Overexpression of RHO Inhibitor and PAK as Possible Treatments For Restoring Sharp Features in Cancer Cells

2001 ◽  
Vol 7 (S2) ◽  
pp. 576-577
Author(s):  
Heckman C. A. ◽  
Urban J. M. ◽  
Wales T. S. ◽  
Cayer M. L. ◽  
Barnes J. A. ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Cancer Cells ◽  
Mechanism Of Action ◽  
Tumor Promoter ◽  
Shape Features ◽  
Cell Edge ◽  
Kinase C ◽  
Bona Fide ◽  
Rho Family

The mechanism of action of the tumor promoter, phorbol 12-myristate 13-acetate (PMA), depends on its ability to substitute for an endogenous second messenger, diacylglycerol, and thereby activate certain members of an enzyme family known as protein kinase C. Previous work from this laboratory showed that the quantitative shape phenotype of cells treated with PMA resembled the phenotype of bona fidecancer cells. The effect of PMA on this phenotype was transient, and was restricted to a period of two- to five-hours after exposure to PMA. When the shape phenotype was dissected into components by relating different variable's values to shape features, several of the altered values appeared to rely upon a declining number of sharp features, such as filopodia and microspikes, at the cell edge.Filopodia and microspikes are in turn regulated by a GTPase of the Rho family, Cdc42, which modulates actin architecture.

scholarly journals Regulated CD44 Cleavage under the Control of Protein Kinase C, Calcium Influx, and the Rho Family of Small G Proteins

1999 ◽  
Vol 274 (36) ◽  
pp. 25525-25534 ◽  
Author(s):  
Isamu Okamoto ◽  
Yoshiaki Kawano ◽  
Mitsuhiro Matsumoto ◽  
Moritaka Suga ◽  
Kozo Kaibuchi ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
G Proteins ◽  
Calcium Influx ◽  
Kinase C ◽  
Rho Family ◽  
Small G Proteins

scholarly journals Protein kinase C-independent stimulation of activator protein-1 and c-Jun N-terminal kinase activity in human endometrial cancer cells by the LHRH agonist triptorelin

2001 ◽  
pp. 651-658 ◽  
Author(s):  
C Grundker ◽  
L Schlotawa ◽  
V Viereck ◽  
G Emons
Keyword(s):  
Cell Proliferation ◽  
Endometrial Cancer ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Cancer Cells ◽  
Fold Increase ◽  
Lhrh Agonist ◽  
Activator Protein 1 ◽  
Kinase C ◽  
Lhrh Receptor

OBJECTIVE: The expression of luteinizing hormone-releasing hormone (LHRH) and its receptor as a part of an autocrine regulatory system of cell proliferation has been demonstrated in a number of human malignant tumours, including cancers of the endometrium. The signalling pathway through which LHRH acts in endometrial cancer is distinct from that in pituitary gonadotrophs. The LHRH receptor interacts with the mitogenic signal transduction of growth factor receptors via activation of a phosphotyrosine phosphatase, resulting in down-regulation of cancer cell proliferation. In addition, LHRH activates nucleus factor kappaB (NFkappaB) and protects the cancer cells from apoptosis. This study was conducted to investigate additional signalling mechanisms of the LHRH receptor cooperating with NFkappaB in endometrial cancer cells. DESIGN: The LHRH agonist triptorelin-induced activator protein-1 (AP-1) activation was analysed using a pAP-1-SEAP reporter gene assay. Expression of c-jun mRNA was quantified using quantitative reverse transcription (RT)-PCR. c-Jun N-terminal kinase (JNK) activity was measured by quantification of phosphorylated c-Jun protein. RESULTS: Treatment of Ishikawa and Hec-1A human endometrial cancer cells with 100 nM triptorelin resulted in a 3.1-fold and 3.5-fold activation of AP-1 respectively (P<0.05). If the cells had been made quiescent, treatment with triptorelin (100 nM) resulted in a 41.7-fold and 48.6-fold increase of AP-1 activation respectively (P<0.001). This effect was completely blocked by simultaneous treatment with pertussis toxin (PTX). A 17.6-fold and 17.3-fold increase of c-jun mRNA expression respectively (P<0.001) was obtained after 20 min of stimulation with triptorelin (100 nM). Treatment with 1 nM triptorelin resulted in a 12.5-fold or an 11.9-fold increase, and treatment with 10 pM triptorelin resulted in a 6.5-fold or a 5.2-fold increase of maximal c-jun mRNA expression respectively (P<0.001). Maximal c-Jun phosphorylation (68.5-fold and 60.2-fold, respectively, P<0.001) was obtained after 90 min incubation with triptorelin (100 nM). CONCLUSIONS: These results suggest that the LHRH agonist triptorelin stimulates the activity of AP-1 in human endometrial cancer cells mediated through PTX-sensitive G-protein alphai. In addition, triptorelin activates JNK, known to activate AP-1. In earlier investigations we have shown that triptorelin does not activate phospholipase and protein kinase C (PKC) in endometrial cancer cells. In addition, it has been demonstrated that triptorelin inhibits growth factor-induced mitogen activated protein kinase (MAPK, ERK) activity. Thus triptorelin-induced activation of the JNK/AP-1 pathway in endometrial cancer cells is independent of the known AP-1 activators, PKC or MAPK (ERK).

Protein kinase C isotypes in human erythroleukemia cell proliferation and differentiation

1992 ◽  
Vol 101 (3) ◽  
pp. 671-679
Author(s):  
B.A. Hocevar ◽  
D.M. Morrow ◽  
M.L. Tykocinski ◽  
A.P. Fields
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Cellular Proliferation ◽  
Biological Effects ◽  
Growth Arrest ◽  
Tumor Promoter ◽  
Induced Differentiation ◽  
Megakaryocytic Differentiation ◽  
Kinase C ◽  
Dose Dependent

The human erythroleukemia (K562) cell line is induced to differentiate into megakaryocytic cells by treatment with the tumor promoter phorbol myristate acetate (PMA). PMA-induced differentiation is characterized by (1) almost complete cessation of cellular proliferation, (2) expression of the megakaryocytic cell surface marker glycoprotein IIb/IIIa (gpIIIa), (3) increased secretion of granulocyte/macrophage-colony stimulating factor (GM-CSF) and (4) increased secretion of interleukin-6 (IL-6). PMA-induced differentiation is dose-dependent with maximal activity seen at 10 nM PMA. In contrast, bryostatin (bryo), a structurally distinct protein kinase C (PKC) activator, fails to induce megakaryocytic differentiation or growth arrest at the concentrations tested (0.01-100 nM). Rather, bryo inhibits PMA-induced growth arrest and megakaryocytic differentiation in a dose-dependent fashion (full inhibition at 100 nM). The divergent biological effects of PMA and bryo correspond to the differential activation and translocation of PKC isotypes in K562 cells. PKC isotype analysis demonstrates that undifferentiated cells express both alpha and beta II PKC but no detectable beta I, gamma or epsilon PKC. Treatment of cells with either PMA or bryo leads to rapid translocation of both alpha and beta II PKC from the cytosol to the non-nuclear particulate fraction. However, bryo also induces selective translocation of beta II PKC to the nuclear membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Protein kinase C isoenzymes in airway smooth muscle

1997 ◽  
Vol 324 (1) ◽  
pp. 167-175 ◽  
Author(s):  
Benjamin L. J. WEBB ◽  
Mark A. LINDSAY ◽  
Peter J. BARNES ◽  
Mark A. GIEMBYCZ
Keyword(s):  
Smooth Muscle ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Anion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Oligonucleotide Primer ◽  
Mrna Levels ◽  
Kinase C ◽  
Gf 109203X ◽  
Bona Fide

The protein kinase C (PKC) isoenzymes expressed by bovine tracheal smooth muscle (BTSM) were identified at the protein and mRNA levels. Western immunoblot analyses reliably identified PKCα, PKCβI and PKCβII. In some experiments immunoreactive bands corresponding to PKCδ, PKCϵ and PKCθ were also labelled, whereas the γ, η and ζ isoforms of PKC were never detected. Reverse transcriptase PCR of RNA extracted from BTSM using oligonucleotide primer pairs designed to recognize unique sequences in the PKC genes for which protein was absent or not reproducibly identified by immunoblotting, amplified cDNA fragments that corresponded to the predicted sizes of PKCδ, PKCϵ and PKCζ, which was confirmed by Southern blotting. Anion-exchange chromatography of the soluble fraction of BTSM following homogenization in Ca2+-free buffer resolved two major peaks of activity. Using ϵ-peptide as the substrate, the first peak of activity was dependent upon Ca2+ and 4β-PDBu (PDBu = phorbol 12,13-dibutyrate), and represented a mixture of PKCs α, βI and βII. In contrast, the second peak of activity, which eluted at much higher ionic strength, also appeared to comprise a combination of conventional PKCs that were arbitrarily denoted PKCα′, PKCβI′ and PKCβII′. However, these novel enzymes were cofactor-independent and did not bind [3H]PDBu, but were equally sensitive to the PKC inhibitor GF 109203X compared with bona fide conventional PKCs, and migrated on SDS/polyacrylamide gels as 81 kDa polypeptides. Taken together, these data suggest that PKCs α′, βI′ and βII′ represent modified, but not proteolysed, forms of their respective native enzymes that retain antibody immunoreactivity and sensitivity to PKC inhibitors, but have lost their sensitivity to Ca2+ and PDBu when ϵ-peptide is used as the substrate.

scholarly journals Inhibition of growth-factor-induced phosphorylation and activation of protein kinase B/Akt by atypical protein kinase C in breast cancer cells

2000 ◽  
Vol 352 (2) ◽  
pp. 475-482 ◽  
Author(s):  
Muling MAO ◽  
Xianjun FANG ◽  
Yiling LU ◽  
Ruth LAPUSHIN ◽  
Robert C. BAST ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Protein Kinase C ◽  
Growth Factor ◽  
Protein Kinase ◽  
Cancer Cells ◽  
Breast Cancer Cells ◽  
Protein Kinase B ◽  
Akt Phosphorylation ◽  
Kinase C ◽  
Pkc Inhibitors

The protein kinase B/Akt serine/threonine kinase, located downstream of phosphoinositide 3-kinase (PI-3K), is a major regulator of cellular survival and proliferation. Atypical protein kinase C (aPKC) family members are activated by PI-3K and also contribute to cell proliferation, suggesting that Akt and aPKC might interact to activate signalling through the PI-3K cascade. Here we demonstrate that blocking PKC activity in MDA-MB-468 breast cancer cells increased the phosphorylation and activity of Akt. Functional PI-3K was required for the PKC inhibitors to increase Akt phosphorylation and activation, potentially owing to the activation of specific PKC isoforms by PI-3K. The concentration dependence of the action of the PKC inhibitors implicates aPKC in the inhibition of Akt phosphorylation and activity. In support of a role for aPKC in the regulation of Akt, Akt and PKCζ or PKCλ/ℓ were readily co-precipitated from the BT-549 breast cancer cell line. Furthermore, the overexpression of PKCζ inhibited growth-factor-induced increases in Akt phosphorylation and activity. Thus PKCζ associates physically with Akt and decreases Akt phosphorylation and enzyme activity. The effects of PKC on Akt were transmitted through the PI-3K cascade as indicated by changes in p70 s6 kinase (p70s6k) phosphorylation. Thus PKCζ, and potentially other PKC isoenzymes, regulate growth-factor-mediated Akt phosphorylation and activation, which is consistent with a generalized role for PKCζ in limiting growth factor signalling through the PI-3K/Akt pathway.

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