scholarly journals Role of Specific Protein Kinase C Isozymes in Mediating Epidermal Growth Factor, Thyrotropin-Releasing Hormone, and Phorbol Ester Regulation of the Rat Prolactin Promoter in GH4/GH4C1 Pituitary Cells

2002 ◽  
Vol 16 (12) ◽  
pp. 2840-2852 ◽  
Author(s):  
Cheryl A. Pickett ◽  
Nicole Manning ◽  
Yoshiko Akita ◽  
Arthur Gutierrez-Hartmann
Keyword(s):  
Gene Transcription ◽  
Promoter Activity ◽  
The Novel ◽  
Calphostin C ◽  
Kinase C ◽  
Epidermal Growth ◽  
Pkc Isozymes ◽  
Pkc Inhibitors ◽  
Prl Gene

Abstract Epidermal growth factor (EGF) and TRH both produce enhanced prolactin (PRL) gene transcription and PRL secretion in GH4 rat pituitary tumor cell lines. These agents also activate protein kinase C (PKC) in these cells. Previous studies have implicated the PKCε isozyme in mediating TRH-induced PRL secretion. However, indirect studies using phorbol ester down-regulation to investigate the role of PKC in EGF- and TRH-induced PRL gene transcription have been inconclusive. In the present study, we examined the role of multiple PKC isozymes on EGF- and TRH-induced activation of the PRL promoter by utilizing general and selective PKC inhibitors and by expression of genes for wild-type and kinase-negative forms of the PKC isozymes. Multiple nonselective PKC inhibitors, including staurosporine, bisindolylmaleimide I, and Calphostin C, inhibited both EGF and TRH induced rat PRL promoter activity. TRH effects were more sensitive to Calphostin C, a competitive inhibitor of diacylglycerol, whereas Go 6976, a selective inhibitor of Ca2+-dependent PKCs, produced a modest inhibition of EGF but no inhibition of TRH effects. Rottlerin, a specific inhibitor of the novel nPKCδ isozyme, significantly blocked both EGF and TRH effects. Overexpression of genes encoding PKCs α, βΙ, βΙΙ, δ, γ, and λ failed to enhance either EGF or TRH responses, whereas overexpression of nPKCη enhanced the EGF response. Neither stable nor transient overexpression of nPKCε produced enhancement of EGF- or TRH-induced PRL promoter activity, suggesting that different processes regulate PRL transcription and hormone secretion. Expression of a kinase inactive nPKCδ construct produced modest inhibition of EGF-mediated rPRL promoter activity. Taken together, these data provide evidence for a role of multiple PKC isozymes in mediating both EGF and TRH stimulated PRL gene transcription. Both EGF and TRH responses appear to require the novel isozyme, nPKCδ, whereas nPKCη may also be able to transmit the EGF response. Inhibitor data suggest that the EGF response may also involve Ca2+-dependent isozymes, whereas the TRH response appears to be more dependent on diacylglycerol.

κ- but not δ-opioid receptors mediate effects of ischemic preconditioning on both infarct and arrhythmia in rats

2001 ◽  
Vol 280 (1) ◽  
pp. H384-H391 ◽  
Author(s):  
Guan-Ying Wang ◽  
Song Wu ◽  
Jian-Ming Pei ◽  
Xiao-Chun Yu ◽  
Tak-Ming Wong
Keyword(s):  
Infarct Size ◽  
Opioid Receptors ◽  
Ischemic Preconditioning ◽  
Antiarrhythmic Action ◽  
Perfused Rat Heart ◽  
Calphostin C ◽  
Kinase C ◽  
Series Of Experiments ◽  
Pkc Inhibitors

Two series of experiments were performed in the isolated perfused rat heart to determine the role of κ- and δ-opioid receptors (OR) in cardioprotection of ischemic preconditioning (IP). In the first series of experiments, it was found that IP with two cycles of 5-min regional ischemia followed by 5-min reperfusion each reduced infarct size induced by 30-min ischemia, and the ameliorating effect of IP on infarct was attenuated with blockade of either 5 × 10−6 mol/l nor-binaltorphimine (nor-BNI), a selective κ-OR antagonist, or 5 × 10−6 mol/l naltrindole (NTD), a selective δ-OR antagonist. The second series showed that U50,488H, a selective κ-OR agonist, ord-Ala2-d-leu5-enkephalin (DADLE), a selective δ-OR agonist, dose dependently reduced the infarct size induced by ischemia, which mimicked the effects of IP. The effect of 10−5 mol/l U50,488H on infarct was significantly attenuated by blockade of protein kinase C (PKC) with specific PKC inhibitors, 5 × 10−6 mol/l chelerythrine or 8 × 10−7 mol/l calphostin C, as well as by blockade of ATP-sensitive K+ (KATP) channels with blockers of the channel, 10−5 mol/l glibenclamide or 10−4 mol/l 5-hydroxydecanoate. IP also reduced arrhythmia induced by ischemia. Nor-BNI, but not NTD, attenuated, while U50,488H, but not DADLE, mimicked the antiarrhythmic action of IP. In conclusion, the present study has provided first evidence that κ-OR mediates the ameliorating effects of IP on infarct and arrhythmia induced by ischemia, whereas δ-OR mediates the effects only on infarct. Both PKC and KATP channels mediate the effect of activation of κ-OR on infarct.

Sustained muscle contraction induced by agonists, growth factors, and Ca2+ mediated by distinct PKC isozymes

2000 ◽  
Vol 279 (1) ◽  
pp. G201-G210 ◽  
Author(s):  
K. S. Murthy ◽  
J. R. Grider ◽  
J. F. Kuemmerle ◽  
G. M. Makhlouf
Keyword(s):  
Growth Factors ◽  
G Protein ◽  
Muscle Cells ◽  
Sustained Contraction ◽  
Calphostin C ◽  
Epidermal Growth ◽  
Pkc Isozymes ◽  
G Protein Coupled ◽  
Pkc Activation

The role of protein kinase C (PKC) in sustained contraction was examined in intestinal circular and longitudinal muscle cells. Initial contraction induced by agonists (CCK-8 and neuromedin C) was abolished by 1) inhibitors of Ca2+ mobilization (neomycin and dimethyleicosadienoic acid), 2) calmidazolium, and 3) myosin light chain (MLC) kinase (MLCK) inhibitor KT-5926. In contrast, sustained contraction was not affected by these inhibitors but was abolished by 1) the PKC inhibitors chelerythrine and calphostin C, 2) PKC-ε antibody, and 3) a pseudosubstrate PKC-ε inhibitor. GDPβS abolished both initial and sustained contraction, whereas a Gαq/11 antibody inhibited only initial contraction, implying that sustained contraction was dependent on activation of a distinct G protein. Sustained contraction induced by epidermal growth factor was inhibited by calphostin C, PKC-α,β,γ antibody, and a pseudosubstrate PKC-α inhibitor. Ca2+ (0.4 μM) induced an initial contraction in permeabilized muscle cells that was blocked by calmodulin and MLCK inhibitors and a sustained contraction that was blocked by calphostin C and a PKC-α,β,γ antibody. Thus initial contraction induced by Ca2+, agonists, and growth factors is mediated by MLCK, whereas sustained contraction is mediated by specific Ca2+-dependent and -independent PKC isozymes. G protein-coupled receptors are linked to PKC activation via distinct G proteins.

Correlation Between Platelet Aggregation and Dephosphorylation of a 68 kDa Protein Revealed through the Use of Putative PKC Inhibitors

1993 ◽  
Vol 70 (04) ◽  
pp. 648-653 ◽  
Author(s):  
Marco E Turini ◽  
Douglas C Gaudette ◽  
Bruce J Holub ◽  
James B Kirkland
Keyword(s):  
Protein Kinase C ◽  
Platelet Aggregation ◽  
Gel Electrophoresis ◽  
Thromboxane A2 ◽  
Human Platelets ◽  
Calphostin C ◽  
Kinase C ◽  
Protein Dephosphorylation ◽  
Pkc Inhibitors

SummaryThe efficacy of two structurally and functionally unrelated protein kinase C (PKC) inhibitors, chelerythrine and calphostin C, was assessed in intact human platelets by studying platelet aggregation in response to Stimulation with phorbol 12-myristate 13-acetate (PMA) or the thromboxane-A2 mimetic, U46619. Surprisingly, both inhibitors increased aggregation in response to PMA, but decreased aggregation in response to U46619. To further explore this phenomenon, gel electrophoresis of 32P-labelled proteins from PMA- or U46619-stimulated platelets in the presence and absence of the two putative PKC inhibitors was performed. Although neither chelerythrine nor calphostin C proved to be effective PKC inhibitors in intact human platelets, a strong correlation between the dephosphorylation of a 68 kDa protein and the rate of platelet aggregation was observed. From these results, the indiscriminate use of PKC inhibitors in whole platelets is questioned and attention is drawn to the role of protein dephosphorylation in platelet activation. The 68 kDa protein was the major phosphorylated substrate in resting platelets. Okadaic acid increased phosphorylation of this band, indicating active phosphate group turnover under resting conditions.

scholarly journals Dysregulation of protein kinase C in adult depression and suicide: evidence from postmortem brain studies

2021 ◽  
Author(s):  
Ghanshyam N Pandey ◽  
Anuradha Sharma ◽  
Hooriyah S Rizavi ◽  
Xinguo Ren
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Protein Expression ◽  
Mrna Expression ◽  
Postmortem Brain ◽  
Cortical Region ◽  
Cytosol Fraction ◽  
Kinase C ◽  
Pkc Isozymes

Abstract Background Several lines of evidence suggest the abnormalities of protein kinase C (PKC) signaling system in mood disorders and suicide based primarily on the studies of PKC and its isozymes in the platelets and postmortem brain of depressed and suicidal subjects. In this study we examined the role of PKC isozymes in depression and suicide. Methods We determined the protein and mRNA expression of various PKC isozymes in the prefrontal cortical region [Brodmann area 9 (BA9)] in 24 normal control (NC) subjects, 24 depressed suicide (DS) subjects and 12 depressed non-suicide (DNS) subjects. The levels of mRNA in the prefrontal cortex (PFC) were determined by qRT-PCR and the protein expression was determined by Western blotting. Results We observed a significant decrease in mRNA expression of PKCα, PKCβI, PKCδ and PKCε and decreased protein expression either in the membrane or the cytosol fraction of PKC isozymes - PKCα, PKCβI, PKCβII and PKCδ in DS and DNS subjects compared with NC subjects. Conclusions The current study provides detailed evidence of specific dysregulation of certain PKC isozymes in the postmortem brain of DS and DNS subjects and further supports earlier evidence for the role of PKC in the platelets and brain of adult and teenage depressed and suicidal population. This comprehensive study may lead to further knowledge of the involvement of PKC in the pathophysiology of depression and suicide.

scholarly journals Targeting Protein Kinase C in Glioblastoma Treatment

Biomedicines ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 381
Author(s):  
Noelia Geribaldi-Doldán ◽  
Irati Hervás-Corpión ◽  
Ricardo Gómez-Oliva ◽  
Samuel Domínguez-García ◽  
Félix A. Ruiz ◽  
...  
Keyword(s):  
Stem Cells ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Combined Treatment ◽  
Primary Brain Tumor ◽  
Kinase C ◽  
Pkc Isozymes ◽  
New Generation ◽  
Effective Drugs

Glioblastoma (GBM) is the most frequent and aggressive primary brain tumor and is associated with a poor prognosis. Despite the use of combined treatment approaches, recurrence is almost inevitable and survival longer than 14 or 15 months after diagnosis is low. It is therefore necessary to identify new therapeutic targets to fight GBM progression and recurrence. Some publications have pointed out the role of glioma stem cells (GSCs) as the origin of GBM. These cells, with characteristics of neural stem cells (NSC) present in physiological neurogenic niches, have been proposed as being responsible for the high resistance of GBM to current treatments such as temozolomide (TMZ). The protein Kinase C (PKC) family members play an essential role in transducing signals related with cell cycle entrance, differentiation and apoptosis in NSC and participate in distinct signaling cascades that determine NSC and GSC dynamics. Thus, PKC could be a suitable druggable target to treat recurrent GBM. Clinical trials have tested the efficacy of PKCβ inhibitors, and preclinical studies have focused on other PKC isozymes. Here, we discuss the idea that other PKC isozymes may also be involved in GBM progression and that the development of a new generation of effective drugs should consider the balance between the activation of different PKC subtypes.

scholarly journals Trans-activation of the human SOX3 promoter by MAZ in NT2/D1 cells

2008 ◽  
Vol 60 (3) ◽  
pp. 379-387 ◽  
Author(s):  
Natasa Kovacevic-Grujicic ◽  
Kazunari Yokoyama ◽  
Milena Stevanovic
Keyword(s):  
Gene Expression ◽  
Neuronal Differentiation ◽  
Gene Transcription ◽  
Binding Sites ◽  
Promoter Activity ◽  
Zinc Finger Protein ◽  
Mobility Shift ◽  
Finger Protein ◽  
Sox3 Gene

In this study, we examine the role of three highly conserved putative binding sites for Myc-associated zinc finger protein (MAZ) in regulation of the human SOX3 gene expression. Electrophoretic mobility shift and supershift assays indicate that complexes formed at two out of three MAZ sites of the human SOX3 promoter involve ubiquitously expressed MAZ protein. Furthermore, in cotransfection experiments we demonstrate that MAZ acts as a positive regulator of SOX3 gene transcription in both undifferentiated and RA-differentiated NT2/D1 cells. Although MAZ increased both basal and RA-induced promoter activity, our results suggest that MAZ does not contribute to RA inducibility of the SOX3 promoter during neuronal differentiation of NT2/D1 cells.

IL-1β enhances β2-adrenergic receptor expression in human airway epithelial cells by activating PKC

2001 ◽  
Vol 280 (4) ◽  
pp. L675-L679 ◽  
Author(s):  
Wei Bin ◽  
Mark O. Aksoy ◽  
Yi Yang ◽  
Steven G. Kelsen
Keyword(s):  
Epithelial Cells ◽  
Adrenergic Receptor ◽  
Airway Epithelial Cells ◽  
Signal Transduction Pathways ◽  
Airway Epithelial ◽  
Calphostin C ◽  
Human Airway ◽  
Pkc Isozymes ◽  
Pkc Inhibitors ◽  
Human Airway Epithelial Cells

Protein kinase C (PKC)-activated signal transduction pathways regulate cell growth and differentiation in many cell types. We have observed that interleukin (IL)-1β upregulates β2-adrenergic receptor (β2-AR) density and β2-AR mRNA in human airway epithelial cells (e.g., BEAS-2B). We therefore tested the hypothesis that PKC-activated pathways mediate IL-1β-induced β-AR upregulation. The role of PKC was assessed from the effects of 1) the PKC activator phorbol 12-myristate 13-acetate (PMA) on β-AR density, 2) selective PKC inhibitors (calphostin C and Ro-31-8220) on β-AR density, and 3) IL-1β treatment on the cellular distribution of PKC isozymes. Recombinant human IL-1β (0.2 nM for 18 h) increased β-AR density to 213% of control values ( P < 0.001). PMA (1 μM for 18 h) increased β-AR density to 225% of control values ( P < 0.005), whereas Ro-31-8220 and calphostin C inhibited the IL-1β-induced upregulation of β-AR in dose-dependent fashion. PKC isozymes detected by Western blotting included α, βII, ε, μ, ζ, and λ/ι. IL-1β increased PKC-μ immunoreactivity in the membrane fraction and had no effect on the distribution of the other PKC isozymes identified. These data indicate that IL-1β-induced β-AR upregulation is mimicked by PKC activators and blocked by PKC inhibitors and appears to involve selective activation of the PKC-μ isozyme. We conclude that signal transduction pathways activated by PKC-μ upregulate β2-AR expression in human airway epithelial cells.

The role of protein kinase C in GH secretion induced by GH-releasing factor and GH-releasing peptides in cultured ovine somatotrophs

1997 ◽  
Vol 154 (2) ◽  
pp. 219-230 ◽  
Author(s):  
D Wu ◽  
I J Clarke ◽  
C Chen
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Dependent Manner ◽  
Adenylyl Cyclase Activity ◽  
Down Regulation ◽  
Gh Secretion ◽  
Calphostin C ◽  
Kinase C ◽  
Pka Pathway

Abstract The involvement of protein kinase C (PKC) in the action of GH-releasing factor (GRF) and synthetic GH-releasing peptides (GHRP-2 and GHRP-6) was investigated in ovine somatotrophs in primary culture. In partially purified sheep somatotrophs, GRF and GHRP-2 caused translocation of PKC activity from the cytosol to the cell membranes and caused GH release in a dose- and time-dependent manner. GHRP-6 did not cause PKC translocation. The PKC inhibitors, calphostin C, staurosporine and chelerythrine, partially reduced GH release in response to GRF and GHRP-2 at doses which selectively inhibit PKC activity. These inhibitors totally abolished GH release caused by phorbol 12-myristate 13-acetate (PMA). Down-regulation of PKC by the treatment of cells with phorbol 12,13-dibutyrate for 16 h caused a significant (P<0·001) reduction in total PKC activity and totally abolished PKC translocation in response to a challenge with GRF, GHRP-2 or PMA. In addition, down-regulation abolished GH release in response to GRF, GHRP-2 or GHRP-6. Treatment of cells with H89, a selective PKA inhibitor, totally blocked GH release caused by either GRF or GHRP-2 and partially reduced PMA-induced GH release. H89 had no effect on PKC translocation caused by GRF, GHRP-2 or PMA and did not affect GH release caused by GHRP-6. These data suggest that GHRP-2 and GRF activate PKC in addition to stimulating adenylyl cyclase activity. Although the cAMP–protein kinase A (PKA) pathway is the major signalling pathway employed by GRF and GHRP-2, the activation of PKC may potentiate signalling via the cAMP–PKA pathway in ovine GH secretion. Importantly, the effect of PMA in increasing the secretion of GH from ovine somatotrophs is effected, in part, by up-regulation of the cAMP–PKA pathway. We conclude that there is cross-talk between the PKC pathway and the cAMP–PKA pathway in ovine somatotrophs during the action of GRF or GHRP. Journal of Endocrinology (1997) 154, 219–230

Protein kinase C regulates endocytosis and recycling of E-cadherin

2002 ◽  
Vol 283 (2) ◽  
pp. C489-C499 ◽  
Author(s):  
Tam Luan Le ◽  
Shannon R. Joseph ◽  
Alpha S. Yap ◽  
Jennifer L. Stow
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Esters ◽  
Recycling Endosomes ◽  
Kinase C ◽  
Pkc Isozymes ◽  
Pkc Activation ◽  
Darby Canine Kidney ◽  
E Cadherin

E-cadherin is a major component of adherens junctions in epithelial cells. We showed previously that a pool of cell surface E-cadherin is constitutively internalized and recycled back to the surface. In the present study, we investigated the potential role of protein kinase C (PKC) in regulating the trafficking of surface E-cadherin in Madin-Darby canine kidney cells. Using surface biotinylation and immunofluorescence, we found that treatment of cells with phorbol esters increased the rate of endocytosis of E-cadherin, resulting in accumulation of E-cadherin in apically localized early or recycling endosomes. The recycling of E-cadherin back to the surface was also decreased in the presence of phorbol esters. Phorbol ester-induced endocytosis of E-cadherin was blocked by specific inhibitors, implicating novel PKC isozymes, such as PKC-ε in this pathway. PKC activation led to changes in the actin cytoskeleton facilitating E-cadherin endocytosis. Depolymerization of actin increased endocytosis of E-cadherin, whereas the PKC-induced uptake of E-cadherin was blocked by the actin stabilizer jasplakinolide. Our findings show that PKC regulates vital steps of E-cadherin trafficking, its endocytosis, and its recycling.

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