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Kinase Activation (kinase + activation)
Kinds of Kinase Activation Selected AbstractsTNF-, Mediates p38 MAP Kinase Activation and Negatively Regulates Bone Formation at the Injured Growth Plate in Rats,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 7 2006Fiona H Zhou Abstract TNF-, is known to inhibit osteoblast differentiation in vitro and yet it is essential for bone fracture repair. Roles of TNF-, in the bony repair of injured growth plate were examined in young rats treated with a TNF-, antagonist. The results show that TNF-, mediates p38 activation, which influences the recruitment, proliferation, and osteoblast differentiation of mesenchymal cells and negatively regulates bone formation at the injured growth plate. Introduction: TNF-, inhibits expression of osteoblast differentiation factor cbfa1 and osteoblast differentiation in vitro and yet TNF-, signaling is essential for bone fracture healing. Roles of TNF-, in the bony repair of injured growth plate cartilage are unknown. Materials and Methods: Roles of TNF-, in the activation of p38 mitogen activated protein (MAP) kinase and the subsequent bony repair of the injured growth plate were examined in young rats receiving the TNF-, inhibitor ENBREL or saline control. Activation of p38 was determined by Western blot analysis and immunohistochemistry. Inflammatory cell counts on day 1, measurements of repair tissue proportions, and counting of proliferative mesenchymal cells on day 8 at growth plate injury site were carried out (n = 6). Expression of inflammatory cytokines TNF-, and IL-1,, fibrogenic growth factor (FGF)-2, cbfa1, and bone protein osteocalcin at the injured growth plate was assessed by quantitative RT-PCR. Effects of TNF-, signaling on proliferation, migration, and apoptosis of rat bone marrow mesenchymal cells (rBMMCs) and the regulatory roles of p38 in these processes were examined using recombinant rat TNF-,, ENBREL, and the p38 inhibitor SB239063 in cultured primary rBMMCs. Results: p38 activation was induced in the injured growth plate during the initial inflammatory response, and activated p38 was immunolocalized in inflammatory cells at the injury site and in the adjacent growth plate. In addition, activation of p38 was blocked in rats treated with TNF-, antagonist, suggesting a role of TNF-, in p38 activation. Whereas TNF-, inhibition did not alter inflammatory infiltrate and expression of TNF-, and IL-1, at the injured growth plate on day 1, it reduced mesenchymal infiltrate and cell proliferation and FGF-2 expression on day 8. Consistently, TNF-, increased proliferation and migration of rBMMCs in vitro, whereas p38 inhibition reduced rBMMC proliferation and migration. At the injured growth plate on day 8, TNF-, inhibition increased expression of cbfa1 and osteocalcin and increased trabecular bone formation at the injury site. There was a significant inverse correlation between TNF-, and cbfa1 expression levels, suggesting a negative relationship between TNF-, and cbfa1 in this in vivo model. Conclusions: These observations suggest that TNF-, activates p38 MAP kinase during the inflammatory response at the injured growth plate, and TNF-,-p38 signaling seems to be required for marrow mesenchymal cell proliferation and migration at the growth plate injury site and in cell culture. Furthermore, TNF signaling has an inhibitory effect on bone formation at the injured growth plate by suppressing bone cell differentiation and bone matrix synthesis at the injury site. [source] Altered Mitogen-Activated Protein Kinase Activation In Vascular Smooth Muscle Cells From Spontaneously Hypertensive RatsCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 7 2002Takao Kubo SUMMARY 1.,We previously reported that activation function of mitogen-activated protein kinases (MAPK) is enhanced in aorta strips from both prehypertensive and hypertensive spontaneously hypertensive rats (SHR) and that this enhancement of MAPK activation results from enhanced MAPK activation reactivity to angiotensin (Ang) II in SHR aorta strips. 2.,The purpose of the present study was to examine whether the enhanced function of the vascular angiotensin system observed in SHR aorta strips results from genetic alterations of vascular smooth muscle cells from SHR. 3.,Basal MAPK activity was within normal limits in cells from 4-week-old SHR, whereas enzyme activity was enhanced in 9-week-old SHR compared with age-matched Wistar-Kyoto (WKY) rats. 4.,Mitogen-activated protein kinase activation reactivity to AngII and endothelin-1 was enhanced in 9-week-old SHR cells but not in 4-week-old SHR cells. The enhancement of basal MAPK activity in 9-week-old SHR cells was abolished by a combination of the angiotensin AT1 receptor antagonist losartan and the endothelin receptor antagonist BQ123. 5.,These findings suggest that MAPK activation function in 4-week-old SHR cells is not enhanced. Thus, it appears that factors outside vascular smooth muscle cells are needed for the enhanced MAPK activation observed in 4-week-old SHR aorta strips. In 9-week-old SHR, MAPK activation function is enhanced in cells themselves and this function may, at least in part, contribute to the enhanced MAPK activation observed in SHR aorta strips. [source] Protein kinases A and C stimulate the Na+ active transport in frog skeletal muscle without an appreciable change in the number of sarcolemmal Na+ pumpsACTA PHYSIOLOGICA, Issue 4 2005R. A. Venosa Abstract Aim:, The activation of both protein kinases A (PKA) and protein kinases C (PKC) in some cell types increases and in others reduces active Na+ efflux. These effects have been ascribed to either a change in the rate of ionic translocation by a fixed number of Na+ pumps or, a change in the number of plasma membrane pumps. The purpose of the present experiments was to study the effect of activating PKA and PKC on the Na+ extrusion by the Na+ pump in frog skeletal muscle. Methods:, Na+ (22Na+) fluxes and ouabain (3H-ouabain) binding were measured in frog sartorius muscles. Results:, Both activation of PKA and PKC increased the active Na+ extrusion by a factor of two; these effects were not additive. Ouabain binding experiments indicated that the pump stimulation by activation of these kinases is not associated with any significant increase in the number of plasma membrane pumps. Stimulation of the active Na+ efflux by protein kinase activation (no change in the number of sarcolemmal pumps) and by hypotonicity (increase in the number of pumps) could be elicited in the same preparation and they were additive. Conclusion:, It is concluded that in frog skeletal muscle fibres, (1) activation of both PKA and PKC stimulate the Na+ pump by increasing its rate of ionic translocation; and (2) two modes of Na+ active transport (with and without an increase in the number of pumps) are operative, and can be at work simultaneously, a phenomenon to be reckoned with. [source] MAP kinase activation in avian cardiovascular developmentDEVELOPMENTAL DYNAMICS, Issue 4 2004Christine M. Liberatore Abstract Signaling pathways mediated by receptor tyrosine kinases (RTK) and mitogen-activated protein kinase (MAPK) activation have multiple functions in the developing cardiovascular system. The localization of diphosphorylated extracellular signal regulated kinase (dp-ERK) was monitored as an indicator of MAPK activation in the forming heart and vasculature of avian embryos. Sustained dp-ERK expression was observed in vascular endothelial cells of embryonic and extraembryonic origins. Although dp-ERK was not detected during early cardiac lineage induction, MAPK activation was observed in the epicardial, endocardial, and myocardial compartments during heart chamber formation. Endocardial expression of dp-ERK in the valve primordia and heart chambers may reflect differential cell growth associated with RTK signaling in the heart. dp-ERK localization in the epicardium, subepicardial fibroblasts, myocardial fibroblasts, and coronary vessels is consistent with MAPK activation in epicardial-derived cell lineages. The complex temporal,spatial regulation of dp-ERK in the heart supports diverse regulatory functions for RTK signaling in different cell populations, including the endocardium, myocardium, and epicardial-derived cells during cardiac organogenesis. Developmental Dynamics 230:773,780, 2004. © 2004 Wiley-Liss, Inc. [source] Neurotrophic activities of trk receptors conserved over 600 million years of evolutionDEVELOPMENTAL NEUROBIOLOGY, Issue 1 2004Gad Beck Abstract The trk family of receptor tyrosine kinases is crucial for neuronal survival in the vertebrate nervous system, however both C. elegans and Drosophila lack genes encoding trks or their ligands. The only invertebrate representative of this gene family identified to date is Ltrk from the mollusk Lymnaea. Did trophic functions of trk receptors originate early in evolution, or were they an innovation of the vertebrates? Here we show that the Ltrk gene conserves a similar exon/intron order as mammalian trk genes in the region encoding defined extracellular motifs, including one exon encoding a putative variant immunoglobulin-like domain. Chimeric receptors containing the intracellular and transmembrane domains of Ltrk undergo ligand-induced autophosphorylation followed by MAP kinase activation in transfected cells. The chimeras are internalized similarly to TrkA in PC12 cells, and their stimulation leads to differentiation and neurite extension. Knock-down of endogenous Ltrk expression compromises outgrowth and survival of Lymnaea neurons cultured in CNS-conditioned medium. Thus, Ltrk is required for neuronal survival, suggesting that trophic activities of the trk receptor family originated before the divergence of molluscan and vertebrate lineages approximately 600 million years ago. © 2004 Wiley Periodicals, Inc. J Neurobiol 60: 12,20, 2004 [source] Up-regulation of leukocyte CXCR4 expression by sulfatide: An L-selectin-dependent pathway on CD4+ T cellsEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 10 2007Pascal Duchesneau Abstract CXCR4 plays significant roles in immune and inflammatory responses and is important for selective recruitment of leukocytes. We previously showed that CXCR4 surface expression of human lymphocytes was affected by sulfatide, an in vivo ligand for L-selectin. Increased CXCR4 expression was shown to promote biologically relevant functions such as integrin-dependent adhesion and transmigration. Here, we show that sulfatide-induced CXCR4 up-regulation also occurs on other leukocyte subsets in humans and mice. B cells and CD4+CD25+ T cells had the highest CXCR4 up-regulation after sulfatide stimulation. Transfection of L-selectin was sufficient for K562 cells to acquire sulfatide-induced CXCR4 up-regulation, while analysis of L-selectin knockout mice revealed that this response was critically L-selectin dependent only for CD4+ T cells, suggesting an alternative pathway in CD8+ T cells and B cells. Sulfatide triggered several intracellular signaling events in CD4+ T cells, but only tyrosine kinase activation, including members of the Src family, were essential for L-selectin to CXCR4 signaling. CXCR4 up-regulation was rapid, enhanced CXCL12-induced signaling and increased chemotaxis toward CXCL12, and therefore has potentially important roles in vivo. Thus, the response to CXCL12 depends in part on tissue expression of sulfatide and, specifically in CD4+ T cells, also depends on the surface level of L-selectin. [source] Activation of Epstein-Barr virus/C3d receptor (gp140, CR2, CD21) on human cell surface triggers pp60src and Akt-GSK3 activities upstream and downstream to PI 3-kinase, respectivelyEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 9 2003Monique Barel Abstract We previously demonstrated that CR2 activation on human B lymphocyte surface specifically triggered tyrosine phosphorylation of the 95-kDa nucleolin, this leading to its binding on SH2 domainsof p85 sub-unit of PI 3-kinase and to activation of this enzyme. The specificity of CR2 pathway was clearly demonstrated as neither CD19 nor BCR could induce tyrosine phosphorylation of nucleolin in normal B lymphocytes. These data led us to investigate herein additional molecular events, which were triggered by CR2 activation, upstream and downstream to PI 3-kinase activation. Upstream, we demonstrated that pp60src, a tyrosine kinase of the src family, was involved in tyrosine phosphorylation of nucleolin, while syk tyrosine kinase was not. We also demonstrated a direct protein-proteininteraction of pp60src with nucleolin in a CR2-dependent and CD19-independent pathway. Downstream, we demonstrated that CR2 activation also triggered Akt and GSK3 enzyme activation, this pathway being under the control of pp60src tyrosine kinase activation. These regulatory functions of activated CR2 were specific as independent of syk tyrosine kinase and of CD19 and BCR activation. Thus, CR2 activation recruits a specific mechanism to activate PI 3-kinase and its subsequent pathways, this mechanism being different to those recruited by CD19 and BCR. [source] Extracellular signal-regulated kinase activation is required for consolidation and reconsolidation of memory at an early stage of ontogenesisEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2009Solčne Languille Abstract The ability to form long-term memories exists very early during ontogeny; however, the properties of early memory processes, brain structures involved and underlying cellular mechanisms are poorly defined. Here, we examine the role of extracellular signal-regulated kinase (ERK), a member of the mitogen-activated protein kinase/ERK signaling cascade, which is crucial for adult memory, in the consolidation and reconsolidation of an early memory using a conditioned taste aversion paradigm in 3-day-old rat pups. We show that intraperitoneal injection of SL327, the upstream mitogen-activated protein kinase kinase inhibitor, impairs both consolidation and reconsolidation of early memory, leaving short-term memory after acquisition and after reactivation intact. The amnesic effect of SL327 diminishes with increasing delays after acquisition and reactivation. Biochemical analyses revealed ERK hyperphosphorylation in the amygdala but not the hippocampus following acquisition, suggesting functional activation of the amygdala as early as post-natal day 3, although there was no clear evidence for amygdalar ERK activation after reactivation. These results indicate that, despite an immature brain, the basic properties of memory and at least some of the molecular mechanisms and brain structures implicated in aversion memory share a number of similarities with the adult and emerge very early during ontogeny. [source] Bi-directional regulation of postsynaptic cortactin distribution by BDNF and NMDA receptor activityEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2005Junko Iki Abstract Cortactin is an F-actin-associated protein which interacts with the postsynaptic scaffolding protein Shank at the SH3 domain and is localized within the dendritic spine in the mouse neuron. Green fluorescent protein (GFP)-based time-lapse imaging revealed cortactin redistribution from dendritic cytoplasm to postsynaptic sites by application of brain-derived neurotrophic factor (BDNF). This response was mediated by mitogen-activated protein (MAP) kinase activation and was dependent on the C-terminal SH3 domain. In contrast, activation of N -methyl- d -aspartate (NMDA) receptors induced loss of cortactin from postsynaptic sites. This NMDA-dependent redistribution was blocked by an Src family kinase inhibitor. Conversely, increasing Src family kinase activity induced cortactin phosphorylation and loss of cortactin from the postsynaptic sites. Finally, blocking of endogenous BDNF reduced the amount of cortactin at the postsynaptic sites and an NMDA receptor antagonist prevented this reduction. These results indicate the importance of counterbalance between BDNF and NMDA receptor-mediated signalling in the reorganization of the postsynaptic actin cytoskeleton during neuronal development. [source] Nerve growth factor-induced circadian phase shifts and MAP kinase activation in the hamster suprachiasmatic nucleiEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2005Gastón A. Pizzio Abstract Circadian rhythms are entrained by light and by several neurochemical stimuli. In hamsters housed in constant darkness, i.c.v. administration of nerve growth factor (NGF) at various times in their circadian cycle produced phase shifts of locomotor activity rhythms that were similar in direction and circadian timing to those produced by brief pulses of light. Moreover, the effect of NGF and light were not additive, indicating signalling points in common. These points include the immediate-early gene c-fos and ERK1/2, a component of the mitogen-activated protein kinases (MAPK) family. NGF activates c-FOS and ERK1/2-MAPK in the suprachiasmatic nuclei, the site of a circadian clock in mammals, when administered during the subjective night but not during the day. The effect of NGF on ERK1/2 activation was not inhibited by the administration of MK-801, a glutamate/NMDA receptor antagonist. These results suggest that NGF, acting through MAPK activation, plays a role in photic entrainment of the mammalian circadian clock. [source] Fractalkine reduces N -methyl- d -aspartate-induced calcium flux and apoptosis in human neurons through extracellular signal-regulated kinase activationEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2004Kumaran Deiva Abstract Our purpose was to investigate in human neurons the neuroprotective pathways induced by Fractalkine (FKN) against glutamate receptor-induced excitotoxicity. CX3CR1 and FKN are expressed constitutively in the tested human embryonic primary neurons and SK-N-SH, a human neuroblastoma cell line. Microfluorometry assay demonstrated that CX3CR1 was functional in 44% of primary neurons and in 70% of SK-N-SH. Fractalkine induced ERK1/2 phosphorylation within 1 min and Akt phosphorylation after 10 min, and both phosphorylation decreased after 20 min. No p38 and SAPK/JNK activation was observed after FKN treatment. Application of FKN triggered a 53% reduction of the NMDA-induced neuronal calcium influx, which was insensitive to pertussis toxin and LY294002 an inhibitor of Akt pathway, but abolished by PD98059, an ERK1/2 pathway inhibitor. Moreover, FKN significantly reduced neuronal NMDA-induced apoptosis, which was pertussis toxin insensitive and abolished in presence of PD98059 and LY294002. In conclusion, FKN protected human neurons from NMDA-mediated excitotoxicity in at least two ways with different kinetics: (i) an early ERK1/2 activation which reduced NMDA-mediated calcium flux; and (ii), a late Akt activation associated with the previously induced ERK1/2 activation. [source] c-Src kinase activation regulates preprotachykinin gene expression and substance P secretion in rat sensory gangliaEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2003Orisa J. Igwe Abstract Increased synthesis of substance P (SP) in the dorsal root ganglia (DRG) and enhanced axonal transport to and secretion from the primary afferent sensory neurons might enhance pain signalling in the spinal dorsal horn by modifying pronociceptive pathways. IL-1, increases SP synthesis by enhancing the expression of preprotachykinin (PPT) mRNA encoding for SP and other tachykinins in the DRG. Stimulation of IL-1 receptor by IL-1, may induce the phosphorylation of tyrosine residues in many effector proteins through the activation of p60c-src kinase. The hypothesis that the synthesis of SP in and secretion from the primary sensory ganglia are regulated by the activation of p60c-src kinase induced by IL-1, was tested. Pretreatment of DRG neurons in culture with herbimycin A, genistein or PP2, three structurally different nonreceptor tyrosine kinase inhibitors that act by different mechanisms, decreased the kinase activity of p60c-src induced by the activation of IL-1 receptor. PP3, a negative control for the Src family of tyrosine kinase inhibitor PP2 had no effect. Herbimycin A and genistein also decreased IL-1,-induced expression of PPT mRNA-encoding transcripts and the levels of SP-li synthesized in the cells and secreted into the culture medium in a concentration-dependent manner. SB 203580 [a p38 mitogen-activated protein kinase (p38 MAPK) inhibitor] and PD 98059 (a p44/42 MAPK kinase inhibitor) were ineffective in modulating IL-1,-induced SP synthesis and secretion, and p60c-src kinase activity in DRG neurons. Whereas, IL-1 receptor antagonist and cycloheximide inhibited IL-1,-evoked secretion of SP-like immunoreactivity (SP-li), actinomycin D decreased it significantly but did not entirely abolish it. These findings show that phosphorylation of specific protein tyrosine residue(s) following IL-1 receptor activation might play a key role in IL-1, signalling to modulate PPT gene expression and SP secretion in sensory neurons. In view of the role of SP as an immunomodulator, these studies provide a new insight into neural-immune intercommunication in pain regulation in the sensory ganglia through the IL-1,-induced p60c-src activation. [source] Antipsoriatic drug anthralin induces EGF receptor phosphorylation in keratinocytes: requirement for H2O2 generationEXPERIMENTAL DERMATOLOGY, Issue 2 2004Dominik Peus Abstract: Even though anthralin is a well-established topical therapeutic agent for psoriasis, little is known about its effects and biochemical mechanisms of signal transduction. In contrast to a previous report, we found that anthralin induced time- and concentration-dependent phosphorylation of epidermal growth factor receptor in primary human keratinocytes. Four lines of evidence show that this process is mediated by reactive oxygen species. First, we found that anthralin induces time-dependent generation of H2O2. Second, there is a correlation between a time-dependent increase in anthralin-induced epidermal growth factor receptor phosphorylation and H2O2 generation. Third, the structurally different antioxidants n -propyl gallate and N -acetylcysteine inhibited epidermal growth factor receptor phosphorylation induced by anthralin. Fourth, overexpression of catalase inhibited this process. The epidermal growth factor receptor-specific tyrosine kinase inhibitor PD153035 abrogated anthralin-induced epidermal growth factor receptor phosphorylation and activation of extracellular-regulated kinase 1/2. These findings establish the following sequence of events: (1) H2O2 generation, (2) epidermal growth factor receptor phosphorylation, and (3) extracellular-regulated kinase activation. Our data identify anthralin-induced reactive oxygen species and, more specifically, H2O2 as an important upstream mediator required for ligand-independent epidermal growth factor receptor phosphorylation and downstream signaling. [source] The hinge region operates as a stability switch in cGMP-dependent protein kinase I,FEBS JOURNAL, Issue 9 2007Arjen Scholten The molecular mechanism of cGMP-dependent protein kinase activation by its allosteric regulator cyclic-3,,5,-guanosine monophosphate (cGMP) has been intensely studied. However, the structural as well as thermodynamic changes upon binding of cGMP to type I cGMP-dependent protein kinase are not fully understood. Here we report a cGMP-induced shift of Gibbs free enthalpy (,,GD) of 2.5 kJ·mol,1 as determined from changes in tryptophan fluorescence using urea-induced unfolding for bovine PKG I,. However, this apparent increase in overall stability specifically excluded the N-terminal region of the kinase. Analyses of tryptic cleavage patterns using liquid chromatography-coupled ESI-TOF mass spectrometry and SDS/PAGE revealed that cGMP binding destabilizes the N-terminus at the hinge region, centered around residue 77, while the C-terminus was protected from degradation. Furthermore, two recombinantly expressed mutants: the deletion fragment ,1-77 and the trypsin resistant mutant Arg77Leu (R77L) revealed that the labile nature of the N-terminus is primarily associated with the hinge region. The R77L mutation not only stabilized the N-terminus but extended a stabilizing effect on the remaining domains of the enzyme as well. These findings support the concept that the hinge region of PKG acts as a stability switch. [source] The P2Y1 receptor mediates ADP-induced p38 kinase-activating factor generation in human plateletsFEBS JOURNAL, Issue 8 2000Carol Dangelmaier U46619, a thromboxane A2 mimetic, but not ADP, caused activation of p38 mitogen activated protein (MAP) kinase in aspirin-treated platelets. In nonaspirinated human platelets ADP activated p38 MAP kinase in both a time-and concentration-dependent manner, suggesting that ADP-induced p38 MAP kinase activation requires generation of thromboxane A2. However, neither a thromboxane A2/prostaglandin H2 receptor antagonist SQ29548 and a thromboxane synthase inhibitor, furegrelate, either alone or together, nor indomethacin blocked ADP-induced p38 kinase activation in nonaspirinated platelets. Other cycloxygenase products, PGE2, PGD2, and PGF2,, failed to activate p38 kinase in aspirin-treated platelets. Hence, ADP must be generating an agonist, other than thromboxane A2, via an aspirin-sensitive pathway, which is capable of activating p38 kinase. AR-C66096, a P2TAC (platelet ADP receptor coupled to inhibition of adenylate cyclase) antagonist, did not inhibit ADP-induced p38 MAP kinase activation. The P2X receptor selective agonist, ,,,-methylene ATP, failed to activate p38 MAP kinase. On the other hand, the P2Y1 receptor selective antagonist, adenosine-2,-phosphate-5,-phosphate inhibited ADP-induced p38 kinase activation in a concentration-dependent manner, indicating that the P2Y1 receptor alone mediates ADP-induced generation of the p38 kinase-activating factor. These results demonstrate that ADP causes the generation of a factor in human platelets, which can activate p38 kinase, and that this response is mediated by the P2Y1 receptor. Neither the P2TAC receptor nor the P2X1 receptor has any significant role in this response. [source] Role of Chk1 and Chk2 in Ara-C-induced differentiation of human leukemia K562 cellsGENES TO CELLS, Issue 2 2005Kazuchika Takagaki Human chronic myelogenous leukemia K562 cells are relatively resistant to the anti-metabolite cytosine arabinoside (Ara-C) and, when treated with Ara-C, they differentiate into erythrocytes without undergoing apoptosis. In this study we investigated the mechanism by which Ara-C induces K562 cells to differentiate. We first observed that Ara-C-induced differentiation of these cells is completely inhibited by the radiosensitizing agent caffeine, an inhibitor of ATM and ATR protein kinases. We next found that Ara-C activates Chk1 and Chk2 in the cells, and that the activation of Chk1, but not of Chk2, was almost completely inhibited by caffeine. Proteasome-mediated degradation of Cdc25A and phosphorylation of Cdc25C were induced by Ara-C treatment, presumably due to the activation of Chk2 and Chk1, respectively. To directly observe the effects of checkpoint kinase activation in Ara-C-induced differentiation, we suppressed Chk1 or Chk2 with the Chk1-specific inhibitor Gö6976, by generating cell lines stably over-expressing dominant-negative forms of Chk2, or by siRNA-mediated knock-down of the Chk1 or the Chk2 gene. The results suggest that Ara-C-induced erythroid differentiation of K562 cells depends on both Chk1 and Chk2 pathways. [source] Inhibition of adiponectin production by homocysteine: A potential mechanism for alcoholic liver disease,HEPATOLOGY, Issue 3 2008Zhenyuan Song Although recent evidence suggests that down-regulation of production of the adipocyte hormone adiponectin has pathophysiological consequences for the development of alcoholic liver disease (ALD), the underlying mechanisms are elusive. Abnormal hepatic methionine-homocysteine metabolism induced by prolonged alcohol exposure has been reported both in clinical and experimental studies of ALD. Here, we conducted both in vivo and in vitro experiments to examine the effects of prolonged alcohol exposure on homocysteine levels in adipose tissue, its potential involvement in regulating adiponectin production, and the consequences for ALD. Chronic alcohol exposure decreased the circulating adiponectin concentration and adiponectin messenger RNA (mRNA) and protein levels in epididymal fat pads. Alcohol feeding induced modest hyperhomocysteinemia and increased homocysteine levels in the epididymal fat pad, which was associated with decreased mRNA levels of cystationine ,-synthase. Betaine supplementation (1.5%, wt/vol) in the alcohol-fed mice reduced homocysteine accumulation in adipose tissue and improved adiponectin levels. Moreover, exogenous homocysteine administration reduced gene expression, protein levels, and secretion of adiponectin in primary adipocytes. Furthermore, rats fed a high-methionine diet (2%, wt/wt) were hyperhomocysteinemic and had decreased adiponectin levels in both plasma and adipose tissue, which was associated with suppressed AMP-activated protein kinase activation in the liver. Mechanistic studies revealed that both inactivation of the extracellular signal regulated kinase 1/2 pathway and induction of endoplasmic reticulum stress response, specifically C/EBP homologous protein expression, may contribute to the inhibitory effect exerted by homocysteine. Conclusion: Chronic alcohol feeding caused abnormal accumulation of homocysteine in adipocytes, which contributes to decreased adiponectin production in ALD. (HEPATOLOGY 2008.) [source] Cell adhesion regulates platelet-derived growth factor,induced MAP kinase and PI-3 kinase activation in stellate cellsHEPATOLOGY, Issue 3 2002Vinicio Carloni The biologic effects of growth factors are dependent on cell adhesion, and a cross talk occurs between growth factors and adhesion complexes. The aim of the present study was to evaluate the influence of cell adhesion on the major intracellular signaling pathways elicited by platelet-derived growth factor (PDGF) in hepatic stellate cells (HSC). PDGF signaling was investigated in an experimental condition characterized by lack of cell adhesion for different intervals of time. Basal and PDGF-induced focal adhesion kinase (FAK) tyrosine phosphorylation was maintained in a condition of cell suspension for 2, 4, and 6 hours, whereas it was completely lost after 12 and 24 hours. We examined MAP kinase activity at 2 and 24 hours, corresponding to the higher and lower levels of FAK phosphorylation. In these experiments, MAP kinase activity correlated with FAK phosphorylation. Stimulation with PDGF was able to cause Ras-GTP loading only in adherent cells. The ability of PDGF to induce phosphatidylinositol 3-kinase (PI 3-K) activity was abrogated in cells maintained in suspension. The Ser473 phosphorylation of Akt was only marginally affected by the lack of cell adhesion. We then evaluated the association of FAK with c-Src. This association was found to be cell adhesion dependent, and it did not appear to be dependent from phosphorylated FAK. These changes in PDGF-induced intracellular signaling were associated with a remarkable reduction of PDGF-proliferative potential in nonadherent cells, although no marked differences in the apoptotic rate were observed. In conclusion, these results suggest that cell adhesion differentially regulates major signaling pathways activated by PDGF in HSC. [source] Key role of proline-rich tyrosine kinase 2 in interleukin-8 (CXCL8/IL-8)-mediated human neutrophil chemotaxisIMMUNOLOGY, Issue 4 2004Vito Di Cioccio Summary The signalling pathways leading to CXCL8/IL-8-induced human neutrophil migration have not been fully characterized. The present study demonstrates that CXCL8 induces tyrosine phosphorylation as well as enzymatic activity of proline-rich tyrosine kinase 2 (Pyk2), a non-receptor protein tyrosine kinase (PTK), in human neutrophils. Induction of Pyk2 tyrosine phosphorylation by CXCL8 is regulated by Src PTK activation, whereas it is unaffected by phosphatidylinositol 3-kinase activation. Inhibition of Pyk2 activation by PP1, a Src PTK inhibitor, is paralleled by the inhibition of CXCL8-mediated neutrophil chemotaxis. Among CXCL8 receptors, Src protein tyrosine kinase activation selectively regulates CXCR1-mediated polymorphonuclear neutrophil (PMN) chemotaxis. Overexpression of PykM, the kinase-dead mutant of Pyk2, blocks CXCL8-induced chemotaxis of HL-60-derived PMN-like cells, thus pinpointing the key role of Pyk2 in CXCL8-induced chemotaxis. [source] Downregulation of erbB3 abrogates erbB2-mediated tamoxifen resistance in breast cancer cellsINTERNATIONAL JOURNAL OF CANCER, Issue 9 2007Bolin Liu Abstract Receptor tyrosine kinase activity is essential for erbB2 (HER2/neu) promotion of breast carcinogenesis, metastasis and therapeutic resistance. erbB2 kinase can be activated by dimerization with another erbB receptor, most of which bind ligands. Of these, the erbB2/erbB3 heterodimer is the most potent oncogenic complex. erbB2 reportedly requires erbB3 to promote cellular proliferation, although this may occur without changes in erbB2 tyrosine kinase activity in some model systems. Our investigations focus on the role(s) of erbB3 in erbB2-associated kinase activity and tamoxifen resistance. Using tumor-derived cell lines from wild type rat c- neu transgenic mice and human breast cancers, we demonstrate that erbB3 plays a critical role in the activation of erbB2 tyrosine kinase activity and erbB2-associated tumorigenesis. Mechanistically, downregulation of erbB3 by specific siRNA reduces erbB2 tyrosine phosphorylation, decreases the PI-3K/Akt signaling, and inhibits mammary/breast cancer cell proliferation and colony formation. Specific erbB3 siRNA sensitizes erbB2 transfected MCF-7 cells (MCF-7/erbB2) to tamoxifen-associated inhibition of both cell growth and colony formation and enhances tamoxifen-induced apoptosis, in contrast to control siRNA transfected MCF-7/erbB2 cells which are tamoxifen-resistant. Our data indicates that erbB2/erbB3 heterodimerization is a prerequisite for erbB2 tyrosine kinase activation in mammary/breast cancer cells and that downregulation of erbB3 inhibits erbB2-associated procarcinogenic activity via inactivation of the PI-3K/Akt pathway. Furthermore, erbB3 also contributes to erbB2-mediated tamoxifen resistance and therefore may be a clinically relevant therapeutic target in addition to erbB2. © 2007 Wiley-Liss, Inc. [source] Her-2/neu and EGFR tyrosine kinase activation predict the efficacy of trastuzumab-based therapy in patients with metastatic breast cancerINTERNATIONAL JOURNAL OF CANCER, Issue 5 2006Gernot Hudelist Abstract Her-2/neu overexpression in human breast cancer leads to an aggressive biological behavior and poor prognosis. Although the anti-Her-2/neu antibody trastuzumab (Herceptin®) has become a valuable therapeutic option for patients with Her-2/neu -overexpressing breast cancer, many patients do not benefit from this therapy. To evaluate the effect of receptor activation on tumor response, we have investigated the phosphorylation status of Her-2/neu and EGFR in 46 Her-2/neu -overexpressing tumor samples from trastuzumab-treated metastatic breast cancer patients by immunohistochemistry. Activated (p)tyr-1248 Her-2/neu was detected in 9 of 46 breast cancers (20%), and activated (p)tyr-845 and (p)tyr-1173 EGFR were both present in 6 tumors (13%) while EGFR was present in 16 cases (35%). ptyr-1248 Her-2/neu showed a trend to correlate with increased response to trastuzumab (p = 0.063), while ptyr-845, ptyr-1173 EGFR and EGFR did not. The presence of ptyr-1248 Her-2/neu and ptyr-845 or ptyr-1173 EGFR, however, was a strong predictor of both response to trastuzumab-based treatment (OR = 8.0, p = 0.021 and OR = 8.0, p = 0.021) and clinical benefit (OR = 5.47, p = 0.041 and OR = 6.22, p = 0.028 multivariate logistic regression analysis). Furthermore, ptyr-845 EGFR and ptyr-1248 Her-2/neu were both independent predictors of progression-free survival (RR = 0.21, p = 0.01 and RR = 0.45, p = 0.026, multivariate analysis). Patients with ptyr-845 EGFR positive tumors also tended toward increased overall survival (RR = 0.17, p = 0.082). Taken together, we have demonstrated that the determination of activated EGFR improves the utility of ptyr-1248 Her-2/neu staining in predicting the clinical outcome of patients undergoing trastuzumab treatment. We hypothesize that the activation state of both Her-2/neu and EGFR are key determinants for trastuzumab efficacy. © 2005 Wiley-Liss, Inc. [source] Signalling responses linked to betulinic acid-induced apoptosis are antagonized by MEK inhibitor U0126 in adherent or 3D spheroid melanoma irrespective of p53 statusINTERNATIONAL JOURNAL OF CANCER, Issue 5 2006Manuel Rieber Abstract MEK1/2 inhibitors like U0126 can potentiate or antagonize the antitumor activity of cytotoxic agents such as cisplatin, paclitaxel or vinblastine, depending on the drug or the target cells. We now investigated whether U0126, differentially regulates melanoma signaling in response to UV radiation or betulinic acid, a drug lethal against melanoma. This report shows that U0126 inhibits early response (ERK) kinase activation and cyclin A expression in wt p53 C8161 melanoma exposed to either UV radiation or betulinic acid. However, U0126 does not protect from UV damage, but counteracts betulinic acid-mediated apoptosis in the same cells. Protection from the latter drug by joint treatment with U0126 was also evident in wt p53 MelJuso melanoma and mutant p53 WM164 melanoma. The latter cells were the most responsive to betulinic acid, showing a selective decline in the cdk4 protein, without a comparable change in other key cell cycle proteins like cdc2, cdk2, cdk7 or cyclin A, prior to apoptosis-associated PARP fragmentation. Laser scanning cytometry also showed that betulinic acid induced a significant increase in chromatin condensation in WM164 melanoma irrespective of whether they were in adherent form or as multicellular spheroids. All these betulinic acid-induced changes were counteracted by U0126. Our data show for the first time that (a) cdk4 protein is an early target of betulinic acid-induced apoptosis and (b) unrestricted ERK signaling favours betulinic acid-induced apoptosis, but this is counteracted by U0126, partly through counteracting chromatin condensation and restoring Akt activation decreased by betulinic acid treatment. © 2005 Wiley-Liss, Inc. [source] TCDD causes suppression of growth and differentiation of MCF10A, human mammary epithelial cells by interfering with their insulin receptor signaling through c-Src kinase and ERK activationJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 6 2005Sujin Park Abstract One of the proposed mechanisms of carcinogenic action of TCDD (=dioxin) on breast cells is that it causes significant inhibition of proper differentiation of mammary duct epithelial cells and thereby increases the number of terminal end buds, which are susceptible to other carcinogens (Fenton et al., Toxicol Sci 2002;67:63,74; Brown et al., Carcinogenesis 1998; 19:1623,1629; Lamartiniere, J Mammary Gland Biol Neoplasia 2002;7:67,76). To address this topic, we selected MCF10A, a line of immortalized normal human breast epithelial cells as an in vitro model. An initial effort was made to optimize the cultural condition of MCF10A cells to promote the cell differentiation effect of insulin. Under this condition, TCDD clearly antagonized the action of insulin only in the presence of cholera toxin that is known to promote the differentiation of normal human breast epithelial cells. To test the hypothesis that TCDD-induced c-Src kinase activation is casually related to this compound's antagonistic action against insulin, we treated MCF10A cells with two c-Src blocking agents, an anti-Src antisense oligonucleotides blocker and a known specific inhibitor of c-Src kinase, PP-2 and studied the effect of insulin and TCDD on cell proliferation. The results showed that, in cells treated with either of these two c-Src blocking agents, the antagonistic effect of TCDD disappeared. It was also found that agents which specifically block the activation of ERK could also abrogate the action of TCDD to suppress insulin signaling. Together, these results indicate that the mechanism of the antagonistic action of TCDD on insulin signaling is mainly mediated through c-Src signaling through activation of ERK. © 2005 Wiley Periodicals, Inc. J Biochem Mol Toxicol 18:322,331, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20040 [source] Regulated expression of syndecan-4 in rat calvaria osteoblasts induced by fibroblast growth factor-2JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2007Shu Jun Song Abstract Fibroblast growth factor-2 (FGF2) is a member of a prominent growth factor family that drives proliferation in a wide variety of cell types, including osteoblasts. The binding and signal transduction triggered by these mitogens is dependent on glycosaminoglycan (GAG) sugars, particularly of the heparan sulfate (HS) class. These are secreted in proteoglycan (PG) complexes, some of which become FGF co-receptors. The syndecans, the transmembrane forms of HSPG of which there are four members, act as multifunctional receptors for a variety of ligands involved in cell-extracellular matrix (ECM) adhesion as well as growth factor binding. To understand the role of syndecans in developing osteoblasts, the effects of exogenous FGF2 on syndecan expression were examined using primary rat calvarial osteoblasts. All four syndecan mRNAs were expressed in the osteoblasts, although only syndecan-4 was upregulated by FGF2 treatment in a dose-dependent manner. This upregulation could be abrogated by pretreatment with the protein synthesis inhibitor cycloheximide, suggesting that the upregulation of syndecan-4 by FGF2 is not a primary response. Osteoblast proliferation and mineralization were enhanced by exogenous FGF2 treatment, but could be specifically diminished by anti-syndecan-4 antibody pretreatment. This treatment also blocked FGF2-induced extracellular signal-regulated kinase activation, but not the expression of the bone-specific transcription factor Runx2. These results demonstrate that mitogen-triggered syndecan-4 expression is an intrinsic part of the pathways subtending osteoblast proliferation and mineralization. J. Cell. Biochem. 100: 402,411, 2007. © 2006 Wiley-Liss, Inc. [source] Colon cancer cell adhesion in response to Src kinase activation and actin-cytoskeleton by non-laminar shear stress,JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2004Vijayalakshmi Thamilselvan Abstract Malignant cells shed from tumors during surgical resection or spontaneous metastasis experience physical forces such as shear stress and turbulence within the peritoneal cavity during irrigation, laparoscopic air insufflation, or surgical manipulation, and within the venous or lymphatic system. Since physical forces can activate intracellular signals that modulate the biology of various cell types in vitro, we hypothesized that shear stress and turbulence might increase colon cancer cell adhesion to extracellular matrix, potentiating metastatic implantation. Primary human malignant colon cancer cells isolated from resected tumors and SW620 were subjected to shear stress and turbulence by stirring cells in suspension at 600 rpm for 10 min. Shear stress for 10 min increased subsequent SW620 colon cancer cell adhesion by 40.0,±,3.0% (n,=,3; P,<,0.001) and primary cancer cells by 41.0,±,3.0% to collagen I when compared to control cells. In vitro kinase assay (1.5,±,0.13 fold) and Western analysis (1.34,±,0.04 fold) demonstrated a significant increase in Src kinase activity in cells exposed shear stress. Src kinase inhibitors PP1 (0.1 µM), PP2 (20 µM), and actin-cytoskeleton stabilizer phalloidin (10 µM) prevented the shear stress stimulated cell adhesion to collagen I. Furthermore, PP2 inhibited basal (50.0,±,2.8%) and prevented shear stress induced src activation but phalloidin pretreatment did not. These results raise the possibility that shear stress and turbulence may stimulate the adhesion of malignant cells shed from colon cancers by a mechanism that requires both actin-cytoskeletal reorganization an independent physical force activation of Src kinase. Blocking this pathway might reduce tumor metastasis during surgical resection. Published 2004 Wiley-Liss, Inc. [source] Diminished contraction-induced intracellular signaling towards mitochondrial biogenesis in aged skeletal muscleAGING CELL, Issue 4 2009Vladimir Ljubicic Summary The intent of this study was to determine whether aging affects signaling pathways involved in mitochondrial biogenesis in response to a single bout of contractile activity. Acute stimulation (1 Hz, 5 min) of the tibialis anterior (TA) resulted in a greater rate of fatigue in old (36 month), compared to young (6 month) F344XBN rats, which was associated with reduced ATP synthesis and a lower mitochondrial volume. To investigate fiber type-specific signaling, the TA was sectioned into red (RTA) and white (WTA) portions, possessing two- to 2.5-fold differences in mitochondrial content. The expression and contraction-mediated phosphorylation of p38, MKK3/6, CaMKII and AMPK, were assessed. Kinase protein expression tended to be higher in fiber sections with lower mitochondrial content, such as the WTA, relative to the RTA muscle, and this was exaggerated in tissues from senescent, compared to young animals. At rest, kinase activation was generally similar between young and old animals, despite the age-related variations in mitochondrial volume. In response to contractile activity, age did not influence the signaling of these kinases in the high-oxidative RTA muscle. However, in the low-oxidative WTA muscle, contraction-induced kinase activation was attenuated in old animals, despite the greater metabolic stress imposed by contractile activity in this muscle. Thus, the reduction of contraction-evoked kinase phosphorylation in muscle from old animals is fiber type-specific, and depends on factors which are, in part, independent of the metabolic milieu within the contracting fibers. These findings imply that the downstream consequences of kinase signaling are reduced in aging muscle. [source] Ecabet sodium promotes the healing of trinitrobenzene-sulfonic-acid-induced ulceration by enhanced restitution of intestinal epithelial cellsJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 7 2010Tomohisa Takagi Abstract Background and Aims:, Ecabet sodium (ES) is a gastric mucosal protective and ulcer-healing agent. Recently enema therapy with ES was found to be effective for the treatment of human ulcerative colitis as well as experimental colitis in an animal model. Whereas ES possesses potential as a novel treatment for ulcerative colitis, its precise mechanism of action remains to be elucidated. In this study, we investigated the therapeutic efficacy of ES in an experimental rat model of colitis, and evaluated the restitution of intestinal epithelial cells treated with ES in vitro. Methods:, Acute colitis was induced with trinitrobenzene sulfonic acid (TNBS) in male Wistar rats. Rats received intrarectal treatment with ES daily starting on day 7 and were sacrificed on day 14 after the administration of TNBS. The distal colon was removed to evaluate various parameters of inflammation. Moreover, wound-healing assays were used to determine the enhanced restitution of rat intestinal epithelial (RIE) cells treated with ES. Results:, Intracolonic administration of ES accelerated TNBS-induced ulcer healing. Increases in the wet weight of the colon after TNBS administration were significantly inhibited by ES treatment. The wound assay revealed ES enhancement of the migration of RIE cells migration through the phosphorylation of extracellular signal-regulated kinase. Conclusion:, Daily administration of an ES enema promoted the healing of intestinal mucosal injury, in part by the enhanced restitution of intestinal epithelial cells via extracellular signal-regulated kinase activation. ES may thus represent a novel therapeutic approach for the treatment of inflammatory bowel disease. [source] Attenuation of proliferation in oligodendrocyte precursor cells by activated microgliaJOURNAL OF NEUROSCIENCE RESEARCH, Issue 8 2010Deanna L. Taylor Abstract Activated microglia can influence the survival of neural cells through the release of cytotoxic factors. Here, we investigated the interaction between Toll-like receptor 4 (TLR4)-activated microglia and oligodendrocytes or their precursor cells (OPC). Primary rat or N9 microglial cells were activated by exposure to TLR4-specifc lipopolysaccharide (LPS), resulting in mitogen-activated protein kinase activation, increased CD68 and inducible nitric oxide synthase expression, and release of the proinflammatory cytokines tumor necrosis factor (TNF) and interleukin-6 (IL-6). Microglial conditioned medium (MGCM) from LPS-activated microglia attenuated primary OPC proliferation without inducing cell death. The microglial-induced inhibition of OPC proliferation was reversed by stimulating group III metabotropic glutamate receptors in microglia with the agonist L-AP4. In contrast to OPC, LPS-activated MGCM enhanced the survival of mature oligodendrocytes. Further investigation suggested that TNF and IL-6 released from TLR4-activated microglia might contribute to the effect of MGCM on OPC proliferation, insofar as TNF depletion of LPS-activated MGCM reduced the inhibition of OPC proliferation, and direct addition of TNF or IL-6 attenuated or increased proliferation, respectively. OPC themselves were also found to express proteins involved in TLR4 signalling, including TLR4, MyD88, and MAL. Although LPS stimulation of OPC did not induce proinflammatory cytokine release or affect their survival, it did trigger JNK phosphorylation, suggesting that TLR4 signalling in these cells is active. These findings suggest that OPC survival may be influenced not only by factors released from endotoxin-activated microglia but also through a direct response to endotoxins. This may have consequences for myelination under conditions in which microglial activation and cerebral infection are both implicated. © 2010 Wiley-Liss, Inc. [source] Antibodies against ,-amyloid reduce a, oligomers, glycogen synthase kinase-3, activation and , phosphorylation in vivo and in vitroJOURNAL OF NEUROSCIENCE RESEARCH, Issue 3 2006Qiu-Lan Ma Abstract Although active and passive immunization against the ,-amyloid peptide (A,) of amyloid plaque-bearing transgenic mice markedly reduces amyloid plaque deposition and improves cognition, the mechanisms of neuroprotection and impact on toxic oligomer species are not understood. We demonstrate that compared to control IgG2b, passive immunization with intracerebroventricular (icv) anti-A, (1,15) antibody into the AD HuAPPsw (Tg2576) transgenic mouse model reduced specific oligomeric forms of A,, including the dodecamers that correlate with cognitive decline. Interestingly, the reduction of soluble A, oligomers, but not insoluble A,, significantly correlated with reduced , phosphorylation by glycogen synthase kinase-3, (GSK-3,), a major , kinase implicated previously in mediating A, toxicity. A conformationally-directed antibody against amyloid oligomers (larger than tetramer) also reduced A, oligomer-induced activation of GSK3, and protected human neuronal SH-SY5Y cells from A, oligomer-induced neurotoxicity, supporting a role for A, oligomers in human , kinase activation. These data suggest that antibodies that are highly specific for toxic oligomer subspecies may reduce toxicity via reduction of GSK-3,, which could be an important strategy for Alzheimer's disease (AD) therapeutics. © 2005 Wiley-Liss, Inc. [source] Differential Effects of Ethanol on Insulin-Like Growth Factor-I Receptor SignalingALCOHOLISM, Issue 2 2000Andrea E.M. Seiler Background: Activation of the insulin-like growth factor I receptor (IGF-IR) by its ligands IGF-I and IGF-II induces cell proliferation and protects against apoptosis. Ethanol inhibits IGF-IR tyrosine autophosphorylation, which subsequently interferes with the activation of key downstream signaling mediators including insulin-receptor substrate-1, phosphatidylinositol 3-kinase, and mitogen-activated protein (MAP) kinase. The ethanol-induced inhibition of IGF-IR signaling reduces mitogenesis and enhances apoptosis. In the current study, we demonstrate that the antiproliferative action of ethanol can be modulated by differential sensitivity of the autophosphorylation of the IGF-IR to ethanol. Methods: A series of subclones was generated from 3T3 cells that express the human IGF-IR. Results: There was considerable variability in the ability of ethanol to inhibit IGF-I-dependent IGF-IR tyrosine autophosphorylation and MAP kinase activation, despite equivalent IGF-IR expression. The IGF-IR was completely resistant to a high concentration of ethanol (150 mM) in several subclones. The sensitivity of IGF-IR autophosphorylation to ethanol correlated directly with the inhibition of IGF-I-mediated MAP kinase activation and cell proliferation. Resistant subclones exhibited features of the transformed phenotype including high MAP kinase activity, partial loss of contact inhibition, and the development of foci at confluency. The IGF-IR isolated from ethanol-resistant cells was similarly resistant to ethanol in autophosphorylation reactions in vitro, whereas ethanol inhibited the autophosphorylation of IGF-IR obtained from sensitive cells. Conclusions: Our findings are the first to demonstrate the modulation of ethanol sensitivity of a tyrosine kinase receptor, and they provide a molecular basis for differential effects of ethanol on cell proliferation. [source] | ||||||||||||||||||||||||||||||||||