scholarly journals Thyrotropin-induced mitogenesis is Ras dependent but appears to bypass the Raf-dependent cytoplasmic kinase cascade.

1995 ◽  
Vol 15 (3) ◽  
pp. 1162-1168 ◽  
Author(s):  
N al-Alawi ◽  
D W Rose ◽  
C Buckmaster ◽  
N Ahn ◽  
U Rapp ◽  
...  
Keyword(s):  
Growth Factor ◽  
Protein Kinase ◽  
Dna Synthesis ◽  
Signaling Pathways ◽  
Cellular Growth ◽  
Intracellular Camp ◽  
Thyroid Cells ◽  
Kinase Cascade ◽  
Rat Thyroid ◽  
Stimulation Of

Cellular growth control requires the coordination and integration of multiple signaling pathways which are likely to be activated concomitantly. Mitogenic signaling initiated by thyrotropin (TSH) in thyroid cells seems to require two distinct signaling pathways, a cyclic AMP (cAMP)-dependent signaling pathway and a Ras-dependent pathway. This is a paradox, since activated cAMP-dependent protein kinase disrupts Ras-dependent signaling induced by growth factors such as epidermal growth factor and platelet-derived growth factor. This inhibition may occur by preventing Raf-1 protein kinase from binding to Ras, an event thought to be necessary for the activation of Raf-1 and the subsequent activation of the mitogen-activated protein (MAP)/extracellular signal-regulated kinase (ERK) kinases (MEKs) and MAP kinase (MAPK)/ERKs. Here we report that serum-stimulated hyperphosphorylation of Raf-1 was inhibited by TSH treatment of Wistar rat thyroid cells, indicating that in this cell line, as in other cell types, increases in intracellular cAMP levels inhibit activation of downstream kinases targeted by Ras. Ras-stimulated expression of genes containing AP-1 promoter elements was similarly inhibited by TSH. On the other hand, stimulation of thyroid cells with TSH resulted in stimulation of DNA synthesis which was Ras dependent but both Raf-1 and MEK independent. We also show that Ras-stimulated DNA synthesis required the use of this kinase cascade in untreated quiescent cells but not in TSH-treated cells. These data suggest that in TSH-treated thyroid cells, Ras might be able to signal through effectors other than the well-studied cytoplasmic kinase cascade.

scholarly journals Insulin and TSH promote growth in size of PC Cl3 rat thyroid cells, possibly via a pathway different from DNA synthesis: comparison with FRTL-5 cells

1999 ◽  
pp. 94-103 ◽  
Author(s):  
T Kimura ◽  
JE Dumont ◽  
A Fusco ◽  
J Golstein
Keyword(s):  
Protein Synthesis ◽  
Dna Replication ◽  
Dna Synthesis ◽  
Cell Lines ◽  
Insulin Action ◽  
Cell Mass ◽  
Thyroid Cell ◽  
Thyroid Cells ◽  
Rat Thyroid ◽  
Stimulation Of

In the rat thyroid cell lines PC Cl3, FRTL- 5 and WRT, proliferation is mainly regulated by insulin or IGF, and TSH. However, the mechanism regulating cell mass doubling prior to division is still unknown. Our laboratory has shown that in dog thyroid cells insulin promotes growth in size while TSH in the presence of insulin triggers DNA replication. In the absence of insulin, TSH has no effect on cell growth. In this report we investigated insulin action on both cell mass and DNA synthesis and its modulation by TSH and insulin in PC Cl3 and FRTL-5 cells. In PC Cl3 cells, insulin activated not only DNA synthesis but also protein synthesis and accumulation. Although TSH potentiated the stimulation of DNA synthesis induced by insulin, enhancement of protein synthesis by both agents was additive. All TSH effects were reproduced by forskolin. Similar effects were also obtained in FRTL-5 cells. This suggests that insulin and TSH, via cAMP, modulate both growth in size and DNA replication in these cell lines. Lovastatin, which blocks 3-hydroxy-3-methylglutaryl coenzyme A reductase, decreased the induction of DNA synthesis, but not of protein synthesis induced by insulin or TSH in PC Cl3 cells. In FRTL-5 cells, lovastatin reduced protein and DNA synthesis stimulated by insulin but not TSH-induced protein synthesis. Taking these data together, we propose that insulin and/or TSH both modulate cell mass doubling and DNA synthesis in these cell lines, presumably via different pathways, and that there are at least two pathways which regulate growth in size in FRTL-5 thyroid cells: one triggered by insulin, which is lovastatin sensitive, and the other activated by TSH, which is not sensitive to lovastatin.

Genistein but not staurosporine can inhibit the mitogenic signal evoked by lithium in rat thyroid cells (FRTL-5)

1994 ◽  
Vol 143 (2) ◽  
pp. 221-226 ◽  
Author(s):  
T Takano ◽  
K Takada ◽  
H Tada ◽  
S Nishiyama ◽  
N Amino
Keyword(s):  
Signal Transduction ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Tyrosine Kinase ◽  
Dna Synthesis ◽  
Thyroid Cells ◽  
Kinase C ◽  
Mitogenic Signal Transduction ◽  
Rat Thyroid ◽  
Mitogenic Signal

Abstract Long-term administration of lithium is one of the well-known causes of goiter. It can stimulate DNA synthesis in rat thyroid cells (FRTL-5) treated with thyroid-stimulating hormone (TSH). To investigate the mitogenic signal transduction system activated by lithium, lithium-induced DNA synthesis and Ca2+ influx were studied using two protein kinase inhibitors, genistein as a specific tyrosine kinase inhibitor and staurosporine as a potent inhibitor of protein kinase C. Genistein but not staurosporine blocked the DNA synthesis induced by lithium in TSH-primed cells but neither compound had any effect on the Ca2+ entry stimulated by lithium. Genistein clearly attenuated the phosphotyrosine content of the 175 kDa substrate in the presence of lithium but staurosporine failed to do so. Moreover, lithium could also stimulate DNA synthesis in protein kinase C down-regulated cells. These data demonstrate that lithium may require the activation of a particular genistein-sensitive kinase, possibly a tyrosine kinase, to induce cell proliferation. It is suggested that the phorbol ester-sensitive protein kinase C family might not participate in the mitogenic signal transduction pathway activated by lithium. Journal of Endocrinology (1994) 143, 221–226

scholarly journals Phosphatidylinositol 3-kinase, protein kinase B and ribosomal S6 kinases in the stimulation of thyroid epithelial cell proliferation by cAMP and growth factors in the presence of insulin

2000 ◽  
Vol 348 (2) ◽  
pp. 351-358 ◽  
Author(s):  
Katia COULONVAL ◽  
Fabrice VANDEPUT ◽  
Rob C. STEIN ◽  
Sara C. KOZMA ◽  
Françoise LAMY ◽  
...  
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Protein Kinase ◽  
Dna Synthesis ◽  
Protein Kinase B ◽  
Phosphatidylinositol 3 Kinase ◽  
S6 Kinase ◽  
P70 S6 Kinase ◽  
Stimulation Of ◽  
Phosphatidylinositol 3

The proliferation of most normal cells depends on the co-operation of several growth factors and hormones, each with a specific role, but the key events involved in the action of each necessary stimulant remain largely uncharacterized. In the present study, the pathways involved in the mechanism(s) of co-operation have been investigated in primary cultures of dog thyroid epithelial cells. In this physiologically relevant system, thyroid stimulating hormone (TSH) acting through cAMP, epidermal growth factor (EGF) and phorbol esters (such as PMA) induce DNA synthesis. Their effect requires stimulation of the insulin-like growth factor-1 (IGF-1) receptor by either IGF-1 or insulin, which are not themselves mitogenic agents. In contrast, hepatocyte growth factor (HGF) is itself fully mitogenic. The results of the study demonstrate that cAMP, EGF, HGF and PMA stimulate p70 ribosomal S6 kinase (p70 S6 kinase). However, insulin/IGF-1 also stimulate p70 S6 kinase. Thus stimulation of p70 S6 kinase might be necessary, but is certainly not sufficient, for the induction of DNA synthesis and is not specific for any stimulated pathway. In contrast, phosphatidylinositol 3-kinase (PI 3-kinase) and protein kinase B (PKB) activation by insulin and HGF is strong and sustained, whereas it is weak and transient with EGF and absent in the presence of TSH or PMA. These findings suggest that: (i) stimulation of PI 3-kinases and/or PKB is not involved in the cAMP-dependent pathways leading to thyrocyte proliferation, or in the action of PMA, (ii) the stimulation of the PI 3-kinase/PKB pathway may account for the permissive action of insulin/IGF-1 in the proliferation of these cells, and (iii) the stimulation of this pathway by HGF may explain why this agent does not require insulin or IGF-1 for its mitogenic action.

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 Inhibition of thyrotropin-stimulated DNA synthesis by microinjection of inhibitors of cellular Ras and cyclic AMP-dependent protein kinase

1993 ◽  
Vol 13 (8) ◽  
pp. 4477-4484
Author(s):  
E Kupperman ◽  
W Wen ◽  
J L Meinkoth
Keyword(s):  
Protein Kinase ◽  
Cyclic Amp ◽  
Dna Synthesis ◽  
Kinase Inhibitor ◽  
Dependent Protein Kinase ◽  
Thyroid Cells ◽  
Heat Stable ◽  
Heat Stable Protein ◽  
Dependent Protein ◽  
Rat Thyroid

Microinjection of a dominant interfering mutant of Ras (N17 Ras) caused a significant reduction in thyrotropin (thyroid-stimulating hormone [TSH])-stimulated DNA synthesis in rat thyroid cells. A similar reduction was observed following injection of the heat-stable protein kinase inhibitor of the cyclic AMP-dependent protein kinase. Coinjection of both inhibitors almost completely abolished TSH-induced DNA synthesis. In contrast to TSH, overexpression of cellular Ras protein did not stimulate the expression of a cyclic AMP response element-regulated reporter gene. Similarly, injection of N17 Ras had no effect on TSH-stimulated reporter gene expression. Moreover, overexpression of cellular Ras protein stimulated similar levels of DNA synthesis in the presence or absence of the heat-stable protein kinase inhibitor. Together, these results suggest that in Wistar rat thyroid cells, a full mitogenic response to TSH requires both Ras and cyclic APK-dependent protein kinase.

Heparin affects signaling pathways stimulated by fibroblast growth factor-1 and -2 in type II cells

2004 ◽  
Vol 287 (1) ◽  
pp. L191-L200 ◽  
Author(s):  
Donna R. Newman ◽  
Cheng-Ming Li ◽  
Rebecca Simmons ◽  
Jody Khosla ◽  
Philip L. Sannes
Keyword(s):  
Growth Factor ◽  
Protein Kinase ◽  
Basement Membrane ◽  
Dna Synthesis ◽  
Signaling Pathways ◽  
Fibroblast Growth Factor ◽  
Type Ii ◽  
Fibroblast Growth ◽  
End Points ◽  
Mitogen Activated Protein

Undersulfation of the basement membrane matrix of alveolar type II (AT2) cells compared with that of neighboring type I cells is believed to account for some of the known morphological and functional differences between these pneumocytes. Heparin, a model for sulfated components of basement membrane matrices, is known to inhibit fibroblast growth factor (FGF)-2-stimulated DNA synthesis as well as gene expression of FGF-2 and its receptor in AT2 cells. To determine whether these end points result from specific effects of heparin on FGF-related signaling pathways, isolated rat AT2 cells were treated with 100 ng/ml FGF-1 or FGF-2 in the presence of up to 500 μg/ml heparin. In addition, experiments were done on cells grown in the presence of 20 mM sodium chlorate (sulfation inhibitor). High-dose heparin reduced FGF-1- or FGF-2-stimulated phosphorylation of mitogen-activated protein kinase kinases (MEK1/2), p44/42 mitogen-activated protein kinases (MAPK/ERK1/2), stress-activated protein kinase/c-Jun NH2-terminal kinase, Akt/protein kinase B, and p90RSK. FGF-2-stimulated signaling was more sensitive to heparin's effects than was signaling stimulated by FGF-1. Heparin had an additive effect on the reduced [3H]thymidine incorporation in FGF-2-treated AT2 cells caused by inhibition of the MEK/ERK pathway by the MEK inhibitor PD-98059. The data suggest that heparin's known capacity to alter DNA synthesis and, possibly, other biological end points is realized via cross talk between multiple signaling pathways.

scholarly journals Mitogenic signaling pathways of growth factors can be distinguished by the involvement of pertussis toxin-sensitive guanosine triphosphate-binding protein and of protein kinase C.

1990 ◽  
Vol 1 (10) ◽  
pp. 747-761 ◽  
Author(s):  
N Nishizawa ◽  
Y Okano ◽  
Y Chatani ◽  
F Amano ◽  
E Tanaka ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Protein Kinase C ◽  
Growth Factors ◽  
Growth Factor ◽  
Protein Kinase ◽  
Dna Synthesis ◽  
Signaling Pathways ◽  
Pertussis Toxin ◽  
Guanosine Triphosphate ◽  
Kinase C

We have examined the possible involvements of pertussis toxin (PT)-sensitive guanosine triphosphate (GTP)-binding protein (Gp) and protein kinase C (PKC) in the mitogenic signaling pathways of various growth factors by the use of PT-pretreated and/or 12-O-tetradecanoyl phorbol-13-acetate (TPA)-pretreated mouse fibroblasts. Effects of PT pretreatment (inactivation of PT-sensitive Gp) and TPA pretreatment (depletion of PKC) on mitogen-induced DNA synthesis varied significantly and systematically in response to growth factors: mitogenic responses of cells to thrombin, bombesin, and bradykinin were almost completely abolished both in PT- and TPA-pretreated cells; responses to epidermal growth factor (EGF), platelet-derived growth factor (PDGF), and vanadate were reduced to approximately 50% both in PT- and TPA-pretreated cells compared with native cells; response to basic fibroblast growth factor (bFGF) was not affected in PT-pretreated cells but was inhibited to some extent in TPA-pretreated cells. Thus, growth factors examined have been classified into three groups with regard to the involvements of PT-sensitive Gp and PKC in their signal transduction pathways. Binding of each growth factor to its receptor was not affected significantly by pretreatment of cells with PT or TPA. Inhibitory effects of PT and TPA pretreatment on each mitogen-induced DNA synthesis were not additive, suggesting that the functions of PT-sensitive Gp and PKC lie on an identical signal transduction pathway. Although all three groups of mitogens activated PKC, signaling of each growth factor depends to a varying extent on the function of PKC. Our results indicate that a single peptide growth factor such as EGF, PDGF, or bFGF acts through multiple signaling pathways to induce cell proliferation.

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