Function of hyperekplexia-causing α1R271Q/L glycine receptors is restored by shifting the affected residue out of the allosteric signalling pathway

Abstract

BACKGROUND AND PURPOSE Glycine receptor α1 subunit R271Q and R271L (α1R271Q/L) mutations cause the neuromotor disorder, hereditary hyperekplexia. Studies suggest that the 271 residue is located within the allosteric signalling pathway linking the agonist binding site to the channel gate. The present study aimed to investigate a possible mechanism for restoring the function of the α1R271Q/L glycine receptor. EXPERIMENTAL APPROACH A 12-amino-acid segment incorporating the 271 residue on the glycine receptor α1271Q/L subunit was replaced by the homologous segment from the glycine receptor β subunit (α1(Ch) 271Q/L). The function of the α1(Ch) 271Q/L glycine receptor was examined by whole-cell patch-clamp recording and voltage-clamp fluorometry techniques. KEY RESULTS The function of the α1(Ch) 271Q/L glycine receptor was restored to the level of the wild-type (WT) α1 glycine receptor. Moreover, in the α1(Ch) glycine receptor, in contrast to the α1 glycine receptor, the channel function was not sensitive to various substitutions of the 271 residue, and the conformational change in the vicinity of the 271 residue was uncoupled from the channel gating. CONCLUSIONS AND IMPLICATIONS The 271 residue is shifted out of the allosteric signalling pathway in the α1(Ch) glycine receptor. We propose that this mechanism provides a novel drug design strategy not only for glycine receptor α1R271Q/L-caused hereditary hyperekplexia, but also for any pathological condition that is caused by missense mutation- or covalent modification-induced disorders involving residues in allosteric signalling pathways. Such a strategy makes it possible to design an ideal drug, which only corrects the function of the mutant or modified protein without affecting the WT or naive protein.