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Cdk1-mediated phosphorylation of human ATF7 at Thr-51 and Thr-53 promotes cell-cycle progression into M phase. PLoS One 2014; 9:e116048. [PMID: 25545367 PMCID: PMC4278844 DOI: 10.1371/journal.pone.0116048] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 11/30/2014] [Indexed: 12/22/2022] Open
Abstract
Activating transcription factor 2 (ATF2) and its homolog ATF7 are phosphorylated at Thr-69/Thr-71 and at Thr-51/Thr-53, respectively, by stress-activated MAPKs regulating their transcriptional functions in G1 and S phases. However, little is known about the role of ATF2 and ATF7 in G2/M phase. Here, we show that Cdk1-cyclin B1 phosphorylates ATF2 at Thr-69/Thr-71 and ATF7 at Thr-51/Thr-53 from early prophase to anaphase in the absence of any stress stimulation. Knockdown of ATF2 or ATF7 decreases the rate of cell proliferation and the number of cells in M-phase. In particular, the knockdown of ATF7 severely inhibits cell proliferation and G2/M progression. The inducible expression of a mitotically nonphosphorylatable version of ATF7 inhibits G2/M progression despite the presence of endogenous ATF7. We also show that mitotic phosphorylation of ATF7 promotes the activation of Aurora kinases, which are key enzymes for early mitotic events. These results suggest that the Cdk1-mediated phosphorylation of ATF7 facilitates G2/M progression, at least in part, by enabling Aurora signaling.
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Keklikoglu N, Akinci S. ATF-2 immunoreactivity in post-mitotic and terminally differentiated human odontoblasts. Med Mol Morphol 2014; 48:164-8. [PMID: 25417007 DOI: 10.1007/s00795-014-0092-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Accepted: 11/06/2014] [Indexed: 10/24/2022]
Abstract
Activating transcription factor 2 (ATF-2/CRE-BP1; cAMP-responsive element binding protein 1) is a member of nuclear transcription factor activator protein-1 (AP-1) family. AP-1 regulates cellular processes including growth, proliferation, differentiation and apoptosis. However, biological relationship of cellular process to each member of the AP-1 family is not clear yet. The objective of the present study was to compare the ATF-2 immunoreactivity in the post-mitotic and terminally differentiated odontoblasts and in the pulpal fibroblasts which can be divided by mitosis when required. Fibroblasts at various stages of differentiation co-exist in the human dental pulp. ATF-2 was investigated immunohistochemically in 20 permanent human teeth. According to the findings obtained, the mean percentage of ATF-2 positive cells was 68.5 ± 19.2% in the odontoblasts and 22.8 ± 13.7% in the pulpal fibroblasts. The comparison of ATF-2 positivity revealed a statistically significant difference between odontoblasts and pulpal fibroblasts. These findings have suggested that ATF-2 is more associated with cell survival rather than cell proliferation, and revealed much of effectiveness in maintaining terminal differentiation than the various differentiation stages of the cells.
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Affiliation(s)
- Nurullah Keklikoglu
- Division of Basic Sciences, Department of Histology and Embryology, Faculty of Dentistry, Istanbul University, Capa, Istanbul, Turkey.
| | - Sevtap Akinci
- Division of Basic Sciences, Department of Histology and Embryology, Faculty of Dentistry, Istanbul University, Capa, Istanbul, Turkey
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Foerster F, Braig S, Moser C, Kubisch R, Busse J, Wagner E, Schmoeckel E, Mayr D, Schmitt S, Huettel S, Zischka H, Mueller R, Vollmar AM. Targeting the actin cytoskeleton: selective antitumor action via trapping PKCɛ. Cell Death Dis 2014; 5:e1398. [PMID: 25165884 PMCID: PMC4454332 DOI: 10.1038/cddis.2014.363] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Revised: 07/14/2014] [Accepted: 07/16/2014] [Indexed: 12/18/2022]
Abstract
Targeting the actin cytoskeleton (CSK) of cancer cells offers a valuable strategy in cancer therapy. There are a number of natural compounds that interfere with the actin CSK, but the mode of their cytotoxic action and, moreover, their tumor-specific mechanisms are quite elusive. We used the myxobacterial compound Chondramide as a tool to first elucidate the mechanisms of cytotoxicity of actin targeting in breast cancer cells (MCF7, MDA-MB-231). Chondramide inhibits cellular actin filament dynamics shown by a fluorescence-based analysis (fluorescence recovery after photobleaching (FRAP)) and leads to apoptosis characterized by phosphatidylserine exposure, release of cytochrome C from mitochondria and finally activation of caspases. Chondramide enhances the occurrence of mitochondrial permeability transition (MPT) by affecting known MPT modulators: Hexokinase II bound to the voltage-dependent anion channel (VDAC) translocated from the outer mitochondrial membrane to the cytosol and the proapoptotic protein Bad were recruited to the mitochondria. Importantly, protein kinase C-ɛ (PKCɛ), a prosurvival kinase possessing an actin-binding site and known to regulate the hexokinase/VDAC interaction as well as Bad phosphorylation was identified as the link between actin CSK and apoptosis induction. PKCɛ, which was found overexpressed in breast cancer cells, accumulated in actin bundles induced by Chondramide and lost its activity. Our second goal was to characterize the potential tumor-specific action of actin-binding agents. As the nontumor breast epithelial cell line MCF-10A in fact shows resistance to Chondramide-induced apoptosis and notably express low level of PKCɛ, we suggest that trapping PKCɛ via Chondramide-induced actin hyperpolymerization displays tumor cell specificity. Our work provides a link between targeting the ubiquitously occurring actin CSK and selective inhibition of pro-tumorigenic PKCɛ, thus setting the stage for actin-stabilizing agents as innovative cancer drugs. This is moreover supported by the in vivo efficacy of Chondramide triggered by abrogation of PKCɛ signaling shown in a xenograft breast cancer model.
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Affiliation(s)
- F Foerster
- Department of Pharmacy, Pharmaceutical Biology, University of Munich, Munich, Germany
| | - S Braig
- Department of Pharmacy, Pharmaceutical Biology, University of Munich, Munich, Germany
| | - C Moser
- Department of Pharmacy, Pharmaceutical Biology, University of Munich, Munich, Germany
| | - R Kubisch
- Department of Pharmacy, Pharmaceutical Biology, University of Munich, Munich, Germany
| | - J Busse
- Department of Pharmacy, Pharmaceutical Biotechnology, University of Munich, Munich, Germany
| | - E Wagner
- Department of Pharmacy, Pharmaceutical Biotechnology, University of Munich, Munich, Germany
| | - E Schmoeckel
- Institute of Pathology, University of Munich, Munich, Germany
| | - D Mayr
- Institute of Pathology, University of Munich, Munich, Germany
| | - S Schmitt
- Institute for Molecular Toxicology and Pharmacology, Helmholtz Centre Munich, German Research Center for Environmental Health, Neuherberg, Germany
| | - S Huettel
- Institute of Pathology, University of Munich, Munich, Germany
| | - H Zischka
- Institute for Molecular Toxicology and Pharmacology, Helmholtz Centre Munich, German Research Center for Environmental Health, Neuherberg, Germany
| | - R Mueller
- Helmholtz Institute for Pharmaceutical Research Saarland, Helmholtz Centre for Infection Research and Department of Pharmaceutical Biotechnology, Saarland University, Saarbrücken, Germany
| | - A M Vollmar
- Department of Pharmacy, Pharmaceutical Biology, University of Munich, Munich, Germany
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Abstract
Protein location and function can change dynamically depending on many factors, including environmental stress, disease state, age, developmental stage, and cell type. Here, we describe an integrative computational framework, called the conditional function predictor (CoFP; http://nbm.ajou.ac.kr/cofp/), for predicting changes in subcellular location and function on a proteome-wide scale. The essence of the CoFP approach is to cross-reference general knowledge about a protein and its known network of physical interactions, which typically pool measurements from diverse environments, against gene expression profiles that have been measured under specific conditions of interest. Using CoFP, we predict condition-specific subcellular locations, biological processes, and molecular functions of the yeast proteome under 18 specified conditions. In addition to highly accurate retrieval of previously known gold standard protein locations and functions, CoFP predicts previously unidentified condition-dependent locations and functions for nearly all yeast proteins. Many of these predictions can be confirmed using high-resolution cellular imaging. We show that, under DNA-damaging conditions, Tsr1, Caf120, Dip5, Skg6, Lte1, and Nnf2 change subcellular location and RNA polymerase I subunit A43, Ino2, and Ids2 show changes in DNA binding. Beyond specific predictions, this work reveals a global landscape of changing protein location and function, highlighting a surprising number of proteins that translocate from the mitochondria to the nucleus or from endoplasmic reticulum to Golgi apparatus under stress.
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55
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MicroRNA-451 regulates activating transcription factor 2 expression and inhibits liver cancer cell migration. Oncol Rep 2014; 32:1021-8. [PMID: 24968707 DOI: 10.3892/or.2014.3296] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Accepted: 06/11/2014] [Indexed: 11/05/2022] Open
Abstract
Accumulating evidence suggests that microRNAs (miRNAs) can function as oncogenes or as tumor suppressor genes depending on the tissue type or target. Therefore, clarification of the specific roles of miRNAs is vital for the diagnosis and treatment of cancer. In the present study, miR-451 was found to be downregulated in hepatocellular carcinoma (HCC) tissues when compared to that in adjacent tissues. Functional analysis showed that, in vitro, miR-451 inhibited the migration of hepatoma cell lines HepG2 and SK-Hep-1. Further investigation of the molecular mechanisms identified activating transcription factor 2 (ATF2) as a target of miR-451. miR-451 inhibited ATF2 expression by binding to the 3'UTR. An in vivo assay revealed a significant negative correlation between miR-451 and ATF2 in liver cancer tissues. According to previous findings reported in the literature, the opposing functions of ATF2 are related to its subcellular localization. In the nucleus, ATF2 displays oncogenic activities in melanoma. In the present study, ATF2 exhibited a higher expression level in the nucleus in tumoral tissues of HCC as detected by immunohistochemistry. In conclusion, in this study, we identified a potential target of miR-451, ATF2, and revealed a novel role of miR-451 in the inhibition of the migratory ability of hepatoma cell lines.
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Abstract
Protein kinase C (PKC) is a family of phospholipid-dependent serine/threonine kinases, which can be further classified into three PKC isozymes subfamilies: conventional or classic, novel or nonclassic, and atypical. PKC isozymes are known to be involved in cell proliferation, survival, invasion, migration, apoptosis, angiogenesis, and drug resistance. Because of their key roles in cell signaling, PKC isozymes also have the potential to be promising therapeutic targets for several diseases, such as cardiovascular diseases, immune and inflammatory diseases, neurological diseases, metabolic disorders, and multiple types of cancer. This review primarily focuses on the activation, mechanism, and function of PKC isozymes during cancer development and progression.
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Jain K, Basu A. The Multifunctional Protein Kinase C-ε in Cancer Development and Progression. Cancers (Basel) 2014; 6:860-78. [PMID: 24727247 PMCID: PMC4074807 DOI: 10.3390/cancers6020860] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 03/27/2014] [Accepted: 04/01/2014] [Indexed: 12/31/2022] Open
Abstract
The protein kinase C (PKC) family proteins are important signal transducers and have long been the focus of cancer research. PKCɛ, a member of this family, is overexpressed in most solid tumors and plays critical roles in different processes that lead to cancer development. Studies using cell lines and animal models demonstrated the transforming potential of PKCɛ. While earlier research established the survival functions of PKCɛ, recent studies revealed its role in cell migration, invasion and cancer metastasis. PKCɛ has also been implicated in epithelial to mesenchymal transition (EMT), which may be the underlying mechanism by which it contributes to cell motility. In addition, PKCɛ affects cell-extracellular matrix (ECM) interactions by direct regulation of the cytoskeletal elements. Recent studies have also linked PKCɛ signaling to cancer stem cell functioning. This review focuses on the role of PKCɛ in different processes that lead to cancer development and progression. We also discussed current literatures on the pursuit of PKCɛ as a target for cancer therapy.
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Affiliation(s)
- Kirti Jain
- Department of Molecular and Medical Genetics, University of North Texas Health Science Center, Institute for Cancer Research, and Focused on Resources for her Health Education and Research, Fort Worth, TX 76107, USA.
| | - Alakananda Basu
- Department of Molecular and Medical Genetics, University of North Texas Health Science Center, Institute for Cancer Research, and Focused on Resources for her Health Education and Research, Fort Worth, TX 76107, USA.
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Wang D, Yan X, Xia M, Yang Y, Li D, Li X, Song F, Ling W. Coenzyme Q10 promotes macrophage cholesterol efflux by regulation of the activator protein-1/miR-378/ATP-binding cassette transporter G1-signaling pathway. Arterioscler Thromb Vasc Biol 2014; 34:1860-70. [PMID: 24675662 DOI: 10.1161/atvbaha.113.302879] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
OBJECTIVE Recent studies have shown the role of miRNAs in macrophage reverse cholesterol transport and atherogenesis. We hypothesized that coenzyme Q10 (CoQ10) may increase macrophage reverse cholesterol transport by regulating miRNA expression that contributes to the prevention of atherosclerosis. APPROACH AND RESULTS CoQ10 treatment suppressed oxidized low-density lipoprotein-induced macrophage foam cell formation by ameliorating the binding of activator protein-1 to the putative promoter region of miR-378 primary transcript, thus decreasing the miR-378 level and enhancing the ATP-binding cassette transporter G1-mediated macrophage cholesterol efflux to high-density lipoprotein. Subsequently, the axis of activator protein-1/miR-378/ATP-binding cassette transporter G1 cholesterol efflux was confirmed in peritoneal macrophages isolated from CoQ10-treated apolipoprotein E-deficient mice. Finally, CoQ10 consumption promoted macrophage reverse cholesterol transport and inhibited the progression of atherosclerosis in apolipoprotein E-deficient mice. CONCLUSIONS This study identified activator protein-1/miR-378/ATP-binding cassette transporter G1 as a novel cascade for CoQ10 in facilitating macrophage cholesterol efflux in vitro and in vivo. Our data thus imply that both CoQ10 and miR-378 are promising candidates for atherosclerosis prevention and treatment.
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Affiliation(s)
- Dongliang Wang
- From the Department of Nutrition, School of Public Health, Sun Yat-Sen University (Northern Campus), Guangzhou, Guangdong Province, People's Republic of China (D.W., X.Y., M.X., Y.Y., D.L., X.L., F.S., W.L.); and Guangdong Provincial Key Laboratory of Food, Nutrition and Health, Department of Nutrition, School of Public Health, Sun Yat-Sen University (Northern Campus), Guangzhou, Guangdong Province, People's Republic of China (D.W., M.X., Y.Y., D.L., W.L.)
| | - Xiao Yan
- From the Department of Nutrition, School of Public Health, Sun Yat-Sen University (Northern Campus), Guangzhou, Guangdong Province, People's Republic of China (D.W., X.Y., M.X., Y.Y., D.L., X.L., F.S., W.L.); and Guangdong Provincial Key Laboratory of Food, Nutrition and Health, Department of Nutrition, School of Public Health, Sun Yat-Sen University (Northern Campus), Guangzhou, Guangdong Province, People's Republic of China (D.W., M.X., Y.Y., D.L., W.L.)
| | - Min Xia
- From the Department of Nutrition, School of Public Health, Sun Yat-Sen University (Northern Campus), Guangzhou, Guangdong Province, People's Republic of China (D.W., X.Y., M.X., Y.Y., D.L., X.L., F.S., W.L.); and Guangdong Provincial Key Laboratory of Food, Nutrition and Health, Department of Nutrition, School of Public Health, Sun Yat-Sen University (Northern Campus), Guangzhou, Guangdong Province, People's Republic of China (D.W., M.X., Y.Y., D.L., W.L.)
| | - Yan Yang
- From the Department of Nutrition, School of Public Health, Sun Yat-Sen University (Northern Campus), Guangzhou, Guangdong Province, People's Republic of China (D.W., X.Y., M.X., Y.Y., D.L., X.L., F.S., W.L.); and Guangdong Provincial Key Laboratory of Food, Nutrition and Health, Department of Nutrition, School of Public Health, Sun Yat-Sen University (Northern Campus), Guangzhou, Guangdong Province, People's Republic of China (D.W., M.X., Y.Y., D.L., W.L.)
| | - Dan Li
- From the Department of Nutrition, School of Public Health, Sun Yat-Sen University (Northern Campus), Guangzhou, Guangdong Province, People's Republic of China (D.W., X.Y., M.X., Y.Y., D.L., X.L., F.S., W.L.); and Guangdong Provincial Key Laboratory of Food, Nutrition and Health, Department of Nutrition, School of Public Health, Sun Yat-Sen University (Northern Campus), Guangzhou, Guangdong Province, People's Republic of China (D.W., M.X., Y.Y., D.L., W.L.)
| | - Xinrui Li
- From the Department of Nutrition, School of Public Health, Sun Yat-Sen University (Northern Campus), Guangzhou, Guangdong Province, People's Republic of China (D.W., X.Y., M.X., Y.Y., D.L., X.L., F.S., W.L.); and Guangdong Provincial Key Laboratory of Food, Nutrition and Health, Department of Nutrition, School of Public Health, Sun Yat-Sen University (Northern Campus), Guangzhou, Guangdong Province, People's Republic of China (D.W., M.X., Y.Y., D.L., W.L.)
| | - Fenglin Song
- From the Department of Nutrition, School of Public Health, Sun Yat-Sen University (Northern Campus), Guangzhou, Guangdong Province, People's Republic of China (D.W., X.Y., M.X., Y.Y., D.L., X.L., F.S., W.L.); and Guangdong Provincial Key Laboratory of Food, Nutrition and Health, Department of Nutrition, School of Public Health, Sun Yat-Sen University (Northern Campus), Guangzhou, Guangdong Province, People's Republic of China (D.W., M.X., Y.Y., D.L., W.L.)
| | - Wenhua Ling
- From the Department of Nutrition, School of Public Health, Sun Yat-Sen University (Northern Campus), Guangzhou, Guangdong Province, People's Republic of China (D.W., X.Y., M.X., Y.Y., D.L., X.L., F.S., W.L.); and Guangdong Provincial Key Laboratory of Food, Nutrition and Health, Department of Nutrition, School of Public Health, Sun Yat-Sen University (Northern Campus), Guangzhou, Guangdong Province, People's Republic of China (D.W., M.X., Y.Y., D.L., W.L.).
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59
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Mitochondrial ion channels as oncological targets. Oncogene 2014; 33:5569-81. [DOI: 10.1038/onc.2013.578] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Revised: 12/04/2013] [Accepted: 12/05/2013] [Indexed: 02/06/2023]
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The ROS/JNK/ATF2 pathway mediates selenite-induced leukemia NB4 cell cycle arrest and apoptosis in vitro and in vivo. Cell Death Dis 2013; 4:e973. [PMID: 24357804 PMCID: PMC3877548 DOI: 10.1038/cddis.2013.475] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Revised: 10/31/2013] [Accepted: 10/31/2013] [Indexed: 01/02/2023]
Abstract
It has previously been shown that selenite can act as an antitumor agent and inhibit cancer cell growth, although the mechanism responsible for this effect is not well understood. In this study, we have shown that selenite can induce cell cycle arrest and apoptosis in NB4 cells. Selenite treatment of these cells also inhibited the JNK/ATF2 axis. Further experiments demonstrated that selenite-induced production of reactive oxygen species (ROS) worked as an upstream of the JNK/ATF2 axis, cell cycle arrest and apoptosis. Inactivation of ATF2 resulted in decreased affinity of this transcription factor for the promoters of cyclin A, cyclin D3 and CDK4, which led to the arrest of the NB4 cells in the G0/G1 phase. Finally, in vivo experiments confirmed the antitumor activity of selenite and the mechanisms that were described in vitro. Taken together, our results indicate that selenite-induced ROS arrest NB4 cells at G0/G1 phase through inhibiting the JNK/ATF2 axis in vitro and in vivo.
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61
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Wu P, Yuan SS, Ho CC, Hsieh WY, Hong QS, Yu SL, Chen W, Chen HY, Wang CD, Li KC, Yang PC, Chen HW. Focal amplification of HOXD-harboring chromosome region is implicated in multiple-walled carbon nanotubes-induced carcinogenicity. NANO LETTERS 2013; 13:4632-41. [PMID: 23984819 DOI: 10.1021/nl401658c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Multiple-walled carbon nanotubes (MWCNTs) may cause carcinogenesis. We found that long-term exposure to MWCNTs can induce irreversible oncogenic transformation of human bronchial epithelial cells and tumorigenicity in vivo. A genome-wide array-comparative genomic hybridization (aCGH) analysis revealed global chromosomal aberration in MWCNTs-treated clones, predominantly at chromosome 2q31-32, where the potential oncogenes HOXD9 and HOXD13 are located. Functional assays confirmed that this variation can modulate oncogenic signaling and plays a part in MWCNTs-induced tumorigenesis, suggesting that MWCNTs are carcinogens that act by altering genomic stability and oncogenic copy numbers.
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Affiliation(s)
- Ping Wu
- Department and Institute of Pharmacology, School of Medicine, National Yang-Ming University , Taipei, Taiwan 112
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Varsano T, Lau E, Feng Y, Garrido M, Milan L, Heynen-Genel S, Hassig CA, Ronai ZA. Inhibition of melanoma growth by small molecules that promote the mitochondrial localization of ATF2. Clin Cancer Res 2013; 19:2710-22. [PMID: 23589174 DOI: 10.1158/1078-0432.ccr-12-2689] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE Effective therapy for malignant melanoma, the leading cause of death from skin cancer, remains an area of significant unmet need in oncology. The elevated expression of PKCε in advanced metastatic melanoma results in the increased phosphorylation of the transcription factor ATF2 on threonine 52, which causes its nuclear localization and confers its oncogenic activities. The nuclear-to-mitochondrial translocation of ATF2 following genotoxic stress promotes apoptosis, a function that is largely lost in melanoma cells, due to its confined nuclear localization. Therefore, promoting the nuclear export of ATF2, which sensitizes melanoma cells to apoptosis, represents a novel therapeutic modality. EXPERIMENTAL DESIGN We conducted a pilot high-throughput screen of 3,800 compounds to identify small molecules that promote melanoma cell death by inducing the cytoplasmic localization of ATF2. The imaging-based ATF2 translocation assay was conducted using UACC903 melanoma cells that stably express doxycycline-inducible GFP-ATF2. RESULTS We identified two compounds (SBI-0089410 and SBI-0087702) that promoted the cytoplasmic localization of ATF2, reduced cell viability, inhibited colony formation, cell motility, and anchorage-free growth, and increased mitochondrial membrane permeability. SBI-0089410 inhibited the 12-O-tetradecanoylphorbol-l3-acetate (TPA)-induced membrane translocation of protein kinase C (PKC) isoforms, whereas both compounds decreased ATF2 phosphorylation by PKCε and ATF2 transcriptional activity. Overexpression of either constitutively active PKCε or phosphomimic mutant ATF2(T52E) attenuated the cellular effects of the compounds. CONCLUSION The imaging-based high-throughput screen provides a proof-of-concept for the identification of small molecules that block the oncogenic addiction to PKCε signaling by promoting ATF2 nuclear export, resulting in mitochondrial membrane leakage and melanoma cell death.
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Affiliation(s)
- Tal Varsano
- Signal Transduction Program, Sanford-Burnham Medical Research Institute, La Jolla, California 92037, USA
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63
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Soengas MS. Mitophagy or how to control the Jekyll and Hyde embedded in mitochondrial metabolism: implications for melanoma progression and drug resistance. Pigment Cell Melanoma Res 2012; 25:721-31. [DOI: 10.1111/pcmr.12021] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- María S. Soengas
- Melanoma Laboratory, Molecular Pathology Programme; Centro Nacional de Investigaciones Oncológicas (Spanish National Cancer Research Centre); Madrid; Spain
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64
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Abstract
The protein kinase C (PKC) family of serine/threonine protein kinases is a heterogeneous group of enzymes receiving and integrating signals involved in both normal melanocyte biology and melanoma pathology. Alterations in PKC enzyme expression and activation contribute to the malignant phenotype of melanoma in both oncogenic and tumor suppressive roles. Delineating the diverse and often context-dependent functions of PKC enzymes in melanocyte/melanoma biology is key to capitalize on these kinases as drug targets. This review summarizes several of the diverse functions of PKC in melanocyte and melanoma biology with a focus on PKC enzyme regulation and function.
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Affiliation(s)
- Mitchell F Denning
- Department of Pathology and the Oncology Institute, Loyola University Chicago, Maywood, IL, USA.
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65
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66
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Lau E, Ronai ZA. ATF2 - at the crossroad of nuclear and cytosolic functions. J Cell Sci 2012; 125:2815-24. [PMID: 22685333 DOI: 10.1242/jcs.095000] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
An increasing number of transcription factors have been shown to elicit oncogenic and tumor suppressor activities, depending on the tissue and cell context. Activating transcription factor 2 (ATF2; also known as cAMP-dependent transcription factor ATF-2) has oncogenic activities in melanoma and tumor suppressor activities in non-malignant skin tumors and breast cancer. Recent work has shown that the opposing functions of ATF2 are associated with its subcellular localization. In the nucleus, ATF2 contributes to global transcription and the DNA damage response, in addition to specific transcriptional activities that are related to cell development, proliferation and death. ATF2 can also translocate to the cytosol, primarily following exposure to severe genotoxic stress, where it impairs mitochondrial membrane potential and promotes mitochondrial-based cell death. Notably, phosphorylation of ATF2 by the epsilon isoform of protein kinase C (PKCε) is the master switch that controls its subcellular localization and function. Here, we summarize our current understanding of the regulation and function of ATF2 in both subcellular compartments. This mechanism of control of a non-genetically modified transcription factor represents a novel paradigm for 'oncogene addiction'.
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Affiliation(s)
- Eric Lau
- Signal Transduction Program, Sanford-Burnham Medical Research Institute, 10901 N. Torrey Pines Rd, La Jolla, CA 92130, USA.
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