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Lui A, Patel RS, Krause-Hauch M, Sparks RP, Patel NA. Regulation of Human Sortilin Alternative Splicing by Glucagon-like Peptide-1 (GLP1) in Adipocytes. Int J Mol Sci 2023; 24:14324. [PMID: 37762628 PMCID: PMC10531797 DOI: 10.3390/ijms241814324] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Revised: 09/13/2023] [Accepted: 09/15/2023] [Indexed: 09/29/2023] Open
Abstract
Type 2 diabetes mellitus is a chronic metabolic disease with no cure. Adipose tissue is a major site of systemic insulin resistance. Sortilin is a central component of the glucose transporter -Glut4 storage vesicles (GSV) which translocate to the plasma membrane to uptake glucose from circulation. Here, using human adipocytes we demonstrate the presence of the alternatively spliced, truncated sortilin variant (Sort_T) whose expression is significantly increased in diabetic adipose tissue. Artificial-intelligence-based modeling, molecular dynamics, intrinsically disordered region analysis, and co-immunoprecipitation demonstrated association of Sort_T with Glut4 and decreased glucose uptake in adipocytes. The results show that glucagon-like peptide-1 (GLP1) hormone decreases Sort_T. We deciphered the molecular mechanism underlying GLP1 regulation of alternative splicing of human sortilin. Using splicing minigenes and RNA-immunoprecipitation assays, the results show that GLP1 regulates Sort_T alternative splicing via the splice factor, TRA2B. We demonstrate that targeted antisense oligonucleotide morpholinos reduces Sort_T levels and improves glucose uptake in diabetic adipocytes. Thus, we demonstrate that GLP1 regulates alternative splicing of sortilin in human diabetic adipocytes.
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Affiliation(s)
- Ashley Lui
- Department of Molecular Medicine, University of South Florida, Tampa, FL 33612, USA; (A.L.); (M.K.-H.)
| | - Rekha S. Patel
- Research Service, James A. Haley Veterans Hospital, Tampa, FL 33612, USA; (R.S.P.); (R.P.S.)
| | - Meredith Krause-Hauch
- Department of Molecular Medicine, University of South Florida, Tampa, FL 33612, USA; (A.L.); (M.K.-H.)
| | - Robert P. Sparks
- Research Service, James A. Haley Veterans Hospital, Tampa, FL 33612, USA; (R.S.P.); (R.P.S.)
- Department of Medicine, Division of Gastroenterology, UMass Chan Medical School, Worcester, MA 01655, USA
| | - Niketa A. Patel
- Department of Molecular Medicine, University of South Florida, Tampa, FL 33612, USA; (A.L.); (M.K.-H.)
- Research Service, James A. Haley Veterans Hospital, Tampa, FL 33612, USA; (R.S.P.); (R.P.S.)
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Xue J, Ma T, Zhang X. TRA2: The dominant power of alternative splicing in tumors. Heliyon 2023; 9:e15516. [PMID: 37151663 PMCID: PMC10161706 DOI: 10.1016/j.heliyon.2023.e15516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Revised: 03/30/2023] [Accepted: 04/12/2023] [Indexed: 05/09/2023] Open
Abstract
The dysregulation of alternative splicing (AS) is frequently found in cancer and considered as key markers for cancer progression and therapy. Transformer 2 (TRA2), a nuclear RNA binding protein, consists of transformer 2 alpha homolog (TRA2A) and transformer 2 beta homolog (TRA2B), and plays a role in the regulation of pre-mRNA splicing. Growing evidence has been provided that TRA2A and TRA2B are dysregulated in several types of tumors, and participate in the regulation of proliferation, migration, invasion, and chemotherapy resistance in cancer cells through alteration of AS of cancer-related genes. In this review, we highlight the role of TRA2 in tumorigenesis and metastasis, and discuss potential molecular mechanisms how TRA2 influences tumorigenesis and metastasis via controlling AS of pre-mRNA. We propose that TRA2Ais a novel biomarker and therapeutic target for cancer progression and therapy.
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Affiliation(s)
- Jiancheng Xue
- Medical Research Center, Shengjing Hospital of China Medical University, Shenyang, China
- Key Laboratory of Research and Application of Animal Model for Environmental and Metabolic Diseases, Shenyang, China
| | - Tie Ma
- Department of Pathology, Shengjing Hospital of China Medical University, Shenyang, China
- Corresponding author.
| | - Xiaowen Zhang
- Medical Research Center, Shengjing Hospital of China Medical University, Shenyang, China
- Key Laboratory of Research and Application of Animal Model for Environmental and Metabolic Diseases, Shenyang, China
- Corresponding author. Medical Research Center, Shengjing Hospital of China Medical University, #36 Sanhao Street, Heping District, Shenyang, 110004, China.
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Li Y, Zhou J. Roles of silent information regulator 1-serine/arginine-rich splicing factor 10-lipin 1 axis in the pathogenesis of alcohol fatty liver disease. Exp Biol Med (Maywood) 2017; 242:1117-1125. [PMID: 28467182 DOI: 10.1177/1535370217707729] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Alcohol exposure is a major reason of morbidity and mortality all over the world, with much of detrimental consequences attributing to alcoholic liver disease (ALD). With the continued ethanol consumption, alcoholic fatty liver disease (AFLD, the earliest and reversible form of ALD) can further develop to more serious forms of alcoholic liver damage, including alcoholic steatohepatitis, fibrosis/cirrhosis, and even eventually progress to hepatocellular carcinoma and liver failure. Furthermore, cell trauma, inflammation, oxidative stress, regeneration, and bacterial translocation are crucial promoters of ethanol-mediated liver lesions. AFLD is characterized by excessive fat deposition in liver induced by excessive drinking, which is related closely to the raised synthesis of fatty acids and triglyceride, reduction of mitochondrial fatty acid β-oxidation, and the aggregation of very-low-density lipoprotein (VLDL). Although little is known about the cellular and molecular mechanisms of AFLD, it seems to be correlated to diverse signal channels. Massive studies have suggested that liver steatosis is closely associated with the inhibition of silent information regulator 1 (SIRT1) and the augment of lipin1 β/α ratio mediated by ethanol. Recently, serine/arginine-rich splicing factor 10 (SFRS10), a specific molecule functioning in alternative splicing of lipin 1 (LPIN1) pre-mRNAs, has emerged as the central connection between SIRT1 and lipin1 signaling. It seems a new signaling axis, SIRT1-SFRS10-LPIN1 axis, acting in the pathogenesis of AFLD exists. This article aims to further explore the interactions among the above three molecules and their influences on the development of AFLD. Impact statement ALD is a major health burden in industrialized countries as well as China. AFLD, the earliest and reversible form of ALD, can progress to hepatitis, fibrosis/cirrhosis, even hepatoma. While the mechanisms, by which ethanol consumption leads to AFLD, are complicated and multiple, and remain incompletely understood. SIRT1, SFRS10, and LIPIN1 had been separately reported to participate in lipid metabolism and the pathogenesis of AFLD. Noteworthy, we found the connection among them via searching articles in PubMed and we had elaborated the connection in detail in this minireview. It seems a new signaling axis, SIRT1-SFRS10-LIPIN1 axis, acting in the pathogenesis of AFLD exists. Further study aimed at SIRT1-SFRS10-LIPIN1 signaling system will possibly offer a more effective therapeutic target for AFLD.
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Affiliation(s)
- Yuanyuan Li
- Department of Infectious Disease, the Third Hospital of Hebei Medical University, Shijiazhuang 050051, China
| | - Junying Zhou
- Department of Infectious Disease, the Third Hospital of Hebei Medical University, Shijiazhuang 050051, China
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Hulse RP, Beazley-Long N, Hua J, Kennedy H, Prager J, Bevan H, Qiu Y, Fernandes ES, Gammons MV, Ballmer-Hofer K, Gittenberger de Groot AC, Churchill AJ, Harper SJ, Brain SD, Bates DO, Donaldson LF. Regulation of alternative VEGF-A mRNA splicing is a therapeutic target for analgesia. Neurobiol Dis 2014; 71:245-59. [PMID: 25151644 PMCID: PMC4194316 DOI: 10.1016/j.nbd.2014.08.012] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Revised: 07/29/2014] [Accepted: 08/06/2014] [Indexed: 12/02/2022] Open
Abstract
Vascular endothelial growth factor-A (VEGF-A) is best known as a key regulator of the formation of new blood vessels. Neutralization of VEGF-A with anti-VEGF therapy e.g. bevacizumab, can be painful, and this is hypothesized to result from a loss of VEGF-A-mediated neuroprotection. The multiple vegf-a gene products consist of two alternatively spliced families, typified by VEGF-A165a and VEGF-A165b (both contain 165 amino acids), both of which are neuroprotective. Under pathological conditions, such as in inflammation and cancer, the pro-angiogenic VEGF-A165a is upregulated and predominates over the VEGF-A165b isoform. We show here that in rats and mice VEGF-A165a and VEGF-A165b have opposing effects on pain, and that blocking the proximal splicing event – leading to the preferential expression of VEGF-A165b over VEGF165a – prevents pain in vivo. VEGF-A165a sensitizes peripheral nociceptive neurons through actions on VEGFR2 and a TRPV1-dependent mechanism, thus enhancing nociceptive signaling. VEGF-A165b blocks the effect of VEGF-A165a. After nerve injury, the endogenous balance of VEGF-A isoforms switches to greater expression of VEGF-Axxxa compared to VEGF-Axxxb, through an SRPK1-dependent pre-mRNA splicing mechanism. Pharmacological inhibition of SRPK1 after traumatic nerve injury selectively reduced VEGF-Axxxa expression and reversed associated neuropathic pain. Exogenous VEGF-A165b also ameliorated neuropathic pain. We conclude that the relative levels of alternatively spliced VEGF-A isoforms are critical for pain modulation under both normal conditions and in sensory neuropathy. Altering VEGF-Axxxa/VEGF-Axxxb balance by targeting alternative RNA splicing may be a new analgesic strategy. The different vegf-a splice variants, VEGF-A165a and VEGF-A165b have pro- and anti-nociceptive actions respectively. Pro-nociceptive actions of VEGF-A165a are dependent on TRPV1. Alternative pre-mRNA splicing underpins peripheral sensitization by VEGF-A isoforms in normal and neuropathic animals.
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Affiliation(s)
- R P Hulse
- Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, UK; Cancer Biology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Queen's Medical Centre, Nottingham NG2 7UH, UK
| | - N Beazley-Long
- Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, UK; School of Life Sciences, The Medical School, University of Nottingham, Queen's Medical Centre, Nottingham NG2 7UH, UK
| | - J Hua
- Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, UK
| | - H Kennedy
- Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, UK
| | - J Prager
- Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, UK
| | - H Bevan
- Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, UK
| | - Y Qiu
- Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, UK
| | | | - M V Gammons
- Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, UK
| | | | | | - A J Churchill
- Clinical Sciences, University of Bristol, Bristol BS1 2LX, UK
| | - S J Harper
- Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, UK
| | - S D Brain
- King's College London, London SE1 9NH, UK
| | - D O Bates
- Cancer Biology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Queen's Medical Centre, Nottingham NG2 7UH, UK.
| | - L F Donaldson
- Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, UK; School of Life Sciences, The Medical School, University of Nottingham, Queen's Medical Centre, Nottingham NG2 7UH, UK.
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5
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Transformer 2β (Tra2β/SFRS10) positively regulates the progression of NSCLC via promoting cell proliferation. J Mol Histol 2014; 45:573-82. [DOI: 10.1007/s10735-014-9582-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2014] [Accepted: 06/11/2014] [Indexed: 10/25/2022]
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Kajita K, Kuwano Y, Kitamura N, Satake Y, Nishida K, Kurokawa K, Akaike Y, Honda M, Masuda K, Rokutan K. Ets1 and heat shock factor 1 regulate transcription of the Transformer 2β gene in human colon cancer cells. J Gastroenterol 2013; 48:1222-33. [PMID: 23361474 DOI: 10.1007/s00535-012-0745-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Accepted: 12/25/2012] [Indexed: 02/04/2023]
Abstract
BACKGROUND Transformer (Tra) 2β is a member of the serine/arginine-rich (SR)-like protein family that regulates alternative splicing of numerous genes in a concentration-dependent manner. Several types of cancer cells up-regulate Tra2β expression, while the regulatory mechanism of Tra2β expression remains to be elucidated. In this study, we examined the transcriptional regulation and possible functions of Tra2β in human colon cancer cells. METHODS We cloned 959 bp-upstream of the human TRA2β 5'-flank into luciferase constructs. Chromatin immunoprecipitation (ChIP) was employed to identify crucial cis element(s) and trans activator(s) of the TRA2β promoter. Tra2β expression in the human colon and colon cancer tissues was examined by immunohistochemistry. RESULTS In response to sodium arsenite, colon cancer cells (HCT116) increased levels of TRA2β1 mRNA encoding a functional, full-length Tra2β with a peak around 6 h without changing its mRNA stability. Transient expression assays using a reporter gene driven by serially truncated TRA2β promoters and Chip assay demonstrated that an Ets1-binding site present at -64 to -55 bp was crucial for basal transcription, while three heat shock elements (HSEs) located at -145 to -99 bp mediated the oxidant-induced transactivation of TRA2β. Tra2β knockdown caused apoptosis of HCT116 cells. Tra2β were preferentially expressed in proliferative compartment of normal human colonic glands and adenocarcinomas, where Ets1 and heat shock factor 1 were also highly expressed. CONCLUSIONS Our results suggest that oxidative stress-responsive Tra2β may play an important role in colon cancer growth.
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Affiliation(s)
- Keisuke Kajita
- Department of Stress Science, Institute of Health Biosciences, The University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
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Karunakaran DKP, Banday AR, Wu Q, Kanadia R. Expression analysis of an evolutionarily conserved alternative splicing factor, Sfrs10, in age-related macular degeneration. PLoS One 2013; 8:e75964. [PMID: 24098751 PMCID: PMC3786888 DOI: 10.1371/journal.pone.0075964] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2013] [Accepted: 08/19/2013] [Indexed: 11/18/2022] Open
Abstract
Age-related macular degeneration (AMD) is the most common cause of blindness in the elderly population. Hypoxic stress created in the micro-environment of the photoreceptors is thought to be the underlying cause that results in the pathophysiology of AMD. However, association of AMD with alternative splicing mediated gene regulation is not well explored. Alternative Splicing is one of the primary mechanisms in humans by which fewer protein coding genes are able to generate a vast proteome. Here, we investigated the expression of a known stress response gene and an alternative splicing factor called Serine-Arginine rich splicing factor 10 (Sfrs10). Sfrs10 is a member of the serine-arginine (SR) rich protein family and is 100% identical at the amino acid level in most mammals. Immunoblot analysis on retinal extracts from mouse, rat, and chicken showed a single immunoreactive band. Further, immunohistochemistry on adult mouse, rat and chicken retinae showed pan-retinal expression. However, SFRS10 was not detected in normal human retina but was observed as distinct nuclear speckles in AMD retinae. This is in agreement with previous reports that show Sfrs10 to be a stress response gene, which is upregulated under hypoxia. The difference in the expression of Sfrs10 between humans and lower mammals and the upregulation of SFRS10 in AMD is further reflected in the divergence of the promoter sequence between these species. Finally, SFRS10+ speckles were independent of the SC35+ SR protein speckles or the HSF1+ stress granules. In all, our data suggests that SFRS10 is upregulated and forms distinct stress-induced speckles and might be involved in AS of stress response genes in AMD.
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Affiliation(s)
| | - Abdul Rouf Banday
- University of Connecticut, Physiology and Neurobiology, Storrs, Connecticut, United States of America
| | - Qian Wu
- University of Connecticut Health Center, Department of Pathology and Laboratory Medicine, Farmington, Connecticut, United States of America
| | - Rahul Kanadia
- University of Connecticut, Physiology and Neurobiology, Storrs, Connecticut, United States of America
- * E-mail:
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8
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Li SJ, Li Y, Cui SC, Qi Y, Zhao JJ, Liu XY, Xu P, Chen XH. Splicing factor transformer-2β (Tra2β) regulates the expression of regulator of G protein signaling 4 (RGS4) gene and is induced by morphine. PLoS One 2013; 8:e72220. [PMID: 23977258 PMCID: PMC3747076 DOI: 10.1371/journal.pone.0072220] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Accepted: 07/08/2013] [Indexed: 12/19/2022] Open
Abstract
Regulator of G protein signaling 4 (RGS4) is a critical modulator of G protein-coupled receptor (GPCR)-mediated signaling and plays important roles in many neural process and diseases. Particularly, drug-induced alteration in RGS4 protein levels is associated with acute and chronic effects of drugs of abuse. However, the precise mechanism underlying the regulation of RGS4 expression is largely unknown. Here, we demonstrated that the expression of RGS4 gene was subject to regulation by alternative splicing of the exon 6. Transformer-2β (Tra2β), an important splicing factor, bound to RGS4 mRNA and increased the relative level of RGS4-1 mRNA isoform by enhancing the inclusion of exon 6. Meanwhile, Tra2β increased the expression of full-length RGS4 protein. In rat brain, Tra2β was co-localized with RGS4 in multiple opioid action-related brain regions. In addition, the acute and chronic morphine treatment induced alteration in the expression level of Tra2β in rat locus coerulus (LC) in parallel to that of RGS4 proteins. It suggests that induction of this splicing factor may contribute to the change of RGS4 level elicited by morphine. Taken together, the results provide the evidence demonstrating the function of Tra2β as a new mediator in opioid-induced signaling pathway via regulating RGS4 expression.
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Affiliation(s)
- Shu-Jing Li
- State Key Laboratory of Medical Neurobiology and Department of Neurobiology,School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, China
- Laboratory of Genomic Physiology and Institutes of Brain Science, Shanghai Medical College of Fudan University, Shanghai, China
| | - Ya Li
- State Key Laboratory of Medical Neurobiology and Department of Neurobiology,School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, China
| | - Shi-chao Cui
- State Key Laboratory of Medical Neurobiology and Department of Neurobiology,School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, China
| | - Yao Qi
- State Key Laboratory of Medical Neurobiology and Department of Neurobiology,School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, China
| | - Jing-Jing Zhao
- State Key Laboratory of Medical Neurobiology and Department of Neurobiology,School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, China
| | - Xiao-Yan Liu
- State Key Laboratory of Medical Neurobiology and Department of Neurobiology,School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, China
| | - Ping Xu
- State Key Laboratory of Medical Neurobiology and Department of Neurobiology,School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, China
| | - Xian-Hua Chen
- State Key Laboratory of Medical Neurobiology and Department of Neurobiology,School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, China
- Laboratory of Genomic Physiology and Institutes of Brain Science, Shanghai Medical College of Fudan University, Shanghai, China
- * E-mail:
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Mende Y, Jakubik M, Riessland M, Schoenen F, Rossbach K, Kleinridders A, Köhler C, Buch T, Wirth B. Deficiency of the splicing factor Sfrs10 results in early embryonic lethality in mice and has no impact on full-length SMN/Smn splicing. Hum Mol Genet 2010; 19:2154-67. [PMID: 20190275 DOI: 10.1093/hmg/ddq094] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The SR-like splicing factor SFRS10 (Htra2-beta1) is well known to influence various alternatively spliced exons without being an essential splicing factor. We have shown earlier that SFRS10 binds SMN1/SMN2 RNA and restores full-length (FL)-SMN2 mRNA levels in vitro. As SMN1 is absent in patients with spinal muscular atrophy (SMA), the level of FL-SMN2 determines the disease severity. Correct splicing of SMN2 can be facilitated by histone deacetylase inhibitors (HDACis) via upregulation of SFRS10. As HDACis are already used in SMA clinical trials, it is crucial to identify the spectrum of alternatively spliced transcripts modulated by SFRS10, because elevated SFRS10 levels may influence or misregulate also other biological processes. To address this issue, we generated a conditional Sfrs10 allele in mice using the Cre/loxP system. The ubiquitous homozygous deletion of Sfrs10, however, resulted in early embryonic lethality around E7.5, indicating an essential role of Sfrs10 during mouse embryogenesis. Deletion of Sfrs10 with recombinant Cre in murine embryonic fibroblasts (MEFs) derived from Sfrs10(fl/fl) embryos increased the low levels of SmnDelta7 3-4-fold, without affecting FL-Smn levels. The weak influence of Sfrs10 on Smn splicing was further proven by a Hb9-Cre driven motor neuron-specific deletion of Sfrs10 in mice, which developed normally without revealing any SMA phenotype. To assess the role of Sfrs10 on FL-SMN2 splicing, we established MEFs from Smn(-/-);SMN2(tg/tg);Sfrs10(fl/fl) embryos. Surprisingly, deletion of Sfrs10 by recombinant Cre showed no impact on SMN2 splicing but increased SMN levels. Our findings highlight the complexity by which alternatively spliced exons are regulated in vivo.
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Affiliation(s)
- Ylva Mende
- Institute of Human Genetics, Center for Molecular Medicine Cologne, University of Cologne, Cologne 50931, Germany
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Watermann DO, Tang Y, Zur Hausen A, Jäger M, Stamm S, Stickeler E. Splicing factor Tra2-beta1 is specifically induced in breast cancer and regulates alternative splicing of the CD44 gene. Cancer Res 2006; 66:4774-80. [PMID: 16651431 DOI: 10.1158/0008-5472.can-04-3294] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The human CD44 gene undergoes extensive alternative splicing of multiple variable exons positioned in a cassette in the middle of the gene. Expression of alternative exons is often restricted to certain tissues and could be associated with tumor progression and metastasis of several human malignancies, including breast cancer. Exon v4 contains multiple copies of a C/A-rich exon enhancer sequence required for optimal inclusion of the exon and binding to the nucleic acid-binding proteins YB-1 and human Tra2-beta1. Here, we show that hTra2-beta1, a member of the extended family of serine/arginine-rich (SR) splicing factors, enhances the in vivo inclusion of CD44 exons v4 and v5. It increased inclusion of exons v4 and v5 and acted synergistically with YB-1. Activation required the C/A-rich enhancer within exon v4. Several other SR proteins had none or only a slight effect on CD44 exon inclusion. In contrast, SC35 inhibited exon usage and antagonized the effects of Tra2 or YB-1. In a matched pair analysis of human breast cancers and their corresponding nonpathologic tissue controls, we found a significant induction of Tra2-beta1 in invasive breast cancer, both on the RNA and protein levels. Together with our functional data, these results suggest an important role for Tra2-beta1 in breast cancer. Induction of this splicing factor might be responsible for splicing of CD44 isoforms associated with tumor progression and metastasis.
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Affiliation(s)
- Dirk O Watermann
- Department of Obstetrics and Gynecology, University of Freiburg, Freiburg, Germany
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Venables JP, Bourgeois CF, Dalgliesh C, Kister L, Stevenin J, Elliott DJ. Up-regulation of the ubiquitous alternative splicing factor Tra2β causes inclusion of a germ cell-specific exon. Hum Mol Genet 2005; 14:2289-303. [PMID: 16000324 DOI: 10.1093/hmg/ddi233] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We have discovered a new exon of the homeodomain-interacting kinase HipK3 that incorporates a premature stop codon and is included only in the human testis. To investigate this, we tested the effects of transfecting cells with green fluorescent protein fusions of RNA-binding proteins implicated in spermatogenesis using a novel assay based on multi-fraction fluorescence-activated cell sorting (MF-FACS). This allows the effect of a controlled titration of any splicing factor on the splicing of endogenous genes to be studied in vivo. We found that Tra2beta recapitulates testis-specific splicing of endogenous HipK3 in a concentration-dependent manner and binds specifically to a long purine-rich sequence in the novel exon. This sequence was also specifically bound by hnRNP A1, hnRNP H, ASF/SF2 and SRp40, but not by 9G8. Consistent with these observations, in vitro studies showed that this sequence shifts splicing to a downstream 5' splice site within a heterologous pre-mRNA substrate in the presence of Tra2beta, ASF/SF2 and SRp40, whereas hnRNP A1 specifically inhibits this choice. By mutating the purine-rich sequence in the context of the HipK3 gene, we also show that it is the major determinant of Tra2beta- and hnRNP A1-mediated regulation. Tra2 is essential for sex determination and spermatogenesis in flies, and Tra2beta protein was most highly expressed in testis out of six mouse tissues, whereas hnRNP A1 is down-regulated during germ cell development. Therefore, our data imply an evolutionarily conserved role for Tra2 proteins in spermatogenesis and suggest that an elevated concentration of Tra2beta may convert it into a tissue-specific splicing factor.
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Affiliation(s)
- Julian P Venables
- Institute of Human Genetics, University of Newcastle upon Tyne, International Centre for Life, Central Parkway, Newcastle upon Tyne NE1 3BZ, UK.
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Abstract
The present study demonstrates a high level of the nuclear Transformer 2alpha (Tra2alpha) protein in adult mouse brain relative to other tissues, including muscle, heart, liver, lungs, kidney and small intestine, suggesting the potential importance of Tra2alpha in neural function. The level of Tra2alpha in mouse cerebrum is developmentally regulated, peaking at neonate stage. In P19 carcinoma cells, Tra2alpha is transiently up-regulated upon retinoic acid (RA) treatment. Although over-expression of Tra2alpha protein alone does not elicit P19 differentiation, under these conditions the response of P19 cells to RA is significantly increased. The results suggest that Tra2alpha proteins may act as a mediator in the signal pathway associated with RA-induced differentiation in P19 cells.
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Affiliation(s)
- Xianhua Chen
- Laboratory of Genomic Physiology, Center for Brain Research, State Key laboratory of Medical Neurobiology, School of Life Sciences, Fudan University, 220 Handan Road, Shanghai 200433, China
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Tsukamoto Y, Matsuo N, Ozawa K, Hori O, Higashi T, Nishizaki J, Tohnai N, Nagata I, Kawano K, Yutani C, Hirota S, Kitamura Y, Stern DM, Ogawa S. Expression of a novel RNA-splicing factor, RA301/Tra2beta, in vascular lesions and its role in smooth muscle cell proliferation. THE AMERICAN JOURNAL OF PATHOLOGY 2001; 158:1685-94. [PMID: 11337366 PMCID: PMC1891943 DOI: 10.1016/s0002-9440(10)64124-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
RA301/Tra2beta, a sequence-specific RNA-binding protein, was first cloned as a stress molecule in re-oxygenated astrocytes. In human vascular tissues, we have found enhanced RA301/Tra2beta expression in coronary artery with intimal thickening, and atherosclerotic aorta. Balloon injury to the rat carotid artery induced RA301/Tra2beta transcripts followed by expression of the antigen, which was detected in medial and neointimal vascular smooth muscle cells (VSMCs). In cultured VSMCs, hypoxia/re-oxygenation caused induction of RA301/Tra2beta and was accompanied by cell proliferation, both of which were blocked by the addition of either diphenyl iodonium, a NADPH oxidase inhibitor, PD98059, a mitogen-activated protein kinase kinase inhibitor, or antisense oligonucleotide for RA301/Tra2beta. Consistent with a link between RA301/Tra2beta and cell proliferation, platelet-derived growth factor also induced expression of RA301/Tra2beta in cultured VSMCS: These data suggest a possible role for RA301/Tra2beta in the regulation of VSMC proliferation, especially in the setting of hypoxia/re-oxygenation-induced cell stress.
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MESH Headings
- Adolescent
- Adult
- Aged
- Animals
- Biphenyl Compounds/pharmacology
- Carotid Arteries/metabolism
- Carotid Arteries/pathology
- Cell Division/drug effects
- Cell Division/physiology
- DNA, Antisense/pharmacology
- Dose-Response Relationship, Drug
- Female
- Flavonoids/pharmacology
- Gene Expression
- Humans
- Infant
- Male
- Middle Aged
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/physiology
- Onium Compounds/pharmacology
- Oxygen/pharmacology
- RNA Splicing
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA-Binding Proteins/genetics
- RNA-Binding Proteins/physiology
- Rats
- Rats, Sprague-Dawley
- Serine-Arginine Splicing Factors
- Superoxides/metabolism
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Affiliation(s)
- Y Tsukamoto
- Department of Pathology and Neurosurgery, National Cardiovascular Center, Suita City, Japan.
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14
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Hofmann Y, Lorson CL, Stamm S, Androphy EJ, Wirth B. Htra2-beta 1 stimulates an exonic splicing enhancer and can restore full-length SMN expression to survival motor neuron 2 (SMN2). Proc Natl Acad Sci U S A 2000; 97:9618-23. [PMID: 10931943 PMCID: PMC16914 DOI: 10.1073/pnas.160181697] [Citation(s) in RCA: 251] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Spinal muscular atrophy (SMA), a common motor neuron disease in humans, results from loss of functional survival motor neuron (SMN1) alleles. A nearly identical copy of the gene, SMN2, fails to provide protection from SMA because of a single translationally silent nucleotide difference in exon 7. This likely disrupts an exonic splicing enhancer and causes exon 7 skipping, leading to abundant production of a shorter isoform, SMN2Delta7. The truncated transcript encodes a less stable protein with reduced self-oligomerization activity that fails to compensate for the loss of SMN1. This report describes the identification of an in vivo regulator of SMN mRNA processing. Htra2-beta1, an SR-like splicing factor and ortholog of Drosophila melanogaster transformer-2, promoted the inclusion of SMN exon 7, which would stimulate full-length SMN2 expression. Htra2-beta1 specifically functioned through and bound an AG-rich exonic splicing enhancer in SMN exon 7. This effect is not species-specific as expression of Htra2-beta1 in human or mouse cells carrying an SMN2 minigene dramatically increased production of full-length SMN2. This demonstrates that SMN2 mRNA processing can be modulated in vivo. Because all SMA patients retain at least one SMN2 copy, these results show that an in vivo modulation of SMN RNA processing could serve as a therapeutic strategy to prevent SMA.
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Affiliation(s)
- Y Hofmann
- Institute of Human Genetics, University of Bonn, Germany
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15
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Kiryu-Seo S, Sasaki M, Yokohama H, Nakagomi S, Hirayama T, Aoki S, Wada K, Kiyama H. Damage-induced neuronal endopeptidase (DINE) is a unique metallopeptidase expressed in response to neuronal damage and activates superoxide scavengers. Proc Natl Acad Sci U S A 2000; 97:4345-50. [PMID: 10759559 PMCID: PMC18244 DOI: 10.1073/pnas.070509897] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/1999] [Indexed: 11/18/2022] Open
Abstract
We isolated a membrane-bound metallopeptidase, DINE (damage-induced neuronal endopeptidase), by differential display PCR using rat normal and axotomized hypoglossal nuclei. The most marked properties of DINE were neuron-specific expression and a striking response to axonal injury in both the central nervous system and peripheral nervous system. For instance, cranial and spinal nerve transection, ischemia, corpus callosum transection, and colchicine treatment increased DINE mRNA expression in the injured neurons, whereas kainate-induced hyperexcitation, immobilization, and osmotic stress failed to up-regulate DINE mRNA. Expression of DINE in COS cells partially inhibited C2-ceramide-induced apoptosis, probably because of the activation of antioxidant enzymes such as Cu/Zn-superoxide dismutase, Mn-superoxide dismutase, and glutathione peroxidase through the proteolytic activity of DINE. These data provide insight into the mechanism of how injured neurons protect themselves against neuronal death.
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Affiliation(s)
- S Kiryu-Seo
- Department of Anatomy, Asahikawa Medical College, 2-1-1-1 Midorigaoka-Higashi, Asahikawa 078-8510, Japan
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