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Liu M, Zhang Y, Jian Y, Gu L, Zhang D, Zhou H, Wang Y, Xu ZX. The regulations of telomerase reverse transcriptase (TERT) in cancer. Cell Death Dis 2024; 15:90. [PMID: 38278800 PMCID: PMC10817947 DOI: 10.1038/s41419-024-06454-7] [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: 09/22/2023] [Revised: 01/04/2024] [Accepted: 01/08/2024] [Indexed: 01/28/2024]
Abstract
Abnormal activation of telomerase occurs in most cancer types, which facilitates escaping from cell senescence. As the key component of telomerase, telomerase reverse transcriptase (TERT) is regulated by various regulation pathways. TERT gene changing in its promoter and phosphorylation respectively leads to TERT ectopic expression at the transcription and protein levels. The co-interacting factors play an important role in the regulation of TERT in different cancer types. In this review, we focus on the regulators of TERT and these downstream functions in cancer regulation. Determining the specific regulatory mechanism will help to facilitate the development of a cancer treatment strategy that targets telomerase and cancer cell senescence. As the most important catalytic subunit component of telomerase, TERT is rapidly regulated by transcriptional factors and PTM-related activation. These changes directly influence TERT-related telomere maintenance by regulating telomerase activity in telomerase-positive cancer cells, telomerase assembly with telomere-binding proteins, and recruiting telomerase to the telomere. Besides, there are also non-canonical functions that are influenced by TERT, including the basic biological functions of cancer cells, such as proliferation, apoptosis, cell cycle regulation, initiating cell formation, EMT, and cell invasion. Other downstream effects are the results of the influence of transcriptional factors by TERT. Currently, some small molecular inhibitors of TERT and TERT vaccine are under research as a clinical therapeutic target. Purposeful work is in progress.
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Affiliation(s)
- Mingdi Liu
- Key Laboratory of Pathobiology, Ministry of Education, Jilin University, Changchun, 130021, Jilin, China
| | - Yuning Zhang
- Key Laboratory of Pathobiology, Ministry of Education, Jilin University, Changchun, 130021, Jilin, China
| | - Yongping Jian
- Key Laboratory of Pathobiology, Ministry of Education, Jilin University, Changchun, 130021, Jilin, China
| | - Liting Gu
- Key Laboratory of Pathobiology, Ministry of Education, Jilin University, Changchun, 130021, Jilin, China
| | - Dan Zhang
- Key Laboratory of Pathobiology, Ministry of Education, Jilin University, Changchun, 130021, Jilin, China
| | - Honglan Zhou
- Department of Urology, The First Hospital of Jilin University, Changchun, 130021, Jilin, China.
| | - Yishu Wang
- Key Laboratory of Pathobiology, Ministry of Education, Jilin University, Changchun, 130021, Jilin, China.
| | - Zhi-Xiang Xu
- Key Laboratory of Pathobiology, Ministry of Education, Jilin University, Changchun, 130021, Jilin, China.
- Department of Urology, The First Hospital of Jilin University, Changchun, 130021, Jilin, China.
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Gap Junction Intercellular Communication in the Carcinogenesis Hallmarks: Is This a Phenomenon or Epiphenomenon? Cells 2019; 8:cells8080896. [PMID: 31416286 PMCID: PMC6721698 DOI: 10.3390/cells8080896] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 08/03/2019] [Accepted: 08/12/2019] [Indexed: 12/24/2022] Open
Abstract
If occupational tumors are excluded, cancer causes are largely unknown. Therefore, it appeared useful to work out a theory explaining the complexity of this disease. More than fifty years ago the first demonstration that cells communicate with each other by exchanging ions or small molecules through the participation of connexins (Cxs) forming Gap Junctions (GJs) occurred. Then the involvement of GJ Intercellular Communication (GJIC) in numerous physiological cellular functions, especially in proliferation control, was proven and accounts for the growing attention elicited in the field of carcinogenesis. The aim of the present paper is to verify and discuss the role of Cxs, GJs, and GJIC in cancer hallmarks, pointing on the different involved mechanisms in the context of the multi-step theory of carcinogenesis. Functional GJIC acts both as a tumor suppressor and as a tumor enhancer in the metastatic stage. On the contrary, lost or non-functional GJs allow the uncontrolled proliferation of stem/progenitor initiated cells. Thus, GJIC plays a key role in many biological phenomena or epiphenomena related to cancer. Depending on this complexity, GJIC can be considered a tumor suppressor in controlling cell proliferation or a cancer ally, with possible preventive or therapeutic implications in both cases.
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Ahn EH, Yang H, Hsieh CY, Sun W, Chang CC, Schroeder JJ. Evaluation of chemotherapeutic and cancer-protective properties of sphingosine and C2-ceramide in a human breast stem cell derived carcinogenesis model. Int J Oncol 2018; 54:655-664. [PMID: 30483770 PMCID: PMC6317677 DOI: 10.3892/ijo.2018.4641] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 08/30/2018] [Indexed: 02/07/2023] Open
Abstract
The overall goal of the present study was to evaluate the chemotherapeutic and cancer-protective properties of D-erythro-sphingosine (sphingosine) and C2-ceramide using a human breast epithelial cell (HBEC) culture system, which represents multiple-stages of breast carcinogenesis. The HBEC model includes Type I HBECs (normal stem), Type II HBECs (normal differentiated) and transformed cells (immortal/non-tumorigenic cells and tumorigenic cells, which are transformed from the same parental normal stem cells). The results of the present study indicate that sphingosine preferentially inhibits proliferation and causes death of normal stem cells (Type I), tumorigenic cells, and MCF7 breast cancer cells, but not normal differentiated cells (Type II). In contrast to the selective anti-proliferative effects of sphingosine, C2-ceramide inhibits proliferation of normal differentiated cells as well as normal stem cells, tumorigenic cells, and MCF7 cancer cells with similar potency. Both sphingosine and C2-ceramide induce apoptosis in tumorigenic cells. Among the sphingosine stereoisomers (D-erythro, D-threo, L-erythro, and L-threo) and sphinganine that were tested, L-erythro-sphingosine most potently inhibits proliferation of tumorigenic cells. The inhibition of breast tumorigenic/cancer cell proliferation by sphingosine was accompanied by inhibition of telomerase activity. Sphingosine at non-cytotoxic concentrations, but not C2-ceramide, induces differentiation of normal stem cells (Type I), thereby reducing the number of stem cells that are more susceptible to neoplastic transformation. To the best of our knowledge, the present study demonstrates one of the first results that sphingosine can be a potential chemotherapeutic and cancer-protective agent, whereas C2-ceramide is not an ideal chemotherapeutic and cancer-protective agent due to its anti-proliferative effects on Type II HBECs and its inability to induce the differentiation of Type I to Type II HBECs.
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Affiliation(s)
- Eun Hyun Ahn
- Department of Pathology and 2Institute of Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA 98195, USA
| | - Hong Yang
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, MI 48824, USA
| | - Ching-Yi Hsieh
- Department of Pediatrics and Human Development, Michigan State University, East Lansing, MI 48824, USA
| | - Wei Sun
- Department of Pediatrics and Human Development, Michigan State University, East Lansing, MI 48824, USA
| | - Chia-Cheng Chang
- Department of Pediatrics and Human Development, Michigan State University, East Lansing, MI 48824, USA
| | - Joseph J Schroeder
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, MI 48824, USA
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Chu WK, Hung LM, Hou CW, Chen JK. Heterogeneous ribonucleoprotein F regulates YAP expression via a G-tract in 3'UTR. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2018; 1862:12-24. [PMID: 30312683 DOI: 10.1016/j.bbagrm.2018.10.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 10/05/2018] [Accepted: 10/06/2018] [Indexed: 10/28/2022]
Abstract
The Yes-associated protein (YAP) is a transcription coactivator that plays crucial roles in organ size control and tumorigenesis, and was demonstrated to be inhibited by the Hippo signaling pathway. To date, the molecular mechanisms regulating the expression of YAP in human cells remain unknown. In the present study, we found that hnRNP F and hnRNP U negatively regulate YAP expression. We also showed that downregulation of YAP expression by hnRNP F and hnRNP U was not at the transcriptional level. Knockdown of hnRNP F or hnRNP U increased YAP mRNA stability, suggesting the downregulation of YAP expression was by a post-transcriptional mechanism. A putative hnRNP F binding site was identified in the YAP 3'UTR at 685 to 698, and deletion of this putative hnRNP F element abolished the down-regulation effect of YAP mRNA stability by hnRNP F. Binding of the hnRNP F to the YAP 3'UTR was demonstrated by Cross-linked RNA Immunoprecipitation. mRNA stability is a possible secondary effect of alternative splicing or other nuclear process. Understanding the regulation of YAP expression would provide insights into the mechanisms underlying the maintenance of tissue size homeostasis and tumorigenesis.
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Affiliation(s)
- Wing-Keung Chu
- Department of Physiology, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan; Healthy and Aging Research Center, Chang Gung University, Taoyuan 333, Taiwan
| | - Li-Man Hung
- Healthy and Aging Research Center, Chang Gung University, Taoyuan 333, Taiwan; Department of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan
| | - Chun-Wei Hou
- Healthy and Aging Research Center, Chang Gung University, Taoyuan 333, Taiwan
| | - Jan-Kan Chen
- Department of Physiology, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan; Healthy and Aging Research Center, Chang Gung University, Taoyuan 333, Taiwan.
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Zhang F, Wang XL, Shi J, Wang SF, Yin Y, Yang YS, Zhang WM, Zhu HL. Synthesis, molecular modeling and biological evaluation of N-benzylidene-2-((5-(pyridin-4-yl)-1,3,4-oxadiazol-2-yl)thio)acetohydrazide derivatives as potential anticancer agents. Bioorg Med Chem 2013; 22:468-77. [PMID: 24286761 DOI: 10.1016/j.bmc.2013.11.004] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Revised: 11/03/2013] [Accepted: 11/04/2013] [Indexed: 12/12/2022]
Abstract
A series of new 1,3,4-oxadiazole derivatives (6a-6x) containing pyridine and acylhydrazone moieties were synthesized and developed as potential telomerase inhibitors. The bioassay tests demonstrated that compounds 6n, 6o, 6q, 6s and 6t exhibited significant broad-spectrum anticancer activity with IC₅₀ range from 0.76 to 9.59 μM against the four cancer cell lines (HEPG2, MCF7, SW1116 and BGC823). Moreover, all the title compounds were assayed for telomerase inhibition using the TRAP-PCR-ELISA assay. Compound 6s showed the highest anticancer activity with IC₅₀ of 0.76-1.54 μM against the tested cancer cell lines and exhibited the most potent telomerase inhibitory activity with IC₅₀ of 1.18 ± 0.14 μM. The docking simulation was carried out to investigate a possible binding mode of compound 6s into the active site of telomerase (pdb. 3DU6) while the QSAR model was built to check the previous work as well as to introduce new directions.
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Affiliation(s)
- Fei Zhang
- Nanjing Institute for the Comprehensive Utilization of Wild Plant, Nanjing 210042, People's Republic of China; State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing 210093, People's Republic of China
| | - Xiao-Liang Wang
- Nanjing Institute for the Comprehensive Utilization of Wild Plant, Nanjing 210042, People's Republic of China; State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing 210093, People's Republic of China
| | - Jing Shi
- Nanjing Institute for the Comprehensive Utilization of Wild Plant, Nanjing 210042, People's Republic of China; State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing 210093, People's Republic of China
| | - She-Feng Wang
- Nanjing Institute for the Comprehensive Utilization of Wild Plant, Nanjing 210042, People's Republic of China; State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing 210093, People's Republic of China
| | - Yong Yin
- Nanjing Institute for the Comprehensive Utilization of Wild Plant, Nanjing 210042, People's Republic of China; State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing 210093, People's Republic of China
| | - Yu-Shun Yang
- Nanjing Institute for the Comprehensive Utilization of Wild Plant, Nanjing 210042, People's Republic of China; State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing 210093, People's Republic of China
| | - Wei-Ming Zhang
- Nanjing Institute for the Comprehensive Utilization of Wild Plant, Nanjing 210042, People's Republic of China; State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing 210093, People's Republic of China.
| | - Hai-Liang Zhu
- Nanjing Institute for the Comprehensive Utilization of Wild Plant, Nanjing 210042, People's Republic of China; State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing 210093, People's Republic of China.
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Chu WK, Dai PM, Li HL, Pao CC, Chen JK. Nanog expression is negatively regulated by protein kinase C activities in human cancer cell lines. Carcinogenesis 2013; 34:1497-509. [PMID: 23536578 DOI: 10.1093/carcin/bgt104] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Nanog is a transcription factor that is essential for the maintenance of pluripotency of the embryonic stem cells. Nanog has been shown to be expressed in various kinds of human tumors, suggesting a role in tumorigenesis. In this study, we found that Nanog expression was upregulated by inhibition of protein kinase C (PKC) activity in six human cancer cell lines examined. In a Nanog non-expressing human nasopharyngeal carcinoma cell line, NPC-076, Nanog mRNA level and protein level were both induced and dose-dependently promoted by exposure to PKC inhibitors. Knockdown experiments showed that PKCα and PKCδ were two subtypes exerted most of the effect. The reporter assay showed that Nanog promoter activity was promoted by exposure of the cells to PKC inhibitors and the effect was dependent on the presence of the Octamer-Sox composite element. The involvement of Octamer-Sox composite element was further supported by the observation that silencing of Oct4 and Sox2 in NPC-076 cells attenuated the effects of PKC inhibitors. In Nanog-expressing human embryonal carcinoma cell lines, NT2/D1 and NCCIT, Nanog expression was suppressed by exposure to PKC activator Phorbol-12-myristate-13-acetate (PMA). Further study showed that overexpression of PKCα elicited a repressive effect on Nanog expression in NT2/D1 cells. Consistently, mutation of the Octamer-Sox composite element abolished the suppressive effect by PKC activator. Nanog expression was of cellular significance in that ectopic expression in NPC-076 stimulated cell proliferation and knockdown of the endogenous Nanog expression in NT2/D1-suppressed cell proliferation.
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Affiliation(s)
- Wing-Keung Chu
- Department of Physiology, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan
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Cheng D, Zhu X, Gillespie DG, Jackson EK. Role of RACK1 in the differential proliferative effects of neuropeptide Y(1-36) and peptide YY(1-36) in SHR vs. WKY preglomerular vascular smooth muscle cells. Am J Physiol Renal Physiol 2013; 304:F770-80. [PMID: 23303411 DOI: 10.1152/ajprenal.00646.2012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Previous studies show that neuropeptide Y(1-36) (NPY(1-36)) and peptide YY(1-36) (PYY(1-36)), by engaging Y1 receptors, stimulate proliferation of spontaneous hypertensive rat (SHR) preglomerular vascular smooth muscle cells (PGVSMCs). In contrast, these peptides have little effect on proliferation of Wistar-Kyoto (WKY) PGVSMCs. Why SHR and WKY PGVSMCs differ in this regard is unknown. Because receptor for activated C kinase 1 (RACK1) can modulate cell proliferation, we tested the hypothesis that differences in RACK1 levels/localization may explain the differential response of SHR vs. WKY PGVSMCs to NPY(1-36) and PYY(1-36). Western blotting for RACK1 in subcellular fractions of cultured SHR and WKY PGVSMCs demonstrated increased levels of RACK1 in the membrane and cytoskeletal subcellular fractions of SHR vs. WKY PGVSMCs. NPY(1-36) and PYY(1-36) stimulated proliferation of SHR PGVSMCs, and siRNA knockdown of RACK1 abrogated this effect. Neither NPY(1-36) nor PYY(1-36) stimulated the proliferation of WKY PGVSMCs. However, in WKY PGVSMCs treated with a RACK1 plasmid, both NPY(1-36) and PYY(1-36) stimulated proliferation. In SHR PGVSMCs, inhibitors of the G(i)/phospholipase C/PKC pathway (a pathway known to be organized by RACK1) attenuated the ability of NPY(1-36) to stimulate the proliferation of SHR PGVSMCs. Our results suggest that RACK1 modulates the ability of PGVSMCs to respond to the proliferative actions of NPY(1-36) and PYY(1-36)and differences in RACK1 levels/localization account for, in part, differential proliferative responses to NPY(1-36) and PYY(1-36) in SHR vs. WKY PGVSMCs. Because dipeptidyl peptidase IV inhibitors increase NPY(1-36) and PYY(1-36) levels, our findings have implications for the use of such drugs in diabetic patients.
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Affiliation(s)
- Dongmei Cheng
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
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SHI Y, CUI YH, WU HG, ZHANG W, ZHAO C, LIU HR, GUO LQ, WU BL, YU AZ, ZHANG YY. Effects of mild-warming moxibustion on Bcl-2 and PKC expressions of peripheral blood in elderly people. J TRADIT CHIN MED 2012; 32:45-51. [DOI: 10.1016/s0254-6272(12)60030-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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9
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Jackson EK, Cheng D, Tofovic SP, Mi Z. Endogenous adenosine contributes to renal sympathetic neurotransmission via postjunctional A1 receptor-mediated coincident signaling. Am J Physiol Renal Physiol 2011; 302:F466-76. [PMID: 22114202 DOI: 10.1152/ajprenal.00495.2011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Adenosine A(1) receptor antagonists have diuretic/natriuretic activity and may be useful for treating sodium-retaining diseases, many of which are associated with increased renal sympathetic tone. Therefore, it is important to determine whether A(1) receptor antagonists alter renal sympathetic neurotransmission. In isolated, perfused rat kidneys, renal vasoconstriction induced by renal sympathetic nerve simulation was attenuated by 1) 1,3-dipropyl-8-p-sulfophenylxanthine (xanthine analog that is a nonselective adenosine receptor antagonist, but is cell membrane impermeable and thus does not block intracellular phosphodiesterases), 2) xanthine amine congener (xanthine analog that is a selective A(1) receptor antagonist), 3) 1,3-dipropyl-8-cyclopentylxanthine (xanthine analog that is a highly selective A(1) receptor antagonist), and 4) FK453 (nonxanthine analog that is a highly selective A(1) receptor antagonist). In contrast, FR113452 (enantiomer of FK453 that does not block A(1) receptors), MRS-1754 (selective A(2B) receptor antagonist), and VUF-5574 (selective A(3) receptor antagonist) did not alter responses to renal sympathetic nerve stimulation, and ZM-241385 (selective A(2A) receptor antagonist) enhanced responses. Antagonism of A(1) receptors did not alter renal spillover of norepinephrine. 2-Chloro-N(6)-cyclopentyladenosine (highly selective A(1) receptor agonist) increased renal vasoconstriction induced by exogenous norepinephrine, an effect that was blocked by 1,3-dipropyl-8-cyclopentylxanthine, U73122 (phospholipase C inhibitor), GF109203X (protein kinase C inhibitor), PP1 (c-src inhibitor), wortmannin (phosphatidylinositol 3-kinase inhibitor), and OSU-03012 (3-phosphoinositide-dependent protein kinase-1 inhibitor). These results indicate that adenosine formed during renal sympathetic nerve stimulation enhances the postjunctional effects of released norepinephrine via coincident signaling and contributes to renal sympathetic neurotransmission. Likely, the coincident signaling pathway is: phospholipase C → protein kinase C → c-src → phosphatidylinositol 3-kinase → 3-phosphoinositide-dependent protein kinase-1.
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Affiliation(s)
- Edwin K Jackson
- Dept. of Pharmacology and Chemical Biology, 100 Technology Dr., Rm. 514, Univ. of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA.
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10
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Xu Y. Chemistry in human telomere biology: structure, function and targeting of telomere DNA/RNA. Chem Soc Rev 2011; 40:2719-40. [DOI: 10.1039/c0cs00134a] [Citation(s) in RCA: 249] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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11
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Chen JLY, Sperry J, Ip NY, Brimble MA. Natural products targeting telomere maintenance. MEDCHEMCOMM 2011. [DOI: 10.1039/c0md00241k] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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Kavitha CV, Choudhary B, Raghavan SC, Muniyappa K. Differential regulation of MRN (Mre11-Rad50-Nbs1) complex subunits and telomerase activity in cancer cells. Biochem Biophys Res Commun 2010; 399:575-80. [PMID: 20682289 DOI: 10.1016/j.bbrc.2010.07.117] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Accepted: 07/29/2010] [Indexed: 11/26/2022]
Abstract
Several lines of evidence suggest that cancer progression is associated with up-regulation or reactivation of telomerase and the underlying mechanism remains an active area of research. The heterotrimeric MRN complex, consisting of Mre11, Rad50 and Nbs1, which is required for the repair of double-strand breaks, plays a key role in telomere length maintenance. In this study, we show significant differences in the levels of expression of MRN complex subunits among various cancer cells and somatic cells. Notably, siRNA-mediated depletion of any of the subunits of MRN complex led to complete ablation of other subunits of the complex. Treatment of leukemia and prostate cancer cells with etoposide lead to increased expression of MRN complex subunits, with concomitant decrease in the levels of telomerase activity, compared to breast cancer cells. These studies raise the possibility of developing anti-cancer drugs targeting MRN complex subunits to sensitize a subset of cancer cells to radio- and/or chemotherapy.
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Affiliation(s)
- C V Kavitha
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
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Vitiello M, Finamore E, Raieta K, Kampanaraki A, Mignogna E, Galdiero E, Galdiero M. Cellular cholesterol involvement in Src, PKC, and p38/JNK transduction pathways by porins. J Interferon Cytokine Res 2010; 29:791-800. [PMID: 19929574 DOI: 10.1089/jir.2009.0010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Biological membranes are described as a mosaic of different domains where interactions between membrane components induce the formation of subdomains with different characteristics and functions. Lipids play an important role in the formation of lipid-enriched microdomains where they dynamically associate to form platforms important for membrane protein sorting and construction of signaling complexes. Cholesterol confined in lipid domains is a crucial component required by microorganisms, directly or indirectly, to enter or exit the intracellular compartment. Cellular activation mediated by superficial bacterial component may be modified by local cholesterol depletion. Therefore, new perspectives for unconventional therapeutic intervention in Gram-negative infections may be envisaged. We tested this hypothesis by using methyl-beta-cyclodextrin (mbetaCD) as a cholesterol-complexing agent to alter the U937 plasma membrane cholesterol content. Our results demonstrate that cholesterol depletion of U937 cells inhibited Salmonella enterica serovar Typhimurium porins-mediated phosphorylation of Src kinase family, protein kinase C (PKC), JNK, and p38, while cholesterol repletion restored the phosphorylation. Lipopolysaccharide (LPS) extracted from the same bacterial strain has been used as a control. Our data demonstrate that the lack of activation of signal transduction pathway observed following cholesterol depletion differently modulates the release of interleukin-6 (IL-6) or tumor necrosis factor-alpha (TNF-alpha), suggesting that Src, associated to lipid domains, may represent an important pathway in Gram-negative-induced cellular signal.
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Affiliation(s)
- Mariateresa Vitiello
- Department of Experimental Medicine, Section of Microbiology and Clinical Microbiology, Second University of Naples, Naples 80138, Italy
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Chiang CT, Chu WK, Chow SE, Chen JK. Overexpression of delta Np63 in a human nasopharyngeal carcinoma cell line downregulates CKIs and enhances cell proliferation. J Cell Physiol 2009; 219:117-22. [PMID: 19089994 DOI: 10.1002/jcp.21656] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
p63 belongs to a member of the tumor suppressor protein p53 family. Due to alternative promoter usage, two types of p63 proteins are produced. The DeltaNp63 isoform lacks the N-terminal transactivation domain and is thought to antagonize TAp63 and p53 in target gene regulation. DeltaNp63 has been found to be overexpressed in numerous human squamous cell carcinomas, including nasopharyngeal carcinoma (NPC). However, the role of DeltaNp63 overexpression in NPC pathogenesis has not been clear. In this study, we use a DeltaNp63 overexpressing human NPC cell line (NPC-076) to explore the possible roles of DeltaNp63 in cell proliferation and cell-cycle regulation. We found that the proliferation of NPC-076 cell is greatly suppressed when the overexpressed DeltaNp63 is silenced by specific DeltaNp63 siRNA. Further studies show that DeltaNp63 silencing results in the upregulation of CKIs, including p27(kip1) and p57(kip2) in both mRNA and protein levels. Cell-cycle analysis shows that DeltaNp63 silencing also results in an increased G1 phase cell and apoptotic cell population. Our findings indicate that DeltaNp63 plays important roles in the regulation of NPC-076 cell-cycle progression, and may play a role in the maintenance of NPC-076 tumor cell phenotype.
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Affiliation(s)
- Chi-Tai Chiang
- Department of Physiology, College of Medicine, Chang Gung University, Taoyuan, Taiwan
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Weinreb O, Mandel S, Bar-Am O, Yogev-Falach M, Avramovich-Tirosh Y, Amit T, Youdim MBH. Multifunctional neuroprotective derivatives of rasagiline as anti-Alzheimer's disease drugs. Neurotherapeutics 2009; 6:163-74. [PMID: 19110207 PMCID: PMC5084264 DOI: 10.1016/j.nurt.2008.10.030] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The recent therapeutic approach in which drug candidates are designed to possess diverse pharmacological properties and act on multiple targets has stimulated the development of the multimodal drugs, ladostigil (TV3326) [(N-propargyl-(3R) aminoindan-5yl)-ethyl methyl carbamate] and the newly designed multifunctional antioxidant iron chelator, M-30 (5-[N-methyl-N-propargylaminomethyl]-8-hydroxyquinoline). Ladostigil combines, in a single molecule, the neuroprotective/neurorestorative effects of the novel anti-Parkinsonian drug and selective monoamine oxidase (MAO)-B inhibitor, rasagiline (Azilect, Teva Pharmaceutical Co.) with the cholinesterase (ChE) inhibitory activity of rivastigmine. A second derivative of rasagiline, M-30 was developed by amalgamating the propargyl moiety of rasagiline into the skeleton of our novel brain permeable neuroprotective iron chelator, VK-28. Preclinical experiments showed that both compounds have anti-Alzheimer's disease activities and thus, the clinical development is oriented toward treatment of this type of dementia. This review discusses the multimodal effects of two rasagiline-containing hybrid molecules, namely ladostigil and M-30, concerning their neuroprotective molecular mechanisms in vivo and in vitro, including regulation of amyloid precursor protein processing, activation of protein kinase C, and mitogen-activated protein kinase signaling pathways, inhibition of cell death markers and upregulation of neurotrophic factors. Altogether, these scientific findings make these multifunctional compounds potentially valuable drugs for the treatment of Alzheimer's disease.
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Affiliation(s)
- Orly Weinreb
- Eve Topf and USA National Parkinson Foundation Centers of Excellence for Neurodegenerative Diseases Research and Department of Pharmacology, Rappaport Family Research Institute, Technion-Faculty of Medicine, 31096 Haifa, Israel
- grid.6451.60000000121102151Department of Pharmacology, Technion-Faculty of Medicine, P.O.B. 9697, 31096 Haifa, Israel
| | - Silvia Mandel
- Eve Topf and USA National Parkinson Foundation Centers of Excellence for Neurodegenerative Diseases Research and Department of Pharmacology, Rappaport Family Research Institute, Technion-Faculty of Medicine, 31096 Haifa, Israel
- grid.6451.60000000121102151Department of Pharmacology, Technion-Faculty of Medicine, P.O.B. 9697, 31096 Haifa, Israel
| | - Orit Bar-Am
- Eve Topf and USA National Parkinson Foundation Centers of Excellence for Neurodegenerative Diseases Research and Department of Pharmacology, Rappaport Family Research Institute, Technion-Faculty of Medicine, 31096 Haifa, Israel
- grid.6451.60000000121102151Department of Pharmacology, Technion-Faculty of Medicine, P.O.B. 9697, 31096 Haifa, Israel
| | - Merav Yogev-Falach
- Eve Topf and USA National Parkinson Foundation Centers of Excellence for Neurodegenerative Diseases Research and Department of Pharmacology, Rappaport Family Research Institute, Technion-Faculty of Medicine, 31096 Haifa, Israel
- grid.6451.60000000121102151Department of Pharmacology, Technion-Faculty of Medicine, P.O.B. 9697, 31096 Haifa, Israel
| | - Yael Avramovich-Tirosh
- Eve Topf and USA National Parkinson Foundation Centers of Excellence for Neurodegenerative Diseases Research and Department of Pharmacology, Rappaport Family Research Institute, Technion-Faculty of Medicine, 31096 Haifa, Israel
- grid.6451.60000000121102151Department of Pharmacology, Technion-Faculty of Medicine, P.O.B. 9697, 31096 Haifa, Israel
| | - Tamar Amit
- Eve Topf and USA National Parkinson Foundation Centers of Excellence for Neurodegenerative Diseases Research and Department of Pharmacology, Rappaport Family Research Institute, Technion-Faculty of Medicine, 31096 Haifa, Israel
- grid.6451.60000000121102151Department of Pharmacology, Technion-Faculty of Medicine, P.O.B. 9697, 31096 Haifa, Israel
| | - Moussa B. H. Youdim
- Eve Topf and USA National Parkinson Foundation Centers of Excellence for Neurodegenerative Diseases Research and Department of Pharmacology, Rappaport Family Research Institute, Technion-Faculty of Medicine, 31096 Haifa, Israel
- grid.6451.60000000121102151Department of Pharmacology, Technion-Faculty of Medicine, P.O.B. 9697, 31096 Haifa, Israel
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Verma SK, Ganesan TS, Parker PJ. The tumour suppressor RASSF1A is a novel substrate of PKC. FEBS Lett 2008; 582:2270-6. [PMID: 18514071 DOI: 10.1016/j.febslet.2008.05.028] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Accepted: 05/18/2008] [Indexed: 11/15/2022]
Abstract
Ras association domain family 1A (RASSF1A) is a tumour suppressor that contains an amino-terminal cysteine-rich region, similar to the diacylglycerol (DAG)-binding domain (C1 domain) found in the protein kinase C (PKC) family of proteins, and a carboxy-terminal Ras-association (RA) domain. In the present study, RASSF1A was identified as a substrate for PKC. Using classical biochemical approaches, it was established that S197 and S203 within the RA domain of RASSF1A are phosphorylated by PKC in vitro and in vivo. Unlike the WT protein, the S197, 203D double mutant of RASSF1A failed to modulate microtubule organization and perinuclear vimentin collapse. By contrast, the equivalent AA mutant of RASSF1A phenocopied the WT protein. These findings indicate that PKC phosphorylation of RASSF1A regulates its ability to reorganize the microtubule network.
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Affiliation(s)
- Sunil K Verma
- Department of Medical Oncology, Medical Sciences Division, The University of Oxford, Oxford, UK
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17
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Huang PR, Tsai ST, Hsieh KH, Wang TCV. Heterogeneous nuclear ribonucleoprotein A3 binds single-stranded telomeric DNA and inhibits telomerase extension in vitro. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2008; 1783:193-202. [DOI: 10.1016/j.bbamcr.2007.08.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2007] [Revised: 07/13/2007] [Accepted: 08/16/2007] [Indexed: 01/25/2023]
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18
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19
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Jones E, Adcock IM, Ahmed BY, Punchard NA. Modulation of LPS stimulated NF-kappaB mediated Nitric Oxide production by PKCepsilon and JAK2 in RAW macrophages. J Inflamm (Lond) 2007; 4:23. [PMID: 18036230 PMCID: PMC2211292 DOI: 10.1186/1476-9255-4-23] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2007] [Accepted: 11/24/2007] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND Nuclear factor kappa B (NF-kappaB) has been shown to play an important role in regulating the expression of many genes involved in cell survival, immunity and in the inflammatory processes. NF-kappaB activation upregulates inducible nitric oxide synthase leading to enhanced nitric oxide production during an inflammatory response. NF-kappaB activation is regulated by distinct kinase pathways independent of inhibitor of kappaB kinase (IKK). Here, we examine the role of protein kinase C isoforms and janus activated kinase 2 (JAK2) activation in NF-kappaB activation and LPS-stimulated NO production. METHODS Murine RAW 264.7 macrophages were treated with lipopolysaccharide (LPS), Phorbol 12-myristate 13-acetate (PMA) and a combination of LPS and PMA in the presence or absence of various inhibitors of PKC isoforms and JAK2. Nuclear translocation of the NF-kappaB p65 subunit, was assessed by Western blot analysis whilst NO levels were assessed by Greiss assay. RESULTS LPS-stimulated NO production was attenuated by PMA whilst PMA alone did not affect NO release. These effects were associated with changes in p65 nuclear translocation. The PKCalpha, beta, gamma, delta and zeta inhibitor Gö 6983 (Go) had no effect on LPS-induced NO release. In contrast, Bisindolymalemide I (Bis), a PKC alpha, betaI, betaII, gamma, delta and epsilon isoform inhibitors completely inhibited LPS-stimulated NO production without affecting p65 nuclear translocation. Furthermore, a partial inhibitory effect on LPS-induced NO release was seen with the JAK2 inhibitor AG-490 and the p38 MAPK inhibitor SB 203850. CONCLUSION The results further define the role of NF-kappaB in LPS stimulated NO production in RAW macrophages. The data support a function for PKCepsilon, JAK2 and p38 MAPK in NF-kappaB activation following p65 nuclear import.
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Affiliation(s)
- Edward Jones
- Division of Science, University of Luton, Luton. UK
| | - Ian M Adcock
- Airway Diseases, NHLI, Imperial College London, London. UK
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20
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Lee BJ, Lee BH, Wang SG, Lee JC, Roh HJ, Goh EK, Kim CM, Jun ES. Change of the expression of human telomerase reverse transcriptase mRNA and human telomerase RNA after cisplatin and 5-fluorouracil exposure in head and neck squamous cell carcinoma cell lines. J Korean Med Sci 2007; 22 Suppl:S73-8. [PMID: 17923759 PMCID: PMC2694390 DOI: 10.3346/jkms.2007.22.s.s73] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Telomerase activity appears to be associated with cell immortalization and malignant progression. Understanding how telomerase activity is regulated in vivo is important not only for understanding the molecular biology of telomerase but also for the potential clinical application of anticancer drugs. This study evaluated telomerase activity and quantified the expression of human telomerase reverse transcriptase (hTERT) mRNA and human telomerase RNA (hTR) using a real-time reverse transcriptase-polymerase chain reaction (RT-PCR) method before and after the exposure of cisplatin and 5-fluorouracil (5-FU) in two head and neck squamous cell carcinoma (HNSCC) cell lines. Two human HNSCC cell lines (PNUH-12 and SNU-899) were studied. Cell cytotoxicity, the change of telomerase activity, and hTERT mRNA and hTR expression by 5-FU and cisplatin exposure were assessed by MTT assay, TRAP assay, and real-time RT-PCR, respectively. In two cell lines, after cisplatin exposure, the telomerase activity and hTERT mRNA expression decreased, but hTR expression in- creased according to the concentration of drug. However, in both cell lines, the telomerase activity and hTR did not show any significant change after 5-FU treatment, but the expression of hTERT mRNA decreased. These results suggest that there may be other important regulating mechanism except hTERT mRNA as the regulation factor of telomerase activity in HNSCC cell lines.
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Affiliation(s)
- Byung-Joo Lee
- Department of Otolaryngology, College of Medicine, Pusan National University, and Medical Research Institute, Pusan National University, Busan, Korea
| | - Bae-Hyuk Lee
- Department of Otolaryngology, College of Medicine, Pusan National University, and Medical Research Institute, Pusan National University, Busan, Korea
| | - Soo-Geun Wang
- Department of Otolaryngology, College of Medicine, Pusan National University, and Medical Research Institute, Pusan National University, Busan, Korea
| | - Jin-Choon Lee
- Department of Otolaryngology, College of Medicine, Pusan National University, and Medical Research Institute, Pusan National University, Busan, Korea
| | - Hwan-Jung Roh
- Department of Otolaryngology, College of Medicine, Pusan National University, and Medical Research Institute, Pusan National University, Busan, Korea
| | - Eui-Kyung Goh
- Department of Otolaryngology, College of Medicine, Pusan National University, and Medical Research Institute, Pusan National University, Busan, Korea
| | - Cheol-Min Kim
- Department of Biochemistry, College of Medicine, Pusan National University, and Medical Research Institute, Pusan National University, Busan, Korea
| | - Eun-Sook Jun
- Medical Research Institute, Pusan National University Hospital, Busan, Korea
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Bar-Am O, Amit T, Youdim MBH. Aminoindan and hydroxyaminoindan, metabolites of rasagiline and ladostigil, respectively, exert neuroprotective properties in vitro. J Neurochem 2007; 103:500-8. [PMID: 17635668 DOI: 10.1111/j.1471-4159.2007.04777.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The anti-Parkinson, selective irreversible monoamine oxidase B inhibitor drug, rasagiline (Azilect), recently approved by the US Food and Drug Administration, has been shown to possess neuroprotective-neurorescue activities in in vitro and in vivo models. Recent preliminary studies indicated the potential neuroprotective effect of the major metabolite of rasagiline, 1-(R)-aminoindan. In the current study, the neuroprotective properties of 1-(R)-aminoindan were assessed employing a cytotoxic model of human neuroblastoma SK-N-SH cells in high-density culture-induced neuronal death. We show that aminoindan (0.1-1 mumol/L) significantly reduced the apoptosis-associated phosphorylated protein, H2A.X (Ser139), decreased the cleavage of caspase 9 and caspase 3, while increasing the anti-apoptotic proteins, Bcl-2 and Bcl-xl. Protein kinase C (PKC) inhibitor, GF109203X, prevented the neuroprotection, indicating the involvement of PKC in aminoindan-induced cell survival. Aminoindan markedly elevated pPKC(pan) and specifically that of the pro-survival PKC isoform, PKCepsilon. Additionally, hydroxyaminoindan, a metabolite of a novel bifunctional drug, ladostigil [(N-propargyl-(3R) aminoindan-5yl)-ethyl methyl carbamate], combining cholinesterase and monoamine oxidase inhibitor activity, exerted similar neuroprotective properties. Aminoindan and hydroxyaminoindan also protected rat pheochromacytoma PC-12 cells against the neurotoxin, 6-hydroxydopamine. Our findings suggest that both metabolites may contribute to the overall neuroprotective activity of their respective parent compounds, further implicating rasagiline and ladostigil as potentially valuable drugs for treatment of a wide variety of neurodegenerative disorders of aging.
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Affiliation(s)
- Orit Bar-Am
- Eve Topf and USA National Parkinson Foundation Centers of Excellence for Neurodegenerative Diseases Research and Department of Pharmacology, Rappaport Family Research Institute, Technion-Faculty of Medicine, Haifa, Israel
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22
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Galdiero M, Vitiello M, D'Isanto M, Raieta K, Galdiero E. STAT1 and STAT3 phosphorylation by porins are independent of JAKs but are dependent on MAPK pathway and plays a role in U937 cells production of interleukin-6. Cytokine 2007; 36:218-28. [PMID: 17258468 DOI: 10.1016/j.cyto.2006.12.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2006] [Revised: 11/28/2006] [Accepted: 12/16/2006] [Indexed: 10/23/2022]
Abstract
A group of transcription factors, termed signal transducers and activators of transcription (STATs), appears to orchestrate the downstream events propagated by cytokine/growth factor interactions with their cognate receptors. Similarly, cytoplasmic Janus kinases (JAKs) seem to play a critical role in diverse signal transduction pathways that govern cellular survival, proliferation, differentiation and apoptosis. In this work, we analysed the effects of the Salmonella enterica serovar Typhimurium porins on signaling by the JAK/STAT pathway and IL-6 release in U937 cells. Porins and LPS of membrane from Gram-negative bacteria are factors implicated in septic shock. In our assays porins induce interleukin-6 (IL-6) release (110+/-2.6pg/ml) 24h after stimulation and STAT1/STAT3 tyrosine (Tyr701/Tyr705) and serine (Ser727) phosphorylation after 15min. By using several selective inhibitors we demonstrate that porins modulate the activation of STAT1/STAT3 through mitogen activated protein kinases (MAPKs) and not JAKs. Furthermore, we demonstrated that STAT1 and STAT3 are not involved in the modulation of IL-6 release in U937 cells stimulated with porins. Inhibition of tyrosine/serine phosphorylation mediated by MAPKs of STAT1 and STAT3 decrease the IL-6 secretion following porin stimulation. Therefore, suggesting a key role of this pathway in phosphorylation of Ser 727 in STAT1 and STAT3. These results are confirmed by porin or LPS-induced nuclear translocation of STAT1 and STAT3 in U937 cells.
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Affiliation(s)
- Marilena Galdiero
- Department of Experimental Medicine, Section of Microbiology and Clinical Microbiology, Faculty of Medicine, Second University of Naples, Naples, Italy
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23
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Ghosh U, Das N, Bhattacharyya NP. Inhibition of telomerase activity by reduction of poly(ADP-ribosyl)ation of TERT and TEP1/TP1 expression in HeLa cells with knocked down poly(ADP-ribose) polymerase-1 (PARP-1) gene. Mutat Res 2006; 615:66-74. [PMID: 17141279 DOI: 10.1016/j.mrfmmm.2006.10.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2006] [Revised: 10/07/2006] [Accepted: 10/19/2006] [Indexed: 10/23/2022]
Abstract
Inhibitors of poly(ADP-ribose) polymerase (PARP) have been shown to reduce the telomerase activity in cultured cells. To find out the specific member of the PARP family, which participates in the regulation of telomerase activity, in the present investigation, we knocked down the PARP-1 gene by siRNA in HeLa cells and studied the telomerase activity. Reduction of expression of PARP-1 by siRNA increased cellular NAD(+) level and decreased general poly(ADP-ribosyl)ation of proteins. Telomerase activity decreased in cells with knocked down PARP-1 gene. Besides, we observed that telomerase reverse transcriptase (hTERT) was poly(ADP-ribosyl)ated in HeLa cells and such modification was decreased in cells with reduced PARP-1 expression. In addition, the expression of telomerase-associated protein 1 (TEP1/TP1) subunit of human telomerase holoenzyme reduced significantly in PARP-1 knock down HeLa cells. Thus, PARP-1 modulates the telomerase activity by altering poly(ADP-ribosyl)ation of TERT and/or the expression of TEP1/TP1.
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Affiliation(s)
- Utpal Ghosh
- Department of Biochemistry & Biophysics, University of Kalyani, Kalyani, Nadia 741235, India
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Chen YJ, Sheng WY, Huang PR, Wang TCV. Potent inhibition of human telomerase by U-73122. J Biomed Sci 2006; 13:667-74. [PMID: 16850179 DOI: 10.1007/s11373-006-9100-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2006] [Accepted: 06/14/2006] [Indexed: 02/02/2023] Open
Abstract
Telomerase activity is repressed in normal human somatic cells, but is activated in most cancers, suggesting that telomerase may be an important target for cancer therapy. In this study, we report that U-73122, an amphiphilic alkylating agent that is commonly used as an inhibitor for phospholipase C, is also a potent and selective inhibitor of human telomerase. The inhibition of telomerase by U-73122 was attributed primarily to the pyrrole-2,5-dione group, since its structural analog U-73343 did not inhibit telomerase. In confirmation, we observed that telomerase was inhibited by N-ethylmaleimide, but not N-ethylsuccinimide. The IC(50) value of U-73122 for the in vitro inhibition of telomerase activity is 0.2 microM, which is comparable to or slightly more sensitive than that for phospholipase C. The inhibitory action of U-73122 on telomerase appears to be rather selective since the presence of externally added proteins did not protect the inhibition and the IC(50) values for the other enzymes tested in this study were at least an order of magnitude higher than that for telomerase. Furthermore, we demonstrate that U-73122 can inhibit telomerase in hematopoietic cancer cells. The potent and selective inhibition of telomerase by U-73122 raises the potential exploitation of this drug and other alkylating agents as telomerase inhibitor.
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Affiliation(s)
- Yi-Jui Chen
- Department of Molecular and Cellular Biology, Chang Gung University, Kwei-San, Tao-Yuan, 333, Taiwan
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25
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Jeyapalan JC, Saretzki G, Leake A, Tilby MJ, von Zglinicki T. Tumour-cell apoptosis after cisplatin treatment is not telomere dependent. Int J Cancer 2006; 118:2727-34. [PMID: 16381006 DOI: 10.1002/ijc.21675] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Cisplatin is a major chemotherapeutic agent, especially for the treatment of neuroblastoma. Telomeres with their sequence (TTAGGG)n are probable targets for cisplatin intrastrand cross-linking, but the role of telomeres in mediating cisplatin cytotoxicity is not clear. After exposure to cisplatin as single dose or continuous treatment, we found no loss of telomeres in either SHSY5Y neuroblastoma cells (telomere length, approximately 4 kbp), HeLa 229 cells (telomere length, 20 kbp) or in the acute lymphoblastic T cell line 1301 (telomere length, approximately 80 kbp). There was no induction of telomeric single strand breaks, telomeric overhangs were not degraded and telomerase activity was down-regulated only after massive onset of apoptosis. In contrast, cisplatin induced a delayed formation of DNA strand breaks and induced DNA damage foci containing gamma-H2A.X at nontelomeric sites. Interstitial DNA damage appears to be more important than telomere loss or telomeric damage as inducer of the signal pathway towards apoptosis and/or growth arrest in cisplatin-treated tumour cells.
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Affiliation(s)
- Jessie C Jeyapalan
- Henry Wellcome Biogerontology Laboratory, University of Newcastle upon Tyne, Newcastle upon Tyne, United Kingdom
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26
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Chang JT, Lu YC, Chen YJ, Tseng CP, Chen YL, Fang CW, Cheng AJ. hTERT phosphorylation by PKC is essential for telomerase holoprotein integrity and enzyme activity in head neck cancer cells. Br J Cancer 2006; 94:870-8. [PMID: 16508638 PMCID: PMC2361368 DOI: 10.1038/sj.bjc.6603008] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Telomerase activity is suppressed in normal somatic tissues but is activated in most cancer cells. We have previously found that all six telomerase subunit proteins, including hTERT and hsp90 are needed for full enzyme activity. Telomerase activity has been reported to be upregulated by protein kinase C (PKC), but the mechanism is not clear. In this study, we examined how PKC regulates telomerase activity in head and neck cancer cells. PKC inhibitor, bisindolylmaleimide I (BIS), inhibited telomerase activity but had no effect on the expressions of telomerase core subunits. RNA interference (RNAi) and in vitro phosphorylation studies revealed that PKC isoforms α, β, δ, ε, ζ specifically involved in telomerase regulation, and the phosphorylation target was on hTERT. Treatment with the hsp-90 inhibitor novobiocin dissociated hsp90 and hTERT as revealed by immunoprecipitation and immunoblot analysis and reduced telomerase activity. Treatment with the PKC activator SC-10 restored the association of hsp90 and hTERT and reactivate telomerase, suggesting that hTERT phosphorylation by PKC is essential for telomerase holoenzyme integrity and function. Analysis on clinical normal and tumour tissues reveal that the expressions of PKC α, β, δ, ε, ζ were higher in the tumour tissues, correlated with telomerase activity. Disruption of PKC phosphorylation by BIS significantly increased chemosensitivity to cisplatin. In conclusion, PKC isoenzymes α, β, δ, ε, ζ regulate telomerase activity in head and neck cancer cells by phosphorylating hTERT. This phosphorylation is essential for telomerase holoenzyme assembly, leading to telomerase activation and oncogenesis. Manipulation of telomerase activity by PKC inhibitors is worth exploring as an adjuvant therapeutic approach.
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Affiliation(s)
- J T Chang
- Department of Radiation Oncology, Chang Gung Memorial Hospital, Taoyuan 333, Taiwan
| | - Y-C Lu
- Graduate Institute of Medical Biotechnology, Chang Gung University, 259 Wen-Hwa 1st Road, Taoyuan 333, Taiwan
| | - Y-J Chen
- Graduate Institute of Medical Biotechnology, Chang Gung University, 259 Wen-Hwa 1st Road, Taoyuan 333, Taiwan
| | - C-P Tseng
- Graduate Institute of Medical Biotechnology, Chang Gung University, 259 Wen-Hwa 1st Road, Taoyuan 333, Taiwan
| | - Y-L Chen
- Graduate Institute of Medical Biotechnology, Chang Gung University, 259 Wen-Hwa 1st Road, Taoyuan 333, Taiwan
| | - C-W Fang
- Graduate Institute of Medical Biotechnology, Chang Gung University, 259 Wen-Hwa 1st Road, Taoyuan 333, Taiwan
| | - A-J Cheng
- Graduate Institute of Medical Biotechnology, Chang Gung University, 259 Wen-Hwa 1st Road, Taoyuan 333, Taiwan
- Graduate Institute of Medical Biotechnology, Chang Gung University, 259 Wen-Hwa 1st Road, Taoyuan 333, Taiwan. E-mail:
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Mizuno H, Wu J, Kanamori H, Fujisawa M, Namiki N, Saji S, Katagiri S, Katayose Y, Sasaki T, Matsumoto T. Sequencing and characterization of telomere and subtelomere regions on rice chromosomes 1S, 2S, 2L, 6L, 7S, 7L and 8S. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2006; 46:206-17. [PMID: 16623884 DOI: 10.1111/j.1365-313x.2006.02684.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Telomeres, which are important for chromosome maintenance, are composed of long, repetitive DNA sequences associated with a variety of telomere-binding proteins. We characterized the organization and structure of rice telomeres and adjacent subtelomere regions on the basis of cytogenetic and sequence analyses. The length of the rice telomeres ranged from 5.1 to 10.8 kb, as revealed by both fibre-fluorescent in situ hybridization and terminal restriction-fragment assay. Physical maps of the chromosomal ends were constructed from a fosmid library. This facilitated sequencing of the telomere regions of chromosomes 1S, 2S, 2L, 6L, 7S, 7L and 8S. The resulting sequences contained conserved TTTAGGG telomere repeats, which indicates that the physical maps partly covered the telomere regions of the respective chromosome arms. These repeats were organized in the order of 5'-TTTAGGG-3' from the chromosome-specific region, except in chromosome 7S, in which seven inverted copies also existed in tandem array. Analysis of the telomere-flanking regions revealed the occurrence of deletions, insertions, or chromosome-specific substitutions of single nucleotides within the repeat sequences at the junction between the telomere and subtelomere. The sequences of the 500-kb regions of the seven chromosome ends were analysed in detail. A total of 598 genes were predicted in the telomeric regions. In addition, repetitive sequences derived from various kinds of retrotransposon were identified. No significant evidence for segmental duplication could be detected within or among the subtelomere regions. These results indicate that the rice chromosome ends are heterogeneous in both sequence and characterization.
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Affiliation(s)
- Hiroshi Mizuno
- National Institute of Agrobiological Sciences, 1-2, Kannondai 2-chome, Tsukuba, Ibaraki 305-8602, Japan
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Chu WK, Lee KC, Chow SE, Chen JK. Dual regulation of the ΔNp63 transcriptional activity by ΔNp63 in human nasopharyngeal carcinoma cell. Biochem Biophys Res Commun 2006; 342:1356-60. [PMID: 16516862 DOI: 10.1016/j.bbrc.2006.02.111] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2006] [Accepted: 02/20/2006] [Indexed: 10/25/2022]
Abstract
p63 splicing variants lacking NH(2)-terminal transactivating domain, known as DeltaNp63, are thought to antagonize p53 and p63 functions and are suggested to play roles in keratinocyte differentiation. Here, we show that DeltaNp63 has a dual-regulatory effect on the activity of its own promoter in NPC-076 cell. Down-regulation of the transcriptional activity is observed when DeltaNp63 is present in low levels. In contrast, up-regulation of DeltaNp63 transcriptional activity is observed when DeltaNp63 is expressed at higher levels. The down-regulation effect is abolished when the p53-binding site of the DeltaNp63 promoter is mutated. In sharp contrast, similar mutation does not affect the up-regulation of the DeltaNp63 transcriptional activity under the same experimental conditions. Further study shows that the up-regulation is correlated with the activation of the STAT3, as the blockade of STAT3 nuclear translocation abolishes the up-regulation by DeltaNp63. Thus, DeltaNp63 exerts a bidirectional regulation of the DeltaNp63 transcriptional activity in NPC-076 cell.
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Affiliation(s)
- Wing-Keung Chu
- Department of Physiology, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan
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Olaussen KA, Dubrana K, Domont J, Spano JP, Sabatier L, Soria JC. Telomeres and telomerase as targets for anticancer drug development. Crit Rev Oncol Hematol 2006; 57:191-214. [PMID: 16469501 DOI: 10.1016/j.critrevonc.2005.08.007] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2005] [Revised: 08/10/2005] [Accepted: 08/11/2005] [Indexed: 12/15/2022] Open
Abstract
In most human cancers, the telomere erosion problem has been bypassed through the activation of a telomere maintenance system (usually activation of telomerase). Therefore, telomere and telomerase are attractive targets for anti-cancer therapeutic interventions. Here, we review a large panel of strategies that have been explored to date, from small inhibitors of the catalytic sub-unit of telomerase to anti-telomerase immunotherapy and gene therapy. The many positive results that are reported from anti-telomere/telomerase assays suggest a prudent optimism for a possible clinical application in a close future. However, we discuss some of the main limits for these approaches of antitumour drug development and why significant work remains before a clinically useful drug can be proposed to patients.
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Affiliation(s)
- Ken André Olaussen
- Laboratory of Radiobiology and Oncology, DSV/DRR/LRO, CEA, Fontenay aux Roses, France
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Weinreb O, Amit T, Bar-Am O, Sagi Y, Mandel S, Youdim MBH. Involvement of multiple survival signal transduction pathways in the neuroprotective, neurorescue and APP processing activity of rasagiline and its propargyl moiety. JOURNAL OF NEURAL TRANSMISSION. SUPPLEMENTUM 2006:457-65. [PMID: 17017568 DOI: 10.1007/978-3-211-45295-0_69] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Our recent studies aimed to elucidate the molecular and biochemical mechanism of actions of the novel anti-Parkinson's drug, rasagiline, an irreversible and selective monoamine oxidase (MAO)-B inhibitor and its propargyl moiety, propargylamine. In cell death models induced by serum withdrawal in rat PC12 cells and human SH-SY5Y neuroblastoma cells, both rasagiline and propargylamine exerted neuroprotective and neurorescue activities via multiple survival pathways, including: stimulation of protein kinase C (PKC) phosphorylation; up-regulation of protein and gene levels of PKCalpha, PKCepsilon and the anti-apoptotic Bcl-2, Bcl-xL, and Bcl-w; and up-regulation of the neurotrophic factors, BDNF and GDNF mRNAs. Rasagiline and propargylamine inhibited the cleavage and subsequent activation of pro-caspase-3 and poly ADP-ribose polymerase. Additionally, these compounds significantly down-regulated PKCgamma mRNA and decreased the level of the pro-apoptotic proteins, Bax, Bad, Bim and H2A.X. Rasagiline and propargylamine both regulated amyloid precursor protein (APP) processing towards the non-amyloidogenic pathway. These structure-activity studies have provided evidence that propargylamine promoted neuronal survival via neuroprotective/neurorescue pathways similar to that of rasagiline. In addition, recent study demonstrated that chronic low doses of rasagiline administered to mice subsequently to 1 methyl-4 phenyl 1,2,3,6 tetrahydropyridine (MPTP), rescued dopaminergic neurons in the substantia nigra pars compacta via activation of the Ras-PI3K-Akt survival pathway, suggesting that rasagiline may possess a disease modifying activity.
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Affiliation(s)
- O Weinreb
- Eve Topf and USA National Parkinson Foundation Centers of Excellence for Neurodegenerative Diseases Research, Department of Pharmacology, Rappaport Family Research Institute, Technion-Faculty of Medicine, Haifa, Israel.
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31
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Huang PR, Yeh YM, Wang TCV. Potent inhibition of human telomerase by helenalin. Cancer Lett 2005; 227:169-74. [PMID: 16112419 DOI: 10.1016/j.canlet.2004.11.045] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2004] [Revised: 11/25/2004] [Accepted: 11/28/2004] [Indexed: 11/18/2022]
Abstract
Telomerase activity is repressed in normal human somatic cells, but is activated in most cancers, suggesting that telomerase may be an important target for cancer therapy. Inhibition of telomerase in cancer cells has been shown to limit the growth of human cancer cells in culture. In this study, we report that helenalin, a natural sesquiterpene lactone, is a potent and selective inhibitor for human telomerase. In vitro studies indicate that this drug can inactivate telomerase directly in a manner that is dependent on concentration and time. The inhibitory action of this drug on telomerase is selective since the presence of excessive externally added proteins did not protect the inhibition and all of the other enzymes tested in this study were not inhibited by this drug. Furthermore, we demonstrated that helenalin can inhibit the expression of hTERT and telomerase in hematopoietic cancer cells. Therefore, the anti-tumor activity of helenalin is attributed, at least in part, to the inhibition of telomerase.
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Affiliation(s)
- Pei-Rong Huang
- Department of Molecular and Cellular Biology, Chang Gung University, Kwei-San, Tao-Yuan 333, Taiwan, ROC
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Jackson EK, Gao L, Zhu C. Mechanism of the Vascular Angiotensin II/α2-Adrenoceptor Interaction. J Pharmacol Exp Ther 2005; 314:1109-16. [PMID: 15901799 DOI: 10.1124/jpet.105.086074] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
alpha(2)-Adrenoceptors potentiate vascular responses to angiotensin II. The goal of this study was to test the hypothesis that the phospholipase C (PLC)/protein kinase C (PKC)/c-src/phosphatidylinositol 3-kinase (PI3K) pathway contributes to the vascular angiotensin II/alpha(2)-adrenoceptor interaction. In rats in vivo, intrarenal infusions of angiotensin II (10 ng/kg/min) increased renal vascular resistance by 5.8 +/- 0.5 units, and this response was enhanced (p < 0.05) to 9.1 +/- 1.2 units by UK-14,304 [5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine; 3 microg/kg/min; alpha(2)-adrenoceptor agonist]. Intrarenal infusions of U-73122 [1-[6-[[(17beta)-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]-hexyl]-1H-pyrrole-2,5-dione; 3 microg/min; PLC inhibitor], GF109203X [bisindolylmaleimide I; 10 microg/min; PKC inhibitor], CGP77675 [1-(2-{4-[4-amino-5-(3-methoxyphenyl)pyrrolo[2,3-d]pyrimidin-7-yl]phenyl}ethyl)piperidin-4-ol; 5 microg/min; c-src inhibitor], and wortmannin (1 microg/min; PI3K inhibitor) abolished the angiotensin II/alpha(2)-adrenoceptor interaction. In isolated perfused rat kidneys, angiotensin II (0.3, 1, and 3 nM) increased perfusion pressure (by 15 +/- 8, 39 +/- 4, and 93 +/- 9 mm Hg, respectively), and UK-14,304 (1 microM) potentiated these responses (to 36 +/- 4, 67 +/- 7, and 135 +/- 17 mm Hg, respectively). This angiotensin II/alpha(2)-adrenoceptor interaction was abolished by U-73122 (10 microM), GF109203X (3 microM), CGP77675 (5 microM), and wortmannin (0.2 microM). Preglomerular microvascular smooth muscle cells expressed phospholipase (PLC)-beta(2), PLC-beta(3), c-src, phospho(tyrosine 416)-c-src, and PI3K. In these cells, angiotensin II (0.1 microM) and UK-14,304 (1 microM) per se did not increase phospho-c-src; however, the combination of angiotensin II plus UK-14,304 doubled phospho-c-src, and this interaction was abolished by U-73122 (10 microM) and GF109203X (3 microM). In conclusion, the PLC/PKC/c-src/PI3K pathway may contribute importantly to the interaction between alpha(2)-adrenoceptors and angiotensin II on renal vascular resistance.
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Affiliation(s)
- Edwin K Jackson
- Center for Clinical Pharmacology, Department of Pharmacology, University of Pittsburgh School of Medicine, PA 15219-3130, USA.
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Abstract
Telomerase is a ribonucleoprotein that directs the synthesis of telomeric sequence. It is detected in majority of malignant tumors, but not in most normal somatic cells. Because telomerase plays a critical role in cell immortality and tumor formation, it has been one of the targets for anti-cancer and regeneration drug development. In this review, we will discuss therapeutic approaches based mainly on small molecules that have been developed to inhibit telomerase activity, modulate telomerase expression, and telomerase directed gene therapy.
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Affiliation(s)
- Yi-hsin Hsu
- Institute of Biopharmaceutical Science, National Yang-Ming University, Taipei, Taiwan, China
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Yeh YM, Pan YT, Wang TCV. Cdc42/Rac1 participates in the control of telomerase activity in human nasopharyngeal cancer cells. Cancer Lett 2005; 218:207-13. [PMID: 15670898 DOI: 10.1016/j.canlet.2004.06.047] [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] [Received: 04/22/2004] [Revised: 06/29/2004] [Accepted: 06/30/2004] [Indexed: 01/20/2023]
Abstract
Telomerase, a specialized ribonucleoprotein reverse transcriptase that directs the synthesis of telomeric DNA, is repressed in normal human somatic cells, but is activated in most cancers. Little is known concerning how telomerase activity is activated and maintained in cancer cells. We have previously shown that protein kinase C-zeta (PKC zeta) controls telomerase activity in nasopharyngeal cancer (NPC) cells. Since PKC zeta activity is known to be modulated by Cdc42/Rac1, we investigated the effects of inhibiting Cdc42 and Rac1 on the telomerase activity of NPC-076 cells. Treatment of NPC cells with antisense oligonucleotides against Cdc42 or Rac1 produced an inhibition of telomerase activity. Similarly, transient expression of dominant-negative mutants of Cdc42 or Rac1, but not the wild-type Cdc42 or Rac1, also produced an inhibition of telomerase activity in NPC cells. This inhibition of telomerase activity is not associated with a transcriptional down-regulation of hTERT, the key regulator of telomerase. We suggest that Cdc42/Rac1 participates in the posttranscriptional control of telomerase activity in NPC cells.
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Affiliation(s)
- Yuan-Ming Yeh
- Department of Molecular and Cellular Biology, Chang Gung University, Kwei-San, Tao-Yuan 333, Taiwan, ROC
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Renault MA, Jalvy S, Potier M, Belloc I, Genot E, Dekker LV, Desgranges C, Gadeau AP. UTP induces osteopontin expression through a coordinate action of NFkappaB, activator protein-1, and upstream stimulatory factor in arterial smooth muscle cells. J Biol Chem 2004; 280:2708-13. [PMID: 15557322 DOI: 10.1074/jbc.m411786200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Osteopontin (OPN) is an important chemokinetic agent for several cell types. Our earlier studies have shown that its expression is essential for uridine triphosphate (UTP)-mediated migration of vascular smooth muscle cells. We demonstrated previously that the activation of an AP-1 binding site located 76 bp upstream of the transcription start in the rat OPN promoter is involved in the induction of OPN expression. In this work, using a luciferase promoter deletion assay, we identified a new region of the rat OPN promoter (-1837 to -1757) that is responsive to UTP. This region contains an NFkappaB site located at -1800 and an Ebox located at -1768. Supershift electrophoretic mobility shift assay and chromatin immunoprecipitation assays identified NFkappaB and USF-1/USF-2 as the DNA binding proteins induced by UTP, respectively, for these two sites. Using dominant negative mutants of IkappaB kinase and USF transcription factors, we confirmed that NFkappaB and USF-1/USF-2 are involved in the UTP-mediated expression of OPN. Using a pharmacological approach, we demonstrated that USF proteins are regulated by the extracellular signal-regulated kinase (ERK)1/2 pathway, just as the earlier discovered AP-1 complex, whereas NFkappaB is up-regulated through PKCdelta signals. Finally, our work suggests that the UTP-stimulated OPN expression involves a coordinate regulation of PKCdelta-NFkappaB, ERK1/2-USF, and ERK1/2/NAD(P)H oxidase AP-1 signaling pathways.
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Liu WJ, Zhang YW, Shen Y, Jiang JF, Miao ZH, Ding J. Telomerase inhibition is a specific early event in salvicine-treated human lung adenocarcinoma A549 cells. Biochem Biophys Res Commun 2004; 323:660-7. [PMID: 15369801 DOI: 10.1016/j.bbrc.2004.08.135] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2004] [Indexed: 11/20/2022]
Abstract
The telomere and telomerase have been suggested as targets for anticancer drug discovery. However, the mechanisms by which conventional anticancer drugs affect these targets are currently unclear. The novel topoisomerase II inhibitor, salvicine, suppresses telomerase activity in leukemia HL-60 cells. To further determine whether this activity of salvicine is specific to the hematological tumor and distinct from those of other conventional anticancer agents, we studied its effects on telomere and telomerase in a solid lung carcinoma cell line, A549. Differences in telomerase inhibition and telomere erosion were observed between salvcine and other anticancer agents. All anticancer agents (except adriamycin) induced shortening of the telomere, which was identified independent of replication, but only salvicine inhibited telomerase activity in A549 cells under conditions of high concentration and short-term exposure. At the low concentration and long-term exposure mode, all the tested anticancer agents shortened the telomere and inhibited telomerase activity in the same cell line. Notably, salvicine inhibited telomerase activity more severely than the other agents examined. Moreover, the compound inhibited telomerase activity in A549 cells indirectly in a concentration- and time-dependent manner. Salvicine did not affect the expression of hTERT, hTP1, and hTR mRNA in A549 cells following 4 h of exposure. Okadaic acid protected telomerase from inhibition by salvicine. These results indicate specificity of salvicine and diversity of anticancer agents in the mechanism of interference with telomerase and the telomere system. Our data should be helpful for designing the study in the development of agents acting on telomere and/or telomerase.
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Affiliation(s)
- Wei-Jun Liu
- Division of Anti-tumor Pharmacology, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 201203, China
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Spiropoulou T, Ferekidou L, Angelopoulou K, Stathopoulou A, Talieri M, Lianidou ES. Effect of antineoplastic agents on the expression of human telomerase reverse transcriptase beta plus transcript in MCF-7 cells. Clin Biochem 2004; 37:299-304. [PMID: 15003732 DOI: 10.1016/j.clinbiochem.2003.12.008] [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] [Received: 10/08/2003] [Revised: 12/10/2003] [Accepted: 12/11/2003] [Indexed: 02/07/2023]
Abstract
OBJECTIVES To evaluate the effect of antineoplastic agents on the expression of human telomerase reverse transcriptase (hTERT) splice variants in MCF-7 cells. DESIGN AND METHODS We have developed a luminometric hybridization assay for hTERT beta plus transcript. MCF-7 cells were isolated before and after treatment with antineoplastic agents. A combination of nested RT-PCR and the developed luminometric hybridization assay was used for the specific detection of hTERT beta plus transcript in treated and untreated MCF-7 cells. Amplification of all hTERT splicing variants by nested PCR in the same samples was also performed. RESULTS MCF-7 cells treated with taxol and etoposide were found positive for all hTERT splicing variants, while the expression of hTERT beta plus transcript did not differ significantly before and after exposure. MCF-7 cells treated with doxorubicin and 5-fluorouracil did not express any of hTERT splicing variants. In the presence of cisplatin, three splicing variants of hTERT were detected. CONCLUSIONS The developed hybridization assay is highly sensitive and specific for the detection of hTERT beta plus transcript in clinical samples.
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Affiliation(s)
- Tonia Spiropoulou
- Laboratory of Analytical Chemistry, Department of Chemistry, University of Athens, 15771 Athens, Greece
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Weinreb O, Bar-Am O, Amit T, Chillag-Talmor O, Youdim MBH. Neuroprotection via pro‐survival protein kinase C isoforms associated with Bcl‐2 family members. FASEB J 2004; 18:1471-3. [PMID: 15247150 DOI: 10.1096/fj.04-1916fje] [Citation(s) in RCA: 155] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
This study provides new insights into neuroprotection involving interaction of protein kinase C (PKC) pathway with Bcl-2 family proteins. Using a model of serum deprivation, we investigated the mechanism by which the anti-Parkinson/monoamine oxidase (MAO)-B inhibitor drug, rasagiline, exerts its neuroprotective effect in rat pheochromocytoma PC12 cells. Here, we report that rasagiline (0.1-10 microM) decreased apoptosis via multiple protection mechanisms, including the stimulation of PKC phosphorylation; up-regulation of PKCalpha and PKC mRNAs, induction of Bcl-xL, Bcl-w, and brain-derived neurotrophic factor (BDNF) mRNAs; and down-regulation of Bad and Bax mRNAs. Moreover, rasagiline inhibited the cleavage and activation of procaspase-3 and poly (ADP-ribose) polymerase (PARP), whereas the PKC inhibitor, GF109203X, reversed these actions. Similarly, rasagiline decreased serum-free-induced levels of the important regulator of cell death, Bad, which was also blocked by GF109203X, indicating the involvement of PKC in rasagiline-induced cell survival. Furthermore, these studies have established that PKC- and Bcl-2-dependent neuroprotective activity of rasagiline is dependent on its propargyl moiety, because propargylamine had similar effects with the same potency.
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Affiliation(s)
- Orly Weinreb
- Eve Topf and Rappaport Family Research Institute, Technion-Faculty of Medicine, Haifa, Israel
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40
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Nasir L, Gault E, Campbell S, Veeramalai M, Gilbert D, McFarlane R, Munro A, Argyle DJ. Isolation and expression of the reverse transcriptase component of the Canis familiaris telomerase ribonucleoprotein (dogTERT). Gene 2004; 336:105-13. [PMID: 15225880 DOI: 10.1016/j.gene.2004.03.032] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2003] [Revised: 02/28/2004] [Accepted: 03/29/2004] [Indexed: 01/14/2023]
Abstract
The enzyme telomerase plays a crucial role in cellular proliferation and tumorigenesis. Telomerase is an RNA-directed DNA polymerase composed minimally of an RNA subunit (TR) and a catalytic protein component (TERT). The protein component acts as a reverse transcriptase (RT) and catalyses the addition of telomeric repeats onto the ends of chromosomes using the RNA subunit as a template. While both the RNA and catalytic subunits are essential for telomerase activity, the TERT component of telomerase is thought to be the primary determinant for enzyme activity as expression of TERT is largely limited to cells with telomerase activity. We describe here the isolation and sequence characterization of the telomerase catalytic subunit from Canis familiaris (dog), dogTERT. The predicted protein consists of 1123-aa residues and contains all the signature motifs of the TERT family members. Sequence comparisons with previously identified mammalian TERT proteins demonstrate that dogTERT shows the highest level of sequence similarity to the human TERT protein, supporting the dog as a model system for telomerase-based studies. Further, we demonstrate that TERT mRNA expression is associated with telomerase activity in canine-cultured cells, similar to TERT expression in human cells. This data will allow for further investigation of telomerase in canine malignancies as well as the development of the dog as a model system for human telomerase investigations.
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Affiliation(s)
- Lubna Nasir
- Department Veterinary Clinical Studies, Institute of Comparative Medicine, University of Glasgow Veterinary School, Bearsden Road, Glasgow G61 1QH, Scotland, UK.
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Abstract
Adult ventricular myocytes can undergo mitotic division, resulting in an increase in the aggregate number of cells in the heart. The improvement in the methodological approach to the analysis of tissue sections by immunostaining and confocal microscopy has defeated the dogma that myocyte regeneration cannot occur in the adult heart. Most importantly, primitive and progenitor cells have been identified in the human heart. These cells express telomerase and have the capability of undergoing lineage commitment and rapid cell division, expanding significantly the contracting ventricular myocardium. These cell populations possess all the molecular components regulating the entry and progression through the cell cycle, karyokinesis, and cytokinesis. The recognition that myocyte hypertrophy and regeneration, as well as myocyte necrosis and apoptosis, occur in cardiac diseases has contributed to enhancing our understanding of the plasticity of the human heart.
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Affiliation(s)
- Jan Kajstura
- New York Medical College, Valhalla, NY 10595, USA
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Jackson TC, Mi Z, Jackson EK. Modulation of cyclic AMP production by signal transduction pathways in preglomerular microvessels and microvascular smooth muscle cells. J Pharmacol Exp Ther 2004; 310:349-58. [PMID: 15087474 DOI: 10.1124/jpet.103.063081] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cyclic AMP affects microvascular smooth muscle contraction and growth. Therefore, it is important to elucidate mechanisms regulating cyclic AMP production in microvascular smooth muscle. In this study, we determined whether several signal transduction pathways regulate receptor-induced cyclic AMP in isolated preglomerular microvessels and microvascular smooth muscle cells. Preglomerular microvessels were incubated with isoproterenol (beta-adrenoceptor agonist) and with and without U73122 (phospholipase C inhibitor), GF109203X (protein kinase C inhibitor), 1-butanol (phospholipase D inhibitor), CGP77675 (c-src inhibitor), HA1077 (Rho kinase inhibitor), Y27632 (Rho kinase inhibitor), LY294002 (phosphatidylinositol-3-kinase inhibitor), dipenyleneiodonium (NADPH oxidase inhibitor), or Tempol (superoxide dismutase mimetic). Cultured preglomerular microvascular smooth muscle cells were incubated with isoproterenol or forskolin (direct activator of adenylyl cyclase) and with or without U73122, C(2)-ceramide (phospholipase D inhibitor), or PP1 [src family inhibitor, 1-(1,1-dimethylethyl)-1-(4-methylphenyl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine]. All studies were conducted with 3-isobutyl-1-methylxanthine (broad-spectrum phosphodiesterase inhibitor) to eliminate changes in cyclic AMP degradation. In microvessels isoproterenol-induced cyclic AMP was not affected by Y27632, HA1007, LY294002, dipenylene-iodonium, or Tempol; was increased by U73122 and GF109203X; and was decreased by 1-butanol and CGP77675. In cells, U73122 increased and C(2)-ceramide and PP1 decreased isoproterenol-induced cyclic AMP. Forskolin-induced cyclic AMP was not altered. These results indicate that receptor-mediated activation of adenylyl cyclase is 1) not modulated by Rho kinase, phosphatidylinositol-3-kinase, NADPH oxidase, or superoxide; 2) is attenuated by phospholipase C and protein kinase C; and 3) is augmented by phospholipase D and src. Phospholipase C, phospholipase D, and src modulate receptor-induced cyclic AMP by affecting beta-adrenoreceptor/G protein/adenylyl cyclase coupling rather than by directly affecting adenylyl cyclase activity.
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Affiliation(s)
- Travis C Jackson
- Department of Medicine, Center for Clinical Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
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Nakajima K, Tohyama Y, Kohsaka S, Kurihara T. Protein kinase Cα requirement in the activation of p38 mitogen-activated protein kinase, which is linked to the induction of tumor necrosis factor α in lipopolysaccharide-stimulated microglia. Neurochem Int 2004; 44:205-14. [PMID: 14602083 DOI: 10.1016/s0197-0186(03)00163-3] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Activated microglia have been suggested to produce a cytotoxic cytokine, tumor necrosis factor alpha (TNF alpha), in many pathological brains. Thus, determining the molecular mechanism of this induction and suppression has been the focus of a great deal of research. Using lipopolysaccharide (LPS) as an experimental inducer of TNF alpha, we investigated the regulatory mechanism by which TNFalpha is induced or suppressed in microglia. We found that LPS-induced TNF alpha is suppressed by pretreatment with the p38 mitogen-activated protein kinase (p38MAPK) inhibitor SB203580. Similar suppression was achieved by pretreatment with specific protein kinase C (PKC) inhibitors, Gö6976, myristoylated pseudosubstrate (20-28), and bisindolylmaleimide. These results suggest that PKC alpha activity as well as p38MAPK activity is associated with TNF alpha induction in LPS-stimulated microglia. The requirement of PKC alpha in LPS-dependent TNFalpha induction was verified in PKC alpha-downregulated microglia which could be induced by phorbol-12-myristate-13-acetate pretreatment. Simultaneously, PKC alpha was found to be requisite for the activation of p38MAPK in LPS-stimulated microglia. In addition, the PKC alpha levels in the LPS-stimulated microglia were observed to decrease in response to the p38MAPK inhibitor, indicating that the PKC alpha levels are regulated by the p38MAPK activity. We therefore concluded that PKC alpha and p38MAPK are interactively linked to the signaling cascade inducing TNFalpha in LPS-stimulated microglia, and that in this cascade, PKC alpha is requisite for the activation of p38MAPK, leading to the induction of TNF alpha.
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Affiliation(s)
- Kazuyuki Nakajima
- Neurobiology Lab, Department of Bioinformatics, Faculty of Engineering, Soka University, 1-236 Tangi-machi, Hachioji, Tokyo 192-8577, Japan.
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Wang X, Wang Q, Hu W, Evers BM. Regulation of phorbol ester-mediated TRAF1 induction in human colon cancer cells through a PKC/RAF/ERK/NF-κB-dependent pathway. Oncogene 2004; 23:1885-95. [PMID: 14981539 DOI: 10.1038/sj.onc.1207312] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Tumor necrosis factor (TNF) receptor-associated factors (TRAFs) are cytoplasmic adapter proteins that link a wide variety of cell surface receptors to the apoptotic signaling cascade. The purpose of this study was to delineate the signaling pathways and TRAF1 promoter elements responsible for phorbol ester-mediated TRAF1 induction in human colon cancers. Here, we found that the PKC activators, phorbol 12-myristate 13-acetate (PMA) and bryostatin I, induced TRAF1 mRNA expression; pretreatment with actinomycin D blocked PMA-mediated TRAF1 expression suggesting induction at the transcriptional level. In contrast, expression of other TRAFs (TRAF2, 3 and 4) was minimally altered by PMA. Various PKC isoform-selective inhibitors blocked PMA-mediated TRAF1 mRNA and promoter stimulation; rottlerin, a selective PKCdelta inhibitor, had no effect suggesting that Ca(2+)-dependent PKC isoforms (e.g., PKCalpha and betaI) play a role in TRAF1 regulation. In addition, the MEK/ERK inhibitors, PD98059 and UO126, suppressed PMA-stimulated TRAF1 promoter activity indicating a role for ERK in TRAF1 induction. Moreover, cotransfection of a dominant-negative Raf-1 (Raf-C4) significantly reduced PMA-stimulated TRAF1 promoter activity whereas transfection of dominant-negative Ras or treatment with Ras inhibitors had minimal to no effect on TRAF1 induction suggesting dependence on Raf, but not Ras, activation. Finally, site-specific mutagenesis of functional NF-kappaB sites (particularly the most proximal site) in the TRAF1 promoter significantly decreased PMA-mediated promoter activity. In conclusion, our results demonstrate selective induction of TRAF1 in human colon cancer cells through a Ca(2+)-dependent PKC/Raf-1/ERK/NF-kappaB-dependent pathway.
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Affiliation(s)
- Xiaofu Wang
- Department of Surgery and Sealy Center for Cancer Cell Biology, The University of Texas Medical Branch, Galveston, TX 77555, USA
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45
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Cao A, Ramos-Martínez JI, Barcia R. In vitro effects of LPS, IL-2, PDGF and CRF on haemocytes of Mytilus galloprovincialis Lmk. FISH & SHELLFISH IMMUNOLOGY 2004; 16:215-225. [PMID: 15123325 DOI: 10.1016/s1050-4648(03)00080-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2002] [Revised: 05/01/2003] [Accepted: 05/28/2003] [Indexed: 05/24/2023]
Abstract
The cells in charge of the innate immune response in the marine mussel Mytilus galloprovincialis Lmk. are the haemocytes. These cells respond in different ways to agents such as lipopolysaccharide (LPS), interleukin-2 (IL-2), platelet-derived growth factor (PDGF) and corticotropin releasing factor (CRF). After stimulation of the haemocytes, the expression of molecules reactive with monoclonal antibodies raised to the alpha chain of the IL-2 receptor, present in their membrane, differed depending on the agent used. The same happened with regard to the levels of dopamine, adrenaline and noradrenaline released to the medium by the haemocytes. It should also be noted that no catecholamine release was detected and the level of expression of IL-2Ralpha showed no significant variation in cultured cells that had not been treated with inducers. These facts would indicate that most haemocytes were in the same starting condition at the moment that the stimulation was performed. Therefore, cultured haemocytes can be a highly reliable model in the study of the innate immune system.
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Affiliation(s)
- Asunción Cao
- Departamento de Bioquímica y Biología Molecular, Universidad de Santiago de Compostela, Facultad de Veterinaria, Campus de Lugo, E-27002 Lugo, Spain
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Lan C, Das D, Wloskowicz A, Vollrath B. Endothelin-1 modulates hemoglobin-mediated signaling in cerebrovascular smooth muscle via RhoA/Rho kinase and protein kinase C. Am J Physiol Heart Circ Physiol 2004; 286:H165-73. [PMID: 14500131 DOI: 10.1152/ajpheart.00664.2003] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Endothelin-1 (ET-1) and oxyhemoglobin (OxyHb) have been implicated in the pathogenesis of cerebral vasospasm after subarachnoid hemorrhage. However, the contribution of ET-1 to this condition has not been definitely established. In this study, we investigated whether threshold concentration of ET-1 enhances cerebrovascular smooth muscle (CVSM) contraction to OxyHb by activating the RhoA/Rho kinase and protein kinase C (PKC) pathways. CVSM contraction was measured in endothelium-denuded rabbit basilar arteries. Cytosolic and particulate fractions of CVSM cells were examined for RhoA and PKC reactivity with specific antibodies using immunoblotting procedures. ET-1 (0.1 nM) alone did not produce any significant contraction, but it markedly potentiated the magnitude (223% of control) and rate (149% of control) of contraction in response to OxyHb, which was attenuated by the inhibitors of Rho kinase Y-27632 and HA-1077. ET-1-mediated potentiation of the contraction was also inhibited by inhibitors of PKC, Ro-32-0432, and GF-109203X. BQ-123 prevented potentiation of vasoconstriction mediated by ET-1, indicating that the action of ET-1 was mediated by the endothelin type A receptor. Pretreatment with ET-1 significantly enhanced OxyHb-mediated RhoA translocation in CVSM cells and intact basilar arteries. ET-1 also caused potentiation of PKC-ϵ expression in membranes of CVSM cells exposed to OxyHb for 10 and 60 min but did not markedly change the distribution of PKC-α. Thus, in CVSM, threshold concentration of ET-1 potentiates contraction induced by OxyHb via RhoA/Rho kinase- and PKC-ϵ-dependent mechanisms. This process may contribute to the pathological contraction of cerebral arteries observed after subarachnoid hemorrhage.
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Affiliation(s)
- Christopher Lan
- Department of Pharmacology, Faculty of Medicine, 9-70 Medical Sciences Bldg., University of Alberta, Edmonton, Alberta, Canada T6G 2H7
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Rezler EM, Bearss DJ, Hurley LH. Telomere inhibition and telomere disruption as processes for drug targeting. Annu Rev Pharmacol Toxicol 2003; 43:359-79. [PMID: 12540745 DOI: 10.1146/annurev.pharmtox.43.100901.135733] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The components and cofactors of the holoenzyme telomerase and its substrate telomeric DNA are attractive targets for anticancer agents that act by inhibiting the activity of telomerase. This review outlines recent advances in telomerase inhibition that have been achieved using antisense oligonucleotides and ribozymes that target the telomerase mRNA or its hTR RNA template. Although these are potent catalytic inhibitors of telomerase, they are challenging to implement in the clinic due to their delayed effectiveness. Drugs that directly bind to the telomeres, the complex structures that are associated at the telomeric ends, and stabilize secondary DNA structures such as G-quadruplexes are also potent inhibitors of telomerase. Special focus is given here to the telomeres, the biological machinery that works in tandem with telomerase to elongate telomeres, the causes of telomere disruption or dysfunction, and the consequences of disruption/dysfunction on the activity and design of anticancer agents.
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Affiliation(s)
- Evonne M Rezler
- College of Pharmacy, The University of Arizona, Tucson, Arizona 85721, USA.
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Sheng WY, Chien YL, Wang TCV. The dual role of protein kinase C in the regulation of telomerase activity in human lymphocytes. FEBS Lett 2003; 540:91-5. [PMID: 12681489 DOI: 10.1016/s0014-5793(03)00230-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Protein kinase C (PKC) has been implicated to play an essential function in the upregulation of telomerase activity in activated T cells, yet its role in the regulation of telomerase activity remains largely unknown. In this work, we present evidence that PKC activity is required both for the induction of hTERT expression and for the post-transcriptional control of telomerase enzyme activity in T lymphocytes. Of the several PKC isoforms present in lymphocytes, only the level of PKC-zeta was greatly increased during T cell activation, implicating that PKC-zeta may be required for the post-transcriptional control of telomerase enzyme activity in T lymphocytes.
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Affiliation(s)
- Wei-Yun Sheng
- Department of Molecular and Cellular Biology, Chang Gung University, Kwei-San, Tao-Yuan 333, Taiwan
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Trailovic SM, Robertson AP, Clark CL, Martin RJ. Levamisole receptor phosphorylation: effects of kinase antagonists on membrane potential responses in Ascaris suum suggest that CaM kinase and tyrosine kinase regulate sensitivity to levamisole. J Exp Biol 2002; 205:3979-88. [PMID: 12432019 DOI: 10.1242/jeb.205.24.3979] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
A two-micropipette current-clamp technique was used to record electrophysiological responses from the somatic muscle of Ascaris suum. Levamisole and acetylcholine were applied to the bag region of the muscle using a microperfusion system. Depolarizations produced by 10 s applications of 10 μmol l-1 levamisole or 20 s applications of 10 μmol l-1 acetylcholine were recorded. The effect on the peak membrane potential change of the kinase antagonists H-7, staurosporine, KN-93 and genistein was observed. H-7 (30 μmol l-1), a non-selective antagonist of protein kinases A, C and G but which has little effect on Ca2+/calmodulin-dependent kinase II (CaM kinase II), did not produce a significant effect on the peak response to levamisole or acetylcholine. Staurosporine (1 μmol l-1), a non-selective kinase antagonist that has effects on protein kinases A, C and G, CaM kinase and tyrosine kinase, reduced the mean peak membrane potential response to levamisole from 6.8 mV to 3.9 mV (P<0.0001) and the mean response to acetylcholine from 5.5 mV to 2.8 mV (P=0.0016). The difference between the effects of H-7 and staurosporine suggested the involvement of CaM kinase II and/or tyrosine kinase. KN-93, a selective CaM kinase II antagonist,reduced the mean peak response to levamisole from 6.2 mV to 2.7 mV(P=0.035) and the mean peak response of acetylcholine from 4.7 mV to 2.0 mV (P=0.0004). The effects indicated the involvement of CaM kinase II in the phosphorylation of levamisole and acetylcholine receptors. The effect of extracellular Ca2+ on the response to levamisole was assessed by comparing responses to levamisole in normal and in low-Ca2+ bathing solutions. The response to levamisole was greater in the presence of Ca2+, an effect that may be explained by stimulation of CaM kinase II. Genistein (90 μmol l-1), a selective tyrosine kinase antagonist, reduced peak membrane potential responses to levamisole from a mean of 6.4 mV to 3.3 mV (P=0.001). This effect indicated the involvement of tyrosine kinase in maintaining the receptor.
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Affiliation(s)
- Sasa M Trailovic
- Department of Biomedical Sciences, Iowa State University, Ames 50011, USA
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Mwimbi XKMS, Muimo R, Treharne KJ, Sijumbila G, Green M, Mehta A. 4alpha-Phorbol negates the inhibitory effects of phorbol-12-myristate-13-acetate on human cilia and alters the phosphorylation of PKC. FEBS Lett 2002; 530:31-6. [PMID: 12387861 DOI: 10.1016/s0014-5793(02)03358-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
In medium 199, ciliary beat frequency (CBF) in human nasal epithelium declines to 60% of baseline by 2 h and 1 nM phorbol-12-myristate-13-acetate (PMA) doubles the rate of decline by activating protein kinase C (PKC). We find that a reported negative control for PMA, 4alpha-phorbol (1 pM-1 nM)+/-1 nM PMA, not only maintains CBF at baseline, but arrests a pre-existing PMA-induced decline in CBF and alters the profile of multiple phosphorylated PKC species. Thus, 4alpha-phorbol not only potently prevents PMA from inhibiting CBF but also has potent effects on the phosphorylation of PKC.
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Affiliation(s)
- Xowi K M S Mwimbi
- Tayside Institute of Child Health, Ninewells Hospital and Medical School, University of Dundee, UK
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