Mechanism of interactions between α-conotoxin RegIIA and carbohydrates at the human α3β4 nicotinic acetylcholine receptor

Abstract

Conotoxins are marine peptide toxins from marine cone snails. The α-conotoxin RegIIA can selectively act on human (h) α3β4 nicotinic acetylcholine receptor (nAChR), and is an important lead for drug development. The high-resolution cryo-electron microscopy structure of the α3β4 nAChR demonstrates several carbohydrates are located near the orthosteric binding sites, which may affect α-conotoxin binding. Oligosaccharide chains can modify the physical and chemical properties of proteins by changing the conformation, hydrophobicity, quality and size of the protein. The purpose of this study is to explore the effect of oligosaccharide chains on the binding modes and activities of RegIIA and its derivatives at hα3β4 nAChRs. Through computational simulations, we designed and synthesized RegIIA mutants at position 14 to explore the importance of residue H14 to the activity of the peptide. Molecular dynamics simulations suggest that the oligosaccharide chains affect the binding of RegIIA at the hα3β4 nAChR through direct interactions with H14 and by affecting the C-loop conformation of the binding sites. Electrophysiology studies on H14 analogues suggest that in addition to forming direct interactions with the carbohydrates, the residue might play an important role in maintaining the conformation of the peptide. Overall, this study further clarifies the structure–activity relationship of α-conotoxin RegIIA at the hα3β4 nAChR and, also provides important experimental and theoretical basis for the development of new peptide drugs.

Conus regius-Derived Conotoxins: Novel Therapeutic Opportunities from a Marine Organism

“…Specifically, two mutations, [T59K]α3β2 and [S113R]α3β2, strongly enhanced the α-conotoxin affinity compared with wild-type α3β2, whereas opposite point mutations in α3β4 exerted the contrary effect [98]. Moreover, a recent study showed that oligosaccharide chains on hα3β4 nAChR are crucial for interaction with RegIIA and that His14 plays an important role for the structure-activity relationship of this conotoxin [100].…”

Fluorescently Labeled α-Conotoxin TxID, a New Probe for α3β4 Neuronal Nicotinic Acetylcholine Receptors

“…Conotoxins can specifically act on ion channels and receptors, so they can be used as an important tool for neurophysiological and pharmacological research [ 24 ]. This family of α-CTx generally belongs to superfamily A, which is generally composed of 6–20 amino acids with two disulfide bonds, and most of the C-terminal amino acids are amidated [ 25 , 26 ]. As selective antagonists of a variety of neural and muscle nAChR subtypes, the α-CTxs have the characteristics of strong selectivity, stable structure, and low side effects [ 21 , 27 , 28 ].…”