RESUMO
Erythropoietin (Epo) and thyroid hormone (T(3)) are key molecules in the development of red blood cells. We have shown previously that the tyrosine kinase Lyn is involved in differentiation signals emanating from an activated erythropoietin receptor. Here we demonstrate that Lyn interacts with thyroid hormone receptor-interacting protein 1 (Trip-1), a transcriptional regulator associated with the T(3) receptor, providing a link between the Epo and T(3) signaling pathways. Trip-1 co-localized with Lyn and the T(3) receptor alpha in the cytoplasm/plasma membrane of erythroid cells but translocated to discrete nuclear foci shortly after Epo-induced differentiation. Our data reveal that T(3) stimulated the proliferation of immature erythroid cells, and inhibited maturation promoted by erythropoietin. Removal of T(3) reduced cell division and enhanced terminal differentiation. This was accompanied by large increases in the cell cycle inhibitor p27(Kip1) and by increasing expression of erythroid transcription factors GATA-1, EKLF, and NF-E2. Strikingly, a truncated Trip-1 inhibited both erythropoietin-induced maturation and T(3)-initiated cell division. This mutant Trip-1 acted in a dominant negative fashion by eliminating endogenous Lyn, elevating p27(Kip1), and blocking T(3) response elements. These data demonstrate that Trip-1 can simultaneously modulate responses involving both cytokine and nuclear receptors.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal , Fatores de Transcrição/metabolismo , Fatores de Transcrição/fisiologia , ATPases Associadas a Diversas Atividades Celulares , Animais , Proteínas de Ciclo Celular/metabolismo , Diferenciação Celular , Divisão Celular , Núcleo Celular/metabolismo , Células Cultivadas , Inibidor de Quinase Dependente de Ciclina p27 , Citocinas/metabolismo , Proteínas de Ligação a DNA/biossíntese , Eritrócitos/metabolismo , Fatores de Ligação de DNA Eritroide Específicos , Técnica Indireta de Fluorescência para Anticorpo , Fator de Transcrição GATA1 , Immunoblotting , Fatores de Transcrição Kruppel-Like , Proteínas com Domínio LIM , Camundongos , Fator de Transcrição NF-E2 , Subunidade p45 do Fator de Transcrição NF-E2 , Testes de Precipitina , Complexo de Endopeptidases do Proteassoma , Ligação Proteica , Retroviridae/metabolismo , Transdução de Sinais , Fatores de Transcrição/biossíntese , Transcrição Gênica , Transfecção , Proteínas Supressoras de Tumor/metabolismo , Técnicas do Sistema de Duplo-Híbrido , Quinases da Família src/biossínteseRESUMO
Hemopoietic lineage switching occurs when leukemic cells, apparently committed to one lineage, change and display the phenotype of another pathway. cDNA representational difference analysis was used to identify myeloid-specific genes that may be associated with an erythroid to myeloid lineage switch involving the murine J2E erythroleukemic cell line. One of the genes isolated (HLS7) is homologous to the novel human oncogene myeloid leukemia factor 1 (MLF1) involved in the t(3;5)(q25.1;q34) translocation associated with acute myeloid leukemia. Enforced expression of HLS7 in J2E cells induced a monoblastoid phenotype, thereby recapitulating the spontaneous erythroid to myeloid lineage switch. HLS7 also inhibited erythropoietin- or chemically-induced differentiation of erythroleukemic cell lines and suppressed development of erythropoietin-responsive colonies in semi-solid culture. However, intracellular signaling activated by erythropoietin was not impeded by ectopic expression of HLS7. In contrast, HLS7 promoted maturation of M1 monoblastoid cells and increased myeloid colony formation in vitro. These data show that HLS7 can influence erythroid/myeloid lineage switching and the development of normal hemopoietic cells.