Effect of solubilization of porcine thyrotropin (TSH) receptor on TSH binding and on radio-receptor assay for anti-TSH receptor antibodies.
The effect of solubilization of porcine thyrotropin receptor (TSHR) on TSH binding and on the radio-receptor assay for anti-TSHR antibodies was examined. After TSHR solubilization with 1% dodecylpolyethy-leneglycoether, TSH binding affinity was increased, from Kd = 1.15 nM to 0.45 nM, and TSH binding capacity was slightly increased, from 0.15 nM to 0.19 nM. With a particulate membrane suspension from thyroid cells, blocking of TSH binding to the membrane suspension by anti-thyrotropin receptor antibody was observed only for thyroid stimulation blocking antibody (TSBAb), not for thyroid-stimulating antibody (TSAb). After the solubilization of TSHR, both TSBAb and TSAb blocked TSH-binding to the solubilized TSHR. We speculate that TSAb interacts with the TSHR in the native conformation without interfering with TSH binding, and that after the solubilization, any anti-TSHR antibody interferes with TSH-binding due to the conformational change in TSHR. With these particulate thyroid cell membrane preparations, we can detect only TSBAb by the radio-receptor assay.
Watanabe
Y
Y
Department of Laboratory Medicine, Osaka University Medical School, Suita, Japan.
Tada
H
H
Hidaka
Y
Y
Takano
T
T
Amino
N
N
D000818:Animals; D001323:Autoantibodies / Q000097:blood*; D001327:Autoimmune Diseases / Q000276:immunology; D001681:Biological Assay; D006801:Humans; D018828:Immunoglobulins, Thyroid-Stimulating; D011869:Radioligand Assay; D011989:Receptors, Thyrotropin / Q000097:blood* / Q000737:chemistry / Q000378:metabolism*; D012995:Solubility; D013552:Swine; D013959:Thyroid Diseases / Q000276:immunology; D013972:Thyrotropin / Q000378:metabolism*
D001323:Autoantibodies; D018828:Immunoglobulins, Thyroid-Stimulating; D011989:Receptors, Thyrotropin; C094372:thyrotropin-binding inhibitory immunoglobulin; D013972:Thyrotropin