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Le Sénéchal R, Keruzoré M, Quillévéré A, Loaëc N, Dinh VT, Reznichenko O, Guixens-Gallardo P, Corcos L, Teulade-Fichou MP, Granzhan A, Blondel M. Alternative splicing of BCL-x is controlled by RBM25 binding to a G-quadruplex in BCL-x pre-mRNA. Nucleic Acids Res 2023; 51:11239-11257. [PMID: 37811881 PMCID: PMC10639069 DOI: 10.1093/nar/gkad772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Revised: 08/05/2023] [Accepted: 09/09/2023] [Indexed: 10/10/2023] Open
Abstract
BCL-x is a master regulator of apoptosis whose pre-mRNA is alternatively spliced into either a long (canonical) anti-apoptotic Bcl-xL isoform, or a short (alternative) pro-apoptotic Bcl-xS isoform. The balance between these two antagonistic isoforms is tightly regulated and overexpression of Bcl-xL has been linked to resistance to chemotherapy in several cancers, whereas overexpression of Bcl-xS is associated to some forms of diabetes and cardiac disorders. The splicing factor RBM25 controls alternative splicing of BCL-x: its overexpression favours the production of Bcl-xS, whereas its downregulation has the opposite effect. Here we show that RBM25 directly and specifically binds to GQ-2, an RNA G-quadruplex (rG4) of BCL-x pre-mRNA that forms at the vicinity of the alternative 5' splice site leading to the alternative Bcl-xS isoform. This RBM25/rG4 interaction is crucial for the production of Bcl-xS and depends on the RE (arginine-glutamate-rich) motif of RBM25, thus defining a new type of rG4-interacting domain. PhenDC3, a benchmark G4 ligand, enhances the binding of RBM25 to the GQ-2 rG4 of BCL-x pre-mRNA, thereby promoting the alternative pro-apoptotic Bcl-xS isoform and triggering apoptosis. Furthermore, the screening of a combinatorial library of 90 putative G4 ligands led to the identification of two original compounds, PhenDH8 and PhenDH9, superior to PhenDC3 in promoting the Bcl-xS isoform and apoptosis. Thus, favouring the interaction between RBM25 and the GQ-2 rG4 of BCL-x pre-mRNA represents a relevant intervention point to re-sensitize cancer cells to chemotherapy.
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Affiliation(s)
- Ronan Le Sénéchal
- Univ Brest; Inserm UMR1078; Etablissement Français du Sang (EFS) Bretagne; CHRU Brest, Hôpital Morvan, Laboratoire de Génétique Moléculaire, 22 avenue Camille Desmoulins, F-29200 Brest, France
| | - Marc Keruzoré
- Univ Brest; Inserm UMR1078; Etablissement Français du Sang (EFS) Bretagne; CHRU Brest, Hôpital Morvan, Laboratoire de Génétique Moléculaire, 22 avenue Camille Desmoulins, F-29200 Brest, France
| | - Alicia Quillévéré
- Univ Brest; Inserm UMR1078; Etablissement Français du Sang (EFS) Bretagne; CHRU Brest, Hôpital Morvan, Laboratoire de Génétique Moléculaire, 22 avenue Camille Desmoulins, F-29200 Brest, France
| | - Nadège Loaëc
- Univ Brest; Inserm UMR1078; Etablissement Français du Sang (EFS) Bretagne; CHRU Brest, Hôpital Morvan, Laboratoire de Génétique Moléculaire, 22 avenue Camille Desmoulins, F-29200 Brest, France
| | - Van-Trang Dinh
- Univ Brest; Inserm UMR1078; Etablissement Français du Sang (EFS) Bretagne; CHRU Brest, Hôpital Morvan, Laboratoire de Génétique Moléculaire, 22 avenue Camille Desmoulins, F-29200 Brest, France
| | - Oksana Reznichenko
- Chemistry and Modelling for the Biology of Cancer (CMBC), CNRS UMR9187, Inserm U1196, Institut Curie, Université Paris Saclay, F-91405 Orsay, France
| | - Pedro Guixens-Gallardo
- Chemistry and Modelling for the Biology of Cancer (CMBC), CNRS UMR9187, Inserm U1196, Institut Curie, Université Paris Saclay, F-91405 Orsay, France
| | - Laurent Corcos
- Univ Brest; Inserm UMR1078; Etablissement Français du Sang (EFS) Bretagne; CHRU Brest, Hôpital Morvan, Laboratoire de Génétique Moléculaire, 22 avenue Camille Desmoulins, F-29200 Brest, France
| | - Marie-Paule Teulade-Fichou
- Chemistry and Modelling for the Biology of Cancer (CMBC), CNRS UMR9187, Inserm U1196, Institut Curie, Université Paris Saclay, F-91405 Orsay, France
| | - Anton Granzhan
- Chemistry and Modelling for the Biology of Cancer (CMBC), CNRS UMR9187, Inserm U1196, Institut Curie, Université Paris Saclay, F-91405 Orsay, France
| | - Marc Blondel
- Univ Brest; Inserm UMR1078; Etablissement Français du Sang (EFS) Bretagne; CHRU Brest, Hôpital Morvan, Laboratoire de Génétique Moléculaire, 22 avenue Camille Desmoulins, F-29200 Brest, France
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2
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Kong X, Patel NA, Chalfant CE, Cooper DR. Ceramide synthesis regulates biogenesis and packaging of exosomal MALAT1 from adipose derived stem cells, increases dermal fibroblast migration and mitochondrial function. Cell Commun Signal 2023; 21:221. [PMID: 37620957 PMCID: PMC10463839 DOI: 10.1186/s12964-022-00900-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Accepted: 05/17/2022] [Indexed: 08/26/2023] Open
Abstract
BACKGROUND The function of exosomes, small extracellular vesicles (sEV) secreted from human adipose-derived stem cells (ADSC), is becoming increasingly recognized as a means of transferring the regenerative power of stem cells to injured cells in wound healing. Exosomes are rich in ceramides and long noncoding RNA (lncRNA) like metastasis-associated lung adenocarcinoma transcript 1 (MALAT1). We identified putative ceramide responsive cis-elements (CRCE) in MALAT1. We hypothesized that CRCE respond to cellular ceramide levels to regulate sEV MALAT1 packaging. MALAT1 levels by many cells exceed those of protein coding genes and it's expression is equally high in exosomes. Ceramide also regulates exosome synthesis, however, the contents of exosome cargo via sphingomyelinase and ceramide synthase pathways has not been demonstrated. METHODS ADSC were treated with an inhibitor of sphingomyelinase, GW4869, and stimulators of ceramide synthesis, C2- and C6-short chain ceramides, prior to collection of conditioned media (CM). sEV were isolated from CM, and then used to treat human dermal fibroblast (HDF) cultures in cell migration scratch assays, and mitochondrial stress tests to evaluate oxygen consumption rates (OCR). RESULTS Inhibition of sphingomyelinase by treatment of ADSC with GW4869 lowered levels of MALAT1 in small EVs. Stimulation of ceramide synthesis using C2- and C6- ceramides increased cellular, EVs levels of MALAT1. The functional role of sEV MALAT1 was evaluated in HDF by applying EVs to HDF. Control sEV increased migration of HDF, and significantly increased ATP production, basal and maximal respiration OCR. sEV from GW4869-treated ADSC inhibited cell migration and maximal respiration. However, sEV from C2- and C6-treated cells, respectively, increased both functions but not significantly above control EV except for maximal respiration. sEV were exosomes except when ADSC were treated with GW4869 and C6-ceramide, then they were larger and considered microvesicles. CONCLUSIONS Ceramide synthesis regulates MALAT1 EV content. Sphingomyelinase inhibition blocked MALAT1 from being secreted from ADSC EVs. Our report is consistent with those of MALAT1 increasing cell migration and mitochondrial MALAT1 altering maximal respiration in cells. Since MALAT1 is important for exosome function, it stands that increased exosomal MALAT1 should be beneficial for wound healing as shown with these assays. Video Abstract.
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Affiliation(s)
- Xaioyuan Kong
- Department of Veterans Affairs, J.A. Haley Veterans Hospital, Research Service 151, Tampa, Fl 33711 USA
| | - Niketa A. Patel
- Department of Veterans Affairs, J.A. Haley Veterans Hospital, Research Service 151, Tampa, Fl 33711 USA
- Department of Molecular Medicine, Morsani College of Medicine, Tampa, USA
| | - Charles E. Chalfant
- Department of Veterans Affairs, J.A. Haley Veterans Hospital, Research Service 151, Tampa, Fl 33711 USA
- Department of Cellular Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, FL 33612 USA
| | - Denise R. Cooper
- Department of Veterans Affairs, J.A. Haley Veterans Hospital, Research Service 151, Tampa, Fl 33711 USA
- Department of Molecular Medicine, Morsani College of Medicine, Tampa, USA
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Manet E, Polvèche H, Mure F, Mrozek-Gorska P, Roisné-Hamelin F, Hammerschmidt W, Auboeuf D, Gruffat H. Modulation of alternative splicing during early infection of human primary B lymphocytes with Epstein-Barr virus (EBV): a novel function for the viral EBNA-LP protein. Nucleic Acids Res 2021; 49:10657-10676. [PMID: 34530456 PMCID: PMC8501971 DOI: 10.1093/nar/gkab787] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 08/27/2021] [Accepted: 09/01/2021] [Indexed: 12/29/2022] Open
Abstract
Epstein-Barr virus (EBV) is a human herpesvirus associated with human cancers worldwide. Ex vivo, the virus efficiently infects resting human B lymphocytes and induces their continuous proliferation. This process is accompanied by a global reprogramming of cellular gene transcription. However, very little is known on the impact of EBV infection on the regulation of alternative splicing, a pivotal mechanism that plays an essential role in cell fate determination and is often deregulated in cancer. In this study, we have developed a systematic time-resolved analysis of cellular mRNA splice variant expression during EBV infection of resting B lymphocytes. Our results reveal that major modifications of alternative splice variant expression appear as early as day 1 post-infection and suggest that splicing regulation provides—besides transcription—an additional mechanism of gene expression regulation at the onset of B cell activation and proliferation. We also report a role for the viral proteins, EBNA2 and EBNA-LP, in the modulation of specific alternative splicing events and reveal a previously unknown function for EBNA-LP—together with the RBM4 splicing factor—in the alternative splicing regulation of two important modulators of cell proliferation and apoptosis respectively, NUMB and BCL-X.
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Affiliation(s)
- Evelyne Manet
- CIRI, Centre International de Recherche en Infectiologie, RNA Expression in Viruses and Eukaryotes Group, Univ Lyon, Université Claude Bernard Lyon I, INSERM U1111, CNRS UMR5308, ENS Lyon, Lyon F-69007, France
| | | | - Fabrice Mure
- CIRI, Centre International de Recherche en Infectiologie, RNA Expression in Viruses and Eukaryotes Group, Univ Lyon, Université Claude Bernard Lyon I, INSERM U1111, CNRS UMR5308, ENS Lyon, Lyon F-69007, France
| | - Paulina Mrozek-Gorska
- Research Unit Gene Vectors, Helmholtz Zentrum München, German Research Center for Environmental Health and German Center for Infection Research, D-81377 Munich, Germany
| | - Florian Roisné-Hamelin
- CIRI, Centre International de Recherche en Infectiologie, RNA Expression in Viruses and Eukaryotes Group, Univ Lyon, Université Claude Bernard Lyon I, INSERM U1111, CNRS UMR5308, ENS Lyon, Lyon F-69007, France
| | - Wolfgang Hammerschmidt
- Research Unit Gene Vectors, Helmholtz Zentrum München, German Research Center for Environmental Health and German Center for Infection Research, D-81377 Munich, Germany
| | | | - Henri Gruffat
- CIRI, Centre International de Recherche en Infectiologie, RNA Expression in Viruses and Eukaryotes Group, Univ Lyon, Université Claude Bernard Lyon I, INSERM U1111, CNRS UMR5308, ENS Lyon, Lyon F-69007, France
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Dou Z, Zhao D, Chen X, Xu C, Jin X, Zhang X, Wang Y, Xie X, Li Q, Di C, Zhang H. Aberrant Bcl-x splicing in cancer: from molecular mechanism to therapeutic modulation. J Exp Clin Cancer Res 2021; 40:194. [PMID: 34118966 PMCID: PMC8196531 DOI: 10.1186/s13046-021-02001-w] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 05/30/2021] [Indexed: 12/13/2022] Open
Abstract
Bcl-x pre-mRNA splicing serves as a typical example to study the impact of alternative splicing in the modulation of cell death. Dysregulation of Bcl-x apoptotic isoforms caused by precarious equilibrium splicing is implicated in genesis and development of multiple human diseases, especially cancers. Exploring the mechanism of Bcl-x splicing and regulation has provided insight into the development of drugs that could contribute to sensitivity of cancer cells to death. On this basis, we review the multiple splicing patterns and structural characteristics of Bcl-x. Additionally, we outline the cis-regulatory elements, trans-acting factors as well as epigenetic modifications involved in the splicing regulation of Bcl-x. Furthermore, this review highlights aberrant splicing of Bcl-x involved in apoptosis evade, autophagy, metastasis, and therapy resistance of various cancer cells. Last, emphasis is given to the clinical role of targeting Bcl-x splicing correction in human cancer based on the splice-switching oligonucleotides, small molecular modulators and BH3 mimetics. Thus, it is highlighting significance of aberrant splicing isoforms of Bcl-x as targets for cancer therapy.
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Affiliation(s)
- Zhihui Dou
- Department of Heavy Ion Radiation Medicine, Bio-Medical Research Center, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, 730000, China
- Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou, 730000, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 101408, China
- School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing, 101408, China
| | - Dapeng Zhao
- Department of Heavy Ion Radiation Medicine, Bio-Medical Research Center, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, 730000, China
- Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou, 730000, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 101408, China
- School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing, 101408, China
| | - Xiaohua Chen
- Department of Heavy Ion Radiation Medicine, Bio-Medical Research Center, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, 730000, China
- Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou, 730000, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 101408, China
- School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing, 101408, China
| | - Caipeng Xu
- Department of Heavy Ion Radiation Medicine, Bio-Medical Research Center, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, 730000, China
- Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou, 730000, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 101408, China
- School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing, 101408, China
| | - Xiaodong Jin
- Department of Heavy Ion Radiation Medicine, Bio-Medical Research Center, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, 730000, China
- Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou, 730000, China
| | - Xuetian Zhang
- Department of Heavy Ion Radiation Medicine, Bio-Medical Research Center, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, 730000, China
- Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou, 730000, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 101408, China
- School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing, 101408, China
| | - Yupei Wang
- Medical Genetics Center of Gansu Maternal and Child Health Care Center, Lanzhou, 730000, China
| | - Xiaodong Xie
- School of Basic Medical Sciences, Lanzhou University, Lanzhou, 730000, China
| | - Qiang Li
- Department of Heavy Ion Radiation Medicine, Bio-Medical Research Center, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, 730000, China
- Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou, 730000, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 101408, China
- School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing, 101408, China
- Advanced Energy Science and Technology Guangdong Laboratory, Huizhou, 516029, China
| | - Cuixia Di
- Department of Heavy Ion Radiation Medicine, Bio-Medical Research Center, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, 730000, China.
- Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou, 730000, China.
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 101408, China.
- School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing, 101408, China.
- Advanced Energy Science and Technology Guangdong Laboratory, Huizhou, 516029, China.
| | - Hong Zhang
- Department of Heavy Ion Radiation Medicine, Bio-Medical Research Center, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, 730000, China.
- Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou, 730000, China.
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 101408, China.
- School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing, 101408, China.
- Advanced Energy Science and Technology Guangdong Laboratory, Huizhou, 516029, China.
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Stevens M, Oltean S. Modulation of the Apoptosis Gene Bcl-x Function Through Alternative Splicing. Front Genet 2019; 10:804. [PMID: 31552099 PMCID: PMC6743414 DOI: 10.3389/fgene.2019.00804] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Accepted: 07/31/2019] [Indexed: 01/09/2023] Open
Abstract
Apoptosis plays a vital role in cell homeostasis during development and disease. Bcl-x, a member of the Bcl-2 family of proteins, is a mitochondrial transmembrane protein that functions to regulate the intrinsic apoptosis pathway. An alternative splicing (AS) event in exon 2 of Bcl-x results in two isoforms of Bcl-x with antagonistic effects on cell survival: Bcl-xL (long isoform), which is anti-apoptotic, and Bcl-xS (short isoform), which is pro-apoptotic. Bcl-xL is the most abundant Bcl-x protein and functions to inhibit apoptosis by a number of different mechanisms including inhibition of Bax. In contrast, Bcl-xS can directly bind to and inhibit the anti-apoptotic Bcl-xL and Bcl-2 proteins, resulting in the release of the pro-apoptotic Bak. There are multiple splice factors and signaling pathways that influence the Bcl-xL/Bcl-xS splicing ratio, including serine/arginine-rich (SR) proteins, heterogeneous nuclear ribonucleoproteins (hnRNPs), transcription factors, and cytokines. Dysregulation of the AS of Bcl-x has been implicated in cancer and diabetes. In cancer, the upregulation of Bcl-xL expression in tumor cells can result in resistance to chemotherapeutic agents. On the other hand, dysregulation of Bcl-x AS to promote Bcl-xS expression has been shown to be detrimental to pancreatic β-cells in diabetes, resulting in β-cell apoptosis. Therefore, manipulation of the splice factor, transcription factor, and signaling pathways that modulate this splicing event is fast emerging as a therapeutic avenue in the treatment of cancer and diabetes.
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Affiliation(s)
- Megan Stevens
- Institute of Biomedical and Clinical Science, Medical School, College of Medicine and Health, University of Exeter, Exeter, United Kingdom
| | - Sebastian Oltean
- Institute of Biomedical and Clinical Science, Medical School, College of Medicine and Health, University of Exeter, Exeter, United Kingdom
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DeLigio JT, Stevens SC, Nazario-Muñoz GS, MacKnight HP, Doe KK, Chalfant CE, Park MA. Serine/Arginine-Rich Splicing Factor 3 Modulates the Alternative Splicing of Cytoplasmic Polyadenylation Element Binding Protein 2. Mol Cancer Res 2019; 17:1920-1930. [PMID: 31138601 PMCID: PMC6726571 DOI: 10.1158/1541-7786.mcr-18-1291] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 04/17/2019] [Accepted: 05/21/2019] [Indexed: 02/06/2023]
Abstract
Triple negative breast cancer (TNBC) has an unusually low 5-year survival rate linked to higher metastatic rates. Our laboratory recently delineated a role for the alternative RNA splicing (AS) of cytoplasmic polyadenylation element binding protein 2 (CPEB2), via inclusion/exclusion of exon 4, in the metastasis of TNBC. In these studies, the mechanism governing the inclusion/exclusion of exon 4 was examined. Specifically, the RNA trans-factor, SRSF3, was found to be explicitly associated with CPEB2 exon 4. A SRSF3 consensus sequence was identified in exon 4, and mutation of this sequence abolished the association of SRSF3. The expression of SRSF3 was upregulated in TNBC cells upon the acquisition of anoikis resistance correlating with a reduction in the CPEB2A/B ratio. Importantly, downregulation of SRSF3 in these cells by siRNA induced the exclusion of exon 4 in cells increasing the ratio of CPEB2A (exon 4 excluded) to CPEB2B (exon 4 included). Downregulation of SRSF3 also reversed the CPEB2A/B ratio of a wild-type CPEB2 exon 4 minigene and endogenous CPEB2 pre-mRNA, but not a mutant CPEB2 minigene with the SRSF3 RNA cis-element ablated. SRSF3 downregulation ablated the anoikis resistance of TNBC cells, which was "rescued" by ectopic expression of CPEB2B. Finally, analysis of The Cancer Genome Atlas database showed a positive relationship between SRSF3 expression and lower CPEB2A/B ratios in aggressive breast cancers. IMPLICATIONS: These findings demonstrate that SRSF3 modulates CPEB2 AS to induce the expression of the CPEB2B isoform that drives TNBC phenotypes correlating with aggressive human breast cancer. VISUAL OVERVIEW: http://mcr.aacrjournals.org/content/molcanres/17/9/1920/F1.large.jpg.
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Affiliation(s)
- James T DeLigio
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University (VCU), Richmond Virginia
| | - Shaun C Stevens
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, Florida
| | - Gina S Nazario-Muñoz
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, Florida
| | - H Patrick MacKnight
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University (VCU), Richmond Virginia
| | - Keli K Doe
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University (VCU), Richmond Virginia
| | - Charles E Chalfant
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University (VCU), Richmond Virginia.
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, Florida
- VCU Massey Cancer Center, Cancer Cell Signaling Program, VCU, Richmond Virginia
- Research Service, Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia
- VCU Institute of Molecular Medicine, Richmond, Virginia
- VCU Johnson Center for Critical Care and Pulmonary Research, Richmond, Virginia
- Research Service, James A. Haley Veterans Hospital, Tampa, Florida
- The Moffitt Cancer Center, Tampa, Florida
| | - Margaret A Park
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University (VCU), Richmond Virginia.
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, Florida
- VCU Massey Cancer Center, Cancer Cell Signaling Program, VCU, Richmond Virginia
- VCU Johnson Center for Critical Care and Pulmonary Research, Richmond, Virginia
- Research Service, James A. Haley Veterans Hospital, Tampa, Florida
- The Moffitt Cancer Center, Tampa, Florida
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7
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Lee CC, Chang WH, Chang YS, Yang JM, Chang CS, Hsu KC, Chen YT, Liu TY, Chen YC, Lin SY, Wu YC, Chang JG. Alternative splicing in human cancer cells is modulated by the amiloride derivative 3,5-diamino-6-chloro-N-(N-(2,6-dichlorobenzoyl)carbamimidoyl)pyrazine-2-carboxide. Mol Oncol 2019; 13:1744-1762. [PMID: 31152681 PMCID: PMC6670021 DOI: 10.1002/1878-0261.12524] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 04/30/2019] [Accepted: 05/30/2019] [Indexed: 12/11/2022] Open
Abstract
Alternative splicing (AS) is a process that enables the generation of multiple protein isoforms with different biological properties from a single mRNA. Cancer cells often use the maneuverability conferred by AS to produce proteins that contribute to growth and survival. In our previous studies, we identified that amiloride modulates AS in cancer cells. However, the effective concentration of amiloride required to modulate AS is too high for use in cancer treatment. In this study, we used computational algorithms to screen potential amiloride derivatives for their ability to regulate AS in cancer cells. We found that 3,5-diamino-6-chloro-N-(N-(2,6-dichlorobenzoyl)carbamimidoyl)pyrazine-2-carboxamide (BS008) can regulate AS of apoptotic gene transcripts, including HIPK3, SMAC, and BCL-X, at a lower concentration than amiloride. This splicing regulation involved various splicing factors, and it was accompanied by a change in the phosphorylation state of serine/arginine-rich proteins (SR proteins). RNA sequencing was performed to reveal that AS of many other apoptotic gene transcripts, such as AATF, ATM, AIFM1, NFKB1, and API5, was also modulated by BS008. In vivo experiments further indicated that treatment of tumor-bearing mice with BS008 resulted in a marked decrease in tumor size. BS008 also had inhibitory effects in vitro, either alone or in a synergistic combination with the cytotoxic chemotherapeutic agents sorafenib and nilotinib. BS008 enabled sorafenib dose reduction without compromising antitumor activity. These findings suggest that BS008 may possess therapeutic potential for cancer treatment.
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Affiliation(s)
- Chien-Chin Lee
- Epigenome Research Center, China Medical University Hospital, Taichung, Taiwan
| | - Wen-Hsin Chang
- Epigenome Research Center, China Medical University Hospital, Taichung, Taiwan.,Department of Primary Care Medicine, Taipei Medical University Hospital, Taiwan
| | - Ya-Sian Chang
- Epigenome Research Center, China Medical University Hospital, Taichung, Taiwan.,Department of Laboratory Medicine, China Medical University Hospital, Taichung, Taiwan.,Center for Precision Medicine, China Medical University Hospital, Taichung, Taiwan
| | - Jinn-Moon Yang
- TIGP-Bioinformatics, Institute of Information Science, Academia Sinica, Taipei, Taiwan.,Institute of Bioinformatics and Systems Biology, National Chiao Tung University, Hsinchu, Taiwan.,Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan
| | - Chih-Shiang Chang
- Graduate Institute of Pharmaceutical Chemistry, China Medical University, Taichung, Taiwan
| | - Kai-Cheng Hsu
- Graduate Institute of Cancer Molecular Biology and Drug Discovery, College of Medical Science and Technology, Taipei Medical University, Taiwan
| | - Yun-Ti Chen
- Institute of Bioinformatics and Systems Biology, National Chiao Tung University, Hsinchu, Taiwan
| | - Ting-Yuan Liu
- Department of Laboratory Medicine, China Medical University Hospital, Taichung, Taiwan
| | - Yu-Chia Chen
- Department of Laboratory Medicine, China Medical University Hospital, Taichung, Taiwan
| | - Shyr-Yi Lin
- Department of Primary Care Medicine, Taipei Medical University Hospital, Taiwan.,Department of General Medicine, School of Medicine, College of Medicine, Taipei Medical University, Taiwan.,TMU Research Center of Cancer Translational Medicine, Taipei Medical University, Taiwan
| | - Yang-Chang Wu
- Graduate Institute of Natural Products, Kaohsiung Medical University, Taiwan.,Research Center for Natural Products and Drug Development, Kaohsiung Medical University, Taiwan.,Department of Medical Research, Kaohsiung Medical University Hospital, Taiwan.,Chinese Medicine Research and Development Center, China Medical University Hospital, Taichung, Taiwan
| | - Jan-Gowth Chang
- Epigenome Research Center, China Medical University Hospital, Taichung, Taiwan.,Department of Primary Care Medicine, Taipei Medical University Hospital, Taiwan.,Department of Laboratory Medicine, China Medical University Hospital, Taichung, Taiwan
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8
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BCL-2 family isoforms in apoptosis and cancer. Cell Death Dis 2019; 10:177. [PMID: 30792387 PMCID: PMC6384907 DOI: 10.1038/s41419-019-1407-6] [Citation(s) in RCA: 366] [Impact Index Per Article: 73.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2018] [Revised: 12/17/2018] [Accepted: 01/29/2019] [Indexed: 12/17/2022]
Abstract
The BCl-2 family has long been identified for its role in apoptosis. Following the initial discovery of BCL-2 in the context of B-cell lymphoma in the 1980s, a number of homologous proteins have since been identified. The members of the Bcl-2 family are designated as such due to their BCL-2 homology (BH) domains and involvement in apoptosis regulation. The BH domains facilitate the family members’ interactions with each other and can indicate pro- or anti-apoptotic function. Traditionally, these proteins are categorised into one of the three subfamilies; anti-apoptotic, BH3-only (pro-apoptotic), and pore-forming or ‘executioner’ (pro-apoptotic) proteins. Each of the BH3-only or anti-apoptotic proteins has a distinct pattern of activation, localisation and response to cell death or survival stimuli. All of these can vary across cell or stress types, or developmental stage, and this can cause the delineation of the roles of BCL-2 family members. Added to this complexity is the presence of relatively uncharacterised isoforms of many of the BCL-2 family members. There is a gap in our knowledge regarding the function of BCL-2 family isoforms. BH domain status is not always predictive or indicative of protein function, and several other important sequences, which can contribute to apoptotic activity have been identified. While therapeutic strategies targeting the BCL-2 family are constantly under development, it is imperative that we understand the molecules, which we are attempting to target. This review, discusses our current knowledge of anti-apoptotic BCL-2 family isoforms. With significant improvements in the potential for splicing therapies, it is important that we begin to understand the distinctions of the BCL-2 family, not limited to just the mechanisms of apoptosis control, but in their roles outside of apoptosis.
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9
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Yosudjai J, Wongkham S, Jirawatnotai S, Kaewkong W. Aberrant mRNA splicing generates oncogenic RNA isoforms and contributes to the development and progression of cholangiocarcinoma. Biomed Rep 2019; 10:147-155. [PMID: 30906543 PMCID: PMC6403481 DOI: 10.3892/br.2019.1188] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 01/04/2019] [Indexed: 12/13/2022] Open
Abstract
Cholangiocarcinoma is a lethal biliary cancer, with an unclear molecular pathogenesis. Alternative splicing is a post-transcriptional modification that generates mature mRNAs, which are subsequently translated into proteins. Aberrant alternative splicing has been reported to serve a role in tumor initiation, maintenance and metastasis in several types of human cancer, including cholangiocarcinoma. In this review, the aberrant splicing of genes and the functional contributions of the spliced genes, in the carcinogenesis, progression and aggressiveness of cholangiocarcinoma are summarized. In addition, factors that influence this aberrant splicing that may be relevant as therapeutic targets or prognosis markers for cholangiocarcinoma are discussed.
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Affiliation(s)
- Juthamas Yosudjai
- Department of Biochemistry, Faculty of Medical Science, Naresuan University, Phitsanulok 65000, Thailand
| | - Sopit Wongkham
- Department of Biochemistry, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand
| | - Siwanon Jirawatnotai
- Siriraj Center for Research of Excellence (SiCORE) for System Pharmacology, Department of Pharmacology, Faculty of Medicine, Siriraj Medical School, Mahidol University, Bangkok 10700, Thailand
| | - Worasak Kaewkong
- Department of Biochemistry, Faculty of Medical Science, Naresuan University, Phitsanulok 65000, Thailand
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10
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Annalora AJ, O'Neil S, Bushman JD, Summerton JE, Marcus CB, Iversen PL. A k-mer based transcriptomics approach for antisense drug discovery targeting the Ewing's family of tumors. Oncotarget 2018; 9:30568-30586. [PMID: 30093970 PMCID: PMC6078127 DOI: 10.18632/oncotarget.25736] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 06/19/2018] [Indexed: 12/22/2022] Open
Abstract
Ewing’s sarcoma treatment failures are associated with high mortality indicating a need for new therapeutic approaches. We used a k-mer counting approach to identify cancer-specific mRNA transcripts in 3 Ewing’s Family Tumor (EFT) cell lines not found in the normal human transcriptome. Phosphorodiamidate morpholino oligomers targeting six EFT-specific transcripts were evaluated for cytotoxicity in TC-32 and CHLA-10 EFT lines and in HEK293 renal epithelial control cells. Average morpholino efficacy (EC50) was 0.66 ± 0.13 in TC-32, 0.25 ± 0.14 in CHLA-10 and 3.07 ± 5.02 µM in HEK293 control cells (ANOVA p < 0.01). Synergy was observed for a cocktail of 12 morpholinos at low dose (0.3 µM) in TC-32 cells, but not in CHLA-10 cells. Paired synergy was also observed in both EFT cell lines when the PHGDH pre-mRNA transcript was targeted in combination with XAGE1B or CYP4F22 transcripts. Antagonism was observed when CCND1 was targeted with XAGE1B or CYP4F22, or when IGFBP-2 was targeted with CCND1 or RBM11. This transcriptome profiling approach is highly effective for cancer drug discovery, as it identified new EWS-specific target genes (e.g. CYP4F22, RBM11 and IGBP-2), and predicted effective antisense agents (EC50 < 1 µM) that demonstrate both synergy and antagonism in combination therapy.
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Affiliation(s)
- Andrew J Annalora
- Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, OR 97331, USA
| | - Shawn O'Neil
- Center for Genome Research and Biocomputing, Oregon State University, Corvallis, OR 97331, USA
| | | | | | - Craig B Marcus
- Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, OR 97331, USA
| | - Patrick L Iversen
- Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, OR 97331, USA.,LS Pharma, LLC, Grand Junction, CO 81507, USA
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11
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Ceramide activates lysosomal cathepsin B and cathepsin D to attenuate autophagy and induces ER stress to suppress myeloid-derived suppressor cells. Oncotarget 2018; 7:83907-83925. [PMID: 27880732 PMCID: PMC5356634 DOI: 10.18632/oncotarget.13438] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Accepted: 11/07/2016] [Indexed: 12/31/2022] Open
Abstract
Myeloid-derived suppressor cells (MDSCs) are immune suppressive cells that are hallmarks of human cancer. MDSCs inhibit cytotoxic T lymphocytes (CTLs) and NK cell functions to promote tumor immune escape and progression, and therefore are considered key targets in cancer immunotherapy. Recent studies determined a key role of the apoptosis pathways in tumor-induced MDSC homeostasis and it is known that ceramide plays a key role in regulation of mammalian cell apoptosis. In this study, we aimed to determine the efficacy and underlying molecular mechanism of ceramide in suppression of MDSCs. Treatment of tumor-bearing mice with LCL521, a lysosomotropic inhibitor of acid ceramidase, significantly decreased MDSC accumulation in vivo. Using a MDSC-like myeloid cell model, we determined that LCL521 targets lysosomes and increases total cellular C16 ceramide level. Although MDSC-like cells have functional apoptosis pathways, LCL521-induced MDSC death occurs in an apoptosis- and necroptosis-independent mechanism. LCL521 treatment resulted in an increase in the number of autophagic vesicles, heterolysosomes and swollen ERs. Finally, concomitant inhibition of cathepsin B and cathepsin D was required to significantly decrease LCL521-induced cell death. Our observations indicate that LCL521 targets lysosomes to activate cathepsin B and cathepsin D, resulting in interrupted autophagy and ER stress that culminates in MDSC death. Therefore, a ceramidase inhibitor is potentially an effective adjunct therapeutic agent for suppression of MDSCs to enhance the efficacy of CTL-based cancer immunotherapy.
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12
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Shapiro BA, Vu NT, Shultz MD, Shultz JC, Mietla JA, Gouda MM, Yacoub A, Dent P, Fisher PB, Park MA, Chalfant CE. Melanoma Differentiation-associated Gene 7/IL-24 Exerts Cytotoxic Effects by Altering the Alternative Splicing of Bcl-x Pre-mRNA via the SRC/PKCδ Signaling Axis. J Biol Chem 2016; 291:21669-21681. [PMID: 27519412 DOI: 10.1074/jbc.m116.737569] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 08/02/2016] [Indexed: 11/06/2022] Open
Abstract
Melanoma differentiation-associated gene 7 (MDA-7/IL-24) exhibits cytotoxic effects on tumor cells while sparing untransformed cells, and Bcl-x(L) is reported to efficiently block the induction of cell death by MDA-7/IL-24. The expression of Bcl-x(L) is regulated at the level of RNA splicing via alternative 5' splice site selection within exon 2 to produce either the pro-apoptotic Bcl-x(s) or the anti-apoptotic Bcl-x(L). Our laboratory previously reported that Bcl-x RNA splicing is dysregulated in a large percentage of human non-small cell lung cancer (NSCLC) tumors. Therefore, we investigated whether the alternative RNA splicing of Bcl-x pre-mRNA was modulated by MDA-7/IL-24, which would suggest that specific NSCLC tumors are valid targets for this cytokine therapy. Adenovirus-delivered MDA-7/IL-24 (Ad.mda-7) reduced the viability of NSCLC cells of varying oncogenotypes, which was preceded by a decrease in the ratio of Bcl-x(L)/Bcl-x(s) mRNA and Bcl-x(L) protein expression. Importantly, both the expression of Bcl-x(L) and the loss of cell viability were "rescued" in Ad.mda-7-treated cells incubated with Bcl-x(s) siRNA. In addition, NSCLC cells ectopically expressing Bcl-x(s) exhibited significantly reduced Bcl-x(L) expression, which was again restored by Bcl-x(s) siRNA, suggesting the existence of a novel mechanism by which Bcl-x(s) mRNA restrains the expression of Bcl-x(L). In additional mechanistic studies, inhibition of SRC and PKCδ completely ablated the ability of MDA-7/IL-24 to reduce the Bcl-x(L)/(s) mRNA ratio and cell viability. These findings show that Bcl-x(s) expression is an important mediator of MDA-7/IL-24-induced cytotoxicity requiring the SRC/PKCδ signaling axis in NSCLC cells.
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Affiliation(s)
- Brian A Shapiro
- From the Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia 23249.,the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University-School of Medicine, Richmond, Virginia 23298-0614
| | - Ngoc T Vu
- the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University-School of Medicine, Richmond, Virginia 23298-0614
| | - Michael D Shultz
- From the Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia 23249
| | - Jacqueline C Shultz
- the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University-School of Medicine, Richmond, Virginia 23298-0614
| | - Jennifer A Mietla
- the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University-School of Medicine, Richmond, Virginia 23298-0614
| | - Mazen M Gouda
- the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University-School of Medicine, Richmond, Virginia 23298-0614
| | - Adly Yacoub
- the Department of Neurosurgery, Virginia Commonwealth University-School of Medicine, Richmond, Virginia 23298-0614
| | - Paul Dent
- the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University-School of Medicine, Richmond, Virginia 23298-0614.,the Virginia Commonwealth University Institute of Molecular Medicine, Richmond, Virginia 23298.,the Virginia Commonwealth University Massey Cancer Center, Richmond, Virginia 23298, and
| | - Paul B Fisher
- the Virginia Commonwealth University Institute of Molecular Medicine, Richmond, Virginia 23298, .,the Virginia Commonwealth University Massey Cancer Center, Richmond, Virginia 23298, and.,the Department of Human and Molecular Genetics, Virginia Commonwealth University-School of Medicine, Richmond, Virginia 23298
| | - Margaret A Park
- the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University-School of Medicine, Richmond, Virginia 23298-0614, .,the Virginia Commonwealth University Massey Cancer Center, Richmond, Virginia 23298, and
| | - Charles E Chalfant
- From the Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia 23249, .,the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University-School of Medicine, Richmond, Virginia 23298-0614.,the Virginia Commonwealth University Institute of Molecular Medicine, Richmond, Virginia 23298.,the Virginia Commonwealth University Massey Cancer Center, Richmond, Virginia 23298, and.,the Virginia Commonwealth University Johnson Center for Critical Care and Pulmonary Research, Richmond, Virginia 23298
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13
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De Maio FA, Risso G, Iglesias NG, Shah P, Pozzi B, Gebhard LG, Mammi P, Mancini E, Yanovsky MJ, Andino R, Krogan N, Srebrow A, Gamarnik AV. The Dengue Virus NS5 Protein Intrudes in the Cellular Spliceosome and Modulates Splicing. PLoS Pathog 2016; 12:e1005841. [PMID: 27575636 PMCID: PMC5004807 DOI: 10.1371/journal.ppat.1005841] [Citation(s) in RCA: 134] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 08/03/2016] [Indexed: 11/22/2022] Open
Abstract
Dengue virus NS5 protein plays multiple functions in the cytoplasm of infected cells, enabling viral RNA replication and counteracting host antiviral responses. Here, we demonstrate a novel function of NS5 in the nucleus where it interferes with cellular splicing. Using global proteomic analysis of infected cells together with functional studies, we found that NS5 binds spliceosome complexes and modulates endogenous splicing as well as minigene-derived alternative splicing patterns. In particular, we show that NS5 alone, or in the context of viral infection, interacts with core components of the U5 snRNP particle, CD2BP2 and DDX23, alters the inclusion/exclusion ratio of alternative splicing events, and changes mRNA isoform abundance of known antiviral factors. Interestingly, a genome wide transcriptome analysis, using recently developed bioinformatics tools, revealed an increase of intron retention upon dengue virus infection, and viral replication was improved by silencing specific U5 components. Different mechanistic studies indicate that binding of NS5 to the spliceosome reduces the efficiency of pre-mRNA processing, independently of NS5 enzymatic activities. We propose that NS5 binding to U5 snRNP proteins hijacks the splicing machinery resulting in a less restrictive environment for viral replication.
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Affiliation(s)
| | - Guillermo Risso
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE, UBA-CONICET), Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires
| | | | - Priya Shah
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, California, United States of America
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California, United States of America
| | - Berta Pozzi
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE, UBA-CONICET), Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires
| | | | - Pablo Mammi
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE, UBA-CONICET), Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires
| | | | | | - Raul Andino
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, California, United States of America
| | - Nevan Krogan
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California, United States of America
| | - Anabella Srebrow
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE, UBA-CONICET), Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires
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14
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Barbour SE, Nguyen PT, Park M, Emani B, Lei X, Kambalapalli M, Shultz JC, Wijesinghe D, Chalfant CE, Ramanadham S. Group VIA Phospholipase A2 (iPLA2β) Modulates Bcl-x 5'-Splice Site Selection and Suppresses Anti-apoptotic Bcl-x(L) in β-Cells. J Biol Chem 2015; 290:11021-31. [PMID: 25762722 DOI: 10.1074/jbc.m115.648956] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2015] [Indexed: 01/09/2023] Open
Abstract
Diabetes is a consequence of reduced β-cell function and mass, due to β-cell apoptosis. Endoplasmic reticulum (ER) stress is induced during β-cell apoptosis due to various stimuli, and our work indicates that group VIA phospholipase A2β (iPLA2β) participates in this process. Delineation of underlying mechanism(s) reveals that ER stress reduces the anti-apoptotic Bcl-x(L) protein in INS-1 cells. The Bcl-x pre-mRNA undergoes alternative pre-mRNA splicing to generate Bcl-x(L) or Bcl-x(S) mature mRNA. We show that both thapsigargin-induced and spontaneous ER stress are associated with reductions in the ratio of Bcl-x(L)/Bcl-x(S) mRNA in INS-1 and islet β-cells. However, chemical inactivation or knockdown of iPLA2β augments the Bcl-x(L)/Bcl-x(S) ratio. Furthermore, the ratio is lower in islets from islet-specific RIP-iPLA2β transgenic mice, whereas islets from global iPLA2β(-/-) mice exhibit the opposite phenotype. In view of our earlier reports that iPLA2β induces ceramide accumulation through neutral sphingomyelinase 2 and that ceramides shift the Bcl-x 5'-splice site (5'SS) selection in favor of Bcl-x(S), we investigated the potential link between Bcl-x splicing and the iPLA2β/ceramide axis. Exogenous C6-ceramide did not alter Bcl-x 5'SS selection in INS-1 cells, and neutral sphingomyelinase 2 inactivation only partially prevented the ER stress-induced shift in Bcl-x splicing. In contrast, 5(S)-hydroxytetraenoic acid augmented the ratio of Bcl-x(L)/Bcl-x(S) by 15.5-fold. Taken together, these data indicate that β-cell apoptosis is, in part, attributable to the modulation of 5'SS selection in the Bcl-x pre-mRNA by bioactive lipids modulated by iPLA2β.
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Affiliation(s)
- Suzanne E Barbour
- From the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia 23298-0614
| | - Phuong T Nguyen
- From the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia 23298-0614
| | - Margaret Park
- From the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia 23298-0614
| | - Bhargavi Emani
- From the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia 23298-0614
| | - Xiaoyong Lei
- the Department of Cell, Developmental, and Integrative Biology and Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Mamatha Kambalapalli
- From the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia 23298-0614
| | - Jacqueline C Shultz
- From the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia 23298-0614
| | - Dayanjan Wijesinghe
- From the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia 23298-0614, the Hunter Holmes McGuire Veterans Affairs Medical Center, Richmond, Virginia 23249
| | - Charles E Chalfant
- From the Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia 23298-0614, the Hunter Holmes McGuire Veterans Affairs Medical Center, Richmond, Virginia 23249, the Massey Cancer Center, Richmond, Virginia 23298, and the Virginia Commonwealth University Reanimation Engineering Science Center, Richmond, Virginia 23298
| | - Sasanka Ramanadham
- the Department of Cell, Developmental, and Integrative Biology and Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, Alabama 35294,
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15
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Chabot B. My road to alternative splicing control: from simple paths to loops and interconnections. Biochem Cell Biol 2015; 93:171-9. [PMID: 25759250 DOI: 10.1139/bcb-2014-0161] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
With the functional importance of alternative splicing being validated in nearly every mammalian biological system and implicated in many human diseases, it is now crucial to identify the molecular programs that control the production of splice variants. In this article, I will survey how our knowledge of the basic principles of alternative splicing control evolved over the last 25 years. I will also describe how investigation of the splicing control of an apoptotic regulator led us to identify novel effectors and revealed the existence of converging pathways linking splicing decisions to DNA damage. Finally, I will review how our efforts at developing tools designed to monitor and redirect splicing helped assess the impact of misregulated splicing in cancer.
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Affiliation(s)
- Benoit Chabot
- Department of Microbiology and Infectious Diseases, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC J1E 4K8, Canada
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16
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Bielli P, Bordi M, Di Biasio V, Sette C. Regulation of BCL-X splicing reveals a role for the polypyrimidine tract binding protein (PTBP1/hnRNP I) in alternative 5' splice site selection. Nucleic Acids Res 2014; 42:12070-81. [PMID: 25294838 PMCID: PMC4231771 DOI: 10.1093/nar/gku922] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Alternative splicing (AS) modulates many physiological and pathological processes. For instance, AS of the BCL-X gene balances cell survival and apoptosis in development and cancer. Herein, we identified the polypyrimidine tract binding protein (PTBP1) as a direct regulator of BCL-X AS. Overexpression of PTBP1 promotes selection of the distal 5' splice site in BCL-X exon 2, generating the pro-apoptotic BCL-Xs splice variant. Conversely, depletion of PTBP1 enhanced splicing of the anti-apoptotic BCL-XL variant. In vivo cross-linking experiments and site-directed mutagenesis restricted the PTBP1 binding site to a polypyrimidine tract located between the two alternative 5' splice sites. Binding of PTBP1 to this site was required for its effect on splicing. Notably, a similar function of PTBP1 in the selection of alternative 5' splice sites was confirmed using the USP5 gene as additional model. Mechanistically, PTBP1 displaces SRSF1 binding from the proximal 5' splice site, thus repressing its selection. Our study provides a novel mechanism of alternative 5' splice site selection by PTBP1 and indicates that the presence of a PTBP1 binding site between two alternative 5' splice sites promotes selection of the distal one, while repressing the proximal site by competing for binding of a positive regulator.
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Affiliation(s)
- Pamela Bielli
- Department of Biomedicine and Prevention, University of Rome Tor Vergata, 00133 Rome, Italy Laboratory of Neuroembryology, Fondazione Santa Lucia, 00143 Rome, Italy
| | - Matteo Bordi
- Department of Biomedicine and Prevention, University of Rome Tor Vergata, 00133 Rome, Italy Laboratory of Neuroembryology, Fondazione Santa Lucia, 00143 Rome, Italy
| | - Valentina Di Biasio
- Department of Biomedicine and Prevention, University of Rome Tor Vergata, 00133 Rome, Italy Laboratory of Neuroembryology, Fondazione Santa Lucia, 00143 Rome, Italy
| | - Claudio Sette
- Department of Biomedicine and Prevention, University of Rome Tor Vergata, 00133 Rome, Italy Laboratory of Neuroembryology, Fondazione Santa Lucia, 00143 Rome, Italy
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17
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DeOcesano-Pereira C, Amaral MS, Parreira KS, Ayupe AC, Jacysyn JF, Amarante-Mendes GP, Reis EM, Verjovski-Almeida S. Long non-coding RNA INXS is a critical mediator of BCL-XS induced apoptosis. Nucleic Acids Res 2014; 42:8343-55. [PMID: 24992962 PMCID: PMC4117780 DOI: 10.1093/nar/gku561] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
BCL-X mRNA alternative splicing generates pro-apoptotic BCL-XS or anti-apoptotic BCL-XL gene products and the mechanism that regulates splice shifting is incompletely understood. We identified and characterized a long non-coding RNA (lncRNA) named INXS, transcribed from the opposite genomic strand of BCL-X, that was 5- to 9-fold less abundant in tumor cell lines from kidney, liver, breast and prostate and in kidney tumor tissues compared with non-tumors. INXS is an unspliced 1903 nt-long RNA, is transcribed by RNA polymerase II, 5′-capped, nuclear enriched and binds Sam68 splicing-modulator. Three apoptosis-inducing agents increased INXS lncRNA endogenous expression in the 786-O kidney tumor cell line, increased BCL-XS/BCL-XL mRNA ratio and activated caspases 3, 7 and 9. These effects were abrogated in the presence of INXS knockdown. Similarly, ectopic INXS overexpression caused a shift in splicing toward BCL-XS and activation of caspases, thus leading to apoptosis. BCL-XS protein accumulation was detected upon INXS overexpression. In a mouse xenograft model, intra-tumor injections of an INXS-expressing plasmid caused a marked reduction in tumor weight, and an increase in BCL-XS isoform, as determined in the excised tumors. We revealed an endogenous lncRNA that induces apoptosis, suggesting that INXS is a possible target to be explored in cancer therapies.
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Affiliation(s)
- Carlos DeOcesano-Pereira
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, 05508-900 São Paulo, SP, Brasil
| | - Murilo S Amaral
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, 05508-900 São Paulo, SP, Brasil
| | - Kleber S Parreira
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, 05508-900 São Paulo, SP, Brasil
| | - Ana C Ayupe
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, 05508-900 São Paulo, SP, Brasil
| | - Jacqueline F Jacysyn
- Departamento de Imunologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, 05508-900 São Paulo, SP, Brasil
| | - Gustavo P Amarante-Mendes
- Departamento de Imunologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, 05508-900 São Paulo, SP, Brasil Instituto Nacional de Ciência e Tecnologia de Investigação em Imunologia, Universidade de São Paulo, 05508-900 São Paulo, SP, Brasil
| | - Eduardo M Reis
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, 05508-900 São Paulo, SP, Brasil Instituto Nacional de Ciência e Tecnologia em Oncogenômica, Universidade de São Paulo, 05508-900 São Paulo, SP, Brasil
| | - Sergio Verjovski-Almeida
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, 05508-900 São Paulo, SP, Brasil Instituto Nacional de Ciência e Tecnologia em Oncogenômica, Universidade de São Paulo, 05508-900 São Paulo, SP, Brasil
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18
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Naro C, Barbagallo F, Chieffi P, Bourgeois CF, Paronetto MP, Sette C. The centrosomal kinase NEK2 is a novel splicing factor kinase involved in cell survival. Nucleic Acids Res 2014; 42:3218-27. [PMID: 24369428 PMCID: PMC3950702 DOI: 10.1093/nar/gkt1307] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Revised: 11/14/2013] [Accepted: 11/25/2013] [Indexed: 12/12/2022] Open
Abstract
NEK2 is a serine/threonine kinase that promotes centrosome splitting and ensures correct chromosome segregation during the G2/M phase of the cell cycle, through phosphorylation of specific substrates. Aberrant expression and activity of NEK2 in cancer cells lead to dysregulation of the centrosome cycle and aneuploidy. Thus, a tight regulation of NEK2 function is needed during cell cycle progression. In this study, we found that NEK2 localizes in the nucleus of cancer cells derived from several tissues. In particular, NEK2 co-localizes in splicing speckles with SRSF1 and SRSF2. Moreover, NEK2 interacts with several splicing factors and phosphorylates some of them, including the oncogenic SRSF1 protein. Overexpression of NEK2 induces phosphorylation of endogenous SR proteins and affects the splicing activity of SRSF1 toward reporter minigenes and endogenous targets, independently of SRPK1. Conversely, knockdown of NEK2, like that of SRSF1, induces expression of pro-apoptotic variants from SRSF1-target genes and sensitizes cells to apoptosis. Our results identify NEK2 as a novel splicing factor kinase and suggest that part of its oncogenic activity may be ascribed to its ability to modulate alternative splicing, a key step in gene expression regulation that is frequently altered in cancer cells.
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Affiliation(s)
- Chiara Naro
- Department of Biomedicine and Prevention, University of Rome ‘Tor Vergata’, Rome, Italy, Laboratories of Neuroembryology and of Cellular and Molecular Neurobiology, Fondazione Santa Lucia IRCCS, 00143 Rome, Italy, Department of Psychology, II University of Naples, Caserta, Italy, Department of Functional Genomics and Cancer, Institut de Genetique et de Biologie Moleculaire et Cellulaire, F-67400, INSERM U964, F-67400 Illkirch, France and Department of Health Sciences, University of Rome Foro Italico, Rome, Italy
| | - Federica Barbagallo
- Department of Biomedicine and Prevention, University of Rome ‘Tor Vergata’, Rome, Italy, Laboratories of Neuroembryology and of Cellular and Molecular Neurobiology, Fondazione Santa Lucia IRCCS, 00143 Rome, Italy, Department of Psychology, II University of Naples, Caserta, Italy, Department of Functional Genomics and Cancer, Institut de Genetique et de Biologie Moleculaire et Cellulaire, F-67400, INSERM U964, F-67400 Illkirch, France and Department of Health Sciences, University of Rome Foro Italico, Rome, Italy
| | - Paolo Chieffi
- Department of Biomedicine and Prevention, University of Rome ‘Tor Vergata’, Rome, Italy, Laboratories of Neuroembryology and of Cellular and Molecular Neurobiology, Fondazione Santa Lucia IRCCS, 00143 Rome, Italy, Department of Psychology, II University of Naples, Caserta, Italy, Department of Functional Genomics and Cancer, Institut de Genetique et de Biologie Moleculaire et Cellulaire, F-67400, INSERM U964, F-67400 Illkirch, France and Department of Health Sciences, University of Rome Foro Italico, Rome, Italy
| | - Cyril F. Bourgeois
- Department of Biomedicine and Prevention, University of Rome ‘Tor Vergata’, Rome, Italy, Laboratories of Neuroembryology and of Cellular and Molecular Neurobiology, Fondazione Santa Lucia IRCCS, 00143 Rome, Italy, Department of Psychology, II University of Naples, Caserta, Italy, Department of Functional Genomics and Cancer, Institut de Genetique et de Biologie Moleculaire et Cellulaire, F-67400, INSERM U964, F-67400 Illkirch, France and Department of Health Sciences, University of Rome Foro Italico, Rome, Italy
| | - Maria Paola Paronetto
- Department of Biomedicine and Prevention, University of Rome ‘Tor Vergata’, Rome, Italy, Laboratories of Neuroembryology and of Cellular and Molecular Neurobiology, Fondazione Santa Lucia IRCCS, 00143 Rome, Italy, Department of Psychology, II University of Naples, Caserta, Italy, Department of Functional Genomics and Cancer, Institut de Genetique et de Biologie Moleculaire et Cellulaire, F-67400, INSERM U964, F-67400 Illkirch, France and Department of Health Sciences, University of Rome Foro Italico, Rome, Italy
| | - Claudio Sette
- Department of Biomedicine and Prevention, University of Rome ‘Tor Vergata’, Rome, Italy, Laboratories of Neuroembryology and of Cellular and Molecular Neurobiology, Fondazione Santa Lucia IRCCS, 00143 Rome, Italy, Department of Psychology, II University of Naples, Caserta, Italy, Department of Functional Genomics and Cancer, Institut de Genetique et de Biologie Moleculaire et Cellulaire, F-67400, INSERM U964, F-67400 Illkirch, France and Department of Health Sciences, University of Rome Foro Italico, Rome, Italy
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Risso G, Pelisch F, Pozzi B, Mammi P, Blaustein M, Colman-Lerner A, Srebrow A. Modification of Akt by SUMO conjugation regulates alternative splicing and cell cycle. Cell Cycle 2013; 12:3165-74. [PMID: 24013425 DOI: 10.4161/cc.26183] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Akt/PKB is a key signaling molecule in higher eukaryotes and a crucial protein kinase in human health and disease. Phosphorylation, acetylation, and ubiquitylation have been reported as important regulatory post-translational modifications of this kinase. We describe here that Akt is modified by SUMO conjugation, and show that lysine residues 276 and 301 are the major SUMO attachment sites within this protein. We found that phosphorylation and SUMOylation of Akt appear as independent events. However, decreasing Akt SUMOylation levels severely affects the role of this kinase as a regulator of fibronectin and Bcl-x alternative splicing. Moreover, we observed that the Akt mutant (Akt E17K) found in several human tumors displays increased levels of SUMOylation and also an enhanced capacity to regulate fibronectin splicing patterns. This splicing regulatory activity is completely abolished by decreasing Akt E17K SUMO conjugation levels. Additionally, we found that SUMOylation controls Akt regulatory function at G₁/S transition during cell cycle progression. These findings reveal SUMO conjugation as a novel level of regulation for Akt activity, opening new areas of exploration related to the molecular mechanisms involved in the diverse cellular functions of this kinase.
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Affiliation(s)
- Guillermo Risso
- Instituto de Fisiología, Biología Molecular y Neurociencias-Consejo Nacional de Investigaciones Científicas y Técnicas; Departamento de Fisiología, Biología Molecular y Celular; Facultad de Ciencias Exactas y Naturales-Universidad de Buenos Aires; Buenos Aires, Argentina
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20
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Ruirui K, Ray P, Yang M, Wen P, Zhu L, Liu J, Fushimi K, Kar A, Liu Y, He R, Kuo D, Wu JY. Alternative Pre-mRNA Splicing, Cell Death, and Cancer. Cancer Treat Res 2013; 158:181-212. [PMID: 24222359 DOI: 10.1007/978-3-642-31659-3_8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Alternative splicing is one of the most powerful mechanisms for generating functionally distinct products from a single genetic loci and for fine-tuning gene activities at the post-transcriptional level. Alternative splicing plays important roles in regulating genes critical for cell death. These cell death genes encode death ligands, cell surface death receptors, intracellular death regulators, signal transduction molecules, and death executor enzymes such as caspases and nucleases. Alternative splicing of these genes often leads to the formation of functionally different products, some of which have antagonistic effects that are either cell death-promoting or cell death-preventing. Differential alternative splicing can affect expression, subcellular distribution, and functional activities of the gene products. Molecular defects in splicing regulation of cell death genes have been associated with cancer development and resistance to treatment. Studies using molecular, biochemical, and systems-based approaches have begun to reveal mechanisms underlying the regulation of alternative splicing of cell death genes. Systematic studies have begun to uncover the multi-level interconnected networks that regulate alternative splicing. A global picture of the complex mechanisms that regulate cell death genes at the pre-mRNA splicing level has thus begun to emerge.
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Affiliation(s)
- Kong Ruirui
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Science, Beijing, China
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21
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Abstract
For most of our 25,000 genes, the removal of introns by pre-messenger RNA (pre-mRNA) splicing represents an essential step toward the production of functional messenger RNAs (mRNAs). Alternative splicing of a single pre-mRNA results in the production of different mRNAs. Although complex organisms use alternative splicing to expand protein function and phenotypic diversity, patterns of alternative splicing are often altered in cancer cells. Alternative splicing contributes to tumorigenesis by producing splice isoforms that can stimulate cell proliferation and cell migration or induce resistance to apoptosis and anticancer agents. Cancer-specific changes in splicing profiles can occur through mutations that are affecting splice sites and splicing control elements, and also by alterations in the expression of proteins that control splicing decisions. Recent progress in global approaches that interrogate splicing diversity should help to obtain specific splicing signatures for cancer types. The development of innovative approaches for annotating and reprogramming splicing events will more fully establish the essential contribution of alternative splicing to the biology of cancer and will hopefully provide novel targets and anticancer strategies. Metazoan genes are usually made up of several exons interrupted by introns. The introns are removed from the pre-mRNA by RNA splicing. In conjunction with other maturation steps, such as capping and polyadenylation, the spliced mRNA is then transported to the cytoplasm to be translated into a functional protein. The basic mechanism of splicing requires accurate recognition of each extremity of each intron by the spliceosome. Introns are identified by the binding of U1 snRNP to the 5' splice site and the U2AF65/U2AF35 complex to the 3' splice site. Following these interactions, other proteins and snRNPs are recruited to generate the complete spliceosomal complex needed to excise the intron. While many introns are constitutively removed by the spliceosome, other splice junctions are not used systematically, generating the phenomenon of alternative splicing. Alternative splicing is therefore the process by which a single species of pre-mRNA can be matured to produce different mRNA molecules (Fig. 1). Depending on the number and types of alternative splicing events, a pre-mRNA can generate from two to several thousands different mRNAs leading to the production of a corresponding number of proteins. It is now believed that the expression of at least 70 % of human genes is subjected to alternative splicing, implying an enormous contribution to proteomic diversity, and by extension, to the development and the evolution of complex animals. Defects in splicing have been associated with human diseases (Caceres and Kornblihtt, Trends Genet 18(4):186-93, 2002, Cartegni et al., Nat Rev Genet 3(4):285-98, 2002, Pagani and Baralle, Nat Rev Genet 5(5):389-96, 2004), including cancer (Brinkman, Clin Biochem 37(7):584-94, 2004, Venables, Bioessays 28(4):378-86, 2006, Srebrow and Kornblihtt, J Cell Sci 119(Pt 13):2635-2641, 2006, Revil et al., Bull Cancer 93(9):909-919, 2006, Venables, Transworld Res Network, 2006, Pajares et al., Lancet Oncol 8(4):349-57, 2007, Skotheim and Nees, Int J Biochem Cell Biol 39:1432-1449, 2007). Numerous studies have now confirmed the existence of specific differences in the alternative splicing profiles between normal and cancer tissues. Although there are a few cases where specific mutations are the primary cause for these changes, global alterations in alternative splicing in cancer cells may be primarily derived from changes in the expression of RNA-binding proteins that control splice site selection. Overall, these cancer-specific differences in alternative splicing offer an immense potential to improve the diagnosis and the prognosis of cancer. This review will focus on the functional impact of cancer-associated alternative splicing variants, the molecular determinants that alter the splicing decisions in cancer cells, and future therapeutic strategies.
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Abstract
The bcl-x gene appears to play a critical role in regulating apoptosis in the developing and mature CNS and following CNS injury. Two isoforms of Bcl-x are produced as a result of alternative pre-mRNA splicing: Bcl-x(L) (the long form) is anti-apoptotic, while Bcl-x(S) (short form) is pro-apoptotic. Despite the antagonistic activities of these two isoforms, little is known about how regulation of alternative splicing of bcl-x may mediate neural cell apoptosis. Here, we report that apoptotic stimuli (staurosporine or C2-ceramide) reciprocally altered Bcl-x splicing in neural cells, decreasing Bcl-x(L) while increasing Bcl-x(S). Specific knockdown of Bcl-x(S) attenuated apoptosis. To further define regulatory elements that influenced Bcl-x splicing, a Bcl-x minigene was constructed. Deletional analysis revealed several consensus sequences within intron 2 that altered splicing. We found that the splicing factor, CUG-binding-protein-1 (CUGBP1), bound to a consensus sequence close to the Bcl-x(L) 5' splice site, altering the Bcl-x(L)/Bcl-x(S) ratio and influencing cell death. In vivo, neonatal hypoxia-ischemia reciprocally altered Bcl-x pre-mRNA splicing, similar to the in vitro studies. Manipulation of the splice isoforms using viral gene transfer of Bcl-x(S) shRNA into the hippocampus of rats before neonatal hypoxia-ischemia decreased vulnerability to injury. Moreover, alterations in nuclear CUGBP1 preceded Bcl-x splicing changes. These results suggest that alternative pre-mRNA splicing may be an important regulatory mechanism for cell death after acute neurological injury and may potentially provide novel targets for intervention.
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23
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Shultz JC, Vu N, Shultz MD, Mba MUU, Shapiro BA, Chalfant CE. The Proto-oncogene PKCι regulates the alternative splicing of Bcl-x pre-mRNA. Mol Cancer Res 2012; 10:660-9. [PMID: 22522453 DOI: 10.1158/1541-7786.mcr-11-0363] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Two splice variants derived from the Bcl-x gene via alternative 5' splice site selection (5'SS) are proapoptotic Bcl-x(s) and antiapoptotic Bcl-x(L). Previously, our laboratory showed that apoptotic signaling pathways regulated the alternative 5'SS selection via protein phosphatase-1 and de novo ceramide. In this study, we examined the elusive prosurvival signaling pathways that regulate the 5'SS selection of Bcl-x pre-mRNA in cancer cells. Taking a broad-based approach by using a number of small-molecule inhibitors of various mitogenic/survival pathways, we found that only treatment of non-small cell lung cancer (NSCLC) cell lines with the phosphoinositide 3-kinase (PI3K) inhibitor LY294002 (50 μmol/L) or the pan-protein kinase C (PKC) inhibitor Gö6983 (25 μmol/L) decreased the Bcl-x(L)/(s) mRNA ratio. Pan-PKC inhibitors that did not target the atypical PKCs, PKCι and PKCζ, had no effect on the Bcl-x(L)/(s) mRNA ratio. Additional studies showed that downregulation of the proto-oncogene, PKCι, in contrast to PKCζ, also resulted in a decrease in the Bcl-x(L)/(s) mRNA ratio. Furthermore, downregulation of PKCι correlated with a dramatic decrease in the expression of SAP155, an RNA trans-acting factor that regulates the 5'SS selection of Bcl-x pre-mRNA. Inhibition of the PI3K or atypical PKC pathway induced a dramatic loss of SAP155 complex formation at ceramide-responsive RNA cis-element 1. Finally, forced expression of Bcl-x(L) "rescued" the loss of cell survival induced by PKCι siRNA. In summary, the PI3K/PKCι regulates the alternative splicing of Bcl-x pre-mRNA with implications in the cell survival of NSCLC cells.
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Affiliation(s)
- Jacqueline C Shultz
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University-School of Medicine, Room 2-016, Sanger Hall, 1101 East Marshall Street, P.O. Box 980614, Richmond, VA 23298, USA
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24
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Apostolatos A, Song S, Acosta S, Peart M, Watson JE, Bickford P, Cooper DR, Patel NA. Insulin promotes neuronal survival via the alternatively spliced protein kinase CδII isoform. J Biol Chem 2012; 287:9299-310. [PMID: 22275369 DOI: 10.1074/jbc.m111.313080] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Insulin signaling pathways in the brain regulate food uptake and memory and learning. Insulin and protein kinase C (PKC) pathways are integrated and function closely together. PKC activation in the brain is essential for learning and neuronal repair. Intranasal delivery of insulin to the central nervous system (CNS) has been shown to improve memory, reduce cerebral atrophy, and reverse neurodegeneration. However, the neuronal molecular mechanisms of these effects have not been studied in depth. PKCδ plays a central role in cell survival. Its splice variants, PKCδI and PKCδII, are switches that determine cell survival and fate. PKCδI promotes apoptosis, whereas PKCδII promotes survival. Here, we demonstrate that insulin promotes alternative splicing of PKCδII isoform in HT22 cells. The expression of PKCδI splice variant remains unchanged. Insulin increases PKCδII alternative splicing via the PI3K pathway. We further demonstrate that Akt kinase mediates phosphorylation of the splicing factor SC35 to promote PKCδII alternative splicing. Using overexpression and knockdown assays, we demonstrate that insulin increases expression of Bcl2 and bcl-xL via PKCδII. We demonstrate increased cell proliferation and increased BrdU incorporation in insulin-treated cells as well as in HT22 cells overexpressing PKCδII. Finally, we demonstrate in vivo that intranasal insulin promotes cognitive function in mice with concomitant increases in PKCδII expression in the hippocampus. This is the first report of insulin, generally considered a growth or metabolic hormone, regulating the alternative isoform expression of a key signaling kinase in neuronal cells such that it results in increased neuronal survival.
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Affiliation(s)
- André Apostolatos
- Department of Molecular Medicine, University of South Florida, Tampa, Florida 33612, USA
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25
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Leu S, Lin YM, Wu CH, Ouyang P. Loss of Pnn expression results in mouse early embryonic lethality and cellular apoptosis through SRSF1-mediated alternative expression of Bcl-xS and ICA**. J Cell Sci 2012; 125:3164-72. [DOI: 10.1242/jcs.100859] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Pinin (Pnn), a serine/arginine-rich (SR)-related protein, has been shown to play multiple roles within eukaryotic cells including in cell-cell adhesion, cell migration, regulation of gene transcription, mRNA export, and alternative splicing. In this study, an attempt to generate mice homozygously deficient in Pnn failed due to early embryonic lethality. To evaluate the effects of loss of Pnn expression on cell survival, RNA interference experiments were performed in MCF-7 cells. With Pnn-depletion, cellular apoptosis and nuclear condensation were observed. In addition, nuclear speckles were disrupted, and expression levels of SR proteins were diminished. RT-PCR analysis showed that alternative splicing patterns of SRSF1 as well as of apoptosis-related genes Bcl-x and ICAD were altered and expression levels of Bim isoforms were modulated in Pnn-depleted cells. Cellular apoptosis induced by Pnn depletion was rescued by overexpression of SRSF1 which also restored generation of Bcl-xL and functionless ICAD. Pnn expression is, therefore, essential for survival of mouse embryos and the breast carcinoma cell line MCF-7. Moreover, Pnn-depletion, modulated by SRSF1, determines cellular apoptosis through activation of expression of pro-apoptotic Bcl-xS transcripts.
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26
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Sumanasekera C, Kelemen O, Beullens M, Aubol BE, Adams JA, Sunkara M, Morris A, Bollen M, Andreadis A, Stamm S. C6 pyridinium ceramide influences alternative pre-mRNA splicing by inhibiting protein phosphatase-1. Nucleic Acids Res 2011; 40:4025-39. [PMID: 22210893 PMCID: PMC3351148 DOI: 10.1093/nar/gkr1289] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Alternative pre-mRNA processing is a central element of eukaryotic gene regulation. The cell frequently alters the use of alternative exons in response to physiological stimuli. Ceramides are lipid-signaling molecules composed of sphingosine and a fatty acid. Previously, water-insoluble ceramides were shown to change alternative splicing and decrease SR-protein phosphorylation by activating protein phosphatase-1 (PP1). To gain further mechanistical insight into ceramide-mediated alternative splicing, we analyzed the effect of C6 pyridinium ceramide (PyrCer) on alternative splice site selection. PyrCer is a water-soluble ceramide analog that is under investigation as a cancer drug. We found that PyrCer binds to the PP1 catalytic subunit and inhibits the dephosphorylation of several splicing regulatory proteins containing the evolutionarily conserved RVxF PP1-binding motif (including PSF/SFPQ, Tra2-beta1 and SF2/ASF). In contrast to natural ceramides, PyrCer promotes phosphorylation of splicing factors. Exons that are regulated by PyrCer have in common suboptimal splice sites, are unusually short and share two 4-nt motifs, GAAR and CAAG. They are dependent on PSF/SFPQ, whose phosphorylation is regulated by PyrCer. Our results indicate that lipids can influence pre-mRNA processing by regulating the phosphorylation status of specific regulatory factors, which is mediated by protein phosphatase activity.
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Affiliation(s)
- Chiranthani Sumanasekera
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky 40536, USA
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27
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Proteins associated with the exon junction complex also control the alternative splicing of apoptotic regulators. Mol Cell Biol 2011; 32:954-67. [PMID: 22203037 DOI: 10.1128/mcb.06130-11] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Several apoptotic regulators, including Bcl-x, are alternatively spliced to produce isoforms with opposite functions. We have used an RNA interference strategy to map the regulatory landscape controlling the expression of the Bcl-x splice variants in human cells. Depleting proteins known as core (Y14 and eIF4A3) or auxiliary (RNPS1, Acinus, and SAP18) components of the exon junction complex (EJC) improved the production of the proapoptotic Bcl-x(S) splice variant. This effect was not seen when we depleted EJC proteins that typically participate in mRNA export (UAP56, Aly/Ref, and TAP) or that associate with the EJC to enforce nonsense-mediated RNA decay (MNL51, Upf1, Upf2, and Upf3b). Core and auxiliary EJC components modulated Bcl-x splicing through different cis-acting elements, further suggesting that this activity is distinct from the established EJC function. In support of a direct role in splicing control, recombinant eIF4A3, Y14, and Magoh proteins associated preferentially with the endogenous Bcl-x pre-mRNA, interacted with a model Bcl-x pre-mRNA in early splicing complexes, and specifically shifted Bcl-x alternative splicing in nuclear extracts. Finally, the depletion of Y14, eIF4A3, RNPS1, SAP18, and Acinus also encouraged the production of other proapoptotic splice variants, suggesting that EJC-associated components are important regulators of apoptosis acting at the alternative splicing level.
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28
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Lamour NF, Wijesinghe DS, Mietla JA, Ward KE, Stahelin RV, Chalfant CE. Ceramide kinase regulates the production of tumor necrosis factor α (TNFα) via inhibition of TNFα-converting enzyme. J Biol Chem 2011; 286:42808-17. [PMID: 22009748 PMCID: PMC3234830 DOI: 10.1074/jbc.m111.310169] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Tumor necrosis factor α (TNFα) is a well known cytokine involved in systemic and acute inflammation. In this study, we demonstrate that ceramide 1-phosphate (C1P) produced by ceramide kinase (CERK) is a negative regulator of LPS-induced TNFα secretion. Specifically, bone marrow-derived macrophages isolated from CERK knock-out mice (CERK−/−) generated higher levels of TNFα than the wild-type mice (CERK+/+) in response to LPS. An increase in basal TNFα secretion was also observed in CERK−/− murine embryonic fibroblasts, which was rescued by re-expression of wild-type CERK. This effect was due to increased secretion and not transcription. The secretion of TNFα is regulated by TNFα-converting enzyme (TACE also known as ADAM17), and importantly, the activity of TACE was higher in cell extracts from CERK−/− as compared with wild type. In vitro analysis also demonstrated that C1P is a potent inhibitor of this enzyme, in stark contrast to ceramide and sphingosine 1-phosphate. Furthermore, TACE specifically bound C1P with high affinity. Finally, several putative C1P-binding sites were identified via homology throughout the protein sequence of TACE. These results indicate that C1P produced by CERK has a negative effect on the processing/secretion of TNFα via modulation of TACE activity.
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Affiliation(s)
- Nadia F Lamour
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia 23298, USA
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29
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Shultz JC, Goehe RW, Wijesinghe DS, Murudkar C, Hawkins AJ, Shay JW, Minna JD, Chalfant CE. Alternative splicing of caspase 9 is modulated by the phosphoinositide 3-kinase/Akt pathway via phosphorylation of SRp30a. Cancer Res 2010; 70:9185-96. [PMID: 21045158 DOI: 10.1158/0008-5472.can-10-1545] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Increasing evidence points to the functional importance of alternative splice variations in cancer pathophysiology. Two splice variants are derived from the CASP9 gene via the inclusion (Casp9a) or exclusion (Casp9b) of a four-exon cassette. Here we show that alternative splicing of Casp9 is dysregulated in non-small cell lung cancers (NSCLC) regardless of their pathologic classification. Based on these findings we hypothesized that survival pathways activated by oncogenic mutation regulated this mechanism. In contrast to K-RasV12 expression, epidermal growth factor receptor (EGFR) overexpression or mutation dramatically lowered the Casp9a/9b splice isoform ratio. Moreover, Casp9b downregulation blocked the ability of EGFR mutations to induce anchorage-independent growth. Furthermore, Casp9b expression blocked inhibition of clonogenic colony formation by erlotinib. Interrogation of oncogenic signaling pathways showed that inhibition of phosphoinositide 3-kinase or Akt dramatically increased the Casp9a/9b ratio in NSCLC cells. Finally, Akt was found to mediate exclusion of the exon 3,4,5,6 cassette of Casp9 via the phosphorylation state of the RNA splicing factor SRp30a via serines 199, 201, 227, and 234. Taken together, our findings show that oncogenic factors activating the phosphoinositide 3-kinase/Akt pathway can regulate alternative splicing of Casp9 via a coordinated mechanism involving the phosphorylation of SRp30a.
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Affiliation(s)
- Jacqueline C Shultz
- Department of Biochemistry, Virginia Commonwealth University, VAMC, and Massey Cancer Center, Richmond, Virginia 23298, USA
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Berasain C, Goñi S, Castillo J, Latasa MU, Prieto J, Ávila MA. Impairment of pre-mRNA splicing in liver disease: Mechanisms and consequences. World J Gastroenterol 2010; 16:3091-102. [PMID: 20593494 PMCID: PMC2896746 DOI: 10.3748/wjg.v16.i25.3091] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Pre-mRNA splicing is an essential step in the process of gene expression in eukaryotes and consists of the removal of introns and the linking of exons to generate mature mRNAs. This is a highly regulated mechanism that allows the alternative usage of exons, the retention of intronic sequences and the generation of exonic sequences of variable length. Most human genes undergo splicing events, and disruptions of this process have been associated with a variety of diseases, including cancer. Hepatocellular carcinoma (HCC) is a molecularly heterogeneous type of tumor that usually develops in a cirrhotic liver. Alterations in pre-mRNA splicing of some genes have been observed in liver cancer, and although still scarce, the available data suggest that splicing defects may have a role in hepatocarcinogenesis. Here we briefly review the general mechanisms that regulate pre-mRNA splicing, and discuss some examples that illustrate how this process is impaired in liver tumorigenesis, and may contribute to HCC development. We believe that a more thorough examination of pre-mRNA splicing is still needed to accurately draw the molecular portrait of liver cancer. This will surely contribute to a better understanding of the disease and to the development of new effective therapies.
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31
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Alternative splicing modulates autoinhibition and SH3 accessibility in the Src kinase Fyn. Mol Cell Biol 2009; 29:6438-48. [PMID: 19805512 DOI: 10.1128/mcb.00398-09] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Src family kinases are central regulators of a large number of signaling pathways. To adapt to the idiosyncrasies of different cell types, these kinases may need a fine-tuning of their intrinsic molecular control mechanisms. Here, we describe on a molecular level how the Fyn kinase uses alternative splicing to adapt to different cellular environments. Using structural analysis, site-directed mutagenesis, and functional analysis, we show how the inclusion of either exon 7A or 7B affects the autoinhibition of Fyn and how this changes the SH3-dependent interaction and tyrosine phosphorylation of Sam68, with functional consequences for the Sam68-regulated survival of epithelial cells. Our results illustrate a novel mechanism of evolution that may contribute to the complexity of Src kinase regulation.
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32
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Fan D, Bitterman PB, Larsson O. Regulatory element identification in subsets of transcripts: comparison and integration of current computational methods. RNA (NEW YORK, N.Y.) 2009; 15:1469-82. [PMID: 19553345 PMCID: PMC2714745 DOI: 10.1261/rna.1617009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2009] [Accepted: 05/20/2009] [Indexed: 05/20/2023]
Abstract
Regulatory elements in mRNA play an often pivotal role in post-transcriptional regulation of gene expression. However, a systematic approach to efficiently identify putative regulatory elements from sets of post-transcriptionally coregulated genes is lacking, hampering studies of coregulation mechanisms. Although there are several analytical methods that can be used to detect conserved mRNA regulatory elements in a set of transcripts, there has been no systematic study of how well any of these methods perform individually or as a group. We therefore compared how well three algorithms, each based on a different principle (enumeration, optimization, or structure/sequence profiles), can identify elements in unaligned untranslated sequence regions. Two algorithms were originally designed to detect transcription factor binding sites, Weeder and BioProspector; and one was designed to detect RNA elements conserved in structure, RNAProfile. Three types of elements were examined: (1) elements conserved in both primary sequence and secondary structure; (2) elements conserved only in primary sequence; and (3) microRNA targets. Our results indicate that all methods can uniquely identify certain known RNA elements, and therefore, integrating the output from all algorithms leads to the most complete identification of elements. We therefore developed an approach to integrate results and guide selection of candidate elements from several algorithms presented as a web service (https://dbw.msi.umn.edu:8443/recit). These findings together with the approach for integration can be used to identify candidate elements from genome-wide post-transcriptional profiling data sets.
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Affiliation(s)
- Danhua Fan
- Department of Medicine, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Jiang L, Yang HS, Wang Z, Zhou Y, Zhou M, Zeng X, Chen QM. ORAOV1-A correlates with poor differentiation in oral cancer. J Dent Res 2009; 88:433-8. [PMID: 19493886 DOI: 10.1177/0022034509336994] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Oral cancer overexpressed 1 (ORAOV1) is a crucial oncogene in oral squamous cell carcinoma (OSCC). In this study, we have identified a novel splice variant of ORAOV1, designated as ORAOV1-A. To study the potential role of ORAOV1-A in OSCC, we tested its expression in 7 OSCC cell lines, as well as in 19 normal oral tissue samples and 47 OSCC tissue samples. The expression of ORAOV1-A was detectable in 6 out of 7 OSCC cell lines tested. In OSCC tissue samples, the expression frequency of ORAOV1-A (51.1%) was much higher than that in normal samples (10.5%). Notably, an inverse correlation was found between the expression frequency of ORAOV1-A and the degree of differentiation in OSCC (P = 0.0017). In conclusion, our results suggested that ORAOV1-A may play a functional role in the tumorigenesis of OSCC, and ORAOV1-A expression may serve as an adjunctive prognostic indicator for persons with OSCC.
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Affiliation(s)
- L Jiang
- State Key Laboratory of Oral Diseases, West China College of Stomatology, Sichuan University, No. 14, Sec.3, Renminnan Road, Chengdu, Sichuan, 610041, China
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Revil T, Pelletier J, Toutant J, Cloutier A, Chabot B. Heterogeneous nuclear ribonucleoprotein K represses the production of pro-apoptotic Bcl-xS splice isoform. J Biol Chem 2009; 284:21458-67. [PMID: 19520842 DOI: 10.1074/jbc.m109.019711] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The Bcl-x pre-mRNA is alternatively spliced to produce the anti-apoptotic Bcl-x(L) and the pro-apoptotic Bcl-x(S) isoforms. By performing deletion mutagenesis on a human Bcl-x minigene, we have identified a novel exonic element that controls the use of the 5' splice site of Bcl-x(S). The proximal portion of this element acts as a repressor and is located downstream of an enhancer. Further mutational analysis provided a detailed topological map of the regulatory activities revealing a sharp transition between enhancer and repressor sequences. Portions of the enhancer can function when transplanted in another alternative splicing unit. Chromatography and immunoprecipitation assays indicate that the silencer element interacts with heterogeneous ribonucleoprotein particle (hnRNP) K, consistent with the presence of putative high affinity sites for this protein. Finally, down-regulation of hnRNP K by RNA interference enhanced splicing to Bcl-x(S), an effect seen only when the sequences bound by hnRNP K are present. Our results therefore document a clear role for hnRNP K in preventing the production of the pro-apoptotic Bcl-x(S) splice isoform.
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Affiliation(s)
- Timothée Revil
- RNA/RNP Group, Département de Microbiologie et d'Infectiologie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
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35
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Wang E, Cambi F. Heterogeneous nuclear ribonucleoproteins H and F regulate the proteolipid protein/DM20 ratio by recruiting U1 small nuclear ribonucleoprotein through a complex array of G runs. J Biol Chem 2009; 284:11194-204. [PMID: 19244236 DOI: 10.1074/jbc.m809373200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
In this study, we sought to investigate the mechanism by which heterogeneous nuclear ribonucleoprotein (hnRNP) H and F regulate proteolipid protein (PLP)/DM20 alternative splicing. G-rich sequences in exon 3B, G1 and M2, are required for hnRNPH- and F-mediated regulation of the PLP/DM20 ratio and, when placed between competing 5' splice sites in an alpha-globin minigene, direct hnRNPH/F-regulated alternative splicing. In contrast, the activity of the intronic splicing enhancer, which is necessary for PLP splicing, is only modestly reduced by removal of hnRNPH/F both in PLP and alpha-globin gene context. In vivo, hnRNPH reversed reduction of DM20 splicing induced by hnRNPH/F removal, whereas hnRNPF had little effect. Tethering of the MS2-hnRNPH fusion protein downstream of the DM20 5' splice site increased DM20 splicing, whereas MS2-hnRNPF did not. Binding of U1 small nuclear ribonucleoprotein (U1snRNP) to DM20 is greatly impaired by mutation of G1 and M2 and depletion of hnRNPH and F. Reconstitution of hnRNPH/F-depleted extracts with either hnRNPH or F restored U1snRNP binding. We conclude that hnRNPH and F regulate DM20 splicing by recruiting U1snRNP and that hnRNPH plays a primary role in DM20 splice site selection in vivo. Decreased expression of hnRNPH/F in differentiated oligodendrocytes may regulate the PLP/DM20 ratio by reducing DM20 5' splice site recognition by U1snRNP.
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Affiliation(s)
- Erming Wang
- Department of Neurology, University of Kentucky, Lexington, Kentucky 40536, USA
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36
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Cloutier P, Toutant J, Shkreta L, Goekjian S, Revil T, Chabot B. Antagonistic Effects of the SRp30c Protein and Cryptic 5 ′ Splice Sites on the Alternative Splicing of the Apoptotic Regulator Bcl-x. J Biol Chem 2008; 283:21315-24. [DOI: 10.1074/jbc.m800353200] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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37
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Hai Y, Cao W, Liu G, Hong SP, Elela SA, Klinck R, Chu J, Xie J. A G-tract element in apoptotic agents-induced alternative splicing. Nucleic Acids Res 2008; 36:3320-31. [PMID: 18440980 PMCID: PMC2425498 DOI: 10.1093/nar/gkn207] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Alternative splicing of a single pre-mRNA transcript can produce protein isoforms that promote either cell growth or death. Here we show that Ro-31-8220 (Ro), an apoptotic agent that inhibits protein kinase C and activates the c-Jun N terminal kinase, decreased the proportion of the cell growth-promoting Bcl-xL splice variant. Targeted mutagenesis analyses narrowed down a critical sequence to a 16-nt G-tract element (Gt16). Transferring this element to a heterologous gene conferred Ro response on an otherwise constitutive exon. The Ro effect was reduced by okadaic acid, an inhibitor of protein phosphatases PP1 and PP2A, in a concentration-dependent manner. Search in the human genome followed by RT–PCR identified a group of genes that contain similar exonic G-tract elements and are responsive to Ro. Moreover, the Gt16 element also mediates the regulation of alternative splicing by other cell apoptosis-inducers particularly retinoic acid. Therefore, the G-tract element likely plays a role in the apoptotic agents-induced alternative splicing of a group of genes. The functions of these genes imply that this regulation will have impact on cell growth/death.
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Affiliation(s)
- Yan Hai
- Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College. Kunming, China
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38
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Emetine and the alternative splicing of Bcl-X: where to next? ACTA ACUST UNITED AC 2008; 14:1313-4. [PMID: 18096499 DOI: 10.1016/j.chembiol.2007.12.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Interference with the alternative splicing of apoptotic factors offers an innovative and specific mechanism to target malignant cells. In this issue of Chemistry & Biology, Zhou et al. report on the regulation of the alternative splicing of Bcl-x pre-mRNA in response to emetine, a potent protein synthesis inhibitor, as well as define a major player in the signaling mechanism.
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Jiang K, Apostolatos AH, Ghansah T, Watson JE, Vickers T, Cooper DR, Epling-Burnette PK, Patel NA. Identification of a novel antiapoptotic human protein kinase C delta isoform, PKCdeltaVIII in NT2 cells. Biochemistry 2007; 47:787-97. [PMID: 18092819 DOI: 10.1021/bi7019782] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Protein kinase C (PKC) delta plays an important role in cellular proliferation and apoptosis where it is involved in the caspase-3 mediated apoptotic pathway. Cleavage of PKCdeltaI by caspase-3 releases a catalytically active C-terminal fragment that is sufficient to induce apoptosis. In this paper, we identified a novel human PKCdelta isozyme, PKCdeltaVIII (Genbank accession number DQ516383) in human teratocarcinoma (NT2) cells that differentiate into hNT neurons upon retinoic acid (RA) treatment. Expression of PKCdeltaVIII was confirmed by real-time RT-PCR analysis, and we observed that after an initial peak at 24 h following RA treatment, its expression gradually declined with prolonged RA treatment. PKCdeltaVIII is generated via the utilization of an alternative 5' splice site, and this results in an insertion of 31 amino acids in the caspase-3 recognition sequence DMQD. The function of PKCdeltaVIII was examined by subcloning it into an expression vector and raising an antibody specific to PKCdeltaVIII. Using in vivo and in vitro assays, we demonstrated that PKCdeltaVIII is resistant to caspase-3 cleavage. Next, we sought to determine the role of PKCdeltaVIII in apoptosis in NT2 cells. Overexpression of PKCdeltaVIII and knockdown using PKCdeltaVIII siRNA suggest an antiapoptotic function for the PKCdeltaVIII isozyme. We demonstrate that antisense oligonucleotides (ASO) directed toward the 5' splice site I promote the expression of the PKCdeltaVIII isozyme. Our results indicated that ASO mediated PKCdeltaVIII expression rescued NT2 cells from etoposide-induced apoptosis. We conclude that the novel human PKCdeltaVIII splice variant functions as an antiapoptotic protein in NT2 cells.
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Affiliation(s)
- Kun Jiang
- Department of Molecular Medicine, College of Medicine, University of South Florida, Tampa, Florida 33612, USA
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40
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Revil T, Toutant J, Shkreta L, Garneau D, Cloutier P, Chabot B. Protein kinase C-dependent control of Bcl-x alternative splicing. Mol Cell Biol 2007; 27:8431-41. [PMID: 17923691 PMCID: PMC2169420 DOI: 10.1128/mcb.00565-07] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2007] [Revised: 05/07/2007] [Accepted: 09/19/2007] [Indexed: 02/07/2023] Open
Abstract
The alternative splicing of Bcl-x generates the proapoptotic Bcl-x(S) protein and the antiapoptotic isoform Bcl-x(L). Bcl-x splicing is coupled to signal transduction, since ceramide, hormones, and growth factors alter the ratio of the Bcl-x isoforms in different cell lines. Here we report that the protein kinase C (PKC) inhibitor and apoptotic inducer staurosporine switches the production of Bcl-x towards the x(S) mRNA isoform in 293 cells. The increase in Bcl-x(S) elicited by staurosporine likely involves signaling events that affect splicing decisions, because it requires active transcription and no new protein synthesis and is independent of caspase activation. Moreover, the increase in Bcl-x(S) is reproduced with more specific inhibitors of PKC. Alternative splicing of the receptor tyrosine kinase gene Axl is similarly affected by staurosporine in 293 cells. In contrast to the case for 293 cells, PKC inhibitors do not influence the alternative splicing of Bcl-x and Axl in cancer cell lines, suggesting that these cells have sustained alterations that uncouple splicing decisions from PKC-dependent signaling. Using minigenes, we show that an exonic region located upstream of the Bcl-x(S) 5' splice site is important to mediate the staurosporine shift in Bcl-x splicing. When transplanted to other alternative splicing units, portions of this region confer splicing modulation and responsiveness to staurosporine, suggesting the existence of factors that couple splicing decisions with PKC signaling.
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Affiliation(s)
- Timothée Revil
- RNA/RNP Group, Département de Microbiologie et d'Infectiologie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
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41
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Paronetto MP, Achsel T, Massiello A, Chalfant CE, Sette C. The RNA-binding protein Sam68 modulates the alternative splicing of Bcl-x. ACTA ACUST UNITED AC 2007; 176:929-39. [PMID: 17371836 PMCID: PMC2064079 DOI: 10.1083/jcb.200701005] [Citation(s) in RCA: 253] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The RNA-binding protein Sam68 is involved in apoptosis, but its cellular mRNA targets and its mechanism of action remain unknown. We demonstrate that Sam68 binds the mRNA for Bcl-x and affects its alternative splicing. Depletion of Sam68 by RNA interference caused accumulation of antiapoptotic Bcl-x(L), whereas its up-regulation increased the levels of proapoptotic Bcl-x(s). Tyrosine phosphorylation of Sam68 by Fyn inverted this effect and favored the Bcl-x(L) splice site selection. A point mutation in the RNA-binding domain of Sam68 influenced its splicing activity and subnuclear localization. Moreover, coexpression of ASF/SF2 with Sam68, or fusion with an RS domain, counteracted Sam68 splicing activity toward Bcl-x. Finally, Sam68 interacted with heterogenous nuclear RNP (hnRNP) A1, and depletion of hnRNP A1 or mutations that impair this interaction attenuated Bcl-x(s) splicing. Our results indicate that Sam68 plays a role in the regulation of Bcl-x alternative splicing and that tyrosine phosphorylation of Sam68 by Src-like kinases can switch its role from proapoptotic to antiapoptotic in live cells.
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Affiliation(s)
- Maria Paola Paronetto
- Department of Public Health and Cell Biology, Section of Anatomy, University of Rome Tor Vergata, 00133 Rome, Italy
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42
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Zhou HL, Baraniak AP, Lou H. Role for Fox-1/Fox-2 in mediating the neuronal pathway of calcitonin/calcitonin gene-related peptide alternative RNA processing. Mol Cell Biol 2007; 27:830-41. [PMID: 17101796 PMCID: PMC1800674 DOI: 10.1128/mcb.01015-06] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2006] [Revised: 07/31/2006] [Accepted: 10/27/2006] [Indexed: 11/20/2022] Open
Abstract
Although multiple regulatory elements and protein factors are known to regulate the non-neuronal pathway of alternative processing of the calcitonin/calcitonin gene-related peptide (CGRP) pre-mRNA, the mechanisms controlling the neuron-specific pathway have remained elusive. Here we report the identification of Fox-1 and Fox-2 proteins as novel regulators that mediate the neuron-specific splicing pattern. Fox-1 and Fox-2 proteins function to repress exon 4 inclusion, and this effect depends on two UGCAUG elements surrounding the 3' splice site of the calcitonin-specific exon 4. In neuron-like cells, mutation of a subset of UGCAUG elements promotes the non-neuronal pattern in which exon 4 is included. In HeLa cells, overexpression of Fox-1 or Fox-2 protein decreases exon 4 inclusion. Fox-1 and Fox-2 proteins interact with the UGCAUG elements specifically and regulate splicing by blocking U2AF(65) binding to the 3' splice site upstream of exon 4. We further investigated the inter-relationship between the UGCAUG silencer elements and the previously identified intronic and exonic splicing regulatory elements and found that exon 4 is regulated by an intricate balance of positive and negative regulation. These results define a critical role for Fox-1 and Fox-2 proteins in exon 4 inclusion of calcitonin/CGRP pre-mRNA and establish a regulatory network that controls the fate of exon 4.
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Affiliation(s)
- Hua-Lin Zhou
- Department of Genetics, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106, USA.
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43
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Dominguez C, Allain FHT. NMR structure of the three quasi RNA recognition motifs (qRRMs) of human hnRNP F and interaction studies with Bcl-x G-tract RNA: a novel mode of RNA recognition. Nucleic Acids Res 2006; 34:3634-45. [PMID: 16885237 PMCID: PMC1540728 DOI: 10.1093/nar/gkl488] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2006] [Revised: 06/28/2006] [Accepted: 06/28/2006] [Indexed: 02/03/2023] Open
Abstract
The heterogeneous nuclear ribonucleoprotein (hnRNP) F belongs to the hnRNP H family involved in the regulation of alternative splicing and polyadenylation and specifically recognizes poly(G) sequences (G-tracts). In particular, hnRNP F binds a G-tract of the Bcl-x RNA and regulates its alternative splicing, leading to two isoforms, Bcl-x(S) and Bcl-x(L), with antagonist functions. In order to gain insight into G-tract recognition by hnRNP H members, we initiated an NMR study of human hnRNP F. We present the solution structure of the three quasi RNA recognition motifs (qRRMs) of hnRNP F and identify the residues that are important for the interaction with the Bcl-x RNA by NMR chemical shift perturbation and mutagenesis experiments. The three qRRMs exhibit the canonical betaalphabetabetaalphabeta RRM fold but additional secondary structure elements are present in the two N-terminal qRRMs of hnRNP F. We show that qRRM1 and qRRM2 but not qRRM3 are responsible for G-tract recognition and that the residues of qRRM1 and qRRM2 involved in G-tract interaction are not on the beta-sheet surface as observed for the classical RRM but are part of a short beta-hairpin and two adjacent loops. These regions define a novel interaction surface for RNA recognition by RRMs.
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Affiliation(s)
- Cyril Dominguez
- Institute of Molecular Biology and Biophysics, ETH ZürichCH-8093 Zürich, Switzerland
| | - Frédéric H.-T. Allain
- Institute of Molecular Biology and Biophysics, ETH ZürichCH-8093 Zürich, Switzerland
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44
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Massiello A, Roesser JR, Chalfant CE. SAP155 Binds to ceramide-responsive RNA cis-element 1 and regulates the alternative 5' splice site selection of Bcl-x pre-mRNA. FASEB J 2006; 20:1680-2. [PMID: 16790528 DOI: 10.1096/fj.05-5021fje] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Two splice variants are derived from the BCL-x gene, proapoptotic Bcl-x(s) and antiapoptotic Bcl-x(L), via alternative 5' splice site selection. In previous studies, our laboratory identified an RNA cis-element within exon 2 of Bcl-x pre-mRNA that is a ceramide responsive termed CRCE 1. In this study, mass spectrometric analysis identified the splicing factor SAP155, as an RNA trans-acting factor binding to the purine-rich CRCE 1. The interaction of SAP155 with CRCE 1 was confirmed by the addition of an anti-SAP155 antibody (Ab) to EMSA decreasing the mobility of a protein:CRCE 1 complex (SuperShift). Furthermore, the down-regulation of SAP155 in A549 cells by RNA interference (RNAi) technology resulted in the loss of a 155 kDa protein complexed with CRCE 1. Moreover, this down-regulation of SAP155 induced an increase in the Bcl-x(s) with a concomitant decrease in the Bcl-x(L) splice variants and immunoreactive protein levels, thereby decreasing the Bcl-x(L)/Bcl-x(s) ratio. Specific down-regulation of SAP155 also inhibited the ability of exogenous ceramide treatment to further induce the activation of the Bcl-x(s) 5' splice site. Additionally, the specific down-regulation of SAP155 sensitized cells to undergo apoptosis in response to daunorubicin in a manner similar to ceramide. Therefore, we have identified SAP155 as an RNA trans-acting factor that binds to CRCE 1, functions to regulate the alternative 5' splice site selection of Bcl-x pre-mRNA, and is required for ceramide to induce the activation of the Bcl-x(s) 5' splice site. Furthermore, we have demonstrated that activation of the Bcl-x(s) 5' splice site can increase the effectiveness of chemotherapeutic drug treatment, thus establishing a role for the alternative splicing mechanism of Bcl-x in chemotherapeutic sensitivity.
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Affiliation(s)
- Autumn Massiello
- Department of Biochemistry, Rm. 2-016, Sanger Hall, Virginia Commonwealth University, 1101 East Marshall St., P.O. Box 980614, Richmond, Virginia 23298-0614, USA
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45
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Chen S, Lee JM, Zeng C, Chen H, Hsu CY, Xu J. Amyloid beta peptide increases DP5 expression via activation of neutral sphingomyelinase and JNK in oligodendrocytes. J Neurochem 2006; 97:631-40. [PMID: 16524368 DOI: 10.1111/j.1471-4159.2006.03774.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
There is growing recognition that white matter pathology is a common feature in Alzheimer's disease. We have previously reported that the amyloid beta peptide (Abeta) induces apoptosis in oligodendrocytes (OLG), via activation of neutral sphingomyelinase (nSMase) and resultant generation of ceramide. In the current study, we report that both Abeta and ceramide increased expression of the proapoptotic protein DP5/Hrk (DP5), and release of cytochrome C from mitochondria to cytoplasm in OLGs. We provide evidence that the Jun N-terminal kinase (JNK) signaling pathway mediates Abeta- and ceramide-induced apoptosis: Both Abeta and ceramide activated JNK phosphorylation, and subsequent AP-1 DNA binding activity; JNK siRNA decreased AP-1 DNA binding, DP5 expression and reduced cell death. Furthermore, inhibition of nSMase attenuated Abeta-induced JNK phosphorylation, AP-1 DNA binding activity, DP5 expression, and cytochrome C release. Collectively, these results suggest that Abeta-induced apoptosis involves the sequential activation of nSMase with ceramide generation, JNK activation, AP-1 DNA binding, and DP5 expression.
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Affiliation(s)
- Shawei Chen
- Department of Neurology and the Hope Center for Neurological Disorders, Washington University, School of Medicine, St Louis, MO 63110, USA
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46
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Soret J, Gabut M, Tazi J. SR Proteins as Potential Targets for Therapy. ALTERNATIVE SPLICING AND DISEASE 2006; 44:65-87. [PMID: 17076265 DOI: 10.1007/978-3-540-34449-0_4] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Serine- and arginine-rich (SR) proteins constitute a highly conserved family of pre-mRNA splicing factors that play key roles in the regulation of splice site selection, and thereby in the control of alternative splicing processes. In addition to conserved sequences at the splice junctions, splice site selection also depends upon different sets of auxiliary cis regulatory elements known as exonic and intronic splicing enhancers (ESEs and ISEs) or exonic and intronic silencers (ESSs and ISSs). Specific binding of SR proteins to their cognate splicing enhancers as well as binding of splicing repressor to silencer sequences serve to enhance or inhibit recognition of weak splice sites by the splicing machinery. Given that the vast majority of human genes contain introns and that most pre-mRNAs containing multiple exons undergo alternative splicing, mutations disrupting or creating such auxiliary elements can result in aberrant splicing events at the origin of various human diseases. In the past few years, numerous studies have reported several approaches allowing correction of such aberrant splicing events by targeting either the mutated sequences or the splicing regulators whose binding is affected by the mutation. The aim of the present review is to highlight the different means by which it is possible to modulate the activity of SR splicing factors and to bring out those holding the greatest promises for the development of therapeutic treatments.
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Affiliation(s)
- Johann Soret
- Institut de Génétique Moléculaire de Montpellier, UMR 5535, IFR 122, Centre National de Recherche Scientifique, 1919, route de Mende, 34293 Montpellier, France
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47
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Wilusz JE, Devanney SC, Caputi M. Chimeric peptide nucleic acid compounds modulate splicing of the bcl-x gene in vitro and in vivo. Nucleic Acids Res 2005; 33:6547-54. [PMID: 16299354 PMCID: PMC1289079 DOI: 10.1093/nar/gki960] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Alternative splicing of the bcl-x gene generates two transcripts: the anti-apoptotic bcl-xL isoform and the pro-apoptotic bcl-xS isoform. The ratio between the two isoforms is a key factor in development and in cancer progression. Here, we show that a short antisense chimeric peptide nucleic acid (PNA) oligonucleotide conjugated to a polypeptide containing eight Ser-Arg repeats (SR)8 can modulate splicing of bcl-x both in vitro and in vivo and induces apoptosis in HeLa cells. The PNA-SR oligo was targeted to a region of bcl-x that does not contain splicing regulatory sequences and was able to override the complex network of splicing enhancers and silencers that regulates the ratio between the two bcl-x isoforms. Thus, PNA-SR oligos are powerful tools that can potentially modulate splice site choice in endogenous genes independent of the presence of other splicing regulatory mechanisms on the target gene.
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Affiliation(s)
| | - Sean C. Devanney
- Biomedical Science Department, Florida Atlantic UniversityBoca Raton, FL 33431, USA
| | - Massimo Caputi
- Biomedical Science Department, Florida Atlantic UniversityBoca Raton, FL 33431, USA
- To whom correspondence should be addressed. Tel: +1 561 297 0627; Fax: +1 561 297 2221;
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Chalfant CE, Spiegel S. Sphingosine 1-phosphate and ceramide 1-phosphate: expanding roles in cell signaling. J Cell Sci 2005; 118:4605-12. [PMID: 16219683 DOI: 10.1242/jcs.02637] [Citation(s) in RCA: 322] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The phosphorylated sphingolipid metabolites sphingosine 1-phosphate (S1P) and ceramide 1-phosphate (C1P) have emerged as potent bioactive agents. Recent studies have begun to define new biological functions for these lipids. Generated by sphingosine kinases and ceramide kinase, they control numerous aspects of cell physiology, including cell survival and mammalian inflammatory responses. Interestingly, S1P is involved in cyclooxygenase-2 induction and C1P is required for the activation and translocation of cPLA2. This suggests that these two sphingolipid metabolites may act in concert to regulate production of eicosanoids, important inflammatory mediators. Whereas S1P functions mainly via G-protein-coupled receptors, C1P appears to bind directly to targets such as cPLA2 and protein phosphatase 1/2A. S1P probably also has intracellular targets, and in plants it appears to directly regulate the G protein α subunit GPA1.
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Affiliation(s)
- Charles E Chalfant
- Department of Biochemistry, Virginia Commonwealth University School of Medicine and Massey Cancer Center, Richmond, VA 23298, USA.
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49
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Schwerk C, Schulze-Osthoff K. Regulation of Apoptosis by Alternative Pre-mRNA Splicing. Mol Cell 2005; 19:1-13. [PMID: 15989960 DOI: 10.1016/j.molcel.2005.05.026] [Citation(s) in RCA: 417] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2004] [Revised: 02/22/2005] [Accepted: 05/05/2005] [Indexed: 12/15/2022]
Abstract
Apoptosis, a phenomenon that allows the regulated destruction and disposal of damaged or unwanted cells, is common to many cellular processes in multicellular organisms. In humans more than 200 proteins are involved in apoptosis, many of which are dysregulated or defective in human diseases including cancer. A large number of apoptotic factors are regulated via alternative splicing, a process that allows for the production of discrete protein isoforms with often distinct functions from a common mRNA precursor. The abundance of apoptosis genes that are alternatively spliced and the often antagonistic roles of the generated protein isoforms strongly imply that alternative splicing is a crucial mechanism for regulating life and death decisions. Importantly, modulation of isoform production of cell death proteins via pharmaceutical manipulation of alternative splicing may open up new therapeutic avenues for the treatment of disease.
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Affiliation(s)
- Christian Schwerk
- Institute of Molecular Medicine, University of Düsseldorf, Building 23.12, Universitätsstrasse 1, 40225 Düsseldorf, Germany
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Bieberich E. Integration of glycosphingolipid metabolism and cell-fate decisions in cancer and stem cells: review and hypothesis. Glycoconj J 2005; 21:315-27. [PMID: 15514480 DOI: 10.1023/b:glyc.0000046274.35732.47] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The metabolism of glycosphingolipids is strictly regulated during the mitotic cell cycle. Before the G1-to-S transition, the ceramide and glucosylceramide concentration is elevated. Ceramide induces apoptosis synergistically with the pro-apoptotic protein prostate apoptosis response 4 (PAR-4) that may be asymmetrically inherited during cell division. Only one daughter cell dies shortly after mitosis, a mechanism we suggested to regulate the number of neural stem cells during embryonic development. The progeny cells, however, may protect themselves by converting ceramide to glucosylceramide and other glycosphingolipids. In particular, complex gangliosides have been found to sustain cell survival and differentiation. The cell cycle may thus be a turning point for (glyco)sphingolipid metabolism and explain rapid changes of the sphingolipid composition in cells that undergo mitotic cell-fate decisions. In the proposed model termed "Shiva cycle", progression through the cell cycle, differentiation, or apoptosis may rely on a delicate balance of (glyco)sphingolipid second messengers that modulate the retinoblastoma-dependent G1-to-S transition or caspase-dependent G1-to-apoptosis program. Ceramide-induced cell cycle delay at G0/G1 is either followed by ceramide-induced apoptosis or by conversion of ceramide to glucosylceramide, a proposed key regulatory rheostat that rescues cells from re-entry into a life/death decision at G1-to-S. We propose a mechanistic model for sphingolpid-induced protein scaffolds ("slip") that regulate cell-fate decisions and will discuss the biological consequences and pharmacological potential of manipulating the (glyco)sphingolipid-dependent cell fate program in cancer and stem cells.
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Affiliation(s)
- Erhard Bieberich
- Institute of Molecular Medicine and Genetics, School of Medicine, Medical College of Georgia, 1120 15th Street Room CB-2803, Augusta, GA 30912, USA.
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