Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.24 (mitogen-activated protein kinase)
 95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

TAK1 (transforming growth factor-beta-activated kinase-1), a MAP3K with considerable sequence similarity to Raf-1 and MEKK-1, has been identified as a transforming growth factor-beta/bone morphogenetic protein (BMP)-activated cytosolic component of the MAPK pathways. In this investigation, the molecular interactions between TAK1 and Smad proteins were characterized as well as their influence on BMP-mediated mesenchymal cell differentiation along the osteogenic/chondrogenic pathway. In co-immunoprecipitations we found an interaction of TAK1 with all Smads tested, R-Smads Smads1-5, the co-Smad Smad4, and the inhibitory Smads (I-Smad6 and I-Smad7). Smad interaction with TAK1 takes place through their MH2 domain. This interaction is dependent on the presence of an active kinase domain in TAK1. TAK1 dramatically interferes with R-Smad transactivation in reporter assays and affects subcellular distribution of Smad proteins. Activated TAK1 also interferes with BMP-dependent osteogenic development in murine mesenchymal progenitor cells (C3H10T 1/2). A potential TAK1-mediated apoptosis process could be excluded for these cells. Both synergistic and interfering influences of TAK1 on BMP-mediated Smad-signaling have been reported previously. We suggest that TAK1 is a factor that is involved in the fine-tuning of BMP effects during osteogenic development.
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PMID:Transforming growth factor-beta-activated kinase-1 (TAK1), a MAP3K, interacts with Smad proteins and interferes with osteogenesis in murine mesenchymal progenitors. 1591 26

The homeopathic compound of resonance FMS*Calciumfluor (FMS*) reportedly promotes osteogenic differentiation of rat pre-osteoblasts in vitro. Here, we show that the continuous exposure of differentiating rat osteogenic cells (ROB) to FMS* modulates the level of expression of mRNAs for 7 of the 8 osteogenic markers tested. Alkaline phosphatase (AP), osteocalcin (OC), metalloproteinases (MMP-2 and -14), procollagenase C (BMP-1), biglycan (BG) and integrin 1 are expressed at higher levels in FMS*-treated osteoblasts than in control cultures. MMP-2 and -14 mRNA are not down-modulated at mineralization. Also, the pattern of expression induced by FMS* for some of these genes (BMP-1, BG and integrin 1) is changed, but collagen type I (Coll I) mRNA levels are not affected by treatment with FMS*. This suggests that FMS* modulates mRNA levels and that this is not generalized, but gene(s) specific. We also report that exposure to FMS* rapidly and transiently induces activation of mitogen-activated protein kinases (MAPKs) 42,44 in populations of early osteoblasts, but not in pre-osteoblasts, with a cell differentiation stage-dependent and pertussis toxin (PTX)-sensitive response. Subsequent to FMS* MAPK signaling activation, an increase in AP and MMP-14 mRNA is detected, which is also inhibited by PTX, suggesting that FMS* activation of MAPK signaling could be an early event required for the induction of these genes. Exposure to FMS* does not cause changes in the activity of p125 (FAK)-mediated signaling.
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PMID:FMS*Calciumfluor specifically increases mRNA levels and induces signaling via MAPK 42,44 and not FAK in differentiating rat osteoblasts. 1602 62

In osteoblasts, the mitogen-activated protein kinases ERK1/2 and p38 as well as the cAMP-response element-binding protein (CREB) have been implicated in the regulation of proliferation and differentiation. The osteogenic growth peptide (OGP) is a 14-mer bone cell mitogen that increases bone formation and trabecular bone density and stimulates fracture healing. OGP-(10-14) is the physiologically active form of OGP. Using gene array analysis, real-time reverse transcription-PCR, and immunoblot and DNA synthesis assays we show here that in MC3T3 E1 and newborn mouse calvarial osteoblastic cultures the OGP-(10-14) mitogenic signaling is critically dependent on de novo synthesis of mitogen-activated protein kinase-activated protein kinase 2 (Mapkapk2) mRNA and protein. The increase in Mapkapk2 occurs following short term (5-60 min) stimulation of ERK1/2 activity by OGP-(10-14); phosphorylation of p38 remains unaffected. Downstream of Mapkapk2, CREB is phosphorylated on Ser(133) leading to its enhanced transcriptional activity. That these events are critical for the OGP-(10-14) mitogenic signaling is demonstrated by blocking the effects of OGP-(10-14) on the ERK1/2 pathway, Mapkapk2, CREB, and DNA synthesis using the MEK inhibitor PD098059. The OGP-(10-14) stimulation of CREB transcriptional activity and DNA synthesis is also blocked by Mapkapk2 siRNA. These data define a novel mitogenic signaling pathway in osteoblasts whereby ERK1/2 stimulation of CREB phosphorylation and transcriptional activity as well as DNA synthesis are critically dependent on de novo Mapkapk2 synthesis.
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PMID:ERK1/2-activated de novo Mapkapk2 synthesis is essential for osteogenic growth peptide mitogenic signaling in osteoblastic cells. 1615 Jul 1

Mechanical signals are important regulators of skeletal homeostasis, and strain-induced oscillatory fluid flow is a potent mechanical stimulus. Although the mechanisms by which osteoblasts and osteocytes respond to fluid flow are being elucidated, little is known about the mechanisms by which bone marrow-derived mesenchymal stem cells respond to such stimuli. Here we show that the intracellular signaling cascades activated in human mesenchymal stem cells by fluid flow are similar to those activated in osteoblastic cells. Oscillatory fluid flow inducing shear stresses of 5, 10, and 20 dyn/cm(2) triggered rapid, flow rate-dependent increases in intracellular calcium that pharmacological studies suggest are inositol trisphosphate mediated. The application of fluid flow also induced the phosphorylation of extracellular signal-regulated kinase-1 and -2 as well as the activation of the calcium-sensitive protein phosphatase calcineurin in mesenchymal stem cells. Activation of these signaling pathways combined to induce a robust increase in cellular proliferation. These data suggest that mechanically induced fluid flow regulates not only osteoblastic behavior but also that of mesenchymal precursors, implying that the observed osteogenic response to mechanical loading may be mediated by alterations in the cellular behavior of multiple members of the osteoblast lineage, perhaps by a common signaling pathway.
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PMID:MAP kinase and calcium signaling mediate fluid flow-induced human mesenchymal stem cell proliferation. 1626 9

Hepatocyte growth factor (HGF) is one of major growth factors in the bone marrow microenvironments with which the proliferation, differentiation and migration of bone marrow-derived mesenchymal stem cells were closely contacted. However, its roles in the regulation of proliferation, differentiation and migration of bone marrow-derived mesenchymal stem cells remain unclear. This study was aimed to investigate the effect of HGF on biological characteristics of bone marrow-derived mesenchymal stem cells. Expression of c-Met, the receptor for HGF was detected by immunohistochemistry assay, cell proliferation was determined by MTT, activity of ALP was quantitatively assayed, cell migration and anoikis-induced MSC apoptosis were analyzed. The results showed that HGF not influenced the proliferation and osteogenic differentiation of bone marrow-derived mesenchymal stem cells. Treatment of bone marrow-derived mesenchymal stem cells with recombinant human hepatocyte growth factor resulted in inhibition of anoikis-induced apoptosis. HGF significantly stimulated the migration of bone marrow-derived mesenchymal stem cells. Both PI-3 kinase and MAPK kinase were proved to be involved in HGF-induced migration. It is concluded that HGF/c-Met signal regulates the apoptosis and migration of bone marrow-derived mesenchymal stem cells.
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PMID:[Influence of hepatocyte growth factor on biological characteristics of bone marrow-derived mesenchymal stem cells]. 1640 77

Glucocorticoid hormones have complex stimulatory and inhibitory effects on skeletal metabolism. Endogenous glucocorticoid signaling is required for normal bone formation in vivo, and synthetic glucocorticoids, such as dexamethasone, promote osteoblastic differentiation in several in vitro model systems. The mechanism by which these hormones induce osteogenesis remains poorly understood. We demonstrate here that the coordinate action of dexamethasone and the osteogenic transcription factor Runx2/Cbfa1 synergistically induces osteocalcin and bone sialoprotein gene expression, alkaline phosphatase activity, and biological mineral deposition in primary dermal fibroblasts. Dexamethasone decreased Runx2 phosphoserine levels, particularly on Ser125, in parallel with the upregulation of mitogen-activated protein kinase (MAPK) phosphatase-1 (MKP-1) through a glucocorticoid-receptor-mediated mechanism. Inhibition of MKP-1 abrogated the dexamethasone-induced decrease in Runx2 serine phosphorylation, suggesting that glucocorticoids modulate Runx2 phosphorylation via MKP-1. Mutation of Ser125 to glutamic acid, mimicking constitutive phosphorylation, inhibited Runx2-mediated osteoblastic differentiation, which was not rescued by dexamethasone treatment. Conversely, mutation of Ser125 to glycine, mimicking constitutive dephosphorylation, markedly increased osteoblastic differentiation, which was enhanced by, but did not require, additional dexamethasone supplementation. Collectively, these results demonstrate that dexamethasone induces osteogenesis, at least in part, by modulating the phosphorylation state of a negative-regulatory serine residue (Ser125) on Runx2. This work identifies a novel mechanism for glucocorticoid-induced osteogenic differentiation and provides insights into the role of Runx2 phosphorylation during skeletal development.
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PMID:Glucocorticoid-induced osteogenesis is negatively regulated by Runx2/Cbfa1 serine phosphorylation. 1644 55

An association has been previously established between uncompensated diabetes mellitus and the loss of bone mineral density and/or quality. In this study, we evaluated the effects of metformin on the growth and differentiation of osteoblasts in culture. Treatment of two osteoblast-like cells (UMR106 and MC3T3E1) with metformin (25-500 microM) for 24 h led to a dose-dependent increase of cell proliferation. Metformin also promoted osteoblastic differentiation: it increased type-I collagen production in both cell lines and stimulated alkaline phosphatase activity in MC3T3E1 osteoblasts. In addition, metformin markedly increased the formation of nodules of mineralization in 3-week MC3T3E1 cultures. Metformin induced activation and redistribution of phosphorylated extracellular signal-regulated kinase (P-ERK) in a transient manner, and dose-dependently stimulated the expression of endothelial and inducible nitric oxide synthases (e/iNOS). These results show for the first time a direct osteogenic effect of metformin on osteoblasts in culture, which could be mediated by activation/redistribution of ERK-1/2 and induction of e/iNOS.
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PMID:Osteogenic actions of the anti-diabetic drug metformin on osteoblasts in culture. 1656 24

Protein kinase C (PKC) is a family of kinases whose isoforms show subtle differences in physiological and biochemical responses, with their expression being cell- specific. We hypothesize that there may be a specific profile of expression of PKC isoforms in differentiating osteoblastic cells (OBC) with individual isoforms having specific functions. Herein, the MC3T3-E1 cell line was used as a differentiating model, which was induced from the pre-osteoblast stage to mature osteoblast and characterized with several phenotypic markers, including alkaline phosphatase activity, osteocalcin and bone sialoprotein. The expression of PKC isoforms was monitored using Western blot analysis. Upon induction of osteogenesis, the intracellular localization of PKC eta and theta was determined using immunofluorescence. Lastly, the effect of P38 MAP kinase inhibition was determined using SB203580. Results show 1) PKC alpha, delta, lambda were all highly expressed in MC3T3-E1 osteoblastic cells, 2) the expression of PKC theta was significantly down-regulated upon induction of osteoblastic differentiation; 3) PKC eta was non-detectable at certain cell culture days; however, was up-regulated as the cells transit from each differentiation phase. The increased expression of PKC eta correlated with increases in OC, BSP levels and alkaline phosphatase activity. Immunofluorescence procedure confirmed the Western blot results with an increase in PKC eta and a decrease in PKC theta upon osteogenic stimulation. The inhibition of p38 resulted in a marked down-regulation of PKC eta. The data demonstrate that there is a specific profile of expression of PKC isoforms in differentiating osteoblasts; the different expression pattern of individual isoforms may be either a consequence of the differentiation itself or plays a role in the regulatory mechanism of osteoblastic differentiation. This study has provided primary information on the temporal pattern of expression of PKC isoforms in the differentiating osteoblast and further insight into their possible role in osteoblastic cell maturation.
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PMID:The expression profile of PKC isoforms during MC3T3-E1 differentiation. 1668 25

The roles of various soluble factors in promoting the osteogenic differentiation of adult mesenchymal stem cells (MSCs) have been widely studied, but little is known about how the extracellular matrix (ECM) instructs the phenotypic transition between growth and differentiation. To investigate this question, we cultured MSCs on purified vitronectin or type-I collagen, motivated by our earlier tissue engineering work demonstrating that MSC adhesion to polymer scaffolds is primarily mediated by the passive adsorption of these two ECM ligands from serum. Using alkaline phosphatase activity and matrix mineralization as indicators of the early and late stages of osteogenesis, respectively, we report here that both substrates supported differentiation, but the mechanism was substrate dependent. Specifically, osteogenesis on vitronectin correlated with enhanced focal adhesion formation, the activation of focal adhesion kinase (FAK) and paxillin, and the diminished activation of extracellular signal-regulated kinase (ERK) and phosphatidylinositol-3 kinase (PI3K) pathways. By contrast, MSCs on type-I collagen exhibited reduced focal adhesion formation, reduced activation of FAK and paxillin, and increased activation of ERK and PI3K. Inhibition of ERK and FAK blocked mineral deposition on both substrates, suggesting that the observed differences in signaling pathways ultimately converge to the same cell fate. Understanding these mechanistic differences is essential to predictably control the osteogenic differentiation of MSCs and widen their use in regenerative medicine.
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PMID:Vitronectin and collagen I differentially regulate osteogenesis in mesenchymal stem cells. 1681 99

Whereas continuous PTH infusion increases bone resorption and bone loss, intermittent PTH treatment stimulates bone formation, in part, via reactivation of quiescent bone surfaces and reducing osteoblast apoptosis. We investigated the possibility that intermittent and continuous PTH treatment also differentially regulates osteogenic and adipocytic lineage commitment of bone marrow stromal progenitor/mesenchymal stem cells (MSC). The MSC were cultured under mildly adipogenic conditions in medium supplemented with dexamethasone, insulin, isobutyl-methylxanthine and troglitazone (DIIT), and treated with 50 nM human PTH(1-34) for either 1 h/day or continuously (PTH replenished every 48 h). After 6 days, cells treated with PTH for 1 h/day retained their normal fibroblastic appearance whereas those treated continuously adopted a polygonal, irregular morphology. After 12-18 days numerous lipid vacuole and oil red O-positive adipocytes had developed in cultures treated with DIIT alone, or with DIIT and continuous PTH. In contrast, adipocyte number was reduced and alkaline phosphatase staining increased in the cultures treated with DIIT and 1 h/day PTH, indicating suppression of adipogenesis and possible promotion of early osteoblastic differentiation. Furthermore, intermittent but not continuous PTH treatment suppressed markers of differentiated adipocytes such as mRNA expression of lipoprotein lipase and PPARgamma as well as glycerol 3-phosphate dehydrogenase activity. All of these effects of intermittent PTH were also produced by a 1 h/day treatment with AH3960 (30 microM), a small molecule, non-peptide agonist of the PTH1 receptor. AH3960, like PTH, activates both the cAMP and calcium signaling pathways. Treatment with the adenylyl cyclase activator forskolin for 1 h/day, mimicked the anti-adipogenic effect of intermittent PTH, whereas pretreatment with the protein kinase-A inhibitor H89 prior to intermittent PTH resulted in almost complete conversion to adipocytes. In contrast, the MAP kinase inhibitor PD 98059 failed to prevent the anti-adipocytic effect of intermittent PTH, suggesting that the inhibitory effect of PTH on adipocyte differentiation is predominantly cAMP-dependent. These results demonstrate a differential effect of PTH1 receptor agonists on the adipocytic commitment and differentiation of adult human bone marrow mesenchymal stem cells. This response may represent an additional mechanism that contributes to the overall bone anabolic action of intermittent PTH.
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PMID:Intermittent treatment with parathyroid hormone (PTH) as well as a non-peptide small molecule agonist of the PTH1 receptor inhibits adipocyte differentiation in human bone marrow stromal cells. 1690 89


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