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Sánchez-Alegría K, Arias C. Functional consequences of brain exposure to saturated fatty acids: From energy metabolism and insulin resistance to neuronal damage. Endocrinol Diabetes Metab 2023; 6:e386. [PMID: 36321333 PMCID: PMC9836261 DOI: 10.1002/edm2.386] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 10/06/2022] [Accepted: 10/09/2022] [Indexed: 11/06/2022] Open
Abstract
INTRODUCTION Saturated fatty acids (FAs) are the main component of high-fat diets (HFDs), and high consumption has been associated with the development of insulin resistance, endoplasmic reticulum stress and mitochondrial dysfunction in neuronal cells. In particular, the reduction in neuronal insulin signaling seems to underlie the development of cognitive impairments and has been considered a risk factor for Alzheimer's disease (AD). METHODS This review summarized and critically analyzed the research that has impacted the field of saturated FA metabolism in neurons. RESULTS We reviewed the mechanisms for free FA transport from the systemic circulation to the brain and how they impact neuronal metabolism. Finally, we focused on the molecular and the physiopathological consequences of brain exposure to the most abundant FA in the HFD, palmitic acid (PA). CONCLUSION Understanding the mechanisms that lead to metabolic alterations in neurons induced by saturated FAs could help to develop several strategies for the prevention and treatment of cognitive impairment associated with insulin resistance, metabolic syndrome, or type II diabetes.
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Affiliation(s)
- Karina Sánchez-Alegría
- Departamento de Medicina Genómica y Toxicología Ambiental, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
| | - Clorinda Arias
- Departamento de Medicina Genómica y Toxicología Ambiental, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
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2
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Targeting Acid Ceramidase Inhibits Glioblastoma Cell Migration through Decreased AKT Signaling. Cells 2022; 11:cells11121873. [PMID: 35741006 PMCID: PMC9221433 DOI: 10.3390/cells11121873] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2022] [Revised: 05/13/2022] [Accepted: 06/06/2022] [Indexed: 01/12/2023] Open
Abstract
Glioblastoma (GBM) remains one of the most aggressive cancers, partially due to its ability to migrate into the surrounding brain. The sphingolipid balance, or the balance between ceramides and sphingosine-1-phosphate, contributes to the ability of GBM cells to migrate or invade. Of the ceramidases which hydrolyze ceramides, acid ceramidase (ASAH1) is highly expressed in GBM samples compared to non-tumor brain. ASAH1 expression also correlates with genes associated with migration and focal adhesion. To understand the role of ASAH1 in GBM migration, we utilized shRNA knockdown and observed decreased migration that did not depend upon changes in growth. Next, we inhibited ASAH1 using carmofur, a clinically utilized small molecule inhibitor. Inhibition of ASAH1 by carmofur blocks in vitro migration of U251 (GBM cell line) and GBM cells derived from patient-derived xenografts (PDXs). RNA-sequencing suggested roles for carmofur in MAPK and AKT signaling. We found that carmofur treatment decreases phosphorylation of AKT, but not of MAPK. The decrease in AKT phosphorylation was confirmed by shRNA knockdown of ASAH1. Our findings substantiate ASAH1 inhibition using carmofur as a potential clinically relevant treatment to advance GBM therapeutics, particularly due to its impact on migration.
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Louis JM, Agarwal A, Mondal S, Talukdar I. A global analysis on the differential regulation of RNA binding proteins (RBPs) by TNF–α as potential modulators of metabolic syndromes. BBA ADVANCES 2022; 2:100037. [PMID: 37082594 PMCID: PMC10074950 DOI: 10.1016/j.bbadva.2021.100037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2021] [Revised: 12/12/2021] [Accepted: 12/15/2021] [Indexed: 11/25/2022] Open
Abstract
Metabolic syndrome (MetS) is associated with a group of conditions, which enhances the risk of diabetes, heart diseases and stroke in the affected individuals. Earlier reports from our lab have shown that Tumor necrosis factor-α (TNF-α) significantly modulates the expression of 56 genes at the alternative splicing level which are involved in various signaling and metabolic pathways (MetS genes) connected to MetS. These MetS genes were predicted to interact with various RNA-binding proteins (RBPs) when exposed to TNF-α, resulting changes in their alternative splicing patterns. Here we are presenting data of an RNA-Seq analysis, which identified 1218 unique, and significantly regulated genes by TNF-α, 15% of which are RBPs . Among the 1218 genes, 204 genes have been identified as MetS genes by the ingenuity pathway analysis, and 10% of the MetS genes are found as RBPs. Our results also show that TNF-α changes the phosphorylation status of certain RBPs such as SR proteins, crucial players in alternative splicing, possibly via changing the activation status of certain upstream signaling molecules which also act as upstream kinases for these proteins. Taken together, these findings suggest that TNF-α influences the regulation of the RBPs at the various levels for their expression, which may lead to the alteration of the splicing pattern of the MetS genes. MetS genes acting as RBPs and are modulated by TNF-α, predict the existence of highly interconnected mechanisms which require further analysis to understand their dual roles on the onset of these diseases.
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Sindhu S, Leung YH, Arefanian H, Madiraju SRM, Al‐Mulla F, Ahmad R, Prentki M. Neutral sphingomyelinase-2 and cardiometabolic diseases. Obes Rev 2021; 22:e13248. [PMID: 33738905 PMCID: PMC8365731 DOI: 10.1111/obr.13248] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 02/18/2021] [Accepted: 02/26/2021] [Indexed: 12/13/2022]
Abstract
Sphingolipids, in particular ceramides, play vital role in pathophysiological processes linked to metabolic syndrome, with implications in the development of insulin resistance, pancreatic ß-cell dysfunction, type 2 diabetes, atherosclerosis, inflammation, nonalcoholic steatohepatitis, and cancer. Ceramides are produced by the hydrolysis of sphingomyelin, catalyzed by different sphingomyelinases, including neutral sphingomyelinase 2 (nSMase2), whose dysregulation appears to underlie many of the inflammation-related pathologies. In this review, we discuss the current knowledge on the biochemistry of nSMase2 and ceramide production and its regulation by inflammatory cytokines, with particular reference to cardiometabolic diseases. nSMase2 contribution to pathogenic processes appears to involve cyclical feed-forward interaction with proinflammatory cytokines, such as TNF-α and IL-1ß, which activate nSMase2 and the production of ceramides, that in turn triggers the synthesis and release of inflammatory cytokines. We elaborate these pathogenic interactions at the molecular level and discuss the potential therapeutic benefits of inhibiting nSMase2 against inflammation-driven cardiometabolic diseases.
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Affiliation(s)
- Sardar Sindhu
- Animal and Imaging core facilityDasman Diabetes InstituteDasmanKuwait
| | - Yat Hei Leung
- Departments of Nutrition, Biochemistry and Molecular MedicineUniversity of MontrealMontréalQuebecCanada
- Centre de Recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM)Montreal Diabetes Research CenterMontréalQuebecCanada
| | - Hossein Arefanian
- Immunology and Microbiology DepartmentDasman Diabetes InstituteDasmanKuwait
| | - S. R. Murthy Madiraju
- Departments of Nutrition, Biochemistry and Molecular MedicineUniversity of MontrealMontréalQuebecCanada
- Centre de Recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM)Montreal Diabetes Research CenterMontréalQuebecCanada
| | - Fahd Al‐Mulla
- Department of Genetics and BioinformaticsDasman Diabetes InstituteDasmanKuwait
| | - Rasheed Ahmad
- Immunology and Microbiology DepartmentDasman Diabetes InstituteDasmanKuwait
| | - Marc Prentki
- Departments of Nutrition, Biochemistry and Molecular MedicineUniversity of MontrealMontréalQuebecCanada
- Centre de Recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM)Montreal Diabetes Research CenterMontréalQuebecCanada
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5
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Wu P, Zhang M, Webster NJG. Alternative RNA Splicing in Fatty Liver Disease. Front Endocrinol (Lausanne) 2021; 12:613213. [PMID: 33716968 PMCID: PMC7953061 DOI: 10.3389/fendo.2021.613213] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 01/13/2021] [Indexed: 12/12/2022] Open
Abstract
Alternative RNA splicing is a process by which introns are removed and exons are assembled to construct different RNA transcript isoforms from a single pre-mRNA. Previous studies have demonstrated an association between dysregulation of RNA splicing and a number of clinical syndromes, but the generality to common disease has not been established. Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease affecting one-third of adults worldwide, increasing the risk of cirrhosis and hepatocellular carcinoma (HCC). In this review we focus on the change in alternative RNA splicing in fatty liver disease and the role for splicing regulation in disease progression.
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Affiliation(s)
- Panyisha Wu
- Department of Medicine, Division of Endocrinology and Metabolism, University of California San Diego, La Jolla, CA, United States
| | - Moya Zhang
- University of California Los Angeles, Los Angeles, CA, United States
| | - Nicholas J. G. Webster
- VA San Diego Healthcare System, San Diego, CA, United States
- Department of Medicine, Division of Endocrinology and Metabolism, University of California San Diego, La Jolla, CA, United States
- Moores Cancer Center, University of California, San Diego, La Jolla, CA, United States
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6
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Razak Hady H, Błachnio-Zabielska AU, Szczerbiński Ł, Zabielski P, Imierska M, Dadan J, Krętowski AJ. Ceramide Content in Liver Increases Along with Insulin Resistance in Obese Patients. J Clin Med 2019; 8:E2197. [PMID: 31842461 PMCID: PMC6947381 DOI: 10.3390/jcm8122197] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 12/02/2019] [Accepted: 12/11/2019] [Indexed: 12/15/2022] Open
Abstract
The liver plays a central role in the glucose and lipid metabolism. Studies performed on animal models have shown an important role of lipid accumulation in the induction of insulin resistance. We sought to explain whether in obese humans, the insulin resistance is associated with hepatic ceramide accumulation. The experiments were conducted on obese men and women. Each gender was divided into three groups: Normal glucose tolerance group (NGT), Impaired glucose tolerance group (IGT), and Type 2 diabetic subjects (T2D). Ceramide (Cer) content was analyzed with the use of LC/MS/MS. An oral glucose tolerance test (OGTT), glycosylated hemoglobin (HbA1c), percentage body fat (FAT%), and body mass index (BMI) was also measured. Total hepatic ceramide was significantly higher in T2D females as compared to NGT females (p < 0.05), whereas in males, total ceramide was significantly higher in IGT and T2D as compared to NGT (p < 0.05). In both, men and women, the highest increase in T2D subjects, was observed in C16:0-Cer, C18:0:-Cer, C22:0-Cer, and C24:0-Cer (p < 0.05) as compared to NGT group. Interestingly, glucose (at 0' and at 120' in OGTT) and HbA1c positively correlated with the ceramide species that most increased in T2D patients (C16:0-Cer, C18:0-Cer, C22:0-Cer, and C24:0-Cer). In men glucose and HbA1c significantly correlated with only C22:0-Cer. This is one of the few studies comparing hepatic ceramide content in severely obese patients. We found that, ceramide content increased in diabetic patients, both in men and women, and the content of ceramide correlated with glycemic parameters. These data indicate ceramide contribution to the induction of hepatic insulin resistance.
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Affiliation(s)
- Hady Razak Hady
- 1st Department of General Surgery and Endocrinology, Medical University Bialystok, 15-276 Bialystok, Poland; (H.R.H.); (J.D.)
| | | | - Łukasz Szczerbiński
- Department of Endocrinology, Diabetology and Internal Medicine, Medical University of Bialystok, 15-276 Bialystok, Poland; (Ł.S.); (A.J.K.)
| | - Piotr Zabielski
- Department of Medical Biology, Medical University of Bialystok, 15-222 Bialystok, Poland;
| | - Monika Imierska
- Department of Hygiene, Epidemiology and Metabolic Disorders, Medical University of Bialystok, 15-222 Bialystok, Poland;
| | - Jacek Dadan
- 1st Department of General Surgery and Endocrinology, Medical University Bialystok, 15-276 Bialystok, Poland; (H.R.H.); (J.D.)
| | - Adam J. Krętowski
- Department of Endocrinology, Diabetology and Internal Medicine, Medical University of Bialystok, 15-276 Bialystok, Poland; (Ł.S.); (A.J.K.)
- Clinical Research Centre, Medical University of Bialystok, 15-276 Bialystok, Poland
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Stith JL, Velazquez FN, Obeid LM. Advances in determining signaling mechanisms of ceramide and role in disease. J Lipid Res 2019; 60:913-918. [PMID: 30846529 PMCID: PMC6495170 DOI: 10.1194/jlr.s092874] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 02/22/2019] [Indexed: 02/07/2023] Open
Abstract
Ceramide is a critical bioactive lipid involved in diverse cellular processes. It has been proposed to regulate cellular processes by influencing membrane properties and by directly interacting with effector proteins. Advances over the past decade have improved our understanding of ceramide as a bioactive lipid. Generation and characterization of ceramide-metabolizing enzyme KO mice, development of specific inhibitors and ceramide-specific antibodies, use of advanced microscopy and mass spectrometry, and design of synthetic ceramide derivatives have all provided insight into the signaling mechanisms of ceramide and its implications in disease. As a result, the role of ceramide in biological functions and disease are now better understood, with promise for development of therapeutic strategies to treat ceramide-regulated diseases.
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Affiliation(s)
- Jeffrey L Stith
- Stony Brook Cancer Center and the Department of Medicine, Health Sciences Center, Stony Brook University, Stony Brook, NY 11794
| | - Fabiola N Velazquez
- Stony Brook Cancer Center and the Department of Medicine, Health Sciences Center, Stony Brook University, Stony Brook, NY 11794
| | - Lina M Obeid
- Stony Brook Cancer Center and the Department of Medicine, Health Sciences Center, Stony Brook University, Stony Brook, NY 11794; Northport Veterans Affairs Medical Center Northport, NY 11768.
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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: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 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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Zabielski P, Daniluk J, Hady HR, Markowski AR, Imierska M, Górski J, Blachnio-Zabielska AU. The effect of high-fat diet and inhibition of ceramide production on insulin action in liver. J Cell Physiol 2018; 234:1851-1861. [PMID: 30067865 DOI: 10.1002/jcp.27058] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 06/25/2018] [Indexed: 12/18/2022]
Abstract
Liver, as one of the most important organs involved in lipids and glucose metabolism, is perceived as a key tissue for pharmacotherapy of insulin resistance (IRes) and type 2 diabetes. Ceramides (Cer) are biologically active lipids, which accumulation is associated with the induction of muscle IRes. We sought to determine the role of intrahepatic bioactive lipids production on insulin action in liver of insulin-resistant rats and after myriocin administration. The experiments were conducted on male Wistar rats divided into three groups: Control, fed high-fat diet (HFD), and fed HFD and treated with myriocin (HFD/Myr). Before sacrifice, the animals were infused with a [U-13 C]palmitate to calculate lipid synthesis rate by means of tracer incorporation technique in particular lipid groups. Liver Cer, diacylglycerols (DAG), acyl-carnitine concentration, and isotopic enrichment were analyzed by LC/MS/MS. Proteins involved in lipid metabolism and insulin pathway were analyzed by western blot analysis. An OGTT and ITT was also performed. HFD-induced IRes and increased both the synthesis rate and the content of DAG and Cer, which was accompanied by inhibition of an insulin pathway. Interestingly, myriocin treatment reduced synthesis rate not only of Cer but also DAG and improved insulin sensitivity. We conclude that the insulin-sensitizing action of myriocin in the liver is a result of the lack of inhibitory effect of lipids on the insulin pathway, due to the reduction of their synthesis rate. This is the first study showing how the synthesis rate of individual lipid groups in liver changes after myriocin administration.
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Affiliation(s)
- Piotr Zabielski
- Department of Medical Biology, Medical University of Bialystok, Bialystok, Poland.,Department of Physiology, Medical University of Bialystok, Bialystok, Poland
| | - Jarosław Daniluk
- Department of Gastroenterology and Internal Medicine, Medical University of Bialystok, Bialystok, Poland
| | - Hady Razak Hady
- 1st Department of General Surgery and Endocrinology, Medical University Bialystok, Bialystok, Poland
| | - Adam R Markowski
- Department of Internal Medicine and Gastroenterology, Polish Red Cross Memorial Municipal Hospital, Bialystok, Poland
| | - Monika Imierska
- Department of Hygiene, Epidemiology and Metabolic Disorders, Medical University of Bialystok, Bialystok, Poland
| | - Jan Górski
- Department of Physiology, Medical University of Bialystok, Bialystok, Poland.,Department of Basic Sciences, Faculty of Health Sciences, Lomza State University of Applied Sciences, Lomza, Poland
| | - Agnieszka U Blachnio-Zabielska
- Department of Physiology, Medical University of Bialystok, Bialystok, Poland.,Department of Hygiene, Epidemiology and Metabolic Disorders, Medical University of Bialystok, Bialystok, Poland
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10
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Bozic J, Markotic A, Cikes-Culic V, Novak A, Borovac JA, Vucemilovic H, Trgo G, Ticinovic Kurir T. Ganglioside GM3 content in skeletal muscles is increased in type 2 but decreased in type 1 diabetes rat models: Implications of glycosphingolipid metabolism in pathophysiology of diabetes. J Diabetes 2018; 10:130-139. [PMID: 28544772 DOI: 10.1111/1753-0407.12569] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Revised: 03/10/2017] [Accepted: 04/13/2017] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Ganglioside GM3 is found in the plasma membrane, where its accumulation attenuates insulin receptor signaling. Considering the role of skeletal muscles in insulin-stimulated glucose uptake, the aim of the present study was to determine the expression of GM3 and its precursors in skeletal muscles of rat models of type 1 and type 2 diabetes mellitus (T1DM and T2DM, respectively). METHODS Diabetes was induced in male Sprague-Dawley rats by streptozotocin injection (55 mg/kg, i.p., for T1DM induction; 35 mg/kg, i.p., for T2DM induction), followed by feeding of rats with either a normal pellet diet (T1DM) or a high-fat diet (T2DM). Rats were killed 2 weeks after diabetes induction and samples of skeletal muscle were collected. Frozen quadriceps muscle sections were stained with a primary antibody against GM3 (Neu5Ac) and visualized using a secondary antibody coupled with Texas Red. The muscle content of ganglioside GM3 and its precursors was analyzed by high-performance thin-layer chromatography (HPTLC) followed by GM3 immunostaining. RESULTS Muscle GM3 content was significantly higher in T2DM compared with control rats (P < 0.001). Furthermore, levels of the GM3 precursors ceramide, glucosylceramide, and lactosylceramide were significantly higher in T2DM compared with control rats (P < 0.05), whereas ceramide content was significantly lower in T1DM rats (P < 0.05). The intensity of the GM3 band on HPTLC was significantly higher in T2DM rats (P < 0.001) and significantly lower in T1DM rats (P < 0.05) compared with control. CONCLUSIONS The expression patterns of GM3 ganglioside and its precursors in diabetic rats suggest that the role of glycosphingolipid metabolism may differ between T2DM and T1DM.
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Affiliation(s)
- Josko Bozic
- Department of Pathophysiology, University of Split School of Medicine, Split, Croatia
| | - Anita Markotic
- Department of Medical Chemistry and Biochemistry, University of Split School of Medicine, Split, Croatia
| | - Vedrana Cikes-Culic
- Department of Medical Chemistry and Biochemistry, University of Split School of Medicine, Split, Croatia
| | - Anela Novak
- Department of Internal Medicine, University Hospital Split, Split, Croatia
| | - Josip A Borovac
- Department of Pathophysiology, University of Split School of Medicine, Split, Croatia
| | - Hrvoje Vucemilovic
- Department of Anesthesiology and Intensive Care Medicine, University Hospital Split, Split, Croatia
| | - Gorana Trgo
- Department of Internal Medicine, University Hospital Split, Split, Croatia
| | - Tina Ticinovic Kurir
- Department of Pathophysiology, University of Split School of Medicine, Split, Croatia
- Department of Internal Medicine, University Hospital Split, Split, Croatia
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Vilaça R, Barros I, Matmati N, Silva E, Martins T, Teixeira V, Hannun YA, Costa V. The ceramide activated protein phosphatase Sit4 impairs sphingolipid dynamics, mitochondrial function and lifespan in a yeast model of Niemann-Pick type C1. Biochim Biophys Acta Mol Basis Dis 2017; 1864:79-88. [PMID: 28988886 DOI: 10.1016/j.bbadis.2017.10.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Revised: 09/29/2017] [Accepted: 10/05/2017] [Indexed: 12/20/2022]
Abstract
The Niemann-Pick type C is a rare neurodegenerative disease that results from loss-of-function point mutations in NPC1 or NPC2, which affect the homeostasis of sphingolipids and sterols in human cells. We have previously shown that yeast lacking Ncr1, the orthologue of human NPC1 protein, display a premature ageing phenotype and higher sensitivity to oxidative stress associated with mitochondrial dysfunctions and accumulation of long chain bases. In this study, a lipidomic analysis revealed specific changes in the levels of ceramide species in ncr1Δ cells, including decreases in dihydroceramides and increases in phytoceramides. Moreover, the activation of Sit4, a ceramide-activated protein phosphatase, increased in ncr1Δ cells. Deletion of SIT4 or CDC55, its regulatory subunit, increased the chronological lifespan and hydrogen peroxide resistance of ncr1Δ cells and suppressed its mitochondrial defects. Notably, Sch9 and Pkh1-mediated phosphorylation of Sch9 decreased significantly in ncr1Δsit4Δ cells. These results suggest that phytoceramide accumulation and Sit4-dependent signaling mediate the mitochondrial dysfunction and shortened lifespan in the yeast model of Niemann-Pick type C1, in part through modulation of the Pkh1-Sch9 pathway.
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Affiliation(s)
- Rita Vilaça
- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Portugal; Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal; Departamento de Biologia Molecular, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
| | - Ivo Barros
- Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal; Departamento de Biologia Molecular, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
| | - Nabil Matmati
- Stony Brook Cancer Center, Stony Brook University, Health Science Center, Stony Brook, NY, USA
| | - Elísio Silva
- Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal; Departamento de Biologia Molecular, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
| | - Telma Martins
- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Portugal; Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - Vítor Teixeira
- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Portugal; Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal; Departamento de Biologia Molecular, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
| | - Yusuf A Hannun
- Stony Brook Cancer Center, Stony Brook University, Health Science Center, Stony Brook, NY, USA
| | - Vítor Costa
- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Portugal; Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal; Departamento de Biologia Molecular, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal.
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12
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Black AJ, Ravi S, Jefferson LS, Kimball SR, Schilder RJ. Dietary Fat Quantity and Type Induce Transcriptome-Wide Effects on Alternative Splicing of Pre-mRNA in Rat Skeletal Muscle. J Nutr 2017; 147:1648-1657. [PMID: 28768832 PMCID: PMC5572497 DOI: 10.3945/jn.117.254482] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 06/07/2017] [Accepted: 06/28/2017] [Indexed: 12/18/2022] Open
Abstract
Background: Fat-enriched diets produce metabolic changes in skeletal muscle, which in turn can mediate changes in gene regulation.Objective: We examined the high-fat-diet-induced changes in skeletal muscle gene expression by characterizing variations in pre-mRNA alternative splicing.Methods: Affymetrix Exon Array analysis was performed on the transcriptome of the gastrocnemius/plantaris complex of male obesity-prone Sprague-Dawley rats fed a 10% or 60% fat (lard) diet for 2 or 8 wk. The validation of exon array results was focused on troponin T (Tnnt3). Tnnt3 splice form analyses were extended in studies of rats fed 10% or 30% fat diets across 1- to 8-wk treatment periods and rats fed 10% or 45% fat diets with fat sources from lard or mono- or polyunsaturated fats for 2 wk. Nuclear magnetic resonance (NMR) was used to measure body composition.Results: Consumption of a 60% fat diet for 2 or 8 wk resulted in alternative splicing of 668 and 726 pre-mRNAs, respectively, compared with rats fed a 10% fat diet. Tnnt3 transcripts were alternatively spliced in rats fed a 60% fat diet for either 2 or 8 wk. The high-fat-diet-induced changes in Tnnt3 alternative splicing were observed in rats fed a 30% fat diet across 1- to 8-wk treatment periods. Moreover, this effect depended on fat type, because Tnnt3 alternative splicing occurred in response to 45% fat diets enriched with lard but not in response to diets enriched with mono- or polyunsaturated fatty acids. Fat mass (a proxy for obesity as measured by NMR) did not differ between groups in any study.Conclusions: Rat skeletal muscle responds to overconsumption of dietary fat by modifying gene expression through pre-mRNA alternative splicing. Variations in Tnnt3 alternative splicing occur independently of obesity and are dependent on dietary fat quantity and suggest a role for saturated fatty acids in the high-fat-diet-induced modifications in Tnnt3 alternative splicing.
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Affiliation(s)
- Adam J Black
- Intercollege Graduate Degree Program in Physiology and,Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, PA; and
| | - Suhana Ravi
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, PA; and
| | - Leonard S Jefferson
- Intercollege Graduate Degree Program in Physiology and,Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, PA; and
| | - Scot R Kimball
- Intercollege Graduate Degree Program in Physiology and,Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, PA; and
| | - Rudolf J Schilder
- Departments of Entomology and Biology, Penn State University, University Park, State College, PA
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13
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Huang FC. The Role of Sphingolipids on Innate Immunity to Intestinal Salmonella Infection. Int J Mol Sci 2017; 18:ijms18081720. [PMID: 28783107 PMCID: PMC5578110 DOI: 10.3390/ijms18081720] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 07/25/2017] [Accepted: 07/27/2017] [Indexed: 02/06/2023] Open
Abstract
Salmonella spp. remains a major public health problem for the whole world. To reduce the use of antimicrobial agents and drug-resistant Salmonella, a better strategy is to explore alternative therapy rather than to discover another antibiotic. Sphingolipid- and cholesterol-enriched lipid microdomains attract signaling proteins and orchestrate them toward cell signaling and membrane trafficking pathways. Recent studies have highlighted the crucial role of sphingolipids in the innate immunity against infecting pathogens. It is therefore mandatory to exploit the role of the membrane sphingolipids in the innate immunity of intestinal epithelia infected by this pathogen. In the present review, we focus on the role of sphingolipids in the innate immunity of intestinal epithelia against Salmonella infection, including adhesion, autophagy, bactericidal effect, barrier function, membrane trafficking, cytokine and antimicrobial peptide expression. The intervention of sphingolipid-enhanced foods to make our life healthy or pharmacological agents regulating sphingolipids is provided at the end.
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Affiliation(s)
- Fu-Chen Huang
- Department of Pediatrics, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung 833, Taiwan.
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14
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Brandão BB, Guerra BA, Mori MA. Shortcuts to a functional adipose tissue: The role of small non-coding RNAs. Redox Biol 2017; 12:82-102. [PMID: 28214707 PMCID: PMC5312655 DOI: 10.1016/j.redox.2017.01.020] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Accepted: 01/30/2017] [Indexed: 12/20/2022] Open
Abstract
Metabolic diseases such as type 2 diabetes are a major public health issue worldwide. These diseases are often linked to a dysfunctional adipose tissue. Fat is a large, heterogenic, pleiotropic and rather complex tissue. It is found in virtually all cavities of the human body, shows unique plasticity among tissues, and harbors many cell types in addition to its main functional unit - the adipocyte. Adipose tissue function varies depending on the localization of the fat depot, the cell composition of the tissue and the energy status of the organism. While the white adipose tissue (WAT) serves as the main site for triglyceride storage and acts as an important endocrine organ, the brown adipose tissue (BAT) is responsible for thermogenesis. Beige adipocytes can also appear in WAT depots to sustain heat production upon certain conditions, and it is becoming clear that adipose tissue depots can switch phenotypes depending on cell autonomous and non-autonomous stimuli. To maintain such degree of plasticity and respond adequately to changes in the energy balance, three basic processes need to be properly functioning in the adipose tissue: i) adipogenesis and adipocyte turnover, ii) metabolism, and iii) signaling. Here we review the fundamental role of small non-coding RNAs (sncRNAs) in these processes, with focus on microRNAs, and demonstrate their importance in adipose tissue function and whole body metabolic control in mammals.
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Affiliation(s)
- Bruna B Brandão
- Program in Molecular Biology, Universidade Federal de São Paulo, São Paulo, Brazil; Department of Biochemistry and Tissue Biology, Universidade Estadual de Campinas, Campinas, Brazil
| | - Beatriz A Guerra
- Program in Molecular Biology, Universidade Federal de São Paulo, São Paulo, Brazil; Department of Biochemistry and Tissue Biology, Universidade Estadual de Campinas, Campinas, Brazil
| | - Marcelo A Mori
- Program in Molecular Biology, Universidade Federal de São Paulo, São Paulo, Brazil; Department of Biochemistry and Tissue Biology, Universidade Estadual de Campinas, Campinas, Brazil; Program in Genetics and Molecular Biology, Universidade Estadual de Campinas, Campinas, Brazil.
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15
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Morales PE, Bucarey JL, Espinosa A. Muscle Lipid Metabolism: Role of Lipid Droplets and Perilipins. J Diabetes Res 2017; 2017:1789395. [PMID: 28676863 PMCID: PMC5476901 DOI: 10.1155/2017/1789395] [Citation(s) in RCA: 102] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Revised: 04/19/2017] [Accepted: 04/26/2017] [Indexed: 02/07/2023] Open
Abstract
Skeletal muscle is one of the main regulators of carbohydrate and lipid metabolism in our organism, and therefore, it is highly susceptible to changes in glucose and fatty acid (FA) availability. Skeletal muscle is an extremely complex tissue: its metabolic capacity depends on the type of fibers it is made up of and the level of stimulation it undergoes, such as acute or chronic contraction. Obesity is often associated with increased FA levels, which leads to the accumulation of toxic lipid intermediates, oxidative stress, and autophagy in skeletal fibers. This lipotoxicity is one of the most common causes of insulin resistance (IR). In this scenario, the "isolation" of certain lipids in specific cell compartments, through the action of the specific lipid droplet, perilipin (PLIN) family of proteins, is conceived as a lifeguard compensatory strategy. In this review, we summarize the cellular mechanism underlying lipid mobilization and metabolism inside skeletal muscle, focusing on the function of lipid droplets, the PLIN family of proteins, and how these entities are modified in exercise, obesity, and IR conditions.
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Affiliation(s)
- Pablo Esteban Morales
- Departamento de Tecnología Médica, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Jose Luis Bucarey
- CIDIS-AC, Escuela de Medicina, Universidad de Valparaiso, Valparaiso, Chile
| | - Alejandra Espinosa
- Departamento de Tecnología Médica, Facultad de Medicina, Universidad de Chile, Santiago, Chile
- Center for Molecular Studies of the Cell, Facultad de Medicina, Universidad de Chile, Santiago, Chile
- *Alejandra Espinosa:
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16
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Sánchez-Iglesias S, Unruh-Pinheiro A, Guillín-Amarelle C, González-Méndez B, Ruiz-Riquelme A, Rodríguez-Cañete BL, Rodríguez-García S, Guillén-Navarro E, Domingo-Jiménez R, Araújo-Vilar D. Skipped BSCL2 Transcript in Celia's Encephalopathy (PELD): New Insights on Fatty Acids Involvement, Senescence and Adipogenesis. PLoS One 2016; 11:e0158874. [PMID: 27391332 PMCID: PMC4938205 DOI: 10.1371/journal.pone.0158874] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Accepted: 06/23/2016] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVE PELD (Progressive Encephalopathy with or without Lipodystrophy or Celia's Encephalopathy) is a fatal and rare neurodegenerative syndrome associated with the BSCL2 mutation c.985C>T, that results in an aberrant transcript without the exon 7 (Celia seipin). The aim of this study was to evaluate both the process of cellular senescence and the effect of unsaturated fatty acids on preadipocytes from a homozygous c.985C>T patient. Also, the role of aberrant seipin isoform on adipogenesis was studied in adipose-derived human mesenchymal stem cells. MATERIAL AND METHODS Cellular senescence was evaluated using β-galactosidase staining of preadipocytes obtained from a homozygous c.985C>T patient. Moreover, these cells were cultured during 24 hours with Intralipid, a soybean oil-based commercial lipid emulsion. The expression of the different BSCL2 transcripts was measured by qPCR. Adipose-derived human mesenchymal stem cells were differentiated to a fat lineage using StemPRO adipogenesis kit, and the expression of BSCL2 transcripts and several adipogenesis-related genes was measured by qPCR. RESULTS the treatment of preadipocytes with unsaturated fatty acids significantly reduced the expression of the BSCL2 transcript without exon 7 by 34 to 63%. On the other hand, at least in preadipocytes, this mutation does not disturb cellular senescence rate. Finally, during adipocyte differentiation of adipose-derived human mesenchymal stem cells, the expression of adipogenic genes (PPARG, LPIN1, and LPL) increased significantly over 14 days, and noteworthy is that the BSCL2 transcript without exon 7 was differentially expressed by 332 to 723% when compared to day 0, suggesting an underlying role in adipogenesis. CONCLUSIONS our results suggest that Celia seipin is probably playing an underestimated role in adipocyte maturation, but not in senescence, and its expression can be modified by exogenous factors as fatty acids.
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Affiliation(s)
- Sofía Sánchez-Iglesias
- Thyroid and Metabolic Diseases Unit (U.E.T.eM.), Department of Medicine, Center for Research in Molecular Medicine and Chronic Diseases (CIMUS)-IDIS, University of Santiago de Compostela, Santiago de Compostela, Spain
| | - Alexander Unruh-Pinheiro
- Thyroid and Metabolic Diseases Unit (U.E.T.eM.), Department of Medicine, Center for Research in Molecular Medicine and Chronic Diseases (CIMUS)-IDIS, University of Santiago de Compostela, Santiago de Compostela, Spain
| | - Cristina Guillín-Amarelle
- Thyroid and Metabolic Diseases Unit (U.E.T.eM.), Department of Medicine, Center for Research in Molecular Medicine and Chronic Diseases (CIMUS)-IDIS, University of Santiago de Compostela, Santiago de Compostela, Spain
| | - Blanca González-Méndez
- Thyroid and Metabolic Diseases Unit (U.E.T.eM.), Department of Medicine, Center for Research in Molecular Medicine and Chronic Diseases (CIMUS)-IDIS, University of Santiago de Compostela, Santiago de Compostela, Spain
| | - Alejandro Ruiz-Riquelme
- Thyroid and Metabolic Diseases Unit (U.E.T.eM.), Department of Medicine, Center for Research in Molecular Medicine and Chronic Diseases (CIMUS)-IDIS, University of Santiago de Compostela, Santiago de Compostela, Spain
| | - Blanca Leticia Rodríguez-Cañete
- Thyroid and Metabolic Diseases Unit (U.E.T.eM.), Department of Medicine, Center for Research in Molecular Medicine and Chronic Diseases (CIMUS)-IDIS, University of Santiago de Compostela, Santiago de Compostela, Spain
| | - Silvia Rodríguez-García
- Thyroid and Metabolic Diseases Unit (U.E.T.eM.), Department of Medicine, Center for Research in Molecular Medicine and Chronic Diseases (CIMUS)-IDIS, University of Santiago de Compostela, Santiago de Compostela, Spain
| | - Encarnación Guillén-Navarro
- Unit of Medical Genetics and Dysmorphology, Division of Pediatrics, Hospital Clínico Universitario Virgen de la Arrixaca, Murcia, Spain
| | - Rosario Domingo-Jiménez
- Section of Neuropediatrics, Division of Pediatrics, Hospital Clínico Universitario Virgen de la Arrixaca, Murcia, Spain
| | - David Araújo-Vilar
- Thyroid and Metabolic Diseases Unit (U.E.T.eM.), Department of Medicine, Center for Research in Molecular Medicine and Chronic Diseases (CIMUS)-IDIS, University of Santiago de Compostela, Santiago de Compostela, Spain
- * E-mail:
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17
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Song Y, Wan X, Gao L, Pan Y, Xie W, Wang H, Guo J. Activated PKR inhibits pancreatic β-cell proliferation through sumoylation-dependent stabilization of P53. Mol Immunol 2015; 68:341-9. [PMID: 26446704 DOI: 10.1016/j.molimm.2015.09.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 08/27/2015] [Accepted: 09/02/2015] [Indexed: 12/20/2022]
Abstract
Double-stranded RNA-dependent protein kinase (PKR) is intimately involved in type 2 diabetes due to its role in insulin resistance in peripheral tissues and anti-proliferative effect on pancreatic β-cells. Activated PKR was found to inhibit β-cell proliferation, partially through accumulation of P53. However the molecular mechanisms underlying PKR-dependent upregulation of P53 remain unknown. The results of the present study showed that PKR can be specifically activated in PKR overexpressing β-cells by a low dosage of the previously synthesized compound 1H-benzimidazole1-ethanol,2,3-dihydro-2-imino-a-(phenoxymethyl)-3-(phenylmethyl)-,monohydrochloride (BEPP), and this led to upregulation of P53 through sumoylation-dependent stability. Activated PKR was found to interact with sumo-conjugating enzyme Ubc9, and P53 sumoylation relies on a PKR-Ubc9 protein-protein interaction. Additionally, a ceramide signal was needed for PKR activation to be triggered by glucolipotoxicity and TNFα stimulation, and stabilization of P53 required endogenous ceramide accumulation. Glucolipotoxicity and pro-inflammatory cytokines therefore promote the sumoylation-dependent stability of P53 via the ceramide/PKR/Ubc9 signalling pathway that is involved in pancreatic β-cell proliferation inhibition in the development of type 2 diabetes.
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Affiliation(s)
- Ying Song
- Department of Respiratory Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, PR China
| | - XiaoMeng Wan
- Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing 210029, PR China
| | - LiLi Gao
- Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing 210029, PR China
| | - Yi Pan
- Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing 210029, PR China
| | - WeiPing Xie
- Department of Respiratory Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, PR China
| | - Hong Wang
- Department of Respiratory Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, PR China.
| | - Jun Guo
- Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing 210029, PR China
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18
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SGK-1 protects kidney cells against apoptosis induced by ceramide and TNF-α. Cell Death Dis 2015; 6:e1890. [PMID: 26379195 PMCID: PMC4650437 DOI: 10.1038/cddis.2015.232] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2015] [Revised: 06/25/2015] [Accepted: 07/06/2015] [Indexed: 12/21/2022]
Abstract
Ceramide regulates several different cellular responses including mechanisms leading to apoptosis. Serum- and glucocorticoid-inducible protein kinase (SGK)-1 is a serine threonine kinase, which activates survival pathways in response to stress stimuli. Recently, we demonstrated an anti-apoptotic role of SGK-1 in human umbilical endothelial cells treated with high glucose. In the present study, since ceramide induces apoptosis by multiple mechanisms in diabetes and its complication such as nephropathy, we aimed to investigate whether SGK-1 may protect even against apoptosis induced by ceramide in kidney cells. Human embryonic kidney (HEK)-293 cells stable transfected with SGK-1 wild type (SGK-1wt) and its dominant negative gene (SGK-1dn) have been used in this study. Apoptotic stimuli were induced by C2-ceramide and TNF-α to increase endogenous synthesis of ceramide. Upon activation with these stimuli, SGK-1wt transfected cells have a statistically significant reduction of apoptosis compared with SGK-1dn cells (P<0.001). This protection was dependent on activation of caspase-3 and Poly-ADP-ribose-polymerase-1 (PARP-1) cleavage. SGK-1 and AKT-1 two highly homologous kinases differently reacted to ceramide treatment, since SGK-1 increases in response to apoptotic stimulus while AKT-1 decreases. This enhancement of SGK-1 was dependent on p38-mitogen-activated-protein kinases (p38MAPK), cyclic-adenosine-monophosphate/protein kinase A (cAMP/PKA) and phosphoinositide-3-kinase (PI3K) pathways. Especially, by using selective LY294002 inhibitor, we demonstrated that the most involved pathway in the SGK-1 mediated process of protection was PI3K. Treatment with inhibitor of SGK-1 (GSK650394) significantly enhanced TNF-α-dependent apoptosis in HEK-293 cells overexpressing SGK-1wt. Caspase-3, -8 and -9 selective inhibitors confirmed that SGK-1 reduced the activation of caspase-dependent apoptosis, probably by both intrinsic and extrinsic pathways. In conclusion, we demonstrated that in kidney cells, overexpression of SGK-1 is protective against ceramide-induced apoptosis and the role of SGK-1 can be potentially explored as a therapeutic target in conditions like diabetes, where ceramide levels are increased.
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19
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Noel A, Ingrand S, Barrier L. Inhibition of GSK3β by pharmacological modulation of sphingolipid metabolism occurs independently of ganglioside disturbance in a cellular model of Alzheimer's disease. Exp Neurol 2015; 271:308-18. [PMID: 26115843 DOI: 10.1016/j.expneurol.2015.06.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 06/19/2015] [Accepted: 06/22/2015] [Indexed: 12/11/2022]
Abstract
Accumulating evidence implicates ganglioside and/or related-sphingolipid disturbance in the pathogenesis of Alzheimer's disease (AD). However, it is not known whether these lipidic alterations are connected with other important features of AD, such as deregulated insulin/Akt/GSK3 signaling. In this study, we have treated neuroglioma cells expressing the double Swedish mutation of human amyloid precursor protein (H4APPsw) with several glycosphingolipid (GSL)-modulating agents, and we have analyzed the impact of the aberrant ganglioside composition on the GSK3 activation state. We found that both ceramide analogs D- and L-PDMP (1-phenyl 2-decanoylamino-3-morpholino-1-propanol), which have opposite effects on ganglioside synthesis, selectively inhibited GSK3β via Ser9 phosphorylation independently of the upstream insulin/Akt pathway. Conversely, the iminosugar N-butyldeoxynojirimycin (NB-DNJ) which displayed similar reduction of gangliosides as D-PDMP, did not affect the phosphorylation state of GSK3β. Concurrently, while NB-DNJ did not modify the cellular ceramide content, both PDMP enantiomers strongly and equally reduced the levels of long-chain ceramide species. Altogether, our findings led us to hypothesize that the PDMP-induced altered ganglioside composition is not the principal mechanism involved in the inhibition of GSK3β, but seems to implicate, at least in part, their ability to reduce ceramide levels. Nevertheless, this study provides new information regarding the possibilities to target GSK3β through modulation of sphingolipid metabolism.
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Affiliation(s)
- Anastasia Noel
- Université Laval, Faculté de médecine, Département de Psychiatrie et Neurosciences, Québec, QC, Canada; Centre Hospitalier de l'Université Laval, Axe Neurosciences, 2705 Boulevard Laurier, Québec, QC G1V 4G2, Canada; University of Poitiers, Groupe de Recherche sur le Vieillissement Cérébral, GRéViC EA 3808, Poitiers, France
| | - Sabrina Ingrand
- Université de Poitiers, UFR Médecine & Pharmacie, Service de Biochimie et Toxicologie, 6 rue de la Milétrie, TSA 51115, 86073 Poitiers cedex 9, France
| | - Laurence Barrier
- Université de Poitiers, UFR Médecine & Pharmacie, Service de Biochimie et Toxicologie, 6 rue de la Milétrie, TSA 51115, 86073 Poitiers cedex 9, France.
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20
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Hamada Y, Nagasaki H, Fujiya A, Seino Y, Shang QL, Suzuki T, Hashimoto H, Oiso Y. Involvement of de novo ceramide synthesis in pro-inflammatory adipokine secretion and adipocyte–macrophage interaction. J Nutr Biochem 2014; 25:1309-16. [DOI: 10.1016/j.jnutbio.2014.07.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Revised: 05/14/2014] [Accepted: 07/24/2014] [Indexed: 01/28/2023]
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21
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Tsuchiya A, Nagaya H, Kanno T, Nishizaki T. Oleic acid stimulates glucose uptake into adipocytes by enhancing insulin receptor signaling. J Pharmacol Sci 2014; 126:337-43. [PMID: 25391857 DOI: 10.1254/jphs.14182fp] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
The present study investigated cis-unsaturated free fatty acid (FFA)-regulated glucose uptake. In the cell-free assay of protein tyrosine phosphatase 1B (PTP1B), cis-unsaturated FFAs such as linoleic, linolenic, and oleic acid significantly suppressed PTP1B activity in a concentration (1 - 100 μM)-dependent manner, with the highest potential for oleic acid. Oleic acid (1 μM) stimulated insulin (0.1 nM)-induced phosphorylation of the insulin receptor at Tyr1185 and increased insulin (0.1 nM)-induced phosphorylation of Akt at Thr308 and Ser473 in differentiated 3T3-L1-GLUT4myc adipocytes. In the föerster resonance energy transfer analysis, oleic acid activated Rac1 in PC-12 cells, which is inhibited by the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin, the 3-phosphoinositide-dependent protein kinase-1 (PDK1) inhibitor BX912, or the Akt inhibitor MK2206. Oleic acid (1 μM) significantly increased insulin (0.1 nM)-stimulated glucose uptake in 3T3-L1-GLUT4myc adipocytes, although oleic acid by itself had no effect on the glucose uptake. Taken together, the results of the present study show that oleic acid enhances insulin receptor signaling through a pathway along an insulin receptor/PI3K/PDK1/Akt/Rac1 axis in association with PTP1B inhibition and facilitates insulin-induced glucose uptake into adipocytes.
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Affiliation(s)
- Ayako Tsuchiya
- Division of Bioinformation, Department of Physiology, Institute for Advanced Medical Sciences, Hyogo College of Medicine, Japan
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Kraft ML, Klitzing HA. Imaging lipids with secondary ion mass spectrometry. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1841:1108-19. [PMID: 24657337 DOI: 10.1016/j.bbalip.2014.03.003] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Revised: 03/11/2014] [Accepted: 03/12/2014] [Indexed: 10/25/2022]
Abstract
This review discusses the application of time-of-flight secondary ion mass spectrometry (TOF-SIMS) and magnetic sector SIMS with high lateral resolution performed on a Cameca NanoSIMS 50(L) to imaging lipids. The similarities between the two SIMS approaches and the differences that impart them with complementary strengths are described, and various strategies for sample preparation and to optimize the quality of the SIMS data are presented. Recent reports that demonstrate the new insight into lipid biochemistry that can be acquired with SIMS are also highlighted. This article is part of a Special Issue entitled Tools to study lipid functions.
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Affiliation(s)
- Mary L Kraft
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
| | - Haley A Klitzing
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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23
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Alternative splicing programs in prostate cancer. Int J Cell Biol 2013; 2013:458727. [PMID: 23983695 PMCID: PMC3747374 DOI: 10.1155/2013/458727] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Accepted: 07/11/2013] [Indexed: 12/31/2022] Open
Abstract
Prostate cancer (PCa) remains one of the most frequent causes of death for cancer in the male population. Although the initial antiandrogenic therapies are efficacious, PCa often evolves into a hormone-resistant, incurable disease. The genetic and phenotypic heterogeneity of this type of cancer renders its diagnosis and cure particularly challenging. Mounting evidence indicates that alternative splicing, the process that allows production of multiple mRNA variants from each gene, contributes to the heterogeneity of the disease. Key genes for the biology of normal and neoplastic prostate cells, such as those encoding for the androgen receptor and cyclin D1, are alternatively spliced to yield protein isoforms with different or even opposing functions. This review illustrates some examples of genes whose alternative splicing regulation is relevant to PCa biology and discusses the possibility to exploit alternative splicing regulation as a novel tool for prognosis, diagnosis, and therapeutic approaches to PCa.
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24
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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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Obanda DN, Hernandez A, Ribnicky D, Yu Y, Zhang XH, Wang ZQ, Cefalu WT. Bioactives of Artemisia dracunculus L. mitigate the role of ceramides in attenuating insulin signaling in rat skeletal muscle cells. Diabetes 2012; 61:597-605. [PMID: 22315320 PMCID: PMC3282822 DOI: 10.2337/db11-0396] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Ectopic lipids in peripheral tissues have been implicated in attenuating insulin action in vivo. The botanical extract of Artemisia dracunculus L. (PMI 5011) improves insulin action, yet the precise mechanism is not known. We sought to determine whether the mechanism by which PMI 5011 improves insulin signaling is through regulation of lipid metabolism. After differentiation, cells were separately preincubated with free fatty acids (FFAs) and ceramide C2, and the effects on glycogen content, insulin signaling, and ceramide profiles were determined. The effect of PMI 5011 on ceramide accumulation and ceramide-induced inhibition of insulin signaling was evaluated. FFAs resulted in increased levels of total ceramides and ceramide species in L6 myotubes. Saturated FFAs and ceramide C2 inhibited insulin-stimulated phosphorylation of protein kinase B/Akt and reduced glycogen content. PMI 5011 had no effect on ceramide formation or accumulation but increased insulin sensitivity via restoration of Akt phosphorylation. PMI 5011 also attenuated the FFA-induced upregulation of a negative inhibitor of insulin signaling, i.e., protein tyrosine phosphatase 1B (PTP1B), and increased phosphorylation of PTP1B. PMI 5011 attenuates the reduction in insulin signaling induced by ceramide accumulation, but the mechanism of improved insulin signaling is independent of ceramide formation.
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Affiliation(s)
- Diana N Obanda
- Botanical Research Center, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, Louisiana, USA
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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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Pihlajamäki J, Lerin C, Itkonen P, Boes T, Floss T, Schroeder J, Dearie F, Crunkhorn S, Burak F, Jimenez-Chillaron JC, Kuulasmaa T, Miettinen P, Park PJ, Nasser I, Zhao Z, Zhang Z, Xu Y, Wurst W, Ren H, Morris AJ, Stamm S, Goldfine AB, Laakso M, Patti ME. Expression of the splicing factor gene SFRS10 is reduced in human obesity and contributes to enhanced lipogenesis. Cell Metab 2011; 14:208-18. [PMID: 21803291 PMCID: PMC3167228 DOI: 10.1016/j.cmet.2011.06.007] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 11/24/2010] [Accepted: 06/02/2011] [Indexed: 01/13/2023]
Abstract
Alternative mRNA splicing provides transcript diversity and may contribute to human disease. We demonstrate that expression of several genes regulating RNA processing is decreased in both liver and skeletal muscle of obese humans. We evaluated a representative splicing factor, SFRS10, downregulated in both obese human liver and muscle and in high-fat-fed mice, and determined metabolic impact of reduced expression. SFRS10-specific siRNA induces lipogenesis and lipid accumulation in hepatocytes. Moreover, Sfrs10 heterozygous mice have increased hepatic lipogenic gene expression, VLDL secretion, and plasma triglycerides. We demonstrate that LPIN1, a key regulator of lipid metabolism, is a splicing target of SFRS10; reduced SFRS10 favors the lipogenic β isoform of LPIN1. Importantly, LPIN1β-specific siRNA abolished lipogenic effects of decreased SFRS10 expression. Together, our results indicate that reduced expression of SFRS10, as observed in tissues from obese humans, alters LPIN1 splicing, induces lipogenesis, and therefore contributes to metabolic phenotypes associated with obesity.
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Affiliation(s)
- Jussi Pihlajamäki
- Research Division, Joslin Diabetes Center, Harvard Medical School, Boston, MA 02215, USA
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Lang F, Ullrich S, Gulbins E. Ceramide formation as a target in beta-cell survival and function. Expert Opin Ther Targets 2011; 15:1061-71. [PMID: 21635197 DOI: 10.1517/14728222.2011.588209] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
INTRODUCTION Ceramide may be synthesized de novo or generated by sphingomyelinase-dependent hydrolysis of sphingomyelin. AREAS COVERED The role of ceramide, ceramide-sensitive signaling and ion channels in β-cell apoptosis, lipotoxicity and amyloid-induced β-cell death. EXPERT OPINION Ceramide participates in β-cell dysfunction and apoptosis after exposure to TNFα, IL-1β and IFN-γ, excessive amyloid and islet amyloid polypeptide or non-esterified fatty acids (lipotoxicity). Knockout of sphingomyelin synthase 1, which converts ceramide to sphingomyelin, leads to impairment of insulin secretion. Increased ceramidase activity or pharmacological inhibition of ceramide synthetase, inhibits β-cell apoptosis. Ceramide contributes to endoplasmatic reticulum (ER) stress, decreased mitochondrial membrane potential in insulin-secreting cells and mitochondrial release of cytochrome c into the cytosol, which are all triggers of apoptotic cell death. Ceramide-dependent signaling involves activation of extracellularly regulated kinases 1 and 2 (ERK1/2), downregulation of Period (Per)-aryl hydrocarbon receptor nuclear translocator (Arnt)-single-minded (Sim) kinase (PASK), activation of okadaic-acid-sensitive protein phosphatase 2A (PP2A) and stimulation of NADPH-oxidase with generation of superoxides and lipid peroxides. Ceramide reduces the activity of voltage gated potassium (Kv)-channels in insulin-secreting cells. The role of ceramide in β-cell survival and function may be therapeutically relevant, because ceramide formation can be suppressed by pharmacological inhibition of ceramide synthetase and/or sphingomyelinase.
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Affiliation(s)
- Florian Lang
- University of Tübingen, Institute of Physiology, Germany.
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Hu W, Ross J, Geng T, Brice SE, Cowart LA. Differential regulation of dihydroceramide desaturase by palmitate versus monounsaturated fatty acids: implications for insulin resistance. J Biol Chem 2011; 286:16596-605. [PMID: 21454530 PMCID: PMC3089502 DOI: 10.1074/jbc.m110.186916] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2010] [Revised: 02/18/2011] [Indexed: 11/06/2022] Open
Abstract
Much data implicate saturated fatty acids in deleterious processes associated with obesity, diabetes, and the metabolic syndrome. Many of these changes may be due to aberrant generation of bioactive lipids when saturated fatty acid availability to tissues is increased. On the other hand, studies are emerging that implicate the monounsaturated fatty acid oleate in protection from saturated fat mediated toxicity; however, the mechanisms are not well understood. Our data demonstrate a novel role for palmitate in increasing mRNA encoding DES1, which is the enzyme responsible for generating ceramide from its precursor dihydroceramide and thus controls synthesis of the bioactive lipid ceramide. Moreover, co-treatment with oleate prevented the increase in ceramide, and this occurred through attenuation of the increase in message and activity of DES1. Knockdown of DES1 also protected from palmitate-induced insulin resistance, and overexpression of this enzyme ameliorated the protective effect of oleate. Together, these findings provide insight into the mechanisms of oleate-mediated protection against metabolic disease and provide novel evidence for fatty acid-mediated regulation of a key enzyme of ceramide biosynthesis.
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Affiliation(s)
- Wei Hu
- From the Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29403 and
| | - Jessica Ross
- From the Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29403 and
| | - Tuoyu Geng
- From the Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29403 and
| | - Sarah E. Brice
- From the Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29403 and
| | - L. Ashley Cowart
- From the Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29403 and
- the Ralph H. Johnson Veterans Affairs Medical Center, Charleston, South Carolina 29403
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Alonso-Chamorro M, Nieto-Vazquez I, Montori-Grau M, Gomez-Foix AM, Fernandez-Veledo S, Lorenzo M. New emerging role of protein-tyrosine phosphatase 1B in the regulation of glycogen metabolism in basal and TNF-α-induced insulin-resistant conditions in an immortalised muscle cell line isolated from mice. Diabetologia 2011; 54:1157-68. [PMID: 21311858 DOI: 10.1007/s00125-011-2057-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Accepted: 12/22/2010] [Indexed: 10/18/2022]
Abstract
AIMS/HYPOTHESIS Protein-tyrosine phosphatase 1B (PTP1B) negatively regulates insulin action, promoting attenuation of the insulin signalling pathway. The production of this phosphatase is enhanced in insulin-resistant states, such as obesity and type 2 diabetes, where high levels of proinflammatory cytokines (TNF-α, IL-6) are found. In these metabolic conditions, insulin action on glycogen metabolism in skeletal muscle is greatly impaired. We addressed the role of PTP1B on glycogen metabolism in basal and insulin-resistant conditions promoted by TNF-α. METHODS We studied the effect of TNF-α in the presence and absence of insulin on glycogen content and synthesis, glycogen synthase (GS) and glycogen phosphorylase (GP) activities and on glycogen synthesis and degradation signalling pathways. For this purpose we used immortalised cell lines isolated from skeletal muscle from mice lacking PTP1B. RESULTS Absence of PTP1B caused activation of GS and GP with a net glycogenolytic effect, reflected in lower amounts of glycogen and activation of the glycogenolytic signalling pathway, with higher rates of phosphorylation of cyclic adenosine monophosphate-dependent kinase (PKA), phosphorylase kinase (PhK) and GP phosphorylation. Nevertheless, insulin action was strongly enhanced in Ptp1b (also known as Ptpn1)(-/-) cells in terms of glycogen content, synthesis, GS activation rates and GS Ser641 dephosphorylation. Treatment with TNF-α augmented the activity ratios of both GS and GP, and impaired insulin stimulation of glycogen synthesis in wild-type myocytes, whereas Ptp1b (-/-) myocytes restored this inhibitory effect. We report a glycogenolytic effect of TNF-α, as demonstrated by greater activation of the degradation signalling cascade PKA/PhK/GP. In our model, this effect is mediated by the activation of PKA. CONCLUSIONS/INTERPRETATION We provide new data about the role of PTP1B in glycogen metabolism and confirm the beneficial effect that absence of the phosphatase confers against an insulin-resistant condition.
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Affiliation(s)
- M Alonso-Chamorro
- Department of Biochemistry and Molecular Biology II, Faculty of Pharmacy, Universidad Complutense de Madrid, 28040 Madrid, Spain.
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32
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Measles virus-induced immunosuppression: from effectors to mechanisms. Med Microbiol Immunol 2010; 199:227-37. [DOI: 10.1007/s00430-010-0152-3] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2010] [Indexed: 12/11/2022]
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Gassert E, Avota E, Harms H, Krohne G, Gulbins E, Schneider-Schaulies S. Induction of membrane ceramides: a novel strategy to interfere with T lymphocyte cytoskeletal reorganisation in viral immunosuppression. PLoS Pathog 2009; 5:e1000623. [PMID: 19834551 PMCID: PMC2757718 DOI: 10.1371/journal.ppat.1000623] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2009] [Accepted: 09/17/2009] [Indexed: 01/16/2023] Open
Abstract
Silencing of T cell activation and function is a highly efficient strategy of immunosuppression induced by pathogens. By promoting formation of membrane microdomains essential for clustering of receptors and signalling platforms in the plasma membrane, ceramides accumulating as a result of membrane sphingomyelin breakdown are not only essential for assembly of signalling complexes and pathogen entry, but also act as signalling modulators, e. g. by regulating relay of phosphatidyl-inositol-3-kinase (PI3K) signalling. Their role in T lymphocyte functions has not been addressed as yet. We now show that measles virus (MV), which interacts with the surface of T cells and thereby efficiently interferes with stimulated dynamic reorganisation of their actin cytoskeleton, causes ceramide accumulation in human T cells in a neutral (NSM) and acid (ASM) sphingomyelinase-dependent manner. Ceramides induced by MV, but also bacterial sphingomyelinase, efficiently interfered with formation of membrane protrusions and T cell spreading and front/rear polarisation in response to beta1 integrin ligation or alphaCD3/CD28 activation, and this was rescued upon pharmacological or genetic ablation of ASM/NSM activity. Moreover, membrane ceramide accumulation downmodulated chemokine-induced T cell motility on fibronectin. Altogether, these findings highlight an as yet unrecognised concept of pathogens able to cause membrane ceramide accumulation to target essential processes in T cell activation and function by preventing stimulated actin cytoskeletal dynamics.
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Affiliation(s)
- Evelyn Gassert
- Institute for Virology and Immunobiology, University of Würzburg, Würzburg, Germany
| | - Elita Avota
- Institute for Virology and Immunobiology, University of Würzburg, Würzburg, Germany
| | - Harry Harms
- Institute for Virology and Immunobiology, University of Würzburg, Würzburg, Germany
| | - Georg Krohne
- Department of Electron Microscopy, University of Würzburg, Würzburg, Germany
| | - Erich Gulbins
- Department for Molecular Biology, University of Essen, Essen, Germany
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Tazi J, Bakkour N, Stamm S. Alternative splicing and disease. BIOCHIMICA ET BIOPHYSICA ACTA 2009; 1792:14-26. [PMID: 18992329 PMCID: PMC5632948 DOI: 10.1016/j.bbadis.2008.09.017] [Citation(s) in RCA: 381] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2008] [Revised: 09/19/2008] [Accepted: 09/30/2008] [Indexed: 12/11/2022]
Abstract
Almost all protein-coding genes are spliced and their majority is alternatively spliced. Alternative splicing is a key element in eukaryotic gene expression that increases the coding capacity of the human genome and an increasing number of examples illustrates that the selection of wrong splice sites causes human disease. A fine-tuned balance of factors regulates splice site selection. Here, we discuss well-studied examples that show how a disturbance of this balance can cause human disease. The rapidly emerging knowledge of splicing regulation now allows the development of treatment options.
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Affiliation(s)
- Jamal Tazi
- University of Montpellier II, Institute of Molecular Genetics, Centre Nationale de Recherche Scientifique, 1919 Route de Mende, France
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35
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Deevska GM, Rozenova KA, Giltiay NV, Chambers MA, White J, Boyanovsky BB, Wei J, Daugherty A, Smart EJ, Reid MB, Merrill AH, Nikolova-Karakashian M. Acid Sphingomyelinase Deficiency Prevents Diet-induced Hepatic Triacylglycerol Accumulation and Hyperglycemia in Mice. J Biol Chem 2008; 284:8359-68. [PMID: 19074137 DOI: 10.1074/jbc.m807800200] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Acid sphingomyelinase plays important roles in ceramide homeostasis, which has been proposed to be linked to insulin resistance. To test this association in vivo, acid sphingomyelinase deletion (asm(-/-)) was transferred to mice lacking the low density lipoprotein receptor (ldlr(-/-)), and then offsprings were placed on control or modified (enriched in saturated fat and cholesterol) diets for 10 weeks. The modified diet caused hypercholesterolemia in all genotypes; however, in contrast to asm(+/+)/ldlr(-/-), the acid sphingomyelinase-deficient littermates did not display hepatic triacylglyceride accumulation, although sphingomyelin and other sphingolipids were substantially elevated, and the liver was enlarged. asm(-/-)/ldlr(-/-) mice on a modified diet did not accumulate body fat and were protected against diet-induced hyperglycemia and insulin resistance. Experiments with hepatocytes revealed that acid sphingomyelinase regulates the partitioning of the major fatty acid in the modified diet, palmitate, into two competitive and inversely related pools, triacylglycerides and sphingolipids, apparently via modulation of serine palmitoyltransferase, a rate-limiting enzyme in de novo sphingolipid synthesis. These studies provide evidence that acid sphingomyelinase activity plays an essential role in the regulation of glucose metabolism by regulating the hepatic accumulation of triacylglycerides and sphingolipids during consumption of a diet rich in saturated fats.
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Affiliation(s)
- Gergana M Deevska
- Departments of Physiology, Pediatrics, and Internal Medicine, University of Kentucky College of Medicine, Lexington, Kentucky 40536, USA
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Abstract
PURPOSE OF REVIEW Acute exposure to fatty acids causes insulin resistance in muscle, and excess dietary lipid and obesity are also strongly associated with muscle insulin resistance. Relevant mechanisms, however, are still not fully elucidated. Here we examine the latest evidence as to why lipids might accumulate in muscle and the possible mechanisms for lipid-induced insulin resistance. RECENT FINDINGS Muscle lipid metabolites such as long chain fatty acid coenzyme As, diacylglycerol and ceramides may impair insulin signalling directly. Crosstalk between inflammatory signalling pathways and insulin signalling pathways, mitochondrial dysfunction and oxidative stress have also been put forward as major contributors to the development or maintenance of lipid-induced insulin resistance in muscle. Several animal models with gene deletions in pathways of fatty acid synthesis and storage also show increased metabolic rate, reduced intramuscular lipid storage and improved insulin action when challenged with a high lipid load. SUMMARY Studies in genetic and dietary obese animal models, genetically modified animals and humans with obesity or type 2 diabetes suggest plausible mechanisms for effects of fatty acids, lipid metabolites, inflammatory pathways and mitochondrial dysfunction on insulin action in muscle. Many of these mechanisms, however, have been demonstrated in situations in which lipid accumulation (obesity) already exists. Whether the initial events leading to muscle insulin resistance are direct effects of fatty acids in muscle or are secondary to lipid accumulation in adipose tissue or liver remains to be clarified.
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Affiliation(s)
- Edward W Kraegen
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Sydney, Australia.
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37
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Abstract
Most of the previous work on the sphingolipid ceramide has been devoted to its function as an apoptosis inducer. Recent studies, however, have shown that in stem cells, ceramide has additional nonapoptotic functions. In this article, ceramide signaling will be reviewed in light of 'systems interface biology': as an interconnection of sphingolipid metabolism, membrane biophysics and cell signaling. The focus will be on the metabolic interconversion of ceramide and sphingomyelin or sphingosine-1-phosphate. Lipid rafts and sphingolipid-induced protein scaffolds will be discussed as a membrane interface for lipid-controlled cell signaling. Ceramide/sphingomyelin and ceramide/sphingosine-1-phosphate-interdependent cell-signaling pathways are significant for the regulation of cell polarity, apoptosis and/or proliferation, and as novel pharmacologic targets in cancer and stem cells.
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Affiliation(s)
- Erhard Bieberich
- Institute of Molecular Medicine & Genetics, School of Medicine, Medical College of Georgia, 1120 15th Street, Room CB-2803, Augusta, GA 30912, USA
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Roles of l-serine and sphingolipid synthesis in brain development and neuronal survival. Prog Lipid Res 2008; 47:188-203. [PMID: 18319065 DOI: 10.1016/j.plipres.2008.01.003] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2007] [Revised: 11/30/2007] [Accepted: 01/17/2008] [Indexed: 01/14/2023]
Abstract
Sphingolipids represent a class of membrane lipids that contain a hydrophobic ceramide chain as its common backbone structure. Sphingolipid synthesis requires two simple components: l-serine and palmitoyl CoA. Although l-serine is classified as a non-essential amino acid, an external supply of l-serine is essential for the synthesis of sphingolipids and phosphatidylserine (PS) in particular types of central nervous system (CNS) neurons. l-Serine is also essential for these neurons to undergo neuritogenesis and to survive. Biochemical analysis has shown that l-serine is synthesized from glucose and released by astrocytes but not by neurons, which is the major reason why this amino acid is an essential amino acid for neurons. Biosynthesis of membrane lipids, such as sphingolipids, PS, and phosphatidylethanolamine (PE), in neurons is completely dependent on this astrocytic factor. Recent advances in lipid biology research using transgenic mice have demonstrated that synthesis of endogenous l-serine and neuronal sphingolipids is essential for brain development. In this review, we discuss the metabolic system that coordinates sphingolipid synthesis with the l-serine synthetic pathway between neurons and glia. We also discuss the crucial roles of the metabolic conversion of l-serine to sphingolipids in neuronal development and survival. Human diseases associated with serine and sphingolipid biosynthesis are also discussed.
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Revil T, Toutant J, Shkreta L, Garneau D, Cloutier P, Chabot B. Protein kinase C-dependent control of Bcl-x alternative splicing. Mol Cell Biol 2007; 27:8431-41. [PMID: 17923691 PMCID: PMC2169420 DOI: 10.1128/mcb.00565-07] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2007] [Revised: 05/07/2007] [Accepted: 09/19/2007] [Indexed: 02/07/2023] Open
Abstract
The alternative splicing of Bcl-x generates the proapoptotic Bcl-x(S) protein and the antiapoptotic isoform Bcl-x(L). Bcl-x splicing is coupled to signal transduction, since ceramide, hormones, and growth factors alter the ratio of the Bcl-x isoforms in different cell lines. Here we report that the protein kinase C (PKC) inhibitor and apoptotic inducer staurosporine switches the production of Bcl-x towards the x(S) mRNA isoform in 293 cells. The increase in Bcl-x(S) elicited by staurosporine likely involves signaling events that affect splicing decisions, because it requires active transcription and no new protein synthesis and is independent of caspase activation. Moreover, the increase in Bcl-x(S) is reproduced with more specific inhibitors of PKC. Alternative splicing of the receptor tyrosine kinase gene Axl is similarly affected by staurosporine in 293 cells. In contrast to the case for 293 cells, PKC inhibitors do not influence the alternative splicing of Bcl-x and Axl in cancer cell lines, suggesting that these cells have sustained alterations that uncouple splicing decisions from PKC-dependent signaling. Using minigenes, we show that an exonic region located upstream of the Bcl-x(S) 5' splice site is important to mediate the staurosporine shift in Bcl-x splicing. When transplanted to other alternative splicing units, portions of this region confer splicing modulation and responsiveness to staurosporine, suggesting the existence of factors that couple splicing decisions with PKC signaling.
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Affiliation(s)
- Timothée Revil
- RNA/RNP Group, Département de Microbiologie et d'Infectiologie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
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40
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Stamm S. Regulation of alternative splicing by reversible protein phosphorylation. J Biol Chem 2007; 283:1223-7. [PMID: 18024427 DOI: 10.1074/jbc.r700034200] [Citation(s) in RCA: 184] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The vast majority of human protein-coding genes are subject to alternative splicing, which allows the generation of more than one protein isoform from a single gene. Cells can change alternative splicing patterns in response to a signal, which creates protein variants with different biological properties. The selection of alternative splice sites is governed by the dynamic formation of protein complexes on the processed pre-mRNA. A unique set of these splicing regulatory proteins assembles on different pre-mRNAs, generating a "splicing" or "messenger ribonucleoprotein code" that determines exon recognition. By influencing protein/protein and protein/RNA interactions, reversible protein phosphorylation modulates the assembly of regulatory proteins on pre-mRNA and therefore contributes to the splicing code. Studies of the serine/arginine-rich protein class of regulators identified different kinases and protein phosphatase 1 as the molecules that control reversible phosphorylation, which controls not only splice site selection, but also the localization of serine/arginine-rich proteins and mRNA export. The involvement of protein phosphatase 1 explains why second messengers like cAMP and ceramide that control the activity of this phosphatase influence alternative splicing. The emerging mechanistic links between splicing regulatory proteins and known signal transduction pathways now allow in detail the understanding how cellular signals modulate gene expression by influencing alternative splicing. This knowledge can be applied to human diseases that are caused by the selection of wrong splice sites.
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Affiliation(s)
- Stefan Stamm
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, 741 South Limestone, Lexington, KY 40536-0509, USA.
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Marchesini N, Jones JA, Hannun YA. Confluence induced threonine41/serine45 phospho-beta-catenin dephosphorylation via ceramide-mediated activation of PP1cgamma. Biochim Biophys Acta Mol Cell Biol Lipids 2007; 1771:1418-28. [PMID: 17996206 DOI: 10.1016/j.bbalip.2007.10.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2007] [Revised: 09/14/2007] [Accepted: 10/01/2007] [Indexed: 12/15/2022]
Abstract
It was previously observed that cell confluence induced up-regulation of neutral sphingomyelinase 2 (nSMase2) and increased ceramide levels [Marchesini N., Osta W., Bielawski J., Luberto C., Obeid L.M. and Hannun Y.A. (2004) J. Biol. Chem., 279, 25101-11]. In this study, we show that, in MCF7 cells, confluence induces the dephosphorylation of phosphorylated-beta-catenin at threonine41/serine45. The effect of confluence on beta-catenin dephosphorylation was prevented by down regulation of nSMase2 using siRNA; reciprocally, exogenous addition of short or very long chain ceramides induced dephosphorylation of beta-catenin. The serine/threonine protein phosphatase inhibitors calyculin A and okadaic acid prevented beta-catenin dephosphorylation during confluence. The specific phosphatase involved was determined by studies using siRNA against the major serine/threonine phosphatases, and the results showed that a specific siRNA against PP1cgamma prevented dephosphorylation of beta-catenin. Moreover, exogenous ceramides and confluence were found to induce the translocation of PP1cgamma to the plasma membrane. All together these results establish: A) a specific intracellular pathway involving the activation of PP1 to mediate the effects of confluence-induced beta-catenin dephosphorylation and B) PP1 as a lipid-regulated protein phosphatase downstream of nSMase2/ceramide. Finally, evidence is provided for a role for this pathway in regulating cell motility during confluence.
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Affiliation(s)
- Norma Marchesini
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, 175 Ashley Ave., POB 250509, Charleston, SC 29425, USA
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