scholarly journals Different roles of protein kinase C α and δ isoforms in the regulation of neutral sphingomyelinase activity in HL-60 cells

1999 ◽  
Vol 344 (3) ◽  
pp. 921-928 ◽  
Author(s):  
Dora VIŠNJIĆ ◽  
Drago BATINIŠ ◽  
Hrvoje BANFIŠ
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Inhibitory Effect ◽  
Interferon Γ ◽  
Neutral Sphingomyelinase ◽  
Kinase C ◽  
Pkc Isoforms ◽  
Ifn Γ ◽  
The Difference ◽  
Specific Regulation

The signalling mechanisms responsible for the hydrolysis of sphingomyelin mediated by 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] and interferon γ (IFN-γ) in HL-60 cells were investigated. IFN-γ was found to increase selectively the activity of cytosolic, Mg2+-independent, neutral sphingomyelinase. The treatment of HL-60 cells with the combination of 1,25(OH)2D3 and IFN-γ had an additive effect on sphingomyelin hydrolysis, ceramide release and the activity of cytosolic, Mg2+-independent, neutral sphingomyelinase. The pretreatment of HL-60 cells with staurosporine, chelerythrine chloride and bisindolylmaleimide abolished the activity of sphingomyelinase in response to 1,25(OH)2D3 and IFN-γ. Calphostin C, which acts on the regulatory site of protein kinase C (PKC), and Gö 6976, a selective inhibitor of Ca2+-dependent PKC isoforms, inhibited the effect of 1,25(OH)2D3 but had no effect on the IFN-γ-mediated increase in activity of sphingomyelinase. Isoform-specific antibodies were used to deplete different PKC isoforms from cytosol before the treatment of the cytosolic fraction with 1,25(OH)2D3, arachidonic acid (AA) and PMA. The depletion of PKC isoforms β1, β2, ϵ, η, μ, ζ and λ had no effect on the activation of sphingomyelinase induced by 1,25(OH)2D3 or by AA. The depletion of PKC α from the cytosol completely abolished the effect of 1,25(OH)2D3 on sphingomyelinase activity but had no effect on the AA-induced activity of sphingomyelinase. PMA had no effect on the activity of sphingomyelinase in either untreated or α-depleted cytosol but significantly increased the activity of sphingomyelinase when added to cytosol depleted of PKC ∆. Moreover, PMA inhibited the effect of 1,25(OH)2D3 on sphingomyelinase activation but the inhibitory effect was abolished by prior depletion of PKC ∆ from the cytosol. These studies demonstrate that 1,25(OH)2D3-induced activation of sphingomyelinase is mediated by PKC α. Furthermore, PKC ∆ had an inhibitory effect on sphingomyelinase, suggesting that the difference between the 1,25(OH)2D3- and PMA-mediated effects on sphingomyelin turnover depends on the specific regulation of the PKC α and PKC ∆ isoforms.

Inhibitory Effect of Hypocrellin A on Protein Kinase C in Liver and Skeletal Muscle of Obese Zucker Rats

2003 ◽  
Vol 31 (06) ◽  
pp. 871-878 ◽  
Author(s):  
Xianqin Qu ◽  
Lei Dang ◽  
J. Paul Seale
Keyword(s):  
Skeletal Muscle ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Inhibitory Effect ◽  
Zucker Rats ◽  
Dependent Manner ◽  
Kinase C ◽  
Hypocrellin A ◽  
Pkc Isoforms ◽  
Obese Zucker Rats

In this ex vivo study, the inhibitory activity of hypocrellin A (HA), a perylene quinonoid pigment isolated from the Chinese medicinal fungus Hypocrella bambuase, on protein kinase C (PKC) enzyme activity in insulin target tissues of obese Zucker rats was assessed. Pre-incubation with HA for 30 minutes significantly inhibited the activity of partially purified PKC enzyme from liver and soleus skeletal muscle in a dose-dependent manner ( IC 50=0.07 and 0.26 μg/ml, respectively). HA produced a greater inhibitory effect in enzyme prepared from the liver than enzyme prepared from soleus muscle. Since total PKC activity in these two insulin target tissues is the net result of several different isoforms of PKC, and PKC-θ is a major isoform expressed in the soleus skeletal muscle, the present data suggest that the naturally occurring compound, HA, may selectively inhibit certain PKC isoforms other than PKC-θ. Further investigations are required to determine which PKC isoforms are most susceptible to HA and whether changes in PKC signaling during treatment with HA can reverse abnormalities of glucose and lipid metabolism in insulin resistant and diabetic states.

scholarly journals Gonadotropin-Releasing Hormone Inhibits Pituitary Adenylyl Cyclase-Activating Polypeptide Coupling to 3′,5′-Cyclic Adenosine-5′-Monophosphate Pathway in LβT2 Gonadotrope Cells through Novel Protein Kinase C Isoforms and Phosphorylation of Pituitary Adenylyl Cyclase-Activating Polypeptide Type I Receptor

Endocrinology ◽  
2008 ◽  
Vol 149 (12) ◽  
pp. 6389-6398 ◽  
Author(s):  
Sigolène Larivière ◽  
Ghislaine Garrel-Lazayres ◽  
Violaine Simon ◽  
Norihito Shintani ◽  
Akemichi Baba ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Adenylyl Cyclase ◽  
Inhibitory Effect ◽  
Intracellular Camp ◽  
Type I ◽  
Camp Pathway ◽  
Kinase C ◽  
Pkc Isoforms ◽  
Underlying Mechanisms

Gonadotrope cells are primarily regulated by GnRH but are also targets of the pituitary adenylyl cyclase-activating polypeptide (PACAP). Although it has been reported that reciprocal interactions between both neuropeptides contribute to regulation of gonadotrope function, the underlying mechanisms remain poorly understood. In this study, we reevaluated PACAP coupling to the cAMP pathway in LβT2 gonadotrope cells and analyzed GnRH effect on PACAP signaling. We established that PACAP38 markedly increases intracellular cAMP levels (EC50 of 4.7 ± 1.3 nm) through the PACAP type 1 receptor (PAC1-R), as evidenced by pharmacological and RT-PCR studies. Interestingly, although GnRH couples to cAMP pathway in LβT2 cells, the effects of both neuropeptides were not synergistic. Instead, the GnRH agonist (GnRHa) triptorelin rapidly and strongly inhibited (70% inhibition as early as 5 min) PACAP38-induced cAMP production. Inhibition was calcium independent, mimicked by the phorbol ester phorbol 12-myristate 13-acetate, and blocked by the protein kinase C (PKC) inhibitor bisindoylmaleimide, indicating that GnRHa inhibitory action relies on PKC. Selective down-regulation of both conventional and novel PKC prevented a GnRHa effect, whereas pharmacological inhibition of conventional PKC only was ineffective, strongly suggesting the involvement of novel PKC isoforms. GnRHa did not inhibit forskolin- or cholera toxin-stimulated cAMP accumulation, suggesting that PAC1-R is the predominant target of GnRH. Accordingly, we demonstrated for the first time that GnRH increases PAC1-R phosphorylation through PKC, providing a potential molecular mechanism which may account for GnRH inhibitory effect.

scholarly journals Identification of Key Phospholipids That Bind and Activate Atypical PKCs

Biomedicines ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 45
Author(s):  
Suresh Velnati ◽  
Sara Centonze ◽  
Federico Girivetto ◽  
Daniela Capello ◽  
Ricardo M. Biondi ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phosphatidic Acid ◽  
Kinase Activity ◽  
Membrane Lipids ◽  
Atypical Protein Kinase C ◽  
Atypical Protein Kinase ◽  
Kinase C ◽  
Specific Regulation ◽  
Phosphatidylinositol 4

PKCζ and PKCι/λ form the atypical protein kinase C subgroup, characterised by a lack of regulation by calcium and the neutral lipid diacylglycerol. To better understand the regulation of these kinases, we systematically explored their interactions with various purified phospholipids using the lipid overlay assays, followed by kinase activity assays to evaluate the lipid effects on their enzymatic activity. We observed that both PKCζ and PKCι interact with phosphatidic acid and phosphatidylserine. Conversely, PKCι is unique in binding also to phosphatidylinositol-monophosphates (e.g., phosphatidylinositol 3-phosphate, 4-phosphate, and 5-phosphate). Moreover, we observed that phosphatidylinositol 4-phosphate specifically activates PKCι, while both isoforms are responsive to phosphatidic acid and phosphatidylserine. Overall, our results suggest that atypical Protein kinase C (PKC) localisation and activity are regulated by membrane lipids distinct from those involved in conventional PKCs and unveil a specific regulation of PKCι by phosphatidylinositol-monophosphates.

Relationship between Protein kinase C isoforms, Telomerase and Alpha- fetoprotein through PI3K/AKT/mTOR pathway in Hepatocellular carcinoma

MedPharmRes ◽  
2021 ◽  
Vol 5 (4) ◽  
pp. 12-26
Author(s):  
Rita Ammoury ◽  
Roula Tahtouh ◽  
Nadine Mahfouz ◽  
Raia Doumit ◽  
Charbel Khalil ◽  
...  
Keyword(s):  
Hepatocellular Carcinoma ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Telomerase Activity ◽  
Mtor Pathway ◽  
Alpha Fetoprotein ◽  
Mrna Levels ◽  
Htert Expression ◽  
Kinase C ◽  
Pkc Isoforms

Protein kinase C (PKC) family has been an alluring objective for new cancer drug discovery. It has been reported to regulate telomerase in several cancer types. Our team had previously used telomerase to elucidate alpha-fetoprotein (AFP) modulation in hepatocellular carcinoma (HCC). The aim of this study was to investigate the interrelationships among PKC isoforms, telomerase and AFP in HCC. PKCα and PKCδ were the most expressed isoforms in HepG2/C3A, PLC/PRF/5, SNU-387 and SKOV-3 cells. Following the upregulation of AFP using pCMV3-AFP and the human telomerase reverse transcriptase (hTERT) using a construct expressing a wild-type hTERT, and after their inhibition with all-trans retinoic acid and hTERT siRNA each respectively, we found that the expression of PKCα, PKCβI, PKCβII and PKCδ was affected by the variation of AFP and hTERT mRNA levels. An increase in AFP expression and secretion was observed after gene silencing of PKCα, PKCβ, PKCδ, and PKCε in HepG2/C3A. A similar pattern was observed in transfected PLC/PRF/5 cells, however PKCδ isoform silencing decreased AFP expression. Furthermore, telomerase activity was quantified using quantitative telomeric repeat amplification protocol. The variations in hTERT expression and telomerase activity were similar to those of AFP. Further investigation showed that PKC isoforms regulate AFP and hTERT expression levels through PI3K/AKT/mTOR pathway in HepG2/C3A and PLC/PRF/5 cells. Thus, these results show for the first time a possible interrelationship that links PKC isoforms to both AFP and hTERT via PI3K/AKT/mTOR pathway in HCC.

Inhibitory Effect of Barbiturates and Local Anaesthetics on Protein Kinase C Activation

1990 ◽  
Vol 18 (2) ◽  
pp. 153-160 ◽  
Author(s):  
K. Mikawa ◽  
N. Maekawa ◽  
H. Hoshina ◽  
O. Tanaka ◽  
J. Shirakawa ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Local Anaesthetics ◽  
Inhibitory Effect ◽  
Kinase C ◽  
Protein Kinase C Activation

scholarly journals Modeled microgravity-induced protein kinase C isoform expression in human lymphocytes

2004 ◽  
Vol 96 (6) ◽  
pp. 2028-2033 ◽  
Author(s):  
A. Sundaresan ◽  
D. Risin ◽  
N. R. Pellis
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Type I Collagen ◽  
Human Lymphocytes ◽  
Receptor Interaction ◽  
Type I ◽  
Modeled Microgravity ◽  
Calcium Dependent ◽  
Kinase C ◽  
Pkc Isoforms

In long-term space travel, the crew is exposed to microgravity and radiation that invoke potential hazards to the immune system. T cell activation is a critical step in the immune response. Receptor-mediated signaling is inhibited in both microgravity and modeled microgravity (MMG) as reflected by diminished DNA synthesis in peripheral blood lymphocytes and their locomotion through gelled type I collagen. Direct activation of protein kinase C (PKC) bypassing cell surface events using the phorbol ester PMA rescues MMG-inhibited lymphocyte activation and locomotion, whereas the calcium ionophore ionomycin had no rescue effect. Thus calcium-independent PKC isoforms may be affected in MMG-induced locomotion inhibition and rescue. Both calcium-dependent isoforms and calcium-independent PKC isoforms were investigated to assess their expression in lymphocytes in 1 g and MMG culture. Human lymphocytes were cultured and harvested at 24, 48, 72, and 96 h, and serial samples were assessed for locomotion by using type I collagen and expression of PKC isoforms. Expression of PKC-α, -δ, and -ϵ was assessed by RT-PCR, flow cytometry, and immunoblotting. Results indicated that PKC isoforms δ and ϵ were downregulated by >50% at the transcriptional and translational levels in MMG-cultured lymphocytes compared with 1- g controls. Events upstream of PKC, such as phosphorylation of phospholipase Cγ in MMG, revealed accumulation of inactive enzyme. Depressed calcium-independent PKC isoforms may be a consequence of an upstream lesion in the signal transduction pathway. The differential response among calcium-dependent and calcium-independent isoforms may actually result from MMG intrusion events earlier than PKC, but after ligand-receptor interaction.

scholarly journals Protein Kinase C Mediates the Mitogenic Action of Thrombopoietin in c-Mpl–Expressing UT-7 Cells

Blood ◽  
1998 ◽  
Vol 91 (3) ◽  
pp. 813-822 ◽  
Author(s):  
Ying Hong ◽  
Dominique Dumènil ◽  
Bernd van der Loo ◽  
Frédérique Goncalves ◽  
William Vainchenker ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Subcellular Distribution ◽  
Membrane Fraction ◽  
Induced Expression ◽  
Gm Csf ◽  
Kinase C ◽  
Pkc Isoforms ◽  
Mitogenic Action ◽  
Pkc Activation

Protein kinase C (PKC) has been implicated in signal transduction events elicited by several hematopoietic growth factors. Thrombopoietin (TPO) is the major regulator of megakaryocytic lineage development, and its receptor, c-Mpl, transduces signals for the proliferation and differentiation of hematopoietic progenitors. In this study we have examined the effect of TPO on the subcellular distribution of PKC (a measure of enzyme activation) in a growth factor-dependent pluripotent hematopoietic cell line that was engineered to express the c-Mpl receptor (UT-7/mpl). In addition, we have assessed the significance of this activation for the induction of both mitogenesis and differentiation. Using a PKC translocation assay, TPO was found to stimulate a time- and dose-dependent increase in the total content of PKC activity present in the membrane fraction of UT-7/mpl cells (maximum increase = 2.3-fold above basal level after 15 minutes with 40 ng/mL TPO, EC50 = 7 ng/mL). Accordingly, a decrease of PKC content in the cytosolic fraction was observed. Immunoblot analysis using PKC isotype-specific antibodies showed that TPO treatment led to a marked increase of the Ca2+/diacylglycerol-sensitive PKC isoforms α and β found in the membrane fraction. In contrast, the subcellular distribution of these isoforms did not change after treatment with granulocyte-macrophage colony-stimulating factor (GM-CSF). Exposure of UT-7/mpl cells to the selective PKC inhibitor GF109203X completely inhibited the PKC activity associated to the membrane fraction after TPO treatment, and blocked the mitogenic effect of TPO. In contrast, GF109203X had no effect on the TPO-induced expression of GpIIb, a megakaryocytic differentiation antigen. Downregulation of PKC isoforms α and β to less than 25% of their initial level by treatment with phorbol 12,13-dibutyrate also abolished the TPO-induced mitogenic response, but had no significant effect when this response was induced by GM-CSF. Taken together, these findings suggest that (1) TPO stimulates the activation of PKC, (2) PKC activation mediates the mitogenic action of TPO, and (3) PKC activation is not required for TPO-induced expression of megakaryocytic surface markers.

Protein kinase C-α isoform is involved in erythropoietin-induced erythroid differentiation of CD34+ progenitor cells from human bone marrow

Blood ◽  
2000 ◽  
Vol 95 (2) ◽  
pp. 510-518 ◽  
Author(s):  
June Helen Myklebust ◽  
Erlend B. Smeland ◽  
Dag Josefsen ◽  
Mouldy Sioud
Keyword(s):  
Bone Marrow ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Progenitor Cells ◽  
Erythroid Differentiation ◽  
Human Bone ◽  
Human Bone Marrow ◽  
Kinase C ◽  
Pkc Isoforms ◽  
Cd34 Cells

Protein kinase C (PKC) is a family of serine/threonine protein kinases involved in many cellular responses. Although the analysis of PKC activity in many systems has provided crucial insights to its biologic function, the precise role of different isoforms on the differentiation of normal hematopoietic progenitor cells into the various lineages remains to be investigated. The authors have assessed the state of activation and protein expression of PKC isoforms after cytokine stimulation of CD34+ progenitor cells from human bone marrow. Freshly isolated CD34+ cells were found to express PKC-, PKC-β2, and PKC-ɛ, whereas PKC-δ, PKC-γ, and PKC-ζ were not detected. Treatment with erythropoietin (EPO) or with EPO and stem cell factor (SCF) induced a predominantly erythroid differentiation of CD34+ cells that was accompanied by the up-regulation of PKC- and PKC-β2 protein levels (11.8- and 2.5-fold, respectively) compared with cells cultured in medium. Stimulation with EPO also resulted in the nuclear translocation of PKC- and PKC-β2 isoforms. Notably, none of the PKC isoforms tested were detectable in CD34+ cells induced to myeloid differentiation by G-CSF and SCF stimulation. The PKC inhibitors staurosporine and calphostin C prevented EPO-induced erythroid differentiation. Down-regulation of the PKC-, PKC-β2, and PKC-ɛ expression by TPA pretreatment, or the down-regulation of PKC- with a specific ribozyme, also inhibited the EPO-induced erythroid differentiation of CD34+ cells. No effect was seen with PKC-β2–specific ribozymes. Taken together, these findings point to a novel role for the PKC- isoform in mediating EPO-induced erythroid differentiation of the CD34+ progenitor cells from human bone marrow.

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