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1.
J Neurosci ; 2022 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-35882556

RESUMO

The activation of self-destructive cellular programs helps sculpt the nervous system during development, but the molecular mechanisms used are not fully understood. Prior studies have investigated the role of the APP in the developmental degeneration of sensory neurons with contradictory results. In this work, we sought to elucidate the impact of APP deletion in the development of the sensory nervous system in vivo and in vitro. Our in vivo data show an increase in the number of sciatic nerve axons in adult male and female APP-null mice, consistent with the hypothesis that APP plays a pro-degenerative role in the development of peripheral axons. In vitro, we show that genetic deletion of APP delays axonal degeneration triggered by nerve growth factor deprivation, indicating that APP does play a pro-degenerative role. Interestingly, APP depletion does not affect caspase-3 levels but significantly attenuates the rise of axoplasmic Ca2+ that occurs during degeneration. We examined intracellular Ca2+ mechanisms that could be involved and found that APP-null DRG neurons had increased Ca2+ levels within the endoplasmic reticulum and enhanced store-operated Ca2+ entry. We also observed that DRG axons lacking APP have more mitochondria than their WT counterparts, but these display a lower mitochondrial membrane potential. Finally, we present evidence that APP deficiency causes an increase in mitochondrial Ca2+ buffering capacity. Our results support the hypothesis that APP plays a pro-degenerative role in the developmental degeneration of DRG sensory neurons, and unveil the importance of APP in the regulation of calcium signaling in sensory neurons.Significance Statement:The nervous system goes through a phase of pruning and programmed neuronal cell death during development to reach maturity. In such context, the role played by the APP in the peripheral nervous system has been controversial, ranging from pro-survival to pro-degenerative. Here we present evidence in vivo and in vitro supporting the pro-degenerative role of APP, demonstrating the ability of APP to alter intracellular Ca2+ homeostasis and mitochondria, critical players of programmed cell death. This work provides a better understanding of the physiological function of APP and its implication in developmental neuronal death in the nervous system.

2.
Immunity ; 30(6): 789-801, 2009 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-19464198

RESUMO

Cellular inhibitor of apoptosis proteins (cIAPs) block apoptosis, but their physiological functions are still under investigation. Here, we report that cIAP1 and cIAP2 are E3 ubiquitin ligases that are required for receptor-interacting protein 2 (RIP2) ubiquitination and for nucleotide-binding and oligomerization (NOD) signaling. Macrophages derived from Birc2(-/-) or Birc3(-/-) mice, or colonocytes depleted of cIAP1 or cIAP2 by RNAi, were defective in NOD signaling and displayed sharp attenuation of cytokine and chemokine production. This blunted response was observed in vivo when Birc2(-/-) and Birc3(-/-) mice were challenged with NOD agonists. Defects in NOD2 signaling are associated with Crohn's disease, and muramyl dipeptide (MDP) activation of NOD2 signaling protects mice from experimental colitis. Here, we show that administration of MDP protected wild-type but not Ripk2(-/-) or Birc3(-/-) mice from colitis, confirming the role of the cIAPs in NOD2 signaling in vivo. This discovery provides therapeutic opportunities in the treatment of NOD-dependent immunologic and inflammatory diseases.


Assuntos
Imunidade Inata , Proteínas Inibidoras de Apoptose/metabolismo , Proteína Adaptadora de Sinalização NOD1/metabolismo , Proteína Adaptadora de Sinalização NOD2/metabolismo , Proteína Serina-Treonina Quinases de Interação com Receptores/metabolismo , Acetilmuramil-Alanil-Isoglutamina/farmacologia , Animais , Apoptose/imunologia , Proteína 3 com Repetições IAP de Baculovírus , Colite/enzimologia , Colite/imunologia , Colite/patologia , Citocinas/imunologia , Citocinas/metabolismo , Proteínas Inibidoras de Apoptose/genética , Proteínas Inibidoras de Apoptose/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteína Adaptadora de Sinalização NOD1/agonistas , Proteína Adaptadora de Sinalização NOD1/imunologia , Proteína Adaptadora de Sinalização NOD2/agonistas , Proteína Adaptadora de Sinalização NOD2/imunologia , Proteína Serina-Treonina Quinase 2 de Interação com Receptor , Proteína Serina-Treonina Quinases de Interação com Receptores/genética , Proteína Serina-Treonina Quinases de Interação com Receptores/imunologia , Receptores de Reconhecimento de Padrão/agonistas , Receptores de Reconhecimento de Padrão/imunologia , Receptores de Reconhecimento de Padrão/metabolismo , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/imunologia , Ubiquitina-Proteína Ligases , Ubiquitinação/imunologia
3.
J Cell Sci ; 128(3): 447-59, 2015 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-25472715

RESUMO

The p75 neurotrophin receptor (p75NTR, also known as tumor necrosis factor receptor superfamily member 16) is implicated in diverse cellular events, but fundamental aspects of its signaling mechanisms remain unclear. To address this, we have established a novel bioassay to characterize signaling cascades activated by p75NTR. We show that in COS7 cells, p75NTR expression causes a large increase in cell surface area that relies on the activation of Rac1, and we demonstrate that the p75NTR-dependent COS7 phenotype is dependent on ADAM17- and c-secretase-dependent cleavage of p75NTR and generation of the p75NTR intracellular domain (p75NTRICD). We show that the p75NTR adaptor protein NRAGE (also known as MAGED1) acts downstream of the p75NTRICD in this cascade and, through a yeast two-hybrid screen, identify NEDD9, a Cas family adaptor protein, as a novel NRAGE-binding partner that mediates p75NTR-dependent Rac1 activation and cell spreading. Our results demonstrate a crucial role for p75NTR cleavage in small GTPase activation and define a novel Rac1 activation pathway involving the p75NTRICD, NRAGE andNEDD9.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Antígenos de Neoplasias/metabolismo , Membrana Celular/metabolismo , Proteínas de Neoplasias/metabolismo , Fosfoproteínas/metabolismo , Receptor de Fator de Crescimento Neural/metabolismo , Proteínas rac1 de Ligação ao GTP/metabolismo , Proteínas ADAM/genética , Proteínas ADAM/metabolismo , Proteína ADAM17 , Proteínas Adaptadoras de Transdução de Sinal/genética , Secretases da Proteína Precursora do Amiloide/metabolismo , Animais , Antígenos de Neoplasias/genética , Células COS , Linhagem Celular , Movimento Celular/fisiologia , Chlorocebus aethiops , Proteínas do Citoesqueleto/metabolismo , Ativação Enzimática , Células HEK293 , Humanos , Proteínas de Neoplasias/genética , Fosfoproteínas/genética , Interferência de RNA , RNA Interferente Pequeno , Transdução de Sinais , Técnicas do Sistema de Duplo-Híbrido
4.
FASEB J ; 30(9): 3083-90, 2016 09.
Artigo em Inglês | MEDLINE | ID: mdl-27189977

RESUMO

Hippocampal long-term depression (LTD) is an active form of synaptic plasticity that is necessary for consolidation of spatial memory, contextual fear memory, and novelty acquisition. Recent studies have shown that caspases (CASPs) play an important role in NMDA receptor-dependent LTD and are involved in postsynaptic remodeling and synaptic maturation. In the present study, we examined the role of X-linked inhibitor of apoptosis (XIAP), a putative endogenous CASP inhibitor, in synaptic plasticity in the hippocampus. Analysis in acute brain slices and in cultured hippocampal neurons revealed that XIAP deletion increases CASP-3 activity, enhances α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor internalization, sharply increases LTD, and significantly reduces synapse density. In vivo behaviors related to memory were also altered in XIAP(-/-) mice, with faster acquisition of spatial object location and increased fear memory observed. Together, these results indicate that XIAP plays an important physiologic role in regulating sublethal CASP-3 activity within central neurons and thereby facilitates synaptic plasticity and memory acquisition.-Gibon, J., Unsain, N., Gamache, K., Thomas, R. A., De Leon, A., Johnstone, A., Nader, K., Séguéla, P., Barker, P. A. The X-linked inhibitor of apoptosis regulates long-term depression and learning rate.


Assuntos
Regulação da Expressão Gênica/fisiologia , Proteínas Inibidoras de Apoptose/metabolismo , Memória/fisiologia , Plasticidade Neuronal/fisiologia , Animais , Caspase 3/genética , Caspase 3/metabolismo , Hipocampo/citologia , Hipocampo/fisiologia , Proteínas Inibidoras de Apoptose/genética , Masculino , Camundongos , Camundongos Knockout , Neurônios/fisiologia
5.
EMBO Rep ; 16(1): 79-86, 2015 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-25427558

RESUMO

Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most common cause of dominant-inherited Parkinson's disease (PD), and yet we do not fully understand the physiological function(s) of LRRK2. Various components of the clathrin machinery have been recently found mutated in familial forms of PD. Here, we provide molecular insight into the association of LRRK2 with the clathrin machinery. We report that through its GTPase domain, LRRK2 binds directly to clathrin-light chains (CLCs). Using genome-edited HA-LRRK2 cells, we localize LRRK2 to endosomes on the degradative pathway, where it partially co-localizes with CLCs. Knockdown of CLCs and/or LRRK2 enhances the activation of the small GTPase Rac1, leading to alterations in cell morphology, including the disruption of neuronal dendritic spines. In Drosphila, a minimal rough eye phenotype caused by overexpression of Rac1, is dramatically enhanced by loss of function of CLC and LRRK2 homologues, confirming the importance of this pathway in vivo. Our data identify a new pathway in which CLCs function with LRRK2 to control Rac1 activation on endosomes, providing a new link between the clathrin machinery, the cytoskeleton and PD.


Assuntos
Cadeias Leves de Clatrina/metabolismo , Endossomos/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas rac1 de Ligação ao GTP/metabolismo , Animais , Animais Geneticamente Modificados , Sequência de Bases , Encéfalo/citologia , Encéfalo/metabolismo , Células COS , Células Cultivadas , Chlorocebus aethiops , Cadeias Leves de Clatrina/genética , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Olho/metabolismo , Olho/patologia , Técnicas de Silenciamento de Genes , Humanos , Serina-Treonina Proteína Quinase-2 com Repetições Ricas em Leucina , Dados de Sequência Molecular , Neurônios/metabolismo , Neurônios/patologia , Proteínas Serina-Treonina Quinases/genética , Estrutura Terciária de Proteína , Ratos , Proteínas rac1 de Ligação ao GTP/genética
6.
Mol Cell Neurosci ; 75: 81-92, 2016 09.
Artigo em Inglês | MEDLINE | ID: mdl-27449758

RESUMO

Recent findings indicate that the mechanisms that drive reshaping of the nervous system are aberrantly activated in epilepsy and several neurodegenerative diseases. The recurrent seizures in epilepsy, particularly in the condition called status epilepticus, can cause permanent neurological damage, resulting in cognitive dysfunction and other serious neurological conditions. In this study, we used an in vitro model of status epilepticus to examine the role of calpain in the degeneration of hippocampal neurons. We grew neurons on a culture system that allowed studying the dendritic and axonal domains separately from the cell bodies. We found that a recently characterized calpain substrate, the neurotrophin receptor TrkB, is cleaved in the dendritic and axonal domain of neurons committed to die, and this constitutes an early step in the neuronal degeneration process. While the full-length TrkB (TrkB-FL) levels decreased, the truncated form of TrkB (Tc TrkB-FL) concurrently increased, leading to a TrkB-FL/Tc TrkB-FL imbalance, which is thought to be causally linked to neurodegeneration. We further show that the treatment with N-acetyl-Leu-Leu-norleucinal, a specific calpain activity blocker, fully protects the neuronal processes from degeneration, prevents the TrkB-FL/Tc TrkB-FL imbalance, and provides full neuroprotection. Moreover, the use of the TrkB antagonist ANA 12 at the time when the levels of TrkB-FL were significantly decreased, totally blocked neuronal death, suggesting that Tc TrkB-FL may have a role in neuronal death. These results indicate that the imbalance of these neurotrophins receptors plays a key role in neurite degeneration induced by seizures.


Assuntos
Calpaína/metabolismo , Neurônios/metabolismo , Receptor trkB/metabolismo , Animais , Cálcio/metabolismo , Calpaína/antagonistas & inibidores , Morte Celular , Células Cultivadas , Hipocampo/citologia , Leupeptinas/farmacologia , Neurônios/citologia , Neurônios/efeitos dos fármacos , Inibidores de Proteases/farmacologia , Proteólise , Ratos , Ratos Wistar , Receptor trkB/antagonistas & inibidores , Estado Epiléptico/metabolismo
7.
Genesis ; 54(12): 605-612, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-27775873

RESUMO

The Neurotrophin receptor associated death domain gene (Nradd/Nrh2/Plaidd) is a type I transmembrane protein with a unique and short N-terminal extracellular domain and a transmembrane and intracellular domain that bears high similarity to the p75 neurotrophin receptor (p75NTR/Ngfr). Initial studies suggested that NRADD regulates neurotrophin signaling but very little is known about its physiological roles. We have generated and characterized NRADD conditional and germ-line null mouse lines. These mice are viable and fertile and dont show evident abnormalities. However, NRADD deletion results in an increase in the proportion of dorsal root ganglion neurons expressing p75NTR. The NRADD conditional and complete knockout mouse lines generated are new and useful tools to study the physiological roles of NRADD. Birth Defects Research (Part A) 106:605-612, 2016. © 2016 Wiley Periodicals, Inc.


Assuntos
Glicoproteínas de Membrana/genética , Fatores de Crescimento Neural/genética , Receptores de Morte Celular/genética , Receptores de Fator de Crescimento Neural/genética , Animais , Apoptose/genética , Linhagem Celular , Gânglios Espinais/metabolismo , Camundongos , Camundongos Knockout , Neurônios/metabolismo , Homologia de Sequência de Aminoácidos , Transdução de Sinais
8.
J Neurosci ; 35(26): 9741-53, 2015 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-26134656

RESUMO

Persistent firing of entorhinal cortex (EC) pyramidal neurons is a key component of working and spatial memory. We report here that a pro-brain-derived neurotrophic factor (proBDNF)-dependent p75NTR signaling pathway plays a major role in excitability and persistent activity of pyramidal neurons in layer V of the EC. Using electrophysiological recordings, we show that proBDNF suppresses persistent firing in entorhinal slices from wild-type mice but not from p75NTR-null mice. Conversely, function-blocking proBDNF antibodies enhance excitability of pyramidal neurons and facilitate their persistent firing, and acute exposure to function-blocking p75NTR antibodies results in enhanced firing activity of pyramidal neurons. Genetic deletion of p75NTR specifically in neurons or during adulthood also induces enhanced excitability and persistent activity, indicating that the proBDNF-p75NTR signaling cascade functions within adult neurons to inhibit pyramidal activity. Phosphatidylinositol 4,5-bisphosphate (PIP2)-sensitive transient receptor potential canonical channels play a critical role in mediating persistent firing in the EC and we hypothesized that proBDNF-dependent p75NTR activation regulates PIP2 levels. Accordingly, proBDNF decreases cholinergic calcium responses in cortical neurons and affects carbachol-induced depletion of PIP2. Further, we show that the modulation of persistent firing by proBDNF relies on a p75NTR-Rac1-PI4K pathway. The hypothesis that proBDNF and p75NTR maintain network homeostasis in the adult CNS was tested in vivo and we report that p75NTR-null mice show improvements in working memory but also display an increased propensity for severe seizures. We propose that the proBDNF-p75NTR axis controls pyramidal neuron excitability and persistent activity to balance EC performance with the risk of runaway activity. SIGNIFICANCE STATEMENT: Persistent firing of entorhinal cortex (EC) pyramidal neurons is required for working memory. We report here that pro-brain-derived neurotrophic factor (proBDNF) activates p75NTR to induce a Rac1-dependent and phosphatidylinositol 4,5-bisphosphate-dependent signaling cascade that suppresses persistent activity. Conversely, using loss-of-function approaches, we find that endogenous proBDNF or p75NTR activation strongly decreases pyramidal neuron excitability and persistent firing, suggesting that a physiological role of this proBDNF-p75NTR cascade may be to regulate working memory in vivo. Consistent with this, mice rendered null for p75NTR during adulthood show improvements in working memory but also display an increased propensity for severe seizures. We propose that by attenuating EC network performance, the proBDNF-p75NTR signaling cascade reduces the probability of epileptogenesis.


Assuntos
Potenciais de Ação/fisiologia , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Córtex Cerebral/citologia , Neurônios/fisiologia , Precursores de Proteínas/metabolismo , Receptores de Fator de Crescimento Neural/metabolismo , Aminoquinolinas/farmacologia , Animais , Fator Neurotrófico Derivado do Encéfalo/genética , Fator Neurotrófico Derivado do Encéfalo/farmacologia , Carbacol/farmacologia , Células Cultivadas , Agonistas Colinérgicos/farmacologia , Convulsivantes/toxicidade , Modelos Animais de Doenças , Embrião de Mamíferos , Feminino , Técnicas In Vitro , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Pentilenotetrazol/toxicidade , Fosfolipase C delta/genética , Fosfolipase C delta/metabolismo , Pilocarpina/toxicidade , Precursores de Proteínas/genética , Precursores de Proteínas/farmacologia , Pirimidinas/farmacologia , Receptores de Fator de Crescimento Neural/genética , Receptores de Fator de Crescimento Neural/imunologia , Convulsões/induzido quimicamente , Convulsões/genética , Convulsões/fisiopatologia
9.
J Neurosci ; 35(35): 12088-102, 2015 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-26338321

RESUMO

Loss of vision in glaucoma results from the selective death of retinal ganglion cells (RGCs). Tumor necrosis factor α (TNFα) signaling has been linked to RGC damage, however, the mechanism by which TNFα promotes neuronal death remains poorly defined. Using an in vivo rat glaucoma model, we show that TNFα is upregulated by Müller cells and microglia/macrophages soon after induction of ocular hypertension. Administration of XPro1595, a selective inhibitor of soluble TNFα, effectively protects RGC soma and axons. Using cobalt permeability assays, we further demonstrate that endogenous soluble TNFα triggers the upregulation of Ca(2+)-permeable AMPA receptor (CP-AMPAR) expression in RGCs of glaucomatous eyes. CP-AMPAR activation is not caused by defects in GluA2 subunit mRNA editing, but rather reflects selective downregulation of GluA2 in neurons exposed to elevated eye pressure. Intraocular administration of selective CP-AMPAR blockers promotes robust RGC survival supporting a critical role for non-NMDA glutamate receptors in neuronal death. Our study identifies glia-derived soluble TNFα as a major inducer of RGC death through activation of CP-AMPARs, thereby establishing a novel link between neuroinflammation and cell loss in glaucoma. SIGNIFICANCE STATEMENT: Tumor necrosis factor α (TNFα) has been implicated in retinal ganglion cell (RGC) death, but how TNFα exerts this effect is poorly understood. We report that ocular hypertension, a major risk factor in glaucoma, upregulates TNFα production by Müller cells and microglia. Inhibition of soluble TNFα using a dominant-negative strategy effectively promotes RGC survival. We find that TNFα stimulates the expression of calcium-permeable AMPA receptors (CP-AMPAR) in RGCs, a response that does not depend on abnormal GluA2 mRNA editing but on selective downregulation of the GluA2 subunit by these neurons. Consistent with this, CP-AMPAR blockers promote robust RGC survival supporting a critical role for non-NMDA glutamate receptors in glaucomatous damage. This study identifies a novel mechanism by which glia-derived soluble TNFα modulates neuronal death in glaucoma.


Assuntos
Cálcio/metabolismo , Glaucoma/patologia , Receptores de AMPA/metabolismo , Células Ganglionares da Retina/efeitos dos fármacos , Fator de Necrose Tumoral alfa/metabolismo , Regulação para Cima/efeitos dos fármacos , Animais , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Morte Celular/efeitos dos fármacos , Colina O-Acetiltransferase/metabolismo , Cobalto/metabolismo , Modelos Animais de Doenças , Células Ependimogliais/efeitos dos fármacos , Células Ependimogliais/metabolismo , Glaucoma/induzido quimicamente , Masculino , Microglia/efeitos dos fármacos , Microglia/metabolismo , Ratos , Receptores de AMPA/genética , Receptores Tipo I de Fatores de Necrose Tumoral/metabolismo , Receptores Tipo II do Fator de Necrose Tumoral/metabolismo , Solução Salina Hipertônica/toxicidade , Fator de Necrose Tumoral alfa/farmacologia , Regulação para Cima/fisiologia
10.
Rapid Commun Mass Spectrom ; 30(2): 293-300, 2016 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-26689159

RESUMO

RATIONALE: Current studies which use the oxygen isotope composition from diatom silica (δ(18) Odiatom ) as a palaeoclimate proxy assume that the δ(18) Odiatom value reflects the isotopic composition of the water in which the diatom formed. However, diatoms dissolve post mortem, preferentially losing less silicified structures in the water column and during/after burial into sediments. The impact of dissolution on δ(18) Odiatom values and potential misinterpretation of the palaeoclimate record are evaluated. METHODS: Diatom frustules covering a range of ages (6 samples from the Miocene to the Holocene), environments and species were exposed to a weak alkaline solution for 48 days at two temperatures (20 °C and 4 °C), mimicking natural dissolution post mucilage removal. Following treatment, dissolution was assessed using scanning electron microscope images and a qualitative diatom dissolution index. The diatoms were subsequently analysed for their δ(18) O values using step-wise fluorination and isotope ratio mass spectrometry. RESULTS: Variable levels of diatom dissolution were observed between the six samples; in all cases higher temperatures resulted in more frustule degradation. Dissolution was most evident in younger samples, probably as a result of the more porous nature of the silica. The degree of diatom dissolution does not directly equate to changes in the isotope ratios; the δ(18) Odiatom value was, however, lower after dissolution, but in only half the samples was this reduction outside the analytical error (2σ analytical error = 0.46‰). CONCLUSIONS: We have shown that dissolution can have a small negative impact on δ(18) Odiatom values, causing reductions of up to 0.59‰ beyond analytical error (0.46‰) at natural environmental temperatures. These findings need to be considered in palaeoenvironmental reconstructions using δ(18) Odiatom values, especially when interpreting variations in these values of <1‰.


Assuntos
Diatomáceas/química , Fósseis , Isótopos de Oxigênio/análise , Sedimentos Geológicos , Microscopia Eletrônica de Varredura , Fatores de Tempo
11.
Bioorg Med Chem ; 24(19): 4759-4765, 2016 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-27567078

RESUMO

Mature neurotrophins as well as their pro forms are critically involved in the regulation of neuronal functions. They are signaling through three distinct types of receptors: tropomyosin receptor kinase family (TrkA/B/C), p75 neurotrophin receptor (p75(NTR)) and sortilin. Aberrant expression of p75(NTR) in the CNS is implicated in a variety of neurodegenerative diseases, including Alzheimer's disease. The goal of this work was to evaluate one of the very few reported p75(NTR) small molecule ligands as a lead compound for development of novel PET radiotracers for in vivo p75(NTR) imaging. Here we report that previously described ligand LM11A-24 shows significant inhibition of carbachol-induced persistent firing (PF) of entorhinal cortex (EC) pyramidal neurons in wild-type mice via selective interaction with p75(NTR). Based on this electrophysiological assay, the compound has very high potency with an EC50<10nM. We optimized the radiosynthesis of [(11)C]LM11A-24 as the first attempt to develop PET radioligand for in vivo imaging of p75(NTR). Despite some weak interaction with CNS tissues, the radiolabeled compound showed unfavorable in vivo profile presumably due to high hydrophilicity.


Assuntos
Cafeína/análogos & derivados , Tomografia por Emissão de Pósitrons/métodos , Receptor de Fator de Crescimento Neural/metabolismo , Animais , Cafeína/metabolismo , Cafeína/farmacocinética , Radioisótopos de Carbono/metabolismo , Radioisótopos de Carbono/farmacocinética , Sistema Nervoso Central/diagnóstico por imagem , Sistema Nervoso Central/metabolismo , Camundongos Endogâmicos C57BL
12.
Mol Cell ; 30(6): 689-700, 2008 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-18570872

RESUMO

The inhibitor of apoptosis (IAP) family of proteins enhances cell survival through mechanisms that remain uncertain. In this report, we show that cIAP1 and cIAP2 promote cancer cell survival by functioning as E3 ubiquitin ligases that maintain constitutive ubiquitination of the RIP1 adaptor protein. We demonstrate that AEG40730, a compound modeled on BIR-binding tetrapeptides, binds to cIAP1 and cIAP2, facilitates their autoubiquitination and proteosomal degradation, and causes a dramatic reduction in RIP1 ubiquitination. We show that cIAP1 and cIAP2 directly ubiquitinate RIP1 and induce constitutive RIP1 ubiquitination in cancer cells and demonstrate that constitutively ubiquitinated RIP1 associates with the prosurvival kinase TAK1. When deubiquitinated by AEG40730 treatment, RIP1 binds caspase-8 and induces apoptosis. These findings provide insights into the function of the IAPs and provide new therapeutic opportunities in the treatment of cancer.


Assuntos
Proteínas Inibidoras de Apoptose/metabolismo , Complexo de Proteínas Formadoras de Poros Nucleares/metabolismo , Proteínas de Ligação a RNA/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Ubiquitina/metabolismo , Proteína 3 com Repetições IAP de Baculovírus , Caspase 8/metabolismo , Morte Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Ativação Enzimática/efeitos dos fármacos , Feminino , Humanos , Neoplasias Ovarianas , Sulfonamidas/farmacologia
13.
J Biol Chem ; 289(12): 8067-85, 2014 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-24519935

RESUMO

Malignant gliomas are highly invasive, proliferative, and resistant to treatment. Previously, we have shown that p75 neurotrophin receptor (p75NTR) is a novel mediator of invasion of human glioma cells. However, the role of p75NTR in glioma proliferation is unknown. Here we used brain tumor-initiating cells (BTICs) and show that BTICs express neurotrophin receptors (p75NTR, TrkA, TrkB, and TrkC) and their ligands (NGF, brain-derived neurotrophic factor, and neurotrophin 3) and secrete NGF. Down-regulation of p75NTR significantly decreased proliferation of BTICs. Conversely, exogenouous NGF stimulated BTIC proliferation through α- and γ-secretase-mediated p75NTR cleavage and release of its intracellular domain (ICD). In contrast, overexpression of the p75NTR ICD induced proliferation. Interestingly, inhibition of Trk signaling blocked NGF-stimulated BTIC proliferation and p75NTR cleavage, indicating a role of Trk in p75NTR signaling. Further, blocking p75NTR cleavage attenuated Akt activation in BTICs, suggesting role of Akt in p75NTR-mediated proliferation. We also found that p75NTR, α-secretases, and the four subunits of the γ-secretase enzyme were elevated in glioblastoma multiformes patients. Importantly, the ICD of p75NTR was commonly found in malignant glioma patient specimens, suggesting that the receptor is activated and cleaved in patient tumors. These results suggest that p75NTR proteolysis is required for BTIC proliferation and is a novel potential clinical target.


Assuntos
Secretases da Proteína Precursora do Amiloide/metabolismo , Neoplasias Encefálicas/metabolismo , Encéfalo/patologia , Glioma/metabolismo , Células-Tronco Neoplásicas/patologia , Fatores de Crescimento Neural/metabolismo , Receptor de Fator de Crescimento Neural/metabolismo , Encéfalo/metabolismo , Neoplasias Encefálicas/genética , Neoplasias Encefálicas/patologia , Linhagem Celular Tumoral , Proliferação de Células , Técnicas de Silenciamento de Genes , Glioma/genética , Glioma/patologia , Humanos , Mutação , Células-Tronco Neoplásicas/citologia , Células-Tronco Neoplásicas/metabolismo , Receptor de Fator de Crescimento Neural/genética
14.
J Neurosci ; 33(5): 2205-16, 2013 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-23365256

RESUMO

The transcription factor p53 mediates neuronal death in a variety of stress-related and neurodegenerative conditions. The proapoptotic activity of p53 is tightly regulated by the apoptosis-stimulating proteins of p53 (ASPP) family members: ASPP1 and ASPP2. However, whether ASPP1/2 play a role in the regulation of p53-dependent neuronal death in the CNS is currently unknown. To address this, we asked whether ASPP1/2 contribute to the death of retinal ganglion cells (RGCs) using in vivo models of acute optic nerve damage in mice and rats. Here, we show that p53 is activated in RGCs soon after injury and that axotomy-induced RGC death is attenuated in p53 heterozygote and null mice. We demonstrate that ASPP1/2 proteins are abundantly expressed by injured RGCs, and that short interfering (si)RNA-based ASPP1 or ASPP2 knockdown promotes robust RGC survival. Comparative gene expression analysis revealed that siASPP-mediated downregulation of p53-upregulated-modulator-of-apoptosis (PUMA), Fas/CD95, and Noxa depends on p53 transcriptional activity. Furthermore, siRNA against PUMA or Fas/CD95 confers neuroprotection, demonstrating a functional role for these p53 targets in RGC death. Our study demonstrates a novel role for ASPP1 and ASPP2 in the death of RGCs and provides evidence that blockade of the ASPP-p53 pathway is beneficial for central neuron survival after axonal injury.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Proteínas Reguladoras de Apoptose/metabolismo , Morte Celular/fisiologia , Células Ganglionares da Retina/metabolismo , Proteína Supressora de Tumor p53/metabolismo , Proteínas Supressoras de Tumor/metabolismo , Receptor fas/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/genética , Animais , Proteínas Reguladoras de Apoptose/genética , Axônios/metabolismo , Regulação para Baixo , Feminino , Camundongos , Camundongos Knockout , Ratos , Ratos Sprague-Dawley , Transdução de Sinais/fisiologia , Ativação Transcricional , Proteína Supressora de Tumor p53/genética , Proteínas Supressoras de Tumor/genética , Receptor fas/genética
15.
J Neurochem ; 131(2): 190-205, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-24923428

RESUMO

Extracellular S100B dramatically increases after brain injury. While low S100B levels are neuroprotective, micromolar S100B levels have shown in vitro to activate microglia and facilitate neuronal death. In astrocytes, S100B exposure activates nuclear factor kappa B (NF-κB) and induces pro-inflammatory mediators. On microglia and neurons S100B effects are essentially mediated by receptor for advanced glycation end products (RAGE)/NF-κB, but it is not clear if these intracellular cascades are activated by different S100B levels in astrocytes and whether increased extracellular S100B is sufficient to induce reactive gliosis. A better understanding of these pathways is essential for developing successful strategies to preserve the beneficial S100B effects after brain injury. Here, we show that microglia-depleted cultured astrocytes exposed to S100B mimicked several features of reactive gliosis by activating RAGE/Rac-1-Cdc42, RAGE/Erk-Akt or RAGE/NF-κB-dependent pathways. S100B effects include RAGE/Rac1-Cdc42-dependent astroglial hypertrophy and facilitation of migration as well as increased mitosis. S100B exposure improved the astrocytic survival to oxidative stress, an effect that requires Erk/Akt. S100B also activates NF-κB in a dose-dependent manner; increases RAGE proximal promoter transcriptional activity and augmented endogenous RAGE expression. S100B-exposed astrocytes showed a pro-inflammatory phenotype with expression of Toll-like receptor 2 (TLR 2), inducible nitric oxide synthase (iNOS) and interleukin 1-beta (IL-1ß), and facilitated neuronal death induced by oxygen-glucose deprivation. In vivo, intracerebral infusion of S100B was enough to induce an astroglial reactive phenotype. Together, these findings demonstrate that extracellular S100B in the micromolar level activates different RAGE-dependent pathways that turn astrocytes into a pro-inflammatory and neurodegenerative phenotype. We propose that S100B turns astrocytes into a reactive phenotype in a RAGE-dependent manner but engaging different intracellular pathways. While both nanomolar and micromolar S100B turn astrocytes into a reactive phenotype, micromolar S100B induces a conversion into a pro-inflammatory-neurodegenerative profile that facilitates neuronal death of OGD-exposed neurons. We think that S100B/RAGE interaction is essential to expand reactive gliosis in the injured brain being a tempting target for limiting reactive gliosis to prevent the glial conversion into the neurodegenerative profile.


Assuntos
Astrócitos/metabolismo , Comunicação Autócrina/fisiologia , Gliose/metabolismo , Receptores Imunológicos/metabolismo , Subunidade beta da Proteína Ligante de Cálcio S100/administração & dosagem , Animais , Animais Recém-Nascidos , Astrócitos/efeitos dos fármacos , Comunicação Autócrina/efeitos dos fármacos , Bovinos , Células Cultivadas , Relação Dose-Resposta a Droga , Infusões Intraventriculares , Masculino , Ratos , Ratos Wistar , Receptor para Produtos Finais de Glicação Avançada
17.
Handb Exp Pharmacol ; 220: 193-221, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24668474

RESUMO

The neurotrophins play crucial roles regulating survival and apoptosis in the developing and injured nervous system. The four neurotrophins exert profound and crucial survival effects on developing peripheral neurons, and their expression and action is intimately tied to successful innervation of peripheral targets. In the central nervous system, they are dispensable for neuronal survival during development but support neuronal survival after lesion or other forms of injury. Neurotrophins also regulate apoptosis of both peripheral and central neurons, and we now recognize that there are regulatory advantages to having the same molecules regulate life and death decisions. This chapter examines the biological contexts in which these events take place and highlights the specific ligands, receptors, and signaling mechanisms that allow them to occur.


Assuntos
Apoptose , Sobrevivência Celular , Fatores de Crescimento Neural/fisiologia , Animais , Humanos , Fator de Crescimento Neural/fisiologia , Precursores de Proteínas/fisiologia , Receptor de Fator de Crescimento Neural/fisiologia , Receptor trkA/fisiologia
18.
Biochem J ; 443(2): 355-9, 2012 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-22332634

RESUMO

A recent study revealed that ES (embryonic stem) cell lines derived from the 129 murine strain carry an inactivating mutation within the caspase 11 gene (Casp4) locus [Kayagaki, Warming, Lamkanfi, Vande Walle, Louie, Dong, Newton, Qu, Liu, Heldens, Zhang, Lee, Roose-Girma and Dixit (2011) Nature 479, 117-121]. Thus, if 129 ES cells are used to target genes closely linked to caspase 11, the resulting mice might also carry the caspase 11 deficiency as a passenger mutation. In the present study, we examined the genetic loci of mice targeted for the closely linked c-IAP (cellular inhibitor of apoptosis) genes, which were generated in 129 ES cells, and found that, despite extensive backcrossing into a C57BL/6 background, c-IAP1(-/-) animals are also deficient in caspase 11. Consequently, data obtained from these mice should be re-evaluated in this new context.


Assuntos
Caspases/genética , Proteínas Inibidoras de Apoptose/metabolismo , Mutação , Animais , Caspases/metabolismo , Caspases Iniciadoras , Linhagem Celular , Ativação Enzimática , Proteínas Inibidoras de Apoptose/deficiência , Camundongos , Camundongos da Linhagem 129
19.
Proc Natl Acad Sci U S A ; 107(8): 3817-22, 2010 Feb 23.
Artigo em Inglês | MEDLINE | ID: mdl-20133718

RESUMO

Neurotrophin binding to the p75 neurotrophin receptor (p75(NTR)) activates neuronal apoptosis following adult central nervous system injury, but the underlying cellular mechanisms remain poorly defined. In this study, we show that the proform of nerve growth factor (proNGF) induces death of retinal ganglion cells in adult rodents via a p75(NTR)-dependent signaling mechanism. Expression of p75(NTR) in the adult retina is confined to Müller glial cells; therefore we tested the hypothesis that proNGF activates a non-cell-autonomous signaling pathway to induce retinal ganglion cell (RGC) death. Consistent with this, we show that proNGF induced robust expression of tumor necrosis factor alpha (TNFalpha) in Müller cells and that genetic or biochemical ablation of TNFalpha blocked proNGF-induced death of retinal neurons. Mice rendered null for p75(NTR), its coreceptor sortilin, or the adaptor protein NRAGE were defective in proNGF-induced glial TNFalpha production and did not undergo proNGF-induced retinal ganglion cell death. We conclude that proNGF activates a non-cell-autonomous signaling pathway that causes TNFalpha-dependent death of retinal neurons in vivo.


Assuntos
Apoptose , Fator de Crescimento Neural/metabolismo , Receptor de Fator de Crescimento Neural/metabolismo , Células Ganglionares da Retina/fisiologia , Fator de Necrose Tumoral alfa/fisiologia , Proteínas Adaptadoras de Transporte Vesicular/metabolismo , Animais , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Fator de Crescimento Neural/farmacologia , Ratos , Ratos Sprague-Dawley , Células Ganglionares da Retina/efeitos dos fármacos , Transdução de Sinais , Fator de Necrose Tumoral alfa/genética
20.
Proc Natl Acad Sci U S A ; 107(17): 7863-8, 2010 Apr 27.
Artigo em Inglês | MEDLINE | ID: mdl-20385823

RESUMO

Schizophrenia likely results from poorly understood genetic and environmental factors. We studied the gene encoding the synaptic protein SHANK3 in 285 controls and 185 schizophrenia patients with unaffected parents. Two de novo mutations (R1117X and R536W) were identified in two families, one being found in three affected brothers, suggesting germline mosaicism. Zebrafish and rat hippocampal neuron assays revealed behavior and differentiation defects resulting from the R1117X mutant. As mutations in SHANK3 were previously reported in autism, the occurrence of SHANK3 mutations in subjects with a schizophrenia phenotype suggests a molecular genetic link between these two neurodevelopmental disorders.


Assuntos
Proteínas de Transporte/genética , Mutação de Sentido Incorreto/genética , Proteínas do Tecido Nervoso/genética , Neurônios/citologia , Esquizofrenia/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Biologia Computacional , Primers do DNA/genética , Feminino , Humanos , Masculino , Repetições de Microssatélites/genética , Dados de Sequência Molecular , Linhagem , Ratos , Análise de Sequência de DNA , Peixe-Zebra
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