ABSTRACT
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.
Subject(s)
Apoptosis , Homeodomain Proteins/metabolism , Transcription Factor Brn-3B/metabolism , Transcriptional Activation , Tumor Suppressor Protein p53/metabolism , bcl-2-Associated X Protein/genetics , Animals , Binding Sites , Cell Cycle , Cell Line , Cells, Cultured , Homeodomain Proteins/chemistry , Homeodomain Proteins/genetics , Mice , Mice, Knockout , Neurons/metabolism , Promoter Regions, Genetic , Protein Structure, Tertiary , Transcription Factor Brn-3B/chemistry , Transcription Factor Brn-3B/genetics , bcl-2-Associated X Protein/biosynthesisABSTRACT
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.
Subject(s)
Cold Temperature , Neurons, Afferent/physiology , Superior Cervical Ganglion/cytology , Sympathetic Nervous System/cytology , Animals , Antipruritics/pharmacology , Cells, Cultured , Ganglia, Spinal/cytology , Ganglia, Spinal/physiology , Ion Channels/genetics , Male , Menthol/pharmacology , Mice , Mice, Inbred C57BL , Neoplasm Proteins/genetics , Neurons, Afferent/cytology , Neurons, Afferent/drug effects , RNA, Messenger/analysis , Sensory Thresholds/physiology , Superior Cervical Ganglion/physiology , Sympathetic Nervous System/physiology , TRPA1 Cation Channel , TRPM Cation Channels , Transient Receptor Potential ChannelsABSTRACT
The Brn-3a transcription factor is critical for the normal development of the nervous system, promoting both neuronal survival and neurite outgrowth. By manipulating the Brn-3a gene in intact mice, we show that these two functions are separately controlled with an N-terminal domain being essential for neuronal survival, whereas the POU domain is essential for neurite outgrowth. Hence the two naturally occurring forms of Brn-3a, which either contain or lack the N-terminal domain, are likely to play distinct roles in the nervous system.
Subject(s)
Apoptosis/physiology , DNA-Binding Proteins/chemistry , DNA-Binding Proteins/genetics , Neurites/physiology , Transcription Factors/chemistry , Transcription Factors/genetics , Animals , Cells, Cultured , DNA-Binding Proteins/metabolism , Mice , Mice, Knockout , Mutagenesis, Insertional , Neurons, Afferent/pathology , Neurons, Afferent/physiology , Neurons, Afferent/ultrastructure , Protein Structure, Tertiary , Transcription Factor Brn-3 , Transcription Factor Brn-3A , Transcription Factors/metabolism , Trigeminal Ganglion/pathologyABSTRACT
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.
