RESUMO
The Brn-3a and Brn-3b transcription factor have opposite and antagonistic effects in neuroblastoma cells since Brn-3a is associated with differentiation whilst Brn-3b enhances proliferation in these cells. In this study, we demonstrate that like Brn-3a, Brn-3b physically interacts with p53. However, whereas Brn-3a repressed p53 mediated Bax expression but cooperated with p53 to increase p21cip1/waf1, this study demonstrated that co-expression of Brn-3b with p53 increases trans-activation of Bax promoter but not p21cip1/waf1. Consequently co-expression of Brn-3b with p53 resulted in enhanced apoptosis, which is in contrast to the increased survival and differentiation, when Brn-3a is co-expressed with p53. For Brn-3b to cooperate with p53 on the Bax promoter, it requires binding sites that flank p53 sites on this promoter. Furthermore, neurons from Brn-3b knock-out (KO) mice were resistant to apoptosis and this correlated with reduced Bax expression upon induction of p53 in neurons lacking Brn-3b compared with controls. Thus, the ability of Brn-3b to interact with p53 and modulate Bax expression may demonstrate an important mechanism that helps to determine the fate of cells when p53 is induced.
Assuntos
Apoptose , Proteínas de Homeodomínio/metabolismo , Fator de Transcrição Brn-3B/metabolismo , Ativação Transcricional , Proteína Supressora de Tumor p53/metabolismo , Proteína X Associada a bcl-2/genética , Animais , Sítios de Ligação , Ciclo Celular , Linhagem Celular , Células Cultivadas , Proteínas de Homeodomínio/química , Proteínas de Homeodomínio/genética , Camundongos , Camundongos Knockout , Neurônios/metabolismo , Regiões Promotoras Genéticas , Estrutura Terciária de Proteína , Fator de Transcrição Brn-3B/química , Fator de Transcrição Brn-3B/genética , Proteína X Associada a bcl-2/biossínteseRESUMO
Several mechanisms have been implicated in underlying the perception of cold, most notably the activation of TRPM8 and TRPA1. We have used ratiometric calcium imaging to reveal a population of neurons in the superior cervical ganglion (SCG) of the mouse that respond to cooling but are insensitive to menthol. Furthermore we show that the expression of the mRNA transcripts encoding the recently identified noxious cold-sensitive channel TRPA1 but not TRPM8 are expressed in the SCG. These data provide evidence for a population of cold-responsive neurons in the SCG whose cold-responsiveness could be mediated by the activation of TRPA1 and suggest that the sympathetic nervous system may play a direct role in mediating sympathetic responses to cold temperatures.
Assuntos
Temperatura Baixa , Neurônios Aferentes/fisiologia , Gânglio Cervical Superior/citologia , Sistema Nervoso Simpático/citologia , Animais , Antipruriginosos/farmacologia , Células Cultivadas , Gânglios Espinais/citologia , Gânglios Espinais/fisiologia , Canais Iônicos/genética , Masculino , Mentol/farmacologia , Camundongos , Camundongos Endogâmicos C57BL , Proteínas de Neoplasias/genética , Neurônios Aferentes/citologia , Neurônios Aferentes/efeitos dos fármacos , RNA Mensageiro/análise , Limiar Sensorial/fisiologia , Gânglio Cervical Superior/fisiologia , Sistema Nervoso Simpático/fisiologia , Canal de Cátion TRPA1 , Canais de Cátion TRPM , Canais de Potencial de Receptor TransitórioRESUMO
The critical role for programmed cell death in the normal development of the nervous system and the abnormal cell death that occurs in human neurodegenerative diseases renders it of vital importance to identify factors that enhance or reduce the levels of cell death in specific neuronal cells in the nervous system. We show that the Brn-3b transcription factor is essential for normal cell death responses in the peripheral nervous system and that in its absence neurons are resistant to a variety of death-inducing stimuli both in vitro and in vivo.