RESUMO
Loss of tumor suppressor adenomatous polyposis coli (APC) activates ß-catenin to initiate colorectal tumorigenesis. However, ß-catenin (CTNNB1) activating mutations rarely occur in human colorectal cancer (CRC). We found that APC loss also results in up-regulation of IL-6 signal transducer (IL-6ST/gp130), thereby activating Src family kinases (SFKs), YAP, and STAT3, which are simultaneously up-regulated in the majority of human CRC. Although, initial YAP activation, which stimulates IL6ST gene transcription, may be caused by reduced serine phosphorylation, sustained YAP activation depends on tyrosine phosphorylation by SFKs, whose inhibition, along with STAT3-activating JAK kinases, causes regression of established colorectal tumors. These results explain why APC loss is a more potent initiating event than the mere activation of CTNNB1.
Assuntos
Proteína da Polipose Adenomatosa do Colo/metabolismo , Neoplasias Colorretais/metabolismo , Receptor gp130 de Citocina/metabolismo , Proteínas Nucleares/metabolismo , Fatores de Transcrição/metabolismo , Proteína da Polipose Adenomatosa do Colo/genética , Adulto , Idoso , Animais , Carcinogênese/genética , Carcinogênese/metabolismo , Proteínas de Ciclo Celular , Linhagem Celular Tumoral , Neoplasias Colorretais/genética , Neoplasias Colorretais/patologia , Receptor gp130 de Citocina/genética , Feminino , Células HCT116 , Células HEK293 , Células HT29 , Humanos , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Pessoa de Meia-Idade , Mutação , beta Catenina/genética , beta Catenina/metabolismoRESUMO
TALE-homeodomain proteins function as components of heteromeric complexes that contain one member each of the PBC and MEIS/PREP subclasses. We recently showed that MEIS2 cooperates with the neurogenic transcription factor PAX6 in the control of adult subventricular zone (SVZ) neurogenesis in rodents. Expression of the PBC protein PBX1 in the SVZ has been reported, but its functional role(s) has not been investigated. Using a genetic loss-of-function mouse model, we now show that Pbx1 is an early regulator of SVZ neurogenesis. Targeted deletion of Pbx1 by retroviral transduction of Cre recombinase into Pbx2-deficient SVZ stem and progenitor cells carrying floxed alleles of Pbx1 significantly reduced the production of neurons and increased the generation of oligodendrocytes. Loss of Pbx1 expression in neuronally committed neuroblasts in the rostral migratory stream in a Pbx2 null background, by contrast, severely compromised cell survival. By chromatin immunoprecipitation from endogenous tissues or isolated cells, we further detected PBX1 binding to known regulatory regions of the neuron-specific genes Dcx and Th days or even weeks before the respective genes are expressed during the normal program of SVZ neurogenesis, suggesting that PBX1 might act as a priming factor to mark these genes for subsequent activation. Collectively, our results establish that PBX1 regulates adult neural cell fate determination in a manner beyond that of its heterodimerization partner MEIS2.
Assuntos
Envelhecimento/metabolismo , Proteínas de Homeodomínio/metabolismo , Ventrículos Laterais/metabolismo , Neurogênese , Fatores de Transcrição/metabolismo , Animais , Sequência de Bases , Diferenciação Celular , Linhagem da Célula , Movimento Celular , Sobrevivência Celular , Células Cultivadas , Proteínas do Domínio Duplacortina , Proteína Duplacortina , Elementos Facilitadores Genéticos/genética , Deleção de Genes , Regulação da Expressão Gênica no Desenvolvimento , Marcação de Genes , Proteínas de Homeodomínio/genética , Camundongos Endogâmicos C57BL , Proteínas Associadas aos Microtúbulos/genética , Proteínas Associadas aos Microtúbulos/metabolismo , Neurogênese/genética , Neuropeptídeos/genética , Neuropeptídeos/metabolismo , Bulbo Olfatório/metabolismo , Oligodendroglia/citologia , Oligodendroglia/metabolismo , Fator de Transcrição 1 de Leucemia de Células Pré-B , Ligação Proteica , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas/metabolismo , Células-Tronco/citologia , Células-Tronco/metabolismo , Fatores de Transcrição/genética , Tirosina 3-Mono-Oxigenase/metabolismoRESUMO
Meis homeodomain transcription factors control cell proliferation, cell fate specification and differentiation in development and disease. Previous studies have largely focused on Meis contribution to the development of non-neuronal tissues. By contrast, Meis function in the brain is not well understood. Here, we provide evidence for a dual role of the Meis family protein Meis2 in adult olfactory bulb (OB) neurogenesis. Meis2 is strongly expressed in neuroblasts of the subventricular zone (SVZ) and rostral migratory stream (RMS) and in some of the OB interneurons that are continuously replaced during adult life. Targeted manipulations with retroviral vectors expressing function-blocking forms or with small interfering RNAs demonstrated that Meis activity is cell-autonomously required for the acquisition of a general neuronal fate by SVZ-derived progenitors in vivo and in vitro. Additionally, Meis2 activity in the RMS is important for the generation of dopaminergic periglomerular neurons in the OB. Chromatin immunoprecipitation identified doublecortin and tyrosine hydroxylase as direct Meis targets in newly generated neurons and the OB, respectively. Furthermore, biochemical analyses revealed a previously unrecognized complex of Meis2 with Pax6 and Dlx2, two transcription factors involved in OB neurogenesis. The full pro-neurogenic activity of Pax6 in SVZ derived neural stem and progenitor cells requires the presence of Meis. Collectively, these results show that Meis2 cooperates with Pax6 in generic neurogenesis and dopaminergic fate specification in the adult SVZ-OB system.
Assuntos
Neurônios Dopaminérgicos/citologia , Proteínas do Olho/metabolismo , Proteínas de Homeodomínio/metabolismo , Neurogênese/fisiologia , Bulbo Olfatório/embriologia , Fatores de Transcrição Box Pareados/metabolismo , Proteínas Repressoras/metabolismo , Animais , Sequência de Bases , Proliferação de Células , Neurônios Dopaminérgicos/metabolismo , Proteínas do Domínio Duplacortina , Proteínas de Homeodomínio/genética , Camundongos , Camundongos Endogâmicos C57BL , Proteínas Associadas aos Microtúbulos/metabolismo , Dados de Sequência Molecular , Células-Tronco Neurais/metabolismo , Neurogênese/genética , Neuropeptídeos/metabolismo , Bulbo Olfatório/citologia , Bulbo Olfatório/crescimento & desenvolvimento , Fator de Transcrição PAX6 , Interferência de RNA , RNA Interferente Pequeno/genética , Fatores de Transcrição/metabolismo , Tirosina 3-Mono-Oxigenase/metabolismoRESUMO
Adult neurogenesis is regulated by stem cell niche-derived extrinsic factors and cell-intrinsic regulators, yet the mechanisms by which niche signals impinge on the activity of intrinsic neurogenic transcription factors remain poorly defined. Here, we report that MEIS2, an essential regulator of adult SVZ neurogenesis, is subject to posttranslational regulation in the SVZ olfactory bulb neurogenic system. Nuclear accumulation of MEIS2 in adult SVZ-derived progenitor cells follows downregulation of EGFR signaling and is modulated by methylation of MEIS2 on a conserved arginine, which lies in close proximity to nested binding sites for the nuclear export receptor CRM1 and the MEIS dimerization partner PBX1. Methylation impairs interaction with CRM1 without affecting PBX1 dimerization and thereby allows MEIS2 nuclear accumulation, a prerequisite for neuronal differentiation. Our results describe a form of posttranscriptional modulation of adult SVZ neurogenesis whereby an extrinsic signal fine-tunes neurogenesis through posttranslational modification of a transcriptional regulator of cell fate.
Assuntos
Arginina/metabolismo , Diferenciação Celular , Núcleo Celular/metabolismo , Proteínas de Homeodomínio/metabolismo , Ventrículos Laterais/citologia , Células-Tronco Neurais/citologia , Neurônios/citologia , Sequência de Aminoácidos , Animais , Ligação Competitiva , Receptores ErbB/metabolismo , Proteínas de Homeodomínio/química , Carioferinas/metabolismo , Metilação , Camundongos Endogâmicos C57BL , Células-Tronco Neurais/metabolismo , Neurônios/metabolismo , Fator de Transcrição 1 de Leucemia de Células Pré-B/metabolismo , Ligação Proteica , Estabilidade Proteica , Transporte Proteico , Receptores Citoplasmáticos e Nucleares/metabolismo , Transdução de Sinais , Proteína Exportina 1RESUMO
Pre-B-cell leukemia homeobox (PBX) and myeloid ecotropic viral integration site (MEIS) proteins control cell fate decisions in many physiological and pathophysiological contexts, but how these proteins function mechanistically remains poorly defined. Focusing on the first hours of neuronal differentiation of adult subventricular zone-derived stem/progenitor cells, we describe a sequence of events by which PBX-MEIS facilitates chromatin accessibility of transcriptionally inactive genes: In undifferentiated cells, PBX1 is bound to the H1-compacted promoter/proximal enhancer of the neuron-specific gene doublecortin (Dcx) Once differentiation is induced, MEIS associates with chromatin-bound PBX1, recruits PARP1/ARTD1, and initiates PARP1-mediated eviction of H1 from the chromatin fiber. These results for the first time link MEIS proteins to PARP-regulated chromatin dynamics and provide a mechanistic basis to explain the profound cellular changes elicited by these proteins.