Functional characteristics of a variant thyrotropin receptor.
A claim has been made that a variant of the human thyrotropin receptor in which Pro52 is replaced by Thr ([Thr52]thyrotropin receptor) is associated with autoimmune thyroid diseases and displays increased responsiveness to thyrotropin. We have analysed the functional characteristics of this variant receptor. Equivalent numbers of of the wild type and of the variant thyrotropin receptor, measured both by 125I-thyrotropin binding and by flow cytofluorimetry, were transiently expressed in COS-7 cells. Under these conditions, the two receptors showed the same degree of constitutive activity for the cAMP pathway, the same affinity for bovine thyrotropin, and a virtually identical responsiveness to bovine thyrotropin for activation of both the cAMP and inositol-phosphate regulatory pathways. Our results show that the [Thr52]thyrotropin receptor variant of the human thyrotropin receptor, which is present in the 12% of the population, does not affect receptor function and represents most likely a simple polymorphism.
Tonacchera
M
M
Institut de Recherche Interdisciplinaire, Faculté de Médicine, Université Libre de Bruxelles, Belgium.
Cetani
F
F
Costagliola
S
S
Van Sande
J
J
Refetoff
S
S
Vassart
G
G
D000483:Alleles; D000818:Animals; D002417:Cattle; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D009154:Mutation; D010716:Phosphatidylinositols / Q000378:metabolism; D011110:Polymorphism, Genetic; D011989:Receptors, Thyrotropin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013972:Thyrotropin / Q000378:metabolism*; D014162:Transfection
D007295:Inositol Phosphates; D010716:Phosphatidylinositols; D011989:Receptors, Thyrotropin; D013972:Thyrotropin; D000242:Cyclic AMP