Use of Synthetic Sequences of the Nicotinic Acetylcholine Receptor to Identify Structural Determinants of Binding Sites for Neurotoxins and Antibodies to the Main Immunogenic Region

Abstract

Synthetic peptide sequences of the nicotinic acetylcholine receptor (AChR) have been used extensively to identify structural features of two functionally important domains of the AChR: the binding site for cholinergic ligands and the main immunogenic region (MIR) (i.e., the set of overlapping epitopes that dominates the antibody response in the autoimmune disease myasthenia gravis) studies that used synthetic peptides have identified sequence regions and individual residues likely to contribute to formation of those domains. The results of several synthetic peptide investigations have been verified by different approaches, such as affinity labeling and study of AChRs carrying mutations of particular residues. Therefore, at least for certain protein ligands, the use of synthetic peptide sequences as representative structural elements of the corresponding receptor has demonstrated a reliable predictive value. Synthetic peptide studies enable, in a relatively short time, identification of candidate sequence regions for contributing to the structure of binding domains involved in protein/protein interaction. They serve as a foundation to direct the focus of more labor-intensive studies involving receptors mutated at individual residues to investigate their binding properties. We describe here the different types of assays employed in our laboratory using synthetic peptide strategies to investigate the AChR sequence regions contributing to the MIR and to cholinergic binding sites. The results obtained are summarized and critically compared and contrasted with those of other approaches. The reliability of the conclusions drawn from the aggregated results of those studies is discussed.