534 research outputs found
Proline-rich tyrosine kinase 2 mediates gonadotropin-releasing hormone signaling to a specific extracellularly regulated kinase-sensitive transcriptional locus in the luteinizing hormone beta-subunit gene
No full textG protein-coupled receptor regulation of gene transcription primarily occurs through the phosphorylation of transcription factors by MAPKs. This requires transduction of an activating signal via scaffold proteins that can ultimately determine the outcome by binding signaling kinases and adapter proteins with effects on the target transcription factor and locus of activation. By investigating these mechanisms, we have elucidated how pituitary gonadotrope cells decode an input GnRH signal into coherent transcriptional output from the LH beta-subunit gene promoter. We show that GnRH activates c-Src and multiple members of the MAPK family, c-Jun NH2-terminal kinase 1/2, p38MAPK, and ERK1/2. Using dominant-negative point mutations and chemical inhibitors, we identified that calcium-dependent proline-rich tyrosine kinase 2 specifically acts as a scaffold for a focal adhesion/cytoskeleton-dependent complex comprised of c-Src, Grb2, and mSos that translocates an ERK-activating signal to the nucleus. The locus of action of ERK was specifically mapped to early growth response-1 (Egr-1) DNA binding sites within the LH beta-subunit gene proximal promoter, which was also activated by p38MAPK, but not c-Jun NH2-terminal kinase 1/2. Egr-1 was confirmed as the transcription factor target of ERK and p38MAPK by blockade of protein expression, transcriptional activity, and DNA binding. We have identified a novel GnRH-activated proline-rich tyrosine kinase 2-dependent ERK-mediated signal transduction pathway that specifically regulates Egr-1 activation of the LH beta-subunit proximal gene promoter, and thus provide insight into the molecular mechanisms required for differential regulation of gonadotropin gene expression
Norberg-Schulz’ elements of space in Dark City
No full textThe chapter analyses the future noir environment of Alex Proyas' Dark City (1998) from a spatial perspective. This science fiction film puts forth questions about the construction process of a city. The aliens in the film constantly alter each street, building and room to create the right environment for humans to dwell. These ‘strangers’ believe that they need to study humans in their authentic spaces to understand human nature. Using bits and pieces of people's memories, they reconstruct a worldless city. On another note, Christian Norberg-Schulz identifies four elements of space: physical, perceptual, existential and conceptual. Physical space is physical existence as it is. Perceptual space is the temporary space the user perceives. Existential space, for instance, the meaning of the concept of home, is abstract and permanent; it does not change with changing conditions. Finally, conceptual space, in his spatial philosophy, is the space concept of specialists like architects, economists and mathematicians. In the context of Dark City, the notion of building is studied as to physical, perceptual, existential and conceptual spaces of Norberg-Schulz through concepts of home, identity, belonging, and alienation with reference to the architecture of the city and the concept of worldlessness. As a spatial and temporal art, cinema includes representational space. With a critical gaze at the existing norms of architecture, science fiction films create new horizons. They extend the borders of the concept of space by creating the space of the future or of the non-existent. In this chapter, the author brings forth the imagined architectural designs of Dark City. Analysing this film in which space performs like an actor, she shows how sci-fi set designs add to the narration of a film and help question the concept of space
Hyperactive ERK/MAPK Regulates Cortical GABAergic Neuron Development
No full textabstract: Aberrant signaling through the canonical RAS/RAF/MEK/ERK (ERK/MAPK) pathway leads to the pathology of a group of neurodevelopmental disorders called RASopathies. RASopathies are caused by germline mutations in the ERK/MAPK pathway and have an incidence of approximately 1:2000 births. The majority of RASopathies stem from mutations that cause gain-of-function in the ERK/MAPK pathway. In this study, we have begun to unravel the roles that GABAergic interneurons play in the pathology of RASopathies. Our data demonstrate that gain-of-function ERK/MAPK signaling expressed in a GABAergic interneuron-specific fashion leads to forebrain hyperexcitability in mutant mice. Further, some GABAergic interneurons experience activated-caspase 3 mediated apoptosis in the embryonic subpallium, leading to a loss of PV-expressing interneurons in the somatosensory cortex. We found that pharmaceutical intervention during embryogenesis using a MEK1 inhibitor may be effective in preventing apoptosis of these neurons. Future work is still needed to understand the mechanism of the death of GABAergic interneurons and to further pursue therapeutic approaches. Taken together, this study suggests potential roles of cortical GABAergic interneurons in ERK/MAPK-linked pathologies and indicates possible approaches to provide therapy for these conditions
A kinase translocation reporter reveals real-time dynamics of ERK activity in Drosophila
No full textExtracellular signal-regulated kinase (ERK) lies downstream of a core signalling cascade that controls all aspects of development and adult homeostasis. Recent developments have led to new tools to image and manipulate the pathway. However, visualising ERK activity in vivo with high temporal resolution remains a challenge in Drosophila. We adapted a kinase translocation reporter (KTR) for use in Drosophila, which shuttles out of the nucleus when phosphorylated by ERK. We show that ERK-KTR faithfully reports endogenous ERK signalling activity in developing and adult tissues, and that it responds to genetic perturbations upstream of ERK. Using ERK-KTR in time-lapse imaging, we made two novel observations: firstly, sustained hyperactivation of ERK by expression of dominant-active epidermal growth factor receptor raised the overall level but did not alter the kinetics of ERK activity; secondly, the direction of migration of retinal basal glia correlated with their ERK activity levels, suggesting an explanation for the heterogeneity in ERK activity observed in fixed tissue. Our results show that KTR technology can be applied in Drosophila to monitor ERK activity in real-time and suggest that this modular tool can be further adapted to study other kinases. This article has an associated First Person interview with the first author of the paper
Author Correction: Combination of ERK and autophagy inhibition as a treatment approach for pancreatic cancer
No full textCorrection to "Combination of ERK and autophagy inhibition as a treatment approach for pancreatic cancer
Snail induction of nuclear erk 1/2 promotes epithelial-mesenchymal transition and chemotherapy resistance in breast cancer cells, 2013
No full textSnail is high in several cancers, correlates with poor clinical prognosis, and associated with increased tumor progression via epithelial-to-mesenchymal transition (EMT). EMT is a latent embryonic program that alters epithelial cells to appear more mesenchymal, regulates embryonic development and wound healing. Snail binds to enhancer box sequences on its target genes like E-cadherin, maspin, and estrogen receptor-alpha (ER-a) to increase EMT. MAP kinase (MAPK/ERK1/2) protein signaling regulates the effects of EMT during tumor progression by regulating cell proliferation, growth, migration, adhesion, invasion, and survival. Recent reports suggest that ERK1 and ERK2 isoforms may function differently although they share similar stimulants and substrates. We investigated the mechanism(s) of Snail-mediated EMT that may be regulated by ERK1/2 in breast cancer cells. Snail expression and phosphorylated ERK (pERK) were higher in breast cancer cells compared to normal breast epithelial cells. Snail siRNA in T47-D and MDA-MB-231 breast cancer cells led to p-ERK relocating from the nucleus to the cytoplasm, and MDA-MB-231 had decreased p-ERK expression. Snail overexpression in MCF-7 Snail cells had increased EMT in vitro and in vivo as compared to MCF-7 Neo (control) cells. MCF-7 Snail had less p-ERK than MCF-7 Neo, which was nuclear-localized. ERK2 isoform activity was also higher in the nucleus of MCF-7 Snail compared to MCF-7 Neo. p-ERK and import protein nucleoporin98 (NUP98) were colocalized at the nuclear membrane in MCF-7 Neo suggesting a shift to the nucleus as cancer progresses. MAPK inhibition decreased cell migration and increased cell adhesion in MCF-7 Snail cells, and also re-induced E-cadherin expression, but decreased adhesion and E-cadherin in MCF-7 Neo. ERK2 isoform regulates EMT because ERK2 siRNA decreased Snail in MCF-7 Snail, but decreased E-cadherin in MCF-7 Neo. MCF-7 cells overexpressing Snail decreased ER-a expression. MCF-7 Snail were less responsive to 4- hydroxytamoxifen (4-OHT) chemotherapy using mitochondrial membrane permeability and cytotoxicity assays. MCF-7 Snail were only sensitive after being treated with 4-OHT at lOuM plus UO126 at lOuM. Collectively, our data suggest that nuclear and cytoplasmic ERK1 isoform activity positively regulates cell adhesion and may have a suppressive role in preventing EMT and breast cancer progression. Conversely, nuclear ERK activity which is predominantly ERK2 isoform activity increases EMT, and promotes resistance to chemotherapy and may promote tumor progression
Induction of neurite outgrowth by α-phenyl-N-tert-butylnitrone through nitric oxide release and Ras-ERK pathway in PC12 cells
No full textIt has previously been suggested that the spin trap agent α-phenyl-N-tert-butylnitrone (PBN) induces neurite outgrowth through activation of the Ras-ERK pathway in PC12 cells. However, the chemical properties of PBN contributing to its biological function and the detailed mechanism for the activation of Ras by PBN remain unknown. This study demonstrates that the hydrophobic structure of PBN is related to the activation of Ras, by comparing with hydrophilic analogues of PBN. [14C]-labelled PBN was found to localize in the lipid fraction and activate Ras indirectly. On the other hand, neurite outgrowth by PBN was inhibited by a nitric oxide (NO) scavenger. Moreover, the neurite outgrowth induced by PBN and the NO donor NOR4 was inhibited by the dominant negative Ras or MAPK/ERK inhibitor. Taken together, these results suggest that PBN is incorporated into the plasma membrane and induces neurite outgrowth in PC12 cells by activating the Ras-ERK pathway through NO releas
Neuropeptide Y activates phosphorylation of ERK and STAT3 in stromal vascular cells from brown adipose tissue, but fails to affect thermogenic function of brown adipocytes
No full textThe thermogenic function of brown adipose tissue (BAT) is increased by norepinephrine (NE) released from sympathetic nerve endings, but the roles of NPY released along with NE are poorly elucidated. Here, we examined effect of NPY on basal and NE-enhanced thermogenesis in isolated brown adipocytes that express Y1 and Y5 receptor mRNA. Treatment of cells with NPY did not influence the basal and NE-enhanced rates of oxygen consumption and cAMP accumulation. Treatment with NPY also failed to induce ERK (Thr202/Tyr204) phosphorylation in the brown adipocytes. In contrast, treatment with NPY increased ERK phosphorylation in cultured stromal vascular cells from the BAT that express Y1 receptor mRNA. In the latter treatment with NPY also increased STAT3 (Ser727) phosphorylation. These results suggest that NPY mainly acts on stromal vascular cells in BAT and plays roles in the regulation of their gene transcription through ERK and STAT3 pathways, while NPY does not affect the thermogenic function of brown adipocytes
Harmine indusces Adipocyte Thermogenesis through RAC1-MEK-ERK-CHD4 Axis
No full text© The Author(s) 2016.Harmine is a natural compound possessing insulin-sensitizing effect in db/db diabetic mice. However its effect on adipose tissue browning is unknown. Here we reveal that harmine antagonizes high fat diet-induced adiposity. Harmine-treated mice gained less weight on a high fat diet and displayed increased energy expenditure and adipose tissue thermogenesis. In vitro, harmine potently induced the expression of thermogenic genes in both brown and white adipocytes, which was largely abolished by inhibition of RAC1/MEK/ERK pathway. Post-transcriptional modification analysis revealed that chromodomain helicase DNA binding protein 4 (CHD4) is a potential downstream target of harmine-mediated ERK activation. CHD4 directly binds the proximal promoter region of Ucp1, which is displaced upon treatment of harmine, thereby serving as a negative modulator of Ucp1. Thus, here we reveal a new application of harmine in combating obesity via this off-target effect in adipocytes.published_or_final_versio
Suppression of ERK signalling promotes pluripotent epiblast in the human blastocyst
No full text\ua9 The Author(s) 2025.Studies in the mouse demonstrate the importance of fibroblast growth factor (FGF) and extra-cellular receptor tyrosine kinase (ERK) in specification of embryo-fated epiblast and yolk-sac-fated hypoblast cells from uncommitted inner cell mass (ICM) cells prior to implantation. Molecular mechanisms regulating specification of early lineages in human development are comparatively unclear. Here we show that exogenous FGF stimulation leads to expanded hypoblast molecular marker expression, at the expense of the epiblast. Conversely, we show that specifically inhibiting ERK activity leads to expansion of epiblast cells functionally capable of giving rise to na\uefve human pluripotent stem cells. Single-cell transcriptomic analysis indicates that these epiblast cells downregulate FGF signalling and maintain molecular markers of the epiblast. Our functional study demonstrates the molecular mechanisms governing ICM specification in human development, whereby segregation of the epiblast and hypoblast lineages occurs during maturation of the mammalian embryo in an ERK signal-dependent manner
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