scholarly journals Dominant negative Ras enhances lactogenic hormone-induced differentiation by blocking activation of the Raf-Mek-Erk signal transduction pathway

2004 ◽  
Vol 201 (2) ◽  
pp. 244-258 ◽  
Author(s):  
Maria Grazia Cerrito ◽  
Traci Galbaugh ◽  
Weihan Wang ◽  
Treasa Chopp ◽  
David Salomon ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Signal Transduction Pathway ◽  
Dominant Negative ◽  
Transduction Pathway ◽  
Induced Differentiation ◽  
Lactogenic Hormone

Hemojuvelin Acts as a Bone Morphogenetic Protein Co-Receptor To Regulate Hepcidin Expression.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 511-511 ◽  
Author(s):  
Franklin W. Huang ◽  
Jodie L. Babitt ◽  
Diedra M. Wrighting ◽  
Tarek A. Samad ◽  
Yin Xia ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Bone Morphogenetic Protein ◽  
Signal Transduction Pathway ◽  
Bmp Signaling ◽  
Dominant Negative ◽  
Transduction Pathway ◽  
Reporter Construct ◽  
Hepcidin Expression ◽  
Morphogenetic Protein ◽  
Juvenile Hemochromatosis

Abstract Juvenile hemochromatosis is a severe iron overload disorder resulting from mutations in the hemojuvelin (HJV) gene. To understand its pathogenesis, we developed Hjv−/− mice. Similar to human patients, Hjv−/− animals accumulate excess iron in the liver, pancreas and heart early in life. Tissue macrophages are iron-depleted. Hjv−/− mice express very low levels of hepcidin mRNA and, likely as a consequence, have elevated expression of the iron transporter ferroportin in enterocytes and macrophages. These results suggested that Hjv plays a role in regulating hepcidin expression. Two known Hjv homologs, Rgma and Rgmb, have previously been shown to act as bone morphogenetic protein (BMP) co-receptors. We hypothesized that Hjv regulates hepcidin expression through a BMP signal transduction pathway. We found that Hjv binds radiolabeled BMP, supporting the contention that it is a BMP co-receptor. Transfection of HepG2 cells with Hjv cDNA activated a BMP-responsive reporter construct and augmented its response to exogenous BMP. Both an anti-BMP neutralizing antibody and the natural BMP antagonist Noggin blocked this response, as did co-expressed dominant negative BMP receptor proteins. When cells were transfected with a construct carrying an Hjv mutation known to cause human disease, BMP reporter activation was significantly reduced in the presence and absence of exogenous BMP. Treatment with BMP stimulated hepcidin production in hepatoma cells and activated a reporter construct containing a fragment of the hepcidin promoter. To extend these results, we studied tissues from Hjv−/− mice. BMP signals are transduced through phosphorylation of Smad proteins. We found that Smads 1, 5 and 8 were hypophosphorylated in Hjv−/− liver, consistent with impaired BMP signaling. BMP treatment of wild type and Hjv−/− primary hepatocytes induced hepcidin expression, but induction was blunted in cells from Hjv−/− animals. Taken together, these data suggest that the normal hepatic function of Hjv is to serve as a BMP co-receptor, modulating a signal transduction pathway that culminates in hepcidin expression. [Note - Jodie L. Babitt is the first author of this abstract, but it will be presented by Franklin W. Huang, the second author]

scholarly journals Genetic evidence for signal transduction within the Bacillus subtilis GerA germinant receptor

2021 ◽  
Author(s):  
Jeremy D. Amon ◽  
Lior Artzi ◽  
David Z. Rudner
Keyword(s):  
Signal Transduction ◽  
Bacillus Subtilis ◽  
Signal Transduction Pathway ◽  
Dominant Negative ◽  
Transduction Pathway ◽  
Sense And Respond ◽  
Enrichment Strategy ◽  
Functional Receptor

Bacterial spores can rapidly exit dormancy through the process of germination. This process begins with the activation of nutrient receptors embedded in the spore membrane. The prototypical germinant receptor in Bacillus subtilis responds to L-alanine and is thought to be a complex of proteins encoded by the genes in the gerA operon: gerAA , gerAB , and gerAC . The GerAB subunit has recently been shown to function as the nutrient sensor, but beyond contributing to complex stability, no additional functions have been attributed to the other two subunits. Here, we investigate the role of GerAA. We resurrect a previously characterized allele of gerA (termed gerA* ) that carries a mutation in gerAA and show it constitutively activates germination even in the presence of a wild-type copy of gerA . Using an enrichment strategy to screen for suppressors of gerA* , we identified mutations in all three gerA genes that restore a functional receptor. Characterization of two distinct gerAB suppressors revealed that one ( gerAB[E105K]) reduces the GerA complex's ability to respond to L-alanine, while another ( gerAB[F259S] ) disrupts the germinant signal downstream of L-alanine recognition. These data argue against models in which GerAA is directly or indirectly involved in germinant sensing. Rather, our data suggest that GerAA is responsible for transducing the nutrient signal sensed by GerAB. While the steps downstream of gerAA have yet to be uncovered, these results validate the use of a dominant-negative genetic approach in elucidating the gerA signal transduction pathway. Importance Endospore formers are a broad group of bacteria that can enter dormancy upon starvation and exit dormancy upon sensing the return of nutrients. How dormant spores sense and respond to these nutrients is poorly understood. Here, we identify a key step in the signal transduction pathway that is activated after spores detect the amino acid L-alanine. We present a model that provides a more complete picture of this process that is critical for allowing dormant spores to germinate and resume growth.

scholarly journals Regulation and Function of the Sonic Hedgehog Signal Transduction Pathway in Isolated Gastric Parietal Cells

2005 ◽  
Vol 280 (16) ◽  
pp. 15700-15708 ◽  
Author(s):  
Vinzenz Stepan ◽  
Saravanan Ramamoorthy ◽  
Hildegard Nitsche ◽  
Yana Zavros ◽  
Juanita L. Merchant ◽  
...  
Keyword(s):  
Gene Expression ◽  
Signal Transduction ◽  
Sonic Hedgehog ◽  
Luciferase Activity ◽  
Signal Transduction Pathway ◽  
Parietal Cells ◽  
Dominant Negative ◽  
Transduction Pathway ◽  
Subunit Gene ◽  
Α Subunit

Shh (Sonic hedgehog) regulates gastric epithelial cell differentiation. We reported that incubation of purified canine parietal cells with epidermal growth factor (EGF) for 6–16 h, stimulates H+/K+-ATPase α-subunit gene expression through the activation of Akt. We explored if Shh mediates some of the actions of EGF in the parietal cells. EGF induced a 6-fold increase in Shh expression, measured by Western blots, after 5 h of incubation. This effect was inhibited by both the phosphatidylinositol 3-kinase inhibitor LY294002 and by transduction of the cells with an adenoviral vector expressing dominant negative Akt. EGF stimulated the release of Shh-like immunoreactivity from the parietal cells, after 16 h of incubation. Shh induced H+/K+-ATPase α-subunit gene expression, assessed by Northern blots, it stimulated a luciferase reporter plasmid containing the EGF-responsive sequence (ERE) of the canine H+/K+-ATPase α-subunit gene promoter, and it induced parietal cell nuclear protein binding to the ERE. Gli transcription factors mediate the intracellular actions of Shh. Co-transfection of the parietal cells with the H+/K+-luc plasmid together with one expressing Gli2, induced H+/K+-luciferase activity 5-fold, whereas co-transfection of the cells with the H+/K+-luc plasmid together with one expressing dominant negative Gli2, inhibited EGF induction of H+/K+-luciferase activity. Identical results were observed in the presence of the Shh signal transduction pathway inhibitor, cyclopamine. Transfection of the cells with dominant negative Akt inhibited EGF, but not Shh stimulation of H+/K+-ATPase-luciferase activity. Thus, EGF but not Shh signals through Akt. Preincubation of the cells for 16 h with either Shh or EGF enhanced histamine-stimulated [14C]aminopyrine uptake by 50%. In conclusions, some of the actions of EGF in the parietal cells are mediated by the sequential activation of the Akt and the Shh signal transduction pathways. These effects might represent novel mechanisms mediating the actions of growth factors on gastric epithelial cell differentiation.

scholarly journals Micrococci and Peptidoglycan Activate TLR2→MyD88→IRAK→TRAF→NIK→IKK→NF-κB Signal Transduction Pathway That Induces Transcription of Interleukin-8

2001 ◽  
Vol 69 (4) ◽  
pp. 2270-2276 ◽  
Author(s):  
Qiuling Wang ◽  
Roman Dziarski ◽  
Carsten J. Kirschning ◽  
Marta Muzio ◽  
Dipika Gupta
Keyword(s):  
Signal Transduction ◽  
Tumor Necrosis Factor Receptor ◽  
Signal Transduction Pathway ◽  
Dominant Negative ◽  
Interleukin 8 ◽  
Hek293 Cells ◽  
Transduction Pathway ◽  
Iκb Kinase ◽  
Negative Tumor ◽  
Mutant Forms

ABSTRACT This study was done to elucidate the signal transduction pathway of interleukin-8 (IL-8) induction by gram-positive bacteria. Bacteria (micrococci) and peptidoglycan (PGN) induced transcription of IL-8 in HEK293 cells expressing Toll-like receptor 2 (TLR2) and CD14 but not in those expressing TLR1 or TLR4. A mutation within the NF-κB site in the IL-8 promoter abrogated transcriptional induction of IL-8 by the two stimulants. Dominant negative myeloid differentiation protein (MyD88), IL-1 receptor-associated kinase (IRAK), NFκB-inducing kinase (NIK), and IκB kinase (IKK) mutant forms completely inhibited micrococcus- and PGN-induced activation of NF-κB and expression of the gene for IL-8. Induction of NF-κB was partially inhibited by dominant negative tumor necrosis factor receptor-associated kinase 6 (TRAF6) but not TRAF2, whereas induction of IL-8 gene was partially inhibited by both TRAF6 and TRAF2. These data indicate that micrococci and PGN induce TLR2-dependent activation of the gene for IL-8 and that this activation requires MyD88, IRAK, NIK, IKK, and NF-κB and may also utilize TRAF6 and, to a lesser extent, TRAF2.

Platelet-derived growth factor-BB-mediated glycosaminoglycan synthesis is transduced through Akt

2002 ◽  
Vol 363 (1) ◽  
pp. 19-28 ◽  
Author(s):  
Nicholas J. CARTEL ◽  
Jinxia WANG ◽  
Martin POST
Keyword(s):  
Signal Transduction ◽  
Growth Factor ◽  
Signal Transduction Pathway ◽  
Fetal Lung ◽  
Dominant Negative ◽  
Platelet Derived Growth Factor ◽  
Lung Fibroblasts ◽  
Transduction Pathway ◽  
Over Expression ◽  
Β Receptor

Previously we have demonstrated that the phosphoinositide 3-kinase (PI-3K) signal-transduction pathway mediates platelet-derived growth factor (PDGF)-BB-induced glycosaminoglycan (GAG) synthesis in fetal lung fibroblasts. In the present study we further investigated the signal-transduction pathway(s) that results in PDGF-BB-induced GAG synthesis. Over-expression of a soluble PDGF β-receptor as well as a mutated form of the β-receptor, unable to bind PI-3K, diminished GAG synthesis in fetal lung fibroblasts subsequent to PDGF-BB stimulation. The PI-3K inhibitor wortmannin blocked PDGF-BB-induced Akt activity as well as significantly diminishing PDGF-BB-mediated GAG synthesis. Expression of dominant-negative PI-3K also abrogated Akt activity and GAG synthesis. Furthermore, expression of dominant-negative Akt abrogated endogenous Akt activity, Rab3D phosphorylation and GAG synthesis, whereas expression of constitutively activated Akt stimulated Rab3D phosphorylation and GAG synthesis in the absence of PDGF-BB. Over-expression of wild-type PTEN (phosphatase and tensin homologue deleted in chromosome 10) inhibited Akt activity and concomitantly attenuated GAG synthesis in fibroblasts stimulated with PDGF-BB. These data suggest that Akt is an integral protein involved in PDGF-BB-mediated GAG regulation in fetal lung fibroblasts.

scholarly journals rac1 regulates a cytokine-stimulated, redox-dependent pathway necessary for NF-kappaB activation.

1996 ◽  
Vol 16 (12) ◽  
pp. 7115-7121 ◽  
Author(s):  
D J Sulciner ◽  
K Irani ◽  
Z X Yu ◽  
V J Ferrans ◽  
P Goldschmidt-Clermont ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Hela Cells ◽  
Recombinant Adenovirus ◽  
Signal Transduction Pathway ◽  
Nuclear Extract ◽  
Dominant Negative ◽  
Transduction Pathway ◽  
Amino Terminal ◽  
Dependent Signal ◽  
Nf Kappab

The signal transduction pathway leading to the activation of the transcription factor NF-kappaB remains incompletely characterized. We demonstrate that in HeLa cells, transient expression of a constitutively active mutant of the small GTP-binding protein rac1 (V12rac1) leads to a significant increase in NF-kappaB transcriptional activity. In addition, expression of a dominant-negative rac1 mutant (N17rac1) inhibits basal and interleukin 1beta-stimulated NF-kappaB activity. Gel shift analysis using nuclear extract prepared from HeLa cells infected with a recombinant adenovirus encoding N17rac1 (Ad.N17racl) showed reduced levels of cytokine-stimulated DNA binding to a consensus NF-kappaB binding site. We demonstrate that rac proteins function downstream of ras proteins in the activation of NF-kappaB. In addition, V12rac1 stimulation of NF-kappaB activity is shown to be independent of the ability of rac proteins to activate the family of c-jun amino-terminal kinases. In an effort to further explore how rac proteins might regulate NF-kappaB activity, we demonstrate that expression of V12rac1 in HeLa cells or stimulation with cytokine results in a significant increase in intracellular reactive oxygen species (ROS). Treatment of cells with either of two chemically unrelated antioxidants inhibits the rise in ROS that occurs following V12rac1 expression as well as the ability of V12rac1 to stimulate NF-kappaB activity. These results suggest that in HeLa cells, rac1 regulates intracellular ROS production and that rac proteins function as part of a redox-dependent signal transduction pathway leading to NF-kappaB activation.

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