Fibronectin-induced proliferation in thyroid cells is mediated by alphavbeta3 integrin through Ras/Raf-1/MEK/ERK and calcium/CaMKII signals.
J Clin Endocrinol Metab
; 90(5): 2865-73, 2005 May.
Article
em En
| MEDLINE
| ID: mdl-15687337
ABSTRACT
We recently demonstrated in an immortalized thyroid cell line that integrin stimulation by fibronectin (FN) simultaneously activates two signaling pathways Ras/Raf/MAPK kinase (Mek)/Erk and calcium Ca2+/calcium calmodulin-dependent kinase II (CaMKII). Both signals are necessary to stimulate Erk phosphorylation because CaMKII modulates Ras-induced Raf-1 activity. In this study we present evidence that extends these findings to normal human thyroid cells in primary culture, demonstrating its biological significance in a more physiological cell model. In normal thyroid cells, immobilized FN-induced activation of p21Ras and Erk phosphorylation. This pathway was responsible for FN-induced cell proliferation. Concurrent increase of intracellular Ca2+ concentration and CaMKII activation was observed. Both induction of p21Ras activity and increase of intracellular Ca2+ concentration were mediated by FN binding to alphavbeta3 integrin. Inhibition of the Ca2+/CaMKII signal pathway by calmodulin or CaMKII inhibitors completely abolished the FN-induced Erk phosphorylation. Binding to FN induced Raf-1 and CaMKII to form a protein complex, indicating that intersection between Ras/Raf/Mek/Erk and Ca2+/CaMKII signaling pathways occurred at Raf-1 level. Interruption of the Ca2+/CaMKII signal pathway arrested cell proliferation induced by FN. We also analyzed thyroid tumor cell lines that displayed concomitant aberrant integrin expression and signal transduction. These data confirm that integrin activation by FN in normal thyroid cells generates Ras/Raf/Mek/Erk and Ca2+/CaMKII signaling pathways and that both are necessary to stimulate cell proliferation, whereas in thyroid tumors integrin signaling is altered.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Glândula Tireoide
/
Proteínas Proto-Oncogênicas p21(ras)
/
Fibronectinas
/
Proteínas Quinases Dependentes de Cálcio-Calmodulina
/
Proteínas Proto-Oncogênicas c-raf
/
Sinalização do Cálcio
/
Quinases de Proteína Quinase Ativadas por Mitógeno
/
Integrina alfaVbeta3
/
MAP Quinases Reguladas por Sinal Extracelular
Tipo de estudo:
Prognostic_studies
Limite:
Humans
Idioma:
En
Ano de publicação:
2005
Tipo de documento:
Article