RESUMEN
This study demonstrates, for the first time, that loss of a single forkhead box class O (FoxO) transcription factor, can promote lymphomagenesis. Using two different mouse models, we show that FoxO3 has a significant tumour-suppressor function in the context of Myc-driven lymphomagenesis. Loss of FoxO3 significantly accelerated myeloid tumorigenesis in vavP-MYC10 transgenic mice and B lymphomagenesis in Eµ-myc transgenic mice. Tumour analysis indicated that the selective pressure for mutation of the p53 pathway during Eµ-myc lymphomagenesis was not altered. Frank tumours were preceded by elevated macrophage numbers in FoxO3(-/-) vavP-MYC10 mice but, surprisingly, pre-B-cell numbers were relatively normal in healthy young FoxO3(-/-)Eµ-myc mice. In vitro assays revealed enhanced survival capacity of Myc-driven cells lacking FoxO3, but no change in cell cycling was detected. The loss of FoxO3 may also be affecting other tumour-suppressive functions for which FoxO1/4 cannot fully compensate.
Asunto(s)
Carcinogénesis/genética , Factores de Transcripción Forkhead/genética , Linfoma de Células B/genética , Proteínas Proto-Oncogénicas c-myc/genética , Animales , Linfocitos B/patología , Línea Celular Tumoral , Proteína Forkhead Box O3 , Factores de Transcripción Forkhead/biosíntesis , Regulación Neoplásica de la Expresión Génica , Humanos , Linfoma de Células B/patología , Ratones , Ratones Transgénicos , Células Mieloides/patologíaRESUMEN
BACKGROUND: Platelet-activating factor (PAF) has been implicated in the pathology of neuropathic pain. Previous studies reported that PAF receptor (PAF-R) antagonists have varied anti-allodynia effects by route of administration and nerve injury models in rats. METHODS: The present study elucidated the effectiveness of PAF antagonists against neuropathic pain in four different models of peripheral nerve injury and provided insights into the mode of anti-allodynia action. RESULTS: PAF antagonists, TCV-309, BN 50739 and WEB 2086 by intravenous (i.v.) and oral administration have potent and long-lasting anti-allodynia action in mice neuropathic pain models. Treatment with PAF antagonists before surgery delayed the initiation of allodynia until the effects of these treatments were abolished. Intrathecal (i.t.) injection of the PAF antagonists and siRNA against PAF receptor ameliorated allodynia. I.t. injection of the glycine receptor (GlyR)α3 siRNA reduced the anti-allodynia effect of PAF antagonists. This evidence suggests that the anti-allodynia effect of PAF antagonists is at least in part mediated by spinal relief of PAF-induced dysfunction of GlyRα3. An analysis of the mode of anti-allodynia action of TCV-309 in vivo revealed a competitive action against PAF shortly after the injection of TCV-309, converting to a non-competitive action later. CONCLUSIONS: The present results revealed the effectiveness in anti-allodynia of PAF antagonists in different nerve injury models, and the unique mode of action; long-lasting anti-allodynia effects mediated by spinal GlyRα3 with a competitive manner at the initial stage and the following non-competitive manner of inhibition.
Asunto(s)
Neuralgia/tratamiento farmacológico , Traumatismos de los Nervios Periféricos/tratamiento farmacológico , Factor de Activación Plaquetaria/antagonistas & inhibidores , Animales , Modelos Animales de Enfermedad , Hiperalgesia/tratamiento farmacológico , Masculino , Ratones , Dimensión del Dolor/métodos , Glicoproteínas de Membrana Plaquetaria/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Médula Espinal/efectos de los fármacos , Médula Espinal/patologíaRESUMEN
Conversion of intestinal stem cells into tumor-initiating cells is an early step in Apc(Min)-induced polyposis. Wild-type p53-induced phosphatase 1 (Wip1)-dependent activation of a DNA damage response and p53 has a permanent role in suppression of stem cell conversion, and deletion of Wip1 lowers the tumor burden in Apc(Min) mice. Here we show that cyclin-dependent kinase inhibitor 2a, checkpoint kinase 2, and growth arrest and DNA damage gene 45a (Gadd45a) exert critical functions in the tumor-resistant phenotype of Wip1-deficient mice. We further identified Gadd45a as a haploinsufficient gene in the regulation of Wip1-dependent tumor resistance in mice. Gadd45a appears to function through its ability to activate the Jnk-dependent signaling pathway that in turn is a necessary mediator of the proapoptotic functions of p53 that respond to activation of the ß-catenin signaling pathway. We propose that silencing of Gadd45a is sufficient to override p53 activation in the presence of active ß-catenin under conditions of an enhanced DNA damage response.
Asunto(s)
Proteínas de Ciclo Celular/metabolismo , Proteínas Nucleares/metabolismo , Fosfoproteínas Fosfatasas/metabolismo , Animales , Apoptosis , Transformación Celular Neoplásica , Quinasa de Punto de Control 2 , Inhibidor p16 de la Quinasa Dependiente de Ciclina/metabolismo , Reparación del ADN , Genes APC , Poliposis Intestinal/metabolismo , Poliposis Intestinal/patología , Proteínas Quinasas JNK Activadas por Mitógenos/metabolismo , Ratones , Ratones Noqueados , Fosfoproteínas Fosfatasas/deficiencia , Fosfoproteínas Fosfatasas/genética , Proteína Fosfatasa 2C , Proteínas Serina-Treonina Quinasas/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Transducción de Señal , Células Madre/metabolismo , Proteína p53 Supresora de Tumor/metabolismo , beta Catenina/metabolismoRESUMEN
We used resonant soft x-ray scattering to study the chain ordering in Sr14Cu24O41 (SCO). We observed, for the first time, both the chain and ladder orders in SCO with the same probe. We found that the chain modulation in SCO is incommensurate with wave vector L_(c)=0.318, is strongly temperature (T) dependent, and is accompanied by a substantial hole modulation. By contrast, the chain modulation in a hole-depleted control sample La6Ca8Cu24O41 was commensurate (L_(c)=0.3), T independent, and purely structural. We conclude that the chain charge order in SCO is a 4k_(F) charge density wave stabilized by the misfit strain between the ladder and chain substructures.
RESUMEN
We report a resonant inelastic x-ray scattering study of charge excitations in the quasi-one-dimensional Mott insulator SrCuO2. We observe a continuum of low-energy excitations, the onset of which exhibits a small dispersion of approximately 0.4 eV. Within this continuum, a highly dispersive feature with a large sinusoidal dispersion (approximately 1.1 eV) is observed. We have also measured the optical conductivity, and studied the dynamic response of the extended Hubbard model with realistic parameters, using a dynamical density-matrix renormalization group method. In contrast to earlier work, we do not find a long-lived exciton, but rather these results suggest that the excitation spectrum comprises a holon-antiholon continuum together with a broad resonance.
RESUMEN
Raman measurements in the 1.5-20 cm(-1) energy range were performed on single crystals of Sr14-xCaxCu24O41. A quasielastic scattering peak (QEP) which softens with cooling is observed only in the polarization parallel to the ladder direction for samples with x=0, 8, and 12. The QEP is a Raman fingerprint of pinned collective density wave excitations screened by uncondensed carriers in the ladder structures. Our results suggest that transport in metallic samples, which is similar to transport in underdoped high-T(c) cuprates, is driven by a collective electronic response.
RESUMEN
A comparative analysis of electron energy-loss spectroscopy (EELS) spectra for the 1D insulating cuprate Sr2CuO3 with transferred momentum q--> axially and radially to the chain axis allows one to elucidate the structure of the charge transfer gap in in-chain response. It is determined by the superposition of two types of excitations with different magnitudes of dispersion. The low-energy response with q--> radially to the chain direction, but yet within the plane of CuO4 plaquettes, exhibits also a dispersionless peak near 2 eV. The theoretical simulation of the EELS data using exact diagonalizations of an appropriate extended Hubbard Hamiltonian for relevant clusters requires the explicit consideration of low-lying oxygen 2p pi states within the CuO4 plaquette plane beyond the standard pd sigma extended Hubbard model widely used for cuprates with corner-shared CuO4 plaquettes.
Asunto(s)
Apoptosis/fisiología , Embrión de Mamíferos/metabolismo , Proteínas/metabolismo , Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , Animales , Factor Apoptótico 1 Activador de Proteasas , Encéfalo/anomalías , Encéfalo/metabolismo , Línea Celular , Etiquetado Corte-Fin in Situ , Hígado/metabolismo , Ratones , Proteína bcl-XRESUMEN
We used transport and Raman scattering measurements to identify the insulating state of self-doped spin (1/2) two-leg ladders of Sr14Cu24O41 as a weakly pinned, sliding density wave with nonlinear conductivity and a giant dielectric response that persists to remarkably high temperatures.
RESUMEN
We report momentum-resolved charge excitations in a one-dimensional (1D) Mott insulator studied using high resolution inelastic x-ray scattering over the entire Brillouin zone for the first time. Excitations at the insulating gap edge are found to be highly dispersive (momentum dependent) compared to excitations observed in two-dimensional Mott insulators. The observed dispersion in 1D cuprates ( SrCuO2 and Sr2CuO3) is consistent with charge excitations involving holons which is unique to spin-1/2 quantum chain systems. These results point to the potential utility of momentum-resolved inelastic x-ray scattering in providing valuable information about electronic structure of strongly correlated insulators.
RESUMEN
The low-energy electronic structure of the nearly optimally doped trilayer cuprate superconductor Bi(2)Sr(2)Ca(2)Cu(3)O(10+delta) is investigated by angle-resolved photoemission spectroscopy. The normal state quasiparticle dispersion and Fermi surface and the superconducting d-wave gap and coherence peak are observed and compared with those of single- and bilayer systems. We find that both the superconducting gap magnitude and the relative coherence-peak intensity scale linearly with T(c) for various optimally doped materials.
RESUMEN
The two-magnon (2M) excitation at 3000 cm(-1) in Sr14Cu24O41 two-leg ladder is studied by Raman scattering. A slight anisotropy of the superexchange coupling J(perpendicular)/J(parallel) approximately 0.8 with J(parallel) = 110+/-20 meV is proposed from the analysis of the magnetic scattering. The resonant coupling across the charge transfer gap increases the 2M intensity by orders of magnitude. The anisotropy of Raman scattering is dependent upon the excitation energy. The 2M relaxation is found to be correlated with the temperature dependent electronic Raman continuum at low frequencies.
RESUMEN
Chimeric mice were prepared from embryonic stem cells transfected with IgH genes as transgenes and RAG-2-deficient blastocysts for the purpose of identifying the cis-acting elements responsible for the induction of somatic hypermutation. Among the three transgene constructs used, the V(H) promoter, the rearranged V(H)-D-J(H), an intron enhancer/matrix attachment region, and human Cmu were common to all, but the 3'-untranslated region in each construct was different. After immunization of mice with a T cell-dependent Ag, the distribution and frequency of hypermutation in transgenes were analyzed. The transgene lacking the 3' untranslated region showed a marginal degree of hypermutation. Addition of the 3' enhancer resulted in a slight increase in the number of mutations. However, the transgene containing DNase I-sensitive regions 3b and 4 in addition to the 3' enhancer showed more than a 10-fold increase in hypermutation, reaching levels comparable to those observed in endogenous V(H)186.2 genes of C57BL/6 mice.
Asunto(s)
Desoxirribonucleasa I/metabolismo , Reordenamiento Génico de Cadena Pesada de Linfocito B , Cadenas Pesadas de Inmunoglobulina/genética , Mutación , Animales , Linfocitos B/inmunología , Linfocitos B/metabolismo , Secuencia de Bases , Células Clonales , Análisis Mutacional de ADN , Femenino , Regulación de la Expresión Génica/inmunología , Humanos , Cadenas Pesadas de Inmunoglobulina/biosíntesis , Cadenas Pesadas de Inmunoglobulina/metabolismo , Región Variable de Inmunoglobulina/biosíntesis , Región Variable de Inmunoglobulina/genética , Región Variable de Inmunoglobulina/metabolismo , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Ratones Endogámicos ICR , Ratones Transgénicos , Datos de Secuencia Molecular , Proteínas Recombinantes de Fusión/biosíntesis , Proteínas Recombinantes de Fusión/genética , Bazo/citología , Bazo/metabolismo , Transgenes/inmunología , Células Tumorales CultivadasRESUMEN
Examination of the effects of water temperature on the inactivation of Cryptosporidium parvum oocysts with ozone, ozonation experiments were conducted in a semi-batch mode with a wide temperature range of 3-30 degrees C. Inactivation was assessed in terms of mice infectivity and in vitro excystation. The temperature dependency of the CT products by a reduction in infectivity of 2 log10 could be described successfully by the Arrhenius equation, 1/CT = 1.086 x 10(18)e-12520/K where CT is the integrated ozone concentration over the contact time (mg/min/L) and K is the Kelvin temperature of water. As for the reduction in viability assessed by the excystation assay, protocol B, the obtained regression equation, 1/CT = 1.802 x 10(18)e-12640/K, was almost identical to that observed for the infectivity. Thus, the CT products required for a 2 log10 reduction in both infectivity and viability increased by an average factor of 4.2 for every 10 degrees C decrease in water temperature. Additionally, our findings suggested that the viability, as determined by protocol B, could substitute for animal infectivity in evaluating the effects of environmental factors on the efficacy of ozonation.
Asunto(s)
Cryptosporidium parvum , Oxidantes Fotoquímicos/farmacología , Ozono/farmacología , Purificación del Agua/métodos , Animales , Modelos Teóricos , Dinámica Poblacional , Temperatura , Abastecimiento de AguaRESUMEN
We report strong instantaneous photoinduced absorption in the quasi-one-dimensional Mott insulator Sr2CuO3 in the IR spectral region. The observed photoinduced absorption is to an even-parity two-photon state that occurs immediately above the absorption edge. Theoretical calculation based on a two-band extended Hubbard model explains the experimental features and indicates that the strong two-photon absorption is due to a very large dipole coupling between nearly degenerate one- and two-photon states. Room temperature picosecond recovery of the optical transparency suggests the strong potential of Sr2CuO3 for all-optical switching.
RESUMEN
Caspases, which play crucial roles during apoptosis, are activated from their inactive proforms in a sequential cascade of cleavage by other members of the caspase family. Caspase-9 is autoprocessed by the Apaf-1/cytochrome c pathway and acts at an early point in this cascade, whereas Bcl-xL, an antiapoptotic member of the Bcl-2 family, prevents activation of caspases in vitro. Little is known, however, about the relation between caspase-9 and Bcl-xL during development of the mammalian nervous system. We used antisera against two cleavage sites in mouse caspase-9 that recognize only the activated form of mouse caspase-9, and we examined immunohistochemically the activation of mouse caspase-9 in the nervous system of Bcl-x-deficient mouse embryos. Mouse caspase-9 is processed at both D(353) and D(368), but it is processed preferentially at D(368) during apoptosis of cultured cells induced by various stimuli and in the nervous system of Bcl-x-deficient mouse embryos. We show that Bcl-xL protects against caspase-9- and/or caspase-3-dependent apoptosis in the caudal portion of the ventral hindbrain, anterior horn cells, and dorsal root ganglia neurons of the normal mouse embryos and against caspase-9/caspase-3-independent apoptosis in the dorsal region of the nervous system including the dorsal spinal cord. Furthermore, we demonstrate that Bcl-xL blocks cytochrome c release from mitochondria, causing activation of caspase-9 in anterior horn cells and dorsal root ganglia neurons in mouse embryos at embryonic day 11.5.
Asunto(s)
Caspasas/metabolismo , Sistema Nervioso/embriología , Proteínas Proto-Oncogénicas c-bcl-2/deficiencia , Animales , Células COS , Caspasa 9 , Caspasas/química , Caspasas/inmunología , Bovinos/sangre , Muerte Celular/fisiología , Células Cultivadas , Grupo Citocromo c/metabolismo , Embrión de Mamíferos/enzimología , Activación Enzimática/fisiología , Células Epiteliales/enzimología , Sangre Fetal , Factor 2 de Crecimiento de Fibroblastos/farmacología , Fibroblastos/enzimología , Ganglios Espinales/metabolismo , Sueros Inmunes/inmunología , Etiquetado Corte-Fin in Situ , Ratones , Ratones Noqueados/genética , Ratones Mutantes/genética , Sistema Nervioso/citología , Fragmentos de Péptidos/inmunología , Fragmentos de Péptidos/metabolismo , Proteínas Proto-Oncogénicas c-bcl-2/genética , Rombencéfalo/metabolismo , Proteína bcl-XRESUMEN
The recent discovery of checkpoint kinases has suggested the conservation of checkpoint mechanisms between yeast and mammals. In yeast, the protein kinase Chk1 is thought to mediate signaling associated with the DNA damage checkpoint of the cell cycle. However, the function of Chk1 in mammals has remained unknown. Targeted disruption of Chk1 in mice showed that Chk1(-/-) embryos exhibit gross morphologic abnormalities in nuclei as early as the blastocyst stage. In culture, Chk1(-/-) blastocysts showed a severe defect in outgrowth of the inner cell mass and died of apoptosis. DNA replication block and DNA damage failed to arrest the cell cycle before initiation of mitosis in Chk1(-/-) embryos. These results may indicate that Chk1 is indispensable for cell proliferation and survival through maintaining the G(2) checkpoint in mammals.
Asunto(s)
Proteínas Quinasas/genética , Proteínas Quinasas/fisiología , Alelos , Animales , Animales Recién Nacidos , Apoptosis , Blastocisto , División Celular/genética , Núcleo Celular/fisiología , Células Cultivadas , Quinasa 1 Reguladora del Ciclo Celular (Checkpoint 1) , Cruzamientos Genéticos , ADN/biosíntesis , Daño del ADN , Embrión de Mamíferos/metabolismo , Fibroblastos/metabolismo , Fase G2 , Genotipo , Humanos , Immunoblotting , Inmunohistoquímica , Etiquetado Corte-Fin in Situ , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos ICR , Ratones Transgénicos , Modelos Genéticos , Mutagénesis , Células MadreRESUMEN
Phosphorylation of IkappaB by the IkappaB kinase (IKK) complex is a critical step leading to IkappaB degradation and activation of transcription factor NF-kappaB. The IKK complex contains two catalytic subunits, IKKalpha and IKKbeta, the latter being indispensable for NF-kappaB activation by pro-inflammatory cytokines. Although IKK is activated by phosphorylation of the IKKbeta activation loop, the physiological IKK kinases that mediate responses to extracellular stimuli remain obscure. Here we describe an IKK-related kinase, named NAK (NF-kappaB-activating kinase), that can activate IKK through direct phosphorylation. NAK induces IkappaB degradation and NF-kappaB activity through IKKbeta. Endogenous NAK is activated by phorbol ester tumour promoters and growth factors, whereas catalytically inactive NAK specifically inhibits activation of NF-kappaB by protein kinase C-epsilon (PKCepsilon). Thus, NAK is an IKK kinase that may mediate IKK and NF-kappaB activation in response to growth factors that stimulate PKCepsilon activity.
Asunto(s)
Proteínas Serina-Treonina Quinasas/metabolismo , Secuencia de Aminoácidos , Animales , Células COS , Línea Celular , Clonación Molecular , Activación Enzimática , Células HeLa , Humanos , Quinasa I-kappa B , Luciferasas/genética , Ratones , Datos de Secuencia Molecular , FN-kappa B/metabolismo , Fosforilación , Serina/metabolismo , Transcripción Genética , Ubiquitinas/metabolismoRESUMEN
The retinoblastoma protein (pRb) is a key regulator of cell growth, differentiation and survival. pRb(-/-) mice show abnormal neuronal cell death in the developing brain. The function of pRb is regulated by its phosphorylation state. In this study, the phosphorylation of pRb during retinoic acid (RA)-induced neuronal differentiation of P19 cells was examined using site-specific antibodies against pRb phosphorylated at Ser601, Ser605 and Ser773. Although pRb was hyperphosphorylated in undifferentiated P19 cells, Ser601 and Ser773 were not phosphorylated. Upon exposure to RA, however, these two sites became strongly phosphorylated. Cdk4 kinase activity was almost undetectable in undifferentiated P19 cells, but was strongly activated on exposure to RA. In contrast, Cdk2 kinase activity and the phosphorylation of Ser605 were observed in undifferentiated cells as well as in RA-treated cells. These observations suggest that Cdk2 and Cdk4 may phosphorylate different sites of pRb in vivo and that the two sites of pRb examined here are newly phosphorylated during RA-induced neuronal differentiation in P19 cells.
Asunto(s)
Quinasas CDC2-CDC28 , Quinasas Ciclina-Dependientes/metabolismo , Neuronas/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Proto-Oncogénicas , Proteína de Retinoblastoma/metabolismo , Tretinoina/farmacología , Secuencia de Aminoácidos , Animales , Ciclo Celular , Diferenciación Celular/efectos de los fármacos , Línea Celular , Quinasa 2 Dependiente de la Ciclina , Quinasa 4 Dependiente de la Ciclina , Cinética , Neuronas/citología , Neuronas/efectos de los fármacos , Fosforilación , Fosfoserina/metabolismo , SerinaRESUMEN
Caspases and Bcl-xL, the mammalian homologues of the Caenorhabditis elegans (C. elegans) ced-3 and ced-9 genes, respectively, regulate apoptosis of various cells. Caspase-3 is processed into an active form (p20 or p17 and p12) during apoptosis. We investigated the relation between caspase-3 and Bcl-xL during development by examining activation of caspase-3 and apoptotic cells in Bcl-x-deficient (bcl-x(-/-)) mice at embryonic (E) day 11.5. We used a double-staining technique with a cleavage site-directed antibody against caspase-3 (anti-p20/17) and terminal-deoxytransferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL). Bcl-xL-deficiency increased both numbers of p20/17-positive and -negative apoptotic cells in dorsal root ganglia (DRG); the numbers of p20/17-positive apoptotic cells in the caudal parts of the ventral hindbrain and ventral spinal cord; and the numbers of p20/17-negative apoptotic cells in the dorsal midbrain, dorsal hindbrain, and dorsal spinal cord. Thus, Bcl-xL blocks the caspase-3-dependent apoptotic pathway in the restricted regions of the nervous system during development. Furthermore, these observations suggest that Bcl-xL protects against activation of the caspase-3-independent apoptotic pathway. Other caspases or apoptotic mechanisms may also be activated in the nervous systems of bcl-x(-/-) mice.