• 대한의생명과학회지
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• 제12권3호
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• pp.249-254
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• 2006

It has been reported that liver is a very important organ to xenotransplantation. Pig is known to be a most suitable species in transplantation of human organs. However, the physiological function of pig hepatocytes is not clear elucidated. Epidermal growth factor (EGF) is known to be a mitogen in various cell systems. Thus, we examined the effect of EGF on cell proliferation and its related signal cascades in primary cultured pig hepatocytes. EGF stimulates cell proliferation in a dose (>1ng/ml) dependent manner. EGF-induced increase of $[^3H]-thymidine$ incorporation was blocked by AG 1478 ($10^{-6}M$, an EGF receptor antagonist) genistein and herbymycin A (tyrosine kinase inhibitors, $10^{-6}M$), suggesting the role of activation and tyrosine phosphorylation of EGF receptor. In addition, EGF-induced increase of $[^3H]-thymidine$ incorporation was prevented by neomycin $(10^{-4}M)$, U73122 $(10^{-5}M)$ (phospholipase C [PLC] inhibitors), staurosporine ($(10^{-8}M)$, or bisindolylmaleimide I $(10^{-6}M)$ (protein kinase C [PKC] inhibitors), suggesting the role of PLC and PKC. Moreover, EGF-induced increase of $[^3H]-thymidine$ incorporation was blocked by PD 98059 (a p44/42 mitogen activated protein kinase [MAPK] inhibitor), SB 203580 (a p38 MAPK inhibitor), and SP 600125 (a JNK inhibitor). EGF increased the translocation of PKC from cytosol to membrane fraction and activated p42/44 MAPK, p38 MAPK and JNK. In conclusion, EGF stimulates cell proliferation via PKC and MAPK in cultured pig hepatocytes.

• BMB Reports
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• 제47권12호
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• pp.685-690
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• 2014

The Ras/Raf/MEK/Erk signaling pathway is important for regulation of cell growth, proliferation, differentiation, survival, and apoptosis in response to a variety of extracellular stimuli. Lack of Erk MAPK activation is observed in several cancer cells despite active activation of Ras. However, little is known about the modulation of Erk1/2 activity by active Ras. Here, we show that overexpression of active H-Ras (H-RasG12R) in NIH3T3 fibroblasts impaired FGF2-induced Erk1/2 phosphorylation, as compared to wild-type cells. Northern blot analysis revealed that prolonged expression of active Ras increased MAP kinase phosphatase 3 (MKP3) mRNA expression, a negative regulator of Erk MAPK. Inhibition of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway abrogated active Ras-induced up-regulation of MKP3 expression, leading to the rescue of Erk1/2 phosphorylation. Our results demonstrated that the Ras/Raf/MEK/Erk signaling cascade is negatively regulated by the PI3K/Aktdependent transcriptional activation of the MKP3 gene.

• 대한약학회:학술대회논문집
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• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2-2
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• pp.75.3-76
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• 2003

The present study was performed to examine mitogen-activated protein kinase associated pathways in mediation of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced cell apoptosis in cultured Jurkat T cells. TCDD significantly decreased cell viability in a concentration-dependent manner (p<0.05 at 10-300 nM). TCDD (10 nM) also time-dependently decreased cell viability (p<0.05 at 12-48 h). c-Jun NH$_2$-terminal kinase was significantly phosphorylated with TCDD treatment in a time dependent manner. (omitted)

• BMB Reports
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• 제49권7호
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• pp.370-375
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• 2016

Ras oncoproteins are small molecular weight GTPases known for their involvement in oncogenesis, which operate in a complex signaling network with multiple effectors. Approximately 25% of human tumors possess mutations in a member of this family. The Raf1/MEK/Erk1/2 pathway is one of the most intensively studied signaling mechanisms. Different levels of regulation account for the inactivation of MAP kinases by MAPK phosphatases in a cell type- and stimuli-dependent manner. In the present study, using three inducible Ras-expressing NIH/3T3 cell lines, we demonstrated that MKP3 upregulation requires the activation of the Erk1/2 pathway, which correlates with the shutdown of this pathway. We also demonstrated, by applying pharmacological inhibitors and effector mutants of Ras, that induction of MKP3 at the protein level is positively regulated by the oncogenic Ras/Raf/MEK/Erk1/2 signaling pathway.

• 대한의생명과학회지
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• 제9권2호
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• pp.59-65
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• 2003

When cells are exposed to proteotoxic stresses such as heat shock, amino acid analogs, and heavy metals, they increase the synthesis of the heat shock proteins (HSPs) by activating the heat shock transcription factor 1 (HSF1), whose activity is controlled via multiple steps including homotrimerization, nuclear translocation, DNA binding, and hyperphosphorylation. Under unstressed conditions, the HSF1 activity is repressed through its constitutive phosphorylation by glycogen synthase kinase 3$\beta$ (GSK3$\beta$), extracellular regulated kinase 1/2 (ERK1/2), and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK). However, the protein kinase (s) responsible for HSF1 hyperphosphorylation and activation is not yet identified. In the present study, we observed that profile of p38 mitogen-activated protein kinase (p38MAPK) activation in response to heat shock was very similar to those of HSF1 hyperphosphorylation and nuclear translocation. Therefore, we investigated whether p38MAPK is involved in the heat shock-induced HSF1 activation and HSP expression. Here we show that the p38MAPK inhibitors, SB202190 and SB203580, but not other inhibitors including the MEK1/2 inhibitor PD98059 and the PI3-K inhibitor LY294002 and wortmannin, suppress HSF1 hyperphosphorylation in response to heat shock and L-azetidine 2-carboxylic acid (Azc), but not to heavy metals. Furthermore, heat shock-induced HSF1-DNA binding and HSP72 expression was specifically prevented by the p38MAPK inhibitors, but not by the MEK1/2 inhibitor and the PI3-K inhibitors. These results suggest that SB202190- and SB203580-sensitive p38MAPK may positively regulate HSP gene regulation in response to heat shock and amino acid analogs.

• Toxicological Research
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• 제20권3호
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• pp.233-239
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• 2004

The present study was designed to determine the impact of mercury on endotoxin-induced inflammatory cytokine expression and corresponding signal transduction in mouse kidney. Male BALB/c mice were exposed continuously to 0, 0.3, 1.5, 7.5, or 37.5 ppm of mercury in drink-ing water for 14 days and at the end of the treatment period, lipopolysaccharide (LPS, 0.5 mg/kg) was injected intraperitoneally 2 h prior to euthanasia. The doses of mercury and LPS did not cause hepatotoxicity or renal toxicity as indicated by unaltered plasma alanine aminotransferase and aspartate aminotransferase levels, and terminal UTP nucleotide end-labeling assay from kidney, respectively. Mercury decreased kidney glutathione (GSH) and with LPS, it additively decreased GSH. Mercury activated p38 mitogen-activated protein kinase (MAPK) and additively increased LPS-induced p38 MAPK phosphorylation. In contrast, mercury inhibited LPS-induced activation of extra-cellular signal-regulated kinase (ERK) but had no effect alone. Mercury increased the gene expression of tumor necrosis factor $\alpha$ (TN F$\alpha$) and potentiated LPS-induced TNF$\alpha$ expression. Mercury did not affect LPS-induced interleukin-1$\beta$ (IL-1$\beta$) expression but decreased LPS-induced IL-6 expression. These results suggest that low levels of mercury might augment LPS-induced TNF$\alpha$ expression by altering GSH and p38 MAPK. Mercury modulates LPS-induced p38 and ERK activation, and downstream TNF$\alpha$ and IL-6 expression in kidney, respectively.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제33권3호
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• pp.211-220
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• 2007

Objective: In organotypic culture of immortalized human oral keratinocytes (IHOK), the change of the growth and differentiation was investigated according to the fibroblast type and the involvement of mitogen-activated protein (MAP) kinase. Materials & Methods: IHOK was cultured three dimensionally with gingival fibroblast (GF), dermal fibroblast (DF) and immortalized gingival fibroblast (IGF). We characterized biologic properties of three dimensionally reconstructed IHOK by histological, immunohistochemical, and Western blot analysis. We also investigated whether MAP kinase pathway was involved in epithelial-mesenchymal interaction by Western blot analysis. Results: The best condition of three dimensionally cultured IHOK was the dermal equivalent consisting of type I collagen and IGF. IGF increased the expression of more proliferating cell nuclear antigen (PCNA), involucrin than GF and DF in response to co-culture with IHOK. Extracellularly regulated kinase (ERK) pathway was activated in organotypic co-culture with IGF. Conclusion: The organotypic co-culture of IHOK with dermal equivalent consisting of type I collagen and IGF resulted in excellent morphologic and immunohistochemical characteristics and involved ERK pathway. The epithelial-mesenchymal interaction was activated according to the fibroblast type.

• BMB Reports
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• 제34권6호
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• pp.517-525
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• 2001

Six renaturable protein kinases that utilize the myelin basic protein (MBP) as a substrate were activated during prolonged exposure of cardiac myocytes to okadaic acid (OA). We characterized the substrate preference and activation of these kinases, with particular emphasis on 3 novel kinases-MBPK-55, MBPK-62 and MBPK-87. The transcription factors c-Jun, Elk, ATF2, and c-Fos that are used to assess mitogen-activated protein kinase activation were all poor substrates for these three kinases. MAPKAPK2 was also not phosphorylated. In contrast, Histone IIIS was phosphorylated by MBPK-55 and MBPK-62. These protein kinases were activated in cultured cardiac fibroblasts, H9c2 cardiac myoblasts, and Cos cells. High concentrations (0.5 to $1\;{\mu}M$) of OA were essential for the activation of the protein kinases in all of the cell types examined, whereas calyculin A [an inhibitor of protein phosphatase 1 (PP1) and PP2A], cyclosporin A (a PP2B inhibitor), and an inactive OA analog all failed to activate these kinases. The high dose of okadaic acid that is required for kinase activation was also required for phosphatase inhibition, as assessed by immunoblotting whole cell lysates with anti-phosphothreonine antibodies. A variety of chemical inhibitors, including PD98059 (MEK-specific), genistein (tyrosine kinase-specific) and Bisindolylmaleimide I (protein kinase C-specific), failed to inhibit the OA activation of these kinases. Thus, MBPK-55 and MBPK-62 are also Histone IIIS kinases that are widely expressed and specifically activated upon exposure to high OA concentrations.

• Journal of mucopolysaccharidosis and rare diseases
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• 제2권2호
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• pp.46-49
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• 2016

Achondroplasia is autosomal dominant genetic disease and fibroblast growth factor receptor 3 (FGFR3) is currently known to be the only gene that causes achondroplasia. Gain-of function mutation in fibroblast-growth-factor-receptor 3 (FGFR3) causes the disease and C-type natriuretic peptide (CNP) antagonizes FGFR3 downstream signaling by inhibiting the pathway of mitogen-activated protein kinase (MAPK). As FGFR3-related skeletal dysplasias are caused by growth attenuation of the cartilage, chondrocytes appear to be unique in their response to FGFR3 activation. However, the full spectrum of molecular events by which FGFR3 mediates its signaling is just beginning to emerge. This article summaries the mechanisms of FGFR3 function in skeletal dysplasias, the extraordinary cellular manifestations of FGFR3 signaling in chondrocytes, and finally, the progress toward therapy for ACH.

• 대한한의학회지
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• 제27권1호
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• pp.220-228
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• 2006

Objectives : Interleukin-1 (IL-1)${\beta}$ in articular chondrocytes regulates differentiation, apoptosis, and inflammatory responses. It is still controversial, So, we investigated IL- $1{\beta}$ induces chondrocytes dedifferentiation and death. Also, we studied the role of the mitogen-activated protein kinase (MAPK) subtypes on IL-$1{\beta}$-induced dedifferentiation and apoptosis. Methods : To evaluation of dedifferentiation by chemokines of chondrocytes, we assessed such as proteoglycan, collagen, MMP-3 and MMP-13 by RT-PCR analysis. Also, to assess of apoptosis effect by chemokines, we measured annexin V/propidium iodode (PI) and sub G1 cells in chondrocytes by flowcytometric analysis Results : IL-$1{\beta}$ treatment did not affect activation of ERK-1/2, but stimulation of p38 kinase. Inhibition of phospho ERK-1/2 with PD98059 enhanced IL-1b-induced dedifferentiation, and apoptosis up to 13.5%, whereas inhibition of phospho p38 kinase with SB203580 inhibited dedifferentiation, and apoptosis. Conclusions : Our results indicate that SB203580, p38 kinase inhibitor, inhibits IL-$1{\beta}$-induced dedifferentiation, and apoptosis by the inhibition of type II collagen expression and proteoglycan synthesis of rabbit articular chondrocytes.