Alteration of the functional activity of Gs protein in thyrotropin-desensitized pig thyroid cells.
Changes in the sensitivity of adenylyl cyclase observed in pig thyroid cells cultured 2 days in the presence of thyroid-stimulating hormone (TSH) or forskolin were assessed by examining the properties of Gs protein. Chronic treatment of thyroid cells with various concentrations of TSH (0.01-1 mU/ml) or forskolin (0.1-10 microM) increased the response of adenylyl cyclase to a further stimulation by forskolin or NaF + AlCl3 ([AlF4]-). In contrast, the enzyme activation promoted by guanosine 5'-(beta,gamma-imido) triphosphate (Gpp(NH)p) was markedly affected. There was a significant increase in adenylyl cyclase activation by Gpp(NH)p in membranes from cells treated with low concentrations of TSH (less than or equal to 0.1 mU/ml) or forskolin (less than or equal to 1 microM) but a significant decrease in membranes from cells cultured with a higher concentration of TSH (1 mU/ml) or forskolin (10 microM). This decrease in Gpp(NH)p-stimulated adenylyl cyclase activity was mimicked by 8-bromo-cAMP but not by 1,9-dideoxyforskolin, a forskolin analogue which has lost its ability to activate adenylyl cyclase. There was a good correlation with the ability of Gs protein to be ADP-ribosylated by cholera toxin: labeling of Gs protein decreased following chronic treatment of thyroid cells with TSH (1 mU/ml) or forskolin (10 microM). In contrast, under the same experimental culture conditions a slight but significant increase in the quantity of Gs subunits was observed by immunoblotting analysis.(ABSTRACT TRUNCATED AT 250 WORDS)
Delemer
B
B
Unité de Recherche sur la Glande Thyroide et la Régulation Hormonale, U.96, INSERM, Hôpital du Kremlin-Bicêtre, France.
Dib
K
K
Saunier
B
B
Haye
B
B
Jacquemin
C
C
Corrèze
C
C
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D002772:Cholera Toxin / Q000494:pharmacology; D005576:Colforsin / Q000031:analogs & derivatives / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D019204:GTP-Binding Proteins / Q000378:metabolism*; D015290:Second Messenger Systems / Q000187:drug effects; D013552:Swine / Q000378:metabolism; D013961:Thyroid Gland / Q000166:cytology / Q000378:metabolism*; D013972:Thyrotropin / Q000494:pharmacology*
D005576:Colforsin; D000246:Adenosine Diphosphate Ribose; D015124:8-Bromo Cyclic Adenosine Monophosphate; D013972:Thyrotropin; D002772:Cholera Toxin; D000242:Cyclic AMP; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases; C047983:1,9-dideoxyforskolin