The same γ-glutamyl transpeptidase RNA species is expressed in fetal liver, hepatic carcinomas, and ras T24-transformed rat liver epithelial cells

1992 ◽  
Vol 5 (1) ◽  
pp. 75-80 ◽  
Author(s):  
Geetha M. Habib ◽  
Sridharan Rajagopalan ◽  
Andrew K. Godwin ◽  
Russell M. Lebovitz ◽  
Michael W. Lieberman
Keyword(s):  
Epithelial Cells ◽  
Rat Liver ◽  
Fetal Liver ◽  
Liver Epithelial Cells ◽  
Rat Liver Epithelial Cells ◽  
Glutamyl Transpeptidase

Doxorubicin induces EGF receptor-dependent downregulation of gap junctional intercellular communication in rat liver epithelial cells

2005 ◽  
Vol 386 (3) ◽  
pp. 217-223 ◽  
Author(s):  
Kotb Abdelmohsen ◽  
Claudia von Montfort ◽  
Dominik Stuhlmann ◽  
P. Arne Gerber ◽  
Ulrich K.M. Decking ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Rat Liver ◽  
Intercellular Communication ◽  
Connexin 43 ◽  
Egf Receptor ◽  
Gap Junctional Intercellular Communication ◽  
Erk Activation ◽  
Liver Epithelial Cells ◽  
Rat Liver Epithelial Cells ◽  
Gap Junctional

Abstract Exposure of rat liver epithelial cells to doxorubicin, an anthraquinone derivative widely employed in cancer chemotherapy, led to a dose-dependent decrease in gap junctional intercellular communication (GJC). Gap junctions are clusters of inter-cellular channels consisting of connexins, the major connexin in the cells used being connexin-43 (Cx43). Doxorubicin-induced loss of GJC was mediated by activation of extracellular signal-regulated kinase (ERK)-1 and ERK-2, as demonstrated using inhibitors of ERK activation. Furthermore, activation of the epidermal growth factor (EGF) receptor by doxorubicin was responsible for ERK activation and the subsequent attenuation of GJC. Inhibition of GJC, however, was not by direct phosphorylation of Cx43 by ERK-1/2, whereas menadione, a 1,4-naphthoquinone derivative that was previously demonstrated to activate the same EGF receptor-dependent pathway as doxorubicin, resulting in downregulation of GJC, caused strong phos-phorylation of Cx43 at serines 279 and 282. Thus, ERK-dependent downregulation of GJC upon exposure to quinones may occur both by direct phosphorylation of Cx43 and in a phosphorylation-independent manner.

scholarly journals Angiotensin II stimulates calcium-dependent activation of c-Jun N-terminal kinase.

1995 ◽  
Vol 15 (11) ◽  
pp. 6160-6168 ◽  
Author(s):  
I E Zohn ◽  
H Yu ◽  
X Li ◽  
A D Cox ◽  
H S Earp
Keyword(s):  
Epithelial Cells ◽  
Rat Liver ◽  
Ang Ii ◽  
Tetraacetic Acid ◽  
Independent Manner ◽  
Calcium Dependent ◽  
Liver Epithelial Cells ◽  
Intracellular Ca ◽  
Rat Liver Epithelial Cells ◽  
Jnk Activation

In GN4 rat liver epithelial cells, angiotensin II (Ang II) and other agonists which activate phospholipase C stimulate tyrosine kinase activity in a calcium-dependent, protein kinase C (PKC)-independent manner. Since Ang II also produces a proliferative response in these cells, we investigated downstream signaling elements traditionally linked to growth control by tyrosine kinases. First, Ang II, like epidermal growth factor (EGF), stimulated AP-1 binding activity in a PKC-independent manner. Because increases in AP-1 can reflect induction of c-Jun and c-Fos, we examined the activity of the mitogen-activated protein (MAP) kinase family members Erk-1 and -2 and the c-Jun N-terminal kinase (JNK), which are known to influence c-Jun and c-Fos transcription. Ang II stimulated MAP kinase (MAPK) activity but only approximately 50% as effectively as EGF; again, these effects were independent of PKC. Ang II also produced a 50- to 200-fold activation of JNK in a PKC-independent manner. Unlike its smaller effect on MAPK, Ang II was approximately four- to sixfold more potent in activating JNK than EGF was. Although others had reported a lack of calcium ionophore-stimulated JNK activity in lymphocytes and several other cell lines, we examined the role of calcium in GN4 cells. The following results suggest that JNK activation in rat liver epithelial cells is at least partially Ca(2+) dependent: (i) norepinephrine and vasopressin hormones that increase inositol 1,4,5-triphosphate stimulated JNK; (ii) both thapsigargin, a compound that produces an intracellular Ca(2+) signal, and Ca(2+) ionophores stimulated a dramatic increase in JNK activity (up to 200-fold); (iii) extracellular Ca(2+) chelation with ethylene glycol tetraacetic acid (EGTA) inhibited JNK activation by ionophore and intracellular chelation with 1,2-bis-(o-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid tetraacetoxymethyl-ester (BAPTA-AM) partially inhibited JNK activation by Ang II or thapsigargin; and (iv) JNK activation by Ang II was inhibited by pretreatment of cells with thapsigargin and EGTA, a procedure which depletes intracellular Ca(2+) stores. JNK activation following Ang II stimulation did not involve calmodulin; either W-7 nor calmidizolium, in concentrations sufficient to inhibit Ca(2+)/calmodulin-dependent kinase II, blocked JNK activation by Ang II. In contrast, genistein, in concentrations sufficient to inhibit Ca(2+)-dependent tyrosine phosphorylation, prevented Ang II and thapsigargin-induced JNK activation. In summary, in GN4 rat liver epithelial cells, Ang II stimulates JNK via a novel Ca(2+)-dependent pathway. The inhibition by genistein suggest that Ca(2+)-dependent tyrosine phosphorylation may modulate the JNK pathway in a cell type-specific manner, particularly in cells with a readily detectable Ca(2+)-regulated tyrosine kinase.

scholarly journals TCDD-dependent downregulation of ?-catenin in rat liver epithelial cells (WB-F344)

2002 ◽  
Vol 103 (4) ◽  
pp. 435-439 ◽  
Author(s):  
Cornelia Dietrich ◽  
Dagmar Faust ◽  
Matthias Moskwa ◽  
Anja Kunz ◽  
Karl-Walter Bock ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Rat Liver ◽  
Liver Epithelial Cells ◽  
Rat Liver Epithelial Cells
Sign in / Sign up

Export Citation Format

Share Document