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Ohm AM, Affandi T, Reisz JA, Caino MC, D'Alessandro A, Reyland ME. Metabolic reprogramming contributes to radioprotection by protein kinase Cδ. J Biol Chem 2023; 299:105186. [PMID: 37611829 PMCID: PMC10519828 DOI: 10.1016/j.jbc.2023.105186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 08/17/2023] [Accepted: 08/18/2023] [Indexed: 08/25/2023] Open
Abstract
Loss of protein kinase Cδ (PKCδ) activity renders cells resistant to DNA damaging agents, including irradiation; however, the mechanism(s) underlying resistance is poorly understood. Here, we have asked if metabolic reprogramming by PKCδ contributes to radioprotection. Analysis of global metabolomics showed that depletion of PKCδ affects metabolic pathways that control energy production and antioxidant, nucleotide, and amino acid biosynthesis. Increased NADPH and nucleotide production in PKCδ-depleted cells is associated with upregulation of the pentose phosphate pathway (PPP) as evidenced by increased activation of G6PD and an increase in the nucleotide precursor, 5-phosphoribosyl-1-pyrophosphate. Stable isotope tracing with U-[13C6] glucose showed reduced utilization of glucose for glycolysis in PKCδ-depleted cells and no increase in U-[13C6] glucose incorporation into purines or pyrimidines. In contrast, isotope tracing with [13C5, 15N2] glutamine showed increased utilization of glutamine for synthesis of nucleotides, glutathione, and tricarboxylic acid intermediates and increased incorporation of labeled glutamine into pyruvate and lactate. Using a glycolytic rate assay, we confirmed that anaerobic glycolysis is increased in PKCδ-depleted cells; this was accompanied by a reduction in oxidative phosphorylation, as assayed using a mitochondrial stress assay. Importantly, pretreatment of cells with specific inhibitors of the PPP or glutaminase prior to irradiation reversed radioprotection in PKCδ-depleted cells, indicating that these cells have acquired codependency on the PPP and glutamine for survival. Our studies demonstrate that metabolic reprogramming to increase utilization of glutamine and nucleotide synthesis contributes to radioprotection in the context of PKCδ inhibition.
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Affiliation(s)
- Angela M Ohm
- Department of Craniofacial Biology, School of Dental Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Trisiani Affandi
- Department of Craniofacial Biology, School of Dental Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Julie A Reisz
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - M Cecilia Caino
- Department of Pharmacology, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Angelo D'Alessandro
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Mary E Reyland
- Department of Craniofacial Biology, School of Dental Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA.
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Deletion of P2X7 Receptor Decreases Basal Glutathione Level by Changing Glutamate-Glutamine Cycle and Neutral Amino Acid Transporters. Cells 2020; 9:cells9040995. [PMID: 32316268 PMCID: PMC7226967 DOI: 10.3390/cells9040995] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 04/07/2020] [Accepted: 04/14/2020] [Indexed: 12/24/2022] Open
Abstract
Glutathione (GSH) is an endogenous tripeptide antioxidant that consists of glutamate-cysteine-glycine. GSH content is limited by the availability of glutamate and cysteine. Furthermore, glutamine is involved in the regulation of GSH synthesis via the glutamate–glutamine cycle. P2X7 receptor (P2X7R) is one of the cation-permeable ATP ligand-gated ion channels, which is involved in neuronal excitability, neuroinflammation and astroglial functions. In addition, P2X7R activation decreases glutamate uptake and glutamine synthase (GS) expression/activity. In the present study, we found that P2X7R deletion decreased the basal GSH level without altering GSH synthetic enzyme expressions in the mouse hippocampus. P2X7R deletion also increased expressions of GS and ASCT2 (a glutamine:cysteine exchanger), but diminished the efficacy of N-acetylcysteine (NAC, a GSH precursor) in the GSH level. SIN-1 (500 μM, a generator nitric oxide, superoxide and peroxynitrite), which facilitates the cystine–cysteine shuttle mediated by xCT (a glutamate/cystein:cystine/NAC antiporter), did not affect basal GSH concentration in WT and P2X7R knockout (KO) mice. However, SIN-1 effectively reduced the efficacy of NAC in GSH synthesis in WT mice, but not in P2X7R KO mice. Therefore, our findings indicate that P2X7R may be involved in the maintenance of basal GSH levels by regulating the glutamate–glutamine cycle and neutral amino acid transports under physiological conditions, which may be the defense mechanism against oxidative stress during P2X7R activation.
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3
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Functional Nutrients for Epilepsy. Nutrients 2019; 11:nu11061309. [PMID: 31185666 PMCID: PMC6628163 DOI: 10.3390/nu11061309] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 06/05/2019] [Accepted: 06/06/2019] [Indexed: 12/11/2022] Open
Abstract
Epilepsy is a common neurological disorder of which seizures are a core symptom. Approximately one third of epileptic patients are resistant to antiepileptic drugs and therefore require alternative therapeutic options. Dietary and nutritional supplements can in some cases replace drugs, but with the exception of ketogenic diets, there are no officially recommended dietary considerations for patients with epilepsy. In this review we summarize a selection of nutritional suggestions that have proved beneficial in treating different types of epilepsy. We describe the types of seizures and epilepsy and follow this with an introduction to basic molecular mechanisms. We then examine several functional nutrients for which there is clinical evidence of therapeutic efficacy in reducing seizures or epilepsy-associated sudden death. We also discuss experimental results that demonstrate possible molecular mechanisms elicited by the administration of various nutrients. The availability of multiple dietary and nutritional candidates that show favorable outcomes in animals implies that assessing the clinical potential of these substances will improve translational medicine, ultimately benefitting epilepsy patients.
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Excitotoxicity, neuroinflammation and oxidant stress as molecular bases of epileptogenesis and epilepsy-derived neurodegeneration: The role of vitamin E. Biochim Biophys Acta Mol Basis Dis 2019; 1865:1098-1112. [PMID: 30703511 DOI: 10.1016/j.bbadis.2019.01.026] [Citation(s) in RCA: 101] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Revised: 01/15/2019] [Accepted: 01/24/2019] [Indexed: 12/14/2022]
Abstract
Glutamate-mediated excitotoxicity, neuroinflammation, and oxidative stress are common underlying events in neurodegeneration. This pathogenic "triad" characterizes the neurobiology of epilepsy, leading to seizure-induced cell death, increased susceptibility to neuronal synchronization and network alterations. Along with other maladaptive changes, these events pave the way to spontaneous recurrent seizures and progressive degeneration of the interested brain areas. In vivo models of epilepsy are available to explore such epileptogenic mechanisms, also assessing the efficacy of chemoprevention and therapy strategies at the pre-clinical level. The kainic acid model of pharmacological excitotoxicity and epileptogenesis is one of the most investigated mimicking the chronicization profile of temporal lobe epilepsy in humans. Its pathogenic cues include inflammatory and neuronal death pathway activation, mitochondrial disturbances and lipid peroxidation of several regions of the brain, the most vulnerable being the hippocampus. The importance of neuroinflammation and lipid peroxidation as underlying molecular events of brain damage was demonstrated in this model by the possibility to counteract the related maladaptive morphological and functional changes of this organ with vitamin E, the main fat-soluble cellular antioxidant and "conditional" co-factor of enzymatic pathways involved in polyunsaturated lipid metabolism and inflammatory signaling. The present review paper provides an overview of the literature supporting the potential for a timely intervention with vitamin E therapy in clinical management of seizures and epileptogenic processes associated with excitotoxicity, neuroinflammation and lipid peroxidation, i.e. the pathogenic "triad".
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Carnosine modulates glutamine synthetase expression in senescent astrocytes exposed to oxygen-glucose deprivation/recovery. Brain Res Bull 2017; 130:138-145. [PMID: 28115195 DOI: 10.1016/j.brainresbull.2017.01.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 01/17/2017] [Accepted: 01/19/2017] [Indexed: 12/22/2022]
Abstract
Carnosine is believed to be neuroprotective in cerebral ischemia. However, few reports concern its function on senescent astrocytes during cerebral ischemia. The aim of this study was to investigate the effects of carnosine on cell damage and glutamine synthetase (GS) expression in D-galactose-induced senescent astrocytes exposed to oxygen-glucose deprivation/recovery (OGD/R). The results showed that OGD/R caused massive cell damage and a significant decrease in GS expression both in the young and senescent astrocytes. The GS expression level was partly recovered whereas it continued to decline in the recovery stage in the young and senescent astrocytes, respectively. Decreased GS expression significantly inhibited glutamate uptake and glutamine production and release. Carnosine prevented the cell damage, rescued the expression of GS and reversed the glutamate uptake activity and glutamine production in the senescent astrocytes exposed to OGD/R. The modulatory effect of carnosine on GS expression was partly antagonized by pyrilamine, a selective histamine H1 receptors antagonist, but not bestatin. Bisindolylmaleimide II, a broad-spectrum inhibitor of PKC could also reverse the action of carnosine on GS expression. Thus, histamine H1 receptors and PKC pathway may be involved in the modulatory action of carnosine in GS expression in the senescent astrocytes exposed to OGD/R.
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Hyzinski-García MC, Vincent MY, Haskew-Layton RE, Dohare P, Keller RW, Mongin AA. Hypo-osmotic swelling modifies glutamate-glutamine cycle in the cerebral cortex and in astrocyte cultures. J Neurochem 2011; 118:140-52. [PMID: 21517854 DOI: 10.1111/j.1471-4159.2011.07289.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
In our previous work, we found that perfusion of the rat cerebral cortex with hypo-osmotic medium triggers massive release of the excitatory amino acid L-glutamate but decreases extracellular levels of L-glutamine (R. E. Haskew-Layton et al., PLoS ONE, 3: e3543). The release of glutamate was linked to activation of volume-regulated anion channels, whereas mechanism(s) responsible for alterations in extracellular glutamine remained unclear. When mannitol was added to the hypo-osmotic medium to reverse reductions in osmolarity, changes in microdialysate levels of glutamine were prevented, indicating an involvement of cellular swelling. As the main source of brain glutamine is astrocytic synthesis and export, we explored the impact of hypo-osmotic medium on glutamine synthesis and transport in rat primary astrocyte cultures. In astrocytes, a 40% reduction in medium osmolarity moderately stimulated the release of L-[(3) H]glutamine by ∼twofold and produced no changes in L-[(3) H]glutamine uptake. In comparison, hypo-osmotic medium stimulated the release of glutamate (traced with D-[(3) H]aspartate) by more than 20-fold. In whole-cell enzymatic assays, we discovered that hypo-osmotic medium caused a 20% inhibition of astrocytic conversion of L-[(3) H]glutamate into L-[(3) H]glutamine by glutamine synthetase. Using an HPLC assay, we further found a 35% reduction in intracellular levels of endogenous glutamine. Overall, our findings suggest that cellular swelling (i) inhibits astrocytic glutamine synthetase activity, and (ii) reduces substrate availability for this enzyme because of the activation of volume-regulated anion channels. These combined effects likely lead to reductions in astrocytic glutamine export in vivo and may partially explain occurrence of hyperexcitability and seizures in human hyponatremia.
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Affiliation(s)
- María C Hyzinski-García
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, New York, USA
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7
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Lo JC, Huang WC, Chou YC, Tseng CH, Lee WL, Sun SH. Activation of P2X(7) receptors decreases glutamate uptake and glutamine synthetase activity in RBA-2 astrocytes via distinct mechanisms. J Neurochem 2007; 105:151-64. [PMID: 18067549 DOI: 10.1111/j.1471-4159.2007.05119.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Glutamate clearance by astrocytes is critical for controlling excitatory neurotransmission and ATP is an important mediator for neuron-astrocyte interaction. However, the effect of ATP on glutamate clearance has never been examined. Here we report that treatment of RBA-2 cells, a type-2-like astrocyte cell line, with ATP and the P2X(7) receptor selective agonist 3'-O-(4-benzoylbenzoyl) adenosine 5'-triphosphate (BzATP) decreased the Na+-dependent [3H]glutamate uptake within minutes. Mechanistic studies revealed that the decreases were augmented by removal of extracellular Mg2+ or Ca2+, and was restored by P2X7 selective antagonist , periodate-oxidized 2',3'-dialdehyde ATP (oATP), indicating that the decreases were mediated through P2X(7) receptors. Furthermore, stimulation of P2X7 receptors for 2 h inhibited both activity and protein expression of glutamine synthetase (GS), and oATP abolished the inhibition. In addition, removal of extracellular Ca(2+) and inhibition of protein kinase C (PKC) restored the ATP-decreased GS expression but failed to restore the P2X(7)-decreased [3H]glutamate uptake. Therefore, P2X7-mediated intracellular signals play a role in the down-regulation of GS activity/expression. Activation of P2X7 receptors stimulated increases in intracellular Na+ concentration ([Na+](i)) suggesting that the P2X(7)-induced increases in [Na+](i) may affect the local Na+ gradient and decrease the Na+-dependent [3H]glutamate uptake. These findings demonstrate that the P2X7-mediated decreases in glutamate uptake and glutamine synthesis were mediated through distinct mechanisms in these cells.
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Affiliation(s)
- Jun-Chih Lo
- Institute of Neuroscience, National Yang Ming University, Taipei, Taiwan, Republic of China
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8
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Hall K, Jones M, Poole A. Coincident regulation of PKCdelta in human platelets by phosphorylation of Tyr311 and Tyr565 and phospholipase C signalling. Biochem J 2007; 406:501-9. [PMID: 17570831 PMCID: PMC2049028 DOI: 10.1042/bj20070244] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
PKC (protein kinase C)d plays a complex role in platelets, having effects on both positive and negative signalling functions. It is phosphorylated on tyrosine residues in response to thrombin and collagen, and it has recently been shown that Tyr311 is phosphorylated in response to PAR (protease-activated receptor) 1 and PAR4 receptor activation. In the present study, we show that Tyr311 and Tyr565 are phosphorylated in response to thrombin, and have examined the interplay between phosphorylation and the classical lipid-mediated activation of PKCd. Phosphorylation of both Tyr311 and Tyr565 is dependent on Src kinase and PLC (phospholipase C) activity in response to thrombin. Importantly, direct allosteric activation of PKCd with PMA also induced phosphorylation of Tyr311 and Tyr565, and this was dependent on the activity of Src kinases, but not PLC. Membrane recruitment of PKCd is essential for phosphorylation of this tyrosine residue, but tyrosine phosphorylation is not required for membrane recruitment of PKCd. Both thrombin and PMA induce recruitment of PKCd to the membrane, and for thrombin, this recruitment is a PLC-dependent process. In order to address the functional role of tyrosine residue phosphorylation of PKCd, we demonstrate that phosphorylation can potentiate the activity of the kinase, although phosphorylation does not play a role in membrane recruitment of the kinase. PKCd is therefore regulated in a coincident fashion, PLC-dependent signals recruiting it to the plasma membrane and by phosphorylation on tyrosine residues, potentiating its activity.
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Affiliation(s)
- Kellie J. Hall
- Department of Pharmacology, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD, U.K
| | - Matthew L. Jones
- Department of Pharmacology, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD, U.K
| | - Alastair W. Poole
- Department of Pharmacology, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD, U.K
- To whom correspondence should be addressed (email )
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9
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Yoshida K. PKCdelta signaling: mechanisms of DNA damage response and apoptosis. Cell Signal 2007; 19:892-901. [PMID: 17336499 DOI: 10.1016/j.cellsig.2007.01.027] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2007] [Revised: 01/19/2007] [Accepted: 01/19/2007] [Indexed: 01/02/2023]
Abstract
The cellular response to genotoxic stress that damages DNA includes cell cycle arrest, activation of DNA repair, and in the event of irreparable damage, induction of apoptosis. However, the signals that determine cell fate, that is, survival or apoptosis, are largely unknown. The delta isoform of protein kinase C (PKCdelta) has been implicated in many important cellular processes, including regulation of apoptotic cell death. The available information supports a model in which certain sensors of DNA lesions activate PKCdelta. This activation is triggered in part by tyrosine phosphorylation of PKCdelta by c-Abl tyrosine kinase. PKCdelta is further proteolytically activated by caspase-3. The cleaved catalytic fragment of PKCdelta translocates to the nucleus and induces apoptosis. Importantly, accumulating data have revealed the nuclear targets for PKCdelta in the induction of apoptosis. A pro-apoptotic function of activated PKCdelta is mediated by at least several downstream effectors known to be associated with the elicitation of apoptosis. Recent findings also demonstrated that PKCdelta is involved in cell cycle-specific activation and induction of apoptotic cell death. Moreover, previous studies have shown that PKCdelta regulates transcription by phosphorylating various transcription factors, including the p53 tumor suppressor that is critical for cell cycle arrest and apoptosis in response to DNA damage. These findings collectively support a pivotal role for PKCdelta in the induction of apoptosis with significant impact. This review is focused on the current views regarding the regulation of cell fate by PKCdelta signaling in response to DNA damage.
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Affiliation(s)
- Kiyotsugu Yoshida
- Medical Research Institute, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan.
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10
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Cipok M, Aga-Mizrachi S, Bak A, Feurstein T, Steinhart R, Brodie C, Sampson SR. Protein kinase Calpha regulates insulin receptor signaling in skeletal muscle. Biochem Biophys Res Commun 2006; 345:817-24. [PMID: 16707110 DOI: 10.1016/j.bbrc.2006.05.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2006] [Accepted: 05/03/2006] [Indexed: 11/28/2022]
Abstract
Certain PKC isoforms are stimulated by insulin and interact with IR as well as with IRS, but it is still not clear if specific PKC isoforms regulate IR signaling directly or through IRS-1. PKCalpha may regulate IRS activity in response to insulin. We investigated the possibility that PKCalpha may be important in insulin signaling. Studies were conducted on skeletal muscle in adult mice and on L6 skeletal cells. PKCalpha is constitutively associated with IRS-1, and insulin stimulation of PKCalpha causes disassociation of the two proteins within 5 min. Blockade of PKCalpha inhibited insulin-induced disassociation of PKCalpha from IRS1. Selective inhibition of PKCalpha increased the ability of insulin to reduce blood glucose levels. Insulin stimulation activates PKB and increases the association of PKCalpha with PKB. Blockade of PKCalpha increased threonine phosphorylation of PKB. We suggest that PKCalpha regulates insulin signaling in skeletal muscle through its disassociation from IRS-1 and association with PKB.
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Affiliation(s)
- Michal Cipok
- Gonda Diagnostic Center, Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
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Mangoura D, Sun Y, Li C, Singh D, Gutmann DH, Flores A, Ahmed M, Vallianatos G. Phosphorylation of neurofibromin by PKC is a possible molecular switch in EGF receptor signaling in neural cells. Oncogene 2006; 25:735-45. [PMID: 16314845 DOI: 10.1038/sj.onc.1209113] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Children with neurofibromatosis (NF1) typically develop central nervous system (CNS) abnormalities, including aberrant proliferation of astrocytes and formation of benign astrocytomas. The NF1 gene encodes neurofibromin, a Ras-GAP, highly expressed in developing neural cells; the mechanism of regulation of neurofibromin as a Ras-GAP, remains however unknown. We now show that, in response to EGF, neurofibromin is in vivo phosphorylated on serine residues by PKC-alpha, in human, rat, and avian CNS cells and cell lines. EGF-induced PKC phosphorylation was prominent in the cysteine/serine-rich domain (CSRD) of neurofibromin, which lies in the N-terminus and upstream of the Ras-GAP domain (GRD), and this modification significantly increased the association of neurofibromin with actin in co-immunoprecipitations. In addition, we show that Ras activation in response to EGF was significantly lowered when C62B cells overexpressed a construct encoding both CSRD + GRD. Moreover, when PKC-alpha was downregulated, the Ras-GAP activity of CSRD + GRD was significantly diminished, whereas overexpressed GRD alone acted as a weaker GAP and in a PKC-independent manner. Most importantly, functional Ras inhibition and EGF signaling shifts were established at the single cell level in C6-derived cell lines stably overexpressing CSRD + GRD, when transient co-overexpression of Ras and PKC-depletion prior to stimulation with EGF-induced mitosis. Taken together, these data provide the first evidence of a functional, allosteric regulation of GRD by CSRD, which requires neurofibromin phosphorylation by PKC and association with the actin cytoskeleton. Our data may suggest a novel mechanism for regulating biological responses to EGF and provide a new aspect for the understanding of the aberrant proliferation seen in the CNS of children with NF1.
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Affiliation(s)
- D Mangoura
- Department of Pediatrics, The University of Chicago, Chicago, IL, USA. and Neurosciences Division, Institute for Biomedical Research, Athens, Greece
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Okhrimenko H, Lu W, Xiang C, Ju D, Blumberg PM, Gomel R, Kazimirsky G, Brodie C. Roles of Tyrosine Phosphorylation and Cleavage of Protein Kinase Cδ in Its Protective Effect Against Tumor Necrosis Factor-related Apoptosis Inducing Ligand-induced Apoptosis. J Biol Chem 2005; 280:23643-52. [PMID: 15774464 DOI: 10.1074/jbc.m501374200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Protein kinase Cdelta (PKCdelta) regulates cell apoptosis in a cell- and stimulus-specific manner. Here, we studied the role of PKCdelta in the apoptotic effect of TRAIL in glioma cells. We found that transfection of the cells with a PKCdelta kinase-dead mutant (K376R) or with a small interfering RNA targeting the PKCdelta mRNA increased the apoptotic effect of tumor necrosis factor-related apoptosis inducing ligand (TRAIL), whereas overexpression of PKCdelta decreased it. PKCdelta acted downstream of caspase 8 and upstream of cytochrome c release from the mitochondria. TRAIL induced cleavage of PKCdelta within 2-3 h of treatment, which was abolished by caspase 3, 8, and 9 inhibitors. The cleavage of PKCdelta was essential for its protective effect because overexpression of a caspase-resistant mutant (PKCdeltaD327A) did not protect glioma cells from TRAIL-induced apoptosis but rather increased it. TRAIL induced translocation of PKCdelta to the perinuclear region and the endoplasmic reticulum and phosphorylation of PKCdelta on tyrosine 155. Using a PKCdeltaY155F mutant, we found that the phosphorylation of PKCdelta on tyrosine 155 was essential for the cleavage of PKCdelta in response to TRAIL and for its translocation to the endoplasmic reticulum. In addition, phosphorylation of PKCdelta on tyrosine 155 was necessary for the activation of AKT in response to TRAIL. Our results indicate that PKCdelta protects glioma cells from the apoptosis induced by TRAIL and implicate the phosphorylation of PKCdelta on tyrosine 155 and its cleavage as essential factors in the anti-apoptotic effect of PKCdelta.
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Affiliation(s)
- Hana Okhrimenko
- Gonda (Goldschmied) Medical Diagnosis Research Center, Faculty of Life-Sciences, Bar-Ilan University, Ramat-Gan, Israel 52900
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Abstract
PKCdelta (protein kinase Cdelta) is a serine/threonine kinase that plays a key role in growth regulation and tissue remodelling. Traditional models of PKC activation have focused on lipid cofactors and anchoring proteins that localize the active conformation of PKCdelta to membranes, in close proximity with its target substrates. However, recent studies identify a distinct mode for PKCdelta activation involving tyrosine phosphorylation by Src family kinases. The tyrosine-phosphorylated form of PKCdelta (which accumulates in the soluble fraction of cells exposed to oxidant stress) displays lipid-independent kinase activity and is uniquely positioned to phosphorylate target substrates throughout the cell (not just on lipid membranes). This review summarizes (1) recent progress towards understanding structure-activity relationships for PKCdelta, with a particular focus on the stimuli that induce (and the distinct functional consequences that result from) tyrosine phosphorylation events in PKCdelta's regulatory, hinge and catalytic domains; (2) current concepts regarding the role of tyrosine phosphorylation as a mechanism to regulate PKCdelta localization and actions in mitochondrial and nuclear compartments; and (3) recent literature delineating distinct roles for PKCdelta (relative to other PKC isoforms) in transcriptional regulation, cell cycle progression and programmed cell death (including studies in PKCdelta-/- mice that implicate PKCdelta in immune function and cardiovascular remodelling). Collectively, these studies argue that the conventional model for PKCdelta activation must be broadened to allow for stimulus-specific differences in PKCdelta signalling during growth factor stimulation and oxidant stress.
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Affiliation(s)
- Susan F Steinberg
- Department of Pharmacology, College of Physicians and Surgeons, Columbia University, 630 West 168 Street, New York, NY 10032, USA.
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14
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Braun DC, Garfield SH, Blumberg PM. Analysis by Fluorescence Resonance Energy Transfer of the Interaction between Ligands and Protein Kinase Cδ in the Intact Cell. J Biol Chem 2005; 280:8164-71. [PMID: 15611119 DOI: 10.1074/jbc.m413896200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The role of the protein kinase C (PKC) family of serine/threonine kinases in cellular differentiation, proliferation, apoptosis, and other responses makes them attractive therapeutic targets. The activation of PKCs by ligands in vivo varies depending upon cell type; therefore, methods are needed to screen the potency of PKCs in this context. Here we describe a genetically encoded chimera of native PKCdelta fused to yellow- and cyan-shifted green fluorescent protein, which can be expressed in mammalian cells. This chimeric protein kinase, CY-PKCdelta, retains native or near-native activity in the several biological and biochemical parameters that we tested. Binding assays showed that CY-PKCdelta and native human PKCdelta have similar binding affinity for phorbol 12,13-dibutyrate. Analysis of translocation by Western blotting and confocal microscopy showed that CY-PKCdelta translocates from the cytosol to the membrane upon treatment with ligand, that the translocation has similar dose dependence as that of endogenous PKCdelta, and that the pattern of translocation is indistinguishable from that of the green fluorescent protein-PKCdelta fusion well characterized from earlier studies. Treatment with phorbol ester of cells expressing CY-PKCdelta resulted in a dose-dependent increase in FRET that could be visualized in situ by confocal microscopy or measured fluorometrically. By using this construct, we were able to measure the kinetics and potencies of 12 known PKC ligands, with respect to CY-PKCdelta, in the intact cell. The CY-PKCdelta chimera and the in vivo assays described here therefore show potential for high throughput screening of prospective PKCdelta ligands within the context of cell type.
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Affiliation(s)
- Derek C Braun
- Department of Biology, Gallaudet University, Washington, D. C. 20002, USA
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15
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Pula G, Crosby D, Baker J, Poole AW. Functional interaction of protein kinase Calpha with the tyrosine kinases Syk and Src in human platelets. J Biol Chem 2004; 280:7194-205. [PMID: 15583006 DOI: 10.1074/jbc.m409212200] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
There is a high degree of cross-talk between tyrosine phosphorylation and the serine/threonine phosphorylation signaling pathways. Here we show a physical and functional interaction between the classical protein kinase C isoform (cPKC), PKCalpha, and two major nonreceptor tyrosine kinases in platelets, Syk and Src. In the presence of the cPKC-selective inhibitor Go6976, platelet 5-hydroxytryptamine release was abolished in response to co-activation of glycoproteins VI and Ib-IX-V by the snake venom alboaggregin A, whereas platelet aggregation was substantially inhibited. Of the two platelet cPKCs, PKCalpha but not PKCbeta was activated, occurring in an Syk- and phospholipase C-dependent manner. Syk and PKCalpha associate in a stimulation-dependent manner, requiring Syk but not PKC activity. PKCalpha and Syk also co-translocate from the cytosol to the plasma membrane upon platelet activation, in a manner dependent upon the activities of both kinases. Although PKCalpha is phosphorylated on tyrosine downstream of Syk, we provide evidence against phosphorylation of Syk by PKCalpha, consistent with a lack of effect of PKCalpha inhibition on Syk activity. PKCalpha also associates with Src; although in contrast to interaction with Syk, PKCalpha activity is required for the association of these kinases but not the stimulation-induced translocation of Src to the cell membrane. Finally, the activity of Src is negatively regulated by PKC, as shown by potentiation of Src activity in the presence of the PKC inhibitors GF109203X or Go6976. Therefore, there is a complex interplay between PKCalpha, Syk, and Src involving physical interaction, phosphorylation, translocation within the cell, and functional activity regulation.
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Affiliation(s)
- Giordano Pula
- Department of Pharmacology, School of Medical Sciences, University Walk, Bristol BS8 1TD, United Kingdom
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16
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Kashiwagi H, Shiraga M, Honda S, Kosugi S, Kamae T, Kato H, Kurata Y, Tomiyama Y. Activation of integrin alpha IIb beta 3 in the glycoprotein Ib-high population of a megakaryocytic cell line, CMK, by inside-out signaling. J Thromb Haemost 2004; 2:177-86. [PMID: 14717982 DOI: 10.1111/j.1538-7836.2003.00529.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Affinity/avidity state of integrin alpha IIb beta 3 is regulated by intracellular inside-out signaling. Although several megakaryocytic cell lines have been established, soluble ligand binding to alpha IIb beta 3 expressed in these cells by cellular agonists has not been demonstrated. We have re-examined agonist-induced alpha IIb beta 3 activation on megakaryocytic cell lines with a marker of the late stage of megakaryocytic differentiation, glycoprotein Ib (GPIb). Activation of alpha IIb beta 3 was assessed by PAC1 and soluble fibrinogen binding to the cells. We found that alpha IIb beta 3 expressed in CMK cells with high GPIb expression was activated by a phorbor ester, phorbol myristate acetate (PMA). Although the population of the GPIbhigh cells was <0.5% of the total cells, incubation with a nucleoside analog, ribavirin, efficiently increased the PMA-reactive GPIbhigh cells. Not only PMA but also a calcium ionophore, A23187, induced alpha IIb beta 3 activation, and PMA and A23187 had an additive effect on alpha IIb beta 3 activation. Ligand binding to the activated alpha IIb beta 3 in the GPIbhigh CMK cells is totally abolished by an alpha IIb beta 3-specific antagonist, and inhibited by wortmannin, cytochalasin-D and prostaglandin E1, and the effects of these inhibitors on alpha IIb beta 3 activation in the GPIbhigh CMK cells were compatible with those in platelets. We have also demonstrated that the ribavirin-treated CMK cells express PKC-alpha, -beta, -delta and -theta, and suggested that PKC-alpha and/or -beta appear to be responsible for PMA-induced activation of alpha IIb beta 3 in CMK cells.
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Affiliation(s)
- H Kashiwagi
- Department of Internal Medicine and Molecular Science, Graduate School of Medicine, Osaka University and Department of Blood Transfusion, Osaka University Hospital, Suita, Osaka, Japan.
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17
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Wang Q, Wang X, Evers BM. Induction of cIAP-2 in human colon cancer cells through PKC delta/NF-kappa B. J Biol Chem 2003; 278:51091-9. [PMID: 14527959 DOI: 10.1074/jbc.m306541200] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Activation of protein kinase C (PKC) prevents apoptosis in certain cells; however, the mechanisms are largely unknown. Inhibitors of apoptosis (IAP) family members, including NAIP, cIAP-1, cIAP-2, XIAP/hILP, survivin, and BRUCE, block apoptosis by binding and potently inhibiting caspases. Activation of NF-kappa B contributes to cIAP-2 induction; however, the cellular mechanisms regulating cIAP-2 expression have not been entirely defined. In this study, we examined the role of the PKC and NF-kappa B pathways in the regulation of cIAP-2 in human colon cancers. We found that cIAP-2 mRNA levels were markedly increased in human colon cancer cells by treatment with the phorbol ester, phorbol-12-myristate-13-acetate (PMA), or bryostatin 1. Inhibitors of the Ca2+-independent, novel PKC isoforms, but not inhibitors of MAPK, PI3-kinase, or PKA, blocked PMA-stimulated cIAP-2 mRNA expression, suggesting a role of PKC in PMA-mediated cIAP-2 induction. Pretreatment with the PKC delta-selective inhibitor rottlerin or transfection with an antisense PKC delta oligonucleotide inhibited PMA-induced cIAP-2 expression, whereas cotransfection with a PKC delta plasmid induced cIAP-2 promoter activity, which, taken together, identifies a role for PKC delta in cIAP-2 induction. Treatment with the proteasome inhibitor, MG132 or inhibitors of NF-kappa B (e.g. PDTC and gliotoxin), decreased PMA-induced up-regulation of cIAP-2. PMA-induced NF-kappa B activation was blocked by either GF109203x, MG132, PDTC, or gliotoxin. Moreover, overexpression of PKC delta-induced cIAP-2 promoter activity and increased NF-kappa B transactivation, suggesting regulation of cIAP-2 expression by a PKC delta/NF-kappa B pathway. In conclusion, our findings demonstrate a role for a PKC/NF-kappa B-dependent pathway in the regulation of cIAP-2 expression in human colon cancer cells. These data suggest a novel mechanism for the anti-apoptotic function mediated by the PKC delta/NF-kappa B/cIAP-2 pathway in certain cancers.
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Affiliation(s)
- Qingding Wang
- Department of Surgery and the Sealy Center for Cancer Cell Biology, The University of Texas Medical Branch, Galveston, Texas 77555, USA
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18
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Crosby D, Poole AW. Physical and functional interaction between protein kinase C delta and Fyn tyrosine kinase in human platelets. J Biol Chem 2003; 278:24533-41. [PMID: 12721299 DOI: 10.1074/jbc.m301847200] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
An increasing number of tyrosine kinases have been shown to associate with isoforms of the protein kinase C (PKC) family. Here, we show evidence for physical and functional interaction between PKCdelta and the Src family kinase Fyn in human platelets activated by alboaggregin-A, a snake venom capable of activating both GPIb-V-IX and GPVI adhesion receptors. This interaction involves phosphorylation of PKCdelta on tyrosine and is specific in that other isoforms of PKC, PKCepsilon and lambda, which also become tyrosine-phosphorylated, do not interact with Fyn. In addition, PKCdelta does not interact with other platelet-expressed tyrosine kinases Syk, Src, or Btk. Stimulation also leads to activation of both Fyn and PKCdelta and to serine phosphorylation of Fyn within a PKC consensus sequence. Alboaggregin-A-dependent activation of Fyn is blocked by bisindolylmaleimide I, suggesting a role for PKC isoforms in regulating Fyn activity. Platelet activation with alboaggregin-A induces translocation of the two kinases from cytoplasm to the plasma membrane of platelets, as observed by confocal immunofluorescence microscopy. Translocation of Fyn and PKCdelta are blocked by PP1 and bisindolylmaleimide I, showing a dependence upon Src and PKC kinase activities. Although PKC activity is required for translocation, it is not required for association between the two kinases, because this was not blocked by bisindolylmaleimide I. Rottlerin, which inhibited PKCdelta activity, did not block translocation of either PKCdelta or Fyn but potentiated platelet aggregation, 5-hydroxytryptamine secretion, and the calcium response induced by alboaggregin-A, indicating that this kinase plays a negative role in the control of these processes.
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Affiliation(s)
- David Crosby
- Department of Pharmacology, School of Medical Sciences, University Walk, Bristol BS8 1TD, United Kingdom
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19
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Zrachia A, Dobroslav M, Blass M, Kazimirsky G, Kronfeld I, Blumberg PM, Kobiler D, Lustig S, Brodie C. Infection of glioma cells with Sindbis virus induces selective activation and tyrosine phosphorylation of protein kinase C delta. Implications for Sindbis virus-induced apoptosis. J Biol Chem 2002; 277:23693-701. [PMID: 11927579 DOI: 10.1074/jbc.m111658200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Sindbis virus (SV) is an alpha virus used as a model for studying the role of apoptosis in virus infection. In this study, we examined the role of protein kinase C (PKC) in the apoptosis induced by SVNI, a virulent strain of SV. Infection of C6 cells with SVNI induced a selective translocation of PKCdelta to the endoplasmic reticulum and its tyrosine phosphorylation. The specific PKCdelta inhibitor rottlerin and a PKCdelta kinase-dead mutant increased the apoptosis induced by SVNI. To examine the role of the tyrosine phosphorylation of PKCdelta in the apoptosis induced by SVNI we used a PKCdelta mutant in which five tyrosine residues were mutated to phenylalanine (PKCdelta5). PKCdelta5-overexpressing cells exhibited increased apoptosis in response to SVNI as compared with control cells and to cells overexpressing PKCdelta. SVNI also increased the cleavage of caspase 3 in cells overexpressing PKCdelta5 but did not induce cleavage of PKCdelta or PKCdelta5. Using single tyrosine mutants, we identified tyrosines 52, 64, and 155 as the phosphorylation sites associated with the apoptosis induced by SVNI. We conclude that PKCdelta exerts an inhibitory effect on the apoptosis induced by SV and that phosphorylation of PKCdelta on specific tyrosines is required for this function.
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Affiliation(s)
- Avi Zrachia
- Gonda (Goldschmied) Medical Diagnosis Research Center, Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel
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20
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Blass M, Kronfeld I, Kazimirsky G, Blumberg PM, Brodie C. Tyrosine phosphorylation of protein kinase Cdelta is essential for its apoptotic effect in response to etoposide. Mol Cell Biol 2002; 22:182-95. [PMID: 11739733 PMCID: PMC134204 DOI: 10.1128/mcb.22.1.182-195.2002] [Citation(s) in RCA: 165] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Protein kinase Cdelta (PKCdelta) is involved in the apoptosis of various cells in response to diverse stimuli. In this study, we characterized the role of PKCdelta in the apoptosis of C6 glioma cells in response to etoposide. We found that etoposide induced apoptosis in the C6 cells within 24 to 48 h and arrested the cells in the G(1)/S phase of the cell cycle. Overexpression of PKCdelta increased the apoptotic effect induced by etoposide, whereas the PKCdelta selective inhibitor rottlerin and the PKCdelta dominant-negative mutant K376R reduced this effect compared to control cells. Etoposide-induced tyrosine phosphorylation of PKCdelta and its translocation to the nucleus within 3 h was followed by caspase-dependent cleavage of the enzyme. Using PKC chimeras, we found that both the regulatory and catalytic domains of PKCdelta were necessary for its apoptotic effect. The role of tyrosine phosphorylation of PKCdelta in the effects of etoposide was examined using cells overexpressing a PKCdelta mutant in which five tyrosine residues were mutated to phenylalanine (PKCdelta5). These cells exhibited decreased apoptosis in response to etoposide compared to cells overexpressing PKCdelta. Likewise, activation of caspase 3 and the cleavage of the PKCdelta5 mutant were significantly lower in cells overexpressing PKCdelta5. Using mutants of PKCdelta altered at individual tyrosine residues, we identified tyrosine 64 and tyrosine 187 as important phosphorylation sites in the apoptotic effect induced by etoposide. Our results suggest a role of PKCdelta in the apoptosis induced by etoposide and implicate tyrosine phosphorylation of PKCdelta as an important regulator of this effect.
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Affiliation(s)
- Michal Blass
- Gonda (Goldschmied) Medical Diagnosis Research Center, Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel
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21
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Appel E, Kazimirsky G, Ashkenazi E, Kim SG, Jacobson KA, Brodie C. Roles of BCL-2 and caspase 3 in the adenosine A3 receptor-induced apoptosis. J Mol Neurosci 2001; 17:285-92. [PMID: 11859924 PMCID: PMC5567771 DOI: 10.1385/jmn:17:3:285] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Selective A3 adenosine receptor agonists have been shown to induce apoptosis in a variety of cell types. In this study we examined the effects of adenosine receptor agonists selective for A1, A2A, or A3 receptors on the induction of apoptosis in primary cultures of rat astrocytes and in C6 glial cells. Treatment of the cells with the A3 receptor agonist Cl-IB-MECA (10 microM) induced apoptosis in both cell types. The effects of Cl-IB-MECA were partially antagonized by the A3 receptor-selective antagonist MRS 1191. In contrast, the A1 and A2A receptor agonists, CPA and CGS 21680, respectively, did not have significant effects on apoptosis in these cells. Cl-IB-MECA reduced the expression of endogenous Bcl-2, whereas it did not affect the expression of Bax. Overexpression of Bcl-2 in C6 cells abrogated the induction of apoptosis induced by the A3 agonist. Cl-IB-MECA also induced an increase in caspase 3 activity and caspase inhibitors decreased the apoptosis induced by the A3 agonist. These findings suggest that intense activation of the A3 receptor is pro-apoptotic in glial cells via bcl2 and caspase-3 dependent pathways.
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Affiliation(s)
- Elena Appel
- Gonda (Goldschmied) Medical Diagnosis Research Center, Faculty of Life Science, Bar-Ilan University, Ramat Gan, Israel 52900
| | - Gila Kazimirsky
- Gonda (Goldschmied) Medical Diagnosis Research Center, Faculty of Life Science, Bar-Ilan University, Ramat Gan, Israel 52900
| | - Ely Ashkenazi
- Department of Neurosurgery, Hadassa Hospital, Jerusalem, Israel
| | - Seong Gon Kim
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0810
| | - Kenneth A. Jacobson
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0810
| | - Chaya Brodie
- Gonda (Goldschmied) Medical Diagnosis Research Center, Faculty of Life Science, Bar-Ilan University, Ramat Gan, Israel 52900
- Author to whom all correspondence and reprint requests should be addressed.
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22
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Wooten MW, Vandenplas ML, Seibenhener ML, Geetha T, Diaz-Meco MT. Nerve growth factor stimulates multisite tyrosine phosphorylation and activation of the atypical protein kinase C's via a src kinase pathway. Mol Cell Biol 2001; 21:8414-27. [PMID: 11713277 PMCID: PMC100005 DOI: 10.1128/mcb.21.24.8414-8427.2001] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Atypical protein kinase C (PKC) isoforms are required for nerve growth factor (NGF)-initiated differentiation of PC12 cells. In the present study, we report that PKC-iota becomes tyrosine phosphorylated in the membrane coincident with activation posttreatment with nerve growth factor. Tyrosine phosphorylation and activation of PKC-iota were inhibited in a dose-dependent manner by both PP2 and K252a, src and TrkA kinase inhibitors. Purified src was observed to phosphorylate and activate PKC-iota in vitro. In PC12 cells deficient in src kinase activity, both NGF-induced tyrosine phosphorylation and activation of PKC-iota were also diminished. Furthermore, we demonstrate activation of src by NGF along with formation of a signal complex including the TrkA receptor, src, and PKC-iota. Recruitment of PKC-iota into the complex was dependent on the tyrosine phosphorylation state of PKC-iota. The association of src and PKC-iota was constitutive but was enhanced by NGF treatment, with the src homology 3 domain interacting with a PXXP sequence within the regulatory domain of PKC-iota (amino acids 98 to 114). Altogether, these findings support a role for src in regulation of PKC-iota. Tyrosine 256, 271, and 325 were identified as major sites phosphorylated by src in the catalytic domain. Y256F and Y271F mutations did not alter src-induced activation of PKC-iota, whereas the Y325F mutation significantly reduced src-induced activation of PKC-iota. The functional relevance of these mutations was tested by determining the ability of each mutant to support TRAF6 activation of NF-kappaB, with significant impairment by the Y325F PKC-iota mutant. Moreover, when the Y352F mutant was expressed in PC12 cells, NGF's ability to promote survival in serum-free media was reduced. In summary, we have identified a novel mechanism for NGF-induced activation of atypical PKC involving tyrosine phosphorylation by c-Src.
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Affiliation(s)
- M W Wooten
- Department of Biological Sciences, Auburn University, 331 Funchess Hall, Auburn, AL 36849, USA.
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23
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Samuels IS, Seibenhener ML, Neidigh KB, Wooten MW. Nerve growth factor stimulates the interaction of ZIP/p62 with atypical protein kinase C and targets endosomal localization: evidence for regulation of nerve growth factor-induced differentiation. J Cell Biochem 2001; 82:452-66. [PMID: 11500922 DOI: 10.1002/jcb.1177] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Atypical protein kinase Cs zeta and lambda/iota play a functional role in the regulation of NGF-induced differentiation and survival of pheochromocytoma, PC12 cells [Coleman and Wooten, 1994; Wooten et al., 1999]. Here we demonstrate an NGF-dependent interaction of aPKC with its binding protein, ZIP/p62. Although, ZIP/p62 was not a PKC-iota substrate, the formation of a ZIP/p62-aPKC complex in PC12 cells by NGF occurred post activation of PKC-iota and was regulated by the tyrosine phosphorylation state of aPKC. Furthermore, NGF-dependent localization of ZIP/p62 was observed within vesicular structures, identified as late endosomes by colocalization with a Rab7 antibody. Both ZIP/p62 as well as PKC-iota colocalized with Rab7 upon NGF stimulation. Inhibition of the tyrosine phosphorylation state of PKC-iota did not prevent movement of ZIP/p62 to the endosomal compartment. These observations indicate that the subcellular localization of ZIP/p62 does not depend entirely upon activation of aPKC itself. Of functional importance, transfection of an antisense p62 construct into PC12 cells significantly diminished NGF-induced neurite outgrowth. Collectively, these findings demonstrate that ZIP/p62 acts as a shuttling protein involved in routing activated aPKC to an endosomal compartment and is required for mediating NGF's biological properties.
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Affiliation(s)
- I S Samuels
- Department of Biological Sciences, Program in Cellular and Molecular Biosciences, Auburn University, Auburn, Alabama 36849, USA
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24
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Shanmugam M, Krett NL, Maizels ET, Murad FM, Rosen ST, Hunzicker-Dunn M. A role for protein kinase C delta in the differential sensitivity of MCF-7 and MDA-MB 231 human breast cancer cells to phorbol ester-induced growth arrest and p21(WAFI/CIP1) induction. Cancer Lett 2001; 172:43-53. [PMID: 11595128 DOI: 10.1016/s0304-3835(01)00602-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The goal of this study was to investigate the differential sensitivity of estrogen receptor (ER) positive MCF-7 and ER negative MDA-MB 231 breast cancer cells to phorbol myristate acetate (PMA)-dependent growth arrest. MCF-7 cells were growth arrested by 80% while MDA-MB 231 cells were arrested by 20% in response to seven days of treatment with 10 nM PMA. Coincident with the increased sensitivity of MCF-7 cells to be growth arrested by the protein kinase C (PKC) activator PMA, PMA induced 9-fold higher levels of the cyclin dependent kinase (Cdk) inhibitor p21(WAF1/GIP1) in MCF-7 compared to MDA-MB 231 cells. A comparison of the PKC isoforms expressed in MCF-7 versus MDA-MB 231 cells showed that only the PMA-sensitive PKC delta and eta isoforms were expressed at markedly (> or =10-fold) elevated levels in MCF7 versus MDA-MB 231 cells. These results suggested that the differential sensitivity to growth arrest and induction of p2l(WAFl/CIPl) could reflect, at least in part, increased expression of PMA-dependent PKC isoforms delta and/or eta. Direct evidence to support this hypothesis was provided by the ability of transient transfections into MCF-7 cells of constitutively active PKC delta but not of PKC's eta or alpha or epsilon to enhance p21(WAFl/CIP1) promoter activity. These results suggest that PKC delta plays a fundamental role in the regulation of growth in estrogen receptor positive breast cancer cells.
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Affiliation(s)
- M Shanmugam
- Department of Cell and Molecular Biology, Northwestern University Medical School, 303 East Chicago Avenue, Chicago, IL 60611, USA
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25
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Konishi H, Yamauchi E, Taniguchi H, Yamamoto T, Matsuzaki H, Takemura Y, Ohmae K, Kikkawa U, Nishizuka Y. Phosphorylation sites of protein kinase C delta in H2O2-treated cells and its activation by tyrosine kinase in vitro. Proc Natl Acad Sci U S A 2001; 98:6587-92. [PMID: 11381116 PMCID: PMC34397 DOI: 10.1073/pnas.111158798] [Citation(s) in RCA: 202] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/02/2001] [Indexed: 01/17/2023] Open
Abstract
Protein kinase C delta (PKC delta) is normally activated by diacylglycerol produced from receptor-mediated hydrolysis of inositol phospholipids. On stimulation of cells with H(2)O(2), the enzyme is tyrosine phosphorylated, with a concomitant increase in enzymatic activity. This activation does not appear to accompany its translocation to membranes. In the present study, the tyrosine phosphorylation sites of PKC delta in the H(2)O(2)-treated cells were identified as Tyr-311, Tyr-332, and Tyr-512 by mass spectrometric analysis with the use of the precursor-scan method and by immunoblot analysis with the use of phosphorylation site-specific antibodies. Tyr-311 was the predominant modification site among them. In an in vitro study, phosphorylation at this site by Lck, a non-receptor-type tyrosine kinase, enhanced the basal enzymatic activity and elevated its maximal velocity in the presence of diacylglycerol. The mutation of Tyr-311 to phenylalanine prevented the increase in this maximal activity, but replacement of the other two tyrosine residues did not block such an effect. The results indicate that phosphorylation at Tyr-311 between the regulatory and catalytic domains is a critical step for generation of the active PKC delta in response to H(2)O(2).
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Affiliation(s)
- H Konishi
- Biosignal Research Center, Kobe University, Kobe 657-8501, Japan
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26
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Pepio AM, Sossin WS. Membrane translocation of novel protein kinase Cs is regulated by phosphorylation of the C2 domain. J Biol Chem 2001; 276:3846-55. [PMID: 11073945 DOI: 10.1074/jbc.m006339200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ca(2+)-independent or novel protein kinase Cs (nPKCs) contain an N-terminal C2 domain of unknown function. Removal of the C2 domain of the Aplysia nPKC Apl II allows activation of the enzyme at lower concentrations of phosphatidylserine, suggesting an inhibitory role for the C2 domain in enzyme activation. However, the mechanism for C2 domain-mediated inhibition is not known. Mapping of the autophosphorylation sites for protein kinase C (PKC) Apl II reveals four phosphopeptides in the regulatory domain of PKC Apl II, two of which are in the C2 domain at serine 2 and serine 36. Unlike most PKC autophosphorylation sites, these serines could be phosphorylated in trans. Interestingly, phosphorylation of serine 36 increased binding of the C2 domain to phosphatidylserine membranes in vitro. In cells, PKC Apl II phosphorylation at serine 36 was increased by PKC activators, and PKC phosphorylated at this position translocated more efficiently to membranes. Moreover, mutation of serine 36 to alanine significantly reduced membrane translocation of PKC Apl II. We suggest that translocation of nPKCs is regulated by phosphorylation of the C2 domain.
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Affiliation(s)
- A M Pepio
- Department of Neurology and Neurosurgery, McGill University, Montreal Neurological Institute, Montreal, Quebec H3A 2B4, Canada
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27
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Kronfeld I, Kazimirsky G, Lorenzo PS, Garfield SH, Blumberg PM, Brodie C. Phosphorylation of protein kinase Cdelta on distinct tyrosine residues regulates specific cellular functions. J Biol Chem 2000; 275:35491-8. [PMID: 10945993 DOI: 10.1074/jbc.m005991200] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein kinase Cdelta (PKCdelta) inhibits proliferation and decreases expression of the differentiation marker glutamine synthetase (GS) in C6 glioma cells. Here, we report that distinct, specific tyrosine residues on PKCdelta are involved in these two responses. Transfection of cells with PKCdelta mutated at tyrosine 155 to phenylalanine caused enhanced proliferation in response to 12-phorbol 12-myristate 13-acetate, whereas GS expression resembled that for the PKCdelta wild-type transfectant. Conversely, transfection with PKCdelta mutated at tyrosine 187 to phenylalanine resulted in increased expression of GS, whereas the rate of proliferation resembled that of the PKCdelta wild-type transfectant. The tyrosine phosphorylation of PKCdelta and the decrease in GS expression induced by platelet-derived growth factor (PDGF) were abolished by the Src kinase inhibitors PP1 and PP2. In response to PDGF, Fyn associated with PKCdelta via tyrosine 187. Finally, overexpression of dominant negative Fyn abrogated the decrease in GS expression and reduced the tyrosine phosphorylation of PKCdelta induced by PDGF. We conclude that the tyrosine phosphorylation of PKCdelta and its association with tyrosine kinases may be an important point of divergence in PKC signaling.
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Affiliation(s)
- I Kronfeld
- Gonda (Goldschmied) Medical Diagnosis Research Center, Faculty of Life-Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel
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28
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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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29
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Abstract
The glucocorticoid signaling pathway is responsive to a considerable number of internal and external signals and can therefore establish diverse patterns of gene expression. A glial-specific pattern, for example, is shown by the glucocorticoid-inducible gene glutamine synthetase. The enzyme is expressed at a particularly high level in glial cells, where it catalyzes the recycling of the neurotransmitter glutamate, and at a low level in most other cells, for housekeeping duties. Glial specificity of glutamine synthetase induction is achieved by the use of positive and negative regulatory elements, a glucocorticoid response element and a neural restrictive silencer element. Though not glial specific by themselves, these elements may establish a glial-specific pattern of expression through their mutual activity and their combined effect. The inductive activity of glucocorticoids is markedly repressed by the c-Jun protein, which is expressed at relatively high levels in proliferating glial cells. The signaling pathway of c-Jun is activated by the disruption of glia-neuron cell contacts, by transformation with v-src, and in proliferating retinal cells of early embryonic ages. The c-Jun protein inhibits the transcriptional activity of the glucocorticoid receptor and thus represses glutamine synthetase expression. This repressive mechanism might also affect the ability of glial cells to cope with glutamate neurotoxicity in injured tissues.
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Affiliation(s)
- L Vardimon
- Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, 69978 Tel Aviv, Israel
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