RESUMO
The signal transducer and activator of transcription 5 (STAT5) regulates differentiation, survival, proliferation and transformation of hematopoietic cells. Upon cytokine stimulation, STAT5 tyrosine phosphorylation (pYSTAT5) is transient, while in diverse neoplastic cells persistent overexpression and enhanced pYSTAT5 are frequently found. Post-translational modifications might contribute to enhanced STAT5 activation in the context of transformation, but the strength and duration of pYSTAT5 are incompletely understood. We found that O-GlcNAcylation and tyrosine phosphorylation act together to trigger pYSTAT5 levels and oncogenic transcription in neoplastic cells. The expression of a mutated hyperactive gain-of-function (GOF) STAT5 without O-GlcNAcylation resulted in decreased tyrosine phosphorylation, oligomerization and transactivation potential and complete loss of oncogenic transformation capacity. The lack of O-GlcNAcylation diminished phospho-ERK and phospho-AKT levels. Our data show that O-GlcNAcylation of STAT5 is an important process that contributes to oncogenic transcription through enhanced STAT5 tyrosine phosphorylation and oligomerization driving myeloid transformation. O-GlcNAcylation of STAT5 could be required for nutrient sensing and metabolism of cancer cells.
Assuntos
Acetilglucosamina/metabolismo , Transformação Celular Neoplásica , Transtornos Mieloproliferativos/etiologia , Processamento de Proteína Pós-Traducional , Fator de Transcrição STAT5/metabolismo , Ativação Transcricional , Proteínas Supressoras de Tumor/metabolismo , Animais , Linhagem Celular , Feminino , Regulação Neoplásica da Expressão Gênica , Genes Reporter , Glicosilação , Humanos , Interleucina-3/farmacologia , Tecido Linfoide/citologia , Masculino , Camundongos , Mutagênese Sítio-Dirigida , Transtornos Mieloproliferativos/genética , Fosforilação , Fosfotirosina/metabolismo , Quimera por Radiação , Proteínas Recombinantes de Fusão/metabolismo , Fator de Transcrição STAT5/genética , Transdução de Sinais , Linfócitos T/citologia , Linfócitos T/efeitos dos fármacos , Linfócitos T/metabolismo , Treonina/metabolismo , Proteínas Supressoras de Tumor/genéticaRESUMO
The balance between hematopoietic progenitor commitment and self-renewal versus differentiation is controlled by various transcriptional regulators cooperating with cytokine receptors. Disruption of this balance is increasingly recognized as important in the development of leukemia, by causing enhanced renewal and differentiation arrest. We studied regulation of renewal versus differentiation in primary murine erythroid progenitors that require cooperation of erythropoietin receptor (EpoR), the receptor tyrosine kinase c-Kit and a transcriptional regulator (glucocorticoid receptor; GR) for sustained renewal. However, mice defective for GR- (GR(dim/dim)), EpoR- (EpoR(H)) or STAT5ab function (Stat5ab(-/-)) show no severe erythropoiesis defects in vivo. Using primary erythroblast cultures from these mutants, we present genetic evidence that functional GR, EpoR, and Stat5 are essential for erythroblast renewal in vitro. Cells from GR(dim/dim), EpoR(H), and Stat5ab(-/-) mice showed enhanced differentiation instead of renewal, causing accumulation of mature cells and gradual proliferation arrest. Stat5ab was additionally required for Epo-induced terminal differentiation: differentiating Stat5ab(-/-) erythroblasts underwent apoptosis instead of erythrocyte maturation, due to absent induction of the antiapoptotic protein Bcl-X(L). This defect could be fully rescued by exogenous Bcl-X(L). These data suggest that signaling molecules driving leukemic proliferation may also be essential for prolonged self-renewal of normal erythroid progenitors.
