title: Thyrotropin effect on the availability of Ni regulatory protein in FRTL-5 rat thyroid cells to ADP-ribosylation by pertussis toxin.
abstract: Incubation of FRTL-5 rat thyroid cell membranes with [32P]NAD and pertussis toxin results in the specific ADP-ribosylation of a protein of about 40 kDa. This protein has the same molecular mass of the alpha i subunit of the adenylate cyclase regulatory protein Ni and is distinct from proteins ADP-ribosylated by cholera toxin in the same membranes. Prior treatment of FRTL-5 cells with pertussis toxin results in the ADP-ribosylation of Ni, as indicated by the loss of the toxin substrate in the ADP-ribosylation assay performed with membranes prepared from such cells. Preincubation of FRTL-5 cells with thyrotropin causes the same loss; cholera toxin has no such effect. Pertussis toxin, as do thyrotropin and cholera toxin, increases cAMP levels in FRTL-5 cells. Forskolin together with thyrotropin, cholera toxin or pertussis toxin causes a further increase in cAMP levels. Pertussis toxin and thyrotropin are not additive in their ability to increase adenylate cyclase activity, whereas both substances are additive with cholera toxin. A role of Ni in the thyrotropin regulation of the adenylate cyclase activity in thyroid cells is proposed.
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D037361:Adenylate Cyclase Toxin; D000818:Animals; D002460:Cell Line; D002772:Cholera Toxin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D007700:Kinetics; D037342:Pertussis Toxin; D011506:Proteins / Q000302:isolation & purification; D051381:Rats; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism*; D013972:Thyrotropin / Q000494:pharmacology*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
chemical_list: D037361:Adenylate Cyclase Toxin; D011506:Proteins; D010566:Virulence Factors, Bordetella; D000246:Adenosine Diphosphate Ribose; D013972:Thyrotropin; D002772:Cholera Toxin; D000242:Cyclic AMP; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins