Presence of a putative steroidal allosteric site on glycoprotein hormone receptors.
In a previous work we found that the insecticide 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT), inhibits the accumulation of cAMP as induced by the bovine thyroid stimulating hormone (bTSH) in cells transfected with the TSH receptor. In this work, we demonstrate that the DDT molecular analogues, diethylstilbestrol and quercetine, are more potent inhibitors of the TSH receptor activity than DDT itself. The notion that all these compounds interfere with nuclear estrogen receptors, as either agonists (DDT and diethylstilbestrol) or antagonists (quercetin), prompted us to test the ability of the steroid hormone 17-beta-estradiol to inhibit the TSH receptor activity. We found that estrogen exposure causes a modest but significant inhibition of the bTSH induced cAMP accumulation both in transfected CHO-TSH receptor and Fischer Rat Thyroid Low Serum 5% (FRTL-5) cells. When applied to CHO cells transfected with the luteinizing hormone receptor, 17-beta-estradiol proved capable of inhibiting the hCG induced cAMP accumulation at a concentration as low as 10nM, though the effect was not greater than 35%. The effect of 17-beta-estradiol was not estrogen receptors mediated, as co-transfection of the estrogen receptor alpha and beta subunits with LH receptor caused cAMP to increase above the level attained by the sole hCG stimulation, and not to decrease it as expected. These data suggest the presence of a steroidal-like allosteric binding site on glycoprotein hormone receptors.
Rossi
Mario
M
Department of Neuroscience, University of Pisa, Pisa, Italy. roberto.maggio@univaq.it
Dimida
Antonio
A
Ferrarini
Eleonora
E
Silvano
Elena
E
De Marco
Giuseppina
G
Agretti
Patrizia
P
Aloisi
Gabriella
G
Simoncini
Tommaso
T
Di Bari
Lorenzo
L
Tonacchera
Massimo
M
Giorgi
Franco
F
Maggio
Roberto
R
D000262:Adenylyl Cyclases / Q000235:genetics; D000495:Allosteric Site; D000818:Animals; D016466:CHO Cells; D019556:COS Cells; D002460:Cell Line; D002522:Chlorocebus aethiops; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D006224:Cricetinae; D003412:Cricetulus; D000242:Cyclic AMP / Q000096:biosynthesis; D003634:DDT / Q000031:analogs & derivatives* / Q000494:pharmacology; D004054:Diethylstilbestrol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical / Q000379:methods; D004958:Estradiol / Q000494:pharmacology; D004967:Estrogens / Q000494:pharmacology; D007527:Isoenzymes / Q000235:genetics; D011485:Protein Binding; D011794:Quercetin / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D018160:Receptors, Cytoplasmic and Nuclear / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism; D011960:Receptors, Estrogen / Q000235:genetics; D011974:Receptors, LH / Q000235:genetics; D011989:Receptors, Thyrotropin / Q000037:antagonists & inhibitors* / Q000235:genetics; D013256:Steroids / Q000737:chemistry* / Q000378:metabolism; D013329:Structure-Activity Relationship; D013972:Thyrotropin / Q000494:pharmacology
D006063:Chorionic Gonadotropin; D004967:Estrogens; D007527:Isoenzymes; D018160:Receptors, Cytoplasmic and Nuclear; D011960:Receptors, Estrogen; D011974:Receptors, LH; D011989:Receptors, Thyrotropin; D013256:Steroids; D004958:Estradiol; D004054:Diethylstilbestrol; D013972:Thyrotropin; D011794:Quercetin; D003634:DDT; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; C419510:adenylyl cyclase type V