RESUMEN
Although the p38 mitogen-activated protein kinases are active in many neuronal populations in the peripheral and central nervous systems, little is known about the physiological functions of p38 in postmitotic neurons. We report that p38 activity determines in vitro and in vivo the switch from noradrenergic to cholinergic neurotransmission that occurs in sympathetic neurons on exposure to the neuropoietic cytokines CNTF and LIF. This transdifferentiation serves as a model for the plastic mechanisms that enable mature neurons to change some of their central functions without passing through the cell cycle. We demonstrate that in postmitotic neurons, p38 and STAT pathways are concurrently activated by neuropoietic cytokine treatment for at least 12 h overlapping with changes in neurotransmitter marker gene expression. Inhibition of p38 blocks the upregulation of the nuclear matrix protein Satb2 and of cholinergic markers by CNTF without affecting STAT3 phosphorylation. Conversely, overexpression of p38α or ß in the absence of cytokines stimulates cholinergic marker expression. The neurotransmitter switch in vitro is impaired in neurons isolated from p38ß(-/-) mice. Consistent with these in vitro results, a substantial loss of cells expressing cholinergic properties is observed in vivo in the stellate ganglion of mature mice deficient in the p38ß isoform.
Asunto(s)
Acetilcolina/fisiología , Transdiferenciación Celular/genética , Neuronas Colinérgicas/enzimología , Proteína Quinasa 11 Activada por Mitógenos/genética , Proteína Quinasa 14 Activada por Mitógenos/genética , Ganglio Estrellado/enzimología , Animales , Animales Recién Nacidos , Muerte Celular/efectos de los fármacos , Muerte Celular/genética , Transdiferenciación Celular/efectos de los fármacos , Células Cultivadas , Neuronas Colinérgicas/citología , Neuronas Colinérgicas/efectos de los fármacos , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Proteína Quinasa 11 Activada por Mitógenos/deficiencia , Proteína Quinasa 14 Activada por Mitógenos/deficiencia , Neurotransmisores/genética , Neurotransmisores/fisiología , Ratas , Ratas Sprague-Dawley , Factores de Transcripción STAT/fisiología , Transducción de Señal/efectos de los fármacos , Transducción de Señal/genética , Ganglio Estrellado/citología , Ganglio Estrellado/crecimiento & desarrolloRESUMEN
Sympathetic neurons can switch their neurotransmitter phenotype from noradrenergic to cholinergic on exposure to neuropoietic cytokines in vitro and in vivo. Here, we provide evidence that this transspecification is regulated by the chromatin architecture protein Satb2. Treatment with the neuropoietic cytokines ciliary neurotrophic factor (CNTF) and leukemia inhibitory factor rapidly and strongly increases Satb2 transcript and protein levels in cultures of rat superior cervical ganglia neurons. Knockdown of endogenous Satb2 by short interfering RNA prevents the upregulation of choline acetyltransferase (Chat) and vesicular acetylcholine transporter (Vacht) by CNTF as well as the loss of norepinephrine transporter (Net). Conversely, overexpression of Satb2 in the noradrenergic sympathetic phenotype results in a marked increase of Chat and Vacht expression and reduced Net mRNA levels in the absence of neuropoietic cytokines. Chromatin immunoprecipitation analysis in primary sympathetic neurons reveals that Satb2 binds to matrix attachment regions (MARs) within the Chat locus. In vivo, in the rat stellate ganglion, Satb2 is expressed exclusively in sudomotor cholinergic neurons innervating the sweat glands and only after establishment of contact between neurons and target. These findings demonstrate a function of the MAR-binding protein Satb2 in growth factor-dependent neurotransmitter plasticity in postmitotic neurons.
Asunto(s)
Proteínas de Unión a la Región de Fijación a la Matriz/fisiología , Neurotransmisores/fisiología , Ganglio Cervical Superior/fisiología , Factores de Transcripción/fisiología , Fibras Adrenérgicas/fisiología , Animales , Animales Recién Nacidos , Células Cultivadas , Técnicas de Silenciamiento del Gen , Proteínas de Unión a la Región de Fijación a la Matriz/genética , Mitosis/genética , Mitosis/fisiología , Plasticidad Neuronal/genética , Plasticidad Neuronal/fisiología , Neurotransmisores/genética , Proteínas Asociadas a Matriz Nuclear/genética , Proteínas Asociadas a Matriz Nuclear/fisiología , Ratas , Factores de Transcripción/genéticaRESUMEN
During late developmental phases individual sympathetic neurons undergo a switch from noradrenergic to cholinergic neurotransmission. This phenomenon of plasticity depends on target-derived signals in vivo and is triggered by neurotrophic factors in neuronal cultures. To analyze genome-wide expression differences between the two transmitter phenotypes we employed DNA microarrays. RNA expression profiles were obtained from chick paravertebral sympathetic ganglia, treated with neurotrophin 3, glial cell line-derived neurotrophic factor or ciliary neurotrophic factor, all of which stimulate cholinergic differentiation. Results were compared with the effect of nerve growth factor, which functions as a pro-noradrenergic stimulus. The gene set common to all three comparisons defined the noradrenergic and cholinergic synexpression groups. Several functional categories, such as signal transduction, G-protein-coupled signaling, cation transport, neurogenesis and synaptic transmission, were enriched in these groups. Experiments based on the prediction that some of the identified genes play a role in the neurotransmitter switch identified bone morphogenetic protein signaling as an inhibitor of cholinergic differentiation.
