Studies of Calmodulin-Like Portion in the TSH Receptor
Calmodulin (CaM) antagonists, such as W–7, W–5 chlorpromazine, and haloperidol, inhibited dose-dependently 125I–bTSH binding to its receptor. This inhibitory effect by CaM antagonist was diminished by the addition of EDTA. Not only anti–CaM antibody but also CaM inhibited dose–dependently 1251–bTSH binding to its receptor. These results may indicate the presence of a CaM–like structure in the membrane receptor for TSH.
Four sera out of 300 patients with Graves’ disease had increased CaM binding activities as compared to normal control subjects. The binding could be demonstrated as the autoantibody to CaM by double antibody method, polyethyleneglycol method, and also gel–filtration. Three antibodies were monoclonal and one was polyclonal immunoglobulins (IgG and/or IgA).
Although the incidence of the autoantibody to CaM in Graves’ disease is low and the pathologiccal significance of the autoantibody to CaM remains obscure, the existence of this antibody in the serum of patients may suggest the production of antibody to a CaM–like structure in the TSH receptor.
KeywordsSubacute Thyroiditis Thyroid Receptor Polyclonal Immunoglobulin Thyroid Plasma Membrane Light Chain Type
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