Regulation of proliferation by the cholera toxin B subunit in FRTL-5 cells may involve a mechanism independent from the modulation of membrane receptor function.
In quiescent rat thyroid (FRTL-5) cells, the B subunit of cholera toxin, which binds to cell surface ganglioside GM1 specifically, alone induced DNA synthesis and markedly enhanced that induced by insulin in serum-free medium. On the other hand, the B subunit inhibited DNA synthesis induced by thyrotropin (TSH). The B subunit did not activate adenylate cyclase and had no effect on the TSH-induced cyclic adenosine 3',5'-monophosphate (cAMP) production. Moreover, the B subunit inhibited DNA synthesis induced by dibutyryl cAMP (Bt2cAMP) or phorbol-12-myristate-13-acetate (PMA). These data demonstrate that the B subunit has both stimulatory and inhibitory effects on DNA synthesis in FRTL-5 cells depending on the presence of other growth factors and that these effects on cell proliferation by the interaction of the B subunit, possibly with cell surface ganglioside GM1, may involve a mechanism independent from the modulation of membrane receptor function through interaction with growth factor receptor.
Tetsumoto
T
T
Department of Laboratory Medicine, Osaka University Medical School, Japan.
Takada
K
K
Amino
N
N
Miyai
K
K
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects*; D002460:Cell Line; D002772:Cholera Toxin / Q000494:pharmacology*; D000242:Cyclic AMP / Q000502:physiology; D005732:Gangliosides / Q000502:physiology*; D007328:Insulin / Q000494:pharmacology; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013961:Thyroid Gland / Q000166:cytology; D013972:Thyrotropin / Q000494:pharmacology
D005732:Gangliosides; D007328:Insulin; D003994:Bucladesine; D013972:Thyrotropin; D002772:Cholera Toxin; D000242:Cyclic AMP; D013755:Tetradecanoylphorbol Acetate