Insulin induces Ca2+ influx into isolated rat hepatocyte couplets

1997 ◽  
Vol 272 (6) ◽  
pp. G1425-G1432 ◽  
Author(s):  
K. Benzeroual ◽  
G. van de Werve ◽  
S. Meloche ◽  
L. Mathe ◽  
A. Romanelli ◽  
...  
Keyword(s):  
Peptide Hormone ◽  
Insulin Binding ◽  
Mitogen Activated Protein Kinase ◽  
Rat Hepatocyte ◽  
Mapk Activity ◽  
Mitogen Activated Protein ◽  
Insulin Dependent ◽  
Dose Dependent Increase ◽  
Isolated Rat ◽  
Stimulation Of

Isolated rat hepatocyte couplets were used to study the direct effect of insulin on intracellular Ca2+ homeostasis. Insulin induced a dose-dependent increase in hepatocellular Ca2+ that was gradual, generally monophasic, and reversible. Chelation of extracellular Ca2+ abolished the insulin-induced Ca2+ response, and this suppression was not related to an effect on insulin binding, as indicated by displacement studies. We thus tested the effect of several Ca2+ channel inhibitors on insulin-induced Ca2+ influx. Verapamil at 20 or 200 microM was without effect, whereas 500 microM nickel and 50 microM gadolinium strongly inhibited insulin-induced Ca2+ entry. Finally, we tested whether insulin-induced Ca2+ movements were implicated in the stimulation of mitogen-activated protein kinase (MAPK) activity, which we measured with the use of an immune-complex assay. Verapamil was without effect on the insulin-dependent stimulation of p44mapk activity, whereas addition of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, nickel, or gadolinium strongly inhibited the effect of the peptide hormone. Our results indicate that insulin triggers Ca2+ influx into hepatocytes, possibly through the opening of channels on the plasma membrane, and that this effect is important for insulin activation of MAPK.

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.

Chinese Medicine Induces Neurite Outgrowth in PC12 Mutant Cells Incapable of Differentiation

2002 ◽  
Vol 30 (02n03) ◽  
pp. 287-295 ◽  
Author(s):  
Yoshio Kano ◽  
Shinichiro Takaguchi ◽  
Tsutomu Nohno ◽  
Fukumi Hiragami ◽  
Kenji Kawamura ◽  
...  
Keyword(s):  
Neurite Outgrowth ◽  
Pc12 Cells ◽  
Mutant Cell ◽  
Mitogen Activated Protein Kinase ◽  
Chinese Medicines ◽  
Mapk Activity ◽  
Mitogen Activated Protein ◽  
Mutant Cells ◽  
Stimulation Of ◽  
Sustained Activation

During continuous culture of neural PC12 cells, we obtained a drug-hypersensitive PC12 mutant cell that showed high stimulation of neurite outgrowth by various drugs. When several Chinese medicines such as Shu-Jing-Huo-Xie-Tang and Wu-Ling-San were provided to these PC12 mutant cells, the frequency of nerve growth factor (NGF)-induced neurite outgrowth increased approximately 30-fold compared to NGF alone. Neurite outgrowth induced by NGF in PC12 cells is accompanied by sustained activation of mitogen-activated protein kinase (MAPK); however, these Chinese medicines did not induce MAPK activity. The findings thus indicate that certain Chinese medicines may induce neurite outgrowth by a novel mechanism which is distinct from the NGF-activated pathway in PC12 mutant cells.

scholarly journals Insulin-Activated Protein Kinase Cβ Bypasses Ras and Stimulates Mitogen-Activated Protein Kinase Activity and Cell Proliferation in Muscle Cells

2000 ◽  
Vol 20 (17) ◽  
pp. 6323-6333 ◽  
Author(s):  
Pietro Formisano ◽  
Francesco Oriente ◽  
Francesca Fiory ◽  
Matilde Caruso ◽  
Claudia Miele ◽  
...  
Keyword(s):  
Growth Factor ◽  
Protein Kinase ◽  
Dna Synthesis ◽  
Antisense Oligonucleotide ◽  
Kinase Activity ◽  
Mitogen Activated Protein Kinase ◽  
Insulin Stimulation ◽  
Mapk Activity ◽  
Mitogen Activated Protein ◽  
Stimulation Of

ABSTRACT In L6 muscle cells expressing wild-type human insulin receptors (L6hIR), insulin induced protein kinase Cα (PKCα) and β activities. The expression of kinase-deficient IR mutants abolished insulin stimulation of these PKC isoforms, indicating that receptor kinase is necessary for PKC activation by insulin. In L6hIR cells, inhibition of insulin receptor substrate 1 (IRS-1) expression caused a 90% decrease in insulin-induced PKCα and -β activation and blocked insulin stimulation of mitogen-activated protein kinase (MAPK) and DNA synthesis. Blocking PKCβ with either antisense oligonucleotide or the specific inhibitor LY379196 decreased the effects of insulin on MAPK activity and DNA synthesis by >80% but did not affect epidermal growth factor (EGF)- and serum-stimulated mitogenesis. In contrast, blocking c-Ras with lovastatin or the use of the L61,S186 dominant negative Ras mutant inhibited insulin-stimulated MAPK activity and DNA synthesis by only about 30% but completely blocked the effect of EGF. PKCβ block did not affect Ras activity but almost completely inhibited insulin-induced Raf kinase activation and coprecipitation with PKCβ. Finally, blocking PKCα expression by antisense oligonucleotide constitutively increased MAPK activity and DNA synthesis, with little effect on their insulin sensitivity. We make the following conclusions. (i) The tyrosine kinase activity of the IR is necessary for insulin activation of PKCα and -β. (ii) IRS-1 phosphorylation is necessary for insulin activation of these PKCs in the L6 cells. (iii) In these cells, PKCβ plays a unique Ras-independent role in mediating insulin but not EGF or other growth factor mitogenic signals.

scholarly journals Fever-like temperature modification differentially affects in vitro signaling of bradykinin B1 and B2 receptors

2011 ◽  
Vol 392 (11) ◽  
Author(s):  
Jasmin Leschner ◽  
Larisa Ring ◽  
Jens Feierler ◽  
Klaus Dinkel ◽  
Marianne Jochum ◽  
...  
Keyword(s):  
Mapk Signaling ◽  
Mitogen Activated Protein Kinase ◽  
Temperature Sensitive ◽  
Hek 293 ◽  
Mapk Activity ◽  
Mitogen Activated Protein ◽  
Surface Receptor ◽  
B2 Receptors ◽  
Stimulation Of

Abstract The bradykinin (BK) B2 and B1 receptors (B2R, B1R) belong to the rhodopsin-like G protein-coupled receptors (GPCRs) and are involved in (patho)physiological processes such as blood pressure regulation or inflammation. They mediate the effects of the pro-inflammatory peptides bradykinin/kallidin and desArg9-BK/desArg10-kallidin, respectively. Whereas the B2R is constitutively expressed and gets internalized upon activation, the B1R is especially induced by inflammatory mediators and responds to stimulation with increased surface receptor numbers. Stimulation of both receptors activates phospholipase Cβ (PLCβ) and mitogen activated protein kinase (MAPK) signaling. Because inflammatory processes are characterized by heat (fever), we analyzed the effect of increased temperature (41°C vs. 37°C) on B1R and B2R signaling in HEK 293 and IMR 90 cells. Our results show that signaling of both receptors is temperature-sensitive, however to a different extent and with regard to the investigated pathways. Comparing PLCβ activity and Ca2+-regulated signals, a temperature-dependent increase was only observed for B1R but not for B2R activation, whereas MAPK activities were doubled at 41°C for both receptors. Taken together, our findings suggest that the observed temperature sensitivity of B1R-induced PLCβ activation is B1R-specific. In contrast, the enhanced stimulation of MAPK activity under hyperthermic conditions appears to be a common phenomenon for GPCRs.

scholarly journals Signals from the AT2 (Angiotensin Type 2) Receptor of Angiotensin II Inhibit p21ras and Activate MAPK (Mitogen-Activated Protein Kinase) to Induce Morphological Neuronal Differentiation in NG108–15 Cells

1999 ◽  
Vol 13 (9) ◽  
pp. 1615-1626 ◽  
Author(s):  
Louis Gendron∗ ◽  
Liette Laflamme∗ ◽  
Nathalie Rivard ◽  
Claude Asselin ◽  
Marcel D. Payet ◽  
...  
Keyword(s):  
Neurite Outgrowth ◽  
Morphological Differentiation ◽  
Mitogen Activated Protein Kinase ◽  
Ang Ii ◽  
Mapk Activity ◽  
Angiotensin Type 2 Receptor ◽  
Mitogen Activated Protein ◽  
Angiotensin Type ◽  
Stimulation Of

Abstract In a previous study, we had shown that activation of the AT2 (angiotensin type 2) receptor of angiotensin II (Ang II) induced morphological differentiation of the neuronal cell line NG108–15. In the present study, we investigated the nature of the possible intracellular mediators involved in the AT2 effect. We found that stimulation of AT2 receptors in NG108–15 cells resulted in time-dependent modulation of tyrosine phosphorylation of a number of cytoplasmic proteins. Stimulation of NG108–15 cells with Ang II induced a decrease in GTP-bound p21ras but a sustained increase in the activity of p42mapk and p44mapk as well as neurite outgrowth. Similarly, neurite elongation, increased polymerized tubulin levels, and increased mitogen-activated protein kinase (MAPK) activity were also observed in a stably transfected NG108–15 cell line expressing the dominant-negative mutant of p21ras, RasN17. These results support the observation that inhibition of p21ras did not impair the effect of Ang II on its ability to stimulate MAPK activity. While 10 μm of the MEK inhibitor, PD98059, only moderately affected elongation, 50 μm PD98059 completely blocked the Ang II- and the RasN17-mediated induction of neurite outgrowth. These results demonstrate that some of the events associated with the AT2 receptor-induced neuronal morphological differentiation of NG108–15 cells not only include inhibition of p21ras but an increase in MAPK activity as well, which is essential for neurite outgrowth.

scholarly journals Differential calcium dependence in the activation of c-Jun kinase and mitogen-activated protein kinase by muscarinic acetylcholine receptors in rat 1a cells

1995 ◽  
Vol 309 (2) ◽  
pp. 381-384 ◽  
Author(s):  
F M Mitchell ◽  
M Russell ◽  
G L Johnson
Keyword(s):  
Protein Kinase ◽  
Acetylcholine Receptors ◽  
Muscarinic Acetylcholine Receptors ◽  
Mitogen Activated Protein Kinase ◽  
Muscarinic Acetylcholine ◽  
Calcium Dependent ◽  
Jun Kinase ◽  
Mapk Activity ◽  
Mitogen Activated Protein ◽  
Stimulation Of

Carbachol stimulation of the muscarinic acetylcholine m1 receptor (m1R), stably expressed in Rat 1a fibroblasts, resulted in a calcium-dependent activation of c-Jun kinase (JNK). Stimulation of the muscarinic acetylcholine m2 receptor (m2R), stably expressed in Rat 1a fibroblasts, resulted in a G1-mediated activation of JNK that was weak relative to that observed with the m1R. Chelation of calcium inhibited the m2R-mediated activation of JNK but not the robust m2R stimulation of mitogen-activated protein kinase (MAPK) activity. These findings demonstrate a role for the second messenger, calcium, in the differential regulation of the activity of JNK and MAPK in Rat 1a cells.

scholarly journals Cross Talk between β-Adrenergic and Bradykinin B2Receptors Results in Cooperative Regulation of Cyclic AMP Accumulation and Mitogen-Activated Protein Kinase Activity

2001 ◽  
Vol 21 (24) ◽  
pp. 8452-8460 ◽  
Author(s):  
Sabine Hanke ◽  
Bernd Nürnberg ◽  
Detlef H. Groll ◽  
Claus Liebmann
Keyword(s):  
Protein Kinase ◽  
Cyclic Amp ◽  
Cross Talk ◽  
Mitogen Activated Protein Kinase ◽  
Protein Kinase Activity ◽  
Downstream Signaling ◽  
Mapk Activity ◽  
Cyclic Amp Accumulation ◽  
Mitogen Activated Protein ◽  
Stimulation Of

ABSTRACT Costimulation of G protein-coupled receptors (GPCRs) may result in cross talk interactions between their downstream signaling pathways. Stimulation of GPCRs may also lead to cross talk regulation of receptor tyrosine kinase signaling and thereby to activation of mitogen-activated protein kinase (MAPK). In COS-7 cells, we investigated the interactions between two particular mitogenic receptor pathways, the endogenously expressed β-adrenergic receptor (β-AR) and the transiently transfected human bradykinin (BK) B2receptor (B2R). When β-AR and B2R are costimulated, we found two different cross talk mechanisms. First, the predominantly Gq protein-coupled B2R is enabled to activate a Gi protein and, subsequently, type II adenylate cyclase. This results in augmentation of β-AR-mediated cyclic AMP (cAMP) accumulation by BK, which alone is unable to increase the cAMP level. Second, independently of BK-induced superactivation of the cAMP system, costimulation of β-AR leads to protein kinase A-mediated blockade of phospholipase C activation by BK. Thereby, the pathway from B2R to MAPK, which essentially involves protein kinase C activation, is selectively switched off. The MAPK activation in response to isoproterenol was not affected due to costimulation. Furthermore, in the presence of isoproterenol, BK lost its ability to stimulate DNA synthesis in COS-7 cells. Thus, our findings might establish a novel paradigm: cooperation between simultaneously activated mitogenic pathways may prevent multiple stimulation of MAPK activity and increased cell growth.

scholarly journals Somatostatin stimulates intestinal NHE8 expression via p38 MAPK pathway

2011 ◽  
Vol 300 (2) ◽  
pp. C375-C382 ◽  
Author(s):  
Chunhui Wang ◽  
Hua Xu ◽  
Huacong Chen ◽  
Jing Li ◽  
Bo Zhang ◽  
...  
Keyword(s):  
P38 Mapk ◽  
Mapk Pathway ◽  
Somatostatin Receptor ◽  
Peptide Hormone ◽  
Mitogen Activated Protein Kinase ◽  
Mapk Phosphorylation ◽  
P38 Mapk Pathway ◽  
Mitogen Activated Protein ◽  
D Cells ◽  
Human Intestinal Cells

Diarrhea is a common manifestation of gastrointestinal disorders. Diarrhea-induced losses of fluid and electrolyte could lead to dehydration and electrolyte imbalances, resulting in significant morbidity and mortality, especially in children living in developing countries. Somatostatin, a peptide hormone secreted by D-cells, plays an important role in regulating motility and intestinal Na+ absorption. Although octreotide, a somatostatin analog, is used to treat diarrhea, its mechanisms of action are unclear. Here we showed that octreotide increased brush-border membrane Na+/H+ exchanger 8 (NHE8) expression in the small intestine to the exclusion of other NHEs that participate in Na+ absorption. The same effect also occurred in human intestinal cells (Caco-2). We found that the increase of NHE8 expression by somatostatin required p38 mitogen-activated protein kinase (MAPK) activation. Furthermore, the somatostatin receptor SSTR2 antagonist CYN154806 could abolish somatostatin-induced NHE8 expression and p38 MAPK phosphorylation. Thus our data provided the first concrete evidence indicating that somatostatin stimulates intestinal Na+ absorption by increasing intestinal NHE8 expression through the SSTR2-p38 MAPK pathway.

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