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Ras Pathway (ras + pathway)
Selected AbstractsUV Exposure, Genetic Targets in Melanocytic Tumors and Transgenic Mouse Models,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2005Frank R. de Gruijl ABSTRACT The genetic changes and corruption of kinase activity in melanomas appear to revolve around a central axis: mitogenic signaling along the RAS pathway down to transcription regulation by pRB. Epidemiological studies point to the importance of ultraviolet (UV) radiation in the etiology of melanoma, but where and how UV radiation is targeted to contribute to the oncogenic signaling remains obscure. Animal models of melanoma genesis could serve to clarify this issue, but many of these models are not responsive to UV exposure. Most interesting advances have been made by using transgenic mice that carry genetic defects that are known to be relevant to human melanoma: specifically, dysfunction in the tumor suppressive action of p161NK4a or a receptor tyrosine kinase/RAS pathway, that is constitutively activated in melanocytes. The latter types of mice appear to be most responsive to (neonatal) UV exposure. Whether this is due to a general increase in target cells by melanocytosis and a paucity or complete lack of pigment, or a possible UV-induced response of the promoter,enhancer of the transgene or a genuinely independent and additional genetic alteration caused by UV exposure needs to be established. Importantly, the full effect of UV radiation needs to be ascertained in mice with different pigmentation by varying the wavelengths, UV-B versus UV-A1, and the exposure schedules, i.e. neonatal versus adult and chronic versus intermittent overexposure. Intermittent UV-B overexposure deserves special attention because it most strongly evokes proliferative responses in melanocytes. [source] Pathophysiology of Target-Organ Disease: Does Angiotensin II Remain the Key?JOURNAL OF CLINICAL HYPERTENSION, Issue 2007Ronald G. Victor MD Basic research provides an increasingly compelling rationale for renin-angiotensin system (RAS) blockade in hypertension treatment and cardiovascular risk reduction. Clinical trials addressing blood pressure-independent effects of angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers, however, have yielded mixed results, in part because of incomplete RAS blockade. Animal studies have shed new light on the complexity of RAS pathways involved in the induction of target-organ damage. New outcomes trials are under way to explore the full potential of more complete RAS blockade with regard to cardiovascular target-organ protection. [source] NO-induced neuroprotection in ischemic preconditioning stimulates mitochondrial Mn-SOD activity and expression via RAS/ERK1/2 pathwayJOURNAL OF NEUROCHEMISTRY, Issue 4 2007A. Scorziello Abstract To identify the transductional mechanisms responsible for the neuroprotective effect of nitric oxide (NO) during ischemic preconditioning (IPC), we investigated the effects of this gaseous mediator on mitochondrial Mn-superoxide dismutase (Mn-SOD) expression and activity. In addition, the possible involvement of Ras/extracellular-regulated kinase (ERK) ERK1/2 pathway in preserving cortical neurons exposed to oxygen and glucose deprivation (OGD) followed by reoxygenation was also examined. Ischemic preconditioning was obtained by exposing neurons to a 30-min sublethal OGD (95% N2 and 5% CO2). Then, after a 24-h interval, neurons were exposed to 3 h of OGD followed by 24 h of reoxygenation (OGD/Rx). Our results revealed that IPC reduced cytochrome c (cyt c) release into the cytosol, improved mitochondrial function, and decreased free radical production. Moreover, it induced an increase in nNOS expression and NO production and promoted ERK1/2 activation. These effects were paralleled by an increase in Mn-SOD expression and activity that persisted throughout the following OGD phase. When the neurons were treated with L-NAME, a well known NOS inhibitor, the increase in Mn-SOD expression occurring during IPC was reduced and, as a result, IPC-induced neuroprotection was prevented. Similarly, when ERK1/2 was inhibited by its selective inhibitor PD98059, the increase in Mn-SOD expression observed during IPC was almost completely abolished. As a result, its neuroprotective effect on cellular survival was thwarted. The present findings indicate that during IPC the increase in Mn-SOD expression and activity are paralleled by NO production. This suggests that NO neuroprotective role occurs through the stimulation of Mn-SOD expression and activity. In particular, NO via Ras activation stimulates downstream ERK1/2 cascade. This pathway, in turn, post-transcriptionally activates Mn-SOD expression and activity, thus promoting neuroprotection during preconditioning. [source] BRAF V599E Mutation is Not Age Dependent: It is Present in Common Melanocytic Nevi in Both Children and AdultsJOURNAL OF CUTANEOUS PATHOLOGY, Issue 1 2005J. Cohen BRAF encodes a serine-threonine kinase, which acts in the RAS/RAF/MAPK pathway transducing regulatory signals from RAS to MEK1/2. Somatic mutations in BRAF have been identified in 53,80% of primary melanomas and 70,90% of common melanocytic nevi. More than 90% of these mutations consist of a valine to glutamate substitution at codon 599 (V599E) of exon 15. While a high prevalence of BRAF mutations in common melanocytic nevi has been reported in adults, nevi in children have not been studied. Of interest, we have previously shown that Spitz nevi in children do not harbor mutations in BRAF. To investigate the association of BRAF mutations with patient age, we studied common melanocytic nevi in children for the V599E activating mutation. Tumor cells were microdissected from 6 common melanocytic nevi in children 10 years of age or younger, and analyzed for the V599E mutation in BRAF by allele-specific PCR and gel electrophoresis. In 6 of 6 (100%) nevi, the V599E mutant allele was observed. Our data suggest that similar genetic pathways are involved in the development of common melanocytic nevi in children and adults. The absence of BRAF mutations in Spitz nevi in children is therefore associated with tumor type, not patient age. [source] Drosophila female sterile (1) homeotic is a multifunctional transcriptional regulator that is modulated by Ras signalingDEVELOPMENTAL DYNAMICS, Issue 3 2008Brian L. Florence Abstract The Drosophila (fs(1)h) gene encodes small (Fs(1)hS) and large (Fs(1)hL) chromatin-binding BET protein transcription factor isoforms. Zygotic mutations cause either lethality or female sterility, whereas maternal mutations cause segmental deletions and thoracic homeotic transformations. Here, we describe novel fs(1)h embryonic phenotypes: homeosis of the head in zygotic mutants and deletion of head and tail regions in maternal mutants, similar to those caused by dominant torso (torD) alleles. tor activates transcription of tailless (tll) and hückebein (hkb) by means of a canonical Ras pathway, through inactivation of Groucho (Gro), Capicua (Cic) and, possibly, Grainy-head (Grh) repressors. Expression of both tailless and hückebein are de-repressed in fs(1)h maternal mutants, as in torD, gro, grh, and cic mutant animals, indicating fs(1)h is also necessary for tll and hkb repression. These data link Ras signaling with modulation of a chromatin-binding transcription factor, Fs(1)h, suggesting a novel mechanism by which Ras can modulate gene expression. Developmental Dynamics 237:554,564, 2008. © 2008 Wiley-Liss, Inc. [source] Differential actions of p60c-Src and Lck kinases on the Ras regulators p120-GAP and GDP/GTP exchange factor CDC25MmFEBS JOURNAL, Issue 11 2001Carmela Giglione It is known that the human Ras GTPase activating protein (GAP) p120-GAP can be phosphorylated by different members of the Src kinase family and recently phosphorylation of the GDP/GTP exchange factor (GEF) CDC25Mm/GRF1 by proteins of the Src kinase family has been revealed in vivo[Kiyono, M., Kaziro, Y. & Satoh, T. (2000) J. Biol. Chem.275, 5441,5446]. As it still remains unclear how these phosphorylations can influence the Ras pathway we have analyzed the ability of p60c-Src and Lck to phosphorylate these two Ras regulators and have compared the activity of the phosphorylated and unphosphorylated forms. Both kinases were found to phosphorylate full-length or truncated forms of GAP and GEF. The use of the catalytic domain of p60c-Src showed that its SH3/SH2 domains are not required for the interaction and the phosphorylation of both regulators. Remarkably, the phosphorylations by the two kinases were accompanied by different functional effects. The phosphorylation of p120-GAP by p60c-Src inhibited its ability to stimulate the Ha-Ras-GTPase activity, whereas phosphorylation by Lck did not display any effect. A different picture became evident with CDC25Mm; phosphorylation by Lck increased its capacity to stimulate the GDP/GTP exchange on Ha-Ras, whereas its phosphorylation by p60c-Src was ineffective. Our results suggest that phosphorylation by p60c-Src and Lck is a selective process that can modulate the activity of p120-GAP and CDC25Mm towards Ras proteins. [source] Role of the Rap1 GTPase in astrocyte growth regulationGLIA, Issue 3 2003Anthony J. Apicelli Abstract Tuberous sclerosis complex (TSC) is an autosomal dominant syndrome in which affected individuals develop nervous system abnormalities that might reflect astrocyte dysfunction. The TSC2 gene product, tuberin, encodes a GTPase-activating protein (GAP) domain, which regulates the activity of Rap1 in vitro. To determine whether dysregulated Rap1, resulting from TSC2 inactivation, leads to increased astrocyte proliferation in vivo, we generated transgenic mice expressing activated Rap1G12V specifically in astrocytes. We observed no statistically significant difference in the number of astrocytes between wild-type and GFAP-Rap1G12V littermates in vivo; however, during log-phase growth, we observed a 25% increase in GFAP-Rap1G12V astrocyte doubling times compared to wild-type controls. This decreased proliferation was associated with delayed MAP kinase, but not AKT, activation. Lastly, to determine whether constitutive Rap1 activation could reverse the increased astrocyte proliferation observed in transgenic mice expressing oncogenic RasG12V, we generated transgenic mice expressing both RasG12V and Rap1G12V in astrocytes. These double transgenic mice showed a striking reversion of the RasG12V astrocyte growth phenotype. Collectively, these results argue that the tumor suppressor properties of tuberin are unlikely to be related to Rap1 inactivation and that Rap1 inhibits mitogenic Ras pathway signaling in astrocytes. GLIA 42:225,234, 2003. © 2003 Wiley-Liss, Inc. [source] Ras/ERK signalling in cannabinoid tolerance: from behaviour to cellular aspectsJOURNAL OF NEUROCHEMISTRY, Issue 4 2005Tiziana Rubino Abstract We investigated the role of the Ras/extracellular-regulated kinase (ERK) pathway in the development of tolerance to ,9 -tetrahydrocannabinol (THC)-induced reduction in spontaneous locomotor activity by a genetic (Ras-specific guanine nucleotide exchange factor (Ras-GRF1) knock-out mice) and pharmacological approach. Pre-treatment of wild-type mice with SL327 (50 mg/kg i.p.), a specific inhibitor of mitogen-activated protein kinase kinase (MEK), the upstream kinase of ERK, fully prevented the development of tolerance to THC-induced hypolocomotion. We investigated the impact of the inhibition of ERK activation on the biological processes involved in cannabinoid tolerance (receptor down-regulation and desensitization), by autoradiographic cannabinoid CB1 receptor and cannabinoid-stimulated [35S]GTP,S binding studies in subchronically treated mice (THC, 10 mg/kg s.c., twice a day for 5 days). In the caudate putamen and cerebellum of Ras-GRF1 knock-out mice and SL327 pre-treated wild-type mice, CB1 receptor down-regulation and desensitization did not occur, suggesting that ERK activation might account for CB1 receptor plasticity involved in the development of tolerance to THC hypolocomotor effect. In contrast, the hippocampus and prefrontal cortex showed CB1 receptor adaptations regardless of the genetic or pharmacological inhibition of the ERK pathway, suggesting regional variability in the cellular events underlying the altered CB1 receptor function. These findings suggest that at least in the caudate putamen and cerebellum, the Ras/ERK pathway is essential for triggering the alteration in CB1 receptor function responsible for tolerance to THC-induced hypomotility. [source] Enhanced cytotoxicity induced by gefitinib and specific inhibitors of the Ras or phosphatidyl inositol-3 kinase pathways in non-small cell lung cancer cellsINTERNATIONAL JOURNAL OF CANCER, Issue 1 2006Maarten L. Janmaat Abstract In this study, we have characterized a panel of NSCLC cell lines with differential sensitivity to gefitinib for activating mutations in egfr, pik3ca, and k-ras, and basal protein expression levels of PTEN. The egfr mutant NSCLC cell line H1650 as well as the egfr wild type cell lines H292 and A431 were highly sensitive to gefitinib treatment, indicating that other factors determine gefitinib-sensitivity in egfr wild type cells. Activating k-ras mutations were specifically detected in gefitinib-resistant cells, suggesting that the occurrence of k-ras mutations is correlated with resistance to EGFR antagonists. No pik3ca mutations were detected within the panel of cell lines, and PTEN protein expression levels did not correlate with gefitinib sensitivity. Gefitinib effectively blocked Akt and Erk phosphorylation in two gefitinib-sensitive NSCLC cell lines, further supporting our previous findings that persistent activity of the PI3K/Akt and/or Ras/Erk pathways is associated with gefitinib-resistance of NSCLC cell lines. Gefitinib-resistant NSCLC cell lines, showing EGFR-independent activity of the PI3K/Akt or Ras/Erk pathways, were treated with gefitinib in combination with specific inhibitors of mTOR, P13K, Ras, and MEK. Additive cytotoxicity was observed in A549 cells co-treated with gefitinib and the MEK inhibitor U0126 or the farnesyl transferase inhibitor SCH66336 and in H460 cells treated with gefitinib and the PI3K inhibitor LY294002, but not in H460 cells treated with gefitinib and rapamycin. These data suggest that combination treatment of NSCLC cells with gefitinib and specific inhibitors of the PI3K/Akt and Ras/Erk pathways may provide a successful strategy. © 2005 Wiley-Liss, Inc. [source] cAMP blocks MAPK activation and sclerotial development via Rap-1 in a PKA-independent manner in Sclerotinia sclerotiorumMOLECULAR MICROBIOLOGY, Issue 1 2005Changbin Chen Summary Sclerotinia sclerotiorum is a filamentous ascomycete phytopathogen able to infect an extremely wide range of cultivated plants. Our previous studies have shown that increases in cAMP levels result in the impairment of the development of the sclerotium, a highly differentiated structure important in the disease cycle of this fungus. cAMP also inhibits the activation of a S. sclerotiorum mitogen-activated protein kinase (MAPK), which we have previously shown to be required for sclerotial maturation; thus cAMP-mediated sclerotial inhibition is modulated through MAPK. However, the mechanism(s) by which cAMP inhibits MAPK remains unclear. Here we demonstrate that a protein kinase A (PKA)-independent signalling pathway probably mediates MAPK inhibition by cAMP. Expression of a dominant negative form of Ras, an upstream activator of the MAPK pathway, also inhibited sclerotial development and MAPK activation, suggesting that a conserved Ras/MAPK pathway is required for sclerotial development. Evidence from bacterial toxins that specifically inhibit the activity of small GTPases, suggested that Rap-1 or Ras is involved in cAMP action. The Rap-1 inhibitor, GGTI-298, restored MAPK activation in the presence of cAMP, further suggesting that Rap-1 is responsible for cAMP-dependent MAPK inhibition. Importantly, inhibition of Rap-1 is able to restore sclerotial development blocked by cAMP. Our results suggest a novel mechanism involving the requirement of Ras/MAPK pathway for sclerotial development that is negatively regulated by a PKA-independent cAMP signalling pathway. Cross-talk between these two pathways is mediated by Rap-1. [source] Lipid-induced filamentous growth in Ustilago maydisMOLECULAR MICROBIOLOGY, Issue 3 2004Jana Klose Summary The phytopathogenic fungus Ustilago maydis is obligately dependent on infection of maize to complete the sexual phase of its life cycle. Mating interactions between haploid, budding cells establish an infectious filamentous cell type that invades the host, induces large tumours and eventually forms large masses of black spores. The ability to switch from budding to filamentous growth is therefore critical for infection and completion of the life cycle, although the signals that influence the transition have not been identified from the host or the environment. We have found that growth in the presence of lipids promotes a filamentous phenotype that resembles the infectious cell type found in planta. In addition, the ability of the fungus to respond to lipids is dependent on both the cAMP signalling pathway and a Ras/MAPK pathway; these pathways are known to regulate mating, filamentous growth and pathogenesis in U. maydis. Overall, these results lead us to hypothesize that lipids may represent one of the signals that promote and maintain the filamentous growth of the fungus in the host environment. [source] Increased expression of the heterogeneous nuclear ribonucleoprotein K in pancreatic cancer and its association with the mutant p53INTERNATIONAL JOURNAL OF CANCER, Issue 2 2010Renyuan Zhou Abstract The heterogeneous nuclear ribonucleoprotein (hnRNP) K is an essential RNA and DNA binding protein involved in gene expression and signal transduction including DNA transcription, RNA splicing, RNA stability and translation. The role of hnRNP K in cancer is relatively understudied. However, several cellular functions strongly indicate that hnRNP K is involved in tumorigenesis. In this study, we investigated the altered protein expression and the subcellular distribution of the hnRNP K protein using tissue microarrays in pancreatic cancer. We showed an increased cytoplasmic hnRNP K in pancreatic cancer. This increase in hnRNP K protein occurs at the posttranscriptional level. We postulate that the cytoplasmic accumulation of hnRNP K will lead to silenced mRNA translation of tumor suppressor genes and thus contributes to pancreatic cancer development. We also demonstrated that knocking down of hnRNP K expression by siRNA inhibited pancreatic cancer cell growth and colony formation. hnRNP K was identified as a member of the p53/HDM2 pathway. Whether hnRNP K interacts with the mutant p53 is not known. Using two different pancreatic cancer cell lines, we can demonstrate that hnRNP K interacts with the mutant p53. The subcellular distribution and function of the mutant p53 and the interaction of hnRNP K/mutant p53 were affected by the Ras/MEK/ERK pathway, growth factors and the specific p53 mutations in pancreatic cancer cells. Since Kras is activated and p53 is mutated in most pancreatic cancers, these data unveiled an important new signaling pathway that linked by hnRNP K and mutant p53 in pancreatic cancer tumorigenesis. [source] ERK signaling leads to mitochondrial dysfunction in extracellular zinc-induced neurotoxicityJOURNAL OF NEUROCHEMISTRY, Issue 2 2010Kai He J. Neurochem. (2010) 114, 452,461. Abstract A zinc-induced signaling pathway leading to extracellular signal-regulated kinase 1/2 (ERK1/2) activation and subsequent neuronal death has been investigated. We find that an extracellular zinc application stimulates biphasic phosphorylation of ERK1/2 and p38 MAPK in rat cultured neurons. The activation of ERK1/2, but not p38, is responsible for zinc neurotoxicity as only U0126, a MEK inhibitor that blocks ERK1/2 phosphorylation, significantly protects cortical neurons from zinc exposure. Over-expression of a dominant negative Ras mutant blocks zinc-induced Elk1-dependent gene expression in neurons, indicating the involvement of Ras activation in the zinc pathway leading to ERK phosphorylation and Elk1 signaling. We also find that zinc treatment results in neuronal mitochondrial hyperpolarization. Importantly, both U0126 and bongkrekic acid, an inhibitor of the mitochondrial adenine nucleotide translocase, effectively reduce zinc-triggered mitochondrial changes. As bongkrekic acid also prevents zinc-triggered neuronal death but not ERK1/2 phosphorylation, activation of MAPK signaling precedes and is required for mitochondrial dysfunction and cell death. These results provide new insight on the mechanism of extracellular zinc-induced toxicity in which the regulation of mitochondrial function by the Ras/MEK/ERK pathway is closely associated with neuronal viability. [source] Phosphorylated Map Kinase (ERK1, ERK2) Expression is Associated with Early Tau Deposition in Neurones and Glial Cells, but not with Increased Nuclear DNA Vulnerability and Cell Death, in Alzheimer Disease, Pick's Disease, Progressive Supranuclear Palsy and Corticobasal DegenerationBRAIN PATHOLOGY, Issue 2 2001I. Ferrer Abnormal tau phosphorylation and deposition in neurones and glial cells is one of the major features in tau pathies. The present study examines the involvement of the Ras/MEK/ERK pathway of tau phosphorylation in Alzheimer disease (AD), Pick's disease (PiD), progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD), by Western blotting, single and double-labelling immunohistochemistry, and p21Ras activation assay. Since this pathway is also activated in several paradigms of cell death and cell survival, activated ERK expression is also analysed with double-labelling immunohistochemistry and in situ end-labelling of nuclear DNA fragmentation to visualise activated ERK in cells with increased nuclear DNA vulnerability. The MEK1 antibody recognises one band of 45 kD that identifies phosphorylation-independent MEK1, whose expression levels are not modified in diseased brains. The ERK antibody recognises one band of 42 kD corresponding to the molecular weight of phosphorylation-independent ERK2; the expression levels, as well as the immunoreactivity of ERK in individual cells, is not changed in AD, PiD, PSP and CBD. The antibody MAPK-P distinguishes two bands of 44 kD and 42 kD that detect phosphorylated ERK1 and ERK2. MAPK-P expression levels, as seen with Western blotting, are markedly increased in AD, PiD, PSP and CBD. Moreover, immunohistochemistry discloses granular precipitates in the cytoplasm of neurones in AD, mainly in a subpopulation of neurones exhibiting early tau deposition, whereas neurones with developed neurofibrillary tangles are less commonly immunostained. MAPK-P also decorates neurones with Pick bodies in PiD, early tau deposition in neurones in PSP and CBD, and cortical achromatic neurones in CBD. In addition, strong MAPK-P immunoreactivity is found in large numbers of tau -positive glial cells in PSP and CBD, as seen with double-labelling immunohistochemistry. Yet no co-localisation of enhanced phosphorylated ERK immunoreactivity and nuclear DNA fragmentation is found in AD, PiD, PSP and CBD. Finally, activated Ras expression levels are increased in AD cases when compared with controls. These results demonstrate increased phosphorylated (active) ERK expression in association with early tau deposition in neurones and glial cells in taupathies, and suggest activated Ras as the upstream activator of the MEK/ERK pathway of tau phosphorylation in AD. [source] Phosphorylation and lipid raft association of fibroblast growth factor receptor-2 in oligodendrocytes,GLIA, Issue 9 2009M. R. Bryant Abstract Fibroblast growth factors (FGFs) and their receptors (FGFRs) initiate diverse cellular responses that contribute to the regulation of oligodendrocyte (OL) function. To understand the mechanisms by which FGFRs elicit these cellular responses, we investigated the phosphorylation of signal transduction proteins and the role of cholesterol-glycosphingolipid-enriched "lipid raft" microdomains in differentiated OLs. Surprisingly, we found that the most abundant tyrosine-phosphorylated protein in OLs was the 120-kd isoform of FGFR2 and that it was phosphorylated even in the absence of FGF2, suggesting a potential ligand-independent function for this receptor. Furthermore, FGFR2, but not FGFR1, was associated with lipid raft microdomains in OLs and myelin (but not in astrocytes). This provides the first evidence for the association of FGFR with TX-100-insoluble lipid raft fractions. FGFR2 phosphorylated the key downstream target, FRS2 in OLs. Raft disruption resulted in loss of phosphorylated FRS2 from lipid rafts, coupled with the loss of Akt but not of Mek or Erk phosphorylation. This suggests that FGFR2-FRS2 signaling in lipid rafts operates via the PI3-Kinase/Akt pathway rather than the Ras/Mek/Erk pathway, emphasizing the importance of microenvironments within the cell membrane. Also present in lipid rafts in OLs and myelin, but not in astrocytes, was a novel 52-kd isoform of FGFR2 that lacked the extracellular ligand-binding region. These results demonstrate that FGFR2 in OLs and myelin possess unique characteristics that are specific both to receptor type and to OLs and provide a novel mechanism to elicit distinct cellular responses that mediate both FGF-dependent and -independent functions. © 2008 Wiley-Liss, Inc. [source] Down-regulation of the PI3-kinase/Akt pathway by ERK MAP kinase in growth factor signalingGENES TO CELLS, Issue 9 2008Hideko Hayashi The ERK MAP kinase and PI3-kinase/Akt pathways are major intracellular signaling modules, which are known to regulate diverse cellular processes including cell proliferation, survival and malignant transformation. However, it has not been fully understood how these two pathways interact with each other. Here, we demonstrate that inhibition of the ERK pathway by the MEK inhibitor U0126 or PD98059 significantly potentiates EGF- and FGF-induced Akt phosphorylation at both Thr308 and Ser473. We also show that hyperactivation of the ERK pathway greatly attenuates EGF- and FGF-induced Akt phosphorylation. Furthermore, the enhanced Akt phosphorylation induced by U0126 is inhibited by the PI3-kinase inhibitor LY294002, and is accompanied by the up-regulation of Ras activity. These results suggest that the ERK pathway inhibition enhances Akt phosphorylation through the Ras/PI3-kinase pathway. Thus, our results demonstrate that the ERK pathway negatively modulates the PI3-kinase/Akt pathway in response to growth factor stimulation. [source] Bradykinin-induced p42/p44 MAPK phosphorylation and cell proliferation via Src, EGF receptors, and PI3-K/Akt in vascular smooth muscle cellsJOURNAL OF CELLULAR PHYSIOLOGY, Issue 3 2005Chuen-Mao Yang In our previous study, bradykinin (BK) exerts its mitogenic effect through Ras/Raf/MEK/MAPK pathway in vascular smooth muscle cells (VSMCs). In addition to this pathway, the non-receptor tyrosine kinases (Src), EGF receptor (EGFR), and phosphatidylinositol 3-kinase (PI3-K) have been implicated in linking a variety of G-protein coupled receptors to MAPK cascades. Here, we investigated whether these different mechanisms participating in BK-induced activation of p42/p44 MAPK and cell proliferation in VSMCs. We initially observed that BK- and EGF-dependent activation of Src, EGFR, Akt, and p42/p44 MAPK and [3H]thymidine incorporation were mediated by Src and EGFR, because the Src inhibitor PP1 and EGFR kinase inhibitor AG1478 abrogated BK- and EGF-dependent effects. Inhibition of PI3-K by LY294002 attenuated BK-induced Akt and p42/p44 MAPK phosphorylation and [3H]thymidine incorporation, but had no effect on EGFR phosphorylation, suggesting that EGFR may be an upstream component of PI3-K/Akt and MAPK in these responses. This hypothesis was supported by the tranfection with dominant negative plasmids of p85 and Akt which significantly attenuated BK-induced Akt and p42/p44 MAPK phosphorylation. Pretreatment with U0126 (a MEK1/2 inhibitor) attenuated the p42/p44 MAPK phosphorylation and [3H]thymidine incorporation stimulated by BK, but had no effect on Akt activation. Moreover, BK-induced transactivation of EGFR and cell proliferation was blocked by matrix metalloproteinase inhibitor GM6001. These results suggest that, in VSMCs, the mechanism of BK-stimulated activation of p42/p44 MAPK and cell proliferation was mediated, at least in part, through activation of Src family kinases, EGFR transactivation, and PI3-K/Akt. Copyright © 2004 Wiley-Liss, Inc. [source] UV Exposure, Genetic Targets in Melanocytic Tumors and Transgenic Mouse Models,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2005Frank R. de Gruijl ABSTRACT The genetic changes and corruption of kinase activity in melanomas appear to revolve around a central axis: mitogenic signaling along the RAS pathway down to transcription regulation by pRB. Epidemiological studies point to the importance of ultraviolet (UV) radiation in the etiology of melanoma, but where and how UV radiation is targeted to contribute to the oncogenic signaling remains obscure. Animal models of melanoma genesis could serve to clarify this issue, but many of these models are not responsive to UV exposure. Most interesting advances have been made by using transgenic mice that carry genetic defects that are known to be relevant to human melanoma: specifically, dysfunction in the tumor suppressive action of p161NK4a or a receptor tyrosine kinase/RAS pathway, that is constitutively activated in melanocytes. The latter types of mice appear to be most responsive to (neonatal) UV exposure. Whether this is due to a general increase in target cells by melanocytosis and a paucity or complete lack of pigment, or a possible UV-induced response of the promoter,enhancer of the transgene or a genuinely independent and additional genetic alteration caused by UV exposure needs to be established. Importantly, the full effect of UV radiation needs to be ascertained in mice with different pigmentation by varying the wavelengths, UV-B versus UV-A1, and the exposure schedules, i.e. neonatal versus adult and chronic versus intermittent overexposure. Intermittent UV-B overexposure deserves special attention because it most strongly evokes proliferative responses in melanocytes. [source] Ultraviolet radiation and skin cancer: molecular mechanismsJOURNAL OF CUTANEOUS PATHOLOGY, Issue 3 2005Mahmoud R. Hussein This electromagnetic energy has both life-giving and life-endangering effects. UV radiation can damage DNA and thus mutagenize several genes involved in the development of the skin cancer. The presence of typical signature of UV-induced mutations on these genes indicates that the ultraviolet-B part of sunlight is responsible for the evolution of cutaneous carcinogenesis. During this process, variable alterations of the oncogenic, tumor-suppressive, and cell-cycle control signaling pathways occur. These pathways include (a) mutated PTCH (in the mitogenic Sonic Hedgehog pathway) and mutated p53 tumor-suppressor gene in basal cell carcinomas, (b) an activated mitogenic ras pathway and mutated p53 in squamous cell carcinomas, and (c) an activated ras pathway, inactive p16, and p53 tumor suppressors in melanomas. This review presents background information about the skin optics, UV radiation, and molecular events involved in photocarcinogenesis. [source] | |||||||||||||||||||||||||