Immunological and functional properties of the acetylcholine receptor expressed on the human cell line TE671.
In the first part of the present study we compared the antigenicity of affinity-purified acetylcholine receptors from the cell line TE671 and from human skeletal muscle. The reactivities of the two acetylcholine receptor preparations showed a strong correlation (r = 0.96) in a radioimmunoassay using sera from myasthenia gravis patients. In additional functional studies, carbamylcholine stimulated cAMP production in TE671 cells to 130%. This increase was even more pronounced when TE671 cells were grown in the presence of dexamethasone. alpha-Bungarotoxin completely blocked this carbamylcholine-induced cAMP increase. Using the Ca2+ indicator, indo-1, it was shown that intracellular Ca2+ concentrations ([Ca2+]i) were elevated in TE671 cells after stimulation with carbamylcholine. This effect was also completely blocked by alpha-bungarotoxin. To test the functional activity of autoantibodies against the acetylcholine receptor, TE671 cells were preincubated with sera from myasthenia gravis patients. In one third of sera a significant inhibition of the agonist-stimulated [Ca2+]i increase was detected, possibly caused by antibodies directed to functionally important areas of the acetylcholine receptor. There was no correlation between the inhibition rate of [Ca2+]i and anti-acetylcholine receptor antibody titres in these patient sera.
Stuhlmüller
B
B
Institut für Klinische Immunologie und Rheumatologie, Universität Erlangen-Nürnberg, Germany.
Kalden
J R
JR
Fahlbusch
R
R
Hain
N
N
Manger
B
B
D001323:Autoantibodies / Q000494:pharmacology / Q000502:physiology; D002038:Bungarotoxins / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002217:Carbachol / Q000494:pharmacology; D002352:Carrier Proteins / Q000032:analysis; D002478:Cells, Cultured; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D000242:Cyclic AMP / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D009132:Muscles / Q000276:immunology / Q000378:metabolism*; D009157:Myasthenia Gravis / Q000276:immunology / Q000378:metabolism*; D009447:Neuroblastoma / Q000378:metabolism*; D011863:Radioimmunoassay; D011950:Receptors, Cholinergic / Q000276:immunology / Q000302:isolation & purification / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D014407:Tumor Cells, Cultured
D001323:Autoantibodies; D002038:Bungarotoxins; D002352:Carrier Proteins; D011950:Receptors, Cholinergic; D002217:Carbachol; D000242:Cyclic AMP; D002118:Calcium