Cholecystokinin and EGF activate a MAPK cascade by different mechanisms in rat pancreatic acinar cells

1997 ◽  
Vol 273 (5) ◽  
pp. C1472-C1479 ◽  
Author(s):  
Andrzej Dabrowski ◽  
Guy E. Groblewski ◽  
Claus Schäfer ◽  
Kun-Liang Guan ◽  
John A. Williams
Keyword(s):  
Protein Kinase ◽  
Phorbol Ester ◽  
Egf Receptor ◽  
Acinar Cells ◽  
Mapk Cascade ◽  
Mitogen Activated Protein Kinase ◽  
Pancreatic Acinar Cells ◽  
Mapk Activity ◽  
Gf 109203X ◽  
High Level

The effects of activating the Gqprotein-coupled cholecystokinin (CCK) receptor on different proteins/signaling molecules in the mitogen-activated protein kinase (MAPK) cascade in pancreatic acinar cells were analyzed and compared with the effects of activating the tyrosine kinase-coupled epidermal growth factor (EGF) receptor. Both EGF and CCK octapeptide rapidly increased the activity of the MAPKs [extracellular signal-regulated kinase (ERK) 1 and ERK2], reaching a maximum within 2.5 min when 3.9- and 8.5-fold increases, respectively, were observed. The EGF-induced increase of MAPK activity was transient, with only a slight elevation after 30 min, whereas CCK-stimulated MAPK remained at a high level of activation to 60 min. The protein kinase C inhibitor GF-109203X abolished the activation by phorbol ester and inhibited the effect of CCK by 78% but had no effect on EGF-activated MAPK activity. EGF and CCK activated both forms of MAPK kinase (MEK), with CCK having a much larger effect, activating MEK1 by 6-fold and MEK2 by 10-fold, whereas EGF activated both MEKs by only 2-fold. Immunoblotting revealed three different forms of Raf in pancreatic acinar cells. Of the total basal Raf kinase activity, 3.7% was Raf-A, 89.0% was Raf-B, and 7.3% was c-Raf-1. All three forms of Raf were stimulated to a greater extent by CCK than by EGF, which was especially evident for Raf-A and c-Raf-1. The effect of CCK in activating Rafs was at least partially mimicked by stimulation with the phorbol ester 12- O-tetradecanoylphorbol-13-acetate. EGF significantly increased GTP-bound Ras by 183 and 164% at 2.5 and 10 min, respectively; CCK and TPA had no measurable effect. Our study suggests that CCK and EGF activate the MAPK cascade by distinct mechanisms in pancreatic acinar cells.

scholarly journals Activation of B-Raf and Regulation of the Mitogen-activated Protein Kinase Pathway by the Go α chain

2000 ◽  
Vol 11 (4) ◽  
pp. 1129-1142 ◽  
Author(s):  
Valeria Antonelli ◽  
Francesca Bernasconi ◽  
Yung H. Wong ◽  
Lucia Vallar
Keyword(s):  
Protein Kinase ◽  
Egf Receptor ◽  
Mapk Pathway ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Mitogen Activated Protein Kinase ◽  
Phosphatidylinositol 3 Kinase ◽  
Ovary Cells ◽  
Mapk Activity ◽  
Mitogen Activated Protein

Many receptors coupled to the pertussis toxin-sensitive Gi/o proteins stimulate the mitogen-activated protein kinase (MAPK) pathway. The role of the α chains of these G proteins in MAPK activation is poorly understood. We investigated the ability of Gαo to regulate MAPK activity by transient expression of the activated mutant Gαo-Q205L in Chinese hamster ovary cells. Gαo-Q205L was not sufficient to activate MAPK but greatly enhanced the response to the epidermal growth factor (EGF) receptor. This effect was not associated with changes in the state of tyrosine phosphorylation of the EGF receptor. Gαo-Q205L also potentiated MAPK stimulation by activated Ras. In Chinese hamster ovary cells, EGF receptors activate B-Raf but not Raf-1 or A-Raf. We found that expression of activated Gαo stimulated B-Raf activity independently of the activation of the EGF receptor or Ras. Inactivation of protein kinase C and inhibition of phosphatidylinositol-3 kinase abolished both B-Raf activation and EGF receptor-dependent MAPK stimulation by Gαo. Moreover, Gαo-Q205L failed to affect MAPK activation by fibroblast growth factor receptors, which stimulate Raf-1 and A-Raf but not B-Raf activity. These results suggest that Gαo can regulate the MAPK pathway by activating B-Raf through a mechanism that requires a concomitant signal from tyrosine kinase receptors or Ras to efficiently stimulate MAPK activity. Further experiments showed that receptor-mediated activation of Gαo caused a B-Raf response similar to that observed after expression of the mutant subunit. The finding that Gαo induces Ras-independent and protein kinase C- and phosphatidylinositol-3 kinase-dependent activation of B-Raf and conditionally stimulates MAPK activity provides direct evidence for intracellular signals connecting this G protein subunit to the MAPK pathway.

scholarly journals Interleukin-6 Inhibits Fas-Induced Apoptosis and Stress-Activated Protein Kinase Activation in Multiple Myeloma Cells

Blood ◽  
1997 ◽  
Vol 89 (1) ◽  
pp. 227-234 ◽  
Author(s):  
Dharminder Chauhan ◽  
Surender Kharbanda ◽  
Atsushi Ogata ◽  
Mitsuyoshi Urashima ◽  
Gerrard Teoh ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Protein Kinase ◽  
Dna Fragmentation ◽  
P38 Mapk ◽  
Interleukin 6 ◽  
Early Response ◽  
Mitogen Activated Protein Kinase ◽  
Serum Starvation ◽  
Mapk Activity ◽  
Induced Apoptosis

Abstract Fas belongs to the family of type-1 membrane proteins that transduce apoptotic signals. In the present studies, we characterized signaling during Fas-induced apoptosis in RPMI-8226 and IM-9 multiple myeloma (MM) derived cell lines as well as patient plasma cell leukemia cells. Treatment with anti-Fas (7C11) monoclonal antibody (MoAb) induced apoptosis, evidenced by internucleosomal DNA fragmentation and propidium iodide staining, and was associated with increased expression of c-jun early response gene. We also show that anti-Fas MoAb treatment is associated with activation of stress-activated protein kinase (SAPK) and p38 mitogen-activated protein kinase (MAPK); however, no detectable increase in extracellular signal-regulated kinases (ERK1 and ERK2) activity was observed. Because interleukin-6 (IL-6) is a growth factor for MM cells and inhibits apoptosis induced by dexamethasone and serum starvation, we examined whether IL-6 affects anti-Fas MoAb-induced apoptosis and activation of SAPK or p38 MAPK in MM cells. Culture of MM cells with IL-6 before treatment with anti-Fas MoAb significantly reduced both DNA fragmentation and activation of SAPK, without altering induction of p38 MAPK activity. These results therefore suggest that anti-Fas MoAb-induced apoptosis in MM cells is associated with activation of SAPK, and that IL-6 may both inhibit apoptosis and modulate SAPK activity.

Endothelins stimulate mitogen-activated protein kinase cascade through either ETA or ETB

1994 ◽  
Vol 267 (4) ◽  
pp. C1130-C1135 ◽  
Author(s):  
Y. Wang ◽  
P. M. Rose ◽  
M. L. Webb ◽  
M. J. Dunn
Keyword(s):  
Protein Kinase ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Mapk Cascade ◽  
Mitogen Activated Protein Kinase ◽  
Thymidine Uptake ◽  
Mapk Activation ◽  
Transfected Cells ◽  
Gel Retardation ◽  
Mitogen Activated Protein

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.

Role of the PI3K/PKB signaling pathway in cAMP-mediated translocation of rat liver Ntcp

1999 ◽  
Vol 277 (6) ◽  
pp. G1165-G1172 ◽  
Author(s):  
Cynthia R. L. Webster ◽  
M. Sawkat Anwer
Keyword(s):  
Plasma Membrane ◽  
Protein Kinase ◽  
Signaling Pathway ◽  
Mitogen Activated Protein Kinase ◽  
Phosphatidylinositol 3 Kinase ◽  
Pi3k Inhibitors ◽  
Mapk Activity ◽  
Mitogen Activated Protein ◽  
Pi3k Signaling Pathway ◽  
Stimulation Of

cAMP stimulates Na+-taurocholate (TC) cotransport by translocating the Na+-TC-cotransporting peptide (Ntcp) to the plasma membrane. The present study was undertaken to determine whether the phosphatidylinositol-3-kinase (PI3K)-signaling pathway is involved in cAMP-mediated translocation of Ntcp. The ability of cAMP to stimulate TC uptake declined significantly when hepatocytes were pretreated with PI3K inhibitors wortmannin or LY-294002. Wortmannin inhibited cAMP-mediated translocation of Ntcp to the plasma membrane. cAMP stimulated protein kinase B (PKB) activity by twofold within 5 min, an effect inhibited by wortmannin. Neither basal mitogen-activated protein kinase (MAPK) activity nor cAMP-mediated inhibition of MAPK activity was affected by wortmannin. cAMP also stimulated p70S6K activity. However, rapamycin, an inhibitor of p70S6K, failed to inhibit cAMP-mediated stimulation of TC uptake, indicating that the effect of cAMP is not mediated via p70S6K. Cytochalasin D, an inhibitor of actin filament formation, inhibited the ability of cAMP to stimulate TC uptake and Ntcp translocation. Together, these results suggest that the stimulation of TC uptake and Ntcp translocation by cAMP may be mediated via the PI3K/PKB signaling pathway and requires intact actin filaments.

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