1
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Weber-Stout M, Nicholson RJ, Dumaguit CDC, Holland WL, Summers SA. Ceramide microdomains: the major influencers of the sphingolipid media platform. Biochem Soc Trans 2024; 52:1765-1776. [PMID: 39082976 DOI: 10.1042/bst20231395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/29/2024]
Abstract
Like 'influencers' who achieve fame and power through social media, ceramides are low abundance members of communication platforms that have a mighty impact on their surroundings. Ceramide microdomains form within sphingolipid-laden lipid rafts that confer detergent resistance to cell membranes and serve as important signaling hubs. In cells exposed to excessive amounts of saturated fatty acids (e.g. in obesity), the abundance of ceramide-rich microdomains within these rafts increases, leading to concomitant alterations in cellular metabolism and survival that contribute to cardiometabolic disease. In this mini-review, we discuss the evidence supporting the formation of these ceramide microdomains and describe the spectrum of harmful ceramide-driven metabolic actions under the context of an evolutionary theory. Moreover, we discuss the proximal 'followers' of these ceramide media stars that account for the diverse intracellular actions that allow them to influence obesity-linked disease.
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Affiliation(s)
- Mariah Weber-Stout
- Department of Nutrition and Integrative Physiology and the Diabetes and Metabolism Research Center, University of Utah, Salt Lake City, UT 84112, U.S.A
| | - Rebekah J Nicholson
- Department of Nutrition and Integrative Physiology and the Diabetes and Metabolism Research Center, University of Utah, Salt Lake City, UT 84112, U.S.A
| | - Carlos Dave C Dumaguit
- Department of Nutrition and Integrative Physiology and the Diabetes and Metabolism Research Center, University of Utah, Salt Lake City, UT 84112, U.S.A
| | - William L Holland
- Department of Nutrition and Integrative Physiology and the Diabetes and Metabolism Research Center, University of Utah, Salt Lake City, UT 84112, U.S.A
| | - Scott A Summers
- Department of Nutrition and Integrative Physiology and the Diabetes and Metabolism Research Center, University of Utah, Salt Lake City, UT 84112, U.S.A
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2
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Maus KD, Stephenson DJ, Macknight HP, Vu NT, Hoeferlin LA, Kim M, Diegelmann RF, Xie X, Chalfant CE. Skewing cPLA 2α activity toward oxoeicosanoid production promotes neutrophil N2 polarization, wound healing, and the response to sepsis. Sci Signal 2023; 16:eadd6527. [PMID: 37433004 PMCID: PMC10565596 DOI: 10.1126/scisignal.add6527] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 06/16/2023] [Indexed: 07/13/2023]
Abstract
Uncontrolled inflammation is linked to poor outcomes in sepsis and wound healing, both of which proceed through distinct inflammatory and resolution phases. Eicosanoids are a class of bioactive lipids that recruit neutrophils and other innate immune cells. The interaction of ceramide 1-phosphate (C1P) with the eicosanoid biosynthetic enzyme cytosolic phospholipase A2 (cPLA2) reduces the production of a subtype of eicosanoids called oxoeicosanoids. We investigated the effect of shifting the balance in eicosanoid biosynthesis on neutrophil polarization and function. Knockin mice expressing a cPLA2 mutant lacking the C1P binding site (cPLA2αKI/KI mice) showed enhanced and sustained neutrophil infiltration into wounds and the peritoneum during the inflammatory phase of wound healing and sepsis, respectively. The mice exhibited improved wound healing and reduced susceptibility to sepsis, which was associated with an increase in anti-inflammatory N2-type neutrophils demonstrating proresolution behaviors and a decrease in proinflammatory N1-type neutrophils. The N2 polarization of cPLA2αKI/KI neutrophils resulted from increased oxoeicosanoid biosynthesis and autocrine signaling through the oxoeicosanoid receptor OXER1 and partially depended on OXER1-dependent inhibition of the pentose phosphate pathway (PPP). Thus, C1P binding to cPLA2α suppresses neutrophil N2 polarization, thereby impairing wound healing and the response to sepsis.
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Affiliation(s)
- Kenneth D Maus
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL 33620, USA
| | - Daniel J Stephenson
- Department of Medicine, Division of Hematology and Oncology, University of Virginia, Charlottesville, VA 22903, USA
| | - H Patrick Macknight
- Department of Medicine, Division of Hematology and Oncology, University of Virginia, Charlottesville, VA 22903, USA
| | - Ngoc T Vu
- Department of Applied Biochemistry, School of Biotechnology, International University-VNU HCM, Ho Chi Minh City, Vietnam
| | - L Alexis Hoeferlin
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University-School of Medicine, Richmond VA 23298, USA
| | - Minjung Kim
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL 33620, USA
| | - Robert F Diegelmann
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University-School of Medicine, Richmond VA 23298, USA
| | - Xiujie Xie
- Department of Medicine, Division of Hematology and Oncology, University of Virginia, Charlottesville, VA 22903, USA
| | - Charles E Chalfant
- Department of Medicine, Division of Hematology and Oncology, University of Virginia, Charlottesville, VA 22903, USA
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22903, USA
- Program in Cancer Biology, University of Virginia Cancer Center, Charlottesville, VA 22903, USA
- Research Service, Richmond Veterans Administration Medical Center, Richmond VA, 23298, USA
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3
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Wang E, Pineda JMB, Kim WJ, Chen S, Bourcier J, Stahl M, Hogg SJ, Bewersdorf JP, Han C, Singer ME, Cui D, Erickson CE, Tittley SM, Penson AV, Knorr K, Stanley RF, Rahman J, Krishnamoorthy G, Fagin JA, Creger E, McMillan E, Mak CC, Jarvis M, Bossard C, Beaupre DM, Bradley RK, Abdel-Wahab O. Modulation of RNA splicing enhances response to BCL2 inhibition in leukemia. Cancer Cell 2023; 41:164-180.e8. [PMID: 36563682 PMCID: PMC9839614 DOI: 10.1016/j.ccell.2022.12.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 10/07/2022] [Accepted: 12/05/2022] [Indexed: 12/24/2022]
Abstract
Therapy resistance is a major challenge in the treatment of cancer. Here, we performed CRISPR-Cas9 screens across a broad range of therapies used in acute myeloid leukemia to identify genomic determinants of drug response. Our screens uncover a selective dependency on RNA splicing factors whose loss preferentially enhances response to the BCL2 inhibitor venetoclax. Loss of the splicing factor RBM10 augments response to venetoclax in leukemia yet is completely dispensable for normal hematopoiesis. Combined RBM10 and BCL2 inhibition leads to mis-splicing and inactivation of the inhibitor of apoptosis XIAP and downregulation of BCL2A1, an anti-apoptotic protein implicated in venetoclax resistance. Inhibition of splicing kinase families CLKs (CDC-like kinases) and DYRKs (dual-specificity tyrosine-regulated kinases) leads to aberrant splicing of key splicing and apoptotic factors that synergize with venetoclax, and overcomes resistance to BCL2 inhibition. Our findings underscore the importance of splicing in modulating response to therapies and provide a strategy to improve venetoclax-based treatments.
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Affiliation(s)
- Eric Wang
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA.
| | - Jose Mario Bello Pineda
- Public Health Sciences and Basic Sciences Divisions, Fred Hutchinson Cancer Research Center, Seattle, WA, USA; Department of Genome Sciences, University of Washington, Seattle, WA, USA; Medical Scientist Training Program, University of Washington, Seattle, WA, USA
| | - Won Jun Kim
- Molecular Pharmacology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Sisi Chen
- Molecular Pharmacology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Jessie Bourcier
- Molecular Pharmacology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Maximilian Stahl
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Simon J Hogg
- Molecular Pharmacology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Jan Phillipp Bewersdorf
- Molecular Pharmacology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Cuijuan Han
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Michael E Singer
- Molecular Pharmacology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Daniel Cui
- Molecular Pharmacology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Caroline E Erickson
- Molecular Pharmacology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Steven M Tittley
- Molecular Pharmacology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Alexander V Penson
- Molecular Pharmacology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Katherine Knorr
- Molecular Pharmacology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Robert F Stanley
- Molecular Pharmacology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Jahan Rahman
- Molecular Pharmacology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Gnana Krishnamoorthy
- Human Oncology and Pathogenesis Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA; Department of Medicine, Division of Endocrinology, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - James A Fagin
- Human Oncology and Pathogenesis Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA; Department of Medicine, Division of Endocrinology, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | | | | | | | | | | | | | - Robert K Bradley
- Public Health Sciences and Basic Sciences Divisions, Fred Hutchinson Cancer Research Center, Seattle, WA, USA; Department of Genome Sciences, University of Washington, Seattle, WA, USA.
| | - Omar Abdel-Wahab
- Molecular Pharmacology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
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4
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Maus KD, Stephenson DJ, Ali AN, MacKnight HP, Huang HJ, Serrats J, Kim M, Diegelmann RF, Chalfant CE. Ceramide kinase regulates acute wound healing by suppressing 5-oxo-ETE biosynthesis and signaling via its receptor OXER1. J Lipid Res 2022; 63:100187. [PMID: 35219746 PMCID: PMC8980959 DOI: 10.1016/j.jlr.2022.100187] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 02/18/2022] [Accepted: 02/21/2022] [Indexed: 01/10/2023] Open
Abstract
The sphingolipid, ceramide-1-phosphate (C1P), has been shown to promote the inflammatory phase and inhibit the proliferation and remodeling stages of wound repair via direct interaction with group IVA cytosolic phospholipase A2, a regulator of eicosanoid biosynthesis that fine-tunes the behaviors of various cell types during wound healing. However, the anabolic enzyme responsible for the production of C1P that suppresses wound healing as well as bioactive eicosanoids and target receptors that drive enhanced wound remodeling have not been characterized. Herein, we determined that decreasing C1P activity via inhibitors or genetic ablation of the anabolic enzyme ceramide kinase (CERK) significantly enhanced wound healing phenotypes. Importantly, postwounding inhibition of CERK enhanced the closure rate of acute wounds, improved the quality of healing, and increased fibroblast migration via a "class switch" in the eicosanoid profile. This switch reduced pro-inflammatory prostaglandins (e.g., prostaglandin E2) and increased levels of 5-hydroxyeicosatetraenoic acid and the downstream metabolite 5-oxo-eicosatetraenoic acid (5-oxo-ETE). Moreover, dermal fibroblasts from mice with genetically ablated CERK showed enhanced wound healing markers, while blockage of the murine 5-oxo-ETE receptor (oxoeicosanoid receptor 1) inhibited the enhanced migration phenotype of these cell models. Together, these studies reinforce the vital roles eicosanoids play in the wound healing process and demonstrate a novel role for CERK-derived C1P as a negative regulator of 5-oxo-ETE biosynthesis and the activation of oxoeicosanoid receptor 1 in wound healing. These findings provide foundational preclinical results for the use of CERK inhibitors to shift the balance from inflammation to resolution and increase the wound healing rate.
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Affiliation(s)
- Kenneth D Maus
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL, USA
| | - Daniel J Stephenson
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL, USA
| | - Anika N Ali
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL, USA
| | - Henry Patrick MacKnight
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL, USA
| | - Huey-Jing Huang
- Neuroscience Drug Discovery Unit, Takeda California, San Diego, CA, USA
| | - Jordi Serrats
- Neuroscience Drug Discovery Unit, Takeda California, San Diego, CA, USA
| | - Minjung Kim
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL, USA
| | - Robert F Diegelmann
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University-School of Medicine, Richmond, VA, USA
| | - Charles E Chalfant
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL, USA; Cancer Biology and Evolution Program, The Moffitt Cancer Center, Tampa, FL, USA; Research Service, James A. Haley Veterans Hospital, Tampa, FL, USA; Division of Hematology & Oncology, Department of Medicine, University of Virginia, Charlottesville, VA, USA; Department of Cell Biology, University of Virginia, Charlottesville, VA, USA; Program in Cancer Biology, University of Virginia Cancer Center, Charlottesville, VA, USA; Research Service, Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, VA, USA.
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5
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The unfolding role of ceramide in coordinating retinoid-based cancer therapy. Biochem J 2021; 478:3621-3642. [PMID: 34648006 DOI: 10.1042/bcj20210368] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 09/02/2021] [Accepted: 09/03/2021] [Indexed: 12/30/2022]
Abstract
Sphingolipid-mediated regulation in cancer development and treatment is largely ceramide-centered with the complex sphingolipid metabolic pathways unfolding as attractive targets for anticancer drug discovery. The dynamic interconversion of sphingolipids is tightly controlled at the level of enzymes and cellular compartments in response to endogenous or exogenous stimuli, such as anticancer drugs, including retinoids. Over the past two decades, evidence emerged that retinoids owe part of their potency in cancer therapy to modulation of sphingolipid metabolism and ceramide generation. Ceramide has been proposed as a 'tumor-suppressor lipid' that orchestrates cell growth, cell cycle arrest, cell death, senescence, autophagy, and metastasis. There is accumulating evidence that cancer development is promoted by the dysregulation of tumor-promoting sphingolipids whereas cancer treatments can kill tumor cells by inducing the accumulation of endogenous ceramide levels. Resistance to cancer therapy may develop due to a disrupted equilibrium between the opposing roles of tumor-suppressor and tumor-promoter sphingolipids. Despite the undulating effect and complexity of sphingolipid pathways, there are emerging opportunities for a plethora of enzyme-targeted therapeutic interventions that overcome resistance resulting from perturbed sphingolipid pathways. Here, we have revisited the interconnectivity of sphingolipid metabolism and the instrumental role of ceramide-biosynthetic and degradative enzymes, including bioactive sphingolipid products, how they closely relate to cancer treatment and pathogenesis, and the interplay with retinoid signaling in cancer. We focused on retinoid targeting, alone or in combination, of sphingolipid metabolism nodes in cancer to enhance ceramide-based therapeutics. Retinoid and ceramide-based cancer therapy using novel strategies such as combination treatments, synthetic retinoids, ceramide modulators, and delivery formulations hold promise in the battle against cancer.
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6
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Khan SA, Goliwas KF, Deshane JS. Sphingolipids in Lung Pathology in the Coronavirus Disease Era: A Review of Sphingolipid Involvement in the Pathogenesis of Lung Damage. Front Physiol 2021; 12:760638. [PMID: 34690821 PMCID: PMC8531546 DOI: 10.3389/fphys.2021.760638] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Accepted: 09/21/2021] [Indexed: 12/17/2022] Open
Abstract
Sphingolipids are bioactive lipids involved in the regulation of cell survival, proliferation, and the inflammatory response. The SphK/S1P/S1PR pathway (S1P pathway) is a driver of many anti-apoptotic and proliferative processes. Pro-survival sphingolipid sphingosine-1-phosphate (S1P) initiates its signaling cascade by interacting with various sphingosine-1-phosphate receptors (S1PR) through which it is able to exert its pro-survival or inflammatory effects. Whereas sphingolipids, including ceramides and sphingosines are pro-apoptotic. The pro-apoptotic lipid, ceramide, can be produced de novo by ceramide synthases and converted to sphingosine by way of ceramidases. The balance of these antagonistic lipids and how this balance manifests is the essence of the sphingolipid rheostat. Recent studies on SARS-CoV-2 have implicated the S1P pathway in the pathogenesis of novel coronavirus disease COVID-19-related lung damage. Accumulating evidence indicates that an aberrant inflammatory process, known as "cytokine storm" causes lung injury in COVID-19, and studies have shown that the S1P pathway is involved in signaling this hyperinflammatory response. Beyond the influence of this pathway on cytokine storm, over the last decade the S1P pathway has been investigated for its role in a wide array of lung pathologies, including pulmonary fibrosis, pulmonary arterial hypertension (PAH), and lung cancer. Various studies have used S1P pathway modulators in models of lung disease; many of these efforts have yielded results that point to the potential efficacy of targeting this pathway for future treatment options. Additionally, they have emphasized S1P pathway's significant role in inflammation, fibrosis, and a number of other endothelial and epithelial changes that contribute to lung damage. This review summarizes the S1P pathway's involvement in COVID-19 and chronic lung diseases and discusses the potential for targeting S1P pathway as a therapeutic option for these diseases.
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Affiliation(s)
| | | | - Jessy S. Deshane
- Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States
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Gao F, Chen X, Lu J, Hu S, Xu H, Shi Y, Feng M, Ding J, Liu H, Luo C, Xie Z, Wang J. Discovery of novel ceramide analogs with favorable pharmacokinetic properties and combination with AKT inhibitor against colon cancer. Eur J Med Chem 2021; 215:113274. [PMID: 33592537 DOI: 10.1016/j.ejmech.2021.113274] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 02/01/2021] [Accepted: 02/01/2021] [Indexed: 10/22/2022]
Abstract
Ceramides have emerged as potential therapeutic option with novel mechanism to affect the proliferation, differentiation, senescence, and apoptosis of cancer cells through regulation of multiple signal transduction. Aiming at the improvement of the apoptosis activity and pharmacokinetic profiles of ceramides, a novel series of ceramide analogs were developed through structure simplification and conformation restriction. Among them, compound 12 bearing an alkoxyl naphthyl motif, with favorable rat pharmacokinetic properties, showed better anti-proliferative activity against various colon cancer cells (IC50 ∼20 μM) than other ceramide analogues, as well as the synergistic effect combined with AKT inhibitor MK2206. Additionally, we demonstrated that this combination therapy promoted caspase 3-dependent apoptotic pathway and intensified cell cycle arrest in the G0/G1 phase. Furthermore, the combination of compound 12 and MK2206 displayed synergistic anti-tumor effect in vivo.
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Affiliation(s)
- Feng Gao
- State Key Laboratory of Drug Research and CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiaoxu Chen
- State Key Laboratory of Drug Research and CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; University of Chinese Academy of Sciences, Beijing, 100049, China; School of Life Science and Technology, ShanghaiTech University, Shanghai, 200031, China
| | - Junyan Lu
- State Key Laboratory of Drug Research and CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Shulei Hu
- State Key Laboratory of Drug Research and CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Hui Xu
- State Key Laboratory of Drug Research and CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yuqiang Shi
- State Key Laboratory of Drug Research and CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Mingshun Feng
- State Key Laboratory of Drug Research and CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; School of Life Science and Technology, ShanghaiTech University, Shanghai, 200031, China
| | - Jian Ding
- State Key Laboratory of Drug Research and CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; University of Chinese Academy of Sciences, Beijing, 100049, China; School of Life Science and Technology, ShanghaiTech University, Shanghai, 200031, China
| | - Hong Liu
- State Key Laboratory of Drug Research and CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; University of Chinese Academy of Sciences, Beijing, 100049, China; School of Life Science and Technology, ShanghaiTech University, Shanghai, 200031, China
| | - Cheng Luo
- State Key Laboratory of Drug Research and CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Zuoquan Xie
- State Key Laboratory of Drug Research and CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Jiang Wang
- State Key Laboratory of Drug Research and CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
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Restoration of ceramide de novo synthesis by the synthetic retinoid ST1926 as it induces adult T-cell leukemia cell death. Biosci Rep 2021; 40:226649. [PMID: 33048123 PMCID: PMC7593536 DOI: 10.1042/bsr20200050] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 09/21/2020] [Accepted: 09/30/2020] [Indexed: 01/15/2023] Open
Abstract
Ceramide (Cer) is a bioactive cellular lipid with compartmentalized and tightly regulated levels. Distinct metabolic pathways lead to the generation of Cer species with distinguishable roles in oncogenesis. Deregulation of Cer pathways has emerged as an important mechanism for acquired chemotherapeutic resistance. Adult T-cell leukemia (ATL) cells are defective in Cer synthesis. ATL is an aggressive neoplasm that develops following infection with human T-cell lymphotropic virus-1 (HTLV-1) where the viral oncogene Tax contributes to the pathogenesis of the disease. ATL cells, resistant to all-trans-retinoic acid, are sensitive to pharmacologically achievable concentrations of the synthetic retinoid ST1926. We studied the effects of ST1926 on Cer pathways in ATL cells. ST1926 treatment resulted in early Tax oncoprotein degradation in HTLV-1-treated cells. ST1926 induced cell death and a dose- and time-dependent accumulation of Cer in malignant T cells. The kinetics and degree of Cer production showed an early response upon ST1926 treatment. ST1926 enhanced de novo Cer synthesis via activation of ceramide synthase CerS(s) without inhibiting dihydroceramide desaturase, thereby accumulating Cer rather than the less bioactive dihydroceramide. Using labeling experiments with the unnatural 17-carbon sphinganine and measuring the generated Cer species, we showed that ST1926 preferentially induces the activities of a distinct set of CerS(s). We detected a delay in cell death response and interruption of Cer generation in response to ST1926 in Molt-4 cells overexpressing Bcl-2. These results highlight the potential role of ST1926 in inducing Cer levels, thus lowering the threshold for cell death in ATL cells.
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9
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Canals D, Salamone S, Santacreu BJ, Aguilar D, Hernandez-Corbacho MJ, Ostermeyer-Fay AG, Greene M, Nemeth E, Haley JD, Obeid LM, Hannun YA. The doxorubicin-induced cell motility network is under the control of the ceramide-activated protein phosphatase 1 alpha. FASEB J 2021; 35:e21396. [PMID: 33583073 PMCID: PMC8220868 DOI: 10.1096/fj.202002427r] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 01/08/2021] [Accepted: 01/08/2021] [Indexed: 12/20/2022]
Abstract
We have recently reported that a specific pool of ceramide, located in the plasma membrane, mediated the effects of sublethal doses of the chemotherapeutic compound doxorubicin on enhancing cancer cell migration. We identified neutral sphingomyelinase 2 (nSMase2) as the enzyme responsible to generate this bioactive pool of ceramide. In this work, we explored the role of members of the protein phosphatases 1 family (PP1), and we identified protein phosphatase 1 alpha isoform (PP1 alpha) as the specific PP1 isoform to mediate this phenotype. Using a bioinformatics approach, we build a functional interaction network based on phosphoproteomics data on plasma membrane ceramide. This led to the identification of several ceramide-PP1 alpha downstream substrates. Studies on phospho mutants of ezrin (T567) and Scrib (S1378/S1508) demonstrated that their dephosphorylation is sufficient to enhance cell migration. In summary, we identified a mechanism where reduced doses of doxorubicin result in the dysregulation of cytoskeletal proteins and enhanced cell migration. This mechanism could explain the reported effects of doxorubicin worsening cancer metastasis in animal models.
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Affiliation(s)
- Daniel Canals
- Department of Medicine, Stony Brook University, Stony Brook, NY, USA
| | - Silvia Salamone
- Department of Medicine, Stony Brook University, Stony Brook, NY, USA
| | - Bruno Jaime Santacreu
- Department of Medicine, Stony Brook University, Stony Brook, NY, USA
- Facultad de Farmacia y Bioquimica, Catedra de Biologia Celular y Molecular, Buenos Aires, Argentina
| | - Daniel Aguilar
- Biomedical Research Networking Center in Hepatic and Digestive Diseases (CIBEREHD), Barcelona, Catalunya, Spain
| | | | | | - Meaghan Greene
- Department of Medicine, Stony Brook University, Stony Brook, NY, USA
| | - Erika Nemeth
- Department of Medicine, Stony Brook University, Stony Brook, NY, USA
| | - John D. Haley
- Department of Medicine, Stony Brook University, Stony Brook, NY, USA
- Department of Pathology, Stony Brook University, NY, USA
| | - Lina M. Obeid
- Department of Medicine, Stony Brook University, Stony Brook, NY, USA
- Northport VA Hospital, Northport, NY, USA
- Stony Brook Cancer Center, Stony Brook, NY, USA
| | - Yusuf A. Hannun
- Department of Medicine, Stony Brook University, Stony Brook, NY, USA
- Stony Brook Cancer Center, Stony Brook, NY, USA
- Department of Biochemistry, Stony Brook University, Stony Brook, NY, USA
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10
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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: 81] [Impact Index Per Article: 16.2] [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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11
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Zhao C, Zhu L, Li R, Wang H, Cai Z. Omics approach reveals metabolic disorders associated with the cytotoxicity of airborne particulate matter in human lung carcinoma cells. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2019; 246:45-52. [PMID: 30529940 DOI: 10.1016/j.envpol.2018.11.108] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 11/30/2018] [Accepted: 11/30/2018] [Indexed: 06/09/2023]
Abstract
Exposure to airborne particulate matter (PM) 2.5 induced various adverse health effects, such as metabolic syndrome, systemic inflammation and respiratory infection. However, a global influence of PM2.5-induced metabolic and proteomic disorders remains confusing, and the underlying mechanism is still under-explored. Herein, LC-MS/MS-based metabolomics, lipidomics and isobaric tags for relative and absolute quantification (iTRAQ)-based proteomics were applied to analyze the toxicological characteristics of PM2.5 from Taiyuan City in China (Taiyuan-PM2.5) on human lung carcinoma cells (A549) after the 24-h treatment. Metabolites, lipids and proteins that have distinctive differences were screened by SIEVE, LipidSearch and Proteome Discoverer, respectively. The abundance of 56 metabolites (40 increased and 16 decreased), 22 lipids (19 increased and 3 decreased) and 81 proteins (55 up-regulated and 26 down-regulated) were significantly changed upon the PM2.5 treatment. Among the proteomics analysis, 16 proteins were specifically related to RNA splicing, mainly including up-regulated serine/arginine-rich splicing factor 1 (SRSF1), SRSF2, small nuclear ribonucleoprotein 70 kDa (snRNP70), small nuclear ribonucleoprotein polypeptide B (SNRPB), SNRPC, SNRPE and down-regulated heterogeneous nuclear ribonucleoprotein U-like 2 (hnRNP UL2). At the metabolic level, PM2.5 exposure significantly altered the sphingolipid metabolism, including ceramide, serine, sphingosine and sphingomyelin. It was proposed that excessive accumulation of ceramide and expression of key enzymes (ceramide synthases, phingomyelinase, sphingosine kinase types 2 and protein phosphatase-1) induced the secretion of pro-inflammatory cytokines, generation of lipotoxicity and alterations of RNA splicing in PM2.5-treated A549 cells. In general, our results demonstrated that ceramide accumulation and altered RNA splicing could becritical contributors to PM2.5-induced cytotoxicity at metabolic and proteomic level, which might be considered as potential markers for toxicological evaluation of PM2.5 samples.
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Affiliation(s)
- Chao Zhao
- State Key Laboratory of Environmental and Biological Analysis, Department of Chemistry, Hong Kong Baptist University, Hong Kong, China; State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China
| | - Lin Zhu
- State Key Laboratory of Environmental and Biological Analysis, Department of Chemistry, Hong Kong Baptist University, Hong Kong, China
| | - Ruijin Li
- Institute of Environmental Science, Shanxi University, Taiyuan, China
| | - Hailin Wang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China
| | - Zongwei Cai
- State Key Laboratory of Environmental and Biological Analysis, Department of Chemistry, Hong Kong Baptist University, Hong Kong, China.
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12
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Black AJ, Schilder RJ, Kimball SR. Palmitate- and C6 ceramide-induced Tnnt3 pre-mRNA alternative splicing occurs in a PP2A dependent manner. Nutr Metab (Lond) 2018; 15:87. [PMID: 30564278 PMCID: PMC6296074 DOI: 10.1186/s12986-018-0326-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 12/10/2018] [Indexed: 12/24/2022] Open
Abstract
Background In a previous study, we showed that consumption of diets enriched in saturated fatty acids causes changes in alternative splicing of pre-mRNAs encoding a number of proteins in rat skeletal muscle, including the one encoding skeletal muscle Troponin T (Tnnt3). However, whether saturated fatty acids act directly on muscle cells to modulate alternative pre-mRNA splicing was not assessed. Moreover, the signaling pathway through which saturated fatty acids act to promote changes in alternative splicing is unknown. Therefore, the objective of the present study was to characterize the signaling pathway through which saturated fatty acids act to modulate Tnnt3 alternative splicing. Methods The effects of treatment of L6 myotubes with saturated (palmitate), mono- (oleate), or polyunsaturated (linoleate) fatty acids on alternative splicing of pre-mRNA was assessed using Tnnt3 as a marker gene. Results Palmitate treatment caused a two-fold change (p < 0.05) in L6 myotube Tnnt3 alternative splicing whereas treatment with either oleate or linoleate had minimal effects compared to control myotubes. Treatment with a downstream metabolite of palmitate, ceramide, had effects similar to palmitate on Tnnt3 alternative splicing and inhibition of de novo ceramide biosynthesis blocked the palmitate-induced alternative splicing changes. The effects of palmitate and ceramide on Tnnt3 alternative splicing were accompanied by a 40–50% reduction in phosphorylation of Akt on S473. However, inhibition of de novo ceramide biosynthesis did not prevent palmitate-induced Akt dephosphorylation, suggesting that palmitate may act in an Akt-independent manner to modulate Tnnt3 alternative splicing. Instead, pre-treatment with okadaic acid at concentrations that selectively inhibit protein phosphatase 2A (PP2A) blocked both palmitate- and ceramide-induced changes in Tnnt3 alternative splicing, suggesting that palmitate and ceramide act through PP2A to modulate Tnnt3 alternative splicing. Conclusions Overall, the data show that fatty acid saturation level and ceramides are important factors modulating alternative pre-mRNA splicing through activation of PP2A. Electronic supplementary material The online version of this article (10.1186/s12986-018-0326-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Adam J Black
- 1Department of Cellular and Molecular Physiology, Penn State College of Medicine, H166, 500 University Drive, Hershey, PA 17033 USA.,Present Address: Department of Cell Biology and Physiology, 6330 Medical Biomolecular Research Building, 111 Mason Farm Rd, Chapel Hill, NC 27599 USA
| | - Rudolf J Schilder
- 3Department of Entomology and Biology, Penn State University, University Park, PA USA
| | - Scot R Kimball
- 1Department of Cellular and Molecular Physiology, Penn State College of Medicine, H166, 500 University Drive, Hershey, PA 17033 USA
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Visualizing bioactive ceramides. Chem Phys Lipids 2018; 216:142-151. [PMID: 30266560 DOI: 10.1016/j.chemphyslip.2018.09.013] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 09/19/2018] [Accepted: 09/20/2018] [Indexed: 11/23/2022]
Abstract
In the last 30 years, ceramides have been found to mediate a myriad of biological processes. Ceramides have been recognized as bioactive molecules and their metabolizing enzymes are attractive targets in cancer therapy and other diseases. The molecular mechanism of action of cellular ceramides are still not fully established, with insights into roles through modification of lipid rafts, creation of ceramide platforms, ceramide channels, or through regulation of direct protein effectors such as protein phosphatases and kinases. Recently, the 'Many Ceramides' hypothesis focuses on distinct pools of subcellular ceramides and ceramide species as potential defined bioactive entities. Traditional methods that measure changes in ceramide levels in the whole cell, such as mass spectrometry, fluorescent ceramide analogues, and ceramide antibodies, fail to differentiate specific bioactive species at the subcellular level. However, a few ceramide binding proteins have been reported, and a smaller subgroup within these, have been shown to translocate to ceramide-enriched membranes, revealing these localized pools of bioactive ceramides. In this review we want to discuss and consolidate these works and explore the possibility of defining these binding proteins as new tools are emerging to visualize bioactive ceramides in cells. Our goal is to encourage the scientific community to explore these ceramide partners, to improve techniques to refine the list of these binding partners, making possible the identification of specific domains that recognize and bind ceramides to be used to visualize the 'Many Ceramides' in the cell.
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Sun Q, Li S, Li J, Fu Q, Wang Z, Li B, Liu SS, Su Z, Song J, Lu D. Homoharringtonine regulates the alternative splicing of Bcl-x and caspase 9 through a protein phosphatase 1-dependent mechanism. BMC COMPLEMENTARY AND ALTERNATIVE MEDICINE 2018; 18:164. [PMID: 29788973 PMCID: PMC5964699 DOI: 10.1186/s12906-018-2233-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Accepted: 05/15/2018] [Indexed: 12/31/2022]
Abstract
BACKGROUND Homoharringtonine (HHT) is a natural alkaloid with potent antitumor activity, but its precise mechanism of action is still poorly understood. METHODS We examined the effect of HHT on alternative splicing of Bcl-x and Caspase 9 in various cells using semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). The mechanism of HHT-affected alternative splicing in these cells was investigated by treatment with protein phosphatase inhibitors and overexpression of a protein phosphatase. RESULTS Treatment with HHT downregulated the levels of anti-apoptotic Bcl-xL and Caspase 9b mRNA with a concomitant increase in the mRNA levels of pro-apoptotic Bcl-xS and Caspase 9a in a dose- and time-dependent manner. Calyculin A, an inhibitor of protein phosphatase 1 (PP1) and protein phosphatase 2A (PP2A), significantly inhibited the effects of HHT on the alternative splicing of Bcl-x and Caspase 9, in contrast to okadaic acid, a specific inhibitor of PP2A. Overexpression of PP1 resulted in a decrease in the ratio of Bcl-xL/xS and an increase in the ratio of Caspase 9a/9b. Moreover, the effects of HHT on Bcl-x and Caspase 9 splicing were enhanced in response to PP1 overexpression. These results suggest that HHT-induced alternative splicing of Bcl-x and Caspase 9 is dependent on PP1 activation. In addition, overexpression of PP1 could induce apoptosis and sensitize MCF7 cells to apoptosis induced by HHT. CONCLUSION Homoharringtonine regulates the alternative splicing of Bcl-x and Caspase 9 through a PP1-dependent mechanism. Our study reveals a novel mechanism underlying the antitumor activities of HHT.
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15
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Zhou J, Chen J, Yu H. Targeting sphingosine kinase 2 by ABC294640 inhibits human skin squamous cell carcinoma cell growth. Biochem Biophys Res Commun 2018; 497:535-542. [PMID: 29428730 DOI: 10.1016/j.bbrc.2018.02.075] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Accepted: 02/07/2018] [Indexed: 12/12/2022]
Abstract
The activity of ABC294640, a small-molecular sphingosine kinase 2 (SphK2) inhibitor, in human skin squamous cell carcinoma (SCC) cells was tested in this study. SphK2 mRNA and protein are expressed in established (A431 cheilocarcinoma cell line) and primary human skin SCC cells. ABC294640 dose-dependently inhibited survival, cell cycle progression and proliferation of skin SCC cells. Furthermore, ABC294640 induced caspase-3/-9 and apoptosis activation in skin SCC cells. The SphK2 inhibitor was however non-cytotoxic to SphK2-null skin melanocytes, keratinocytes and fibroblasts. ABC294640 induced ceramide accumulation, sphingosine-1-phosphate (S1P) reduction, Akt-S6K1 inhibition and JNK activation in skin SCC cells. Conversely, its cytotoxicity against SCC cells was largely attenuated by co-treatment of S1P, the Akt activator SC79, and the JNK inhibitor SP600125. In vivo, ABC294640 oral administration inhibited A431 xenograft tumor growth in nude mice. Akt-S6K1 inhibition and JNK activation were observed in ABC294640-treated tumors. Collectively, ABC294640 efficiently inhibits human skin SCC cell growth in vitro and in vivo.
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Affiliation(s)
- Jianbo Zhou
- Dental Department, Yinzhou People's Hospital, Ningbo, Zhejiang 315040, China
| | - Jin Chen
- Dental Department, Yinzhou People's Hospital, Ningbo, Zhejiang 315040, China
| | - Huanmiao Yu
- Dental Department, Yinzhou People's Hospital, Ningbo, Zhejiang 315040, China.
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16
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Hage-Sleiman R, Hamze AB, El-Hed AF, Attieh R, Kozhaya L, Kabbani S, Dbaibo G. Ceramide inhibits PKCθ by regulating its phosphorylation and translocation to lipid rafts in Jurkat cells. Immunol Res 2017; 64:869-86. [PMID: 26798039 DOI: 10.1007/s12026-016-8787-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Protein kinase C theta (PKCθ) is a novel, calcium-independent member of the PKC family of kinases that was identified as a central player in T cell signaling and proliferation. Upon T cell activation by antigen-presenting cells, PKCθ gets phosphorylated and activated prior to its translocation to the immunological synapse where it couples with downstream effectors. PKCθ may be regulated by ceramide, a crucial sphingolipid that is known to promote differentiation, growth arrest, and apoptosis. To further investigate the mechanism, we stimulated human Jurkat T cells with either PMA or anti-CD3/anti-CD28 antibodies following induction of ceramide accumulation by adding exogenous ceramide, bacterial sphingomyelinase, or Fas ligation. Our results suggest that ceramide regulates the PKCθ pathway through preventing its critical threonine 538 (Thr538) phosphorylation and subsequent activation, thereby inhibiting the kinase's translocation to lipid rafts. Moreover, this inhibition is not likely to be a generic effect of ceramide on membrane reorganization. Other lipids, namely dihydroceramide, palmitate, and sphingosine, did not produce similar effects on PKCθ. Addition of the phosphatase inhibitors okadaic acid and calyculin A reversed the inhibition exerted by ceramide, and this suggests involvement of a ceramide-activated protein phosphatase. Such previously undescribed mechanism of regulation of PKCθ raises the possibility that ceramide, or one of its derivatives, and may prove valuable in novel therapeutic approaches for disorders involving autoimmunity or excessive inflammation-where PKCθ plays a critical role.
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Affiliation(s)
- Rouba Hage-Sleiman
- Department of Biology, Faculty of Sciences, Lebanese University, Hadath, Lebanon
| | - Asmaa B Hamze
- Department of Biomedical Science, Faculty of Health Sciences, Global University, Batrakiyye, Beirut, Lebanon
| | - Aimée F El-Hed
- Department of Pediatrics and Adolescent Medicine, Center for Infectious Diseases Research, Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, PO Box 11-0236 Riad El Solh, Beirut, Lebanon
| | - Randa Attieh
- Department of Pediatrics and Adolescent Medicine, Center for Infectious Diseases Research, Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, PO Box 11-0236 Riad El Solh, Beirut, Lebanon
| | - Lina Kozhaya
- Department of Pediatrics and Adolescent Medicine, Center for Infectious Diseases Research, Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, PO Box 11-0236 Riad El Solh, Beirut, Lebanon
| | - Sarah Kabbani
- Department of Pediatrics and Adolescent Medicine, Center for Infectious Diseases Research, Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, PO Box 11-0236 Riad El Solh, Beirut, Lebanon
| | - Ghassan Dbaibo
- Department of Pediatrics and Adolescent Medicine, Center for Infectious Diseases Research, Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, PO Box 11-0236 Riad El Solh, Beirut, Lebanon.
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17
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Alternative splicing and cell survival: from tissue homeostasis to disease. Cell Death Differ 2016; 23:1919-1929. [PMID: 27689872 DOI: 10.1038/cdd.2016.91] [Citation(s) in RCA: 125] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 05/26/2016] [Accepted: 07/15/2016] [Indexed: 12/17/2022] Open
Abstract
Most human genes encode multiple mRNA variants and protein products through alternative splicing of exons and introns during pre-mRNA processing. In this way, alternative splicing amplifies enormously the coding potential of the human genome and represents a powerful evolutionary resource. Nonetheless, the plasticity of its regulation is prone to errors and defective splicing underlies a large number of inherited and sporadic diseases, including cancer. One key cellular process affected by alternative splicing is the programmed cell death or apoptosis. Many apoptotic genes encode for splice variants having opposite roles in cell survival. This regulation modulates cell and tissue homeostasis and is implicated in both developmental and pathological processes. Furthermore, recent evidence has also unveiled splicing-mediated regulation of genes involved in autophagy, another essential process for tissue homeostasis. In this review, we highlight some of the best-known examples of alternative splicing events involved in cell survival. Emphasis is given to the role of this regulation in human cancer and in the response to chemotherapy, providing examples of how alternative splicing of apoptotic genes can be exploited therapeutically.
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18
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Jiang F, Jin K, Huang S, Bao Q, Shao Z, Hu X, Ye J. Liposomal C6 Ceramide Activates Protein Phosphatase 1 to Inhibit Melanoma Cells. PLoS One 2016; 11:e0159849. [PMID: 27631768 PMCID: PMC5025141 DOI: 10.1371/journal.pone.0159849] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2016] [Accepted: 07/09/2016] [Indexed: 02/02/2023] Open
Abstract
Melanoma is one common skin cancer. In the present study, the potential anti-melanoma activity by a liposomal C6 ceramide was tested in vitro. We showed that the liposomal C6 (ceramide) was cytotoxic and anti-proliferative against a panel of human melanoma cell lines (SK-Mel2, WM-266.4 and A-375 and WM-115). In addition, liposomal C6 induced caspase-dependent apoptotic death in the melanoma cells. Reversely, its cytotoxicity was attenuated by several caspase inhibitors. Intriguingly, liposomal C6 was non-cytotoxic to B10BR mouse melanocytes and primary human melanocytes. Molecularly, liposomal C6 activated protein phosphatase 1 (PP1) to inactivate Akt-mammalian target of rapamycin (mTOR) signaling in melanoma cells. On the other hand, PP1 shRNA knockdown or exogenous expression of constitutively activate Akt1 (CA-Akt1) restored Akt-mTOR activation and significantly attenuated liposomal C6-mediated cytotoxicity and apoptosis in melanoma cells. Our results suggest that liposomal C6 activates PP1 to inhibit melanoma cells.
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Affiliation(s)
- Fangzhen Jiang
- Department of Plastic and Reconstructive Surgery, the Second Affiliated Hospital of Zhejiang University, College of Medicine, Hangzhou, 310009, China
| | - Kai Jin
- Department of Ophthalmology, the Second Affiliated Hospital of Zhejiang University, College of Medicine, Hangzhou, 310009, China
- * E-mail:
| | - Shenyu Huang
- Department of Ophthalmology, the Second Affiliated Hospital of Zhejiang University, College of Medicine, Hangzhou, 310009, China
| | - Qi Bao
- Department of Plastic and Reconstructive Surgery, the Second Affiliated Hospital of Zhejiang University, College of Medicine, Hangzhou, 310009, China
| | - Zheren Shao
- Department of Plastic and Reconstructive Surgery, the Second Affiliated Hospital of Zhejiang University, College of Medicine, Hangzhou, 310009, China
| | - Xueqing Hu
- Department of Plastic and Reconstructive Surgery, the Second Affiliated Hospital of Zhejiang University, College of Medicine, Hangzhou, 310009, China
| | - Juan Ye
- Department of Ophthalmology, the Second Affiliated Hospital of Zhejiang University, College of Medicine, Hangzhou, 310009, China
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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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Li Y, Yuan Y. Alternative RNA splicing and gastric cancer. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2016; 773:263-273. [PMID: 28927534 DOI: 10.1016/j.mrrev.2016.07.011] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Revised: 07/06/2016] [Accepted: 07/28/2016] [Indexed: 02/07/2023]
Abstract
Alternative splicing (AS) linked to diseases, especially to tumors. Recently, more and more studies focused on the relationship between AS and gastric cancer (GC). This review surveyed the hot topic from four aspects: First, the common types of AS in cancer, including exon skipping, intron retention, mutually exclusive exon, alternative 5 ' or 3' splice site, alternative first or last exon and alternative 3' untranslated regions. Second, basic mechanisms of AS and its relationship with cancer. RNA splicing in eukaryotes follows the GT-AG rule by both cis-elements and trans-acting factors regulatory. Through RNA splicing, different proteins with different forms and functions can be produced and may be associated with carcinogenesis. Third, AS types of GC-related genes and their splicing variants. In this paper, we listed 10 common genes with AS and illustrated its possible molecular mechanisms owing to genetic variation (mutation and /or polymorphism). Fourth, the splicing variants of GC-associated genes and gastric carcinogenesis, invasion and metastasis. Many studies have found that the different splicing variants of the same gene are differentially expressed in GC and its precancerous diseases, suggesting AS has important implications in GC development. Taking together, this review highlighted the role of AS and splicing variants in the process of GC. We hope that this is not only beneficial to advances in the study field of GC, but also can provide valuable information to other similar tumor research.Although we already know some gene splicing and splicing variants play an important role in the development of GC, but many phenomena and mechanisms are still unknown. For example, how the tumor microenvironment and signal transduction pathway effect the forming and function of AS? Unfortunately, this review did not cover the contents because the current study is limited. It is no doubt that clarifying the phenomena and mechanisms of these unknown may help to reveal the relationship of AS with complex tumor genetic variation and the occurrence and development of tumors.
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Affiliation(s)
- Ying Li
- Tumor Etiology and Screening Department of Cancer Institute and General Surgery, The First Affiliated Hospital of China Medical University, Key Laboratory of Cancer Etiology and Prevention (China Medical University), Liaoning Provincial Education Department, Shenyang 110001, China
| | - Yuan Yuan
- Tumor Etiology and Screening Department of Cancer Institute and General Surgery, The First Affiliated Hospital of China Medical University, Key Laboratory of Cancer Etiology and Prevention (China Medical University), Liaoning Provincial Education Department, Shenyang 110001, China.
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21
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Towards understanding pre-mRNA splicing mechanisms and the role of SR proteins. Gene 2016; 587:107-19. [PMID: 27154819 DOI: 10.1016/j.gene.2016.04.057] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 04/30/2016] [Indexed: 01/04/2023]
Abstract
Alternative pre-mRNA splicing provides a source of vast protein diversity by removing non-coding sequences (introns) and accurately linking different exonic regions in the correct reading frame. The regulation of alternative splicing is essential for various cellular functions in both pathological and physiological conditions. In eukaryotic cells, this process is commonly used to increase proteomic diversity and to control gene expression either co- or post-transcriptionally. Alternative splicing occurs within a megadalton-sized, multi-component machine consisting of RNA and proteins; during the splicing process, this complex undergoes dynamic changes via RNA-RNA, protein-protein and RNA-protein interactions. Co-transcriptional splicing functionally integrates the transcriptional machinery, thereby enabling the two processes to influence one another, whereas post-transcriptional splicing facilitates the coupling of RNA splicing with post-splicing events. This review addresses the structural aspects of spliceosomes and the mechanistic implications of their stepwise assembly on the regulation of pre-mRNA splicing. Moreover, the role of phosphorylation-based, signal-induced changes in the regulation of the splicing process is demonstrated.
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The Role of Alternative Splicing in the Control of Immune Homeostasis and Cellular Differentiation. Int J Mol Sci 2015; 17:ijms17010003. [PMID: 26703587 PMCID: PMC4730250 DOI: 10.3390/ijms17010003] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2015] [Revised: 12/11/2015] [Accepted: 12/15/2015] [Indexed: 12/21/2022] Open
Abstract
Alternative splicing of pre-mRNA helps to enhance the genetic diversity within mammalian cells by increasing the number of protein isoforms that can be generated from one gene product. This provides a great deal of flexibility to the host cell to alter protein function, but when dysregulation in splicing occurs this can have important impact on health and disease. Alternative splicing is widely used in the mammalian immune system to control the development and function of antigen specific lymphocytes. In this review we will examine the splicing of pre-mRNAs yielding key proteins in the immune system that regulate apoptosis, lymphocyte differentiation, activation and homeostasis, and discuss how defects in splicing can contribute to diseases. We will describe how disruption to trans-acting factors, such as heterogeneous nuclear ribonucleoproteins (hnRNPs), can impact on cell survival and differentiation in the immune system.
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Abstract
Studies over the past two decades have identified ceramide as a multifunctional central molecule in the sphingolipid biosynthetic pathway. Given its diverse tumor suppressive activities, molecular understanding of ceramide action will produce fundamental insights into processes that limit tumorigenesis and may identify key molecular targets for therapeutic intervention. Ceramide can be activated by a diverse array of stresses such as heat shock, genotoxic damage, oxidative stress and anticancer drugs. Ceramide triggers a variety of tumor suppressive and anti-proliferative cellular programs such as apoptosis, autophagy, senescence, and necroptosis by activating or repressing key effector molecules. Defects in ceramide generation and metabolism in cancer contribute to tumor cell survival and resistance to chemotherapy. The potent and versatile anticancer activity profile of ceramide has motivated drug development efforts to (re-)activate ceramide in established tumors. This review focuses on our current understanding of the tumor suppressive functions of ceramide and highlights the potential downstream targets of ceramide which are involved in its tumor suppressive action.
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Functional Consequences for Apoptosis by Transcription Elongation Regulator 1 (TCERG1)-Mediated Bcl-x and Fas/CD95 Alternative Splicing. PLoS One 2015; 10:e0139812. [PMID: 26462236 PMCID: PMC4604205 DOI: 10.1371/journal.pone.0139812] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Accepted: 09/17/2015] [Indexed: 11/19/2022] Open
Abstract
Here, we present evidence for a specific role of the splicing-related factor TCERG1 in regulating apoptosis in live cells by modulating the alternative splicing of the apoptotic genes Bcl-x and Fas. We show that TCERG1 modulates Bcl-x alternative splicing during apoptosis and its activity in Bcl-x alternative splicing correlates with the induction of apoptosis, as determined by assessing dead cells, sub-G1-phase cells, annexin-V binding, cell viability, and cleavage of caspase-3 and PARP-1. Furthermore, the effect of TCERG1 on apoptosis involved changes in mitochondrial membrane permeabilization. We also found that depletion of TCERG1 reduces the expression of the activated form of the pro-apoptotic mitochondrial membrane protein Bak, which remains inactive by heterodimerizing with Bcl-xL, preventing the initial step of cytochrome c release in Bak-mediated mitochondrial apoptosis. In addition, we provide evidence that TCERG1 also participates in the death receptor-mediated apoptosis pathway. Interestingly, TCERG1 also modulates Fas/CD95 alternative splicing. We propose that TCERG1 sensitizes a cell to apoptotic agents, thus promoting apoptosis by regulating the alternative splicing of both the Bcl-x and Fas/CD95 genes. Our findings may provide a new link between the control of alternative splicing and the molecular events leading to apoptosis.
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Lysosomal ceramide generated by acid sphingomyelinase triggers cytosolic cathepsin B-mediated degradation of X-linked inhibitor of apoptosis protein in natural killer/T lymphoma cell apoptosis. Cell Death Dis 2015; 6:e1717. [PMID: 25855965 PMCID: PMC4650549 DOI: 10.1038/cddis.2015.82] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 02/20/2015] [Accepted: 02/23/2015] [Indexed: 02/07/2023]
Abstract
We previously reported that IL-2 deprivation induced acid sphingomyelinase-mediated (ASM-mediated) ceramide elevation and apoptosis in an NK/T lymphoma cell line KHYG-1. However, the molecular mechanism of ASM–ceramide-mediated apoptosis during IL-2 deprivation is poorly understood. Here, we showed that IL-2 deprivation induces caspase-dependent apoptosis characterized by phosphatidylserine externalization, caspase-8, -9, and -3 cleavage, and degradation of X-linked inhibitor of apoptosis protein (XIAP). IL-2 re-supplementation rescued apoptosis via inhibition of XIAP degradation without affecting caspase cleavage. However, IL-2 deprivation induced ceramide elevation via ASM in lysosomes and activated lysosomal cathepsin B (CTSB) but not cathepsin D. A CTSB inhibitor CA-074 Me and knockdown of CTSB inhibited ceramide-mediated XIAP degradation and apoptosis. Inhibition of ceramide accumulation in lysosomes using an ASM inhibitor, desipramine, decreased cytosolic activation of CTSB by inhibiting its transfer into cytosol from the lysosome. Knockdown of ASM also inhibited XIAP degradation and apoptosis. Furthermore, cell permeable N-acetyl sphingosine (C2-ceramide), which increases mainly endogenous d18:1/16:0 and d18:1/24:1 ceramide-like IL-2 deprivation, induced caspase-dependent apoptosis with XIAP degradation through CTSB. These findings suggest that lysosomal ceramide produced by ASM mediates XIAP degradation by activation of cytosolic CTSB and caspase-dependent apoptosis. The ASM–ceramide–CTSB signaling axis is a novel pathway of ceramide-mediated apoptosis in IL-2-deprived NK/T lymphoma cells.
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Regulation of ceramide channel formation and disassembly: Insights on the initiation of apoptosis. Saudi J Biol Sci 2015; 22:760-72. [PMID: 26587005 PMCID: PMC4625378 DOI: 10.1016/j.sjbs.2015.03.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 03/12/2015] [Accepted: 03/15/2015] [Indexed: 01/04/2023] Open
Abstract
Sphingolipid research has surged in the past two decades and has produced a wide variety of evidence supporting the role of this class of molecules in mediating cellular growth, differentiation, senescence, and apoptosis. Ceramides are a subgroup of sphingolipids (SLs) that are directly involved in the process of initiation of apoptosis. We, and others, have recently shown that ceramides are capable of the formation of protein-permeable channels in mitochondrial outer membranes under physiological conditions. These pores are indeed good candidates for the pathway of release of pro-apoptotic proteins from the mitochondrial intermembrane space (IMS) into the cytosol to initiate intrinsic apoptosis. Here, we review recent findings on the regulation of ceramide channel formation and disassembly, highlighting possible implications on the initiation of the intrinsic apoptotic pathway.
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Key Words
- Apoptosis
- Assembly and disassembly
- Bcl-2 family proteins
- Bcl-2, B cell CLL/lymphoma-2
- Cer, ceramide
- CerS, ceramide synthase
- Ceramide channels
- Chain length
- DES, dihydroceramide desaturase
- DHCer, dihydroceramide
- ER, endoplasmic reticulum
- IMS, intermembrane space
- KSR, 3-ketosphinganine reductase
- MOMP, mitochondrial outer membrane permeability
- Mitochondria
- SLs, sphingolipids
- SM, sphingomyelin
- SPT, serine palmitoyl transferase
- So, sphingosine
- Sphingolipids
- de novo synthesis
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Dany M, Ogretmen B. Ceramide induced mitophagy and tumor suppression. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:2834-45. [PMID: 25634657 DOI: 10.1016/j.bbamcr.2014.12.039] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Revised: 12/09/2014] [Accepted: 12/25/2014] [Indexed: 12/11/2022]
Abstract
Sphingolipids are bioactive lipid effectors, which are involved in the regulation of various cellular signaling pathways. Sphingolipids play essential roles in controlling cell inflammation, proliferation, death, migration, senescence, metastasis and autophagy. Alterations in sphingolipid metabolism have been also implicated in many human cancers. Macroautophagy (referred to here as autophagy) is a form of nonselective sequestering of cytosolic materials by double membrane structures, autophagosomes, which can be either protective or lethal for cells. Ceramide, a central molecule of sphingolipid metabolism is involved in the regulation of autophagy at various levels, including the induction of lethal mitophagy, a selective autophagy process to target and eliminate damaged mitochondria. In this review, we focused on recent studies with regard to the regulation of autophagy, in particular lethal mitophagy, by ceramide, and aimed at providing discussion points for various context-dependent roles and mechanisms of action of ceramide in controlling mitophagy.
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Affiliation(s)
- Mohammed Dany
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA; Hollings Cancer Center, Medical University of South Carolina, 86 Jonathan Lucas Street, Charleston, SC 29425, USA
| | - Besim Ogretmen
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA; Hollings Cancer Center, Medical University of South Carolina, 86 Jonathan Lucas Street, Charleston, SC 29425, USA.
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Rodriguez-Cuenca S, Barbarroja N, Vidal-Puig A. Dihydroceramide desaturase 1, the gatekeeper of ceramide induced lipotoxicity. Biochim Biophys Acta Mol Cell Biol Lipids 2015; 1851:40-50. [DOI: 10.1016/j.bbalip.2014.09.021] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Revised: 09/24/2014] [Accepted: 09/25/2014] [Indexed: 12/25/2022]
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Ceramide modulates pre-mRNA splicing to restore the expression of wild-type tumor suppressor p53 in deletion-mutant cancer cells. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1841:1571-80. [PMID: 25195822 DOI: 10.1016/j.bbalip.2014.08.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 07/25/2014] [Accepted: 08/27/2014] [Indexed: 11/20/2022]
Abstract
Mutants of tumor suppressor p53 not only lose the activity in genome stabilizing and in tumor suppression, but also exhibit oncogenic function in cancer cells. Most efforts in restoring p53 biological activity focus on either altering mutant-protein conformation or introducing an exogenous p53 gene into cells to eliminate p53-mutant cancer cells. Being different from these, we report that ceramide can restore the expression of wild-type p53 and induce p53-dependent apoptosis in deletion-mutant cancer cells. We show that endogenous long-carbon chain ceramide species (C16- to C24-ceramides) and exogenous C6-ceramide, rather than other sphingolipids, restore wild-type mRNA (intact exon-5), phosphorylated protein (Ser15 in exon-5) of p53, and p53-responsive proteins, including p21 and Bax, in ovarian cancer cells, which predominantly express a deleted exon-5 of p53 mutant before treatments. Consequently, the restored p53 sensitizes these p53-mutant cancer cells to DNA damage-induced growth arrest and apoptosis. Furthermore, we elucidate that ceramide activates protein phosphatase-1, and then the dephosphorylated serine/arginine-rich splicing-factor 1 (SRSF1) is translocated to the nucleus, thus promoting pre-mRNA splicing preferentially to wild-type p53 expression. These findings disclose an unrecognized mechanism that pre-mRNA splicing dysfunction can result in p53 deletion-mutants. Ceramide through SRSF1 restores wild-type p53 expression versus deletion-mutant and leads cancer cells to apoptosis. This suggests that heterozygous deletion-mutants of p53 can be restored in posttranscriptional level by using epigenetic approaches.
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Choi DB, Park MR, Kim HR, Jun CD, Kim HJ, Shim H, Kim YD, Choi C, Choi KH, Yun KJ, Chae SC, Park R, Choe SK, Lee YJ, Park DS. Aberrant proteomic expression of NSRP70 and its clinical implications and connection to the transcriptional level in adult acute leukemia. Leuk Res 2014; 38:1252-9. [PMID: 25176346 DOI: 10.1016/j.leukres.2014.08.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Revised: 08/02/2014] [Accepted: 08/03/2014] [Indexed: 11/30/2022]
Abstract
We investigated three splicing factor proteins (SFPs; NSRP70, SRSF1, and HNRNPA1) in 187 adults with and without acute leukemia (AL). We showed that NSRP70 is a novel lymphoblastic AL (ALL) surrogate marker, which presented excellent diagnostic accuracy (92%) and disappeared during remission. Its highest molecular weight form, but not total amount, was associated with adverse genetic abnormalities in myeloid AL (AML). Furthermore, we identified that these SFPs were more prevalent in ALL than in AML; were not correlated with their mRNA levels; and their formations in AL may occur without coding mutations and relate to post-translational modifications.
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Affiliation(s)
- Dan-Bee Choi
- Department of Laboratory Medicine, School of Medicine, Wonkwang University, Iksan, Republic of Korea; Center for Metabolic Function Regulation, Institute of Wonkwang Medical Science and Institute of Wonkwang Clinical Medicine, Wonkwang University, Iksan, Republic of Korea
| | - Moo-Rim Park
- Department of Internal Medicine, School of Medicine, Wonkwang University, Iksan, Republic of Korea
| | - Hak-Ryul Kim
- Department of Internal Medicine, School of Medicine, Wonkwang University, Iksan, Republic of Korea
| | - Chang-Duk Jun
- School of Life Sciences, Immune Synapse Research Center and Cell Dynamics Research Center, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea
| | - Hyeoung-Joon Kim
- Department of Internal Medicine and Genome Research Center for Hematopoietic Diseases, Chonnam National University Hwasun Hospital, Hwasun-gun, Republic of Korea
| | - Hyeok Shim
- Department of Internal Medicine, School of Medicine, Wonkwang University, Iksan, Republic of Korea
| | - Young-Dae Kim
- School of Life Sciences, Immune Synapse Research Center and Cell Dynamics Research Center, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea
| | - Chan Choi
- Department of Pathology and Genome Research Center for Hematopoietic Diseases, Chonnam National University Hwasun Hospital, Hwasun-gun, Republic of Korea
| | - Keum-Ha Choi
- Department of Pathology, School of Medicine, Wonkwang University, Iksan, Republic of Korea
| | - Ki Jung Yun
- Department of Pathology, School of Medicine, Wonkwang University, Iksan, Republic of Korea
| | - Soo-Cheon Chae
- Department of Pathology, School of Medicine, Wonkwang University, Iksan, Republic of Korea
| | - Raekil Park
- Center for Metabolic Function Regulation, Institute of Wonkwang Medical Science and Institute of Wonkwang Clinical Medicine, Wonkwang University, Iksan, Republic of Korea; Department of Microbiology, School of Medicine, Wonkwang University, Iksan, Republic of Korea
| | - Seong-Kyu Choe
- Center for Metabolic Function Regulation, Institute of Wonkwang Medical Science and Institute of Wonkwang Clinical Medicine, Wonkwang University, Iksan, Republic of Korea; Department of Microbiology, School of Medicine, Wonkwang University, Iksan, Republic of Korea
| | - Young-Jin Lee
- Department of Laboratory Medicine, School of Medicine, Wonkwang University, Iksan, Republic of Korea
| | - Do-Sim Park
- Department of Laboratory Medicine, School of Medicine, Wonkwang University, Iksan, Republic of Korea; Center for Metabolic Function Regulation, Institute of Wonkwang Medical Science and Institute of Wonkwang Clinical Medicine, Wonkwang University, Iksan, Republic of Korea.
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He Q, Wang G, Wakade S, Dasgupta S, Dinkins M, Kong JN, Spassieva SD, Bieberich E. Primary cilia in stem cells and neural progenitors are regulated by neutral sphingomyelinase 2 and ceramide. Mol Biol Cell 2014; 25:1715-29. [PMID: 24694597 PMCID: PMC4038499 DOI: 10.1091/mbc.e13-12-0730] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Human embryonic stem and induced pluripotent stem cell–derived neuroprogenitors (NPs) develop primary cilia. Ciliogenesis depends on the sphingolipid ceramide and its interaction with atypical PKC, both of which distribute to the primary cilium and the apicolateral cell membrane in NP rosettes. We show here that human embryonic stem (ES) and induced pluripotent stem cell–derived neuroprogenitors (NPs) develop primary cilia. Ciliogenesis depends on the sphingolipid ceramide and its interaction with atypical PKC (aPKC), both of which distribute to the primary cilium and the apicolateral cell membrane in NP rosettes. Neural differentiation of human ES cells to NPs is concurrent with a threefold elevation of ceramide—in particular, saturated, long-chain C16:0 ceramide (N-palmitoyl sphingosine) and nonsaturated, very long chain C24:1 ceramide (N-nervonoyl sphingosine). Decreasing ceramide levels by inhibiting ceramide synthase or neutral sphingomyelinase 2 leads to translocation of membrane-bound aPKC to the cytosol, concurrent with its activation and the phosphorylation of its substrate Aurora kinase A (AurA). Inhibition of aPKC, AurA, or a downstream target of AurA, HDAC6, restores ciliogenesis in ceramide-depleted cells. Of importance, addition of exogenous C24:1 ceramide reestablishes membrane association of aPKC, restores primary cilia, and accelerates neural process formation. Taken together, these results suggest that ceramide prevents activation of HDAC6 by cytosolic aPKC and AurA, which promotes acetylation of tubulin in primary cilia and, potentially, neural processes. This is the first report on the critical role of ceramide generated by nSMase2 in stem cell ciliogenesis and differentiation.
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Affiliation(s)
- Qian He
- Program in Developmental Neurobiology, Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Georgia Regents University, Augusta, GA 30912
| | - Guanghu Wang
- Program in Developmental Neurobiology, Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Georgia Regents University, Augusta, GA 30912
| | - Sushama Wakade
- Program in Developmental Neurobiology, Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Georgia Regents University, Augusta, GA 30912
| | - Somsankar Dasgupta
- Program in Developmental Neurobiology, Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Georgia Regents University, Augusta, GA 30912
| | - Michael Dinkins
- Program in Developmental Neurobiology, Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Georgia Regents University, Augusta, GA 30912
| | - Ji Na Kong
- Program in Developmental Neurobiology, Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Georgia Regents University, Augusta, GA 30912
| | - Stefka D Spassieva
- Division of Hematology/Oncology, Department of Medicine, Medical University of South Carolina, Charleston, SC 29425
| | - Erhard Bieberich
- Program in Developmental Neurobiology, Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Georgia Regents University, Augusta, GA 30912
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Giussani P, Tringali C, Riboni L, Viani P, Venerando B. Sphingolipids: key regulators of apoptosis and pivotal players in cancer drug resistance. Int J Mol Sci 2014; 15:4356-92. [PMID: 24625663 PMCID: PMC3975402 DOI: 10.3390/ijms15034356] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 02/07/2014] [Accepted: 02/21/2014] [Indexed: 12/17/2022] Open
Abstract
Drug resistance elicited by cancer cells still constitutes a huge problem that frequently impairs the efficacy of both conventional and novel molecular therapies. Chemotherapy usually acts to induce apoptosis in cancer cells; therefore, the investigation of apoptosis control and of the mechanisms used by cancer cells to evade apoptosis could be translated in an improvement of therapies. Among many tools acquired by cancer cells to this end, the de-regulated synthesis and metabolism of sphingolipids have been well documented. Sphingolipids are known to play many structural and signalling roles in cells, as they are involved in the control of growth, survival, adhesion, and motility. In particular, in order to increase survival, cancer cells: (a) counteract the accumulation of ceramide that is endowed with pro-apoptotic potential and is induced by many drugs; (b) increase the synthesis of sphingosine-1-phosphate and glucosylceramide that are pro-survivals signals; (c) modify the synthesis and the metabolism of complex glycosphingolipids, particularly increasing the levels of modified species of gangliosides such as 9-O acetylated GD3 (αNeu5Ac(2-8)αNeu5Ac(2-3)βGal(1-4)βGlc(1-1)Cer) or N-glycolyl GM3 (αNeu5Ac (2-3)βGal(1-4)βGlc(1-1)Cer) and de-N-acetyl GM3 (NeuNH(2)βGal(1-4)βGlc(1-1)Cer) endowed with anti-apoptotic roles and of globoside Gb3 related to a higher expression of the multidrug resistance gene MDR1. In light of this evidence, the employment of chemical or genetic approaches specifically targeting sphingolipid dysregulations appears a promising tool for the improvement of current chemotherapy efficacy.
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Affiliation(s)
- Paola Giussani
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Segrate (Milan 20090), Italy.
| | - Cristina Tringali
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Segrate (Milan 20090), Italy.
| | - Laura Riboni
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Segrate (Milan 20090), Italy.
| | - Paola Viani
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Segrate (Milan 20090), Italy.
| | - Bruno Venerando
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Segrate (Milan 20090), Italy.
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C6-ceramide nanoliposomes target the Warburg effect in chronic lymphocytic leukemia. PLoS One 2013; 8:e84648. [PMID: 24367685 PMCID: PMC3868606 DOI: 10.1371/journal.pone.0084648] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Accepted: 11/26/2013] [Indexed: 11/19/2022] Open
Abstract
Ceramide is a sphingolipid metabolite that induces cancer cell death. When C6-ceramide is encapsulated in a nanoliposome bilayer formulation, cell death is selectively induced in tumor models. However, the mechanism underlying this selectivity is unknown. As most tumors exhibit a preferential switch to glycolysis, as described in the "Warburg effect", we hypothesize that ceramide nanoliposomes selectively target this glycolytic pathway in cancer. We utilize chronic lymphocytic leukemia (CLL) as a cancer model, which has an increased dependency on glycolysis. In CLL cells, we demonstrate that C6-ceramide nanoliposomes, but not control nanoliposomes, induce caspase 3/7-independent necrotic cell death. Nanoliposomal ceramide inhibits both the RNA and protein expression of GAPDH, an enzyme in the glycolytic pathway, which is overexpressed in CLL. To confirm that ceramide targets GAPDH, we demonstrate that downregulation of GAPDH potentiates the decrease in ATP after ceramide treatment and exogenous pyruvate treatment as well as GAPDH overexpression partially rescues ceramide-induced necrosis. Finally, an in vivo murine model of CLL shows that nanoliposomal C6-ceramide treatment elicits tumor regression, concomitant with GAPDH downregulation. We conclude that selective inhibition of the glycolytic pathway in CLL cells with nanoliposomal C6-ceramide could potentially be an effective therapy for leukemia by targeting the Warburg effect.
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Abstract
Ceramide, a bioactive sphingolipid, is now at the forefront of cancer research. Classically, ceramide is thought to induce death, growth inhibition, and senescence in cancer cells. However, it is now clear that this simple picture of ceramide no longer holds true. Recent studies suggest that there are diverse functions of endogenously generated ceramides, which seem to be context dependent, regulated by subcellular/membrane localization and presence/absence of direct targets of these lipid molecules. For example, different fatty-acid chain lengths of ceramide, such as C(16)-ceramide that can be generated by ceramide synthase 6 (CerS6), have been implicated in cancer cell proliferation, whereas CerS1-generated C(18)-ceramide mediates cell death. The dichotomy of ceramides' function in cancer cells makes some of the metabolic enzymes of ceramide synthesis potential drug targets (such as Cers6) to prevent cancer growth in breast and head and neck cancers. Conversely, activation of CerS1 could be a new therapeutic option for the development of novel strategies against lung and head and neck cancers. This chapter focuses on recent discoveries about the mechanistic details of mainly de novo-generated ceramides and their signaling functions in cancer pathogenesis, and about how these mechanistic information can be translated into clinically relevant therapeutic options for the treatment of cancer.
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Bhat-Nakshatri P, Song EK, Collins NR, Uversky VN, Dunker AK, O'Malley BW, Geistlinger TR, Carroll JS, Brown M, Nakshatri H. Interplay between estrogen receptor and AKT in estradiol-induced alternative splicing. BMC Med Genomics 2013; 6:21. [PMID: 23758675 PMCID: PMC3687557 DOI: 10.1186/1755-8794-6-21] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Accepted: 06/03/2013] [Indexed: 02/07/2023] Open
Abstract
Background Alternative splicing is critical for generating complex proteomes in response to extracellular signals. Nuclear receptors including estrogen receptor alpha (ERα) and their ligands promote alternative splicing. The endogenous targets of ERα:estradiol (E2)-mediated alternative splicing and the influence of extracellular kinases that phosphorylate ERα on E2-induced splicing are unknown. Methods MCF-7 and its anti-estrogen derivatives were used for the majority of the assays. CD44 mini gene was used to measure the effect of E2 and AKT on alternative splicing. ExonHit array analysis was performed to identify E2 and AKT-regulated endogenous alternatively spliced apoptosis-related genes. Quantitative reverse transcription polymerase chain reaction was performed to verify alternative splicing. ERα binding to alternatively spliced genes was verified by chromatin immunoprecipitation assay. Bromodeoxyuridine incorporation-ELISA and Annexin V labeling assays were done to measure cell proliferation and apoptosis, respectively. Results We identified the targets of E2-induced alternative splicing and deconstructed some of the mechanisms surrounding E2-induced splicing by combining splice array with ERα cistrome and gene expression array. E2-induced alternatively spliced genes fall into at least two subgroups: coupled to E2-regulated transcription and ERα binding to the gene without an effect on rate of transcription. Further, AKT, which phosphorylates both ERα and splicing factors, influenced ERα:E2 dependent splicing in a gene-specific manner. Genes that are alternatively spliced include FAS/CD95, FGFR2, and AXIN-1. E2 increased the expression of FGFR2 C1 isoform but reduced C3 isoform at mRNA level. E2-induced alternative splicing of FAS and FGFR2 in MCF-7 cells correlated with resistance to FAS activation-induced apoptosis and response to keratinocyte growth factor (KGF), respectively. Resistance of MCF-7 breast cancer cells to the anti-estrogen tamoxifen was associated with ERα-dependent overexpression of FGFR2, whereas resistance to fulvestrant was associated with ERα-dependent isoform switching, which correlated with altered response to KGF. Conclusion E2 may partly alter cellular proteome through alternative splicing uncoupled to its effects on transcription initiation and aberration in E2-induced alternative splicing events may influence response to anti-estrogens.
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Affiliation(s)
- Poornima Bhat-Nakshatri
- Department of Surgery, Indiana University School of Medicine, 980 West Walnut Street, Indianapolis, IN 46202, USA
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Hara H, Takeda T, Yamamoto N, Furuya K, Hirose K, Kamiya T, Adachi T. Zinc-induced modulation of SRSF6 activity alters Bim splicing to promote generation of the most potent apoptotic isoform BimS. FEBS J 2013; 280:3313-27. [PMID: 23648111 DOI: 10.1111/febs.12318] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Revised: 04/25/2013] [Accepted: 04/29/2013] [Indexed: 12/12/2022]
Abstract
Bim is a member of the pro-apoptotic BH3-only Bcl-2 family of proteins. Bim gene undergoes alternative splicing to produce three predominant splicing variants (BimEL, BimL and BimS). The smallest variant BimS is the most potent inducer of apoptosis. Zinc (Zn(2+)) has been reported to stimulate apoptosis in various cell types. In this study, we examined whether Zn(2+) affects the expression of Bim in human neuroblastoma SH-SY5Y cells. Zn(2+) triggered alterations in Bim splicing and induced preferential generation of BimS, but not BimEL and BimL, in a dose- and time-dependent manner. Other metals (cadmium, cobalt and copper) and stresses (oxidative, endoplasmic reticulum and genotoxic stresses) had little or no effect on the expression of BimS. To address the mechanism of Zn(2+)-induced preferential generation of BimS, which lacks exon 4, we developed a Bim mini-gene construct. Deletion analysis using the Bim mini-gene revealed that predicted binding sites of the SR protein SRSF6, also known as SRp55, are located in the intronic region adjacent to exon 4. We also found that mutations in the predicted SRSF6-binding sites abolished generation of BimS mRNA from the mutated Bim mini-gene. In addition, a UV cross-linking assay followed by Western blotting showed that SRSF6 directly bound to the predicted binding site and Zn(2+) suppressed this binding. Moreover, Zn(2+) stimulated SRSF6 hyper-phosphorylation. TG003, a cdc2-like kinase inhibitor, partially prevented Zn(2+)-induced generation of BimS and SRSF6 hyper-phosphorylation. Taken together, our findings suggest that Zn(2+) inhibits the activity of SRSF6 and promotes elimination of exon 4, leading to preferential generation of BimS.
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Affiliation(s)
- Hirokazu Hara
- Laboratory of Clinical Pharmaceutics, Gifu Pharmaceutical University, Gifu, Japan.
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Abstract
Acid sphingomyelinase (ASM) is a lipid hydrolase that cleaves the sphingolipid, sphingomyelin, into ceramide. Mutations in the ASM gene (SMPD1) result in the rare lysosomal storage disorder, Niemann-Pick disease (NPD). In addition to its role in NPD, over the past two decades, the importance of sphingolipids, and ASM in particular, in normal physiology and the pathophysiology of numerous common diseases also has become known. For example, altered sphingolipid metabolism occurs in many cancers, generally reducing the levels of the pro-apoptotic lipid, ceramide, and/or elevating the levels of the proliferative lipid, sphingosine-1-phosphate (S1P). These changes likely contribute to the tumorigenicity and/or metastatic capacity of the cancer. In addition, many cancer therapies induce ceramide-mediated death, and cancer cells have evolved novel mechanisms to overcome this effect. In the present review, we discuss sphingolipid metabolism in cancer, and specifically the potential for pharmacological modulation using ASM. Of note, recombinant human ASM (rhASM) has been produced for human use and is being evaluated as a treatment for NPD. Thus, its use for cancer therapy could be rapidly evaluated in the clinic after appropriate animal model studies have been completed. As this enzyme was initially studied in the context of NPD, we start with a brief overview of the history of ASM and NPD, followed by a discussion of the role of ASM in cancer biology, and then summarize emerging preclinical efficacy studies using rhASM as an adjunct in the treatment of solid tumors.
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Affiliation(s)
- Radoslav Savić
- Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, USA
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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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Young MM, Kester M, Wang HG. Sphingolipids: regulators of crosstalk between apoptosis and autophagy. J Lipid Res 2012; 54:5-19. [PMID: 23152582 DOI: 10.1194/jlr.r031278] [Citation(s) in RCA: 268] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Apoptosis and autophagy are two evolutionarily conserved processes that maintain homeostasis during stress. Although the two pathways utilize fundamentally distinct machinery, apoptosis and autophagy are highly interconnected and share many key regulators. The crosstalk between apoptosis and autophagy is complex, as autophagy can function to promote cell survival or cell death under various cellular conditions. The molecular mechanisms of crosstalk are beginning to be elucidated and have critical implications for the treatment of various diseases, such as cancer. Sphingolipids are a class of bioactive lipids that mediate many key cellular processes, including apoptosis and autophagy. By targeting several of the shared regulators, sphingolipid metabolites differentially regulate the induction of apoptosis and autophagy. Importantly, individual sphingolipid species appear to "switch" autophagy toward cell survival (e.g., sphingosine-1-phosphate) or cell death (e.g., ceramide, gangliosides). This review assesses the current understanding of sphingolipid-induced apoptosis and autophagy to address how sphingolipids mediate the "switch" between the cell survival and cell death. As sphingolipid metabolism is frequently dysregulated in cancer, sphingolipid-modulating agents, or sphingomimetics, have emerged as a novel chemotherapeutic strategy. Ultimately, a greater understanding of sphingolipid-mediated crosstalk between apoptosis and autophagy may be critical for enhancing the chemotherapeutic efficacy of these agents.
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Affiliation(s)
- Megan M Young
- Department of Pharmacology and Penn State Hershey Cancer Institute, Pennsylvania State University College of Medicine, Hershey, PA, USA
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Taniguchi M, Kitatani K, Kondo T, Hashimoto-Nishimura M, Asano S, Hayashi A, Mitsutake S, Igarashi Y, Umehara H, Takeya H, Kigawa J, Okazaki T. Regulation of autophagy and its associated cell death by "sphingolipid rheostat": reciprocal role of ceramide and sphingosine 1-phosphate in the mammalian target of rapamycin pathway. J Biol Chem 2012; 287:39898-910. [PMID: 23035115 DOI: 10.1074/jbc.m112.416552] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The role of "sphingolipid rheostat" by ceramide and sphingosine 1-phosphate (S1P) in the regulation of autophagy remains unclear. In human leukemia HL-60 cells, amino acid deprivation (AA(-)) caused autophagy with an increase in acid sphingomyleinase (SMase) activity and ceramide, which serves as an autophagy inducing lipid. Knockdown of acid SMase significantly suppressed the autophagy induction. S1P treatment counteracted autophagy induction by AA(-) or C(2)-ceramide. AA(-) treatment promoted mammalian target of rapamycin (mTOR) dephosphorylation/inactivation, inducing autophagy. S1P treatment suppressed mTOR inactivation and autophagy induction by AA(-). S1P exerts biological actions via cell surface receptors, and S1P(3) among five S1P receptors was predominantly expressed in HL-60 cells. We evaluated the involvement of S1P(3) in suppressing autophagy induction. S1P treatment of CHO cells had no effects on mTOR inactivation and autophagy induction by AA(-) or C(2)-ceramide. Whereas S1P treatment of S1P(3) overexpressing CHO cells resulted in activation of the mTOR pathway, preventing cells from undergoing autophagy induced by AA(-) or C(2)-ceramide. These results indicate that S1P-S1P(3) plays a role in counteracting ceramide signals that mediate mTOR-controlled autophagy. In addition, we evaluated the involvement of ceramide-activated protein phosphatases (CAPPs) in ceramide-dependent inactivation of the mTOR pathway. Inhibition of CAPP by okadaic acid in AA(-)- or C(2)-ceramide-treated cells suppressed dephosphorylation/inactivation of mTOR, autophagy induction, and autophagy-associated cell death, indicating a novel role of ceramide-CAPPs in autophagy induction. Moreover, S1P(3) engagement by S1P counteracted cell death. Taken together, these results indicated that sphingolipid rheostat in ceramide-CAPPs and S1P-S1P(3) signaling modulates autophagy and its associated cell death through regulation of the mTOR pathway.
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Affiliation(s)
- Makoto Taniguchi
- Division of Clinical Laboratory Medicine, Faculty of Medicine, Tottori University, 86 Nishi-Machi, Yonago 683-8503, Japan
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42
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Alternative splicing interference by xenobiotics. Toxicology 2012; 296:1-12. [DOI: 10.1016/j.tox.2012.01.014] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Revised: 01/21/2012] [Accepted: 01/23/2012] [Indexed: 12/21/2022]
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Perry DM, Kitatani K, Roddy P, El-Osta M, Hannun YA. Identification and characterization of protein phosphatase 2C activation by ceramide. J Lipid Res 2012; 53:1513-21. [PMID: 22615346 DOI: 10.1194/jlr.m025395] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Ceramide is a bioactive sphingolipid with many associated biological outcomes, yet there is a significant gap in our current understanding of how ceramide mediates these processes. Previously, ceramide has been shown to activate protein phosphatase (PP) 1 and 2A. While continuing this line of work, a late fraction from a Mono-Q column was consistently observed to be activated by ceramide, yet PP1 and PP2A were undetectable in this fraction. Proteomic analysis of this fraction revealed the identity of the phosphatase to be PP2Cγ/PPM1G. This was consistent with our findings that PP2Cγ 1-eluted in a high salt fraction due to its strongly acidic domain, and 2-was insensitive to okadaic acid. Further characterization was performed with PP2Cα, which showed robust activation by C(6)-ceramide. Activation was specific for the erythro conformation of ceramide and the presence of the acyl chain and hydroxyl group at the first carbon. In order to demonstrate more physiological activation of PP2Cα by ceramide, phospho-p38δ was utilized as substrate. Indeed, PP2Cα induced the dephosphorylation of p38δ only in the presence of C(16)-ceramide. Taken together, these results show that the PP2C family of phosphatases is activated by ceramide, which may have important consequences in mediating the biological effects of ceramide.
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Affiliation(s)
- David M Perry
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA
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44
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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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45
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Lafont E, Dupont R, Andrieu-Abadie N, Okazaki T, Schulze-Osthoff K, Levade T, Benoist H, Ségui B. Ordering of ceramide formation and caspase-9 activation in CD95L-induced Jurkat leukemia T cell apoptosis. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1821:684-93. [PMID: 22306364 DOI: 10.1016/j.bbalip.2012.01.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Revised: 01/03/2012] [Accepted: 01/18/2012] [Indexed: 11/19/2022]
Abstract
Ceramide, a biologically active sphingolipid in cell death signaling, accumulates upon CD95L treatment, concomitantly to apoptosis induction in Jurkat leukemia T cells. Herein, we show that ceramide did not increase in caspase-8 and -10-doubly deficient Jurkat cells in response to CD95L, indicating that apical caspases are essential for CD95L-triggered ceramide formation. Jurkat cells are typically defined as type 2 cells, which require the activation of the mitochondrial pathway for efficient apoptosis induction in response to CD95L. Caspase-9-deficient Jurkat cells significantly resisted CD95L-induced apoptosis, despite ceramide accumulation. Knock-down of sphingomyelin synthase 1, which metabolizes ceramide to sphingomyelin, enhanced (i) CD95L-triggered ceramide production, (ii) cytochrome c release from the mitochondria and (iii) caspase-9 activation. Exogenous ceramide-induced caspase-3 activation and apoptosis were impaired in caspase-9-deficient Jurkat cells. Conversely, caspase-9 re-expression in caspase-9-deficient Jurkat cells restored caspase-3 activation and apoptosis upon exogenous ceramide treatment. Collectively, our data provide genetic evidence that CD95L-triggered endogenous ceramide increase in Jurkat leukemia T cells (i) is not a mere consequence of cell death and occurs mainly in a caspase-9-independent manner, (ii) is likely involved in the pro-apoptotic mitochondrial pathway leading to caspase-9 activation.
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Affiliation(s)
- Elodie Lafont
- INSERM UMR1037, Centre de Recherches en Cancérologie de Toulouse, Equipe 4, BP84225, 31432 Toulouse Cedex 4, France
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46
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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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Dieker J, Iglesias-Guimarais V, Décossas M, Stevenin J, Vlag J, Yuste VJ, Muller S. Early Apoptotic Reorganization of Spliceosomal Proteins Involves Caspases, CAD and Rearrangement of NuMA. Traffic 2011; 13:257-72. [DOI: 10.1111/j.1600-0854.2011.01307.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Revised: 10/21/2011] [Accepted: 10/21/2011] [Indexed: 01/18/2023]
Affiliation(s)
| | - Victoria Iglesias-Guimarais
- Cell Death, Senescence & Survival Research Group; Dept. Bioquimica i Biologia Molecular; Institut de Neurociències; Universitat Autònoma de Barcelona; Barcelona; Spain
| | - Marion Décossas
- Centre National de la Recherche Scientifique (CNRS); Institut de Biologie Moléculaire et Cellulaire; Strasbourg; France
| | - James Stevenin
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC); Institut National de Santé et de Recherche Médicale (INSERM)/Centre National de Recherche Scientifique (CNRS); Université de Strasbourg; Illkirch; France
| | - Johan Vlag
- Nephrology Research Laboratory; Department of Nephrology; Nijmegen Centre for Molecular Life Sciences; Radboud University Nijmegen Medical Centre; Nijmegen; The Netherlands
| | - Victor J. Yuste
- Cell Death, Senescence & Survival Research Group; Dept. Bioquimica i Biologia Molecular; Institut de Neurociències; Universitat Autònoma de Barcelona; Barcelona; Spain
| | - Sylviane Muller
- Centre National de la Recherche Scientifique (CNRS); Institut de Biologie Moléculaire et Cellulaire; Strasbourg; France
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48
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Regulation of alternative splicing within the supraspliceosome. J Struct Biol 2011; 177:152-9. [PMID: 22100336 DOI: 10.1016/j.jsb.2011.11.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2011] [Revised: 11/02/2011] [Accepted: 11/05/2011] [Indexed: 12/12/2022]
Abstract
Alternative splicing is a fundamental feature in regulating the eukaryotic transcriptome, as ~95% of multi-exon human Pol II transcripts are subject to this process. Regulated splicing operates through the combinatorial interplay of positive and negative regulatory signals present in the pre-mRNA, which are recognized by trans-acting factors. All these RNA and protein components are assembled in a gigantic, 21 MDa, ribonucleoprotein splicing machine - the supraspliceosome. Because most alternatively spliced mRNA isoforms vary between different cell and tissue types, the ability to perform alternative splicing is expected to be an integral part of the supraspliceosome, which constitutes the splicing machine in vivo. Here we show that both the constitutively and alternatively spliced mRNAs of the endogenous human pol II transcripts: hnRNP A/B, survival of motor neuron (SMN) and ADAR2 are predominantly found in supraspliceosomes. This finding is consistent with our observations that the splicing regulators hnRNP G as well as all phosphorylated SR proteins are predominantly associated with supraspliceosomes. We further show that changes in alternative splicing of hnRNP A/B, affected by up regulation of SRSF5 (SRp40) or by treatment with C6-ceramide, occur within supraspliceosomes. These observations support the proposed role of the supraspliceosome in splicing regulation and alternative splicing.
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Leva V, Giuliano S, Bardoni A, Camerini S, Crescenzi M, Lisa A, Biamonti G, Montecucco A. Phosphorylation of SRSF1 is modulated by replicational stress. Nucleic Acids Res 2011; 40:1106-17. [PMID: 21984412 PMCID: PMC3273819 DOI: 10.1093/nar/gkr837] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
DNA ligase I-deficient 46BR.1G1 cells show a delay in the maturation of replicative intermediates resulting in the accumulation of single- and double-stranded DNA breaks. As a consequence the ataxia telangiectasia mutated protein kinase (ATM) is constitutively phosphorylated at a basal level. Here, we use 46BR.1G1 cells as a model system to study the cell response to chronic replication-dependent DNA damage. Starting from a proteomic approach, we demonstrate that the phosphorylation level of factors controlling constitutive and alternative splicing is affected by the damage elicited by DNA ligase I deficiency. In particular, we show that SRSF1 is hyperphosphorylated in 46BR.1G1 cells compared to control fibroblasts. This hyperphosphorylation can be partially prevented by inhibiting ATM activity with caffeine. Notably, hyperphosphorylation of SRSF1 affects the subnuclear distribution of the protein and the alternative splicing pattern of target genes. We also unveil a modulation of SRSF1 phosphorylation after exposure of MRC-5V1 control fibroblasts to different exogenous sources of DNA damage. Altogether, our observations indicate that a relevant aspect of the cell response to DNA damage involves the post-translational regulation of splicing factor SRSF1 which is associated with a shift in the alternative splicing program of target genes to control cell survival or cell death.
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Affiliation(s)
- Valentina Leva
- Istituto di Genetica Molecolare, Consiglio Nazionale delle Ricerche, 27100 Pavia, Italy
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50
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Dobierzewska A, Giltiay NV, Sabapathi S, Karakashian AA, Nikolova-Karakashian MN. Protein phosphatase 2A and neutral sphingomyelinase 2 regulate IRAK-1 protein ubiquitination and degradation in response to interleukin-1beta. J Biol Chem 2011; 286:32064-73. [PMID: 21708940 DOI: 10.1074/jbc.m111.238030] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The IL-1β signaling cascade is initiated by the phosphorylation of IL-1β receptor-associated kinase-1 (IRAK-1), followed by its ubiquitination and degradation. This paper investigates the regulation of IRAK-1 degradation in primary hepatocytes and in HEK cells overexpressing the IL-1β receptor. We provide evidence that protein phosphatase 2A (PP2A) is a negative regulator of the phosphorylation, Lys(48)-linked ubiquitination, and degradation of IRAK-1. PP2A catalytic activity increased within 30 min of stimulation with IL-1β. siRNA against PP2A catalytic subunit (PP2Ac) or treatment with pharmacological inhibitor, okadaic acid, enhanced IRAK-1 Lys(48)-linked ubiquitination and degradation. Direct interaction between PP2Ac and IRAK-1 was observed, suggesting that IRAK-1 might be a PP2A substrate. The mechanisms of PP2A activation by IL-1β involved neutral sphingomyelinase-2 (NSMase-2) and an accumulation of ceramide. Overexpression of NSMase-2 delayed IRAK-1 degradation in a PP2A-dependent manner, whereas NSMase-2 silencing had the opposite effect. The addition of sphingomyelinase, ceramide, or a proteasome inhibitor all led to retention of IRAK-1 at the cell membrane and to increased JNK phosphorylation. This study suggests that NSMase-2- and PP2A-dependent regulation of IRAK-1 degradation is a novel mechanism to fine tune the magnitude of IL-1β response.
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Affiliation(s)
- Aneta Dobierzewska
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky 40536, USA
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