that predominantly binds to the pleiotropic cyclic peptide urotensin-II (U-II). U-II is constrained by a disulfide bridge that induces a a-turn structure and binds pseudo-irreversibly to UTR and is believed to result in a structural rearrangement of the receptor. However, it is not well understood how U-II binds pseudo-irreversibly and the nature of the reorganization of the receptor that results in G-protein activation. Here we describe a series of U-II peptidomimetics incorporating a non-reducible disulfide bond structural surrogate to investigate the feasibility that native U-II binds to the G protein-coupled receptor through disulfide bond shuffling as a mechanism of covalent interaction. Disubstituted 1,2,3-triazoles were designed with the aid of computational modeling as a non-reducible mimic of the disulfide bridge (Cys5-Cys10) in U-II. Solid phase synthesis using CuAAC or RuAAC as the key macrocyclisation step provided four analogues of U-II(4-11) incorporating either a 1,5-triazole bridge (5, 6) or 1,4-triazole bridge (9, 10). Biological evaluation of compounds 5, 6, 9 and 10 was achieved using in vitro [I-125] UII binding and [Ca2+](i) assays at recombinant human UTR. Compounds 5 and 6 demonstrated high affinity (K-D similar to 10 nM) for the UTR and were also shown to bind reversibly as predicted and activate the UTR to increase [Ca2+](i). Importantly, our results provide new insight into the mechanism of covalent binding of U-II with the UTR.

• 出版日期2017-6-7