scholarly journals Critical role of the extracellular signal–regulated kinase–MAPK pathway in osteoblast differentiation and skeletal development

2007 ◽  
Vol 176 (5) ◽  
pp. 709-718 ◽  
Author(s):  
Chunxi Ge ◽  
Guozhi Xiao ◽  
Di Jiang ◽  
Renny T. Franceschi
Keyword(s):  
Transcriptional Activity ◽  
Mapk Pathway ◽  
Skeletal Development ◽  
Critical Role ◽  
Dominant Negative ◽  
Mitogen Activated Protein Kinase ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal

The extracellular signal–regulated kinase (ERK)–mitogen-activated protein kinase (MAPK) pathway provides a major link between the cell surface and nucleus to control proliferation and differentiation. However, its in vivo role in skeletal development is unknown. A transgenic approach was used to establish a role for this pathway in bone. MAPK stimulation achieved by selective expression of constitutively active MAPK/ERK1 (MEK-SP) in osteoblasts accelerated in vitro differentiation of calvarial cells, as well as in vivo bone development, whereas dominant-negative MEK1 was inhibitory. The involvement of the RUNX2 transcription factor in this response was established in two ways: (a) RUNX2 phosphorylation and transcriptional activity were elevated in calvarial osteoblasts from TgMek-sp mice and reduced in cells from TgMek-dn mice, and (b) crossing TgMek-sp mice with Runx2+/− animals partially rescued the hypomorphic clavicles and undemineralized calvaria associated with Runx2 haploinsufficiency, whereas TgMek-dn; Runx2+/− mice had a more severe skeletal phenotype. This work establishes an important in vivo function for the ERK–MAPK pathway in bone that involves stimulation of RUNX2 phosphorylation and transcriptional activity.

scholarly journals Nck-dependent Activation of Extracellular Signal-regulated Kinase-1 and Regulation of Cell Survival during Endoplasmic Reticulum Stress

2004 ◽  
Vol 15 (9) ◽  
pp. 4248-4260 ◽  
Author(s):  
Duc Thang Nguyên ◽  
Sem Kebache ◽  
Ali Fazel ◽  
Hetty N. Wong ◽  
Sarah Jenna ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Kinase ◽  
Er Stress ◽  
Cell Survival ◽  
Mapk Pathway ◽  
Critical Role ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal

In response to stress, the endoplasmic reticulum (ER) signaling machinery triggers the inhibition of protein synthesis and up-regulation of genes whose products are involved in protein folding, cell cycle exit, and/or apoptosis. We demonstrate that the misfolding agents azetidine-2-carboxylic acid (Azc) and tunicamycin initiate signaling from the ER, resulting in the activation of Jun-N-terminal kinase, p44MAPK/extracellular signal-regulated kinase-1 (ERK-1), and p38MAPK through IRE1α-dependent mechanisms. To characterize the ER proximal signaling events involved, immuno-isolated ER membranes from rat fibroblasts treated with ER stress inducers were used to reconstitute the activation of the stress-activated protein kinase/mitogen-activate protein kinase (MAPK) pathways in vitro. This allowed us to demonstrate a role for the SH2/SH3 domain containing adaptor Nck in ERK-1 activation after Azc treatment. We also show both in vitro and in vivo that under basal conditions ER-associated Nck represses ERK-1 activation and that upon ER stress this pool of Nck dissociates from the ER membrane to allow ERK-1 activation. Moreover, under the same conditions, Nck-null cells elicit a stronger ERK-1 activation in response to Azc stress, thus, correlating with an enhanced survival phenotype. These data delineate a novel mechanism for the regulation of ER stress signaling to the MAPK pathway and demonstrate a critical role for Nck in ER stress and cell survival.

scholarly journals Identification of Novel In Vivo Raf-1 Phosphorylation Sites Mediating Positive Feedback Raf-1 Regulation by Extracellular Signal-regulated Kinase

2006 ◽  
Vol 17 (3) ◽  
pp. 1141-1153 ◽  
Author(s):  
Vitaly Balan ◽  
Deborah T. Leicht ◽  
Jun Zhu ◽  
Karina Balan ◽  
Alexander Kaplun ◽  
...  
Keyword(s):  
Positive Feedback ◽  
Critical Role ◽  
Mitogen Activated Protein Kinase ◽  
Phosphorylation Sites ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal ◽  
Mitogen Activated Protein ◽  
Phosphopeptide Mapping

The Ras–Raf–mitogen-activated protein kinase cascade is a key growth-signaling pathway, which uncontrolled activation results in transformation. Although the exact mechanisms underlying Raf-1 regulation remain incompletely understood, phosphorylation has been proposed to play a critical role in this regulation. We report here three novel epidermal growth factor-induced in vivo Raf-1 phosphorylation sites that mediate positive feedback Raf-1 regulation. Using mass spectrometry, we identified Raf-1 phosphorylation on three SP motif sites: S289/S296/S301 and confirmed their identity using two-dimensional-phosphopeptide mapping and phosphospecific antibodies. These sites were phosphorylated by extracellular signal-regulated kinase (ERK)-1 in vitro, and their phosphorylation in vivo was dependent on endogenous ERK activity. Functionally, ERK-1 expression sustains Raf-1 activation in a manner dependent on Raf-1 phosphorylation on the identified sites, and S289/296/301A substitution markedly decreases the in vivo activity of Raf-1 S259A. Importantly, the ERK-phosphorylated Raf-1 pool has 4 times higher specific kinase activity than total Raf-1, and its phosphopeptide composition is similar to that of the general Raf-1 population, suggesting that the preexisting, phosphorylated Raf-1, representing the activatable Raf-1 pool, is the Raf-1 subpopulation targeted by ERK. Our study describes the identification of new in vivo Raf-1 phosphorylation sites targeted by ERK and provides a novel mechanism for a positive feedback Raf-1 regulation.

scholarly journals Extracellular Signal-Regulated Kinase 1 Interacts with and Phosphorylates CdGAP at an Important Regulatory Site

2005 ◽  
Vol 25 (15) ◽  
pp. 6314-6329 ◽  
Author(s):  
Joseph Tcherkezian ◽  
Eric I. Danek ◽  
Sarah Jenna ◽  
Ibtissem Triki ◽  
Nathalie Lamarche-Vane
Keyword(s):  
Bound States ◽  
Mitogen Activated Protein Kinase ◽  
Regulatory Site ◽  
Nucleotide Exchange ◽  
Rich Region ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal ◽  
Proline Rich Region

ABSTRACT Rho GTPases regulate multiple cellular processes affecting both cell proliferation and cytoskeletal dynamics. Their cycling between inactive GDP- and active GTP-bound states is tightly regulated by guanine nucleotide exchange factors and GTPase-activating proteins (GAPs). We have previously identified CdGAP (for Cdc42 GTPase-activating protein) as a specific GAP for Rac1 and Cdc42. CdGAP consists of an N-terminal RhoGAP domain and a C-terminal proline-rich region. In addition, CdGAP is a member of the impressively large number of mammalian RhoGAP proteins that is well conserved among both vertebrates and invertebrates. In mice, we find two predominant isoforms of CdGAP differentially expressed in specific tissues. We report here that CdGAP is highly phosphorylated in vivo on serine and threonine residues. We find that CdGAP is phosphorylated downstream of the MEK-extracellular signal-regulated kinase (ERK) pathway in response to serum or platelet-derived growth factor stimulation. Furthermore, CdGAP interacts with and is phosphorylated by ERK-1 and RSK-1 in vitro. A putative DEF (docking for ERK FXFP) domain located in the proline-rich region of CdGAP is required for efficient binding and phosphorylation by ERK1/2. We identify Thr776 as an in vivo target site of ERK1/2 and as an important regulatory site of CdGAP activity. Together, these data suggest that CdGAP is a novel substrate of ERK1/2 and mediates cross talk between the Ras/mitogen-activated protein kinase pathway and regulation of Rac1 activity.

Delivery of Sorafenib and Metformin Against Hepatocellular Carcinoma with Amphiphilic Polypeptide-based Micelles

2021 ◽  
Author(s):  
Lanqing Cao ◽  
Guangmeng Xu ◽  
Hongyu He ◽  
Jiannan Li
Keyword(s):  
Mapk Pathway ◽  
Synergistic Effects ◽  
Mitogen Activated Protein Kinase ◽  
High Recurrence Rate ◽  
Extracellular Signal Regulated Kinase ◽  
Cycle Arrest ◽  
Extracellular Signal ◽  
Mitogen Activated Protein ◽  
Poly Ethylene

Abstract Hepatoma is a common clinical disease with poor prognosis and a high recurrence rate. Chemotherapy is important for hepatoma treatment because only a small amount of hepatoma patients are suitable for local resection, and the effects of transarterial chemoembolization (TACE) are unsatisfactory. But many limitations restrict further application of chemotherapy. In this study, sorafenib (Sor) and metformin (Met) co-loaded poly(ethylene glycol)-block-poly(L-glutamic acid-co-L-phenylalanine) (mPEG-b-P(Glu-co-Phe)) micelles were developed. Sor is a common molecular target agent which can inhibit the mitogen-activated protein kinase (MAPK) pathway to treat hepatoma clinically. Met can also regulate the MAPK pathway and inhibit the expression of the phosphorylated extracellular signal-regulated kinase (p-ERK). Moreover, both Sor and Met play important roles in cell cycle arrest. The integration of these two drugs aims to achieve synergistic effects against hepatoma. The micelles can be targeted to cancer cells and possess longer blood circulation time. The two agents can be released rapidly in the tumor sites. Both orthotopic and patient-derived xenograft (PDX) hepatoma models were developed to analyze the treatment efficacy of the Sor and Met loaded micelles. The in vivo study showed that the micelles can prevent hepatoma progression by inhibiting the expressions of p-ERK and cyclin D1. This study indicated that the Sor/Met-loaded micelles are suitable for hepatoma treatment.

scholarly journals Signal Pathways Which Promote Invasion and Metastasis: Critical and Distinct Contributions of Extracellular Signal-Regulated Kinase and Ral-Specific Guanine Exchange Factor Pathways

2001 ◽  
Vol 21 (17) ◽  
pp. 5958-5969 ◽  
Author(s):  
Yvona Ward ◽  
Warner Wang ◽  
Elisa Woodhouse ◽  
Ilona Linnoila ◽  
Lance Liotta ◽  
...  
Keyword(s):  
Dominant Negative ◽  
Signal Pathways ◽  
Nucleotide Exchange ◽  
3T3 Cells ◽  
Invasion And Metastasis ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal ◽  
Erk Activity

ABSTRACT Approximately 50% of metastatic tumors contain Ras mutations. Ras proteins can activate at least three downstream signaling cascades mediated by the Raf–MEK–extracellular signal-regulated kinase family, phosphatidylinositol-3 (PI3) kinase, and Ral-specific guanine nucleotide exchange factors (RalGEFs). Here we investigated the contribution of RalGEF and ERK activation to the development of experimental metastasis in vivo and associated invasive properties in vitro. Each pathway contributes distinct properties to the metastatic phenotype. Following lateral tail vein injection, 3T3 cells transformed by constitutively active Raf or MEK produced lung metastasis that displayed circumscribed, noninfiltrating borders. In contrast, 3T3 cells transformed by Ras(12V,37G), a Ras effector mutant that activates RalGEF but not Raf or P13 kinase, formed aggressive, infiltrative metastasis. Dominant negative RalB inhibited Ras(12V,37G)-activated invasion and metastasis, demonstrating the necessity of the RalGEF pathway for a fully transformed phenotype. Moreover, 3T3 cells constitutively expressing a membrane-associated form of RalGEF (RalGDS-CAAX) formed invasive tumors as well, demonstrating that activation of a RalGEF pathway is sufficient to initiate the invasive phenotype. Despite the fact that Ras(12V,37G) expression does not elevate ERK activity, inhibition of this kinase by a conditionally expressed ERK phosphatase demonstrated that ERK activity was necessary for Ras(12V,37G)-transformed cells to express matrix-degrading activity in vitro and tissue invasiveness in vivo. Therefore, these experiments have revealed a hitherto-unknown but essential interaction of the RalGEF and ERK pathways to produce a malignant phenotype. The generality of the role of the RalGEF pathway in metastasis is supported by the finding that Ras(12V,37G) increased the invasiveness of epithelial cells as well as fibroblasts.

scholarly journals TGFβ induces GDNF responsiveness in neurons by recruitment of GFRα1 to the plasma membrane

2002 ◽  
Vol 159 (1) ◽  
pp. 157-167 ◽  
Author(s):  
H. Peterziel ◽  
K. Unsicker ◽  
K. Krieglstein
Keyword(s):  
Plasma Membrane ◽  
Transforming Growth Factor ◽  
Mapk Pathway ◽  
Cooperative Effect ◽  
Primary Neurons ◽  
Glycosyl Phosphatidylinositol ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal

We have previously shown that the neurotrophic effect of glial cell line–derived neurotrophic factor (GDNF) in vitro and in vivo requires the presence of transforming growth factor (TGF)β. Using primary neurons (chick E8 ciliary) we show that the combination of GDNF plus TGFβ promotes survival, whereas the single factors do not. This cooperative effect is inhibited by blocking the extracellular signal-regulated kinase (ERK)/MAPK pathway, but not by interfering with the PI3 kinase signaling cascade. Although there is no functional GDNF signaling in the absence of TGFβ, pretreatment with TGFβ confers GDNF responsiveness to the cells. This is not due to upregulation of GDNF receptors mRNA and protein, but to TGFβ-induced recruitment of the glycosyl-phosphatidylinositol-anchored GDNF receptor (GFR)α1 to the plasma membrane. This is supported by the fact that GDNF in the presence of a soluble GFRα1 can promote survival in the absence of TGFβ. Our data suggest that TGFβ is involved in GFRα1 membrane translocation, thereby permitting GDNF signaling and neurotrophic effects.

Sign in / Sign up

Export Citation Format

Share Document