201
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Hansen ME, Matsumura F. Down-regulation of particulate protein kinase Cepsilon and up-regulation of nuclear activator protein-1 DNA binding in liver following in vivo exposure of B6C3F1 male mice to heptachlor epoxide. J Biochem Mol Toxicol 2001; 15:1-14. [PMID: 11170310 DOI: 10.1002/1099-0461(2001)15:1<1::aid-jbt1>3.0.co;2-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The effects of in vivo administration of the cyclodiene tumor promoter heptachlor epoxide on mouse liver protein kinase C were studied in male B6C3F1 mice by protein kinase C activity assays and Western blotting under conditions known to increase the incidence of hepatocellular carcinoma because protein kinase C is thought to be critical in phorbol ester-induced tumor promotion. Under these test conditions, 20 ppm dietary heptachlor epoxide for 1-20 days increased cytosolic and decreased particulate total protein kinase C activities, while 10 ppm had no effect. Further, total cytosolic and particulate protein kinase C activities were decreased within 1 hour by 10 mg/kg intraperitoneal (i.p.) heptachlor epoxide. Western blotting showed that conventional protein kinase Calpha and beta isoforms were unaffected by heptachlor epoxide. Particulate novel protein kinase Cepsilon, however, was selectively down-regulated by 1, 10, and 20 ppm dietary heptachlor epoxide, whereas the cytosolic isoform was decreased by 1 and 10 ppm heptachlor epoxide for 10 days. The high-dose treatment for 24 hours also decreased particulate novel protein kinase Cepsilon but increased the cytosolic titer. These results demonstrate that this isoform is unique in its sensitivity to heptachlor epoxide. Activator protein-1 DNA binding, a critical factor in tumor promotion, was substantially increased at 3 and 6 hours with 3.7 mg/kg (i.p.) heptachlor epoxide and at 3 and 10 days with 20 ppm dietary heptachlor epoxide. The effects of heptachlor epoxide on protein kinase C and activator protein-1 are similar to those caused by phorbol ester treatments and correlate well to heptachlor levels found to induce tumors in mice. However, heptachlor epoxide did not initially activate protein kinase C with in vivo treatments or with in vitro treatments of a plasma membrane fraction aimed at demonstrating direct activation, as has been shown for phorbol esters. The ability of heptachlor epoxide to down-regulate particulate novel protein kinase Cepsilon correlates to dosages used in in vivo tumor promotion studies. However, this may represent a negative feedback response rather than a causative effect.
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Affiliation(s)
- M E Hansen
- Institute of Toxicology and Environmental Health, University of California, Davis 95616, USA
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202
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Frey MR, Leontieva O, Watters DJ, Black JD. Stimulation of protein kinase C-dependent and -independent signaling pathways by bistratene A in intestinal epithelial cells. Biochem Pharmacol 2001; 61:1093-100. [PMID: 11301042 PMCID: PMC3601670 DOI: 10.1016/s0006-2952(01)00596-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The marine toxin bistratene A (BisA) potently induces cytostasis and differentiation in a variety of systems. Evidence that BisA is a selective activator of protein kinase C (PKC) delta implicates PKC delta signaling in the negative growth-regulatory effects of this agent. The current study further investigates the signaling pathways activated by BisA by comparing its effects with those of the PKC agonist phorbol 12-myristate 13-acetate (PMA) in the IEC-18 intestinal crypt cell line. Both BisA and PMA induced cell cycle arrest in these cells, albeit with different kinetics. While BisA produced sustained cell cycle arrest in G(0)/G(1) and G(2)/M, the effects of PMA were transient and involved mainly a G(0)/G(1) blockade. BisA also produced apoptosis in a proportion of the population, an effect not seen with PMA. Both agents induced membrane translocation/activation of PKC, with BisA translocating only PKC delta and PMA translocating PKC alpha, delta, and epsilon in these cells. Notably, while depletion of PKC alpha, delta, and epsilon abrogated the cell cycle-specific effects of PMA in IEC-18 cells, the absence of these PKC isozymes failed to inhibit BisA-induced G(0)/G(1) and G(2)/M arrest or apoptosis. The cell cycle inhibitory and apoptotic effects of BisA, therefore, appear to be PKC-independent in IEC-18 cells. On the other hand, BisA and PMA both promoted PKC-dependent activation of Erk 1 and 2 in this system. Thus, intestinal epithelial cells respond to BisA through activation of at least two signaling pathways: a PKC delta-dependent pathway, which leads to activation of mitogen-activated protein kinase and possibly cytostasis in the appropriate context, and a PKC-independent pathway, which induces both cell cycle arrest in G(0)/G(1) and G(2)/M and apoptosis through as yet unknown mechanisms.
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Affiliation(s)
- Mark R. Frey
- Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY 14263, USA
| | - Olga Leontieva
- Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY 14263, USA
| | - Dianne J. Watters
- Department of Surgery, University of Queensland, Clinical Sciences Building, Royal Brisbane Hospital, Brisbane 4029, Australia
| | - Jennifer D. Black
- Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY 14263, USA
- Corresponding author. Tel.: +1-716-845-5766; fax: +1-716-845-8857. (J.D. Black)
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203
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Kazanietz MG, Caloca MJ, Aizman O, Nowicki S. Phosphorylation of the Catalytic Subunit of Rat Renal Na+,K+-ATPase by Classical PKC Isoforms. Arch Biochem Biophys 2001; 388:74-80. [PMID: 11361144 DOI: 10.1006/abbi.2000.2264] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In this study we have evaluated the specificity of different PKC isozymes for the phosphorylation of the catalytic alpha1 subunit of rat renal Na+,K+-ATPase (alpha1 Na+,K+-ATPase). Using in vitro phosphotransferase assays we found that classical PKCs (cPKCs) alpha, betaI, and gamma efficiently phosphorylate alpha1 Na+,K+-ATPase. However, alpha1 Na+,K+-ATPase was a poor substrate for the novel PKCs (nPKCs) delta and epsilon. Two-dimensional phosphopeptide mapping revealed a similar pattern of phosphorylation by all cPKCs. The functional significance of this finding was evaluated by measuring Na+,K+-ATPase activity (assessed by 86Rb+ uptake) in COS-7 cells expressing the rat alpha1 Na+,K+-ATPase. 1-oleoyl-2-acetoyl-sn-glycerol (OAG), a nonselective PKC activator, inhibited Na+,K+-ATPase activity in this system. On the other hand, 12-deoxyphorbol-13-phenylacetate (DPP), which preferentially activates nPKCepsilon, did not affect 86Rb+ uptake. These results indicate a differential pattern of phosphorylation and regulation of rat renal Na+,K+-ATPase activity by PKC isoforms and suggest an important role for cPKCs in the physiological regulation of the pump.
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Affiliation(s)
- M G Kazanietz
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia 19104-6160, USA
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204
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England K, Watson J, Beale G, Warner M, Cross J, Rumsby M. Signalling pathways regulating the dephosphorylation of Ser729 in the hydrophobic domain of protein kinase Cepsilon upon cell passage. J Biol Chem 2001; 276:10437-42. [PMID: 11121415 DOI: 10.1074/jbc.m009421200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have recently demonstrated that in quiescent fibroblasts protein kinase C (PKC) epsilon(95) is phosphorylated at Ser(729), Ser(703), and Thr(566) and that upon passage of quiescent cells phosphorylation at Ser(729) is lost, giving rise to PKCepsilon(87). Ser(729) may be rephosphorylated later, suggesting cycling between PKCepsilon(87) and PKCepsilon(95). Here we show that the dephosphorylation at Ser(729) is insensitive to okadaic acid, calyculin, ascomycin C, and cyclosporin A, suggesting that dephosphorylation at this site is not mediated through protein phosphatases 1, 2A or 2B. We demonstrate that this dephosphorylation at Ser(729) requires serum and cell readhesion and is sensitive to rapamycin, PD98059, chelerythrine, and Ro-31-8220. These results suggest that the phosphorylation status of Ser(729) in the hydrophobic domain at Ser(729) is regulated independently of the phosphorylation status of other sites in PKCepsilon, by a mTOR-sensitive phosphatase. The mitogen-activated protein kinase pathway and PKC are also implicated in regulating the dephosphorylation at Ser(729).
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Affiliation(s)
- K England
- Department of Biology, University of York, York YO10 5DD, United Kingdom.
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205
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Hansen ME, Matsumura F. Effects of heptachlor epoxide on components of various signal transduction pathways important in tumor promotion in mouse hepatoma cells. Determination of the most sensitive tumor promoter related effect induced by heptachlor epoxide. Toxicology 2001; 160:139-53. [PMID: 11246134 DOI: 10.1016/s0300-483x(00)00445-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The effects of the organochlorine (OC) liver tumor promoter heptachlor epoxide (HE; 0, 0.1, 1, 10, and 50 microM) on several cellular tumor promoter-sensitive parameters were studied in mouse 1c1c7 hepatoma cells in an effort to identify the most sensitive biomarker for OC promoter exposure and the critical pathway and target of OC promoters. The levels of Ca2+ in the endoplasmic reticulum (ER) store, connexin43 (Cx43), PLCgamma(1), nPKCvarepsilon, and AP-1 DNA binding in nucleus were studied to screen for effects induced by submicromolar HE levels. While all the parameters tested elicited effects, particulate PLCgamma(1) and AP-1 DNA binding were found to be the most sensitive parameters affected by HE on both dose and temporal bases. Their levels were increased with 10- to 100-fold lower HE concentrations than were required to affect nPKCvarepsilon or Cx43. Further, with the lower HE dosages, particulate PLCgamma(1) and nuclear AP-1 were positively modulated by HE after 1 h versus 3 or 72 h for nPKCvarepsilon and Cx43. Ca2+ store depletion was probably the third most sensitive parameter, after AP-1 and PLCgamma(1). These results suggest the tyrosine kinase growth factor receptor pathway is the probable critical pathway for HE-induce tumor promotion with the critical target most likely being upstream of PLCgamma(1) and AP-1. This work also demonstates that upon exposure to a tumor promoter such as HE, many hepatocellular effects or changes result, suggesting that a cellular-program shift occurs similar to that described by the resistant hepatocyte model after exposure to a carcinogen or enzyme inducer.
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Affiliation(s)
- M E Hansen
- Institute of Toxicology and Environmental Health, University of California, Davis, CA 95616, USA
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206
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Abstract
PKC isoenzymes were found to be involved in proliferation, antitumor drug resistance and apoptosis. Therefore, it has been tried to exploit PKC as a target for antitumor treatment. PKC alpha activity was found to be elevated, for example, in breast cancers and malignant gliomas, whereas it seems to be underexpressed in many colon cancers. So it can be expected that inhibition of PKC activity will not show similar antitumor activity in all tumors. In some tumors it seems to be essential to inhibit PKC to reduce growth. However, for inhibition of tumor proliferation it may be an advantage to induce apoptosis. In this case an activation of PKC delta should be achieved. The situation is complicated by the facts that bryostatin leads to the activation of PKC and later to a downmodulation and that the PKC inhibitors available to date are not specific for one PKC isoenzyme. For these reasons, PKC modulation led to many contradicting results. Despite these problems, PKC modulators such as miltefosine, bryostatin, safingol, CGP41251 and UCN-01 are used in the clinic or are in clinical evaluation. The question is whether PKC is the major or the only target of these compounds, because they also interfere with other targets. PKC may also be involved in apoptosis. Oncogenes and growth factors can induce cell proliferation and cell survival, however, they can also induce apoptosis, depending on the cell type or conditions in which the cells or grown. PKC participates in these signalling pathways and cross-talks. Induction of apoptosis is also dependent on many additional factors, such as p53, bcl-2, mdm2, etc. Therefore, there are also many contradicting results on PKC modulation of apoptosis. Similar controversial data have been reported about MDR1-mediated multidrug resistance. At present it seems that PKC inhibition alone without direct interaction with PGP will not lead to successful reversal of PGP-mediated drug efflux. One possibility to improve chemotherapy would be to combine established antitumor drugs with modulators of PKC. However, here also very contrasting results were obtained. Many indicate that inhibition, others, that activation of PKC enhances the antiproliferative activity of anticancer drugs. The problem is that the exact functions of the different PKC isoenzymes are not clear at present. So further investigations into the role of PKC isoenzymes in the complex and interacting signalling pathways are essential. It is a major challenge in the future to reveal whether modulation of PKC can be used for the improvement of cancer therapy.
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Affiliation(s)
- J Hofmann
- Institute of Medical Chemistry and Biochemistry, University of Innsbruck, A-6020 Innsbruck, Austria
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207
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García-García J, Gómez-Fernández JC, Corbalán-García S. Structural characterization of the C2 domain of novel protein kinase Cepsilon. EUROPEAN JOURNAL OF BIOCHEMISTRY 2001; 268:1107-17. [PMID: 11179977 DOI: 10.1046/j.1432-1327.2001.2680041107.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Infrared spectroscopy (IR) and differential scanning calorimetry (DSC) were used to study the biophysical properties of the PKCepsilon-C2 domain, a C2 domain that possess special characteristics as it binds to acidic phospholipids in a Ca2+-independent manner and no structural information about it is available to date. When the secondary structure was determined by IR spectroscopy in H2O and D2O buffers, beta sheet was seen to be the major structural component. Spectroscopic studies of the thermal denaturation in D2O showed a broadening in the amide I' band starting at 45 degrees C. Curve fitting analysis of the spectra demonstrated that two components appear upon thermal denaturation, one at 1623 cm(-1) which was assigned to aggregation and a second one at 1645 cm(-1), which was assigned to unordered or open loop structures. A lipid binding assay has demonstrated that PKCepsilon-C2 domain has preferential affinity for PIP2 although it exhibits maximal binding activity for phosphatidic acid when 100 mol% of this negatively charged phospholipid was used. Thus, phosphatidic acid containing vesicles were used to characterize the effect of lipid binding on the secondary structure and thermal stability. These experiments showed that the secondary structure did not change upon lipid binding and the thermal stability was very high with no significant changes occurring in the secondary structure after heating. DSC experiments demonstrated that when the C2-protein was scanned alone, it showed a Tm of 49 degrees C and a calorimetric denaturation enthalpy of 144.318 kJ x mol(-1). However, when phoshatidic acid vesicles were included in the mixture, the transition disappeared and further IR experiments demonstrated that the protein structure was not modified under these conditions.
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Affiliation(s)
- J García-García
- Departamento de Bioquímica y Biología Molecular 'A', Facultad de Veterinaria, Universidad de Murcia, Spain
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208
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Shen S, Alt A, Wertheimer E, Gartsbein M, Kuroki T, Ohba M, Braiman L, Sampson SR, Tennenbaum T. PKCdelta activation: a divergence point in the signaling of insulin and IGF-1-induced proliferation of skin keratinocytes. Diabetes 2001; 50:255-64. [PMID: 11272134 DOI: 10.2337/diabetes.50.2.255] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Insulin and insulin-like growth factor-1 (IGF-1) are members of the family of the insulin family of growth factors, which activate similar cellular downstream pathways. In this study, we analyzed the effects of insulin and IGF-1 on the proliferation of murine skin keratinocytes in an attempt to determine whether these hormones trigger the same signaling pathways. Increasing doses of insulin and IGF-1 promote keratinocyte proliferation in an additive manner. We identified downstream pathways specifically involved in insulin signaling that are known to play a role in skin physiology; these include activation of the Na+/K+ pump and protein kinase C (PKC). Insulin, but not IGF-1, stimulated Na+/K+ pump activity. Furthermore, ouabain, a specific Na+/K+ pump inhibitor, abolished the proliferative effect of insulin but not that of IGF-1. Insulin and IGF-1 also differentially regulated PKC activation. Insulin, but not IGF-1, specifically activated and translocated the PKCB isoform to the membrane fraction. There was no effect on PKC isoforms alpha, eta, epsilon, and zeta, which are expressed in skin. PKC8 overexpression increased keratinocyte proliferation and Na+/K+ pump activity to a degree similar to that induced by insulin but had no affect on IGF-1-induced proliferation. Furthermore, a dominant negative form of PKCdelta abolished the effects of insulin on both proliferation and Na+/K+ pump activity but did not abrogate induction of keratinocyte proliferation induced by other growth factors. These data indicate that though insulin or IGF-1 stimulation induce keratinocyte proliferation, only insulin action is specifically mediated via PKC8 and involves activation of the Na+/K+ pump.
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Affiliation(s)
- S Shen
- Faculty of Life Sciences, Gonda-Goldschmeid Center, Bar-Ilan University, Ramat-Gan, Israel
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209
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Thodeti CK, Nielsen CK, Paruchuri S, Larsson C, Sjölander A. The epsilon isoform of protein kinase C is involved in regulation of the LTD(4)-induced calcium signal in human intestinal epithelial cells. Exp Cell Res 2001; 262:95-103. [PMID: 11139333 DOI: 10.1006/excr.2000.5077] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated the potential roles of specific isoforms of protein kinase C (PKC) in the regulation of leukotriene D(4)-induced Ca(2+) signaling in the intestinal epithelial cell line Int 407. RT-PCR and Western blot analysis revealed that these cells express the PKC isoforms alpha, betaII, delta, epsilon, zeta, and mu, but not betaI, gamma, eta, or theta;. The inflammatory mediator leukotriene D(4) (LTD(4)) caused the TPA-sensitive PKC isoforms alpha, delta, and epsilon, but not betaII, to rapidly translocate to a membrane-enriched fraction. The PKC inhibitor GF109203X at 30 microM but not 2 microM significantly impaired the LTD(4)-induced Ca(2+) signal, indicating that the response involves a novel PKC isoform, such as delta or epsilon, but not alpha. LTD(4)-induced Ca(2+) signaling was significantly suppressed in cells pretreated with TPA for 15 min and was abolished when the pretreatment was prolonged to 2 h. Immunoblot analysis revealed that the reduction in the LTD(4)-induced calcium signal coincided with a reduction in the cellular content of PKCepsilon and, to a limited extent, PKCdelta. LTD(4)-induced Ca(2+) signaling was also markedly suppressed by microinjection of antibodies against PKCepsilon but not PKCdelta. These data suggest that PKCepsilon plays a unique role in regulation of the LTD(4)-dependent Ca(2+) signal in intestinal epithelial cells.
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Affiliation(s)
- C K Thodeti
- Division of Experimental Pathology, Lund University, U-MAS, Malmö, SE-205 02, Sweden
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210
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Gaubert F, Escaffit F, Bertrand C, Korc M, Pradayrol L, Clemente F, Estival A. Expression of the high molecular weight fibroblast growth factor-2 isoform of 210 amino acids is associated with modulation of protein kinases C delta and epsilon and ERK activation. J Biol Chem 2001; 276:1545-54. [PMID: 11031252 DOI: 10.1074/jbc.m001184200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The high molecular weight (HMW) fibroblast growth factor (FGF)-2 isoform of 210 amino acids initiated at a CUG start codon possesses a nuclear localization sequence and is not secreted. In contrast, the low molecular weight (LMW) isoform of 155 amino acids initiated at the AUG start codon can be secreted and activates the cell surface FGF receptors. The two isoforms possess different biological properties; however, little is known about the intracrine regulatory mechanisms involved in the biological effects of the HMW FGF-2 isoform. Using pancreatic cells stably transfected with cDNAs leading to the expression of either the HMW FGF-2 (A3 cells) or the LMW form (A5 cells), we provide evidence that the two FGF-2 isoforms differentially modulate PKC levels. The LMW FGF-2 up-regulated the PKC epsilon levels by 1.6-fold; by contrast the HMW isoform down-regulated the level of this PKC isotype by about 3-fold and increased the amount of PKC delta by 1.7-fold. PKC mRNAs were also modified, suggesting that PKC expression was regulated at a pretranslational level. Additionally, expression of different levels of the HMW FGF-2 with an inducible expression system confirmed the role of this isoform on PKC delta and epsilon expressions. Increased activation of ERK-1 and -2 was also observed in cells expressing the HMW FGF-2. By using different PKC inhibitors and a dominant negative PKC delta, it was found that ERK activation was PKC delta-dependent. These data indicate that expression of HMW FGF-2 can modify PKC levels by acting at the intracellular level and that the overexpression of PKC delta induces ERK-1/2 activation. The expression of a dominant negative FGFR1 did not reduce ERK-1/2 activation by the HMW FGF-2, suggesting that ERK activation does not require FGFR activity. The signaling cascade downstream of ERK might be involved in the known mitogenic effect exerted by this FGF-2 isoform.
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Affiliation(s)
- F Gaubert
- INSERM U 531, Institut Louis Bugnard, CHU Rangueil Bat L 3, 31403 Toulouse Cedex 4, France
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211
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Takahashi T, Shibuya M. The overexpression of PKCdelta is involved in vascular endothelial growth factor-resistant apoptosis in cultured primary sinusoidal endothelial cells. Biochem Biophys Res Commun 2001; 280:415-20. [PMID: 11162532 DOI: 10.1006/bbrc.2000.4123] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have previously reported that primary sinusoidal endothelial cells from the rat liver are highly dependent on VEGF for cell proliferation in in vitro culture. However, even in the presence of VEGF, essentially all the SE cells could not survive longer than 7 days, leading to growth factor-resistant cell death. The death had characteristics typical of apopotosis, such as DNA fragmentation, staining with TUNEL reagent and nuclear condensation. We found that the cell death was blocked by the treatment of TPA in a dose-dependent manner and was preceded by a remarkable increase in PKCdelta at a protein level. Furthermore, PKCdelta-specific inhibitor, Rottrelin, significantly suppressed this VEGF-resistant apoptosis of cultured SE cells, whereas conventional PKC-specific inhibitor, Go6976 could not. TPA was found to downregulate the overexpression of PKCdelta. Thus, we suggest that the VEGF-resistant apoptosis is a new type of endothelial cell death and that PKCdelta is an essential mediator for this process.
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Affiliation(s)
- T Takahashi
- Department of Genetics, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo 108-8639, Japan.
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212
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Davis CD, Johnson WT. Dietary copper and dimethylhydrazine affect protein kinase C isozyme protein and mRNA expression and the formation of aberrant crypts in colon of rats. Biofactors 2001; 15:11-26. [PMID: 11673641 DOI: 10.1002/biof.5520150102] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Low dietary copper has been shown to decrease the expression of various protein kinase C (PKC) isozymes and increase the risk of colon cancer development in experimental animals. The purpose of this study was to investigate the relationship between dietary copper and carcinogen administration on PKC isozyme accumulation and aberrant crypt foci (ACF) formation in rats fed 0.9 and 7.7 microg Cu/g diet. After 24 and 31 d on the diets, the rats were injected with either dimethylhydrazine (DMH) (25 mg/kg i.p.) or saline and killed at two time points (2 wk and 8 wk after DMH). Rats fed low dietary copper had significantly lower (p<0.0001) hematocrits, hemoglobin, ceruloplasmin activity and plasma and liver copper concentrations than rats fed adequate dietary copper. Ingestion of low dietary copper significantly (p<0.005) increased the formation of DMH-induced ACF (116.8 vs 59.6). Low dietary copper significantly (p<0.05) decreased the concentration of PKC alpha, delta, and zeta in the colon at 2 wk but not at 8 wk. Thus, changes in PKC isoform protein concentration may be related to increased susceptibility of copper-deficient animals to colon cancer.
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Affiliation(s)
- C D Davis
- United States Department of Agriculture, Agricultural Research Service, Grand Forks Human Nutrition Research Center, Grand Forks, ND 58202-9034, USA.
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213
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Corbau R, Duverger V, Rommelaere J, Nüesch JP. Regulation of MVM NS1 by protein kinase C: impact of mutagenesis at consensus phosphorylation sites on replicative functions and cytopathic effects. Virology 2000; 278:151-67. [PMID: 11112491 DOI: 10.1006/viro.2000.0600] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Minute virus of mice NS1, an 83-kDa mainly nuclear phosphoprotein, is the only viral nonstructural protein required in all cell types and it is involved in multiple processes necessary for virus propagation. The diversity of functions assigned to NS1, together with the variation of its complex phosphorylation pattern during infection, suggested that the various activities of NS1 could be regulated by distinct phosphorylation events. So far, it has been demonstrated that NS1 replicative functions, in particular, DNA-unwinding activities, are regulated by protein kinase C (PKC), as exemplified by the modulation of NS1 helicase activity by PKClambda phosphorylation. In order to determine further impact of phosphorylation on NS1 functions, including the induction of cytopathic effects, a mutational approach was pursued in order to produce NS1 variants harboring amino acid substitutions at candidate PKC target residues. Besides the determination of two additional in vivo phosphorylation sites in NS1, this mutagenesis allowed the segregation of distinct NS1 functions from one another, generating NS1 variants with a distinct activity profile. Thus, we obtained NS1 mutants that were fully proficient for trans activation of the viral P38 promoter, while being impaired in their replicative functions. Moreover, the alterations of specific PKC phosphorylation sites gave rise to NS1 polypeptides that exerted reduced cytotoxicity, leading to sustained gene expression, while keeping functions necessary for progeny virus production, i.e., viral DNA replication and activation of the capsid gene promoter. These data suggested that in the course of a viral infection, NS1 may undergo a shift from productive to cytotoxic functions as a result of a phosphorylation-dependent regulation.
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Affiliation(s)
- R Corbau
- Program of Applied Tumor Virology, Institut National de la Santé et de la Recherche Médicale U375, Heidelberg, Germany
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214
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Blake RA, Broome MA, Liu X, Wu J, Gishizky M, Sun L, Courtneidge SA. SU6656, a selective src family kinase inhibitor, used to probe growth factor signaling. Mol Cell Biol 2000; 20:9018-27. [PMID: 11074000 PMCID: PMC86555 DOI: 10.1128/mcb.20.23.9018-9027.2000] [Citation(s) in RCA: 488] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The use of small-molecule inhibitors to study molecular components of cellular signal transduction pathways provides a means of analysis complementary to currently used techniques, such as antisense, dominant-negative (interfering) mutants and constitutively activated mutants. We have identified and characterized a small-molecule inhibitor, SU6656, which exhibits selectivity for Src and other members of the Src family. A related inhibitor, SU6657, inhibits many kinases, including Src and the platelet-derived growth factor (PDGF) receptor. The use of SU6656 confirmed our previous findings that Src family kinases are required for both Myc induction and DNA synthesis in response to PDGF stimulation of NIH 3T3 fibroblasts. By comparing PDGF-stimulated tyrosine phosphorylation events in untreated and SU6656-treated cells, we found that some substrates (for example, c-Cbl, and protein kinase C delta) were Src family substrates whereas others (for example, phospholipase C-gamma) were not. One protein, the adaptor Shc, was a substrate for both Src family kinases (on tyrosines 239 and 240) and a distinct tyrosine kinase (on tyrosine 317, which is perhaps phosphorylated by the PDGF receptor itself). Microinjection experiments demonstrated that a Shc molecule carrying mutations of tyrosines 239 and 240, in conjunction with an SH2 domain mutation, interfered with PDGF-stimulated DNA synthesis. Deletion of the phosphotyrosine-binding domain also inhibited synthesis. These inhibitions were overcome by heterologous expression of Myc, supporting the hypothesis that Shc functions in the Src pathway. SU6656 should prove a useful additional tool for further dissecting the role of Src kinases in this and other signal transduction pathways.
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Affiliation(s)
- R A Blake
- SUGEN Inc., South San Francisco, California 94080, USA
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215
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Simon AK, Auphan N, Pophillat M, Boyer C, Ghosh S, Rincón M, Flavell RA, Schmitt-Verhulst AM. The lack of NF-kappa B transactivation and PKC epsilon expression in CD4(+)CD8(+) thymocytes correlates with negative selection. Cell Death Differ 2000; 7:1253-62. [PMID: 11175263 DOI: 10.1038/sj.cdd.4400760] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Deletion of autoreactive thymocytes at the DP stage is the basis for tolerance to thymus-expressed self antigens. In this study we investigated whether distinct signalling pathways are induced in DP thymocytes as compared to mature T cells upon stimulation with antigen. Using triple transgenic mice expressing a TCR transgene, dominant negative ras/Mek proteins and a reporter gene construct with AP-1 or NF-kappa B binding sites, we showed a complete lack of transcriptional activity of NF-kappa B but not AP-1 in DP thymocytes, whereas both were transcriptionally active in mature T cells after antigenic stimulation. Lack of NF-kappa B induction correlated with increased death in response to antigen. AP-1 induction was dependent on the integrity of the ras/Mek pathway indicating that this pathway was activated in the DP thymocytes. In contrast, we found a complete lack of constitutive expression of the epsilon isoform of Protein Kinase C (PKC) in DP thymocytes, although it was present in mature thymocytes and peripheral T cells. Taken together the results suggest that the lack of PKC epsilon in DP thymocytes could lead to the absence of NF-kappa B activity after antigenic stimulation contributing to negative selection. Cell Death and Differentiation (2000) 7, 1253 - 1262.
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Affiliation(s)
- A K Simon
- Centre d'Immunologie INSERM-CNRS de Marseille Luminy, Marseille, France.
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216
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Bähr C, Rohwer A, Stempka L, Rincke G, Marks F, Gschwendt M. DIK, a novel protein kinase that interacts with protein kinase Cdelta. Cloning, characterization, and gene analysis. J Biol Chem 2000; 275:36350-7. [PMID: 10948194 DOI: 10.1074/jbc.m004771200] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A novel serine/threonine kinase, termed DIK, was cloned using the yeast two-hybrid system to screen a cDNA library from the human keratinocyte cell line HaCaT with the catalytic domain of rat protein kinase Cdelta (PKCdelta(cat)) cDNA as bait. The predicted 784-amino acid polypeptide with a calculated molecular mass of 86 kDa contains a catalytic kinase domain and a putative regulatory domain with ankyrin-like repeats and a nuclear localization signal. Expression of DIK at the mRNA and protein level could be demonstrated in several cell lines. The dik gene is located on chromosome 21q22.3 and possesses 8 exons and 7 introns. DIK was synthesized in an in vitro transcription/translation system and expressed as recombinant protein in bacteria, HEK, COS-7, and baculovirus-infected insect cells. In the in vitro system and in cells, but not in bacteria, various post-translationally modified forms of DIK were produced. DIK was shown to exhibit protein kinase activity toward autophosphorylation and substrate phosphorylation. The interaction of PKCdelta(cat) and PKCdelta with DIK was confirmed by coimmunoprecipitation of the proteins from HEK cells transiently transfected with PKCdelta(cat) or PKCdelta and DIK expression constructs.
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Affiliation(s)
- C Bähr
- German Cancer Research Center, D-69120 Heidelberg, Germany
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217
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Frey MR, Clark JA, Leontieva O, Uronis JM, Black AR, Black JD. Protein kinase C signaling mediates a program of cell cycle withdrawal in the intestinal epithelium. J Cell Biol 2000; 151:763-78. [PMID: 11076962 PMCID: PMC2169440 DOI: 10.1083/jcb.151.4.763] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2000] [Accepted: 09/25/2000] [Indexed: 12/21/2022] Open
Abstract
Members of the protein kinase C (PKC) family of signal transduction molecules have been widely implicated in regulation of cell growth and differentiation, although the underlying molecular mechanisms involved remain poorly defined. Using combined in vitro and in vivo intestinal epithelial model systems, we demonstrate that PKC signaling can trigger a coordinated program of molecular events leading to cell cycle withdrawal into G(0). PKC activation in the IEC-18 intestinal crypt cell line resulted in rapid downregulation of D-type cyclins and differential induction of p21(waf1/cip1) and p27(kip1), thus targeting all of the major G(1)/S cyclin-dependent kinase complexes. These events were associated with coordinated alterations in expression and phosphorylation of the pocket proteins p107, pRb, and p130 that drive cells to exit the cell cycle into G(0) as indicated by concomitant downregulation of the DNA licensing factor cdc6. Manipulation of PKC isozyme levels in IEC-18 cells demonstrated that PKCalpha alone can trigger hallmark events of cell cycle withdrawal in intestinal epithelial cells. Notably, analysis of the developmental control of cell cycle regulatory molecules along the crypt-villus axis revealed that PKCalpha activation is appropriately positioned within intestinal crypts to trigger this program of cell cycle exit-specific events in situ. Together, these data point to PKCalpha as a key regulator of cell cycle withdrawal in the intestinal epithelium.
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Affiliation(s)
- M R Frey
- Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, New York 14263, USA.
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218
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Carlin S, Poronnik P, Cook DI, Carpenter L, Biden TJ, Johnson PR, Black JL. An antisense of protein kinase C-zeta inhibits proliferation of human airway smooth muscle cells. Am J Respir Cell Mol Biol 2000; 23:555-9. [PMID: 11017922 DOI: 10.1165/ajrcmb.23.4.4197] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
We hypothesized that an atypical isoform of protein kinase (PK) C, PKC-zeta, is essential for proliferation of human airway smooth muscle (HASM) cells in primary culture. Recombinant replication-deficient E1-deleted adenoviruses (100 plaque-forming units [pfu]/cell) expressing the antisense of PKC-zeta and the wild-type PKC-zeta (Ad-CMV-PKC-zeta) were added to actively growing cells that were subsequently incubated for 48 h in platelet-derived growth factor (PDGF) 40 ng/mL or 10% fetal bovine serum (FBS). Expression of the antisense at a virus concentration of 100 pfu/cell produced a significant (n = 3, P<0.05) decrease in the mean manual cell count in the presence of PDGF to 37+/-5% relative to that in cells with no virus (100%), whereas in cells infected with virus containing no construct, this figure was 102+/-13%. The increase in cell number in response to FBS, however, was not affected by the presence of the antisense. Corresponding values for cells in 10% FBS were 100+/-22%, 85+/-22%, and 122+/-18%. Western blotting revealed decreased levels of PKC-zeta protein, but not PKC-alpha or PKC-epsilon protein, in cells infected with the antisense when compared with levels in control cells. Thus, in HASM cells, PKC-zeta is involved in proliferation in response to PDGF, but not in response to FBS, for which alternate signal transduction pathways independent of PKC-zeta must exist.
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Affiliation(s)
- S Carlin
- Department of Pharmacology, University of Sydney, New South Wales, Australia
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219
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Kang Y, Park JS, Kim SH, Shin YJ, Kim W, Joo HJ, Chun JS, Kim HJ, Ha MJ. Overexpression of protein kinase C delta represses expression of proliferin in NIH3T3 cells that regulates cell proliferation. MOLECULAR CELL BIOLOGY RESEARCH COMMUNICATIONS : MCBRC 2000; 4:181-7. [PMID: 11281734 DOI: 10.1006/mcbr.2001.0276] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Protein kinase C (PKC) delta is known to inhibit proliferation of many cell types. In this study we found that overexpression of PKCdelta reduced proliferation of NIH3T3 cells. To identify specific genes regulated by PKCdelta in regulation of cell proliferation, we used differential display-polymerase chain reaction in PKCdelta-overexpressing NIH3T3 cells and found that the expression of proliferin, a secreted protein known to stimulate cell proliferation, was significantly repressed. Transient transfection study indicated that the repression of proliferin expression was inversely proportional to the expression levels of PKCdelta. Addition of an anti-proliferin antibody to culture medium to neutralize the secreted proliferin decreased cell proliferation in a dose-dependent manner. Our results, therefore, suggest that overexpression of PKCdelta induces transcriptional repression of proliferin, thereby resulting in inhibition of cell proliferation.
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Affiliation(s)
- Y Kang
- Institute for Medical Sciences, Ajou University School of Medicine, Suwon 442-721, Korea
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220
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Meinhardt G, Roth J, Hass R. Activation of protein kinase C relays distinct signaling pathways in the same cell type: differentiation and caspase-mediated apoptosis. Cell Death Differ 2000; 7:795-803. [PMID: 11042674 DOI: 10.1038/sj.cdd.4400709] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Activation of PKC with 5 nM 12-O-tetradecanoylphorbol-13-acetate (TPA) for 72 h in human U937 myeloid leukemia cells is associated with induction of adherence, followed by monocytic differentiation and G0/G1 cell cycle arrest. In this study, we demonstrate that in addition to these effects about 25% of U937 cells accumulated in an apoptotic subG1 phase after TPA treatment. The appearance of these apoptotic suspension cells was detectable throughout the time course of the culture and was independent of TPA concentrations between 0.5 and 500 nM. Experiments with cells synchronized by centrifugal elutriation revealed dominant susceptibility of G1-phase cells to TPA-mediated apoptosis. While adherent cells expressed differentiation markers including the integrin CD11c, this effect was less pronounced in the TPA-treated suspension fraction. Moreover, previous work has demonstrated cell cycle arrest in differentiating U937 cells. Accordingly, PKC activation by TPA treatment was associated with a significant expression of the cdk/cyclin inhibitor p21WAF/CIP/sdi-1 in the adherent population and subsequent G0/G1 cell cycle arrest. In contrast, suspension cells failed to induce significant levels of p21WAF/CIP/sdi-1 after TPA stimulation. Immunoblotting experiments demonstrated no difference in the expression of the pro-apoptotic factors Bax, Bad, and Bak in either control U937 and TPA-treated adherent or suspension cells, respectively. However, anti-apoptotic factors including Bcl-2, Bcl-xL, and Mcl-1 were significantly induced in the adherent population whereas no induction was detectable in the suspension cells. In this context, incubation with the caspase-3/caspase-7 specific tetrapeptide inhibitor DEVD prior to TPA treatment prevented an accumulation of cells in subG1, respectively, demonstrating an involvement of these caspases. Taken together, these data suggest that PKC activation can relay distinct signaling pathways such as induction of adherence coupled with monocytic differentiation and growth arrest, or induction of caspase-mediated apoptosis coupled with the failure to adhere and to differentiate.
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Affiliation(s)
- G Meinhardt
- Medizinische Klinik Innenstadt, Department of Hematology/Oncology, Ludwig-Maximilians-University, Ziemssenstrasse 1, 80336 Munich, Germany.
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221
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Clarke H, Ginanni N, Soler AP, Mullin JM. Regulation of protein kinase C-delta and -epsilon isoforms by phorbol ester treatment of LLC-PK1 renal epithelia. Kidney Int 2000; 58:1004-15. [PMID: 10972665 DOI: 10.1046/j.1523-1755.2000.00258.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND LLC-PK1 renal epithelia are a widely used model for proximal tubular physiology and differentiation. Protein kinase C (PKC) has been observed to play a role in both processes. This study examines the subcellular distribution and down-regulation of PKC-delta and PKC-epsilon isoforms in phorbol ester-treated LLC-PK1 epithelia. METHODS Cells were treated with 10-7 mol/L 12-O-tetradecanoyl phorbol 13-acetate (TPA) for up to seven days and were extracted as total cell lysates as well as cytosolic, membrane-associated (Triton-X soluble) and a third (Triton-X insoluble) fraction. The expression and cellular localization of PKC-delta and PKC-epsilon isoforms were then detected using Western immunoblot and immunofluorescence. RESULTS Based on the use of an anti-PKC-delta monoclonal antibody, TPA was observed to cause a rapid decrease in total PKC-delta content, which then returned to near control levels by seven days of treatment. Immunofluorescence indicated that PKC-delta had a cytoskeletal localization within the cells, and a subtle cytoskeletal rearrangement occurred upon exposure to TPA. Western immunoblots showed that PKC-delta did not undergo the expected membrane translocation upon activation by TPA, but simply disappeared immediately from the cytosolic compartment. Conventional cell fractionation procedures such as homogenization and Triton extraction prior to Western immunoblot will, however, fail to evaluate completely PKC-delta in LLC-PK1 epithelia because of the highly stringent measures necessary to extract PKC-delta from the cytoskeletal compartment of these cells. Furthermore, we observed that a second (polyclonal) PKC-delta antibody may recognize phosphorylated forms of PKC-delta, which went unrecognized by the other antibody. PKC-epsilon was present in the cytosol, membrane, and Triton-X-insoluble fractions of the cells. TPA treatment resulted in a partial translocation of PKC-epsilon to both the membrane and Triton-X-insoluble fractions of the cell, but total PKC-epsilon remained essentially unchanged. CONCLUSIONS The present data indicate that the localization of PKC-delta and subsequent redistribution within the LLC-PK1 cells in response to TPA treatment is highly unique and distinct from that of PKC-epsilon and PKC-alpha. An important methodological finding is that one given antibody may not recognize all phosphoproteins of a given PKC isoform.
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Affiliation(s)
- H Clarke
- Lankenau Medical Research Center, Wynnewood, Pennsylvania, USA.
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222
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Corbit KC, Soh JW, Yoshida K, Eves EM, Weinstein IB, Rosner MR. Different protein kinase C isoforms determine growth factor specificity in neuronal cells. Mol Cell Biol 2000; 20:5392-403. [PMID: 10891480 PMCID: PMC85991 DOI: 10.1128/mcb.20.15.5392-5403.2000] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Although mitogenic and differentiating factors often activate a number of common signaling pathways, the mechanisms leading to their distinct cellular outcomes have not been elucidated. In a previous report, we demonstrated that mitogen-activated protein (MAP) kinase (ERK) activation by the neurogenic agents fibroblast growth factor (FGF) and nerve growth factor is dependent on protein kinase Cdelta (PKCdelta), whereas MAP kinase activation in response to the mitogen epidermal growth factor (EGF) is independent of PKCdelta in rat hippocampal (H19-7) and pheochromocytoma (PC12) cells. We now show that EGF activates MAP kinase through a PKCzeta-dependent pathway involving phosphatidylinositol 3-kinase and PDK1 in H19-7 cells. PKCzeta, like PKCdelta, acts upstream of MEK, and PKCzeta can potentiate Raf-1 activation by EGF. Inhibition of PKCzeta also blocks EGF-induced DNA synthesis as monitored by bromodeoxyuridine incorporation in H19-7 cells. Finally, in embryonic rat brain hippocampal cell cultures, inhibitors of PKCzeta or PKCdelta suppress MAP kinase activation by EGF or FGF, respectively, indicating that these factors activate distinct signaling pathways in primary as well as immortalized neural cells. Taken together, these results implicate different PKC isoforms as determinants of growth factor signaling specificity within the same cell. Furthermore, these data provide a mechanism whereby different growth factors can differentially activate a common signaling intermediate and thereby generate biological diversity.
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Affiliation(s)
- K C Corbit
- Neurobiology, Pharmacology and Physiology Department and Ben May Institute for Cancer Research, University of Chicago, Chicago, Illinois 60637, USA
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223
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Maasch C, Wagner S, Lindschau C, Alexander G, Buchner K, Gollasch M, Luft FC, Haller H. Protein kinase Cα targeting is regulated by temporal and spatial changes in intracellular free calcium concentration [Ca
2+
]
i. FASEB J 2000. [DOI: 10.1096/fj.99-0403com] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Christian Maasch
- Franz Volhard Clinic and the Max‐Delbrück Center for Molecular MedicineMedizinische Fakultät der ChariteHumboldt University of BerlinGermany
| | - Stefan Wagner
- Institute of BiochemistryFree UniversityBerlinGermany
| | | | | | - Klaus Buchner
- Institute of BiochemistryFree UniversityBerlinGermany
| | - Maik Gollasch
- Franz Volhard Clinic and the Max‐Delbrück Center for Molecular MedicineMedizinische Fakultät der ChariteHumboldt University of BerlinGermany
| | - Friedrich C. Luft
- Franz Volhard Clinic and the Max‐Delbrück Center for Molecular MedicineMedizinische Fakultät der ChariteHumboldt University of BerlinGermany
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224
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Hussaini IM, Karns LR, Vinton G, Carpenter JE, Redpath GT, Sando JJ, VandenBerg SR. Phorbol 12-myristate 13-acetate induces protein kinase ceta-specific proliferative response in astrocytic tumor cells. J Biol Chem 2000; 275:22348-54. [PMID: 10806212 DOI: 10.1074/jbc.m003203200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein kinase C (PKC) activation has been implicated in cellular proliferation in neoplastic astrocytes. The roles for specific PKC isozymes in regulating this glial response, however, are not well understood. The aim of this study was to characterize the expression of PKC isozymes and the role of PKC-eta expression in regulating cellular proliferation in two well characterized astrocytic tumor cell lines (U-1242 MG and U-251 MG) with different properties of growth in cell culture. Both cell lines expressed an array of conventional (alpha, betaI, betaII, and gamma) and novel (theta and epsilon) PKC isozymes that can be activated by phorbol myristate acetate (PMA). Another novel PKC isozyme, PKC-eta, was only expressed by U-251 MG cells. In contrast, PKC-delta was readily detected in U-1242 MG cells but was present only at low levels in U-251 MG cells. PMA (100 nm) treatment for 24 h increased cell proliferation by over 2-fold in the U-251 MG cells, whereas it decreased the mitogenic response in the U-1242 MG cells by over 90%. When PKC-eta was stably transfected into U-1242 MG cells, PMA increased cell proliferation by 2.2-fold, similar to the response of U-251 MG cells. The cell proliferation induced by PMA in both the U-251 MG and U-1242-PKC-eta cells was blocked by the PKC inhibitor bisindolylmaleimide (0.5 micrometer) and the MEK inhibitor, PD 98059 (50 micrometer). Transient transfection of wild type U-251 with PKC-eta antisense oligonucleotide (1 micrometer) also blocked the PMA-induced increase in [(3)H]thymidine incorporation. The data demonstrate that two glioblastoma lines, with functionally distinct proliferative responses to PMA, express different novel PKC isozymes and that the differential expression of PKC-eta plays a determining role in the different proliferative capacity.
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Affiliation(s)
- I M Hussaini
- Departments of Pathology (Neuropathology), Biomedical Engineering, and Pharmacology, University of Virginia, Charlottesville, Virginia 22908, USA.
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225
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Yokoi T, Ohmichi M, Tasaka K, Kimura A, Kanda Y, Hayakawa J, Tahara M, Hisamoto K, Kurachi H, Murata Y. Activation of the luteinizing hormone beta promoter by gonadotropin-releasing hormone requires c-Jun NH2-terminal protein kinase. J Biol Chem 2000; 275:21639-47. [PMID: 10787426 DOI: 10.1074/jbc.m910252199] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Regulation of the mitogen-activated protein kinase (MAPK) family by gonadotropin-releasing hormone (GnRH) in the gonadotrope cell line LbetaT2 was investigated. Treatment with gonadotropin-releasing hormone agonist (GnRHa) activates extracellular signal-regulated kinase (ERK) and c-Jun NH(2)-terminal kinase (JNK). Activation of ERK by GnRHa occurred within 5 min, and declined thereafter, whereas activation of JNK by GnRHa occurred with a different time frame, i.e. it was detectable at 5 min, reached a plateau at 30 min, and declined thereafter. GnRHa-induced ERK activation was dependent on protein kinase C or extracellular and intracellular Ca(2+), whereas GnRHa-induced JNK activation was not dependent on protein kinase C or on extracellular or intracellular Ca(2+). To determine whether a mitogen-activated protein kinase family cascade regulates rat luteinizing hormone beta (LHbeta) promoter activity, we transfected the rat LHbeta (-156 to +7)-luciferase construct into LbetaT2 cells. GnRH activated the rat LHbeta promoter activity in a time-dependent manner. Neither treatment with a mitogen-activated protein kinase/ERK kinase (MEK) inhibitor, PD98059, nor cotransfection with a catalytically inactive form of a mitogen-activated protein kinase construct inhibited the induction of the rat LHbeta promoter by GnRH. Furthermore, cotransfection with a dominant negative Ets had no effect on the response of the rat LHbeta promoter to GnRH. On the other hand, cotransfection with either dominant negative JNK or dominant negative c-Jun significantly inhibited the induction of the rat LHbeta promoter by GnRH. In addition, GnRH did not induce either the rat LHbeta promoter activity in LbetaT2 cells transfected stably with dominant negative c-Jun. These results suggest that GnRHa differentially activates ERK and JNK, and a JNK cascade is necessary to elicit the rat LHbeta promoter activity in a c-Jun-dependent mechanism in LbetaT2 cells.
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Affiliation(s)
- T Yokoi
- Department of Obstetrics and Gynecology, Osaka University Medical School, 2-2, Yamadaoka, Suita, Osaka 565-0871, Japan
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226
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Dammeier S, Lovric J, Eulitz M, Kolch W, Mushinski JF, Mischak H. Identification of the smooth muscle-specific protein, sm22, as a novel protein kinase C substrate using two-dimensional gel electrophoresis and mass spectrometry. Electrophoresis 2000; 21:2443-53. [PMID: 10939458 DOI: 10.1002/1522-2683(20000701)21:12<2443::aid-elps2443>3.0.co;2-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We report a novel method to identify protein kinase C (PKC) substrates. Tissue lysates were fractionated by ion exchange chromatography and used as substrates in in vitro kinase reactions. The phosphorylated proteins were separated using two-dimensional gel electrophoresis. Spots that contained isolated phosphoproteins were excised and digested with trypsin. The tryptic peptides were analyzed using mass spectrometry. While several of the proteins identified using this technique represent known PKC substrates, we identified a new PKC substrate in the initial screen. This protein, sm22, is expressed in smooth muscle cells and served well as a substrate for PKC in vitro. Sm22 is predominantly associated with the actin cytoskeleton. Upon activation of PKC in vivo, sm22 dissociates from the actin cytoskeleton and is distributed diffusely in the cytoplasm. Our data strongly suggest that phosphorylation by PKC controls the intracellular localization of sm22. This demonstrates that our approach, using a complex mixture of proteins as in vitro kinase substrates and subsequently identifying the newly phosphorylated proteins by mass spectrometry, is a powerful method to identify new kinase substrates.
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Affiliation(s)
- S Dammeier
- Institut für Klinische Molekularbiologie, GSF München, Germany.
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227
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Koren R, Langzam L, Paz A, Livne PM, Gal R, Sampson SR. Protein kinase C (PKC) isoenzymes immunohistochemistry in lymph node revealing solution-fixed, paraffin-embedded bladder tumors. Appl Immunohistochem Mol Morphol 2000; 8:166-71. [PMID: 10937066 DOI: 10.1097/00129039-200006000-00013] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Protein kinase C (PKC) plays an important role in cellular differentiation and in the malignant process. In an earlier study, it was shown that the expression pattern of PKC isoenzymes is altered in some tumors compared to their corresponding normal tissue. In this study, we evaluated the pattern of PKC isoenzyme immunostaining in bladder transitional cell carcinoma (TCC) of different grades and stages and normal tissue. Twenty-seven TCC samples and six areas of normal bladder mucosa were stained with antibodies specific for the PKC isoenzymes: alpha, beta 1, beta 2, delta, and zeta. The sections were scored for intensity of staining, and the correlation with grade and stage of the tumors was computed. The PKC alpha and beta 2 immunostains were intense in normal urothelium and in all evaluated tumors. PKC beta 1 and delta stains were intense in normal and low-grade and -stage tumors and weak in high-grade and -stage tumors. The opposite trend was found for PKC zeta. PKC isoenzyme expression differs in invasive TCC compared to low-grade, low-stage TCC and normal urothelium. The value of these findings as a marker of tumor aggressiveness should be further assessed.
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Affiliation(s)
- R Koren
- Department of Pathology, Hasharon Hospital, Petah Tikva, Israel
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228
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Abstract
In addition to the well-characterized interaction with classical and novel protein kinase C (PKC) isozymes, the phorbol ester tumor promoters bind to other receptors lacking kinase activity. Among these novel phorbol ester receptors, two families of proteins may play a role in the regulation of cell growth and malignant transformation: chimaerins and ras guanyl-releasing protein (ras-GRP). These proteins possess a single copy of the C1 domain that is involved in binding of phorbol esters and the lipid second messenger diacylglycerol. Four isoforms of chimaerins (alpha1-, alpha2-, beta1-, and beta2-chimaerins) have been isolated to-date, all of them possessing GTPase-activating protein activity for Rac, a small GTP-binding protein that controls actin cytoskeleton organization, cell-cycle progression, adhesion, and migration. Ras-GRP is a guanine nucleotide exchange factor for ras and promotes malignant transformation in fibroblasts in a phorbol ester-dependent manner. The C1 domain in Ras-GRP may, therefore, have a dominant role in Ras-GRP activation and is essential for phorbol ester-dependent activation of downstream effectors of ras, i.e., the mitogen-activated protein kinase cascade. Thus, a novel concept emerges in which phorbol esters may exert cellular responses through pathways not involving phorbol ester-responsive PKC isozymes. The discovery of "nonPKC" phorbol ester receptors adds an additional level of complexity to the understanding of phorbol ester effects and the molecular mechanisms of carcinogenesis.
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Affiliation(s)
- M G Kazanietz
- Center for Experimental Therapeutics and Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia 19104-6160, USA
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229
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Spina A, Chiosi E, Naviglio S, Pagano M, Illiano G, Marchese M, Spena SR, Buommino E, Morelli F, Metafora S. Treatment of v-Ki-ras-transformed SVC1 cells with low retinoic acid induces malignancy reversion associated with ras p21 down-regulation. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1496:285-95. [PMID: 10771097 DOI: 10.1016/s0167-4889(00)00032-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The effect of nontoxic, low concentrations (10(-8) M) of retinoic acid (RA) for a relatively long time (28 days) on a Kirsten ras-virus transformed cell line (Ki-SVC1), derived from the rat seminal vesicle epithelium, was investigated. In these experimental conditions, the cell treatment with RA induced a decrease of the proliferation rate, apoptosis and a marked reduction of both anchorage-independent growth and tumorigenicity. These biological responses were either preceded or associated with important changes in adenylate cyclase/protein kinase C signaling pathways, the activation of important apoptosis-linked genes and a marked decrease of the v-Ki-ras p21 protein. The significance of these findings is discussed.
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Affiliation(s)
- A Spina
- Department of Biochemistry and Biophysics, Second University of Naples, Via Costantinopoli 16, 80138, Naples, Italy
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230
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Sun X, Wu F, Datta R, Kharbanda S, Kufe D. Interaction between protein kinase C delta and the c-Abl tyrosine kinase in the cellular response to oxidative stress. J Biol Chem 2000; 275:7470-3. [PMID: 10713049 DOI: 10.1074/jbc.275.11.7470] [Citation(s) in RCA: 173] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein kinase C (PKC) isoforms are phosphorylated on tyrosine in the response of cells to oxidative stress. The present studies demonstrate that treatment of cells with hydrogen peroxide (H(2)O(2)) induces binding of the PKCdelta isoform and the c-Abl protein-tyrosine kinase. The results show that c-Abl phosphorylates PKCdelta in the H(2)O(2) response. We also show that PKCdelta phosphorylates and activates c-Abl in vitro. In cells, induction of c-Abl activity by H(2)O(2) is attenuated by the PKCdelta inhibitor, rottlerin, and by overexpression of the regulatory domain of PKCdelta. These findings support a functional interaction between PKCdelta and c-Abl in the cellular response to oxidative stress.
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Affiliation(s)
- X Sun
- Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA
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231
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Fujii T, García-Bermejo ML, Bernabó JL, Caamaño J, Ohba M, Kuroki T, Li L, Yuspa SH, Kazanietz MG. Involvement of protein kinase C delta (PKCdelta) in phorbol ester-induced apoptosis in LNCaP prostate cancer cells. Lack of proteolytic cleavage of PKCdelta. J Biol Chem 2000; 275:7574-82. [PMID: 10713064 DOI: 10.1074/jbc.275.11.7574] [Citation(s) in RCA: 159] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phorbol esters, the activators of protein kinase C (PKC), induce apoptosis in androgen-sensitive LNCaP prostate cancer cells. The role of individual PKC isozymes as mediators of this effect has not been thoroughly examined to date. To study the involvement of the novel isozyme PKCdelta, we used a replication-deficient adenovirus (PKCdeltaAdV), which allowed for a tightly controlled expression of PKCdelta in LNCaP cells. A significant reduction in cell number was observed after infection of LNCaP cells with PKCdeltaAdV. Overexpression of PKCdelta markedly enhanced the apoptotic effect of phorbol 12-myristate 13-acetate in LNCaP cells. PKCdelta-mediated apoptosis was substantially reduced by the pan-caspase inhibitor z-VAD and by Bcl-2 overexpression. Importantly, and contrary to other cell types, PKCdelta-mediated apoptosis does not involve its proteolytic cleavage by caspase-3, suggesting that allosteric activation of PKCdelta is sufficient to trigger apoptosis in LNCaP cells. In addition, phorbol ester-induced apoptosis was blocked by a kinase-deficient mutant of PKCdelta, supporting the concept that PKCdelta plays an important role in the regulation of apoptotic cell death in LNCaP prostate cancer cells.
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Affiliation(s)
- T Fujii
- Center for Experimental Therapeutics and Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6160, USA
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232
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Dal Pra I, Whitfield JF, Chiarini A, Armato U. Increased activity of the protein kinase C-delta holoenzyme in the cytoplasmic particulate fraction precedes the activation of caspases in polyomavirus-transformed pyF111 rat fibroblasts exposed to calphostin C or topoisomerase-II inhibitors. Exp Cell Res 2000; 255:171-83. [PMID: 10694433 DOI: 10.1006/excr.1999.4789] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A caspase-mediated release of the 40-kDa catalytic fragment of the delta isoform (CF-delta) of protein kinase C (PKC-delta) is involved in apoptosis, but its actual role in apoptosis development is still unknown. In an effort to understand this role, we have used polyomavirus-transformed pyF111 rat fibroblasts, which are hypersusceptible to apoptosis as they constitutively hyperexpress PKC-delta, but cannot make the antiapoptotic Bcl-2 and Bcl-X(L) proteins, while making the proapoptotic Bax protein. Calphostin C is reportedly both a specific inhibitor of PKC-delta activity (C. Keenan, N. Goode, and C. Pears, 1997, FEBS Lett. 415, 101-108) and an effective apoptogen (M. Murata et al., 1997, Cell. Mol. Life Sci. 53, 737-743). Exposure of pyF111 cells to calphostin C (75 nM) stimulated the translocation of the PKC-delta holoenzyme (holo-PKC-delta) onto the cytoplasmic particulate (CP) fraction between 15 and 45 min, which was after the release of mitochondrial cytochrome c but before the activation of cytoplasmic DEVD-specific caspases. The CF-delta fragment started accumulating only between 2 and 4 h, while apoptosis occurred mostly within 6 h. Incubating pyF111 cells with the much slower acting, apoptogenic topoisomerase-II inhibitors etoposide (VP-16) and teniposide (VM-26) also caused within 6 h a doubling of the CP-bound holo-PKC-delta-related activity but with no significant translocation of the holoenzyme to the CP fraction. Again this occurred after the release of cytochrome c but before the activation of DEVDases and the accumulation of the CF-delta. However, while calphostin C did not affect the delta-related activity in the nuclear membrane (NM) and nucleoplasmic (NP) fractions, VP-16 and VM-26 caused a prompt, large, and irreversible drop in the delta activity at the NM and a transient surge followed by a fall in the NP-associated activity. Hence, a surge of CP-anchored holo-PKC-delta activity is a common part of the signals given by various apoptogenic drugs to pyF111 cells. On the other hand, inhibition of delta-related activity, first at the NM and then in the NP fraction, is a specific feature only of the signals given by apoptogenic DNA-damaging agents.
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Affiliation(s)
- I Dal Pra
- Histology & Embryology Unit, University of Verona, Verona, I-37134, Italy
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233
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Kurkinen KM, Keinänen RA, Karhu R, Koistinaho J. Genomic structure and chromosomal localization of the rat protein kinase Cdelta-gene. Gene 2000; 242:115-23. [PMID: 10721703 DOI: 10.1016/s0378-1119(99)00539-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Protein kinase Cdelta (PKCdelta) is a widely expressed calcium-independent PKC isozyme that is induced at mRNA and protein levels upon stimulation of different cellular pathways. We found the rat PKCdelta gene to consist of 19 exons and to span approximately 29 kb. The exon-intron junctions follow the GT/AG rule. The 5' untranslated region is nearly 12 kb in length, and the transcription initiation site is surrounded by CG-rich sequences. The 5' flanking region contains putative binding sites for activator protein 1 (AP-1), nuclear factor kappa B (NFkappaB), stimulatory protein-1 (Sp-1) and nerve growth factor induced-C (NGFI-C) transcription factors. The PKCdelta gene is localized at the rat chromosome 19p14. The cloned gene will help to elucidate the role of PKCdelta in growth, differentiation and death of mammalian cells.
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Affiliation(s)
- K M Kurkinen
- A.I. Virtanen Institute for Molecular Sciences, University of Kuopio, Finland
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234
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235
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Zhuang S, Hirai SI, Ohno S. Hyperosmolality induces activation of cPKC and nPKC, a requirement for ERK1/2 activation in NIH/3T3 cells. Am J Physiol Cell Physiol 2000; 278:C102-9. [PMID: 10644517 DOI: 10.1152/ajpcell.2000.278.1.c102] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Protein kinase C (PKC) has been reported to be associated with the activation of extracellular signal-regulated kinase (ERK) by hyperosmolality. However, it is unclear whether hyperosmolality induces PKC activation and which PKC isoforms are involved in ERK activation. In this study, we demonstrate that NaCl increases total PKC activity and induces PKCalpha, PKCdelta, and PKCepsilon translocation from the cytosol to the membrane in NIH/3T3 cells, suggesting that hyperosmotic stress activates conventional PKC (cPKC) and novel PKC (nPKC). Further studies show that NaCl-inducible ERK1 and ERK2 (ERK1/2) activation is a consequence of cPKC and nPKC activation, because either downregulation with 12-O-tetradecanoylphorbol 13-acetate or selective inhibition of cPKC and nPKC by GF-109203X and rottlerin largely inhibited the stimulation of ERK1/2 phosphorylation by NaCl. In addition, we show that NaCl increases diacylglycerol (DAG) levels and that a phospholipase C (PLC) inhibitor, U-73122, inhibits NaCl-induced ERK1/2 phosphorylation. These results, together, suggest that a hyperosmotic NaCl-induced signaling pathway that leads to activation of ERK1/2 may sequentially involve PLC activation, DAG release, and cPKC and nPKC activation.
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Affiliation(s)
- S Zhuang
- Department of Molecular Biology, Yokohama City University School of Medicine, Kanazawa-Ku, Yokohama 236, Japan
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236
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Schmidt A, Vlodavsky I, Völker W, Buddecke E. Differentiation of coronary smooth muscle cells to a cell cycle-arrested hypertrophic growth status by a synthetic non-toxic heparin-mimicking compound. Atherosclerosis 1999; 147:387-97. [PMID: 10559525 DOI: 10.1016/s0021-9150(99)00209-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Studies on the mode of action of basic fibroblast growth factor (bFGF) identified an essential role of heparan sulfate and heparin-like molecules in the formation of distinct bFGF-heparan sulfate-bFGF-receptor complexes that are required for bFGF-induced signal transduction. In coronary smooth muscle cells that express 6-8 ng bFGF mg(-1) cell protein, the heparan sulfate chains of membrane-associated proteoheparan sulfate are implicated in bFGF signaling and thus are involved in the regulation of proliferation and differentiation of vascular smooth muscle cells. We studied the mode of action of a synthetic non-sulfated heparin-mimicking compound termed RG-13,577 (poly-4-hydroxyphenoxy acetic acid, Mr approximately 5 kD) and found a dose-dependent antiproliferative effect that was characterized by a block of G(1)/S-phase transition indicated by a marked (80%) reduction of [3H]thymidine incorporation at a concentration of 5 microg ml(-1) RG-13,577. Cell cycle analysis showed a block of cell division in the G(1)-phase. In response to RG-13,577 the cells were converted into a hypertrophic growth status within 72 h as judged from a doubling of the cellular protein content and measurement of cell and nucleus size. The increased cell protein content resulted from a de novo synthesis and was also associated with an increase in the incorporation of [35S]sulfate into cell-associated proteoglycans, including the proteoheparan sulfate coreceptor of bFGF. In contrast, the compound-induced G(1)-phase arrest was associated with an extensive downregulation of the cellular and pericellular bFGF level. The reduced bFGF content was accompanied by downregulation of the bFGF signaling-involved protein kinase C-alpha and MAP kinase, abrogation of MAP kinase phosphorylation and overexpression of protein kinase C-gamma. RG-13,577 failed to elicit apoptotic reactions at a concentration range of 0.5-10 microg ml(-1) and its effect was reversible upon removal of the compound. It appears that RG-13,577 induces a phenotype transformation of coronary SMC into a metabolically active hypertrophic status that could promote repair processes after balloon angioplasty (PTCA) without stimulating cell proliferation. Development of non-toxic polyanionic compounds may provide an effective strategy to inhibit cell proliferation associated with restenosis following balloon angioplasty and coronary artery bypass surgery.
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Affiliation(s)
- A Schmidt
- Institute for Arteriosclerosis Research, University of Muenster, Domagkstrasse 3, D-48149, Muenster, Germany.
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237
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Garcia-Huidobro T, Valenzuela E, Leisewitz AV, Valderrama J, Bronfman M. Anti-proliferative effect of two novel palmitoyl-carnitine analogs, selective inhibitors of protein kinase C conventional isoenzymes. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 266:855-64. [PMID: 10583379 DOI: 10.1046/j.1432-1327.1999.00923.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Previous studies have shown that palmitoyl-carnitine is an anti-proliferative agent and a protein kinase C inhibitor. Two new palmitoyl-carnitine analogs were synthesized by replacing the ester bond with a metabolically more stable ether bond. An LD50 value in the nM range was found in anti-proliferative assays using HL-60 cells and was dependent on the alkyl-chain length. The inhibitory action of these water-soluble compounds on protein kinase C in vitro was greatly increased with respect to palmitoyl-carnitine and was dependent on the length of the alkyl chain. Its effect was mediated by an increase in the enzyme's requirement for phosphatidylserine. Inhibition of the in situ phosphorylation of a physiological platelet protein kinase C substrate and of phorbol ester-induced differentiation of HL-60 cells was also observed. Finally, to test for isoenzyme selectivity, several human recombinant protein kinase C isoforms were used. Only the Ca2+-dependent classic protein kinase Cs (alpha, betaIota, betaIotaIota and gamma) were inhibited by these compounds, yet the activities of casein kinase I, Ca2+/calmodulin-dependent kinase and cAMP-dependent protein kinase were unaffected. Thus, these novel inhibitors appear to be both protein kinase C and isozyme selective. They may be useful in assessing the individual roles of protein kinase C isoforms in cell proliferation and tumor development and may be rational candidates for anti-neoplasic drug design.
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Affiliation(s)
- T Garcia-Huidobro
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas y Facultad de Química, P. Universidad Católica de Chile, Santiago, Chile
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238
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Li L, Lorenzo PS, Bogi K, Blumberg PM, Yuspa SH. Protein kinase Cdelta targets mitochondria, alters mitochondrial membrane potential, and induces apoptosis in normal and neoplastic keratinocytes when overexpressed by an adenoviral vector. Mol Cell Biol 1999; 19:8547-58. [PMID: 10567579 PMCID: PMC84974 DOI: 10.1128/mcb.19.12.8547] [Citation(s) in RCA: 223] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/1999] [Accepted: 08/19/1999] [Indexed: 11/20/2022] Open
Abstract
Inactivation of protein kinase Cdelta (PKCdelta) is associated with resistance to terminal cell death in epidermal tumor cells, suggesting that activation of PKCdelta in normal epidermis may be a component of a cell death pathway. To test this hypothesis, we constructed an adenovirus vector carrying an epitope-tagged PKCdelta under a cytomegalovirus promoter to overexpress PKCdelta in normal and neoplastic keratinocytes. While PKCdelta overexpression was detected by immunoblotting in keratinocytes, the expression level of other PKC isozymes, including PKCalpha, PKCepsilon, PKCzeta, and PKCeta, did not change. Calcium-independent PKC-specific kinase activity increased after infection of keratinocytes with the PKCdelta adenovirus. Activation of PKCdelta by 12-O-tetradecanoylphorbol-13-acetate (TPA) at a nanomolar concentration was lethal to normal and neoplastic mouse and human keratinocytes overexpressing PKCdelta. Lethality was inhibited by PKC selective inhibitors, GF109203X and Ro-32-0432. TPA-induced cell death was apoptotic as evidenced by morphological criteria, TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling) assay, DNA fragmentation, and increased caspase activity. Subcellular fractionation indicated that PKCdelta translocated to a mitochondrial enriched fraction after TPA activation, and this finding was confirmed by confocal microscopy of cells expressing a transfected PKCdelta-green fluorescent protein fusion protein. Furthermore, activation of PKCdelta in keratinocytes altered mitochondrial membrane potential, as indicated by rhodamine-123 fluorescence. Mitochondrial inhibitors, rotenone and antimycin A, reduced TPA-induced cell death in PKCdelta-overexpressing keratinocytes. These results indicate that PKCdelta can initiate a death pathway in keratinocytes that involves direct interaction with mitochondria and alterations of mitochondrial function.
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Affiliation(s)
- L Li
- Laboratory of Cellular Carcinogenesis and Tumor Promotion, Division of Basic Science, National Cancer Institute, Bethesda, Maryland 20892, USA
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239
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Cooper DR, Watson JE, Patel N, Illingworth P, Acevedo-Duncan M, Goodnight J, Chalfant CE, Mischak H. Ectopic expression of protein kinase CbetaII, -delta, and -epsilon, but not -betaI or -zeta, provide for insulin stimulation of glucose uptake in NIH-3T3 cells. Arch Biochem Biophys 1999; 372:69-79. [PMID: 10562418 DOI: 10.1006/abbi.1999.1472] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Insulin regulates a diverse array of signaling pathways involved in the control of growth, differentiation, proliferation, and metabolism. Insulin increases in glucose uptake via a protein kinase C-dependent pathway in target tissues such as fat and muscle are well documented. Insulin-regulated events, however, occur in all cells. The utilization of glucose as a preferred energy source is a ubiquitous event in eukaryotic cells. In NIH-3T3 fibroblasts, insulin treatment increased levels of the cPKC and nPKC activator, diacylglycerol. Insulin-responsive 2-[(3)H]deoxyglucose uptake was stimulated in a dose-dependent manner. The overexpression of protein kinase C (PKC)betaI, -betaII, -delta, -epsilon, and -zeta was used to investigate the specificity of PKC isozymes for insulin-sensitive glucose uptake. The stable overexpression of PKCbetaII, -delta, and -epsilon resulted in increases in insulin-stimulated 2-[(3)H]deoxyglucose uptake compared to vector control cells, while basal 2-deoxyglucose uptake levels were not elevated. Overexpression of PKCbetaI and PKCzeta isozymes had no further effect on basal or insulin-stimulated 2-deoxyglucose uptake. The PKC-specific inhibitor, CGP41251, blocked insulin effects on 2-deoxyglucose uptake but not its effects on tyrosine phosphorylation of cellular substrates. Insulin-stimulated 3-O-methylglucose uptake was also greater in cells overexpressing PKCbetaII, -delta, and -epsilon, compared to control cells. The increased responsiveness was not accompanied by conversion of 3T3 cells to the adipocyte phenotype or the increased expression of insulin receptors or glucose transporters (GLUT1-type). Insulin-stimulated recruitment of GLUT1 to plasma membranes of cells overexpressing PKCbetaII, -delta, and -epsilon, was greater than that in control cells. The data suggest that more than one PKC isozyme is involved in insulin signaling pathways in fibroblasts, resulting in increased GLUT1 transporter recruitment to cell membranes.
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Affiliation(s)
- D R Cooper
- James A. Haley Veterans Hospital, University of South Florida College of Medicine, Tampa, Florida, 33612, USA.
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240
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Kiley SC, Clark KJ, Duddy SK, Welch DR, Jaken S. Increased protein kinase C delta in mammary tumor cells: relationship to transformtion and metastatic progression. Oncogene 1999; 18:6748-57. [PMID: 10597283 DOI: 10.1038/sj.onc.1203101] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Relatively little is known about the molecular mechanisms of tumor promotion/progression in mammary carcinogenesis. Increased protein kinase C (PKC) activity is known to promote tumor formation in several tissues; however, its role in mammary carcinogenesis is not yet known. To determine if individual PKCs may selectively regulate properties of mammary tumor cells, we compared PKC isozyme levels in mammary tumor cell lines with low, moderate and high metastatic potential. All three cell lines expressed alpha, delta, epsilon and zeta PKCs; however, PKC delta levels were relatively increased in the highly metastatic cells. To determine if increased PKC delta could contribute to promotion/progression, we overexpressed PKC delta in the low and moderately metastatic cell lines. PKC delta overexpression had no significant effect on growth of adherent cells, but significantly increased anchorage-independent growth. Conversely, expressing the regulatory domain of PKC delta (RD delta), a putative PKC delta inhibitory fragment, inhibited anchorage-independent growth. The efficacy of RD delta as a PKC delta inhibitor was demonstrated by showing that RD delta selectively interfered with PKC delta subcellular location and significantly interfered with phosphorylation of the PKC cytoskeletal substrate, adducin. PKC-dependent phosphorylation of cytoskeletal substrate proteins, such as adducin, provides a mechanistic link between increased PKC delta activity and phenotypic changes in cytoskeletal-dependent processes such as migration and attachment, two processes that are relevant to metastatic potential. The reciprocal growth effects of expressing PKC delta and RD delta as gain and loss of function constructs, respectively, provide strong evidence that PKC delta regulates processes important for anchorage-independent growth in these mammary tumor cells.
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Affiliation(s)
- S C Kiley
- Adirondack Biomedical Research Institute, Inc., Lake Placid, NY 12946, USA
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241
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Tseng CP, Ely BD, Pong RC, Wang Z, Zhou J, Hsieh JT. The role of DOC-2/DAB2 protein phosphorylation in the inhibition of AP-1 activity. An underlying mechanism of its tumor-suppressive function in prostate cancer. J Biol Chem 1999; 274:31981-6. [PMID: 10542228 DOI: 10.1074/jbc.274.45.31981] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
DOC-2/DAB2, a novel phosphoprotein with signal-transducing capability, inhibits human prostatic cancer cells (Tseng, C.-P., Ely, B. D., Li, Y., Pong, R.-C., and Hsieh, J.-T. (1998) Endocrinology 139, 3542-3553). However, its mechanism of action is not understood completely. This study delineates the functional significance of DOC-2/DAB2 protein phosphorylation and demonstrates that in vivo activation of protein kinase C (PKC) by 12-O-tetradecanoylphorbol-13-acetate (TPA) induces DOC-2/DAB2 phosphorylation, including a serine residue at position 24. Mutation of Ser(24) to Ala reduced DOC-2/DAB2 phosphorylation by PKC. Using a synthetic Ser(24) peptide (APS(24)KKEKKKGSEKTD) or recombinant DOC-2/DAB2 as substrates, PKCbetaII, PKCgamma, and PKCdelta (but not casein kinase II) directly phosphorylated Ser(24) in vitro. This indicates that DOC-2/DAB2 is a PKC-specific substrate. Since expression of wild-type DOC-2/DAB2, but not the S24A mutant, inhibited TPA-induced AP-1 activity in prostatic epithelial cells, phosphorylation of Ser(24) appears to play a critical role in modulating TPA-induced AP-1 activity. Taken together, these data suggest that PKC-regulated phosphorylation of DOC-2/DAB2 protein may help its growth inhibitory function.
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Affiliation(s)
- C P Tseng
- Department of Urology, University of Texas Southwestern Medical Center, Dallas, Texas 75235-9110, USA
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242
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Konishi H, Matsuzaki H, Takaishi H, Yamamoto T, Fukunaga M, Ono Y, Kikkawa U. Opposing effects of protein kinase C delta and protein kinase B alpha on H(2)O(2)-induced apoptosis in CHO cells. Biochem Biophys Res Commun 1999; 264:840-6. [PMID: 10544018 DOI: 10.1006/bbrc.1999.1579] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
H(2)O(2)-induced apoptosis was enhanced in the CHO cell line overproducing protein kinase C delta (PKCdelta) as judged by DNA fragmentation. In response to the H(2)O(2) treatment, PKCdelta was tyrosine phosphorylated and recovered as a constitutively active form, but its proteolytic fragment was not generated. In contrast, H(2)O(2)-induced apoptosis was suppressed in the CHO cell line overexpressing protein kinase B alpha (PKBalpha). Consistently, phosphorylation of BAD, a pro-apoptotic protein negatively regulated by PKBalpha, was sustained in the cells overproducing PKBalpha, but was not changed in the cells overexpressing PKCdelta. In the CHO cell line overproducing both PKCdelta and PKBalpha, H(2)O(2)-induced tyrosine phosphorylation of PKCdelta was suppressed, and DNA fragmentation was diminished concomitantly. These results suggest that PKCdelta contributes to H(2)O(2)-induced apoptosis by a mechanism independent of BAD and that PKCdelta is a target of PKB for the regulation of cell survival.
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Affiliation(s)
- H Konishi
- Faculty of Science, Kobe University, Kobe, 657-8501, Japan
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243
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Hornia A, Lu Z, Sukezane T, Zhong M, Joseph T, Frankel P, Foster DA. Antagonistic effects of protein kinase C alpha and delta on both transformation and phospholipase D activity mediated by the epidermal growth factor receptor. Mol Cell Biol 1999; 19:7672-80. [PMID: 10523655 PMCID: PMC84804 DOI: 10.1128/mcb.19.11.7672] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Downregulation of protein kinase C delta (PKC delta) by treatment with the tumor-promoting phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) transforms cells that overexpress the non-receptor class tyrosine kinase c-Src (Z. Lu et al., Mol. Cell. Biol. 17:3418-3428, 1997). We extended these studies to cells overexpressing a receptor class tyrosine kinase, the epidermal growth factor (EGF) receptor (EGFR cells); like c-Src, the EGF receptor is overexpressed in several human tumors. In contrast with expectations, downregulation of PKC isoforms with TPA did not transform the EGFR cells; however, treatment with EGF did transform these cells. Since TPA downregulates all phorbol ester-responsive PKC isoforms, we examined the effects of PKC delta- and PKC alpha-specific inhibitors and the expression of dominant negative mutants for both PKC delta and alpha. Consistent with a tumor-suppressing function for PKC delta, the PKC delta-specific inhibitor rottlerin and a dominant negative PKC delta mutant transformed the EGFR cells in the absence of EGF. In contrast, the PKC alpha-specific inhibitor Go6976 and expression of a dominant negative PKC alpha mutant blocked the transformed phenotype induced by both EGF and PKC delta inhibition. Interestingly, both rottlerin and EGF induced substantial increases in phospholipase D (PLD) activity, which is commonly elevated in response to mitogenic stimuli. The elevation of PLD activity in response to inhibiting PKC delta, like transformation, was dependent upon PKC alpha and restricted to the EGFR cells. These data demonstrate that PKC isoforms alpha and delta have antagonistic effects on both transformation and PLD activity and further support a tumor suppressor role for PKC delta that may be mediated by suppression of tyrosine kinase-dependent increases in PLD activity.
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Affiliation(s)
- A Hornia
- Department of Biological Sciences, Hunter College of The City University of New York, New York, New York 10021, USA
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244
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Thiam K, Loing E, Zoukhri D, Rommens C, Hodges R, Dartt D, Verwaerde C, Auriault C, Gras-Masse H, Sergheraert C. Direct evidence of cytoplasmic delivery of PKC-alpha, -epsilon and -zeta pseudosubstrate lipopeptides: study of their implication in the induction of apoptosis. FEBS Lett 1999; 459:285-90. [PMID: 10526151 DOI: 10.1016/s0014-5793(99)01240-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Protein kinases C (PKC) are serine/threonine kinase enzymes involved in the mechanism of cell survival. Their pseudosubstrate sequences are autoinhibitory domains, which maintain the enzyme in an inactive state in the absence of allosteric activators, thus representing an attractive tool for the modulation of different PKC isoforms. Here, we report the use of palmitoylated modified PKC-alpha, -epsilon, and -zeta pseudosubstrate peptides, and determine their intracellular distribution together with their respective PKC isoenzymes. Finally, we propose that the differential distribution of the peptides is correlated with a selective induction of apoptosis and therefore argues for different involvement of PKC isoforms in the anti-apoptotic program.
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Affiliation(s)
- K Thiam
- UMR 8727, Lille II University, Institut de Biologie et Institut Pasteur de Lille, 1 rue du Pr. A. Calmette, P.O. Box 447, 59021, Lille, France.
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245
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Gil C, Pelliccioni P, Itarte E, Aguilera J. Differential action of nerve growth factor and phorbol ester TPA on rat synaptosomal PKC isoenzymes. Neurochem Int 1999; 35:281-91. [PMID: 10482348 DOI: 10.1016/s0197-0186(99)00076-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The subcellular redistribution of protein kinase C family members (alpha, beta, gamma, delta, epsilon and zeta isoforms) was examined in response to treatment with 12-O-tetradecanoyl-phorbol-13 acetate (TPA) or nerve growth factor (NGF) in a synaptosomal-enriched P2 fraction from rat brain. Treatment with TPA affected members of the classical-PKC family (alpha, beta and gamma), resulting in a final loss of total protein of each isoenzyme. The kinetics of changes of members of the novel-PKC family are different, the delta isoform being translocated, but not down-regulated, while the epsilon isoform showing only a slight diminishing of immunoreactivity in the soluble and particulate fractions. The atypical-PKC zeta isoform was not translocated in response to TPA. Incubation with NGF induced a loss of immunoreactivity of the cytosolic alpha, beta and epsilon isoforms, but the membrane fractions of these isoforms were not appreciably affected. In contrast, a marked translocation from cytosol to membrane was observed in the case of the gamma and delta isoforms. The zeta isoform presented a slight translocation from the particulate fraction to the soluble fraction. Thus, the results show that the effects of TPA and NGF on PKC isoforms are not coincident in synaptosomes, the 6 isoform being activated and not down-regulated by both treatments, whereas the gamma isoform is only down-regulated in the case of TPA, but presents sustained translocation with NGF, indicating that PKC isoform-specific degradation pathways exist in synaptic terminals. The effects of NGF on PKC isoforms coexist with an increase in NGF-induced polyphosphoinositide hydrolysis, suggesting the participation of phospholipases.
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Affiliation(s)
- C Gil
- Departament de Bioquímica i de Biologia Molecular, Facultat de Medicina, Universitat Autònoma de Barcelona, Spain
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246
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Weller SG, Klein IK, Penington RC, Karnes WE. Distinct protein kinase C isozymes signal mitogenesis and apoptosis in human colon cancer cells. Gastroenterology 1999; 117:848-57. [PMID: 10500067 DOI: 10.1016/s0016-5085(99)70343-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND & AIMS Protein kinase C (PKC) is a family of serine-threonine kinases that transmit signals from cell surface receptors. To determine if distinct PKC isozymes transmit proliferative and/or apoptotic signals in colon cancer cells, we examined the effects of 3 PKC agonists, phorbol 12-myristate 13 acetate (PMA), ingenol 3,20-dibenzoate (IDB), and bistratene A, and a selective PKC inhibitor, GF 109203X, on proliferation, apoptosis, and activation of individual PKC isozymes in 5 colon cancer cell lines. METHODS Effects were assayed by a formazan-based colorimetric assay, [(3)H]thymidine incorporation, fluorescent nuclear staining, annexin V binding, DNA fragmentation assay, and immunoblotting of cytoplasmic and membrane fractions for PKC isozymes. RESULTS Two cell lines, SNU-C1 and SNU-C4, showed proliferative responses to PMA (0.1-1 nmol/L) and IDB (10-1000 nmol/L) and marked apoptotic responses to PMA (>5 nmol/L) and bistratene A (>1 micromol/L). GF 109203X blocked proliferative and apoptotic effects of PMA with distinct IC(50)s. Proliferative concentrations of PMA and IDB caused translocation of PKCepsilon alone, whereas apoptotic concentrations of PMA and bistratene A induced translocation of PKCdelta. CONCLUSIONS Activation of PKCepsilon and PKCdelta triggers proliferative and apoptotic signals, respectively, in SNU-C4 colon cancer cells. These 2 isozymes may play important opposing roles in normal homeostasis and neoplastic transformation of the colorectal epithelium.
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Affiliation(s)
- S G Weller
- Colorectal Neoplasia Group, Division of Gastroenterology, Mayo Clinic, Rochester, Minnesota, USA
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247
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Knauf JA, Elisei R, Mochly-Rosen D, Liron T, Chen XN, Gonsky R, Korenberg JR, Fagin JA. Involvement of protein kinase Cepsilon (PKCepsilon) in thyroid cell death. A truncated chimeric PKCepsilon cloned from a thyroid cancer cell line protects thyroid cells from apoptosis. J Biol Chem 1999; 274:23414-25. [PMID: 10438519 DOI: 10.1074/jbc.274.33.23414] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The protein kinase C (PKC) family has been implicated in the regulation of apoptosis. However, the contribution of individual PKC isozymes to this process is not well understood. We reported amplification of the chromosome 2p21 locus in 28% of thyroid neoplasms, and in the WRO thyroid carcinoma cell line. By positional cloning we identified a rearrangement and amplification of the PKCepsilon gene, that maps to 2p21, in WRO cells. This resulted in the overexpression of a chimeric/truncated PKCepsilon (Tr-PKCepsilon) mRNA, coding for N-terminal amino acids 1-116 of the isozyme fused to an unrelated sequence. Expression of the Tr-PKCepsilon protein in PCCL3 cells inhibited activation-induced translocation of endogenous PKCepsilon, but its kinase activity was unaffected, consistent with a dominant negative effect of the mutant protein on activation-induced translocation of wild-type PKCepsilon and/or displacement of the isozyme to an aberrant subcellular location. Cell lines expressing Tr-PKCepsilon grew to a higher saturation density than controls. Moreover, cells expressing Tr-PKCepsilon were resistant to apoptosis, which was associated with higher Bcl-2 levels, a marked impairment in p53 stabilization, and dampened expression of Bax. These findings point to a role for PKCepsilon in apoptosis-signaling pathways in thyroid cells, and indicate that a naturally occurring PKCepsilon mutant that functions as a dominant negative can block cell death triggered by a variety of stimuli.
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Affiliation(s)
- J A Knauf
- Division of Endocrinology and Metabolism, University of Cincinnati, Cincinnati, Ohio 45267-0547, USA
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248
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Cho KK, Mikkelsen T, Lee YJ, Jiang F, Chopp M, Rosenblum ML. The role of protein kinase Calpha in U-87 glioma invasion. Int J Dev Neurosci 1999; 17:447-61. [PMID: 10571407 DOI: 10.1016/s0736-5748(99)00054-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
To investigate the hypothesis that protein kinase Calpha (PKCalpha) is functional glial tumor cell invasion, stable PKCalpha sense and antisense transfected U-87 cell lines were established and PKCalpha expression characterized by Western blot and PKC activity assays. Invasion assays including barrier migration (Koochekpour et al., Extracellular matrix proteins inhibit proliferation, upregulate migration and induce morphological changes in human glioma lines. Eur. J. Cancer, 1995, 31, 375-380; Merzak et al., CD44 mediates human glioma cell adhesion and invasion in vitro. Cancer Res., 1994, 54, 3988-3992; Merzak et al., Cell surface gangliosides are involved in the control of human glioma cell invasion in vitro. Neurosci. Lett., 1994, 177, 11-16), and spheroid confrontation were used to study the relationship between PKCalpha expression and invasiveness. PKCalpha overexpressing clones show increased barrier migration (1.5x) relative to the control transfected clones. PKCalpha inhibited clones exhibited reduced invasiveness, to < 50%. In coculture with PKCalpha overexpressing clones, the remaining normal fetal rat brain aggregate volume was significantly decreased (up to 200%) but 90% of the initial brain volume was left in PKCalpha inhibited clone in the rat brain aggregate tumor spheroid confrontation. This effect was not associated with significant growth inhibition. We conclude that expression of PKCalpha in glioma-derived cell lines appears to be central to glioma invasion in vitro.
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Affiliation(s)
- K K Cho
- Department of Neurosurgery, Henry Ford Hospital, Detroit, MI 48202, USA
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249
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Bouscarel B, Kroll SD, Fromm H. Signal transduction and hepatocellular bile acid transport: cross talk between bile acids and second messengers. Gastroenterology 1999; 117:433-52. [PMID: 10419927 DOI: 10.1053/gast.1999.0029900433] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Affiliation(s)
- B Bouscarel
- Division of Gastroenterology and Nutrition, Department of Medicine, George Washington University Medical Center, Washington, D.C., USA
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250
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Mai S, Hanley-Hyde J, Rainey GJ, Kuschak TI, Paul JT, Littlewood TD, Mischak H, Stevens LM, Henderson DW, Mushinski JF. Chromosomal and extrachromosomal instability of the cyclin D2 gene is induced by Myc overexpression. Neoplasia 1999; 1:241-52. [PMID: 10935479 PMCID: PMC1508077 DOI: 10.1038/sj.neo.7900030] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/1999] [Accepted: 05/25/1999] [Indexed: 11/08/2022]
Abstract
We examined the expression of cyclins D1, D2, D3, and E in mouse B-lymphocytic tumors. Cyclin D2 mRNA was consistently elevated in plasmacytomas, which characteristically contain Myc-activating chromosome translocations and constitutive c-Myc mRNA and protein expression. We examined the nature of cyclin D2 overexpression in plasmacytomas and other tumors. Human and mouse tumor cell lines that exhibited c-Myc dysregulation displayed instability of the cyclin D2 gene, detected by Southern blot, fluorescent in situ hybridization (FISH), and in extrachromosomal preparations (Hirt extracts). Cyclin D2 instability was not seen in cells with low levels of c-Myc protein. To unequivocally demonstrate a role of c-Myc in the instability of the cyclin D2 gene, a Myc-estrogen receptor chimera was activated in two mouse cell lines. After 3 to 4 days of Myc-ER activation, instability at the cyclin D2 locus was seen in the form of extrachromosomal elements, determined by FISH of metaphase and interphase nuclei and of purified extrachromosomal elements. At the same time points, Northern and Western blot analyses detected increased cyclin D2 mRNA and protein levels. These data suggest that Myc-induced genomic instability may contribute to neoplasia by increasing the levels of a cell cycle-regulating protein, cyclin D2, via intrachromosomal amplification of its gene or generation of extrachromosomal copies.
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Affiliation(s)
- S Mai
- Manitoba Institute of Cell Biology, University of Manitoba, Winnipeg, Canada
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