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Richartz N, Pietka W, Yadav A, Bostad M, Bhagwat S, Naderi S, Naderi EH, Stokke T, Ruud E, Blomhoff HK. N-acetyl cysteine turns EPAC activators into potent killers of acute lymphoblastic leukemia cells. J Biol Chem 2024; 300:105509. [PMID: 38042493 PMCID: PMC10772734 DOI: 10.1016/j.jbc.2023.105509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 11/09/2023] [Accepted: 11/13/2023] [Indexed: 12/04/2023] Open
Abstract
Today, the majority of patients with pediatric B cell precursor acute lymphoblastic leukemia (BCP-ALL, hereafter ALL) survive their disease, but many of the survivors suffer from life-limiting late effects of the treatment. ALL develops in the bone marrow, where the cells are exposed to cAMP-generating prostaglandin E2. We have previously identified the cAMP signaling pathway as a putative target for improved efficacy of ALL treatment, based on the ability of cAMP signaling to reduce apoptosis induced by DNA damaging agents. In the present study, we have identified the antioxidant N-acetyl cysteine (NAC) as a powerful modifier of critical events downstream of the cell-permeable cAMP analog 8-(4-chlorophenylthio) adenosine-3', 5'- cyclic monophosphate (8-CPT). Accordingly, we found NAC to turn 8-CPT into a potent killer of ALL cells in vitro both in the presence and absence of DNA damaging treatment. Furthermore, we revealed that NAC in combination with 8-CPT is able to delay the progression of ALL in a xenograft model in NOD-scid IL2Rγnull mice. NAC was shown to rely on the ability of 8-CPT to activate the guanine-nucleotide exchange factor EPAC, and we demonstrated that the ALL cells are killed by apoptosis involving sustained elevated levels of calcium imposed by the combination of the two drugs. Taken together, we propose that 8-CPT in the presence of NAC might be utilized as a novel strategy for treating pediatric ALL patients, and that this powerful combination might be exploited to enhance the therapeutic index of current ALL targeting therapies.
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Affiliation(s)
- Nina Richartz
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Wojciech Pietka
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Ajay Yadav
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Monica Bostad
- Department of Core Facilities, Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
| | - Sampada Bhagwat
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Soheil Naderi
- Division of Laboratory Medicine, Department of Pharmacology, Oslo University Hospital, Oslo, Norway
| | - Elin Hallan Naderi
- Section of Head and Neck Oncology, Department of Oncology, Oslo University Hospital, Oslo, Norway
| | - Trond Stokke
- Department of Core Facilities, Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
| | - Ellen Ruud
- Division of Paediatric and Adolescent Medicine, Oslo University Hospital, Oslo, Norway; Faculty of Medicine, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Heidi Kiil Blomhoff
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.
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Sharma P, Tiufekchiev S, Lising V, Chung SW, Suk JS, Chung BM. Keratin 19 interacts with GSK3β to regulate its nuclear accumulation and degradation of cyclin D3. Mol Biol Cell 2021; 32:ar21. [PMID: 34406791 PMCID: PMC8693971 DOI: 10.1091/mbc.e21-05-0255] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Cyclin D3 regulates the G1/S transition and is frequently overexpressed in several cancer types including breast cancer, where it promotes tumor progression. Here we show that a cytoskeletal protein keratin 19 (K19) physically interacts with a serine/threonine kinase GSK3β and prevents GSK3β-dependent degradation of cyclin D3. The absence of K19 allowed active GSK3β to accumulate in the nucleus and degrade cyclin D3. Specifically, the head (H) domain of K19 was required to sustain inhibitory phosphorylation of GSK3β Ser9, prevent nuclear accumulation of GSK3β, and maintain cyclin D3 levels and cell proliferation. K19 was found to interact with GSK3β and K19–GSK3β interaction was mapped out to require Ser10 and Ser35 residues on the H domain of K19. Unlike wildtype K19, S10A and S35A mutants failed to maintain total and nuclear cyclin D3 levels and induce cell proliferation. Finally, we show that the K19–GSK3β-cyclin D3 pathway affected sensitivity of cells toward inhibitors to cyclin-dependent kinase 4 and 6 (CDK4/6). Overall, these findings establish a role for K19 in the regulation of GSK3β-cyclin D3 pathway and demonstrate a potential strategy for overcoming resistance to CDK4/6 inhibitors.
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Affiliation(s)
- Pooja Sharma
- Department of Biology, The Catholic University of America, Washington, DC 20064
| | - Sarah Tiufekchiev
- Department of Biology, The Catholic University of America, Washington, DC 20064
| | - Victoria Lising
- Department of Biology, The Catholic University of America, Washington, DC 20064
| | - Seung Woo Chung
- Center for Nanomedicine at the Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, 21231
| | - Jung Soo Suk
- Center for Nanomedicine at the Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, 21231
| | - Byung Min Chung
- Department of Biology, The Catholic University of America, Washington, DC 20064
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Liu Y, Yaozu Z, Zhao H, Peng P, Tingbao Z, Jincao C. Inhibition of Glioma Cell Growth and Apoptosis Induction through Targeting Wnt10B Expression by Pyrazolo[4,3-c]pyridine-4-one. Med Sci Monit 2020; 26:e923912. [PMID: 33173023 PMCID: PMC7670829 DOI: 10.12659/msm.923912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Background Gliomas are commonly diagnosed tumors in the central nervous system that have an elevated mortality rate. The present study evaluated pyrazolo[4,3-c]pyridine-4-one (PP-4-one) as an anti-proliferative agent against glioma cells and investigated the associated mechanism. Material/Methods The changes in cell growth were analyzed by Cell Counting Kit-8 (CCK-8) and apoptosis by flow cytometry using Annexin V-FITC staining kit. The FACSCalibur flow cytometer was used for analysis of DNA content and western blotting for protein expression. Results The PP-4-one treatment suppressed viability of U251, C6, and U87 cells significantly at a concentration of 0.25 μM. At a concentration of 16 μM, PP-4-one treatment for 72 hours suppressed viability of U251, C6, and U87 cells to 24%, 21%, and 20%, respectively. Treatment with PP-4-one suppressed cyclic 3′,5′-adenosine monophosphate (cAMP) levels in U251 and C6 cells significantly (P<0.05) depending on the concentration. The apoptotic cells were increased significantly (P<0.05) by PP-4-one treatment in U251 and C6 cell cultures. A considerable enhancement in the proportion of U251 and C6 cells in the G0/G1 phase was recorded on incubation with PP-4-one. Treatment of U251 and C6 cells with PP-4-one markedly enhanced p21 expression relative to the control. The B-cell lymphoma (Bcl-2) level in PP-4-one treated U251 and C6 cells was markedly lower relative to the control cells. The Bax, caspase-3, and caspase-9 levels were elevated markedly by PP-4-one treatment in U251 and C6 cells. Conclusions This study demonstrated that PP-4-one has anti-proliferative potential for glioma cells via targeting cAMP and Bcl-2 levels. It also promoted glioma cell apoptosis through caspase activation and arrest of the cell cycle. Thus, PP-4-one may be used to develop drug candidates for the glioma treatment.
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Affiliation(s)
- Yang Liu
- Department of Neurosurgery, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, China (mainland).,Department of Neurosurgery, General Hospital of Central Theater of the People's Liberation Army (PLA), Wuhan, Hubei, China (mainland)
| | - Zhu Yaozu
- Department of Neurosurgery, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, China (mainland).,Department of Neurosurgery, Xiangyang Central Hospital, Affiliated Hospital of Hubei University of Arts and Science, Xiangyang, Hubei, China (mainland)
| | - Huang Zhao
- Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China (mainland)
| | - Peng Peng
- Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China (mainland)
| | - Zhang Tingbao
- Department of Neurosurgery, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, China (mainland)
| | - Chen Jincao
- Department of Neurosurgery, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, China (mainland)
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Fan H, Geng L, Yang F, Dong X, He D, Zhang Y. Ursolic acid derivative induces apoptosis in glioma cells through down-regulation of cAMP. Eur J Med Chem 2019; 176:61-67. [PMID: 31096119 DOI: 10.1016/j.ejmech.2019.04.059] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Revised: 04/19/2019] [Accepted: 04/20/2019] [Indexed: 01/13/2023]
Abstract
The present study was designed to synthesize and evaluate ursolic acid hybrid compounds against glioma cells. Initial screening revealed that most of the synthesized compounds displayed better inhibitory effect on glioma cell proliferation compared to parent ursolic acid. The mechanism of inhibitory effect of the most potent compound 6d on glioma cells was investigated in detail. Treatment with compound 6d significantly (p < 0.001) reduced U251 and C6 cell proliferation at 48 h. The growth of U251 and C6 glioma cells was reduced to minimum level (17 and 21%) on treatment with 10 μM concentration of compound 6d. Treatment of the U251 cells with 10 μM concentration of compound 6d caused a significant (p < 0.05) inhibition of cAMP level. In U251 cell cultures treatment with compound 6d at 10 μM concentration enhanced proportion of apoptotic cells to 69.32% compared to 2.34% in the control cultures. The compound 6d treatment of U251 cells for 48 h caused arrest of cell cycle in the G0/G1 phase with consequent decrease of cell population in G2/M and S phases. The results from TEM showed that compound 6d treatment of U251 cells for 48 h caused blebbing of the cell membranes, chromatin condensation, appearance of foamy cytoplasmic material and autophagic vacuoles. The results from SEM revealed that compound 6d treatment of U251 cells caused a marked inhibition of microvilli and extensions on the cell surfaces. Thus present study demonstrates that compound 6d inhibits glioma cell growth, induces apoptosis and arrest cell cycle through metabolic pathway down-regulation. Therefore, compound 6d can be evaluated further for the treatment of glioma.
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Affiliation(s)
- Haitao Fan
- Department of Neurosurgery, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, Shandong, 250021, China
| | - Li Geng
- Department of Gastroenterology, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, Shandong, 250021, China
| | - Fan Yang
- Department of Neurosurgery, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, Shandong, 250021, China
| | - Xushuai Dong
- Department of Neurosurgery, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, Shandong, 250021, China
| | - Dong He
- Department of Neurosurgery, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, Shandong, 250021, China
| | - Yongchao Zhang
- Department of Neurosurgery, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, Shandong, 250021, China.
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5
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Kloster MM, Naderi EH, Haaland I, Gjertsen BT, Blomhoff HK, Naderi S. cAMP signalling inhibits p53 acetylation and apoptosis via HDAC and SIRT deacetylases. Int J Oncol 2013; 42:1815-21. [PMID: 23483263 DOI: 10.3892/ijo.2013.1853] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Accepted: 01/18/2013] [Indexed: 11/05/2022] Open
Abstract
Activation of cAMP signalling potently inhibits DNA damage-induced apoptosis in acute lymphoblastic leukemia cells by promoting the turnover of p53 protein. Recently, we showed that the cAMP-induced destabilization of p53 in DNA-damaged cells occurs as a result of enhanced interaction between p53 and HDM2. In this report, we present results showing that increased levels of cAMP in cells with DNA damage enhances the deacetylation of p53, an event that facilitates the interaction of p53 with HDM2, thus annulling the stabilizing effect of DNA damage on p53. The combined inhibition of the HDAC and SIRT1 deacetylases abolished the cAMP-mediated deacetylation of p53, implying that cAMP-mediated deacetylation of p53 is dependent on the activity of these two classes of histone deacetylases. Importantly, diminishing the activity of HDACs and SIRT1 was also found to reverse the inhibitory effect of cAMP on the DNA damage-induced p53 stabilization and apoptosis, suggesting the involvement of the p53 acetylation pathway in the anti-apoptotic effect of cAMP signalling.
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6
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Activation of cAMP signaling interferes with stress-induced p53 accumulation in ALL-derived cells by promoting the interaction between p53 and HDM2. Neoplasia 2011; 13:653-63. [PMID: 21750659 DOI: 10.1593/neo.11542] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Revised: 05/13/2011] [Accepted: 05/16/2011] [Indexed: 12/11/2022] Open
Abstract
The tumor suppressor p53 provides an important barrier to the initiation and maintenance of cancers. As a consequence, p53 function must be inactivated for a tumor to develop. This is achieved by mutation in approximately 50% of cases and probably by functional inactivation in the remaining cases. We have previously shown that the second messenger cAMP can inhibit DNA damage-induced wild-type p53 accumulation in acute lymphoblastic leukemia cells, leading to a profound reduction of their apoptotic response. In the present article, we provide a mechanistic insight into the regulation of p53 levels by cAMP. We show that increased levels of cAMP augment the binding of p53 to its negative regulator HDM2, overriding the DNA damage-induced dissociation of p53 from HDM2. This results in maintained levels of p53 ubiquitination and proteasomal degradation, which in turn counteracts the DNA damage-induced stabilization of the p53 protein. The apoptosis inhibitory effect of cAMP is further shown to depend on this effect on p53 levels. These findings potentially implicate deregulation of cAMP signaling as a candidate mechanism used by transformed cells to quench the p53 response while retaining wild-type p53.
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Cyclic AMP-mediated immune regulation--overview of mechanisms of action in T cells. Cell Signal 2010; 23:1009-16. [PMID: 21130867 DOI: 10.1016/j.cellsig.2010.11.018] [Citation(s) in RCA: 154] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2010] [Revised: 11/23/2010] [Accepted: 11/25/2010] [Indexed: 01/21/2023]
Abstract
The canonical second messenger cAMP is well established as a potent negative regulator of T cell immune function. Through protein kinase A (PKA) it regulates T cell function at the level of transcription factors, members of the mitogen-activated protein kinase pathway, phospholipases (PLs), Ras homolog (Rho)A and proteins involved in the control of cell cycle progression. Type I PKA is the predominant PKA isoform in T cells. Furthermore, whereas type II PKA is located at the centrosome, type I PKA is anchored close to the T cell receptor (TCR) in lipid rafts by the Ezrin-ERM-binding phosphoprotein of 50 kDa (EBP50)-phosphoprotein associated with glycosphingolipid-enriched microdomains (PAG) scaffold complex. The most TCR-proximal target for type I PKA is C-terminal Src kinase (Csk), which upon activation by raft recruitment and phosphorylation inhibits the Src family tyrosine kinases Lck and Fyn and thus functions to maintain T cell homeostasis. Recently, induction of cAMP levels in responder T cells has emerged as one of the mechanisms by which regulatory T (T(R)) cells execute their suppressive action. Thus, the cAMP-type I PKA-Csk pathway emerges as a putative target for therapeutic intervention in autoimmune disorders as well as in cancer, where T(R) cell-mediated suppression contributes to suboptimal local immune responses.
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8
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Vasoactive intestinal peptide induces cell cycle arrest and regulatory functions in human T cells at multiple levels. Mol Cell Biol 2010; 30:2537-51. [PMID: 20231362 DOI: 10.1128/mcb.01282-09] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Vasoactive intestinal peptide (VIP) is a potent anti-inflammatory neuropeptide that, by inhibiting Th1-driven responses and inducing the emergence of regulatory T cells (T(reg)), has been proven successful in the induction of tolerance in various experimental models of autoimmune disorders. Here, we investigate the molecular mechanisms involved in VIP-induced tolerance. VIP treatment in the presence of T-cell receptor (TCR) signaling and CD28 costimulation induced cell cycle arrest in human T cells. VIP blocked G(1)/S transition and inhibited the synthesis of cyclins D3 and E and the activation of the cyclin-dependent kinases (CDKs) cdk2 and cdk4. This effect was accompanied by maintenance of threshold levels of the CDK inhibitor p27(kip1) and impairment of phosphatidylinositol 3-kinase (PI3K)-Akt signaling. Inhibition of interleukin 2 (IL-2) transcription and downregulation of signaling through NFAT, AP-1, and Ras-Raf paralleled the VIP-induced cell cycle arrest. Noteworthy from a functional point of view is the fact that VIP-treated T cells show a regulatory phenotype characterized by high expression of CD25, cytotoxic-T-lymphocyte-associated protein 4 (CTLA4), and Forkhead box protein 3 (FoxP3) and potent suppressive activities against effector T cells. CTLA4 appears to be critically involved in the generation and suppressive activities of VIP-induced T(reg). Finally, cyclic AMP (cAMP) and protein kinase A (PKA) activation seems to mediate the VIP-induced cell cycle arrest and T(reg) generation.
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9
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Abstract
Identification of rational therapeutic targets is an important strategy to improve the cure rate of diffuse large B-cell lymphoma (DLBCL). We previously showed that inhibition of the phosphodiesterase 4B (PDE4B) unleashes cyclic-AMP (cAMP) inhibitory effects toward the PI3K/AKT pathway and induces apoptosis. These data raised important considerations as to which upstream regulators mediate cAMP inhibition of PI3K/AKT, and how identifying this signaling route could be translated into clinical initiatives. We found that in normal and malignant B cells, cAMP potently inhibit the phosphorylation and activity of the tyrosine kinase SYK. Using genetic models of gain- and loss-of-function, we demonstrated the essential role for PDE4B in controlling these effects in DLBCL. Furthermore, we used a constitutively active SYK mutant to confirm its central role in transducing cAMP effects to PI3K/AKT. Importantly, given SYK credentials as a therapeutic target in B-cell tumors, we explored the role of PDE4B in these responses. In multiple DLBCL models, we found that genetically, hence specifically, inhibiting PDE4B expression significantly improved the efficacy of SYK inhibitors. Our data defined a hitherto unknown role for cAMP in negatively regulating SYK and indicate that combined inhibition of PDE4B and SYK should be actively pursued.
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Grandoch M, López de Jesús M, Oude Weernink PA, Weber AA, Jakobs KH, Schmidt M. B cell receptor-induced growth arrest and apoptosis in WEHI-231 immature B lymphoma cells involve cyclic AMP and Epac proteins. Cell Signal 2009; 21:609-21. [PMID: 19167486 DOI: 10.1016/j.cellsig.2009.01.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2008] [Revised: 12/23/2008] [Accepted: 01/01/2009] [Indexed: 12/13/2022]
Abstract
Signaling by the B cell antigen receptor (BCR) is essential for B lymphocyte homeostasis and immune function. In immature B cells, ligation of the BCR promotes growth arrest and apoptosis, and BCR-driven balancing between pro-apoptotic extracellular signal-regulated kinase 1 and 2 (ERK1/2) and anti-apoptotic phosphoinositide 3-kinase-dependent Akt seems to define the final cellular apoptotic response. Dysfunction of these late BCR signaling events can lead to the development of immunological diseases. Here we report on novel cyclic AMP-dependent mechanisms of BCR-induced growth arrest and apoptosis in the immature B lymphoma cell line WEHI-231. BCR signaling to ERK1/2 and Akt requires cyclic AMP-regulated Epac, the latter acting as a guanine nucleotide exchange factor for Rap1 and H-Ras independent of protein kinase A. Importantly, activation of endogenously expressed Epac by a specific cyclic AMP analog enhanced the induction of growth arrest (reduced DNA synthesis) and apoptosis (nuclear condensation, annexin V binding, caspase-3 cleavage and poly-ADP-ribose polymerase processing) by the BCR. Our data indicate that cyclic AMP-dependent Epac signals to ERK1/2 and Akt upon activation of Rap1 and H-Ras, and is involved in BCR-induced growth arrest and apoptosis in WEHI-231 cells.
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Affiliation(s)
- Maria Grandoch
- Institut für Pharmakologie, Universitätsklinikum Essen, Essen, Germany.
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11
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Naderi S, Blomhoff HK. Activation of cAMP signaling enhances Fas-mediated apoptosis and activation-induced cell death through potentiation of caspase 8 activation. Hum Immunol 2008; 69:833-6. [DOI: 10.1016/j.humimm.2008.09.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2008] [Revised: 08/27/2008] [Accepted: 09/04/2008] [Indexed: 11/28/2022]
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12
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Rodriguez-Collazo P, Snyder SK, Chiffer RC, Bressler EA, Voss TC, Anderson EP, Genieser HG, Smith CL. cAMP signaling regulates histone H3 phosphorylation and mitotic entry through a disruption of G2 progression. Exp Cell Res 2008; 314:2855-69. [PMID: 18644368 DOI: 10.1016/j.yexcr.2008.06.022] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2008] [Revised: 06/28/2008] [Accepted: 06/30/2008] [Indexed: 01/06/2023]
Abstract
cAMP signaling is known to have significant effects on cell growth, either inhibitory or stimulatory depending on the cell type. Study of cAMP-induced growth inhibition in mammalian somatic cells has focused mainly on the combined role of protein kinase A (PKA) and mitogen-activated protein (MAP) kinases in regulation of progression through the G1 phase of the cell cycle. Here we show that cAMP signaling regulates histone H3 phosphorylation in a cell cycle-dependent fashion, increasing it in quiescent cells but dramatically reducing it in cycling cells. The latter is due to a rapid and dramatic loss of mitotic histone H3 phosphorylation caused by a disruption in G2 progression, as evidenced by the inhibition of mitotic entry and decreased activity of the CyclinB/Cdk1 kinase. The inhibition of G2 progression induced through cAMP signaling is dependent on expression of the catalytic subunit of PKA and is highly sensitive to intracellular cAMP concentration. The mechanism by which G2 progression is inhibited is independent of both DNA damage and MAP kinase signaling. Our results suggest that cAMP signaling activates a G2 checkpoint by a unique mechanism and provide new insight into normal cellular regulation of G2 progression.
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Affiliation(s)
- Pedro Rodriguez-Collazo
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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13
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Kloster MM, Hafte TT, Moltzau LR, Naderi EH, Dahle MK, Skålhegg BS, Gaudernack G, Levy FO, Naderi S, Blomhoff HK. EBV infection renders B cells resistant to growth inhibition via adenylyl cyclase. Cell Signal 2008; 20:1169-78. [PMID: 18406106 DOI: 10.1016/j.cellsig.2008.02.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2007] [Revised: 02/04/2008] [Accepted: 02/13/2008] [Indexed: 12/27/2022]
Abstract
Cyclic AMP (cAMP) is an important physiological growth inhibitor of lymphoid cells, and the cAMP/protein kinase A (PKA) pathway is disrupted in several immunological disorders and cancers. Epstein Barr virus (EBV) infection of B lymphocytes is responsible for the development of lymphoproliferative disease as well as certain B-lymphoid malignancies. Here we hypothesized that EBV infection might render B lymphocytes resistant to cAMP/PKA-mediated growth inhibition. To test this, we assessed the growth-inhibitory response of cAMP-elevating compounds such as forskolin and isoproterenol, as well as the PKA activator 8-CPT-cAMP in normal B lymphocytes, EBV-infected B cells and in the EBV-negative B lymphoid cell line Reh. We could demonstrate that EBV infection indeed abolished cAMP-mediated growth inhibition of B cells. The defect was pinpointed to defective adenylyl cyclase (AC) activation by forskolin and isoproterenol, resulting in reduced formation of cAMP and lack of PKA activation and CREB phosphorylation. In contrast, 8-CPT-cAMP which directly activates PKA was able to inhibit EBV-infected B cell growth. The physiological implications of these results were underlined by the observation that the ability of forskolin to inhibit camptothecin-induced apoptosis was abolished in EBV-infected B cells. We conclude that EBV infection of B cells abrogates the activation of AC and thereby cAMP formation, and that this dysfunction renders the cells resistant to growth inhibition via the cAMP/PKA pathway.
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Affiliation(s)
- Martine Müller Kloster
- Department of Biochemistry, Institute of Basic Medical Sciences, University of Oslo, N-0317 Oslo, Norway
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14
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O'Shaughnessy MJ, Chen ZM, Gramaglia I, Taylor PA, Panoskaltsis-Mortari A, Vogtenhuber C, Palmer E, Grader-Beck T, Boussiotis VA, Blazar BR. Elevation of intracellular cyclic AMP in alloreactive CD4(+) T Cells induces alloantigen-specific tolerance that can prevent GVHD lethality in vivo. Biol Blood Marrow Transplant 2007; 13:530-42. [PMID: 17448912 DOI: 10.1016/j.bbmt.2007.01.071] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2006] [Accepted: 01/11/2007] [Indexed: 10/23/2022]
Abstract
Cyclic AMP (cAMP) is an important negative regulator of T cell activation, and an increased level of cAMP is associated with T cell hyporesponsiveness in vitro. We sought to determine whether elevating intracellular cAMP levels ex vivo in alloreactive T cells during primary mixed lymphocyte reactions (MLR) is sufficient to induce alloantigen-specific tolerance and prevent graft-versus-host disease (GVHD). Primary MLRs were treated with exogenous (8)Br-cAMP and IBMX, a compound that increases intracellular cAMP levels by inhibition of phosphodiesterases. T cell proliferation and IL-2 responsiveness in the treated primary MLR cultures were greatly reduced, and viable T cells recovered on day 8 also had impaired responses to restimulation with alloantigen compared to control-treated cells, but without an impairment to nonspecific mitogens. Labeling experiments showed that cAMP/IBMX inhibited alloreactive T cell proliferation by limiting the number of cell divisions, increasing susceptibility to apoptosis, and rendering nondeleted alloreactive T cells hyporesponsive to alloantigen restimulation. cAMP/IBMX-treated CD4(+) T cells had a markedly reduced capacity for GVHD lethality in major histocompatibility complex class II disparate recipients, but maintained the capacity to mediate other CD4(+) T cell responses in vivo. Thus, our results provide the first preclinical evidence of using cAMP-elevating pharmaceutical reagents to achieve long-term alloantigen-specific T cell tolerance that is sufficient to prevent GVHD.
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Affiliation(s)
- Matthew J O'Shaughnessy
- University of Minnesota Cancer Center, Department of Pediatrics, Division of Bone Marrow Transplantation, Minneapolis, Minnesota 55455, USA
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15
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Schmees C, Prinz C, Treptau T, Rad R, Hengst L, Voland P, Bauer S, Brenner L, Schmid RM, Gerhard M. Inhibition of T-cell proliferation by Helicobacter pylori gamma-glutamyl transpeptidase. Gastroenterology 2007; 132:1820-33. [PMID: 17484877 DOI: 10.1053/j.gastro.2007.02.031] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2006] [Accepted: 01/18/2007] [Indexed: 12/14/2022]
Abstract
BACKGROUND & AIMS Helicobacter pylori colonizes the human gastric mucosa of >50% of the world's population. Most of the patients have no overt clinical symptoms. However, the infection is invariably associated with the development of active chronic gastritis, leading in some cases to the development of peptic ulcer disease, distal gastric adenocarcinoma, and mucosa-associated lymphoid tissue lymphoma. In contrast to most other pathogens, infection with H pylori persists lifelong, but reasons for the persistence remain obscure. CD4-positive T cells are crucial for bacterial elimination but are inhibited by H pylori. We aimed to identify the factor responsible for suppression of T-cell response and characterize this inhibitory effect on a cellular and molecular level. METHODS Using size-exclusion chromatography, sodium dodecyl sulfate/polyacrylamide gel electrophoresis, and a spectrophotometric enzyme assay, we identified the secreted gamma-glutamyl transpeptidase of H pylori (HPGGT) as the factor responsible for inhibition of T-cell proliferation. RESULTS Mutagenesis of HPGGT in different H pylori strains completely abrogated this inhibitory effect. Recombinantly expressed HPGGT protein showed full antiproliferative activity. Site-directed mutagenesis and application of the GGT inhibitor acivicin revealed that inhibition of T cells depends on catalytic activity of HPGGT. Cell cycle analysis of human T cells indicated that HPGGT was necessary and sufficient to induce G(1) arrest. Reduced levels of c-Myc and phosphorylated c-Raf protein suggest the disruption of Ras-dependent signaling by HPGGT. CONCLUSIONS GGT is a novel immunosuppressive factor of H pylori inhibiting T-cell proliferation by induction of a cell cycle arrest in the G(1) phase.
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Affiliation(s)
- Christian Schmees
- Department of Medicine II, Technical University of Munich, Munich, Germany
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16
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Cho CH, Seo M, Lee YI, Kim SY, Youn HD, Juhnn YS. Dibutyryl cAMP stimulates the proliferation of SH-SY5Y human neuroblastoma cells by up-regulating Skp2 protein. J Cancer Res Clin Oncol 2006; 133:135-44. [PMID: 17004068 DOI: 10.1007/s00432-006-0153-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2006] [Accepted: 08/02/2006] [Indexed: 01/19/2023]
Abstract
PURPOSE We previously found that the proliferation of SH-SY5Y neuroblastoma cells is stimulated when cAMP is up-regulated by stable expression of stimulatory G protein. Therefore, this study was performed to investigate the mechanism whereby cAMP stimulates the proliferation of SH-SY5Y cells. METHODS To investigate the effect of cAMP on cellular proliferation, SH-SY5Y neuroblastoma cells were treated with dibutyryl cAMP (dbcAMP), and then cell growth, thymidine incorporation and cell cycle phase distribution were analyzed. The expression and the activity of the molecules that regulate cell cycle progression were monitored by Western blot, RT-PCR, and kinase activity assay. RESULTS Treatment with dbcAMP produced a biphasic effect on cellular proliferation; especially treatment with low concentration of dbcAMP (0.5 mM) showed a higher cellular proliferation rate and promoted G1/S transition in cell cycle. The dbcAMP (0.5 mM) treatment increased CDK2 activity, and it significantly decreased p27Kip1 expression with a decreased half-life of p27Kip1 protein. Moreover, dbcAMP (0.5 mM) increased the protein level and the stability of Skp2 with a concomitant decrease in its ubiquitination. CONCLUSIONS cAMP up-regulates Skp2 protein by reducing its degradation probably through decreasing the ubiquitination of Skp2, which might result in accelerated degradation of p27Kip1, increase in CDK2 activity, and stimulation of SH-SY5Y cell proliferation in sequence.
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Affiliation(s)
- Chin-Ho Cho
- Department of Biochemistry and Molecular Biology, Laboratory of Cellular Signaling, Cancer Research Institute, Seoul National University College of Medicine, 28 Yongon-dong, Jongno-gu, Seoul, 110-799, South Korea
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17
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Spofford LS, Abel EV, Boisvert-Adamo K, Aplin AE. Cyclin D3 expression in melanoma cells is regulated by adhesion-dependent phosphatidylinositol 3-kinase signaling and contributes to G1-S progression. J Biol Chem 2006; 281:25644-51. [PMID: 16815849 PMCID: PMC4266577 DOI: 10.1074/jbc.m600197200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
D-type cyclins regulate G1 cell cycle progression by enhancing the activities of cyclin-dependent kinases (CDKs), and their expression is frequently altered in malignant cells. We and others have previously shown that cyclin D1 is up-regulated in melanoma cells through adhesion-independent MEK-ERK1/2 signaling initiated by mutant B-RAF. Here, we describe the regulation and role of cyclin D3 in human melanoma cells. Cyclin D3 expression was enhanced in a cell panel of human melanoma cell lines compared with melanocytes and was regulated by fibronectin-mediated phosphatidylinositol 3-kinase/Akt signaling but not MEK activity. RNA interference experiments demonstrated that cyclin D3 contributed to G1-S cell cycle progression and proliferation in melanoma cells. Overexpression of cyclin D1 did not recover the effects of cyclin D3 knockdown. Finally, immunoprecipitation studies showed that CDK6 is a major binding partner for cyclin D3, whereas CDK4 preferentially associated with cyclin D1. Together, these findings demonstrate that cyclin D3 is an important regulator of melanoma G1-S cell cycle progression and that D-type cyclins are differentially regulated in melanoma cells.
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Affiliation(s)
- Laurie S. Spofford
- Center for Cell Biology and Cancer Research, Albany Medical College, Albany, New York 12208
| | - Ethan V. Abel
- Center for Cell Biology and Cancer Research, Albany Medical College, Albany, New York 12208
| | - Karen Boisvert-Adamo
- Center for Cell Biology and Cancer Research, Albany Medical College, Albany, New York 12208
| | - Andrew E. Aplin
- Center for Cell Biology and Cancer Research, Albany Medical College, Albany, New York 12208
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18
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Låhne HU, Kloster MM, Lefdal S, Blomhoff HK, Naderi S. Degradation of cyclin D3 independent of Thr-283 phosphorylation. Oncogene 2006; 25:2468-76. [PMID: 16331257 DOI: 10.1038/sj.onc.1209278] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Cyclin D3 has been shown to play a major role in the regulation of cell cycle progression in lymphocytes. It is therefore important to understand the mechanisms involved in the regulation of this protein. We have previously shown that both basal and cAMP-induced degradation of cyclin D3 in Reh cells is dependent on Thr-283 phosphorylation by glycogen synthase kinase-3beta (GSK-3beta). We now provide evidence of an alternative mechanism being involved in the regulation of cyclin D3 degradation. Treatment of lymphoid cells with okadaic acid (OA), an inhibitor of protein phosphatases 1 and 2A (PP1 and PP2A), induces rapid phosphorylation and proteasomal degradation of cyclin D3. This degradation is not inhibited by the GSK-3beta inhibitors lithium or Kenpaullone, or by substitution of Thr-283 with Ala on cyclin D3, indicating that cyclin D3 can be degraded independently of Thr-283 phosphorylation and GSK-3beta activity. Interestingly, in vitro experiments revealed that PP1, but not PP2A, was able to dephosphorylate cyclin D3 efficiently, and PP1 was found to associate with His-tagged cyclin D3. These results support the hypothesis that PP1 constitutively keeps cyclin D3 in a stable, dephosphorylated state, and that treatment of cells with OA leads to phosphorylation and degradation of cyclin D3 through inhibition of PP1.
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Affiliation(s)
- H U Låhne
- Department of Biochemistry, Institute of Basic Medical Sciences, University of Oslo, P.O. Box 1112 Blindern, Oslo, Norway
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19
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Chemnitz JM, Driesen J, Classen S, Riley JL, Debey S, Beyer M, Popov A, Zander T, Schultze JL. Prostaglandin E2 impairs CD4+ T cell activation by inhibition of lck: implications in Hodgkin's lymphoma. Cancer Res 2006; 66:1114-22. [PMID: 16424048 DOI: 10.1158/0008-5472.can-05-3252] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Many tumors, including Hodgkin's lymphoma, are associated with decreased cellular immunity and elevated levels of prostaglandin E(2) (PGE(2)), a known inhibitor of CD4+ T cell activation, suggested to be involved in immune deviation in cancer. To address the molecular mechanisms tumor-derived PGE(2) might have on primary human CD4+ T cells, we used a whole genome-based transcriptional approach and show that PGE(2) severely limited changes of gene expression induced by signaling through the T cell receptor and CD28. This data suggests an interference of PGE(2) at an early step of T cell receptor signaling: indeed, PGE(2) stimulation of T cells leads to inactivation of lck and reduced phosphorylation of ZAP70. Antiapoptotic genes escaped PGE(2)-induced inhibition resulting in partial protection from apoptosis in response to irradiation or Fas-mediated signaling. As a functional consequence, PGE(2)-treated CD4+ T cells are arrested in the cell cycle associated with up-regulation of the cyclin/cyclin-dependent kinase inhibitor p27(kip1). Most importantly, CD4+ T cells in Hodgkin's lymphoma show similar regulation of genes that were altered in vitro by PGE(2) in T cells from healthy individuals. These data strongly suggest that PGE(2) is an important factor leading to CD4+ T cell impairment observed in Hodgkin's lymphoma.
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Affiliation(s)
- Jens M Chemnitz
- Molecular Tumor Biology and Tumor Immunology, Department of Internal Medicine I, University of Cologne, Joseph-Stelzmann-Strasse 9, 50924 Cologne, Germany
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20
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Willis D, Zhang Y, Molloy GR. Transcription of brain creatine kinase in U87-MG glioblastoma is modulated by factor AP2. ACTA ACUST UNITED AC 2005; 1728:18-33. [PMID: 15777731 DOI: 10.1016/j.bbaexp.2005.01.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2004] [Revised: 01/14/2005] [Accepted: 01/19/2005] [Indexed: 11/28/2022]
Abstract
Our previous studies established in U87-MG glioblastoma cells that elevated cAMP increased transcription of the endogenous as well as a transiently-transfected brain creatine kinase (CKB) gene, despite the absence of a cAMP response element (CRE) in the CKB proximal promoter. This report employed transfection to show that the transcription of CKB in U87 cells is induced by transcription factor AP2alpha, which is known to be activated by cAMP. Dominant-negative forms of AP2alpha not only prevented the AP2alpha-mediated activation of CKB but also blocked the cAMP-mediated increase in CKB transcription caused by forskolin treatment. The mutation of the four potential AP2 elements within the CKB proximal promoter showed that induction of CKB by AP2 was mediated principally through the AP2 element located at -50 bp in the promoter. Electromobility shift assays revealed a protein in U87 nuclear extracts that bound to a consensus AP2alpha element as well as to the (-50) AP2 element in CKB. Interestingly, the CKB (-50) AP2 element contains GCCAATGGG which also bound NF-Y, the CCAAT-binding protein, suggesting that interplay between AP2 and NF-Y may modulate CKB transcription. This is the first report of a role for AP2 in the regulation of CKB transcription and of an AP2 element within which an NF-Y site is located.
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Affiliation(s)
- Dianna Willis
- Department of Biological Sciences, University of Delaware, 117 Wolf Hall, Newark, DE 19716, USA
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21
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Kim MJ, Park KG, Lee KM, Kim HS, Kim SY, Kim CS, Lee SL, Chang YC, Park JY, Lee KU, Lee IK. Cilostazol inhibits vascular smooth muscle cell growth by downregulation of the transcription factor E2F. Hypertension 2005; 45:552-6. [PMID: 15723965 DOI: 10.1161/01.hyp.0000158263.64320.eb] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Neointimal formation, the leading cause of restenosis, is caused by proliferation of vascular smooth muscle cells (VSMCs). Patients with diabetes mellitus have higher restenosis rates after coronary angioplasty than nondiabetic patients. Cilostazol, a selective type 3 phosphodiesterase inhibitor, is currently used to treat patients with diabetic vascular complications. Cilostazol is a potent antiplatelet agent that inhibits VSMC proliferation. In the present study, we examine whether the antiproliferative effect of cilostazol on VSMCs is mediated by inhibition of an important cell cycle transcription factor, E2F. Cilostazol inhibited the proliferation of human VSMCs in response to high glucose in vitro and virtually abolished neointimal formation in rats subjected to carotid artery injury in vivo. Moreover, the compound suppressed high-glucose-induced E2F-DNA binding activity, and the expression of E2F1, E2F2, cyclin A, and PCNA proteins. These data suggest that the beneficial effects of cilostazol on high-glucose-stimulated proliferation of VSMCs are mediated by the downregulation of E2F activity and expression of its downstream target genes, including E2F1, E2F2, cyclin A, and PCNA.
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Affiliation(s)
- Mi-Jung Kim
- Department of Internal Medicine, Keimyung University School of Medicine, Daegu, South Korea
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22
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Naderi S, Gutzkow KB, Låhne HU, Lefdal S, Ryves WJ, Harwood AJ, Blomhoff HK. cAMP-induced degradation of cyclin D3 through association with GSK-3beta. J Cell Sci 2004; 117:3769-83. [PMID: 15252116 DOI: 10.1242/jcs.01210] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
In this study we report a new mechanism whereby cyclic AMP (cAMP) regulates the cell-cycle machinery. We demonstrate that elevation of intracellular levels of cAMP promotes degradation of cyclin D3 in proteasomes, and that this occurs via glycogen synthase kinase-3beta (GSK-3beta)-mediated phosphorylation of cyclin D3 at Thr-283. Elevation of cAMP did not change the subcellular distribution of either cyclin D3 or GSK-3beta. However, cAMP promoted the interaction between cyclin D3 and GSK-3beta both in vitro and in vivo, indicating that GSK-3beta-mediated phosphorylation of cyclin D3 might require the association between the two proteins. These results demonstrate how cAMP enhances degradation of cyclin D3. Furthermore, we provide evidence for a novel mechanism by which GSK-3beta might phosphorylate unprimed substrates in vivo.
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Affiliation(s)
- Soheil Naderi
- Department of Medical Biochemistry, University of Oslo, P.O. Box 1112 Blindern, Oslo, N-0317, Norway
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23
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Hleb M, Murphy S, Wagner EF, Hanna NN, Sharma N, Park J, Li XC, Strom TB, Padbury JF, Tseng YT, Sharma S. Evidence for Cyclin D3 as a Novel Target of Rapamycin in Human T Lymphocytes. J Biol Chem 2004; 279:31948-55. [PMID: 15131122 DOI: 10.1074/jbc.m400638200] [Citation(s) in RCA: 40] [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
The immunosuppressant rapamycin has been shown to inhibit G(1)/S transition of the cell cycle. This inhibition is thought to be mediated by maintenance of the threshold levels of cyclin-dependent kinase (CDK) inhibitor p27(Kip1) (p27) and inhibition of p70 s6 kinase (p70(s6k)). However, recent evidence suggests that cells still remain sensitive to rapamycin in the absence of functional p27 or p70(s6k). Here, we show that rapamycin represses cyclin D3 levels in activated human T lymphocytes with no inhibitory effects on cyclin D2. Furthermore, rapamycin elicits similar cyclin D3 modulatory effects in B lymphocytes. The overall effect of rapamycin on cyclin D3 leads to impaired formation of active complexes with Cdk4 or Cdk6 and subsequent inhibition of cyclin D3/CDK kinase activity. Decrease in cyclin D3 protein levels is due to translational repression and not due to attenuated transcription of the cyclin D3 gene. Importantly, stable overexpression of cyclin D3 (2-2.5 fold) in Jurkat T cell transfectants renders them resistant to lower doses (1-10 ng/ml) of rapamycin. These results point to a critical role of cyclin D3 in rapamycin-mediated immunosuppressive effects in T cells and cell cycle regulation in lymphocytes in general.
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Affiliation(s)
- Marija Hleb
- Department of Pediatrics, Brown Medical School, Women and Infant's Hospital of Rhode Island, Providence, Rhode Island 02905, USA
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24
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Kalma Y, Granot I, Galiani D, Barash A, Dekel N. Luteinizing hormone-induced connexin 43 down-regulation: inhibition of translation. Endocrinology 2004; 145:1617-24. [PMID: 14684606 DOI: 10.1210/en.2003-1051] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The coordinated function of the different compartments of the follicle, the oocyte and the somatic cumulus/granulosa cells, is enabled by the presence of a network of cell-to-cell communication generated by gap junctions. Connexin 43 (Cx43) is the most abundant gap junction protein expressed by the ovarian follicle. The expression of Cx43 is subjected to the control of gonadotropins as follows: FSH up-regulates, whereas LH down-regulates its levels. The aim of this study was to explore the mechanism by which LH reduces the levels of Cx43 and to identify the signal transduction pathway involved in this process. The effect of LH was studied in vitro using isolated intact ovarian follicles. The possible mediators of LH-induced Cx43 down-regulation were examined by incubating the follicles with LH in the presence or absence of inhibitors of protein kinase A (PKA) and of MAPK signaling pathways. Our experiments revealed a 3-h half-life of Cx43 in both control and LH-treated follicles, suggesting that LH did not affect the rate of Cx43 degradation. We further demonstrated that the level of Cx43 mRNA was not significantly influenced by this gonadotropin. However, upon LH administration, [(35)S]methionine incorporation into Cx43 protein was remarkably reduced. The LH-induced arrest of Cx43 synthesis was counteracted by inhibitors of both the PKA and the MAPK cascades. We show herein that LH inhibits Cx43 expression by reducing its rate of translation and that this effect is mediated by both PKA and MAPK.
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Affiliation(s)
- Yael Kalma
- Department of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel
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25
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Alexandre-Moreira MS, Piuvezam MR, Peçanha LMT. Modulation of B lymphocyte function by an aqueous fraction of the ethanol extract of Cissampelos sympodialis Eichl (Menispermaceae). Braz J Med Biol Res 2003; 36:1511-22. [PMID: 14576907 DOI: 10.1590/s0100-879x2003001100010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cissampelos sympodialis Eichl species are used in folk medicine for the treatment of asthma, arthritis and rheumatism. In the present study, we investigated the immunomodulatory effect of an aqueous fraction of a 70% (v/v) ethanol extract of C. sympodialis leaves on B lymphocyte function. The hydroalcoholic extract inhibited the in vitro proliferative response of resting B cells induced by LPS (IC50 = 17.2 g/ml), anti-delta-dextran (IC50 = 13.9 g/ml) and anti-IgM (IC50 = 24.3 g/ml) but did not affect the anti-MHC class II antibody-stimulated proliferative response of B cell blasts obtained by stimulation with IL-4 and anti-IgM. Incubation with the hydroalcoholic extract used at 50 g/ml induced a 700% increase in intracellular cAMP levels. IgM secretion by resting B cells (obtained from normal mice) and polyclonally activated B cells (obtained from Trypanosoma cruzi-infected animals) was inhibited by the hydroalcoholic extract. The latter were more sensitive to the hydroalcoholic extract since 6.5 g/ml induced a 20% inhibition in the response of cells from normal mice while it inhibited the response of B cells from infected animals by 75%. The present data indicate that the alcoholic extract of C. sympodialis inhibited B cell function through an increase in intracellular cAMP levels. The finding that the hydroalcoholic extract inhibited immunoglobulin secretion suggests a therapeutic use for the extract from C. sympodialis in conditions associated with unregulated B cell function and enhanced immunoglobulin secretion. Finally, the inhibitory effect of the hydroalcoholic extract on B cells may indicate an anti-inflammatory effect of this extract.
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Affiliation(s)
- M S Alexandre-Moreira
- Departamento de Imunologia, Instituto de Microbiologia Prof. Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brasil
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26
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Gutzkow KB, Låhne HU, Naderi S, Torgersen KM, Skålhegg B, Koketsu M, Uehara Y, Blomhoff HK. Cyclic AMP inhibits translation of cyclin D3 in T lymphocytes at the level of elongation by inducing eEF2-phosphorylation. Cell Signal 2003; 15:871-81. [PMID: 12834812 DOI: 10.1016/s0898-6568(03)00038-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The purpose of the present study was to understand the mechanism by which activated protein kinase A (PKA) leads to down-regulation of cyclin D3 in lymphocytes. By using Jurkat cells as a model system, we have been able to demonstrate that cyclin D3 is reduced at the level of translation by inhibition of elongation. One of the important factors involved in translational elongation is the eukaryotic elongation factor 2 (eEF2). eEF2 promotes translation in its unphosphorylated form, and we observed a rapid phosphorylation of the eEF2-protein upon forskolin treatment. When using specific inhibitors of the eEF2-kinase prior to forskolin treatment, we were able to inhibit the increased phosphorylation of eEF2. Furthermore, inhibition of eEF2-kinase prevented the forskolin-mediated down-regulation of cyclin D3. Taken together, it appears that activation of PKA in Jurkat cells reduces the expression of cyclin D3 at the level of translational elongation by increasing the phosphorylation of eEF2 and thereby inhibiting its activity.
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Affiliation(s)
- Kristine B Gutzkow
- Institute of Medical Biochemistry, University of Oslo, PO Box 1112, Blindern, N-0317, Oslo, Norway
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27
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Thiel M, Caldwell CC, Sitkovsky MV. The critical role of adenosine A2A receptors in downregulation of inflammation and immunity in the pathogenesis of infectious diseases. Microbes Infect 2003; 5:515-26. [PMID: 12758281 DOI: 10.1016/s1286-4579(03)00068-6] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Adenosine can be described as a retaliatory metabolite, the production and release of which is usually enhanced under adverse environmental conditions. Binding via specific receptors, adenosine activates endogenous protective mechanisms aiming at the restoration of tissue homeostasis. While adenosinergic downregulation of tissue damage is beneficial in acute inflammation, chronic suppression of the immune system by adenosine may account for immunoparalysis in long-term septic patients.
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Affiliation(s)
- Manfred Thiel
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 10/11N311, 10 Center Drive, Bethesda, MD 20892-1892, USA
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28
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Andersson KB, Kowenz-Leutz E, Brendeford EM, Tygsett AHH, Leutz A, Gabrielsen OS. Phosphorylation-dependent down-regulation of c-Myb DNA binding is abrogated by a point mutation in the v-myb oncogene. J Biol Chem 2003; 278:3816-24. [PMID: 12456674 DOI: 10.1074/jbc.m209404200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The viral Myb (v-Myb) oncoprotein of the avian myeloblastosis virus (AMV) is an activated form of the cellular transcription factor c-Myb causing acute monoblastic leukemia in chicken. Oncogenic v-Myb alterations include N- and C-terminal deletions as well as point mutations. Whereas truncations in Myb cause loss of various protein modifications, none of the point mutations in v-Myb has been directly linked to protein modifications. Here we show that the DNA-binding domain of c-Myb can be phosphorylated on serine 116 by the catalytic subunit of protein kinase A. Phosphorylation of Ser(116) differentially destabilizes a subtype of c-Myb-DNA complexes. The V117D mutation of the AMV v-Myb oncoprotein abolishes phosphorylation of the adjacent Ser(116) residue. Modification of Ser(116) was also detected in live cells in c-Myb, but not in AMV v-Myb. Phosphorylation-mimicking mutants of c-Myb failed to activate the resident mim-1 gene. Our data imply that protein kinase A or a kinase with similar specificity negatively regulates c-Myb function, including collaboration with C/EBP, and that the leukemogenic AMV v-Myb version evades inactivation by a point mutation that abolishes a phosphoacceptor consensus site. This suggests a novel link between Myb, a signal transduction pathway, cooperativity with C/EBP, and a point mutation in the myb oncogene.
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29
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Stork PJS, Schmitt JM. Crosstalk between cAMP and MAP kinase signaling in the regulation of cell proliferation. Trends Cell Biol 2002; 12:258-66. [PMID: 12074885 DOI: 10.1016/s0962-8924(02)02294-8] [Citation(s) in RCA: 695] [Impact Index Per Article: 31.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Hormonal stimulation of cyclic adenosine monophosphate (cAMP) and the cAMP-dependent protein kinase PKA regulates cell growth by multiple mechanisms. A hallmark of cAMP is its ability to stimulate cell growth in many cell types while inhibiting cell growth in others. In this review, the cell type-specific effects of cAMP on the mitogen-activated protein (MAP) kinase (also called extracellular signal-regulated kinase, or ERK) cascade and cell proliferation are examined. Two basic themes are discussed. First, the capacity of cAMP for either positive or negative regulation of the ERK cascade accounts for many of the cell type-specific actions of cAMP on cell proliferation. Second, there are several specific mechanisms involved in the inhibition or activation of ERKs by cAMP. Emerging new data suggest that one of these mechanisms might involve the activation of the GTPase Rap1, which can activate or inhibit ERK signaling in a cell-specific manner.
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Affiliation(s)
- Philip J S Stork
- Vollum Institute and the Dept of Cell and Developmental Biology, Oregon Health and Science University, Portland, OR 97201, USA.
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30
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Mei FC, Qiao J, Tsygankova OM, Meinkoth JL, Quilliam LA, Cheng X. Differential signaling of cyclic AMP: opposing effects of exchange protein directly activated by cyclic AMP and cAMP-dependent protein kinase on protein kinase B activation. J Biol Chem 2002; 277:11497-504. [PMID: 11801596 DOI: 10.1074/jbc.m110856200] [Citation(s) in RCA: 233] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The recent discovery of Epac, a novel cAMP receptor protein, opens up a new dimension in studying cAMP-mediated cell signaling. It is conceivable that many of the cAMP functions previously attributed to cAMP-dependent protein kinase (PKA) are in fact also Epac-dependent. The finding of an additional intracellular cAMP receptor provides an opportunity to further dissect the divergent roles that cAMP exerts in different cell types. In this study, we probed cross-talk between cAMP signaling and the phosphatidylinositol 3-kinase/PKB pathways. Specifically, we examined the modulatory effects of cAMP on PKB activity by monitoring the specific roles that Epac and PKA play individually in regulating PKB activity. Our study suggests a complex regulatory scheme in which Epac and PKA mediate the opposing effects of cAMP on PKB regulation. Activation of Epac leads to a phosphatidylinositol 3-kinase-dependent PKB activation, while stimulation of PKA inhibits PKB activity. Furthermore, activation of PKB by Epac requires the proper subcellular targeting of Epac. The opposing effects of Epac and PKA on PKB activation provide a potential mechanism for the cell type-specific differential effects of cAMP. It is proposed that the net outcome of cAMP signaling is dependent upon the dynamic abundance and distribution of intracellular Epac and PKA.
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Affiliation(s)
- Fang C Mei
- Department of Pharmacology, School of Medicine, The University of Texas Medical Branch, Galveston, Texas 77555, USA
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Gützkow KB, Naderi S, Blomhoff HK. Forskolin-mediated G1 arrest in acute lymphoblastic leukaemia cells: phosphorylated pRB sequesters E2Fs. J Cell Sci 2002; 115:1073-82. [PMID: 11870225 DOI: 10.1242/jcs.115.5.1073] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Increased intracellular levels of cAMP, induced by forskolin, lead to permanent G1 arrest of Reh cells. As expected, we observed a rapid dephosphorylation of the retinoblastoma protein (pRB) within 2 hours of forskolin treatment concomitant with reduced activity of the pRB-specific kinases. Interestingly, however, the dephosphorylation of pRB, as well as the inhibition of the kinase activities, was only transient, despite the permanent arrest of cells in G1. Importantly, although the pRB-specific kinases were fully active after 48 hours, pRB became only partially rephosphorylated.
The transient dephosphorylation of pRB could be explained by the transient decrease in the activities of the pRB-specific kinases, but to understand why pRB became only partially rephosphorylated, despite fully activated kinases,we postulated that cAMP could activate a pRB-directed phosphatase. It was therefore interesting to find that the phosphatase inhibitor, tautomycin, was able to abolish the forskolin-mediated dephosphorylation of pRB, without increasing the activities of the pRB-specific kinases.
To understand how Reh cells expressing hyperphosphorylated forms of pRB can remain arrested in G1, we used three different methods to test for the ability of pRB to form functional complexes with the family of E2F transcription factors. As expected, we observed an increased complex formation between E2F-1, E2F-4 and pRB after 2 hours when pRB was in its most dephosphorylated state. Suprisingly, however, prolonged treatment with forskolin, which induced partial rephosphorylation of pRB, in fact further increased the complex formation between the E2Fs and pRB, and this also resulted in reduced E2F-promoter activity in vivo. These data imply that in Reh cells, partially phosphorylated forms of pRB retain the ability to inhibit E2F-promoter activity, and thereby prevent cells from entering into S-phase.
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Affiliation(s)
- Kristine Bjerve Gützkow
- Institute of Medical Biochemistry, University of Oslo, PO Box 1112, Blindern, N-0317, Oslo, Norway
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Sonoki T, Harder L, Horsman DE, Karran L, Taniguchi I, Willis TG, Gesk S, Steinemann D, Zucca E, Schlegelberger B, Solé F, Mungall AJ, Gascoyne RD, Siebert R, Dyer MJ. Cyclin D3 is a target gene of t(6;14)(p21.1;q32.3) of mature B-cell malignancies. Blood 2001; 98:2837-44. [PMID: 11675358 DOI: 10.1182/blood.v98.9.2837] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Chromosomal translocation t(6;14)(p21.1;q32.3) has been reported as a rare but recurrent event not only in myeloma and plasma cell leukemia but also in diffuse large B-cell non-Hodgkin lymphoma (B-NHL) (diffuse large B-cell lymphoma [DLBCL]) and splenic lymphoma with villous lymphocytes (SLVL); however, the nature of the target gene(s) has not been determined. This study identified t(6;14)(p21.1;q32.3) in 3 cases of transformed extranodal marginal zone B-NHL, in 1 case of SLVL, and in 1 case of a low-grade B-cell lymphoproliferative disorder. In a sixth case, a CD5(+) DLBCL, the translocation was identified by molecular cloning in the absence of cytogenetically detectable change. Two chromosomal translocation breakpoints were cloned by using long-distance inverse polymerase chain reaction methods. Comparison with the genomic sequence for chromosome 6p21.1 showed breakpoints approximately 59 and 73.5 kilobases 5' of the cyclin D3 (CCND3) gene with no other identifiable transcribed sequences in the intervening region. Although Southern blotting with derived genomic 6p21.1 probes failed to detect other rearrangements, fluorescent in situ hybridization assays, using BAC (bacterial artificial chromosome) clones spanning and flanking the CCND3 locus, along with probes for IGH confirmed localization of 6p21.1 breakpoints within the same region, as well as fusion of the CCND3 and IGH loci. Furthermore, in all cases, high-level expression of CCND3 was demonstrated at RNA and/or protein levels by Northern and Western blotting and by immunohistochemistry. These data implicate CCND3 as a dominant oncogene in the pathogenesis and transformation in several histologic subtypes of mature B-cell malignancies with t(6;14)(p21.1;q32.3) and suggest that CCND3 overexpression seen in about 10% of DLBCL cases may have a genetic basis.
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MESH Headings
- Adult
- Aged
- B-Lymphocytes/chemistry
- B-Lymphocytes/pathology
- B-Lymphocytes/ultrastructure
- Base Sequence
- Chromosome Breakage/genetics
- Chromosomes, Human, Pair 14
- Chromosomes, Human, Pair 6
- Cloning, Molecular
- Cyclin D3
- Cyclins/genetics
- Female
- Humans
- Immunoglobulin Heavy Chains/genetics
- Immunohistochemistry
- In Situ Hybridization, Fluorescence
- Lymphoma, B-Cell/chemistry
- Lymphoma, B-Cell/genetics
- Lymphoma, B-Cell/pathology
- Lymphoproliferative Disorders/genetics
- Lymphoproliferative Disorders/pathology
- Male
- Middle Aged
- Molecular Sequence Data
- Translocation, Genetic/genetics
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Affiliation(s)
- T Sonoki
- Academic Department of Haematology and Cytogenetics, Institute of Cancer Research, Sutton, United Kingdom
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van Oirschot BA, Stahl M, Lens SM, Medema RH. Protein kinase A regulates expression of p27(kip1) and cyclin D3 to suppress proliferation of leukemic T cell lines. J Biol Chem 2001; 276:33854-60. [PMID: 11457838 DOI: 10.1074/jbc.m104395200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Peripheral homeostasis and tolerance requires the suppression or removal of excessive or harmful T lymphocytes. This can occur either by apoptosis through active antigen-induced death or cytokine withdrawal. Alternatively, T cell activation can be suppressed by agents that activate the cAMP-dependent protein kinase (PKA) signaling pathway, such as prostaglandin E2. Stimulation of PKA inhibits lymphocyte proliferation and immune effector functions. Here we have investigated the mechanism by which activation of PKA induces inhibition of proliferation in human leukemic T cell lines. Using a variety of agents that stimulate PKA, we can arrest Jurkat and H9 leukemic T cells in the G(1) phase of the cell cycle, whereas cell viability is hardly affected. This G(1) arrest is associated with an inhibition of cyclin D/Cdk and cyclin E/Cdk kinase activity. Interestingly, expression of cyclin D3 is rapidly reduced by PKA activation, whereas expression of the Cdk inhibitor p27(kip1) is induced. Ectopic expression of cyclin D3 can override the growth suppression induced by PKA activation to some extent, indicating that growth inhibition of leukemic T cells by PKA activation is partially dependent on down-regulation of cyclin D3 expression. Taken together our data suggest that immunosuppression by protein kinase A involves regulation of both cyclin D3 and p27(kip1) expression.
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Affiliation(s)
- B A van Oirschot
- Jordan Laboratory for Hemato-Oncology, G03-647, Utrecht Medical Center, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
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Staples KJ, Bergmann M, Tomita K, Houslay MD, McPhee I, Barnes PJ, Giembycz MA, Newton R. Adenosine 3',5'-cyclic monophosphate (cAMP)-dependent inhibition of IL-5 from human T lymphocytes is not mediated by the cAMP-dependent protein kinase A. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2001; 167:2074-80. [PMID: 11489990 DOI: 10.4049/jimmunol.167.4.2074] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
IL-5 is implicated in the pathogenesis of asthma and is predominantly released from T lymphocytes of the Th2 phenotype. In anti-CD3 plus anti-CD28-stimulated PBMC, albuterol, isoproterenol, rolipram, PGE2, forskolin, cholera toxin, and the cAMP analog, 8-bromoadenosine cAMP (8-Br-cAMP) all inhibited the release of IL-5 and lymphocyte proliferation. Although all of the above compounds share the ability to increase intracellular cAMP levels and activate protein kinase (PK) A, the PKA inhibitor H-89 failed to ablate the inhibition of IL-5 production mediated by 8-Br-cAMP, rolipram, forskolin, or PGE2. Similarly, H-89 had no effect on the cAMP-mediated inhibition of lymphocyte proliferation. Significantly, these observations occurred at a concentration of H-89 (3 microM) that inhibited both PKA activity and CREB phosphorylation in intact cells. Additional studies showed that the PKA inhibitors H-8, 8-(4-chlorophenylthio) adenosine-3',5'-cyclic monophosphorothioate Rp isomer, and a myristolated PKA inhibitor peptide also failed to block the 8-Br-cAMP-mediated inhibition of IL-5 release from PBMC. Likewise, a role for PKG was considered unlikely because both activators and inhibitors of this enzyme had no effect on IL-5 release. Western blotting identified Rap1, a downstream target of the cAMP-binding proteins, exchange protein directly activated by cAMP/cAMP-guanine nucleotide exchange factors 1 and 2, in PBMC. However, Rap1 activation assays revealed that this pathway is also unlikely to be involved in the cAMP-mediated inhibition of IL-5. Taken together, these results indicate that cAMP-elevating agents inhibit IL-5 release from PBMC by a novel cAMP-dependent mechanism that does not involve the activation of PKA.
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Affiliation(s)
- K J Staples
- Department of Thoracic Medicine, National Heart and Lung Institute, Imperial College School of Medicine, London, United Kingdom
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