• Molecules and Cells
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• 제20권2호
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• pp.196-200
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• 2005

The neurofibromatosis type2 (NF2) tumor suppressor gene product, merlin, is structurally related to the ezrin-radixin-moesin (ERM) family of proteins that anchor the actin cytoskeleton to specific membrane proteins and participate in cell signaling. However, the basis of the tumor suppressing activity of merlin is not well understood. Previously, we identified a role of merlin as an inhibitor of the Ras-ERK signaling pathway. Recent studies have suggested that phosphorylation of merlin, as of other ERM proteins, may regulate its function. To determine whether phosphorylation of merlin affects its suppression of Ras-ERK signaling, we generated plasmids expressing full-length merlin with substitutions of serine 518, a potential phosphorylation site. A substitution that mimics constitutive phosphorylation (S518D) abrogated the ability of merlin to suppress effects of the Ras-ERK signaling pathway such as Ras-induced SRE transactivation, Elk-mediated SRE transactivation, Ras-induced ERK phosphorylation and Ras-induced focus formation. On the other hand, an S518A mutant, which mimics nonphosphorylated merlin, acted like wild type merlin. These observations show that mimicking merlin phosphorylation impairs not only growth suppression by merlin but also its inhibitory action on the Ras-ERK signaling pathway.

• Archives of Pharmacal Research
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• 제26권7호
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• pp.545-553
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• 2003

The expression of cyclooxygenase-2 (COX-2) is a characteristic response to inflammation, which can be inhibited with sodium salicylate. IL-1$\beta$ and TNF-$\alpha$ can induce extracellular signal-regulated kinase (ERK), IKK, IkB degradation and NF-$\kappa$B activation. Salicylate inhibited the IL-1$\beta$ and TNF-$\alpha$-induced COX-2 expressions, regulated the activation of ERK, IKK and IkB degradation, and the subsequent activation of NF-$\kappa$B, in neonatal rat ventricular cardiomyocytes. The inhibition of the ERK pathway, with a selective inhibitor, PD098059, blocked the expressions of IL-1$\beta$ and TNF-$\alpha$-induced COX-2 and $PGE_2$ release. The antioxidant, N-acetyl-cysteine, also reduced the glutathione or catalase- attenuated COX-2 expressions in IL-1$\beta$ and TNF-$\alpha$-treated cells. This antioxidant also inhibited the activation of ERK and NF-$\kappa$B in neonatal rat cardiomyocytes. In addition, IL-1$\beta$ and TNF-$\alpha$-stimulated the release of reactive oxygen species (ROS) in the cardiomyocytes. However, salicylate had no inhibitory effect on the release of ROS in the DCFDA assay. The results showed that salicylate inhibited the activation of ERK and IKK, I$\kappa$B degradation and NF-$\kappa$B activation, independently of the release of ROS, which suggested that salicylate exerts its anti-inflammatory action through the inhibition of ERK, IKK, IkB and NF-$\kappa$B, and the resultant COX-2 expression pathway in neonatal rat ventricular cardiomyocytes.

• The Korean Journal of Physiology and Pharmacology
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• 제7권4호
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• pp.239-246
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• 2003

The expression of cyclooxygenase-2 (COX-2) is a characteristic response to inflammation and can be inhibited with sodium salicylate. $TNF-{\alpha}$ plus $IFN-{\gamma}$ can induce extracellular signal-regulated kinase (ERK), IKK, $I{\kappa}B$ degradation and NF-${\kappa}B$ activation. The inhibition of the ERK pathway with selective inhibitor, PD098059, blocked cytokine-induced COX-2 expression and $PGE_2$ release. Salicylate treatment inhibited COX-2 expression induced by $TNF-{\alpha}$/$IFN-{\gamma}$ and regulated the activation of ERK, IKK and $I{\kappa}B$ degradation and subsequent NF-${\kappa}B$ activation in MC3T3E1 osteoblasts. Furthermore, antioxidants such as catalase, N-acetyl-cysteine or reduced glutathione attenuated COX-2 expression in combined cytokines-treated cells, and also inhibited the activation of ERK, IKK and NF-${\kappa}B$ in MC3T3E1 osteoblasts. In addition, $TNF-{\alpha}$/$IFN-{\gamma}$ stimulated ROS release in the osteoblasts. However, salicylate had no obvious effect on ROS release in DCFDA assay. The results showed that salicylate inhibited the activation of ERK and IKK, $I{\kappa}B$ degradation and NF-${\kappa}B$ activation independent of ROS release and suggested that salicylate exerts its anti-inflammatory action in part through inhibition of ERK, IKK, $I{\kappa}B$, $NF-{\kappa}B$ and resultant COX-2 expression pathway.

• Archives of Reconstructive Microsurgery
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• 제14권2호
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• pp.85-94
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• 2005

Purpose: This study was to evaluate the effect of ${\alpha}-lipoic$ acid, a potent free radical scavenger, on the expression of active form of extracellular signal-regulated kinase (pERK1/2) proteins from hindlimb muscles of rats following ischemia-reperfusion injury. Material and methods: 64 health, $280{\sim}350\;g$ weighted Sprague-Dawley male rats were used. In order to make a muscle flap, the gastrocnemius (GC) and soleus (SOL) muscles were dissected and elevated. The popliteal artery was occluded for 4hours and reperfused for 10 minutes, 30 minutes, 1 hour, 2 hours and 4 hours, respectively. Results: The ischemia by occlusion of the popliteal artery itself caused a minimal change in expression of phosphorylated form of proteins observed in hindlimb muscle. In contrast, after 4 hours of ischemia, immunoreactivity for pERK1/2 in the GC muscle showed dual peaks at 10 minutes and 4 hours after reperfusion. In ${\alpha}-lipoic$ acid treated group, the expression of pERK1/2 was increased significantly compared to I/R-only group. Conclusion: These results suggest that ${\alpha}-lipoic$ acid may protect I/R injury of the skeletal muscle through free radical scavening and activation of intracellular pERK1/2 expression.

• Molecules and Cells
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• 제39권3호
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• pp.266-279
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• 2016

The mechanism by which 12-O-tetradecanoylphorbol-13-acetate (TPA) bypasses cellular senescence was investigated using human diploid fibroblast (HDF) cell replicative senescence as a model. Upon TPA treatment, protein kinase C (PKC) ${\alpha}$ and $PKC{\beta}1$ exerted differential effects on the nuclear translocation of cytoplasmic pErk1/2, a protein which maintains senescence. $PKC{\alpha}$ accompanied pErk1/2 to the nucleus after freeing it from $PEA-15pS^{104}$ via $PKC{\beta}1$ and then was rapidly ubiquitinated and degraded within the nucleus. Mitogen-activated protein kinase docking motif and kinase activity of $PKC{\alpha}$ were both required for pErk1/2 transport to the nucleus. Repetitive exposure of mouse skin to TPA downregulated $PKC{\alpha}$ expression and increased epidermal and hair follicle cell proliferation. Thus, $PKC{\alpha}$ downregulation is accompanied by in vivo cell proliferation, as evidenced in 7, 12-dimethylbenz(a)anthracene (DMBA)-TPA-mediated carcinogenesis. The ability of TPA to reverse senescence was further demonstrated in old HDF cells using RNA-sequencing analyses in which TPA-induced nuclear $PKC{\alpha}$ degradation freed nuclear pErk1/2 to induce cell proliferation and facilitated the recovery of mitochondrial energy metabolism. Our data indicate that TPA-induced senescence reversal and carcinogenesis promotion share the same molecular pathway. Loss of $PKC{\alpha}$ expression following TPA treatment reduces pErk1/2-activated SP1 biding to the $p21^{WAF1}$ gene promoter, thus preventing senescence onset and overcoming G1/S cell cycle arrest in senescent cells.

• BMB Reports
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• 제45권12호
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• pp.724-729
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• 2012

In this study, we evaluated the anti-melanogenesis effects of Caffeoylserotonin (CaS) in B16 melanoma cells. Treatment with CaS reduced the melanin content and tyrosinase (TYR) activity in B16 melanoma cells in a dose-dependent manner. CaS inhibited the expression of melanogenesis-related proteins, including microphthalmia-associated transcription factor (MITF), TYR, and tyrosinase-related protein-1 (TRP-1), but not TRP-2. ${\alpha}$-MSH is known to interact with melanocortin 1 receptor (MC1R) thus activating adenylyl cyclase and increasing intracellular cyclic AMP (cAMP) levels. Furthermore, cAMP activates extracellular signal-regulated kinase 2 (ERK2) via phosphorylation, which phosphorylates MITF, thereby targeting the transcription factor to proteasomes for degradation. The CaS reduced intracellular cAMP levels to unstimulated levels and activated ERK phosphorylation within 30 min. The ERK inhibitor PD98059 abrogated the suppressive effect of CaS on ${\alpha}$-MSH-induced melanogenesis. Based on this study, the inhibitory effects of CaS on melanogenesis are derived from the downregulation of MITF signaling via the inhibition of intracellular cAMP levels, as well as acceleration of ERK activation.

• Bulletin of the Korean Chemical Society
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• 제32권8호
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• pp.2817-2819
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• 2011

• Biomolecules & Therapeutics
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• 제18권1호
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• pp.24-31
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• 2010

Taurine, 2-aminoethanesulfonic acid, is an abundant free amino acid present in brain cells and exerts many important biological functions such as anti-convulsant, modulation of neuronal excitability, regulation of learning and memory, anti-aggressiveness and anti-alcoholic effects. In the present study, we investigated to explore whether taurine has any protective actions against oxidative stress-induced damages in neuronal cells. ERK I/II regulates signaling pathways involved in nitric oxide (NO) and reactive oxygen species (ROS) production and plays a role in the regulation of cell growth, and apoptosis. We have found that taurine significantly inhibited AMPA induced cortical depolarization in the Grease Gap assays using rat cortical slices. Taurine also inhibited AMPA-induced neuronal cell damage in MTT assays in the differentiated SH-SY5Y cells. When the neuronal cells were treated with $H_2O_2$, levels of NO were increased; however, taurine pretreatment decreased the NO production induced by $H_2O_2$ to approximately normal levels. Interestingly, taurine treatment stimulated ERK I/II activity in the presence of AMPA or $H_2O_2$, suggesting the potential role of ERK I/II in the neuroprotection of taurine. Taken together, taurine has significant neuroprotective actions against AMPA or $H_2O_2$ induced damages in neuronal cells, possibly via activation of ERK I/II.

• Biomolecules & Therapeutics
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• 제22권6호
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• pp.503-509
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• 2014

Paraquat has been suggested to induce apoptosis by generation of reactive oxygen species (ROS). However, little is known about the mechanism of paraquat-induced apoptosis. Here, we demonstrate that extracellular signal-regulated protein kinase (ERK) is required for paraquat-induced apoptosis in NIH3T3 cells. Paraquat treatment resulted in activation of ERK, and U0126, inhibitors of the MEK/ERK signaling pathway, prevented apoptosis. Moreover, paraquat-induced apoptosis was associated with cytochrome C release, which could be prevented by treatment with the MEK inhibitors. Taken together, our findings suggest that ERK activation plays an active role in mediating paraquat-induced apoptosis of NIH3T3 cells.

• BMB Reports
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• 제34권1호
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• pp.85-89
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• 2001

Both topoisomerase $II{\alpha}$ and $II{\beta}$ east as phosphoproteins in the cells. Recently it was reported that DNA topoisomerase $II{\alpha}$ associates with and is phosphorylated by the extracellular signal-regulated kinase 2 (ERK2). Also, ERK2 stimulates the activity of topoisomerase II by a phosphorylation-independent manner [Shapiro et al., (1999) Mol. Cell. Biol. 19, 3551-3560]. In this study, a yeast two-hybrid system was used to investigate the binding site between topoisomerase $II{\alpha}$ or $II{\beta}$ and ERK2. The two-hybrid test clearly showed that topoisomerase $II{\beta}$ residues 1099-1263, and topoisomerase $II{\alpha}$ residues 1078-1182, mediate the interaction with ERK2, and that the leucine zipper motifs of topoisomerase $II{\alpha}$ and $II{\beta}$ are not required for its physical binding to ERK2. Our results suggest that topoisomerase $II{\beta}$ residues 1099-1263, and topoisomerase $II{\alpha}$ residues 1078-1182, may be common binding sites for activator proteins.