RESUMO
Signaling pathways invoke interplays between forward signaling and feedback to drive robust cellular response. In this study, we address the dynamics of growth factor signaling through profiling of protein phosphorylation and gene expression, demonstrating the presence of a kinetically defined cluster of delayed early genes that function to attenuate the early events of growth factor signaling. Using epidermal growth factor receptor signaling as the major model system and concentrating on regulation of transcription and mRNA stability, we demonstrate that a number of genes within the delayed early gene cluster function as feedback regulators of immediate early genes. Consistent with their role in negative regulation of cell signaling, genes within this cluster are downregulated in diverse tumor types, in correlation with clinical outcome. More generally, our study proposes a mechanistic description of the cellular response to growth factors by defining architectural motifs that underlie the function of signaling networks.
Assuntos
Retroalimentação Fisiológica/genética , Peptídeos e Proteínas de Sinalização Intercelular/fisiologia , Transdução de Sinais/genética , Fatores de Transcrição/fisiologia , Canais Iônicos Sensíveis a Ácido , Células Cultivadas , Análise por Conglomerados , Canais de Sódio Degenerina , Fator de Crescimento Epidérmico/fisiologia , Canais Epiteliais de Sódio/fisiologia , MAP Quinases Reguladas por Sinal Extracelular/fisiologia , Regulação da Expressão Gênica , Células HeLa , Humanos , Fatores de Transcrição Kruppel-Like/fisiologia , Fator de Transcrição MafF/fisiologia , Modelos Biológicos , Proteínas do Tecido Nervoso/fisiologia , Proteínas Nucleares/fisiologia , Fatores de Transcrição/genética , Tristetraprolina/fisiologiaRESUMO
Sprouty proteins are evolutionarily conserved negative feedback regulators of multiple receptor tyrosine kinases. Mammalian versions of these proteins differentially regulate signaling induced by the fibroblast and the epidermal growth factors (FGF and EGF, respectively). Herein we show that, although both growth factors elevate expression of Sprouty-2, FGF- and not EGF-induced activation of the Erk/MAPK pathway is inhibited by Sprouty-2. Attenuation of FGF-signaling is accompanied by the induction of Sprouty-2 phosphorylation on the amino-terminal as well as carboxyl-terminal tyrosine residues, which are less effectively modified upon EGF treatment. Mutagenesis of carboxyl-terminal tyrosines, especially a newly identified phosphorylation site, tyrosine 227, impaired the inhibitory activity of Sprouty-2. These results attribute a novel role for carboxyl-terminal tyrosine residues and yet unidentified phosphotyrosine-binding proteins in the differential regulation of Sprouty-2 activity.