| 1. |
- Aifa, Sami, et al.
(författare)
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Interactions between the juxtamembrane domain of the EGFR and calmodulin measured by surface plasmon resonance
- 2002
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Ingår i: Cellular Signalling. - 0898-6568 .- 1873-3913. ; 14:12, s. 1005-1013
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Tidskriftsartikel (refereegranskat)abstract
- One early response to epidermal growth factor receptor (EGFR) activation is an increase in intracellular calcium. We have used surface plasmon resonance (SPR) to study real-time interactions between the intracellular juxtamembrane (JM) region of EGFR and calmodulin. The EGFR-JM (Met644-Phe688) was expressed as a GST fusion protein and immobilised on a sensor chip surface. Calmodulin specifically interacts with EGFR-JM in a calcium-dependent manner with a high on and high off rate. Chemical modification of EGFR-JM by using arginine-selective phenylglyoxal or deletion of the basic segment Arg645-Arg657 inhibits the interaction. Phosphorylation of EGFR-JM by protein kinase C (PKC) or glutamate substitution of Thr654 inhibits the interaction, suggesting that PKC phosphorylation electrostatically interferes with calmodulin binding to basic arginine residues. Calmodulin binding was also inhibited by suramin. Our results suggest that EGFR-JM is essential for epidermal growth factor (EGF)-mediated calcium-calmodulin signalling and for signal integration between other signalling pathways.
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| 2. |
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| 3. |
- Andersson, Tony, 1973-, et al.
(författare)
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Phosphoinositide 3-kinase is involved in Xenopus and Labrus melanophore aggregation
- 2003
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Ingår i: Cellular Signalling. - 0898-6568 .- 1873-3913. ; 15:12, s. 1119-1127
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Tidskriftsartikel (refereegranskat)abstract
- Melanophores are pigmented cells capable of quick colour changes through coordinated transport of their intracellular pigment granules. We demonstrate the involvement of phosphoinositide 3-kinase (PI3-K) in Xenopus and Labrus aggregation by the use of the PI3-K inhibitor, LY-294002. In Xenopus, wortmannin-insensitive PI3-K was found to be essential for the aggregation, mitogen-activated protein kinase (MAPK) activation and tyrosine phosphorylation of a 280-kDa protein, and for the maintenance of low cyclic adenosine 3':5'-monophosphate (cAMP) during the aggregated state. Pre-aggregated cells disperse completely to LY-294002 at 50-100 muM, involving a transient elevation in cAMP due to adenylate cyclase (AC) stimulation or to inhibition of cyclic nucleotide phosphodiesterase (PDE). The inactive analogue LY-303511 did not induce dispersion at the same concentrations. PDE4 and/or PDE2 was found to be involved in melanosome aggregation. The similar kinetics of LY-294002 and various PDE inhibitors indicates that the elevation of cAMP might be due to inhibition of PDE. In Labrus melanophores, LY-294002 had a less dramatic effect, probably due to less dependence on PDE in regulation of cAMP levels. In Xenopus aggregation, we suggest that melatonin stimulation of the Mel1c receptor via G(betagamma) activates PI3-K that, directly or indirectly via MAPK, activates PDE. (C) 2003 Elsevier Inc. All rights reserved.
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| 4. |
- Attarha, Sanaz, et al.
(författare)
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Mast cells modulate proliferation, migration and sternness of glioma cells through downregulation of GSK3 beta expression and inhibition of STAT3 activation
- 2017
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Ingår i: Cellular Signalling. - : Elsevier BV. - 0898-6568 .- 1873-3913. ; 37, s. 81-92
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Tidskriftsartikel (refereegranskat)abstract
- Glioblastoma (GBM) heterogeneity is the main obstacle to efficient treatment due to the existence of sub population of cells with increased tumorigenicity and network of tumor associated parenchymal cells in the tumor microenvironment. We previously demonstrated that mast cells (MCs) infiltrate mouse and human gliomas in response to variety of signals in a glioma grade-dependent manner. However, the role of MCs in glioma development and the mechanisms behind MCs-glioma cells interaction remain unidentified. In the present study, we show that MCs upon activation by glioma cells produce soluble factors including IL-6, which are documented to be involved in cancer-related activities. We observe 'tumor educated' MCs decrease glioma cell proliferation and migration, reduce self-renewal capacity and expression of stemness markers but in turn promote glioma cell differentiation. 'Tumor educated' MC derived mediators exert these effects via inactivation of STAT3 signaling pathway through GSK3 beta down-regulation. We identified 'tumor educated' MC derived IL-6 as one of the contributors among the complex mixture of MCs mediators, to be partially involved in the observed MC induced biological effect on glioma cells. Thus, MC mediated abolition of STAT3 signaling hampers glioma cell proliferation and migration by suppressing their stemness and inducing differentiation via down-regulation of GSK3 beta expression. Targeting newly identified inflammatory MC-STAT3 axis could contribute to patient tailored therapy and unveil potential future therapeutic opportunities for patients.
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| 5. |
- Batool, Tahira, et al.
(författare)
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Upregulated BMP-Smad signaling activity in the glucuronyl C5-epimerase knock out MEF cells
- 2019
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Ingår i: Cellular Signalling. - : Elsevier. - 0898-6568 .- 1873-3913. ; 54, s. 122-129
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Tidskriftsartikel (refereegranskat)abstract
- Glucuronyl C5-epimerase (Hsepi) catalyzes the conversion of glucuronic acid to iduronic acid in the process of heparan sulfate biosynthesis. Targeted interruption of the gene, Glce,in mice resulted in neonatal lethality with varied defects in organ development. To understand the molecular mechanisms of the phenotypes, we used mouse embryonic fibroblasts (MEF) as a model to examine selected signaling pathways. Our earlier studies found reduced activities of FGF-2, GDNF, but increased activity of sonic hedgehog in the mutant cells. In this study, we focused on the bone morphogenetic protein (BMP) signaling pathway. Western blotting detected substantially elevated endogenous Smad1/5/8 phosphorylation in the Hsepi mutant (KO) MEF cells, which is reverted by re-expression of the enzyme in the KO cells. The mutant cells displayed an enhanced proliferation and elevated alkaline phosphatase activity, marking higher differentiation, when cultured in osteogenic medium. The high level of Smad1/5/8 phosphorylation was also found in primary calvarial cells isolated from the KO mice. Analysis of the genes involved in the BMP signaling pathway revealed upregulation of a number of BMP ligands, but reduced expression of several Smads and BMP antagonist (Grem1) in the KO MEF cells. The results suggest that Hsepi expression modulates BMP signaling activity, which, at least partially, is associated with defected molecular structure of heparan sulfate expressed in the cells.
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| 6. |
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| 7. |
- Berggreen, Christine, et al.
(författare)
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cAMP-elevation mediated by β-adrenergic stimulation inhibits salt-inducible kinase (SIK) 3 activity in adipocytes.
- 2012
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Ingår i: Cellular Signalling. - : Elsevier BV. - 1873-3913 .- 0898-6568. ; 24:9, s. 1863-1871
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Tidskriftsartikel (refereegranskat)abstract
- Salt-inducible kinase (SIK) 3 is a virtually unstudied, ubiquitously expressed serine/threonine kinase, belonging to the AMP-activated protein kinase (AMPK)-related family of kinases, all of which are regulated by LKB1 phosphorylation of a threonine residue in their activation (T)-loops. Findings in adrenal cells have revealed a role for cAMP in the regulation of SIK1, and recent findings suggest that insulin can regulate an SIK isoform in Drosophila. As cAMP has important functions in adipocytes, mainly in the regulation of lipolysis, we have evaluated a potential role for cAMP, as well as for insulin, in the regulation of SIK3 in these cells. We establish that raised cAMP levels in response to forskolin and the β-adrenergic receptor agonist CL 316,243 induce a phosphorylation of SIK3 in HEK293 cells and primary adipocytes. This phosphorylation coincides with increased 14-3-3 binding to SIK3 in these cell types. Our findings also show that cAMP-elevation results in reduced SIK3 activity in adipocytes. Phosphopeptide mapping and site-directed mutagenesis reveal that the cAMP-mediated regulation of SIK3 appears to depend on three residues, T469, S551 and S674, that all contribute to some extent to the cAMP-induced phosphorylation and 14-3-3-binding. As the cAMP-induced regulation can be reversed with the protein kinase A (PKA) inhibitor H89, and a role for other candidate kinases, including PKB and RSK, could be excluded, we believe that PKA is the kinase responsible for SIK3 regulation in response to elevated cAMP levels. Our findings of cAMP-mediated regulation of SIK3 suggest that SIK3 may mediate some of the effects of this important second messenger in adipocytes.
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| 8. |
- Bergström Lind, Sara, et al.
(författare)
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Toward a comprehensive characterization of the phosphotyrosine proteome
- 2011
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Ingår i: Cellular Signalling. - : Elsevier BV. - 0898-6568 .- 1873-3913. ; 23:8, s. 1387-1395
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Tidskriftsartikel (refereegranskat)abstract
- Tyrosine phosphorylation (pTyr) regulates important cell functions and plays a key role in carcinogenesis. The purpose of this study was to perform a comprehensive study of the phosphotyrosine proteome. Immunoaffinity enriched pTyr proteins and peptides from K562 leukemia cells were analyzed with high-resolving liquid chromatography mass spectrometry. Two different antibodies selective for the pTyr modification were used in repeated enrichments to identify as many pTyr peptides as possible. Stringent verification of putative pTyr sites was performed to assure high reliability in the subsequent biological interpretation of the data. Identified pTyr proteins were subjected to pathway analysis by using different analytical tools. In total, 294 pTyr peptides belonging to 217 pTyr proteins were identified, 15 of which had not previously been reported to be modified by pTyr. The pTyr proteins were clustered in six major groups based on the biological functions "cellular signaling", "cell motility and shape", "cell cycle process", "transport", "RNA processing" and "protein processing". The pTyr proteins were mainly positioned in the following cellular compartments: cytoplasm, cytoskeleton, nucleus and ribonucleoprotein complexes. An interesting finding was that many proteins were related to RNA processing and were found to be heterogeneous nuclear ribonucleoproteins. Also, more than half of the novel pTyr proteins were localized to the nucleus, of which three (PBX2, TEAD1 and DIDO1) were classified as transcription factors and two (CENPC1 and MAD2L1) are associated with cell division control.
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| 9. |
- Bertran, Esther, et al.
(författare)
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Role of CXCR4/SDF-1 alpha in the migratory phenotype of hepatoma cells that have undergone epithelial-mesenchymal transition in response to the transforming growth factor-beta.
- 2009
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Ingår i: Cellular Signalling. - : Elsevier BV. - 0898-6568 .- 1873-3913. ; 21:11, s. 1595-1606
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Tidskriftsartikel (refereegranskat)abstract
- Treatment of FaO rat hepatoma cells with TGF-beta selects cells that survive to its apoptotic effect and undergo epithelial-mesenchymal transitions (EMT). We have established a cell line (T beta T-FaO, from TGF-beta-treated FaO) that shows a mesenchymal, de-differentiated, phenotype in the presence of TGF-beta and is refractory to its suppressor effects. In the absence of this cytokine, cells revert to an epithelial phenotype in 3-4 weeks and recover the response to TGF-beta. T beta T-FaO show higher capacity to migrate than that observed in the parental FaO cells. We found that FaO cells express low levels of CXCR4 and do not respond to SDF-1 alpha. However, TGF-beta up-regulates CXCR4, through a NF kappaB-dependent mechanism, and T beta T-FaO cells show elevated levels of CXCR4, which is located in the presumptive migration front. A specific CXCR4 antagonist (AMD3100) attenuates the migratory capacity of T beta T-FaO cells on collagen gels. Extracellular SDF-1 alpha activates the ERKs pathway in T beta T-FaO, but not in FaO cells, increasing cell scattering and protecting cells from apoptosis induced by serum deprivation. Targeted knock-down of CXCR4 with specific siRNA blocks the T beta T-FaO response to SDF-1 alpha. Thus, the SDF-1/CXCR4 axis might play an important role in mediating cell migration and survival after a TGF-beta-induced EMT in hepatoma cells.
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| 10. |
- Caja, Laia, et al.
(författare)
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Differential intracellular signalling induced by TGF-beta in rat adult hepatocytes and hepatoma cells : implications in liver carcinogenesis.
- 2007
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Ingår i: Cellular Signalling. - : Elsevier BV. - 0898-6568 .- 1873-3913. ; 19:4, s. 683-94
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Tidskriftsartikel (refereegranskat)abstract
- The transforming growth factor-beta (TGF-beta) regulates hepatocyte growth, inhibiting proliferation and inducing apoptosis. Indeed, escaping from the TGF-beta suppressor actions might be a prerequisite for liver tumour progression. In this work we show that TGF-beta plays a dual role in regulating apoptosis in FaO rat hepatoma cells, since, in addition to its pro-apoptotic effect, TGF-beta also activates survival signals, such as AKT, the epidermal growth factor receptor (EGFR) being required for its activation. TGF-beta induces the expression of the EGFR ligands transforming growth factor-alpha (TGF-alpha) and heparin-binding EGF-like growth factor (HB-EGF) and induces intracellular re-localization of the EGFR. Cells that overcome the apoptotic effects of TGF-beta undergo morphological changes reminiscent of an epithelial-mesenchymal transition (EMT) process. In contrast, TGF-beta does not activate AKT in adult hepatocytes, which correlates with lack of EGFR transactivation and no response to EGFR inhibitors. Although TGF-beta induces TGF-alpha and HB-EGF in adult hepatocytes, these cells show very low expression of TACE/ADAM 17 (TNF-alpha converting enzyme), which is required for EGFR ligand proteolysis and activation. Furthermore, adult hepatocytes do not undergo EMT processes in response to TGF-beta, which might be due, at least in part, to the fact that F-actin re-organization induced by TGF-beta in FaO cells require the EGFR pathway. Finally, results indicate that EGFR transactivation does not block TGF-beta-induced cell cycle arrest in FaO cells, but must be interfering with the pro-apoptotic signalling. In conclusion, TGF-beta is a suppressor factor for adult quiescent hepatocytes, but not for hepatoma cells, where it plays a dual role, both suppressing and promoting carcinogenesis.
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