Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 8 de 8
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
J Cell Sci ; 122(Pt 19): 3554-65, 2009 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-19759287

RESUMO

Functional and protein interactions between the N-methyl-D-aspartate type of glutamate receptor (NMDAR) and neurotrophin or ephrin receptors play essential roles in neuronal survival and differentiation. A shared downstream effector for neurotrophin- and ephrin-receptor signaling is kinase D-interacting substrate of 220 kDa (Kidins220), also known as ankyrin repeat-rich membrane spanning (ARMS). Because this molecule is obligatory for neurotrophin-induced differentiation, we investigated whether Kidins220/ARMS and NMDAR functions were related. Here, we identify an association between these proteins and discover that excitotoxicity, a specific form of neuronal death induced by NMDAR overstimulation, dramatically decreases Kidins220/ARMS levels in cortical neurons and in a model of cerebral ischemia. Kidins220/ARMS downregulation is triggered by overactivation of NMDARs containing NR2B subunits and subsequent Ca(2+) influx, and involves a dual mechanism: rapid cleavage by the Ca(2+)-dependent protease calpain and calpain-independent silencing of Kidins220/Arms gene transcription. Additionally, Kidins220/ARMS knockdown decreases ERK activation and basal neuronal viability, and enhances neuronal death under excitotoxic conditions. Our results demonstrate Kidins220/ARMS participation in neuronal life and death pathways, and constitute the first report of its regulation under pathological conditions.


Assuntos
Isquemia Encefálica/fisiopatologia , Regulação para Baixo , Proteínas de Membrana/metabolismo , Neurônios/citologia , Fosfoproteínas/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Animais , Isquemia Encefálica/metabolismo , Morte Celular , Sobrevivência Celular , Células Cultivadas , Modelos Animais de Doenças , Humanos , Masculino , Proteínas de Membrana/genética , Neurônios/metabolismo , Fosfoproteínas/genética , Ligação Proteica , Ratos , Ratos Sprague-Dawley , Ratos Wistar , Receptores de N-Metil-D-Aspartato/genética
2.
J Biol Chem ; 280(41): 35018-27, 2005 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-16049015

RESUMO

The N-methyl-D-aspartate (NMDA) type of glutamate receptor (NMDAR) plays central roles in normal and pathological neuronal functioning. We have examined the regulation of the NR1 subunit of the NMDAR in response to excessive activation of this receptor in in vitro and in vivo models of excitotoxicity. NR1 protein expression in cultured cortical neurons was specifically reduced by stimulation with 100 microM NMDA or glutamate. NMDA decreased NR1 protein amounts by 71% after 8 h. Low NMDA concentrations (< or = 10 microM) had no effect. NR1 down-regulation was inhibited by the general NMDAR antagonist DL-AP5 and also by ifenprodil, which specifically antagonizes NMDARs containing NR2B subunits. Arrest of NMDAR signaling with DL-AP5 after brief exposure to NMDA did not prevent subsequent NR1 decrease. Down-regulation of NR1 did not involve calpain cleavage but resulted from a decrease in de novo synthesis consequence of reduced mRNA amounts. In contrast, NMDA did not alter the expression of NR2A mRNA or newly synthesized protein. In neurons transiently transfected with an NR1 promoter/luciferase reporter construct, promoter activity was reduced by 68% after 2 h of stimulation with NMDA, and its inhibition required extracellular calcium. A similar mechanism of autoregulation of the receptor probably operates during cerebral ischemia, because NR1 mRNA and protein were strongly decreased at early stages of blood reperfusion in the infarcted brains of rats subjected to occlusion of the middle cerebral artery. Because NR1 is the obligatory subunit of NMDARs, this regulatory mechanism will be fundamental to NMDAR functioning.


Assuntos
Isquemia Encefálica/patologia , Regulação para Baixo , Receptores de N-Metil-D-Aspartato/química , Animais , Northern Blotting , Encéfalo/patologia , Cálcio/metabolismo , Corantes/farmacologia , Ácido Egtázico/análogos & derivados , Ácido Egtázico/farmacologia , Genes Reporter , Immunoblotting , Imuno-Histoquímica , Imunoprecipitação , Luciferases/metabolismo , Microscopia de Fluorescência , Modelos Biológicos , Neurônios/metabolismo , Regiões Promotoras Genéticas , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-Dawley , Receptores de Glutamato/química , Receptores de N-Metil-D-Aspartato/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Ribonucleases/química , Transdução de Sinais , Sais de Tetrazólio/farmacologia , Tiazóis/farmacologia , Fatores de Tempo , Transfecção
3.
Mech Ageing Dev ; 126(3): 431-8, 2005 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-15664631

RESUMO

An open issue in research on ageing is the extent to which responses to the environment during development can influence variability in life span in animals, and the health profile of the elderly in human populations. Both affluence and adversity in human societies have profound impacts on survivorship curves, and some of this effect may be traceable to effects in utero or in infancy. The Barker Hypothesis that links caloric restriction in very early life to disruptions of glucose-insulin metabolism in later life has attracted much attention, as well as some controversy, in medical circles. It is only rarely considered by evolutionary biologists working on phenotypic plasticity, or by biogerontologists studying model organisms such as C. elegans or Drosophila. One crucial mechanism by which animals can respond in an adaptive manner to adverse conditions, for example in nutrition or infection, during development is phenotypic plasticity. Here we begin with a discussion of adaptive plasticity in animals before asking what such phenomena may reveal of relevance to rates of ageing in animals, and in humans. We survey the evidence for effects on adult ageing of environmental conditions during development across mammalian and invertebrate model organisms, and ask whether evolutionary conserved mechanisms might be involved. We conclude that the Barker Hypothesis is poorly supported and argue that more work in human populations should be integrated with multi-disciplinary studies of ageing-related phenomena in experimental populations of different model species that are subjected to nutritional challenges or infections during pre-adult development.


Assuntos
Adaptação Fisiológica , Evolução Biológica , Longevidade/fisiologia , Fenótipo , Animais , Restrição Calórica , Meio Ambiente , Humanos , Modelos Animais
4.
Oncogene ; 23(54): 8756-65, 2004 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-15467737

RESUMO

Thyroid hormone receptors (TRs) are members of the ligand-inducible transcription factor superfamily. The two major functional TRs (alpha1 and beta1) have different spatial and temporal expression patterns and specific physiological functions for these isoforms are now starting to emerge. By expressing these TR isoforms individually in Swiss 3T3 fibroblasts, we found that TRbeta1 expression, in the absence of hormone, provokes a proliferation arrest in G0/G1, lengthening the cycling time. Upon serum stimulation TRbeta1-expressing cells showed a marked delay in the induction of cyclins D and E, in the phosphorylation of retinoblastoma protein, and in the activation of cyclin-dependent kinase 2, accompanied by increased levels of cyclin-dependent kinase inhibitor p27Kip1. Accordingly, serum-stimulated E2F-1 transcriptional activity was repressed by TRbeta1 in transient transfection experiments. Analysis of the receptor domains required for this effect confirmed that there is no need for a functional ligand-binding domain while the DNA-binding domain is essential. In this work, we demonstrate for the first time that TRbeta1 participates in the molecular mechanisms that control cell proliferation. The unliganded TRbeta1 impairs the normal induction of the G1/S cycle regulators preventing progression into the S phase.


Assuntos
Divisão Celular/fisiologia , Fase G1 , Receptores beta dos Hormônios Tireóideos/fisiologia , Animais , Sequência de Bases , Western Blotting , Primers do DNA , Fibroblastos/citologia , Citometria de Fluxo , Imunoprecipitação , Ligantes , Camundongos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Células Swiss 3T3
5.
Mol Cell Neurosci ; 26(3): 470-80, 2004 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-15234351

RESUMO

trkB as receptor for neurotrophins brain-derived neurotrophic factor (BDNF)/neurotrophin (NT)-4/5 plays a crucial role during development, maintenance of the adult brain, and its adaptation to injury or pathological conditions. In spite of this, very little is known about the mechanisms that regulate its expression. Here, we show that forskolin (Fk) rapidly stimulates the expression of both the full-length and truncated trkB isoforms in primary cultures of cortical neurons. Gel shift assays and transient transfection experiments demonstrate that this activation occurs via a protein kinase A (PKA)/cyclic AMP-responsive element-binding protein (CREB)-dependent mechanism. Activated CREB binds to the second cyclic AMP (cAMP)-responsive element (CRE) of the two CRE sites located within the P2 promoter of the trkB gene, which is able to confer cAMP responsiveness to a heterologous promoter. Our results illustrate that the trkB gene is a target for CREB regulation and explain the increase of trkB expression produced in different adaptative responses of the nervous system where CREB is participating.


Assuntos
Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/fisiologia , Regulação da Expressão Gênica/fisiologia , Neurônios/fisiologia , Receptor trkB/biossíntese , Transdução de Sinais/fisiologia , Animais , Células Cultivadas , Córtex Cerebral/efeitos dos fármacos , Córtex Cerebral/fisiologia , Colforsina/farmacologia , Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/biossíntese , Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/genética , Relação Dose-Resposta a Droga , Regulação da Expressão Gênica/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Ratos , Ratos Wistar , Receptor trkB/genética , Transdução de Sinais/efeitos dos fármacos
6.
Neurochem Res ; 29(5): 903-22, 2004 May.
Artigo em Inglês | MEDLINE | ID: mdl-15139289

RESUMO

Thyroid hormone (T3) regulates brain development and function and in particular ensures normal myelination. Animal models and in vitro systems have been employed to demonstrate the effects of T3, which acts via nuclear hormone receptors. T3 receptors (TRs) are transcription factors that activate or suppress target gene expression, such as myelin basic protein (MBP), in a hormone-dependent or -independent fashion. Two distinct genes, TR alpha and TR beta, encode several receptor isoforms with specific functions. This overview summarizes current knowledge on the cellular expression and the role of these isoforms and also examines the action of T3 on oligodendrocyte lineage cell types at defined developmental stages. Re-expression of TRs and also that of other transcription factors in oligodendrocytes may constitute some of the metabolic changes required for succesfull remyelination in the adult central nervous system after demyelinating lesions.


Assuntos
Oligodendroglia/metabolismo , Isoformas de Proteínas/metabolismo , Receptores dos Hormônios Tireóideos/metabolismo , Animais , Linhagem da Célula , Oligodendroglia/citologia
7.
FEBS Lett ; 514(2-3): 309-14, 2002 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-11943172

RESUMO

Thyroid hormone (TH) regulates mitochondrial respiratory rate by activating coordinated transcription in the nucleus and mitochondria. Whereas TH activates transcription of mitochondrial genes directly, the activation of nuclear-encoded mitochondrial genes is probably executed by indirect unknown mechanisms. Nuclear respiratory factors (NRF)-1 and GA-binding protein (BP)/NRF-2 may function as transacting genes, but regulation of these genes by TH is not demonstrated. We show that TH administration to hypothyroid rats promptly increases GABP/NRF-2 alpha-subunit mRNA levels in the liver, without significant changes in beta, gamma subunits. In run-on and time-course experiments, the transcription rate and protein levels increased three-fold in response to TH, indicating GABP/NRF-2 transcriptional regulation. The results also support the notion that ATP synthase beta-subunit is regulated by TH through the indirect activation of GABP/NRF-2.


Assuntos
Proteínas de Ligação a DNA/metabolismo , Fígado/efeitos dos fármacos , Proteínas Mitocondriais , Fatores de Transcrição/metabolismo , Transcrição Gênica/efeitos dos fármacos , Tri-Iodotironina/administração & dosagem , Complexos de ATP Sintetase/genética , Complexos de ATP Sintetase/metabolismo , Animais , Proteínas de Ligação a DNA/genética , Esquema de Medicação , Fator de Transcrição de Proteínas de Ligação GA , Regulação da Expressão Gênica/efeitos dos fármacos , Regulação da Expressão Gênica/fisiologia , Hipotireoidismo/tratamento farmacológico , Hipotireoidismo/metabolismo , Injeções Intraperitoneais , Fígado/metabolismo , Masculino , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Subunidades Proteicas , RNA Mensageiro/metabolismo , Ratos , Ratos Wistar , Fatores de Tempo , Fatores de Transcrição/genética
8.
J Neurosci Res ; 67(1): 106-13, 2002 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-11754086

RESUMO

Double and triple immunocytochemistry with stage-specific markers and specific antireceptor antibodies was used to study expression of nuclear thyroid hormone receptor (TR) isoforms in cultured mouse oligodendrocytes. To evaluate the coexpression of each TR isoform, antibodies were raised in rabbits and mice against specific regions of alpha1-TR and alpha2-TR common to both alpha isoforms and beta1-TR. Their specificities were assessed by Western blotting and by immunocytochemistry on rat hepatocytes. Oligodendrocyte subpopulations were found to coexpress the alpha- and beta1-TR epitopes at defined developmental stages. Both alpha- and beta1-TR isoforms are colocalized in oligodendrocytes during an early stage identified by the marker OL-1, before 2',3'-cyclic nucleotide 3'-phosphohydrolase is expressed. Expression of beta1-TR varies during maturation, and that of alpha-TR decreases during terminal maturation.


Assuntos
Diferenciação Celular/fisiologia , Sistema Nervoso Central/embriologia , Sistema Nervoso Central/crescimento & desenvolvimento , Proteínas de Ligação a DNA , Oligodendroglia/metabolismo , Receptores dos Hormônios Tireóideos/metabolismo , Células-Tronco/metabolismo , Hormônios Tireóideos/metabolismo , Envelhecimento/fisiologia , Animais , Especificidade de Anticorpos , Fatores de Transcrição Hélice-Alça-Hélice Básicos , Células Cultivadas , Sistema Nervoso Central/citologia , Técnicas de Cocultura , Regulação da Expressão Gênica/fisiologia , Imuno-Histoquímica , Camundongos , Proteínas da Mielina , Glicoproteína Associada a Mielina/metabolismo , Glicoproteína Mielina-Oligodendrócito , Proteínas do Tecido Nervoso/metabolismo , Oligodendroglia/citologia , Isoformas de Proteínas/metabolismo , Ratos , Células-Tronco/citologia
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...