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Hey F, Andreadi C, Noble C, Patel B, Jin H, Kamata T, Straatman K, Luo J, Balmanno K, Jones DT, Collins VP, Cook SJ, Caunt CJ, Pritchard C. Over-expressed, N-terminally truncated BRAF is detected in the nucleus of cells with nuclear phosphorylated MEK and ERK. Heliyon 2018; 4:e01065. [PMID: 30603699 PMCID: PMC6304467 DOI: 10.1016/j.heliyon.2018.e01065] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 09/12/2018] [Accepted: 12/14/2018] [Indexed: 12/31/2022] Open
Abstract
BRAF is a cytoplasmic protein kinase, which activates the MEK-ERK signalling pathway. Deregulation of the pathway is associated with the presence of BRAF mutations in human cancer, the most common being V600E BRAF, although structural rearrangements, which remove N-terminal regulatory sequences, have also been reported. RAF-MEK-ERK signalling is normally thought to occur in the cytoplasm of the cell. However, in an investigation of BRAF localisation using fluorescence microscopy combined with subcellular fractionation of Green Fluorescent Protein (GFP)-tagged proteins expressed in NIH3T3 cells, surprisingly, we detected N-terminally truncated BRAF (ΔBRAF) in both nuclear and cytoplasmic compartments. In contrast, ΔCRAF and full-length, wild-type BRAF (WTBRAF) were detected at lower levels in the nucleus while full-length V600EBRAF was virtually excluded from this compartment. Similar results were obtained using ΔBRAF tagged with the hormone-binding domain of the oestrogen receptor (hbER) and with the KIAA1549-ΔBRAF translocation mutant found in human pilocytic astrocytomas. Here we show that GFP-ΔBRAF nuclear translocation does not involve a canonical Nuclear Localisation Signal (NLS), but is suppressed by N-terminal sequences. Nuclear GFP-ΔBRAF retains MEK/ERK activating potential and is associated with the accumulation of phosphorylated MEK and ERK in the nucleus. In contrast, full-length GFP-WTBRAF and GFP-V600EBRAF are associated with the accumulation of phosphorylated ERK but not phosphorylated MEK in the nucleus. These data have implications for cancers bearing single nucleotide variants or N-terminal deleted structural variants of BRAF.
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Affiliation(s)
- Fiona Hey
- Department of Molecular Cell Biology, University of Leicester, Lancaster Road, Leicester LE1 9HN, UK
| | - Catherine Andreadi
- Leicester Cancer Research Centre, Clinical Sciences Building, University of Leicester, Leicester Royal Infirmary, Leicester LE2 7LX, UK
| | - Catherine Noble
- Department of Molecular Cell Biology, University of Leicester, Lancaster Road, Leicester LE1 9HN, UK
| | - Bipin Patel
- Department of Molecular Cell Biology, University of Leicester, Lancaster Road, Leicester LE1 9HN, UK
| | - Hong Jin
- Department of Molecular Cell Biology, University of Leicester, Lancaster Road, Leicester LE1 9HN, UK
| | - Tamihiro Kamata
- Leicester Cancer Research Centre, Clinical Sciences Building, University of Leicester, Leicester Royal Infirmary, Leicester LE2 7LX, UK
| | - Kees Straatman
- Core Biotechnology Services, University of Leicester, Lancaster Road, Leicester LE1 9HN, UK
| | - Jinli Luo
- Leicester Cancer Research Centre, Clinical Sciences Building, University of Leicester, Leicester Royal Infirmary, Leicester LE2 7LX, UK
| | - Kathryn Balmanno
- Signalling Laboratory, The Babraham Institute, Babraham Research Campus, Cambridge CB22 3AT, UK
| | - David T.W. Jones
- Department of Pathology, Division of Molecular Histopathology, University of Cambridge, Cambridge CB2 0QQ, UK
| | - V. Peter Collins
- Department of Pathology, Division of Molecular Histopathology, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Simon J. Cook
- Signalling Laboratory, The Babraham Institute, Babraham Research Campus, Cambridge CB22 3AT, UK
| | - Christopher J. Caunt
- Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - Catrin Pritchard
- Leicester Cancer Research Centre, Clinical Sciences Building, University of Leicester, Leicester Royal Infirmary, Leicester LE2 7LX, UK
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Abstract
Gonadotropin-releasing hormone (GnRH) acts via G-protein coupled receptors on pituitary gonadotropes. These are Gq-coupled receptors that mediate acute effects of GnRH on the exocytotic secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), as well as the chronic regulation of their synthesis. FSH and LH control steroidogenesis and gametogenesis in the gonads so GnRH mediates control of reproduction by the central nervous system. GnRH is secreted in short pulses and the effects of GnRH on its target cells are dependent on the dynamics of these pulses. Here we provide a brief overview of the signaling network activated by GnRH with emphasis on the use of high content imaging for their examination. We also describe computational approaches that we have used to simulate GnRH signaling in order to explore dynamics, noise, and information transfer in this system.
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Visualizing and Quantitating the Spatiotemporal Regulation of Ras/ERK Signaling by Dual-Specificity Mitogen-Activated Protein Phosphatases (MKPs). Methods Mol Biol 2016; 1447:197-215. [PMID: 27514808 DOI: 10.1007/978-1-4939-3746-2_12] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The spatiotemporal regulation of the Ras/ERK pathway is critical in determining the physiological and pathophysiological outcome of signaling. Dual-specificity mitogen-activated protein kinase (MAPK) phosphatases (DUSPs or MKPs) are key regulators of pathway activity and may also localize ERK to distinct subcellular locations. Here we present methods largely based on the use of high content microscopy to both visualize and quantitate the subcellular distribution of activated (p-ERK) and total ERK in populations of mouse embryonic fibroblasts derived from mice lacking DUSP5, a nuclear ERK-specific MKP. Such methods in combination with rescue experiments using adenoviral vectors encoding wild-type and mutant forms of DUSP5 have allowed us to visualize specific defects in ERK regulation in these cells thus confirming the role of this phosphatase as both a nuclear regulator of ERK activity and localization.
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Perrett RM, Fowkes RC, Caunt CJ, Tsaneva-Atanasova K, Bowsher CG, McArdle CA. Signaling to extracellular signal-regulated kinase from ErbB1 kinase and protein kinase C: feedback, heterogeneity, and gating. J Biol Chem 2013; 288:21001-21014. [PMID: 23754287 PMCID: PMC3774369 DOI: 10.1074/jbc.m113.455345] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Many extracellular signals act via the Raf/MEK/ERK cascade in which kinetics, cell-cell variability, and sensitivity of the ERK response can all influence cell fate. Here we used automated microscopy to explore the effects of ERK-mediated negative feedback on these attributes in cells expressing endogenous ERK or ERK2-GFP reporters. We studied acute rather than chronic stimulation with either epidermal growth factor (ErbB1 activation) or phorbol 12,13-dibutyrate (PKC activation). In unstimulated cells, ERK-mediated negative feedback reduced the population-average and cell-cell variability of the level of activated ppERK and increased its robustness to changes in ERK expression. In stimulated cells, negative feedback (evident between 5 min and 4 h) also reduced average levels and variability of phosphorylated ERK (ppERK) without altering the “gradedness” or sensitivity of the response. Binning cells according to total ERK expression revealed, strikingly, that maximal ppERK responses initially occur at submaximal ERK levels and that this non-monotonic relationship changes to an increasing, monotonic one within 15 min. These phenomena occur in HeLa cells and MCF7 breast cancer cells and in the presence and absence of ERK-mediated negative feedback. They were best modeled assuming distributive (rather than processive) activation. Thus, we have uncovered a novel, time-dependent change in the relationship between total ERK and ppERK levels that persists without negative feedback. This change makes acute response kinetics dependent on ERK level and provides a “gating” or control mechanism in which the interplay between stimulus duration and the distribution of ERK expression across cells could modulate the proportion of cells that respond to stimulation.
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Affiliation(s)
- Rebecca M Perrett
- From the Laboratories for Integrative Neuroscience and Endocrinology, School of Clinical Sciences, University of Bristol, Whitson Street, Bristol BS13NY, United Kingdom
| | - Robert C Fowkes
- Endocrine Signaling Group, Royal Veterinary College, Royal College St., London NW10TU, United Kingdom
| | - Christopher J Caunt
- Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath BA27AY, United Kingdom
| | - Krasimira Tsaneva-Atanasova
- Bristol Centre for Applied Nonlinear Mathematics, Department of Engineering Mathematics, University of Bristol, Bristol BS81TR, United Kingdom, and
| | - Clive G Bowsher
- School of Mathematics, University of Bristol, Bristol BS81TW, United Kingdom
| | - Craig A McArdle
- From the Laboratories for Integrative Neuroscience and Endocrinology, School of Clinical Sciences, University of Bristol, Whitson Street, Bristol BS13NY, United Kingdom,.
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Rivero G, Llorente J, McPherson J, Cooke A, Mundell SJ, McArdle CA, Rosethorne EM, Charlton SJ, Krasel C, Bailey CP, Henderson G, Kelly E. Endomorphin-2: a biased agonist at the μ-opioid receptor. Mol Pharmacol 2012; 82:178-88. [PMID: 22553358 DOI: 10.1124/mol.112.078659] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Previously we correlated the efficacy for G protein activation with that for arrestin recruitment for a number of agonists at the μ-opioid receptor (MOPr) stably expressed in HEK293 cells. We suggested that the endomorphins (endomorphin-1 and -2) might be biased toward arrestin recruitment. In the present study, we investigated this phenomenon in more detail for endomorphin-2, using endogenous MOPr in rat brain as well as MOPr stably expressed in HEK293 cells. For MOPr in neurons in brainstem locus ceruleus slices, the peptide agonists [d-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin (DAMGO) and endomorphin-2 activated inwardly rectifying K(+) current in a concentration-dependent manner. Analysis of these responses with the operational model of pharmacological agonism confirmed that endomorphin-2 had a much lower operational efficacy for G protein-mediated responses than did DAMGO at native MOPr in mature neurons. However, endomorphin-2 induced faster desensitization of the K(+) current than did DAMGO. In addition, in HEK293 cells stably expressing MOPr, the ability of endomorphin-2 to induce phosphorylation of Ser375 in the COOH terminus of the receptor, to induce association of arrestin with the receptor, and to induce cell surface loss of receptors was much more efficient than would be predicted from its efficacy for G protein-mediated signaling. Together, these results indicate that endomorphin-2 is an arrestin-biased agonist at MOPr and the reason for this is likely to be the ability of endomorphin-2 to induce greater phosphorylation of MOPr than would be expected from its ability to activate MOPr and to induce activation of G proteins.
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Affiliation(s)
- Guadalupe Rivero
- School of Physiology and Pharmacology, University of Bristol, University Walk, Bristol, UK
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Finch AR, Caunt CJ, Perrett RM, Tsaneva-Atanasova K, McArdle CA. Dual specificity phosphatases 10 and 16 are positive regulators of EGF-stimulated ERK activity: indirect regulation of ERK signals by JNK/p38 selective MAPK phosphatases. Cell Signal 2012; 24:1002-11. [PMID: 22245064 PMCID: PMC3314959 DOI: 10.1016/j.cellsig.2011.12.021] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 12/28/2011] [Indexed: 11/25/2022]
Abstract
We have explored the possible role of dual specificity phosphatases (DUSPs) on acute EGF-mediated ERK signalling using high content imaging and a delayed MEK inhibition protocol to distinguish direct and indirect effects of the phosphatases on ERK activity. Using siRNAs, we were unable to find evidence that any of the MAPK phosphatases (MKPs) expressed in HeLa cells acts directly to dephosphorylate ppERK1/2 (dual phosphorylated ERKs 1 and/or 2) in the acute time-frame tested (0–14 min). Nevertheless, siRNAs against two p38/JNK MKPs (DUSPs 10 and 16) inhibited acute EGF-stimulated ERK activation. No such effect was seen for acute effects of the protein kinase C activator PDBu (phorbol 12,13 dibutyrate) on ERK activity, although effects of EGF and PDBu on ERK-dependent transcription (Egr-1 luciferase activity) were both reduced by siRNA targeting DUSPs 10 and 16. Inhibition of EGF-stimulated ERK activity by these siRNAs was reversed by pharmacological inhibition of p38 MAPK and single cell analysis revealed that the siRNAs did not influence the nuclear-cytoplasmic distribution of ppERK1/2. Thus, DUSPs 10 and 16 are positive regulators of activation, apparently acting by modulating cross-talk between the p38 and ERK pathways. A simplified mathematical model of this scenario accurately predicted the experimental data, supporting the conclusion that the major mechanism by which MKPs influence acute EGF-stimulated ERK responses is the negative regulation of p38, resulting in the positive regulation of ERK phosphorylation and activity.
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Affiliation(s)
- Ann R Finch
- Laboratories for Integrative Neuroscience and Endocrinology, School of Clinical Sciences, University of Bristol, 1 Whitson Street, Bristol, BS1 3NY, UK
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Elliott-Hunt CR, Holmes FE, Hartley DM, Perez S, Mufson EJ, Wynick D. Endogenous galanin protects mouse hippocampal neurons against amyloid toxicity in vitro via activation of galanin receptor-2. J Alzheimers Dis 2011; 25:455-62. [PMID: 21471641 PMCID: PMC3145121 DOI: 10.3233/jad-2011-110011] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Expression of the neuropeptide galanin is known to be upregulated in the brain of patients with Alzheimer's disease (AD). We and others have shown that galanin plays a neuroprotective role in a number of excitotoxic injury paradigms, mediated by activation of the second galanin receptor subtype (GAL2). In the present study, we investigated whether galanin/GAL2 plays a similar protective role against amyloid-β(Aβ) toxicity. Here we report that galanin or the GAL2/3-specific peptide agonist Gal2-11, both equally protect primary dispersed mouse wildtype (WT) neonatal hippocampal neurons from 250 nM Aβ1-42 toxicity in a dose dependent manner. The amount of Aβ1-42 induced cell death was significantly greater in mice with loss-of-function mutations in galanin (Gal-KO) or GAL2 (GAL2-MUT) compared to strain-matched WT controls. Conversely, cell death was significantly reduced in galanin over-expressing (Gal-OE) transgenic mice compared to strain-matched WT controls. Exogenous galanin or Gal2-11 rescued the deficits in the Gal-KO but not the GAL2-MUT cultures, confirming that the protective effects of endogenous or exogenous galanin are mediated by activation of GAL2. Despite the high levels of endogenous galanin in the Gal-OE cultures, the addition of exogenous 100 nM or 50 nM galanin or 100 nM Gal2-11 further significantly reduced cell death, implying that GAL2-mediated neuroprotection is not at maximum in the Gal-OE mice. These data further support the hypothesis that galanin over-expression in AD is a neuroprotective response and imply that the development of a drug-like GAL2 agonist might reduce the progression of symptoms in patients with AD.
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Affiliation(s)
- Caroline R. Elliott-Hunt
- Schools of Physiology and Pharmacology and Clinical Sciences, University of Bristol, Bristol, UK
| | - Fiona E. Holmes
- Schools of Physiology and Pharmacology and Clinical Sciences, University of Bristol, Bristol, UK
| | - Dean M. Hartley
- Department of Neurological Sciences, Rush University Medical Center, Chicago University, Chicago, IL, USA
| | - Sylvia Perez
- Department of Neurological Sciences, Rush University Medical Center, Chicago University, Chicago, IL, USA
| | - Elliott J. Mufson
- Department of Neurological Sciences, Rush University Medical Center, Chicago University, Chicago, IL, USA
| | - David Wynick
- Schools of Physiology and Pharmacology and Clinical Sciences, University of Bristol, Bristol, UK
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