scholarly journals Differential Roles of Akt, Rac, and Ral in R-Ras-Mediated Cellular Transformation, Adhesion, and Survival

1999 ◽  
Vol 19 (9) ◽  
pp. 6333-6344 ◽  
Author(s):  
Masako Osada ◽  
Tatyana Tolkacheva ◽  
Weiqun Li ◽  
Tung O. Chan ◽  
Philip N. Tsichlis ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Protein Kinase ◽  
Biological Activities ◽  
Cellular Transformation ◽  
Dominant Negative ◽  
Mitogen Activated Protein Kinase ◽  
Signaling Cascades ◽  
Dominant Negative Mutant ◽  
Negative Mutant ◽  
Promote Cell Adhesion

ABSTRACT Multiple biological functions have been ascribed to the Ras-related G protein R-Ras. These include the ability to transform NIH 3T3 fibroblasts, the promotion of cell adhesion, and the regulation of apoptotic responses in hematopoietic cells. To investigate the signaling mechanisms responsible for these biological phenotypes, we compared three R-Ras effector loop mutants (S61, G63, and C66) for their relative biological and biochemical properties. While the S61 mutant retained the ability to cause transformation, both the G63 and the C66 mutants were defective in this biological activity. On the other hand, while both the S61 and the C66 mutants failed to promote cell adhesion and survival in 32D cells, the G63 mutant retained the ability to induce these biological activities. Thus, the ability of R-Ras to transform cells could be dissociated from its propensity to promote cell adhesion and survival. Although the transformation-competent S61 mutant bound preferentially to c-Raf, it only weakly stimulated the mitogen-activated protein kinase (MAPK) activity, and a dominant negative mutant of MEK did not significantly perturb R-Ras oncogenicity. Instead, a dominant negative mutant of phosphatidylinositol 3-kinase (PI3-K) drastically inhibited the oncogenic potential of R-Ras. Interestingly, the ability of the G63 mutant to induce cell adhesion and survival was closely associated with the PI3-K-dependent signaling cascades. To further delineate R-Ras downstream signaling events, we observed that while a dominant negative mutant of Akt/protein kinase inhibited the ability of R-Ras to promote cell survival, both dominant negative mutants of Rac and Ral suppressed cell adhesion stimulated by R-Ras. Thus, the biological actions of R-Ras are mediated by multiple effectors, with PI3-K-dependent signaling cascades being critical to its functions.

scholarly journals UVB-mediated activation of p38 mitogen-activated protein kinase enhances resistance of normal human keratinocytes to apoptosis by stabilizing cytoplasmic p53

2002 ◽  
Vol 365 (1) ◽  
pp. 133-145 ◽  
Author(s):  
Nadine CHOUINARD ◽  
Kristoffer VALERIE ◽  
Mahmoud ROUABHIA ◽  
Jacques HUOT
Keyword(s):  
Adaptive Response ◽  
Human Keratinocytes ◽  
Dominant Negative ◽  
Mitogen Activated Protein Kinase ◽  
Dominant Negative Mutant ◽  
Normal Human Keratinocytes ◽  
Mitogen Activated Protein ◽  
Normal Human ◽  
Induced Apoptosis ◽  
Negative Mutant

Human keratinocytes respond to UV rays by developing a fast adaptive response that contributes to maintaining their functions and survival. We investigated the role of the mitogen-activated protein kinase pathways in transducing the UV signals in normal human keratinocytes. We found that UVA, UVB or UVC induced a marked and persistent activation of p38, whereas c-Jun N-terminal kinase or extracellular signal-regulated kinase were less or not activated respectively. Inhibition of p38 activity by expression of a dominant-negative mutant of p38 or with SB203580 impaired cell viability and led to an increase in UVB-induced apoptosis. This sensitization to apoptosis was independent of caspase activities. Inhibition of p38 did not sensitize transformed HaCaT keratinocytes to UVB-induced apoptosis. In normal keratinocytes, expression of a dominant-negative mutant of p53 increased UVB-induced cell death, pointing to a role for p53. In these cells, UVB triggered a p38-dependent phosphorylation of p53 on Ser-15. This phosphorylation was associated with an SB203580-sensitive accumulation of p53, even in the presence of a serine phosphatase inhibitor. Accumulated p53 was localized mainly in the cytoplasm, independently of CRM1 nuclear export. In HaCaT cells, p53 was localized exclusively in the nucleus and its distribution and level were not affected by UVB or p38 inhibition. However, UVB induced an SB203580-insensitive phosphorylation on Ser-15 of mutated p53. Overall, our results suggest that, in normal human keratinocytes, protection against UVB depends on p38-mediated phosphorylation and stabilization of p53 and is tightly associated with the cytoplasmic sequestration of wild-type p53. We conclude that the p38/p53 pathway plays a key role in the adaptive response of normal human keratinocytes against UV stress.

scholarly journals Role of Nectin in Formation of E-Cadherin–based Adherens Junctions in Keratinocytes: Analysis with the N-Cadherin Dominant Negative Mutant

2003 ◽  
Vol 14 (4) ◽  
pp. 1597-1609 ◽  
Author(s):  
Yoshinari Tanaka ◽  
Hiroyuki Nakanishi ◽  
Shigeki Kakunaga ◽  
Noriko Okabe ◽  
Tomomi Kawakatsu ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Adhesion Molecule ◽  
Cell Adhesion Molecule ◽  
Adherens Junctions ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Adhesion Activity ◽  
Negative Mutant ◽  
E Cadherin ◽  
Cell Cell

E-Cadherin is a Ca2+-dependent cell-cell adhesion molecule at adherens junctions (AJs) of epithelial cells. A fragment of N-cadherin lacking its extracellular region serves as a dominant negative mutant (DN) and inhibits cell-cell adhesion activity of E-cadherin, but its mode of action remains to be elucidated. Nectin is a Ca2+-independent immunoglobulin-like cell-cell adhesion molecule at AJs and is associated with E-cadherin through their respective peripheral membrane proteins, afadin and catenins, which connect nectin and cadherin to the actin cytoskeleton, respectively. We showed here that overexpression of nectin capable of binding afadin, but not a mutant incapable of binding afadin, reduced the inhibitory effect of N-cadherin DN on the cell-cell adhesion activity of E-cadherin in keratinocytes. Overexpressed nectin recruited N-cadherin DN to the nectin-based cell-cell adhesion sites in an afadin-dependent manner. Moreover, overexpression of nectin enhanced the E-cadherin–based cell-cell adhesion activity. These results suggest that N-cadherin DN competitively inhibits the association of the endogenous nectin-afadin system with the endogenous E-cadherin-catenin system and thereby reduces the cell-cell adhesion activity of E-cadherin. Thus, nectin plays a role in the formation of E-cadherin–based AJs in keratinocytes.

Expression of a dominant negative cadherin mutant inhibits proliferation and stimulates terminal differentiation of human epidermal keratinocytes

1996 ◽  
Vol 109 (13) ◽  
pp. 3013-3023 ◽  
Author(s):  
A.J. Zhu ◽  
F.M. Watt
Keyword(s):  
Cell Adhesion ◽  
Terminal Differentiation ◽  
Intercellular Adhesion ◽  
Dominant Negative ◽  
Epidermal Keratinocytes ◽  
Dominant Negative Mutant ◽  
Beta Catenin ◽  
Human Epidermal Keratinocytes ◽  
Negative Mutant ◽  
E Cadherin

Cell adhesion molecules are not only required for maintenance of tissue integrity, but also regulate many aspects of cell behaviour, including growth and differentiation. While the regulatory functions of integrin extracellular matrix receptors in keratinocytes are well established, such functions have not been investigated for the primary receptors that mediate keratinocyte intercellular adhesion, the cadherins. To examine cadherin function in normal human epidermal keratinocytes we used a retroviral vector to introduce a dominant negative E-cadherin mutant, consisting of the extracellular domain of H-2Kd and the transmembrane and cytoplasmic domains of E-cadherin. As a control a vector containing the same construct, but with the catenin binding site destroyed, was prepared. High levels of expression of the constructs were achieved; the dominant negative mutant, but not the control, formed complexes with alpha-, beta- and gamma-catenin. In cells expressing the dominant negative mutant there was a 5-fold decrease in the level of endogenous cadherins and a 3-fold increase in the level of beta-catenin. Cell-cell adhesion and stratification were inhibited by the dominant negative mutant and desmosome formation was reduced. Expression of the mutant resulted in reduced levels of the alpha 2 beta 1 and alpha 3 beta 1 integrins and increased cell motility, providing further evidence for cross-talk between cadherins and the beta 1 integrins. In view of the widely documented loss of E-cadherin in keratinocyte tumours it was surprising that the dominant negative mutant had an inhibitory effect on keratinocyte proliferation and stimulated terminal differentiation even under conditions in which intercellular adhesion was prevented. These results establish a role for cadherins in regulating keratinocyte growth and differentiation and raise interesting questions as to the relative importance of cell adhesion-dependent and -independent mechanisms.

Epithelial injury induces Egr-1 and Fos expression by a pathway involving protein kinase C and ERK

1999 ◽  
Vol 276 (2) ◽  
pp. G322-G330 ◽  
Author(s):  
Brian K. Dieckgraefe ◽  
Danielle M. Weems
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Dominant Negative ◽  
Mitogen Activated Protein Kinase ◽  
Dominant Negative Mutant ◽  
Mrna Levels ◽  
Mobility Shift ◽  
Erk Activation ◽  
Kinase C

The signaling pathways activated in response to gastrointestinal injury remain poorly understood. Previous work has implicated the extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase as a mediator of wound-signal transduction and a possible regulator of epithelial restitution. Monolayer injury resulted in rapid activation of p42 and p44 ERK. Injury-induced ERK activation was blocked by protein kinase C inhibition or by disruption of the cell cytoskeleton. Significant increases in Fos and early growth response (Egr)-1 mRNA levels were stimulated by injury, peaking by 20 min. ERK activation and the induction of Egr-1 mRNA were inhibited in a dose-dependent fashion with PD-98059. Fos mRNA expression was partially blocked by PD-98059. Western blot analysis demonstrated strong expression and nuclear localization of Fos and Egr after wounding. Electrophoretic mobility shift assays demonstrated that nuclear extracts contained a protein that specifically bound double-stranded oligonucleotides containing the Egr consensus binding element. Gel supershift assays demonstrated that the protein-DNA complexes were recognized by anti-Egr antibody. Inhibition of injury-induced ERK activation by PD-98059 or direct interference with Egr by expression of a dominant negative mutant led to significantly reduced in vitro monolayer restitution.

scholarly journals Akt-Dependent Phosphorylation Specifically Regulates Cot Induction of NF-κB-Dependent Transcription

2002 ◽  
Vol 22 (16) ◽  
pp. 5962-5974 ◽  
Author(s):  
Lawrence P. Kane ◽  
Marianne N. Mollenauer ◽  
Zheng Xu ◽  
Christoph W. Turck ◽  
Arthur Weiss
Keyword(s):  
Protein Kinase ◽  
Signaling Pathways ◽  
Cellular Transformation ◽  
Dominant Negative ◽  
Mitogen Activated Protein Kinase ◽  
Iκb Kinase ◽  
Ikk Complex ◽  
Mitogen Activated Protein ◽  
Tumor Necrosis Factor Induction ◽  
Necrosis Factor

ABSTRACT The Akt (or protein kinase B) and Cot (or Tpl-2) serine/threonine kinases are associated with cellular transformation. These kinases have also been implicated in the induction of NF-κB-dependent transcription. As a member of the mitogen-activated protein kinase kinase kinase (MAP3K) family, Cot can also activate MAP kinase signaling pathways that target AP-1 and NFAT family transcription factors. Here we show that Akt and Cot physically associate and functionally cooperate. Akt appears to function upstream of Cot, as Akt can enhance Cot induction of NF-κB-dependent transcription, and dominant-negative Cot blocks the activation of this element by Akt. Furthermore, deletion analysis shows that binding to Akt is critical for Cot function. The regulation of NF-κB-dependent transcription by Cot requires Akt-dependent phosphorylation of serine 400 (S400), near the carboxy terminus of Cot. However, phosphorylation at this site is not required for Cot kinase activity or AP-1 induction, suggesting it specifically regulates Cot effector function at the level of the NF-κB pathway. Mutation of S400 in Cot does indeed abolish its ability to activate IκB-kinase (IKK) complexes, but paradoxically it allows for increased Cot association with the IKK complex. This mutated form of Cot also acts as a dominant negative for T-cell antigen receptor/CD28- or Akt/phorbol myristate acetate-induced NF-κB induction, while having relatively little effect on tumor necrosis factor induction of NF-κB. These findings suggest that the activation of different signaling pathways by MAP3Ks may be regulated separately and may provide evidence for how such discrimination by one member of this kinase family occurs.

scholarly journals Role of MKK3 and p38 MAPK in cytokine-induced death of insulin-producing cells

2005 ◽  
Vol 393 (1) ◽  
pp. 129-139 ◽  
Author(s):  
Natalia Makeeva ◽  
Jason W. Myers ◽  
Nils Welsh
Keyword(s):  
Nitric Oxide ◽  
Cell Death ◽  
Protein Kinase ◽  
P38 Mapk ◽  
Dominant Negative ◽  
Mitogen Activated Protein Kinase ◽  
Nitric Oxide Donor ◽  
Cell Leukaemia ◽  
Dominant Negative Mutant

The aim of the present investigation was to elucidate further the importance of p38 MAPK (mitogen-activated protein kinase) in nitric oxide- and cytokine-induced β-cell death. For this purpose, isolated human islets were treated with d-siRNA (diced small interfering RNA) and then exposed to the nitric oxide donor DETA/NONOate [2,2′-(hydroxynitrosohydrazono)bis-ethanamine]. We observed that cells treated with p38α-specific d-siRNA, but not with d-siRNA targeting GL3 (a firefly luciferase siRNA plasmid) or PKCδ (protein kinase Cδ), were protected against nitric oxide-induced death. This was paralleled by an increased level of Bcl-XL (B-cell leukaemia/lymphoma-X long). For an in-depth study of the mechanisms of p38 activation, MKK3 (MAPK kinase 3), MKK6 and their dominant-negative mutants were overexpressed in insulin-producing RIN-5AH cells. In transient transfections, MKK3 overexpression resulted in increased p38 phosphorylation, whereas in stable MKK3-overexpressing RIN-5AH clones, the protein levels of p38 and JNK (c-Jun N-terminal kinase) were decreased, resulting in unaffected phospho-p38 levels. In addition, a long-term MKK3 overexpression did not affect cell death rates in response to the cytokines interleukin-1β and interferon-γ, whereas a short-term MKK3 expression resulted in increased cytokine-induced RIN-5AH cell death. The MKK3-potentiating effect on cytokine-induced cell death was abolished by a nitric oxide synthase inhibitor, and MKK3-stimulated p38 phosphorylation was enhanced by inhibitors of phosphatases. Finally, as the dominant-negative mutant of MKK3 did not affect cytokine-induced p38 phosphorylation, and as wild-type MKK3 did not influence p38 autophosphorylation, it may be that p38 is activated by MKK3/6-independent pathways in response to cytokines and nitric oxide. In addition, it is likely that a long-term increase in p38 activity is counteracted by both a decreased expression of the p38, JNK and p42 genes as well as an increased dephosphorylation of p38.

scholarly journals Coordinate Regulation of IκB Kinases by Mitogen-Activated Protein Kinase Kinase Kinase 1 and NF-κB-Inducing Kinase

1998 ◽  
Vol 18 (12) ◽  
pp. 7336-7343 ◽  
Author(s):  
Shino Nemoto ◽  
Joseph A. DiDonato ◽  
Anning Lin
Keyword(s):  
Protein Kinase ◽  
Interleukin 1 ◽  
Dominant Negative ◽  
Mitogen Activated Protein Kinase ◽  
Dominant Negative Mutant ◽  
Necrosis Factor Alpha ◽  
Tnf Α ◽  
Ikk Complex ◽  
Mitogen Activated Protein ◽  
Protein Kinase Kinase

ABSTRACT IκB kinases (IKKα and IKKβ) are key components of the IKK complex that mediates activation of the transcription factor NF-κB in response to extracellular stimuli such as inflammatory cytokines, viral and bacterial infection, and UV irradiation. Although NF-κB-inducing kinase (NIK) interacts with and activates the IKKs, the upstream kinases for the IKKs still remain obscure. We identified mitogen-activated protein kinase kinase kinase 1 (MEKK1) as an immediate upstream kinase of the IKK complex. MEKK1 is activated by tumor necrosis factor alpha (TNF-α) and interleukin-1 and can potentiate the stimulatory effect of TNF-α on IKK and NF-κB activation. The dominant negative mutant of MEKK1, on the other hand, partially blocks activation of IKK by TNF-α. MEKK1 interacts with and stimulates the activities of both IKKα and IKKβ in transfected HeLa and COS-1 cells and directly phosphorylates the IKKs in vitro. Furthermore, MEKK1 appears to act in parallel to NIK, leading to synergistic activation of the IKK complex. The formation of the MEKK1-IKK complex versus the NIK-IKK complex may provide a molecular basis for regulation of the IKK complex by various extracellular signals.

scholarly journals Immediate and Delayed Effects of E-Cadherin Inhibition on Gene Regulation and Cell Motility in Human Epidermoid Carcinoma Cells

2005 ◽  
Vol 25 (20) ◽  
pp. 9138-9150 ◽  
Author(s):  
Henriette Andersen ◽  
Jakob Mejlvang ◽  
Shaukat Mahmood ◽  
Irina Gromova ◽  
Pavel Gromov ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Cell Motility ◽  
Family Members ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Short Term ◽  
Mesenchymal Transition ◽  
Negative Mutant ◽  
E Cadherin ◽  
Cell Cell

ABSTRACT The invasion suppressor protein, E-cadherin, plays a central role in epithelial cell-cell adhesion. Loss of E-cadherin expression or function in various tumors of epithelial origin is associated with a more invasive phenotype. In this study, by expressing a dominant-negative mutant of E-cadherin (Ec1WVM) in A431 cells, we demonstrated that specific inhibition of E-cadherin-dependent cell-cell adhesion led to the genetic reprogramming of tumor cells. In particular, prolonged inhibition of cell-cell adhesion activated expression of vimentin and repressed cytokeratins, suggesting that the effects of Ec1WVM can be classified as epithelial-mesenchymal transition. Both short-term and prolonged expression of Ec1WVM resulted in morphological transformation and increased cell migration though to different extents. Short-term expression of Ec1WVM up-regulated two AP-1 family members, c-jun and fra-1, but was insufficient to induce complete mesenchymal transition. AP-1 activity induced by the short-term expression of Ec1WVM was required for transcriptional up-regulation of AP-1 family members and down-regulation of two other Ec1WVM-responsive genes, S100A4 and igfbp-3. Using a dominant-negative mutant of c-Jun (TAM67) and RNA interference-mediated silencing of c-Jun and Fra-1, we demonstrated that AP-1 was required for cell motility stimulated by the expression of Ec1WVM. In contrast, Ec1WVM-mediated changes in cell morphology were AP-1-independent. Our data suggest that mesenchymal transition induced by prolonged functional inhibition of E-cadherin is a slow and gradual process. At the initial step of this process, Ec1WVM triggers a positive autoregulatory mechanism that increases AP-1 activity. Activated AP-1 in turn contributes to Ec1WVM-mediated effects on gene expression and tumor cell motility. These data provide novel insight into the tumor suppressor function of E-cadherin.

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