scholarly journals The Repertoire of Fos and Jun Proteins Expressed during the G1 Phase of the Cell Cycle Is Determined by the Duration of Mitogen-Activated Protein Kinase Activation

1999 ◽  
Vol 19 (1) ◽  
pp. 330-341 ◽  
Author(s):  
Simon J. Cook ◽  
Natasha Aziz ◽  
Martin McMahon

ABSTRACT In Rat-1 fibroblasts nonmitogenic doses of lysophosphatidic acid (LPA) stimulate a transient activation of mitogen-activated protein kinase (MAPK), whereas mitogenic doses elicit a sustained response. This sustained phase of MAPK activation regulates cell fate decisions such as proliferation or differentiation, presumably by inducing a program of gene expression which is not observed in response to transient MAPK activation. We have examined the expression of members of the AP-1 transcription factor complex in response to stimulation with different doses of LPA. c-Fos, c-Jun, and JunB are induced rapidly in response to LPA stimulation, whereas Fra-1 and Fra-2 are induced after a significant lag. The expression of c-Fos is transient, whereas the expression of c-Jun, JunB, Fra-1, and Fra-2 is sustained. The early expression of c-Fos can be reconstituted with nonmitogenic doses of LPA, but the response is transient compared to that observed with mitogenic doses. In contrast, expression of Fra-1, Fra-2, and JunB and optimal expression of c-Jun are observed only with doses of LPA which induce sustained MAPK activation and DNA synthesis. LPA-stimulated expression of c-Fos, Fra-1, Fra-2, c-Jun, and JunB is inhibited by the MEK1 inhibitor PD098059, indicating that the Raf-MEK-MAPK cascade is required for their expression. In cells expressing a conditionally active form of Raf-1 (ΔRaf-1:ER), we observed that selective, sustained activation of Raf-MEK-MAPK was sufficient to induce expression of Fra-1, Fra-2, and JunB but, interestingly, induced little or no c-Fos or c-Jun. The induction of c-Fos observed in response to LPA was strongly inhibited by buffering the intracellular [Ca2+]. Moreover, although Raf activation or calcium ionophores induced little c-Fos expression, we observed a synergistic induction in response to the combination of ΔRaf-1:ER and ionomycin. These results suggest that kinetically distinct phases of MAPK activation serve to regulate the expression of distinct AP-1 components such that sustained MAPK activation is required for the induced expression of Fra-1, Fra-2, c-Jun, and JunB. However, in contrast to the case for Fra-1, Fra-2, and JunB, activation of the MAPK cascade alone is not sufficient to induce c-Fos expression, which rather requires cooperation with other signals such as Ca2+mobilization. Finally, the identification of the Fra-1, Fra-2, c-Jun, and JunB genes as genes which are selectively regulated by sustained MAPK activation or in response to activated Raf suggests that they are candidates to mediate certain of the effects of Ras proteins in oncogenic transformation.

1994 ◽  
Vol 267 (4) ◽  
pp. C1130-C1135 ◽  
Author(s):  
Y. Wang ◽  
P. M. Rose ◽  
M. L. Webb ◽  
M. J. Dunn

Endothelin (ET) has been shown to activate mitogen-activated protein kinase (MAPK). However, it has been unclear which of the ET receptors is coupled to MAPK activation. In the present study, we conducted experiments to determine which ET receptor is linked to MAPK activation. We found that both human ETA and ETB were coupled to the MAPK cascade in ETA or ETB cDNA-transfected Chinese hamster ovary cells. ET-1 was more potent than ET-3 in the activation of p42 MAPK, induction of MAPK kinase (MAPKK) gel retardation and uptake of [3H]thymidine in ETA-transfected cells, whereas sarafotoxin (S6c) showed no stimulatory effect on the kinases and [3H]thymidine uptake. ET-1, ET-3, and S6c had approximately the same potency to activate p42 MAPK, MAPKK gel retardation, and [3H]thymidine uptake in ETB-transfected cells. These data suggest that 1) ET isopeptides, through either ETA or ETB receptors, induce the MAPK cascade as well as cell proliferation; and 2) the different potencies of ET isopeptides for activation of the MAPK cascade and induction of cell growth are mainly due to their different affinities toward ETA and ETB.


2005 ◽  
Vol 25 (11) ◽  
pp. 4676-4682 ◽  
Author(s):  
Jeffrey P. MacKeigan ◽  
Leon O. Murphy ◽  
Christopher A. Dimitri ◽  
John Blenis

ABSTRACT The mitogen-activated protein kinase (MAPK) pathway is an evolutionarily conserved signaling module that controls important cell fate decisions in a variety of physiological contexts. During Xenopus oocyte maturation, the MAPK cascade converts an increasing progesterone stimulus into a switch-like, all-or-nothing response. While the importance of such switch-like behavior is widely discussed in the literature, it is not known whether the MAPK pathway in mammalian cells exhibits a switch-like or graded response. For this study, we used flow cytometry and immunofluorescence to generate single-cell measurements of MAPK signaling in Swiss 3T3 fibroblasts. In contrast to the case in Xenopus oocytes, we found that ERK activation in individual mammalian cells is not ultrasensitive and shows a graded response to changes in agonist concentration. Thus, the conserved MAPK signaling module exhibits different systems-level properties in different cellular contexts. Furthermore, the graded ERK response was converted into a more switch-like behavior at the level of immediate-early gene induction and cell cycle progression. Thus, while MAPK signaling is involved in all-or-nothing cell fate decisions for both Xenopus oocyte maturation and mammalian fibroblast proliferation, the underlying mechanisms responsible for the switch-like nature of the cellular responses are different in these two systems, with the mechanism appearing to lie downstream of the kinase cascade in mammalian fibroblasts.


2009 ◽  
Vol 29 (8) ◽  
pp. 2082-2091 ◽  
Author(s):  
Joseph Lin ◽  
Angus Harding ◽  
Emanuele Giurisato ◽  
Andrey S. Shaw

ABSTRACT Mitogen-activated protein kinase (MAPK) cascades are evolutionarily conserved signaling pathways that regulate cell fate decisions. They generate a wide range of signal outputs, including graded and digital responses. In T cells, MAPK activation is digital in response to T-cell-receptor stimulation; however, whether other receptors on T cells that lead to MAPK activation are graded or digital is unknown. Here we evaluate MAPK activation in T cells at the single-cell level. We show that T cells responded digitally to stimulation with superantigen-loaded antigen-presenting cells, whereas they responded in a graded manner to the chemokine SDF-1, demonstrating that the system output of the MAPK module is highly plastic and determined by components upstream of the MAPK module. These findings also confirm that different MAPK system outputs are used by T cells to control discrete biological functions. Scaffold proteins are essential for proper MAPK signaling and function as they physically assemble multiple components and regulators of MAPK cascades. We found that the scaffold protein KSR1 regulated the threshold required for MAPK activation in T cells without affecting the nature of the response. We conclude that KSR1 plays a central role in determining the sensitivity of T-cell responses and is thus well positioned as a key control point.


2009 ◽  
Vol 20 (3) ◽  
pp. 1020-1029 ◽  
Author(s):  
Wei Zuo ◽  
Ye-Guang Chen

Transforming growth factor (TGF)-β regulates a spectrum of cellular events, including cell proliferation, differentiation, and migration. In addition to the canonical Smad pathway, TGF-β can also activate mitogen-activated protein kinase (MAPK), phosphatidylinositol 3-kinase (PI3K)/Akt, and small GTPases in a cell-specific manner. Here, we report that cholesterol depletion interfered with TGF-β–induced epithelial-mesenchymal transition (EMT) and cell migration. This interference is due to impaired activation of MAPK mediated by cholesterol-rich lipid rafts. Cholesterol-depleting agents specifically inhibited TGF-β–induced activation of extracellular signal-regulated kinase (ERK) and p38, but not Smad2/3 or Akt. Activation of ERK or p38 is required for both TGF-β–induced EMT and cell migration, whereas PI3K/Akt is necessary only for TGF-β–promoted cell migration but not for EMT. Although receptor heterocomplexes could be formed in both lipid raft and nonraft membrane compartments in response to TGF-β, receptor localization in lipid rafts, but not in clathrin-coated pits, is important for TGF-β–induced MAPK activation. Requirement of lipid rafts for MAPK activation was further confirmed by specific targeting of the intracellular domain of TGF-β type I receptor to different membrane locations. Together, our findings establish a novel link between cholesterol and EMT and cell migration, that is, cholesterol-rich lipid rafts are required for TGF-β–mediated MAPK activation, an event necessary for TGF-β–directed epithelial plasticity.


2011 ◽  
Vol 300 (1) ◽  
pp. E103-E110 ◽  
Author(s):  
Xiaoban Xin ◽  
Lijun Zhou ◽  
Caleb M. Reyes ◽  
Feng Liu ◽  
Lily Q. Dong

The adaptor protein APPL1 mediates the stimulatory effect of adiponectin on p38 mitogen-activated protein kinase (MAPK) signaling, yet the underlying mechanism remains unclear. Here we show that, in C2C12 cells, overexpression or suppression of APPL1 enhanced or suppressed, respectively, adiponectin-stimulated p38 MAPK upstream kinase cascade, consisting of transforming growth factor-β-activated kinase 1 (TAK1) and mitogen-activated protein kinase kinase 3 (MKK3). In vitro affinity binding and coimmunoprecipitation experiments revealed that TAK1 and MKK3 bind to different regions of APPL1, suggesting that APPL1 functions as a scaffolding protein to facilitate adiponectin-stimulated p38 MAPK activation. Interestingly, suppressing APPL1 had no effect on TNFα-stimulated p38 MAPK phosphorylation in C2C12 myotubes, indicating that the stimulatory effect of APPL1 on p38 MAPK activation is selective. Taken together, our study demonstrated that the TAK1-MKK3 cascade mediates adiponectin signaling and uncovers a scaffolding role of APPL1 in regulating the TAK1-MKK3-p38 MAPK pathway, specifically in response to adiponectin stimulation.


Author(s):  
Benjamin L. Shneider ◽  
Nahir Cortes-Santiago ◽  
Deborah A. Schady ◽  
Swapna Krishnamoorthy ◽  
Sundararajah Thevananther ◽  
...  

Activation of Mitogen-activated protein kinases (MAPKs) is a key factor in the pathogenesis of cancer, although the specific role of mitogen-activated protein kinase kinase (MEK1) is not well understood. Villin promoter driven cre expression was used to excise a floxed stop cassette from a phosphomimetically constitutively activated MEK1 (caMEK1) expression construct in the intestine of C57BL/6 mice. Zygosity status of caMEK1 afforded assessment of the dose dependence of the effect. The expected mendelian distribution of genotypes and sex was observed in 443 progenies. Between 21 and 63 days of life caMEK1 had no effect on body weight in male mice, but reduced body weight in female mice homozygous for caMEK1. At 10 weeks of age, the ileum of caMEK1 expressing mice was characterized by the finding of dysplasia and profound changes in overall architecture. Paneth cells were nearly absent in caMEK1 homozygotes. Targeted proteomic profiling via reverse phase protein array analyses with confirmatory western blotting revealed significant changes in protein and phosphoprotein expression including up-regulation of proteins downstream of MEK1, associated with enhanced markers of proliferation, diminished apoptosis, alterations in cell-fate determination, cell-cell interactions and tight junctions. Long-term viability of caMEK1 homozygous mice was reduced with no survival beyond one year. Invasive adenocarcinoma developed in three of ten older mice (15 [homozygous], 26 [homozygous] and 35 weeks [heterozygous] of age). Expression of caMEK1 in enterocytes leads to marked derangements in the intestinal epithelium, which is associated with a predisposition to the development of invasive cancer.


BMC Genomics ◽  
2020 ◽  
Vol 21 (1) ◽  
Author(s):  
Archita Chatterjee ◽  
Abhirup Paul ◽  
G. Meher Unnati ◽  
Ruchika Rajput ◽  
Trisha Biswas ◽  
...  

Abstract Background Mitogen Activated Protein Kinase (MAPK) cascade is a fundamental pathway in organisms for signal transduction. Though it is well characterized in various plants, there is no systematic study of this cascade in tea. Result In this study, 5 genes of Mitogen Activated Protein Kinase Kinase (MKK) and 16 genes of Mitogen Activated Protein Kinase (MPK) in Camellia sinensis were found through a genome-wide search taking Arabidopsis thaliana as the reference genome. Also, phylogenetic relationships along with structural analysis which includes gene structure, location as well as protein conserved motifs and domains, were systematically examined and further, predictions were validated by the results. The plant species taken for comparative study clearly displayed segmental duplication, which was a significant candidate for MAPK cascade expansion. Also, functional interaction was carried out in C. sinensis based on the orthologous genes in Arabidopsis. The expression profiles linked to various stress treatments revealed wide involvement of MAPK and MAPKK genes from Tea in response to various abiotic factors. In addition, the expression of these genes was analysed in various tissues. Conclusion This study provides the targets for further comprehensive identification, functional study, and also contributed for a better understanding of the MAPK cascade regulatory network in C. sinensis.


2000 ◽  
Vol 12 (4) ◽  
pp. 209 ◽  
Author(s):  
Naoki Iwamori ◽  
Kunihiko Naito ◽  
Koji Sugiura ◽  
Hideyuki Kagii ◽  
Masakane Yamashita ◽  
...  

The mitogen-activated protein kinase (MAPK) cascade is one of the most important signal transduction pathways that regulate the cell cycle in somatic cells. The present study examined the phosphorylation states of components in the MAPK cascade, Raf-1, MEK-1, and extracellular signal regulated kinases (ERKs), which are activated by mitogens, throughout early mouse embryo development and in cultured somatic cells generally. In somatic cells, Raf-1 and MEK-1 were phosphorylated at M-phase and dephosphorylated during interphase. ERKs were not phosphorylated at any stage during the cell cycle. These results were similar to previous findings for the first and second cell cycles of early mouse embryos. In contrast, after the four-cell stage, not only ERKs, but also Raf-1 and MEK-1, were not phosphorylated at any stage during the cell cycle in mouse early embryos. These results suggest that the MAPK cascade in mouse embryos is regulated by the same mechanism as in somatic cells before the two-cell stage, and that regulation is changed to an embryo-specific mechanism after the four-cell stage.


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