Signalling Pathways Involved in the Mitogenic Effects of cAMP

1997 ◽  
Vol 92 (5) ◽  
pp. 445-451 ◽  
Author(s):  
D. J. Withers
Keyword(s):  
Dna Synthesis ◽  
Mapk Pathway ◽  
Critical Role ◽  
Cell Types ◽  
Mapk Cascade ◽  
Mitogen Activated Protein Kinase ◽  
Signalling Pathways ◽  
3T3 Cells ◽  
Mitogen Activated Protein ◽  
Swiss 3T3

1. Elevation of intracellular cyclic AMP (cAMP) is a potent mitogenic signal for a number of cell types, including Swiss 3T3 cells, thyroid epithelial cells and the somatotroph cells of the anterior pituitary. 2. Activation of the mitogen-activated protein kinase (MAPK) cascade has been shown to underlie the mitogenic effects of many growth factors. However, the precise relationship between the mitogenic effects of cAMP and the MAPK cascade is not fully defined. 3. In Swiss 3T3 cells, elevation of cAMP did not stimulate kinases at all three levels of the MAPK cascade. Additionally, blockade of the MAPK pathway failed to inhibit cAMP-stimulated DNA synthesis. 4. Mitogenic combinations of cAMP strongly stimulated the phosphorylation and activation of the serine/threonine kinase p70 S6 kinase, p70S6K, an effect that was inhibited by rapamycin. This agent markedly inhibited cAMP-stimulated DNA synthesis, suggesting a critical role for p70S6K in cAMP mitogenic signalling. 5. Thus, multiple parallel but distinct signalling pathways may be involved in the action of mitogens. This redundancy has important implications for the pathogenesis and treatment of conditions characterized by inappropriate activation of growth factor signalling pathways.

scholarly journals Dissociation of mitogen-activated protein kinase activation from p125 focal adhesion kinase tyrosine phosphorylation in Swiss 3T3 cells stimulated by bombesin, lysophosphatidic acid, and platelet-derived growth factor.

1996 ◽  
Vol 7 (12) ◽  
pp. 1865-1875 ◽  
Author(s):  
T Seufferlein ◽  
D J Withers ◽  
D Mann ◽  
E Rozengurt
Keyword(s):  
Protein Kinase ◽  
Tyrosine Phosphorylation ◽  
Focal Adhesion ◽  
Lysophosphatidic Acid ◽  
Mitogen Activated Protein Kinase ◽  
Platelet Derived Growth Factor ◽  
3T3 Cells ◽  
Kinase C ◽  
Mitogen Activated Protein ◽  
Swiss 3T3

The experiments presented here were designed to examine the contribution of p125 focal adhesion kinase (p125FAK) tyrosine phosphorylation to the activation of the mitogen-activated protein kinase cascade induced by bombesin, lysophosphatidic acid (LPA), and platelet-derived growth factor (PDGF) in Swiss 3T3 cells. We found that tyrosine phosphorylation of p125FAK in response to these growth factors is completely abolished in cells treated with cytochalasin D or in cells that were suspended in serum-free medium for 30 min. In marked contrast, the activation of p42mapk by these factors was independent of the integrity of the actin cytoskeleton and of the interaction of the cells with the extracellular matrix. The protein kinase C inhibitor GF 109203X and down-regulation of protein kinase C by prolonged pretreatment of cells with phorbol esters blocked bombesin-stimulated activation of p42mapk, p90rsk, and MAPK kinase-1 but did not prevent bombesin-induced tyrosine phosphorylation of p125FAK. Furthermore, LPA-induced p42mapk activation involved a pertussis toxin-sensitive guanylate nucleotide-binding protein, whereas tyrosine phosphorylation of p125FAK in response to LPA was not prevented by pretreatment with pertussis toxin. Finally, PDGF induced maximum p42mapk activation at concentrations (30 ng/ml) that failed to induce tyrosine phosphorylation of p125FAK. Thus, our results demonstrate that p42mapk activation in response to bombesin, LPA, and PDGF can be dissociated from p125FAK tyrosine phosphorylation in Swiss 3T3 cells.

scholarly journals Positive and negative selection invoke distinct signaling pathways.

1996 ◽  
Vol 184 (1) ◽  
pp. 9-18 ◽  
Author(s):  
J Alberola-Ila ◽  
K A Hogquist ◽  
K A Swan ◽  
M J Bevan ◽  
R M Perlmutter
Keyword(s):  
T Cell ◽  
Positive Selection ◽  
Negative Selection ◽  
Mapk Pathway ◽  
Cell Receptor ◽  
Dominant Negative ◽  
Mapk Cascade ◽  
Mitogen Activated Protein Kinase ◽  
Mitogen Activated Protein

During T cell development, interaction of the T cell receptor (TCR) with cognate ligands in the thymus may result in either maturation (positive selection) or death (negative selection). The intracellular pathways that control these opposed outcomes are not well characterized. We have generated mice expressing dominant-negative Ras (dnRas) and Mek-1 (dMek) transgenes simultaneously, either in otherwise normal animals, or in animals expressing a transgenic TCR, thereby permitting a comprehensive analysis of peptide-specific selection. In this system, thymocyte maturation beyond the CD4+8+ stage is blocked almost completely, whereas negative selection, assessed using an in vitro deletion protocol, is quantitatively intact. This suggests that activation of the mitogen-activated protein kinase (MAPK) cascade is necessary for positive selection, but irrelevant for negative selection. Generation of gamma/delta and of CD4-8- alpha/beta T cells proceeds normally despite blockade of the MAPK cascade. Hence, only cells that mature via conventional, TCR-mediated repertoire selection require activation of the MAPK pathway to complete their maturation.

Manipulation of host signalling pathways by anthrax toxins

2007 ◽  
Vol 402 (3) ◽  
pp. 405-417 ◽  
Author(s):  
Benjamin E. Turk
Keyword(s):  
Protein Kinase ◽  
Pathogenic Bacteria ◽  
Protective Antigen ◽  
Lethal Factor ◽  
Cell Types ◽  
Host Cells ◽  
Mitogen Activated Protein Kinase ◽  
Signalling Pathways ◽  
Common Strategy ◽  
Mitogen Activated Protein

Infectious microbes face an unwelcoming environment in their mammalian hosts, which have evolved elaborate multicelluar systems for recognition and elimination of invading pathogens. A common strategy used by pathogenic bacteria to establish infection is to secrete protein factors that block intracellular signalling pathways essential for host defence. Some of these proteins also act as toxins, directly causing pathology associated with disease. Bacillus anthracis, the bacterium that causes anthrax, secretes two plasmid-encoded enzymes, LF (lethal factor) and EF (oedema factor), that are delivered into host cells by a third bacterial protein, PA (protective antigen). The two toxins act on a variety of cell types, disabling the immune system and inevitably killing the host. LF is an extraordinarily selective metalloproteinase that site-specifically cleaves MKKs (mitogen-activated protein kinase kinases). Cleavage of MKKs by LF prevents them from activating their downstream MAPK (mitogen-activated protein kinase) substrates by disrupting a critical docking interaction. Blockade of MAPK signalling functionally impairs cells of both the innate and adaptive immune systems and induces cell death in macrophages. EF is an adenylate cyclase that is activated by calmodulin through a non-canonical mechanism. EF causes sustained and potent activation of host cAMP-dependent signalling pathways, which disables phagocytes. Here I review recent progress in elucidating the mechanisms by which LF and EF influence host signalling and thereby contribute to disease.

scholarly journals Distinct signalling pathways mediate the cAMP response element (CRE)-dependent activation of the calcitonin gene-related peptide gene promoter by cAMP and nerve growth factor

2000 ◽  
Vol 345 (2) ◽  
pp. 233-238 ◽  
Author(s):  
Karen FREELAND ◽  
Yu-Zhen LIU ◽  
David S. LATCHMAN
Keyword(s):  
Nerve Growth Factor ◽  
Growth Factor ◽  
Protein Kinase ◽  
Mapk Pathway ◽  
Mitogen Activated Protein Kinase ◽  
Signalling Pathways ◽  
Camp Response Element ◽  
Response Element ◽  
Calcitonin Gene ◽  
Mitogen Activated Protein

The gene encoding the calcitonin gene-related peptide (CGRP) is activated in neuronal cells by treatment with cAMP and nerve growth factor (NGF). Both stimuli induce the phosphorylation of the cAMP response element (CRE)-binding protein (CREB) transcription factor on Ser-133 and require the CRE in the CGRP promoter to stimulate transcription. However, whereas the CRE is necessary and sufficient for promoter activation by cAMP, it is necessary but not sufficient for activation by NGF. We show that this difference is paralleled by a difference in the signalling pathways which are required for each stimulus to activate the CGRP promoter. Thus whilst cAMP-mediated activation requires the protein kinase A pathway, NGF-mediated stimulation requires the Ras/Raf mitogen-activated protein kinase kinase-1 (MEK-1)/p42/p44 mitogen-activated protein kinase (MAPK) pathway. Although NGF can activate the protein kinase C, p38 MAPK and c-Jun N-terminal kinase (JNK) pathways, these pathways are not involved in its effect on the CGRP promoter. The effect of the p42/p44 MAPK pathway on CREB and associated transcription factors, and the manner in which this results in activation of the CGRP promoter is discussed.

scholarly journals Prolonged activation of the mitogen-activated protein kinase pathway promotes DNA synthesis in primary hepatocytes from p21Cip-1/WAF1-null mice, but not in hepatocytes from p16INK4a-null mice

1998 ◽  
Vol 336 (3) ◽  
pp. 551-560 ◽  
Author(s):  
Kelly L. AUER ◽  
Jong-Sung PARK ◽  
Prem SETH ◽  
Robert J. COFFEY ◽  
Gretchen DARLINGTON ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Dna Synthesis ◽  
Mapk Pathway ◽  
Mitogen Activated Protein Kinase ◽  
Cyclin Dependent Kinase ◽  
Wild Type ◽  
Primary Hepatocytes ◽  
Rhoa Gtpase ◽  
Mapk Signalling ◽  
Mitogen Activated Protein

In primary rat hepatocytes, prolonged activation of the p42/44 mitogen-activated protein kinase (MAPK) pathway is associated with a decrease in DNA synthesis and increased expression of the cyclin-dependent kinase inhibitor (CKI) proteins p21Cip-1/WAF1 and p16INK4a. To evaluate the relative importance of these CKIs in mediating this response, we determined the impact of prolonged MAPK activation on DNA synthesis in primary cultures of hepatocytes derived from mice embryonically deleted (null) for either p21Cip-1/WAF1 or p16INK4a. When MAPK was activated in wild-type mouse hepatocytes for 24 h, via infection with a construct to express an inducible oestrogen receptor–Raf-1 fusion protein (ΔRaf:ER), the expression of p21Cip-1/WAF1 and p16INK4a CKI proteins increased, cyclin-dependent kinase 2 (cdk2) and cdk4 activities decreased, and DNA synthesis decreased. Inhibition of RhoA GTPase function increased the basal expression of p21Cip-1/WAF1 and p27Kip-1 but not p16INK4a, and enhanced the ability of MAPK signalling to decrease DNA synthesis. Ablation of the expression of CCAATT enhancer-binding protein α (C/EBPα), but not of the expression of C/EBPβ, decreased the ability of MAPK signalling to induce p21Cip-1/WAF1. When MAPK was activated in p16INK4a-null hepatocytes for 24 h, the expression of p21Cip-1/WAF1 increased, cdk2 and cdk4 activities decreased and DNA synthesis decreased. In contrast with these findings, prolonged activation of the MAPK pathway in hepatocytes from p21Cip-1/WAF1-null mice enhanced cdk2 and cdk4 activities and caused a large increase in DNA synthesis, despite elevated expression of p16INK4a. Inhibition of RhoA GTPase activity in p21Cip-1/WAF1-null cells partly blunted both the basal levels of DNA synthesis and the ability of prolonged MAPK signalling to increase DNA synthesis. Expression of anti-sense p21Cip-1/WAF1 in either wild-type or p16INK4a-null hepatocytes decreased the ability of prolonged MAPK signalling to increase the expression of p21Cip-1/WAF1, and permitted MAPK signalling to increase both cdk2 and cdk4 activities and DNA synthesis. These results argue that the ability of prolonged MAPK signalling to inhibit DNA synthesis in hepatocytes requires the expression of p21Cip-1/WAF1, and that the increased expression of p16INK4a has a smaller role in the ability of this stimulus to mediate growth arrest. Our results also suggest that RhoA function can modulate DNA synthesis in primary hepatocytes via the expression of p21Cip-1/WAF1 and p27Kip-1.

scholarly journals Bombesin stimulates cholecystokinin secretion through mitogen-activated protein-kinase-dependent and -independent mechanisms in the enteroendocrine STC-1 cell line

1998 ◽  
Vol 331 (1) ◽  
pp. 129-135 ◽  
Author(s):  
Eric NÉMOZ-GAILLARD ◽  
Martine CORDIER-BUSSAT ◽  
Chantal FILLOUX ◽  
Jean-Claude CUBER ◽  
Emmanuel VAN OBBERGHEN ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Cell Line ◽  
Mapk Pathway ◽  
Late Phase ◽  
Cell Types ◽  
Mitogen Activated Protein Kinase ◽  
Pancreatic Acinar Cells ◽  
Prolonged Treatment ◽  
3T3 Fibroblasts ◽  
Mitogen Activated Protein

Bombesin has been reported to stimulate cholecystokinin (CCK) secretion from rat duodeno-jejunal I-cells. Bombesin was shown to activate mitogen-activated protein kinases (MAPKs) in cell types such as Swiss 3T3 fibroblasts and rat pancreatic acinar cells. No information is available on whether MAPK is activated in intestinal endocrine cells upon bombesin stimulation. This was studied by using the CCK-producing enteroendocrine cell line STC-1. Bombesin stimulated markedly and transiently both p42MAPK and p44MAPK, with a maximum at 2 min, and a decrease to basal levels within 10 min. As expected, bombesin stimulated MAPK kinase 1 (MEK-1) activity. Activation of protein kinase C (PKC) with PMA also stimulated p42MAPK, p44MAPK and MEK-1. Treatment of cells with PD 098059 (at 10 µM or 30 µM), which selectively inhibits MEK phosphorylation, blocked bombesin-induced p42MAPK and p44MAPK activation for at least 90 min. However, PD 098059 inhibited bombesin- and PMA-stimulated CCK secretion during the first 15 min, but failed to significantly reduce CCK release at later times. Inhibition of PKC with staurosporine, or PKC down-regulation by prolonged treatment with PMA, both drastically decreased MEK-1, p42MAPK and p44MAPK activation upon bombesin stimulation. Additionally, PKC activation appeared to be required for both MAPK-dependent (early) and -independent (late) CCK responses to bombesin. It is concluded that the early CCK secretory response of STC-1 cells to bombesin involves MAPK pathway activation through a PKC-dependent mechanism, whereas the late phase of bombesin-induced CCK secretion, that also requires PKC, appears to result from a MAPK-independent process.

scholarly journals The Mitogen-Activated Protein Kinase Signal-Integrating Kinase Mnk2 Is a Eukaryotic Initiation Factor 4E Kinase with High Levels of Basal Activity in Mammalian Cells

2001 ◽  
Vol 21 (3) ◽  
pp. 743-754 ◽  
Author(s):  
Gert C. Scheper ◽  
Nick A. Morrice ◽  
Miranda Kleijn ◽  
Christopher G. Proud
Keyword(s):  
Protein Kinase ◽  
Mitogen Activated Protein Kinase ◽  
Initiation Factor ◽  
Eukaryotic Initiation Factor ◽  
3T3 Cells ◽  
Mapk Pathways ◽  
Eukaryotic Initiation Factor 4E ◽  
Mitogen Activated Protein ◽  
Swiss 3T3

ABSTRACT The cap-binding translation initiation factor eukaryotic initiation factor 4E (eIF4E) is phosphorylated in vivo at Ser209 in response to a variety of stimuli. In this paper, we show that the mitogen-activated protein kinase (MAPK) signal-integrating kinase Mnk2 phosphorylates eIF4E at this residue. Mnk2 binds to the scaffolding protein eIF4G, and overexpression of Mnk2 results in increased phosphorylation of endogenous eIF4E, showing that it can act as an eIF4E kinase in vivo. We have identified eight phosphorylation sites in Mnk2, of which at least three potential MAPK sites are likely to be essential for Mnk2 activity. In contrast to that of Mnk1, the activity of overexpressed Mnk2 is high under control conditions and could only be reduced substantially by a combination of PD98059 and SB203580, while the activity of endogenous Mnk2 in Swiss 3T3 cells was hardly affected upon treatment with these inhibitors. These compounds did not abolish phosphorylation of eIF4E, implying that Mnk2 may mediate phosphorylation of eIF4E in Swiss 3T3 cells. In vitro phosphorylation studies show that Mnk2 is a significantly better substrate than Mnk1 for extracellular signal-regulated kinase 2 (ERK2), p38MAPKα, and p38MAPKβ. Therefore, the high levels of activity of Mnk2 under several conditions may be explained by efficient activation of Mnk2 by low levels of activity of the upstream kinases. Interestingly, we found that the association of both Mnk1 and Mnk2 with eIF4G increased upon inhibition of the MAPK pathways while activation of ERK resulted in decreased binding to eIF4G. This might reflect a mechanism to ensure rapid, but transient, phosphorylation of eIF4E upon stimulation of the MAPK pathways.

scholarly journals Chromatin remodeling by the SWI/SNF complex is essential for transcription mediated by the yeast cell wall integrity MAPK pathway

2012 ◽  
Vol 23 (14) ◽  
pp. 2805-2817 ◽  
Author(s):  
A. Belén Sanz ◽  
Raúl García ◽  
Jose Manuel Rodríguez-Peña ◽  
Sonia Díez-Muñiz ◽  
César Nombela ◽  
...  
Keyword(s):  
Cell Wall ◽  
Chromatin Remodeling ◽  
Mapk Pathway ◽  
Critical Role ◽  
Transcriptional Response ◽  
Wall Stress ◽  
Cell Wall Integrity ◽  
Mitogen Activated Protein Kinase ◽  
Cell Wall Stress ◽  
Mitogen Activated Protein

In Saccharomyces cerevisiae, the transcriptional program triggered by cell wall stress is coordinated by Slt2/Mpk1, the mitogen-activated protein kinase (MAPK) of the cell wall integrity (CWI) pathway, and is mostly mediated by the transcription factor Rlm1. Here we show that the SWI/SNF chromatin-remodeling complex plays a critical role in orchestrating the transcriptional response regulated by Rlm1. swi/snf mutants show drastically reduced expression of cell wall stress–responsive genes and hypersensitivity to cell wall–interfering compounds. On stress, binding of RNA Pol II to the promoters of these genes depends on Rlm1, Slt2, and SWI/SNF. Rlm1 physically interacts with SWI/SNF to direct its association to target promoters. Finally, we observe nucleosome displacement at the CWI-responsive gene MLP1/KDX1, which relies on the SWI/SNF complex. Taken together, our results identify the SWI/SNF complex as a key element of the CWI MAPK pathway that mediates the chromatin remodeling necessary for adequate transcriptional response to cell wall stress.

Thrombopoietin-Induced Activation of the Mitogen-Activated Protein Kinase (MAPK) Pathway in Normal Megakaryocytes: Role in Endomitosis

Blood ◽  
1999 ◽  
Vol 94 (4) ◽  
pp. 1273-1282 ◽  
Author(s):  
Ponlapat Rojnuckarin ◽  
Jonathan G. Drachman ◽  
Kenneth Kaushansky
Keyword(s):  
Protein Kinase ◽  
Mapk Pathway ◽  
Geometric Mean ◽  
Critical Role ◽  
Mek Inhibitor ◽  
Mitogen Activated Protein Kinase ◽  
Mapk Activity ◽  
Extracellular Signal ◽  
Mitogen Activated Protein ◽  
Signaling Domain

Thrombopoietin (TPO) plays a critical role in megakaryocyte proliferation and differentiation. Using various cultured cell lines, several recent studies have implicated the mitogen-activated protein kinase (MAPK) pathway in megakaryocyte differentiation. In the study reported here, we examined the role played by thrombopoietin-induced MAPK activity in a cytokine-dependent cell line (BAF3/Mpl) and in primary murine megakaryocytes. In both systems, extracellular signal-regulated protein kinase (ERK) 1 and 2 MAPK phosphorylation was rapidly induced by TPO stimulation. To identify the Mpl domain responsible for MAPK activation, BAF3 cells expressing truncated forms of the Mpl receptor were studied. Phosphorylation of ERKs did not require elements of the cytoplasmic signaling domain distal to Box 2 and was not dependent on phosphorylation of the adapter protein Shc. ERK activation in murine megakaryocytes was maximal at 10 minutes and was markedly decreased over the subsequent 3 hours. Next, the physiologic consequences of MAPK inhibition were studied. Using the MAPK kinase (MEK) inhibitor, PD 98059, blockade of MAPK activity substantially reduced TPO-dependent proliferation in BAF3/Mpl cells and markedly decreased mean megakaryocyte ploidy in cultures. To exclude an indirect effect of MAPK inhibition on stromal cells in whole bone marrow, CD41+ cells were selected and then cultured in TPO. The number of polyploid megakaryocytes derived from the CD41-selected cells was also significantly reduced by MEK inhibition, as was their geometric mean ploidy. These studies show an important role for MAPK in TPO-induced endomitosis and underscore the value of primary cells when studying the physiologic effects of signaling pathways.

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