D-Amino Acid Substitution of ?-Conotoxin RgIA Identifies its Critical Residues and Improves the Enzymatic Stability.

ABSTRACT: ?-Conotoxin RgIA is a selective and potent competitive antagonist of rat ?9?10 nicotinic acetylcholine receptors (nAChR), but it is much less potent towards human ?9?10 nAChR. Furthermore, RgIA is susceptible to proteolytic degradation due to containing four arginine residues. These disadvantages greatly limit its use for clinical applications. The purpose of this research was to identify critical stereocenters of RgIA and discover more stable analogues, enhancing its bioavailability by using the d-amino acid scan method. The activity of each variant was investigated against rat and human ?9?10 nAChRs, which were expressed in Xenopus oocytes. Experimental assays showed that 14 out of 15 analogues had a substantial reduction in potency towards rat ?9?10 nAChR. Noticeably, analogue 13 retained full biological activity compared with RgIA. Meanwhile, two other analogues, 14 and 15, of which l-Args were substituted with d-Args, exhibited a significantly increased potency towards human ?9?10 nAChR, although these analogues showed decreased activities against rat ?9?10 nAChR. Additionally, these three analogues exhibited a high resistance against enzymatic degradation in human serum and simulated intestinal fluid (SIF). Collectively, our findings suggest that a d-amino acid scan is a useful strategy for investigating how the side-chain chirality of amino acids affects the structure and function of peptides and may facilitate the development of more stable analogues to increase therapeutic potential.

SUBMITTER: Ren J 

PROVIDER: S-EPMC6472032 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature