Thyrotropin regulates autophosphorylation and kinase activity in both the insulin and the insulin-like growth factor-I receptors in FRTL5 cells. (Articolo in rivista)

Type
Label
  • Thyrotropin regulates autophosphorylation and kinase activity in both the insulin and the insulin-like growth factor-I receptors in FRTL5 cells. (Articolo in rivista) (literal)
Anno
  • 1992-01-01T00:00:00+01:00 (literal)
Alternative label
  • Condorelli G, Formisano P, Miele C, Beguinot F. (1992)
    Thyrotropin regulates autophosphorylation and kinase activity in both the insulin and the insulin-like growth factor-I receptors in FRTL5 cells.
    in Endocrinology (Philadelphia)
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Condorelli G, Formisano P, Miele C, Beguinot F. (literal)
Rivista
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • Centro di Endocrinologia ed Oncologia Sperimentale del C.N.R., University of Naples, II Medical School, Italy. (literal)
Titolo
  • Thyrotropin regulates autophosphorylation and kinase activity in both the insulin and the insulin-like growth factor-I receptors in FRTL5 cells. (literal)
Abstract
  • TSH regulation of insulin and insulin-like growth factor-I (IGF-I) receptor kinases has been studied in FRTL5 cultured thyroid cells. Preincubation of intact cells with TSH increased by 2-fold insulin and IGF-I receptor autophosphorylation and phosphorylation of the p175 endogenous substrate for the receptors. Enhanced phosphorylations reached a maximum within 30 min, were maintained for 30 min more, and vanished after 120 min of TSH incubation. TSH dose-responses exhibited half-maximal and maximal effects at 1 and 10 pM, respectively. In vitro, insulin as well as IGF-I receptors purified from cells treated with 10 pM TSH also exhibited 2-fold enhanced receptor autophosphorylation and kinase activity toward the exogenous substrate poly(Glu,Tyr) (4:1). At variance with TSH, cell incubation with either 8-bromo-cAMP or the protein kinase-C activator 12-O-tetradecanoylphorbol-13-acetate inhibited insulin and IGF-I receptor kinases. In intact cells, TSH stimulation of insulin and IGF-I receptor kinases was accompanied by enhanced turnover of phosphate on autophosphorylated receptors, increased receptor tyrosine phosphorylation, and decreased receptor serine/threonine phosphorylation in response to insulin. Incubation of in vivo labeled insulin and IGF-I receptors with extracts from TSH-treated cells also decreased receptor phosphoserine and phosphothreonine content. Furthermore, preincubation of insulin and IGF-I receptors with extracts from TSH-treated cells enhanced in vitro autophosphorylation. The latter effect was inhibited by the serine/threonine phosphatase inhibitors fluoride and okadaic acid, but not by the tyrosine phosphatase inhibitor vanadate. The data suggest that in FRTL5 cells, TSH induces the activity of a Ser/Thr protein phosphatase, which dephosphorylates insulin and IGF-I receptors and enhances their endogenous kinases. (literal)
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