title: Myasthenogenicity of human acetylcholine receptor synthetic alpha-subunit peptide 125-147 does not require intramolecular disulfide cyclization.
abstract: This study reports the synthesis of a disulfide-looped peptide corresponding to residues 125-147 (Cys 128-Cys 142) of the nicotinic acetylcholine receptor (AChR) of human skeletal muscle, H alpha 125-147 (Lys-Ser-Tyr-Cys-Glu-Ile-Ile-Val-Thr-His-Phe-Pro-Phe-Asp-Glu-Gln- Asn-Cys-Ser-Nle-Lys Leu-Gly), and a nondisulfide-looped analogue, H alpha 125-147(S) (Lys-Ser-Tyr-Ser-Glu-Ile-Ile-Val-Thr-His-Phe-Pro-Phe-Asp-Glu- Gln-Asn-Cys-Ser-Nle-Lys-Leu-Gly), in which the amino acid Cys 128 was replaced with serine. Both peptides induced antigen-specific helper T cell responses, as evidenced in vitro by lymph node cell proliferation and in vivo by production of anti-AChR antibodies. Rats immunized with 100 micrograms of either synthetic peptide, without conjugation to a carrier, produced anti-peptide antibodies which bound to native AChR in immunoprecipitation assays and induced modulation of membrane-bound AChR from cultured human myotubes. Both peptides also induced electrophysiologic and biochemical signs of experimental autoimmune myasthenia gravis. Thus, region 125-147 of the AChR alpha-subunit is at least partly exposed extracellularly in human muscle and contains one or more autoantigenic sites capable of stimulating T cells and B cells. Disulfide-linkage between residues Cys 128 and Cys 142 is not essential for myasthenogenicity.
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000276:immunology; D004220:Disulfides; D006801:Humans; D007152:Immunologic Capping; D008213:Lymphocyte Activation; D009132:Muscles / Q000276:immunology*; D009157:Myasthenia Gravis / Q000276:immunology*; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000276:immunology; D011487:Protein Conformation; D051381:Rats; D011978:Receptors, Nicotinic / Q000276:immunology*; D013329:Structure-Activity Relationship; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D000954:Antigens, Surface; D004220:Disulfides; D010446:Peptide Fragments; D011978:Receptors, Nicotinic