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Tavares CDJ, Devkota AK, Dalby KN, Cho EJ. Application of Eukaryotic Elongation Factor-2 Kinase (eEF-2K) for Cancer Therapy: Expression, Purification, and High-Throughput Inhibitor Screening. Methods Mol Biol 2016; 1360:19-33. [PMID: 26501899 DOI: 10.1007/978-1-4939-3073-9_2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Protein kinases have emerged as an important class of therapeutic targets, as they are known to be involved in pathological pathways linked to numerous human disorders. Major efforts to discover kinase inhibitors in both academia and pharmaceutical companies have centered on the development of robust assays and cost-effective approaches to isolate them. Drug discovery procedures often start with hit identification for lead development, by screening a library of chemicals using an appropriate assay in a high-throughput manner. Considering limitations unique to each assay technique and screening capability, intelligent integration of various assay schemes and level of throughput, in addition to the choice of chemical libraries, is the key to success of this initial step. Here, we describe the purification of the protein kinase, eEF-2K, and the utilization of three biochemical assays in the course of identifying small molecules that block its enzymatic reaction.
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Affiliation(s)
- Clint D J Tavares
- Division of Medicinal Chemistry, College of Pharmacy, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Ashwini K Devkota
- Texas Screening Alliance for Cancer Therapeutics, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Kevin N Dalby
- Division of Medicinal Chemistry, College of Pharmacy, The University of Texas at Austin, Austin, TX, 78712, USA.
- Texas Screening Alliance for Cancer Therapeutics, The University of Texas at Austin, Austin, TX, 78712, USA.
| | - Eun Jeong Cho
- Texas Screening Alliance for Cancer Therapeutics, The University of Texas at Austin, Austin, TX, 78712, USA.
- College of Pharmacy, The University of Texas at Austin, Austin, TX, 78712, USA.
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2
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Usui T, Nijima R, Sakatsume T, Otani K, Kameshima S, Okada M, Yamawaki H. Eukaryotic elongation factor 2 kinase controls proliferation and migration of vascular smooth muscle cells. Acta Physiol (Oxf) 2015; 213:472-80. [PMID: 25069823 DOI: 10.1111/apha.12354] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Revised: 07/14/2014] [Accepted: 07/17/2014] [Indexed: 11/27/2022]
Abstract
AIM Eukaryotic elongation factor 2 kinase (eEF2K), also known as calmodulin (CaM)-dependent protein kinase (CaMK) III, is a unique member of CaMK family protein. We have recently found that expression of eEF2K protein increased in mesenteric artery from spontaneously hypertensive rats. As pathogenesis of hypertension is in part regulated by vascular structural remodelling via proliferation and migration of vascular smooth muscle cells (SMCs), we tested the hypothesis that eEF2K controls SMCs proliferation and migration. METHODSAND RESULTS In rat mesenteric arterial SMCs, an eEF2K inhibitor, A-484954 (10 μm), significantly inhibited platelet-derived growth factor (PDGF)-BB (10 ng mL(-1) )-induced SMCs proliferation as determined by a cell counting and bromodeoxyuridine incorporation assay. PDGF-BB (10 ng mL(-1) )-induced SMCs migration was significantly inhibited by A-484954 (10 μm) as determined by a Boyden chamber assay. A-484954 (10 μm) significantly inhibited PDGF-BB (10 ng mL(-1) )-induced phosphorylation of eEF2K, extracellular signal-regulated kinase (ERK), Akt, p38 and heat-shock protein (HSP) 27 as determined by Western blotting. It was confirmed that a CaM inhibitor, W-7 (50 μm), inhibited PDGF-BB (10 ng mL(-1) )-induced phosphorylation of eEF2K. In an ex vivo mesenteric arterial ring assay, 10% foetal bovine serum-induced SMCs outgrowth was significantly inhibited by A-484954 (10 μm). CONCLUSION We for the first time revealed that eEF2K mediates PDGF-BB-induced SMCs proliferation and migration through activating ERK, Akt, p38 and HSP27 signals in a CaM-dependent manner. Our results suggest eEF2K as a novel pharmaceutical target for the prevention of hypertensive cardiovascular diseases.
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Affiliation(s)
- T. Usui
- Laboratory of Veterinary Pharmacology; School of Veterinary Medicine; Kitasato University; Towada Aomori Japan
| | - R. Nijima
- Laboratory of Veterinary Pharmacology; School of Veterinary Medicine; Kitasato University; Towada Aomori Japan
| | - T. Sakatsume
- Laboratory of Veterinary Pharmacology; School of Veterinary Medicine; Kitasato University; Towada Aomori Japan
| | - K. Otani
- Laboratory of Veterinary Pharmacology; School of Veterinary Medicine; Kitasato University; Towada Aomori Japan
| | - S. Kameshima
- Laboratory of Veterinary Pharmacology; School of Veterinary Medicine; Kitasato University; Towada Aomori Japan
| | - M. Okada
- Laboratory of Veterinary Pharmacology; School of Veterinary Medicine; Kitasato University; Towada Aomori Japan
| | - H. Yamawaki
- Laboratory of Veterinary Pharmacology; School of Veterinary Medicine; Kitasato University; Towada Aomori Japan
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3
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Usui T, Okada M, Hara Y, Yamawaki H. Eukaryotic elongation factor 2 kinase regulates the development of hypertension through oxidative stress-dependent vascular inflammation. Am J Physiol Heart Circ Physiol 2013; 305:H756-68. [PMID: 23812389 DOI: 10.1152/ajpheart.00373.2013] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Eukaryotic elongation factor 2 kinase (eEF2K) is a Ca2+/calmodulin-dependent protein kinase. We recently demonstrated that eEF2K protein increases in mesenteric artery from spontaneously hypertensive rats (SHR). Pathogenesis of hypertension is regulated in part by vascular inflammation. We tested the hypothesis whether eEF2K mediates vascular inflammatory responses and development of hypertension. In vascular endothelial cells, small interfering RNA (siRNA) against eEF2K inhibited induction of VCAM-1 and endothelial-selectin as well as monocyte adhesion by TNF-α (10 ng/ml). eEF2K siRNA inhibited phosphorylation of JNK and NF-κB p65 as well as reactive oxygen species (ROS) production by TNF-α. In vascular smooth muscle cells, eEF2K siRNA also inhibited VCAM-1 induction and phosphorylation of JNK and NF-κB by TNF-α. In vivo, increased blood pressure in SHR and ROS production, induction of inflammatory molecules, and hypertrophy in SHR superior mesenteric artery were reduced by an eEF2K inhibitor NH125 (500 μg·kg(-1)·day(-1)). In SHR superior mesenteric artery, impairment of ACh-induced relaxation was normalized by NH125. The present results for the first time demonstrate that eEF2K mediates TNF-α-induced vascular inflammation via ROS-dependent mechanism, which is at least partly responsible for the development of hypertension in SHR.
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Affiliation(s)
- Tatsuya Usui
- Laboratory of Veterinary Pharmacology, School of Veterinary Medicine, Kitasato University, Towada, Aomori, Japan
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4
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Tekedereli I, Alpay SN, Tavares CDJ, Cobanoglu ZE, Kaoud TS, Sahin I, Sood AK, Lopez-Berestein G, Dalby KN, Ozpolat B. Targeted silencing of elongation factor 2 kinase suppresses growth and sensitizes tumors to doxorubicin in an orthotopic model of breast cancer. PLoS One 2012; 7:e41171. [PMID: 22911754 PMCID: PMC3401164 DOI: 10.1371/journal.pone.0041171] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2012] [Accepted: 06/18/2012] [Indexed: 11/18/2022] Open
Abstract
Eukaryotic elongation factor 2 kinase (eEF-2K), through its phosphorylation of elongation factor 2 (eEF2), provides a mechanism by which cells can control the rate of the elongation phase of protein synthesis. The activity of eEF-2K is increased in rapidly proliferating malignant cells, is inhibited during mitosis, and may contribute to the promotion of autophagy in response to anti-cancer therapies. The purpose of this study was to examine the therapeutic potential of targeting eEF-2K in breast cancer tumors. Through the systemic administration of liposomal eEF-2K siRNA (twice a week, i.v. 150 µg/kg), the expression of eEF-2K was down-regulated in vivo in an orthotopic xenograft mouse model of a highly aggressive triple negative MDA-MB-231 tumor. This targeting resulted in a substantial decrease in eEF2 phosphorylation in the tumors, and led to the inhibition of tumor growth, the induction of apoptosis and the sensitization of tumors to the chemotherapy agent doxorubicin. eEF-2K down-modulation in vitro resulted in a decrease in the expression of c-Myc and cyclin D1 with a concomitant increase in the expression of p27Kip1. A decrease in the basal activity of c-Src (phospho-Tyr-416), focal adhesion kinase (phospho-Tyr-397), and Akt (phospho-Ser-473) was also detected following eEF-2K down-regulation in MDA-MB-231 cells, as determined by Western blotting. Where tested, similar results were seen in ER-positive MCF-7 cells. These effects were also accompanied by a decrease in the observed invasive phenotype of the MDA-MB-231 cells. These data support the notion that the disruption of eEF-2K expression in breast cancer cells results in the down-regulation of signaling pathways affecting growth, survival and resistance and has potential as a therapeutic approach for the treatment of breast cancer.
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Affiliation(s)
- Ibrahim Tekedereli
- Department of Experimental Therapeutics, University of Texas M. D. Anderson Cancer Center, Houston, Texas, United States of America
| | - S. Neslihan Alpay
- Department of Experimental Therapeutics, University of Texas M. D. Anderson Cancer Center, Houston, Texas, United States of America
| | - Clint D. J. Tavares
- Graduate Program in Cell and Molecular Biology, The University of Texas, Austin, Texas, United States of America
| | - Zehra E. Cobanoglu
- Department of Experimental Therapeutics, University of Texas M. D. Anderson Cancer Center, Houston, Texas, United States of America
| | - Tamer S. Kaoud
- Division of Medicinal Chemistry, College of Pharmacy, The University of Texas, Austin, Texas, United States of America
| | - Ibrahim Sahin
- Department of Experimental Therapeutics, University of Texas M. D. Anderson Cancer Center, Houston, Texas, United States of America
| | - Anil K. Sood
- Department of Gynecologic Oncology, University of Texas M. D. Anderson Cancer Center, Houston, Texas, United States of America
- Department of Cancer Biology, University of Texas M. D. Anderson Cancer Center, Houston, Texas, United States of America
- Center for RNAi and Non-Coding RNA, University of Texas M. D. Anderson Cancer Center, Houston, Texas, United States of America
| | - Gabriel Lopez-Berestein
- Department of Experimental Therapeutics, University of Texas M. D. Anderson Cancer Center, Houston, Texas, United States of America
- Department of Cancer Biology, University of Texas M. D. Anderson Cancer Center, Houston, Texas, United States of America
- Center for RNAi and Non-Coding RNA, University of Texas M. D. Anderson Cancer Center, Houston, Texas, United States of America
| | - Kevin N. Dalby
- Graduate Program in Cell and Molecular Biology, The University of Texas, Austin, Texas, United States of America
- Division of Medicinal Chemistry, College of Pharmacy, The University of Texas, Austin, Texas, United States of America
- * E-mail: (BO); (KND)
| | - Bulent Ozpolat
- Department of Experimental Therapeutics, University of Texas M. D. Anderson Cancer Center, Houston, Texas, United States of America
- Center for RNAi and Non-Coding RNA, University of Texas M. D. Anderson Cancer Center, Houston, Texas, United States of America
- * E-mail: (BO); (KND)
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5
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Devkota AK, Tavares CDJ, Warthaka M, Abramczyk O, Marshall KD, Kaoud TS, Gorgulu K, Ozpolat B, Dalby KN. Investigating the kinetic mechanism of inhibition of elongation factor 2 kinase by NH125: evidence of a common in vitro artifact. Biochemistry 2012; 51:2100-12. [PMID: 22352903 DOI: 10.1021/bi201787p] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Evidence that elongation factor 2 kinase (eEF-2K) has potential as a target for anticancer therapy and possibly for the treatment of depression is emerging. Here the steady-state kinetic mechanism of eEF-2K is presented using a peptide substrate and is shown to conform to an ordered sequential mechanism with ATP binding first. Substrate inhibition by the peptide was observed and revealed to be competitive with ATP, explaining the observed ordered mechanism. Several small molecules are reported to inhibit eEF-2K activity with the most notable being the histidine kinase inhibitor NH125, which has been used in a number of studies to characterize eEF-2K activity in cells. While NH125 was previously reported to inhibit eEF-2K in vitro with an IC(50) of 60 nM, its mechanism of action was not established. Using the same kinetic assay, the ability of an authentic sample of NH125 to inhibit eEF-2K was assessed over a range of substrate and inhibitor concentrations. A typical dose-response curve for the inhibition of eEF-2K by NH125 is best fit to an IC(50) of 18 ± 0.25 μM and a Hill coefficient of 3.7 ± 0.14, suggesting that NH125 is a weak inhibitor of eEF-2K under the experimental conditions of a standard in vitro kinase assay. To test the possibility that NH125 is a potent inhibitor of eEF2 phosphorylation, we assessed its ability to inhibit the phosphorylation of eEF2. Under standard kinase assay conditions, NH125 exhibits a similar weak ability to inhibit the phosphorylation of eEF2 by eEF-2K. Notably, the activity of NH125 is severely abrogated by the addition of 0.1% Triton to the kinase assay through a process that can be reversed upon dilution. These studies suggest that NH125 is a nonspecific colloidal aggregator in vitro, a notion further supported by the observation that NH125 inhibits other protein kinases, such as ERK2 and TRPM7 in a manner similar to that of eEF-2K. As NH125 is reported to inhibit eEF-2K in a cellular environment, its ability to inhibit eEF2 phosphorylation was assessed in MDA-MB-231 breast cancer, A549 lung cancer, and HEK-293T cell lines using a Western blot approach. No sign of a decrease in the level of eEF2 phosphorylation was observed up to 12 h following addition of NH125 to the media. Furthermore, contrary to the previously reported literatures, NH125 induced the phosphorylation of eEF-2.
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Affiliation(s)
- Ashwini K Devkota
- Graduate Program in Cell and Molecular Biology, The University of Texas, Austin, Texas 78712, United States
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6
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Py BF, Boyce M, Yuan J. A critical role of eEF-2K in mediating autophagy in response to multiple cellular stresses. Autophagy 2009; 5:393-6. [PMID: 19221463 DOI: 10.4161/auto.5.3.7762] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The phosphorylation of the subunit alpha of eukaryotic translation initiation factor 2 (eIF2alpha), a critical regulatory event in controlling protein translation, has recently been found to mediate the induction of autophagy. However, the mediators of autophagy downstream of eIF2alpha remain unknown. Here, we provide evidence that eIF2alpha phosphorylation is required for phosphorylation of eukaryotic elongation factor 2 (eEF-2) during nutrient starvation. In addition, we show that eukaryotic elongation factor 2 kinase (eEF-2K) is also required for autophagy signaling during ER stress, suggesting that phosphorylation of eEF-2 may serve as an integrator of various cell stresses for autophagy signaling. On the other hand, although the activation of eEF-2K in response to starvation requires the phosphorylation of eIF2alpha, additional pathways relying partly on Ca(2+) flux may control eEF-2K activity during ER stress, as eIF2alpha phosphorylation is dispensable for both eEF-2 phosphorylation and autophagy in this context.
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Affiliation(s)
- Bénédicte F Py
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
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7
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Chen JH, Riazy M, Smith EM, Proud CG, Steinbrecher UP, Duronio V. Oxidized LDL-Mediated Macrophage Survival Involves Elongation Factor-2 Kinase. Arterioscler Thromb Vasc Biol 2009; 29:92-8. [DOI: 10.1161/atvbaha.108.174599] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Johnny H. Chen
- From the Department of Medicine (J.H.C., M.R., U.P.S., V.D.), University of British Columbia, and Vancouver Coastal Health Research Institute, Vancouver, BC, Canada; Genome Damage and Stability Centre (E.M.S.), University of Sussex, Falmer, Brighton, UK; and the School of Biological Sciences (C.G.P.), University of Southampton, UK
| | - Maziar Riazy
- From the Department of Medicine (J.H.C., M.R., U.P.S., V.D.), University of British Columbia, and Vancouver Coastal Health Research Institute, Vancouver, BC, Canada; Genome Damage and Stability Centre (E.M.S.), University of Sussex, Falmer, Brighton, UK; and the School of Biological Sciences (C.G.P.), University of Southampton, UK
| | - Ewan M. Smith
- From the Department of Medicine (J.H.C., M.R., U.P.S., V.D.), University of British Columbia, and Vancouver Coastal Health Research Institute, Vancouver, BC, Canada; Genome Damage and Stability Centre (E.M.S.), University of Sussex, Falmer, Brighton, UK; and the School of Biological Sciences (C.G.P.), University of Southampton, UK
| | - Christopher G. Proud
- From the Department of Medicine (J.H.C., M.R., U.P.S., V.D.), University of British Columbia, and Vancouver Coastal Health Research Institute, Vancouver, BC, Canada; Genome Damage and Stability Centre (E.M.S.), University of Sussex, Falmer, Brighton, UK; and the School of Biological Sciences (C.G.P.), University of Southampton, UK
| | - Urs P. Steinbrecher
- From the Department of Medicine (J.H.C., M.R., U.P.S., V.D.), University of British Columbia, and Vancouver Coastal Health Research Institute, Vancouver, BC, Canada; Genome Damage and Stability Centre (E.M.S.), University of Sussex, Falmer, Brighton, UK; and the School of Biological Sciences (C.G.P.), University of Southampton, UK
| | - Vincent Duronio
- From the Department of Medicine (J.H.C., M.R., U.P.S., V.D.), University of British Columbia, and Vancouver Coastal Health Research Institute, Vancouver, BC, Canada; Genome Damage and Stability Centre (E.M.S.), University of Sussex, Falmer, Brighton, UK; and the School of Biological Sciences (C.G.P.), University of Southampton, UK
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8
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Wu H, Yang JM, Jin S, Zhang H, Hait WN. Elongation Factor-2 Kinase Regulates Autophagy in Human Glioblastoma Cells. Cancer Res 2006; 66:3015-23. [PMID: 16540650 DOI: 10.1158/0008-5472.can-05-1554] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Elongation factor-2 kinase (eEF-2 kinase), also known as Ca(2+)/calmodulin-dependent kinase III, regulates protein synthesis by controlling the rate of peptide chain elongation. The activity of eEF-2 kinase is increased in glioblastoma and other malignancies, yet its role in neoplasia is uncertain. Recent evidence suggests that autophagy plays an important role in oncogenesis and that this can be regulated by mammalian target of rapamycin (mTOR). Because eEF-2 kinase lies downstream of mTOR, we studied the role of eEF-2 kinase in autophagy using human glioblastoma cell lines. Knockdown of eEF-2 kinase by RNA interference inhibited autophagy in glioblastoma cell lines, as measured by light chain 3 (LC3)-II formation, acidic vesicular organelle staining, and electron microscopy. In contrast, overexpression of eEF-2 kinase increased autophagy. Furthermore, inhibition of autophagy markedly decreased the viability of glioblastoma cells grown under conditions of nutrient depletion. Nutrient deprivation increased eEF-2 kinase activity and decreased the activity of S6 kinase, suggesting an involvement of mTOR pathway in the eEF-2 kinase regulation of autophagy. These results suggest that eEF-2 kinase plays a regulatory role in the autophagic process in tumor cells; and eEF-2 kinase is a downstream member of the mTOR signaling; eEF-2 kinase may promote cancer cell survival under conditions of nutrient deprivation through regulating autophagy. Therefore, eEF-2 kinase may be a part of a survival mechanism in glioblastoma and targeting this kinase may represent a novel approach to cancer treatment.
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Affiliation(s)
- Hao Wu
- Department of Pharmacology, University of Medicine and Dentistry of New Jersey/Robert Wood Johnson Medical School, New Brunswick, NJ 08901, USA
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9
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Nairn AC, Matsushita M, Nastiuk K, Horiuchi A, Mitsui K, Shimizu Y, Palfrey HC. Elongation factor-2 phosphorylation and the regulation of protein synthesis by calcium. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2002; 27:91-129. [PMID: 11575162 DOI: 10.1007/978-3-662-09889-9_4] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Affiliation(s)
- A C Nairn
- Laboratory of Molecular and Cellular Neuroscience, Rockefeller University, New York, New York 10021, USA
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Caraglia M, Budillon A, Vitale G, Lupoli G, Tagliaferri P, Abbruzzese A. Modulation of molecular mechanisms involved in protein synthesis machinery as a new tool for the control of cell proliferation. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:3919-36. [PMID: 10866791 DOI: 10.1046/j.1432-1327.2000.01465.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the past years, the attention of scientists has focused mainly on the study of the genetic information and alterations that regulate eukaryotic cell proliferation and that lead to neoplastic transformation. All therapeutic strategies against cancer are, to date, directed at DNA either with cytotoxic drugs or gene therapy. Little or no interest has been aroused by protein synthesis mechanisms. However, an increasing body of data is emerging about the involvement of translational processes and factors in control of cell proliferation, indicating that protein synthesis can be an additional target for anticancer strategies. In this paper we review the novel insights on the biochemical and molecular events leading to protein biosynthesis and we describe their involvement in cell proliferation and tumorigenesis. A possible mechanistic explanation is given by the interactions that occur between protein synthesis machinery and the proliferative signal transduction pathways and that are therefore suitable targets for indirect modulation of protein synthesis. We briefly describe the molecular tools used to block protein synthesis and the attempts made at increasing their efficacy. Finally, we propose a new multimodal strategy against cancer based on the simultaneous intervention on protein synthesis and signal transduction.
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Affiliation(s)
- M Caraglia
- Dipartimento di Biochimica e Biofisica, Seconda Università di Napoli, Italy
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11
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Parmer TG, Ward MD, Yurkow EJ, Vyas VH, Kearney TJ, Hait WN. Activity and regulation by growth factors of calmodulin-dependent protein kinase III (elongation factor 2-kinase) in human breast cancer. Br J Cancer 1999; 79:59-64. [PMID: 10408694 PMCID: PMC2362180 DOI: 10.1038/sj.bjc.6690012] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/1997] [Revised: 02/16/1998] [Accepted: 03/24/1998] [Indexed: 11/09/2022] Open
Abstract
Calmodulin-dependent protein kinase III (CaM kinase III, elongation factor-2 kinase) is a unique member of the Ca2+/CaM-dependent protein kinase family. Activation of CaM kinase III leads to the selective phosphorylation of elongation factor 2 (eEF-2) and transient inhibition of protein synthesis. Recent cloning and sequencing of CaM kinase III revealed that this enzyme represents a new superfamily of protein kinases. The activity of CaM kinase III is selectively activated in proliferating cells; inhibition of the kinase blocked cells in G0/G1-S and decreased viability. To determine the significance of CaM kinase III in breast cancer, we measured the activity of the kinase in human breast cancer cell lines as well as in fresh surgical specimens. The specific activity of CaM kinase III in human breast cancer cell lines was equal to or greater than that seen in a variety of cell lines with similar rates of proliferation. The specific activity of CaM kinase III was markedly increased in human breast tumour specimens compared with that of normal adjacent breast tissue. The activity of this enzyme was regulated by breast cancer mitogens. In serum-deprived MDA-MB-231 cells, the combination of insulin-like growth factor I (IGF-I) and epidermal growth factor (EGF) stimulated cell proliferation and activated CaM kinase III to activities observed in the presence of 10% serum. Inhibition of enzyme activity blocked cell proliferation induced by growth factors. In MCF-7 cells separated by fluorescence-activated cell sorting. CaM kinase III was increased in S-phase over that of other phases of the cell cycle. In summary, the activity of Ca2+/CaM-dependent protein kinase III is controlled by breast cancer mitogens and appears to be constitutively activated in human breast cancer. These results suggest that CaM kinase III may contribute an important link between growth factor/receptor interactions, protein synthesis and the induction of cellular proliferation in human breast cancer.
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Affiliation(s)
- T G Parmer
- Department of Pharmacology, The Cancer Institute of New Jersey, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, New Brunswick 08901, USA
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12
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Nilsson A, Nygård O. Phosphorylation of eukaryotic elongation factor 2 in differentiating and proliferating HL-60 cells. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1268:263-8. [PMID: 7548224 DOI: 10.1016/0167-4889(95)00084-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Ca(2+)-and calmodulin-dependent protein kinase III (CaM PKIII) phosphorylates eukaryotic elongation factor 2 (eEF-2) in HL-60 cells. Dephosphorylation of the factor in these cells is catalyzed by phosphoprotein phosphatase 2A alone. Differentiation of the HL-60 cells by all-trans retinoic acid resulted in a reduced growth rate and a marked decrease in the intracellular concentration of eEF-2. During differentiation the activity of the eEF-2 kinase is gradually reduced and reaches 10% of that found in undifferentiated cells 5 days after the onset of differentiation. The capacity to dephosphorylate phospho-eEF-2 remained unaltered in the growth-arrested cells. Differentiation without reduced proliferation was induced in the HL-60 cells by interferon-gamma. Under these conditions, differentiation had no effect on the cellular content of eEF-2 or the ability to dephosphorylate phospho-eEF-2. However, the differentiated cells showed a dramatic decrease in the specific activity of the eEF-2 kinase. The results show that the cellular content of eEF-2 varies with the rate of proliferation and that the activity of the eEF-2 kinase is high in undifferentiated proliferating cells and decreases upon differentiation even under conditions of an unaltered growth rate.
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Affiliation(s)
- A Nilsson
- Department of Zoological Cell Biology, Arrhenius Laboratories E5, Stockholm University, Sweden
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13
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Nilsson A, Nygård O. Effect of oxidizing agents and haemin on the phosphorylation of eukaryotic elongation factor 2 in rabbit reticulocyte lysates. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1260:200-6. [PMID: 7841197 DOI: 10.1016/0167-4781(94)00198-c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Incubation of rabbit reticulocyte lysates in the absence of added haemin resulted in the phosphorylation of a 95 kDa protein. This protein was suggested to be elongation factor 2 (eEF-2) based on the following observations, (i) phosphorylation of the 95 kDa protein was Ca2+ and CaM-dependent. (ii) eEF-2 supplemented to the lysates became phosphorylated and co-migrated with the endogenous 95 kDa phosphoprotein upon electrophoresis in SDS gels. (iii) The tryptophane specific cleavage pattern obtained from the isolated 95 kDa phosphoprotein was identical to that of phosphorylated eEF-2. Phosphorylation of the 95 kDa protein was stimulated by oxidizing agents such as oxidized glutathione and NAD+ and inhibited by addition of haemin. The haemin concentration needed for 50% inhibition (IC50) was 2.5 microM. Haemin also had an inhibitory effect on eEF-2 phosphorylation in a system containing highly purified components (IC50 = 2 microM). In this system haemin inhibited phosphorylation of eEF-2 even in the presence of a 100-fold excess of beta-mercaptoethanol. Oxidizing agents had no effect on the kinase activity in the purified system.
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Affiliation(s)
- A Nilsson
- Department of Zoological Cell Biology, Arrhenius Laboratories E5, Stockholm University, Sweden
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Derventzi A, Rattan SI, Clark BF. Phorbol ester PMA stimulates protein synthesis and increases the levels of active elongation factors EF-1 alpha and EF-2 in ageing human fibroblasts. Mech Ageing Dev 1993; 69:193-205. [PMID: 8412369 DOI: 10.1016/0047-6374(93)90023-k] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Phorbol esters modulate gene expression, reorganize the cytoskeleton and stimulate bulk protein synthesis and the steps of initiation and elongation. We have observed that a phorbol ester PMA stimulates protein synthesis and increases the amounts of active elongation factors, EF-1 alpha and EF-2 in cultured human fibroblasts MRC-5 undergoing ageing. Although bulk protein synthesis slows down during ageing, the cellular response to the stimulatory effects of PMA is higher in senescent cells. Similarly, despite the age-related decline in the amounts of active EF-1 alpha and EF-2, senescent cells exhibit a higher response to PMA. The results indicate an age-dependent increase of cellular responsiveness to PMA and provide evidence about both the integrity of the translational apparatus and the effectiveness of the signal transduction pathways during cellular ageing. In comparison, the effects of PMA on SV40-transformed MRC-5V2 cells were minimal.
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Affiliation(s)
- A Derventzi
- Department of Chemistry, Aarhus University, Denmark
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Fujiki H, Suganuma M. Tumor promotion by inhibitors of protein phosphatases 1 and 2A: the okadaic acid class of compounds. Adv Cancer Res 1993; 61:143-94. [PMID: 8394044 DOI: 10.1016/s0065-230x(08)60958-6] [Citation(s) in RCA: 241] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- H Fujiki
- Cancer Prevention Division, National Cancer Center Research Institute, Tokyo, Japan
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