1
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Bushell M. Non-coding RNAs mechanisms enforcing oncogenic programs and allowing establishment of metastatic inches. Toxicol Lett 2021. [DOI: 10.1016/s0378-4274(21)00316-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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2
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Sbarrato T, Horvilleur E, Pöyry T, Hill K, Chaplin LC, Spriggs RV, Stoneley M, Wilson L, Jayne S, Vulliamy T, Beck D, Dokal I, Dyer MJS, Yeomans AM, Packham G, Bushell M, Wagner SD, Willis AE. A ribosome-related signature in peripheral blood CLL B cells is linked to reduced survival following treatment. Cell Death Dis 2016; 7:e2249. [PMID: 27253413 PMCID: PMC5143378 DOI: 10.1038/cddis.2016.148] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Revised: 04/18/2016] [Accepted: 05/02/2016] [Indexed: 01/14/2023]
Abstract
We have used polysome profiling coupled to microarray analysis to examine the translatome of a panel of peripheral blood (PB) B cells isolated from 34 chronic lymphocytic leukaemia (CLL) patients. We have identified a ‘ribosome-related' signature in CLL patients with mRNAs encoding for ribosomal proteins and factors that modify ribosomal RNA, e.g. DKC1 (which encodes dyskerin, a pseudouridine synthase), showing reduced polysomal association and decreased expression of the corresponding proteins. Our data suggest a general impact of dyskerin dysregulation on the translational apparatus in CLL and importantly patients with low dyskerin levels have a significantly shorter period of overall survival following treatment. Thus, translational dysregulation of dyskerin could constitute a mechanism by which the CLL PB B cells acquire an aggressive phenotype and thus have a major role in oncogenesis.
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Affiliation(s)
- T Sbarrato
- Medical Research Council Toxicology Unit, Hodgkin Building, PO Box 138, Lancaster Rd, Leicester LE19HN, UK
| | - E Horvilleur
- Medical Research Council Toxicology Unit, Hodgkin Building, PO Box 138, Lancaster Rd, Leicester LE19HN, UK
| | - T Pöyry
- Medical Research Council Toxicology Unit, Hodgkin Building, PO Box 138, Lancaster Rd, Leicester LE19HN, UK
| | - K Hill
- The Babraham Institute, Babraham, Cambridge, UK
| | - L C Chaplin
- Medical Research Council Toxicology Unit, Hodgkin Building, PO Box 138, Lancaster Rd, Leicester LE19HN, UK
| | - R V Spriggs
- Medical Research Council Toxicology Unit, Hodgkin Building, PO Box 138, Lancaster Rd, Leicester LE19HN, UK
| | - M Stoneley
- Medical Research Council Toxicology Unit, Hodgkin Building, PO Box 138, Lancaster Rd, Leicester LE19HN, UK
| | - L Wilson
- Medical Research Council Toxicology Unit, Hodgkin Building, PO Box 138, Lancaster Rd, Leicester LE19HN, UK
| | - S Jayne
- Department of Cancer Studies, Ernest and Helen Scott Haematology Research Institute, University of Leicester, Lancaster Road, Leicester LE1 7H, UK
| | - T Vulliamy
- Centre for Genomics and Child Health, Blizard Institute, Barts and The London School of Medicine and Dentistry, 4 Newark Street, Whitechapel, London E1 2AT, UK
| | - D Beck
- Department of Cancer Studies, Ernest and Helen Scott Haematology Research Institute, University of Leicester, Lancaster Road, Leicester LE1 7H, UK
| | - I Dokal
- Centre for Genomics and Child Health, Blizard Institute, Barts and The London School of Medicine and Dentistry, 4 Newark Street, Whitechapel, London E1 2AT, UK
| | - M J S Dyer
- Department of Cancer Studies, Ernest and Helen Scott Haematology Research Institute, University of Leicester, Lancaster Road, Leicester LE1 7H, UK
| | - A M Yeomans
- Cancer Research UK Centre, Faculty of Medicine, University of Southampton, Southampton, UK
| | - G Packham
- Cancer Research UK Centre, Faculty of Medicine, University of Southampton, Southampton, UK
| | - M Bushell
- Medical Research Council Toxicology Unit, Hodgkin Building, PO Box 138, Lancaster Rd, Leicester LE19HN, UK
| | - S D Wagner
- Department of Cancer Studies, Ernest and Helen Scott Haematology Research Institute, University of Leicester, Lancaster Road, Leicester LE1 7H, UK
| | - A E Willis
- Medical Research Council Toxicology Unit, Hodgkin Building, PO Box 138, Lancaster Rd, Leicester LE19HN, UK
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3
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Hall AE, Lu WT, Godfrey JD, Antonov AV, Paicu C, Moxon S, Dalmay T, Wilczynska A, Muller PAJ, Bushell M. The cytoskeleton adaptor protein ankyrin-1 is upregulated by p53 following DNA damage and alters cell migration. Cell Death Dis 2016; 7:e2184. [PMID: 27054339 PMCID: PMC4855670 DOI: 10.1038/cddis.2016.91] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Revised: 03/09/2016] [Accepted: 03/15/2016] [Indexed: 12/19/2022]
Abstract
The integrity of the genome is maintained by a host of surveillance and repair mechanisms that are pivotal for cellular function. The tumour suppressor protein p53 is a major component of the DNA damage response pathway and plays a vital role in the maintenance of cell-cycle checkpoints. Here we show that a microRNA, miR-486, and its host gene ankyrin-1 (ANK1) are induced by p53 following DNA damage. Strikingly, the cytoskeleton adaptor protein ankyrin-1 was induced over 80-fold following DNA damage. ANK1 is upregulated in response to a variety of DNA damage agents in a range of cell types. We demonstrate that miR-486-5p is involved in controlling G1/S transition following DNA damage, whereas the induction of the ankyrin-1 protein alters the structure of the actin cytoskeleton and sustains limited cell migration during DNA damage. Importantly, we found that higher ANK1 expression correlates with decreased survival in cancer patients. Thus, these observations highlight ANK1 as an important effector downstream of the p53 pathway.
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Affiliation(s)
- A E Hall
- Medical Research Council (MRC), Toxicology Unit, Leicester, UK
| | - W-T Lu
- Medical Research Council (MRC), Toxicology Unit, Leicester, UK
| | - J D Godfrey
- Medical Research Council (MRC), Toxicology Unit, Leicester, UK
| | - A V Antonov
- Medical Research Council (MRC), Toxicology Unit, Leicester, UK
| | - C Paicu
- The Genome Analysis Centre, Norwich, UK.,School of Computing Sciences, University of East Anglia, Norwich, UK
| | - S Moxon
- The Genome Analysis Centre, Norwich, UK
| | - T Dalmay
- School of Biological Sciences, University of East Anglia, Norwich, UK
| | - A Wilczynska
- Medical Research Council (MRC), Toxicology Unit, Leicester, UK
| | - P A J Muller
- Medical Research Council (MRC), Toxicology Unit, Leicester, UK
| | - M Bushell
- Medical Research Council (MRC), Toxicology Unit, Leicester, UK
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Mura M, Hopkins TG, Michael T, Abd-Latip N, Weir J, Aboagye E, Mauri F, Jameson C, Sturge J, Gabra H, Bushell M, Willis AE, Curry E, Blagden SP. LARP1 post-transcriptionally regulates mTOR and contributes to cancer progression. Oncogene 2015; 34:5025-36. [PMID: 25531318 PMCID: PMC4430325 DOI: 10.1038/onc.2014.428] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Revised: 09/20/2014] [Accepted: 10/21/2014] [Indexed: 12/24/2022]
Abstract
RNA-binding proteins (RBPs) bind to and post-transcriptionally regulate the stability of mRNAs. La-related protein 1 (LARP1) is a conserved RBP that interacts with poly-A-binding protein and is known to regulate 5'-terminal oligopyrimidine tract (TOP) mRNA translation. Here, we show that LARP1 is complexed to 3000 mRNAs enriched for cancer pathways. A prominent member of the LARP1 interactome is mTOR whose mRNA transcript is stabilized by LARP1. At a functional level, we show that LARP1 promotes cell migration, invasion, anchorage-independent growth and in vivo tumorigenesis. Furthermore, we show that LARP1 expression is elevated in epithelial cancers such as cervical and non-small cell lung cancers, where its expression correlates with disease progression and adverse prognosis, respectively. We therefore conclude that, through the post-transcriptional regulation of genes such as mTOR within cancer pathways, LARP1 contributes to cancer progression.
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Affiliation(s)
- M Mura
- Division of Cancer, Department of Surgery and Cancer, Ovarian Cancer Action Research Centre, Imperial College London, Hammersmith Campus, London, UK
| | - T G Hopkins
- Division of Cancer, Department of Surgery and Cancer, Ovarian Cancer Action Research Centre, Imperial College London, Hammersmith Campus, London, UK
| | - T Michael
- Division of Cancer, Department of Surgery and Cancer, Ovarian Cancer Action Research Centre, Imperial College London, Hammersmith Campus, London, UK
| | - N Abd-Latip
- Division of Cancer, Department of Surgery and Cancer, Ovarian Cancer Action Research Centre, Imperial College London, Hammersmith Campus, London, UK
| | - J Weir
- Department of Cellular Pathology, Imperial College Healthcare NHS Trust, Charing Cross Hospital, London, UK
| | - E Aboagye
- Division of Cancer, Department of Surgery and Cancer, Cancer Research UK Laboratories, Imperial College London, Hammersmith Campus, London, UK
| | - F Mauri
- Department of Histopathology, Centre for Pathology, Imperial College London, Hammersmith Campus, London, UK
| | - C Jameson
- Department of Histopathology, University College Hospital, London, UK
| | - J Sturge
- Division of Cancer, Department of Surgery and Cancer, Cancer Research UK Laboratories, Imperial College London, Hammersmith Campus, London, UK
- School of Biological, Biomedical & Environmental Sciences, The Allam Building, University of Hull, Hull, UK
| | - H Gabra
- Division of Cancer, Department of Surgery and Cancer, Ovarian Cancer Action Research Centre, Imperial College London, Hammersmith Campus, London, UK
| | - M Bushell
- MRC Toxicology Unit, Hodgkin Building, University of Leicester, Leicester, UK
| | - A E Willis
- MRC Toxicology Unit, Hodgkin Building, University of Leicester, Leicester, UK
| | - E Curry
- Division of Cancer, Department of Surgery and Cancer, Ovarian Cancer Action Research Centre, Imperial College London, Hammersmith Campus, London, UK
| | - S P Blagden
- Division of Cancer, Department of Surgery and Cancer, Ovarian Cancer Action Research Centre, Imperial College London, Hammersmith Campus, London, UK
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Abstract
MicroRNAs (miRNAs) are one of a growing class of noncoding RNAs that are involved in the regulation of a wide range of metabolic processes including cellular differentiation, cell proliferation and apoptosis. The generation of miRNA is regulated in complex ways, for example by small interfering RNAs (small nucleolar and nuclear RNAs) and various other metabolites. This complexity of control is likely to explain how a relatively small part of the DNA that codes for proteins has enabled the evolution of such complex organisms as mammals. Non-protein-coding DNA is therefore thought to carry the memory of early evolutionary steps that led to progressively complex metabolic controls. Clinically, miRNAs are becoming increasingly important following the recognition that some congenital abnormalities can be traced to defects in miRNA processing. The potential for manipulating metabolism and affecting disease processes by the pharmaceutical or biological targeting of specific miRNA pathways is now being tested. miRNAs are also released into the extracellular milieu after packaging by cells into nano-sized extracellular vesicles. Such vesicles can be taken up by adjacent and possibly more distant cells, thereby allowing coordinated intercellular communication in specific tissues. Extracellular miRNAs found in the blood stream may also serve as novel biomarkers for both diagnosing specific forms of cancer and assessing the likelihood of metastasis, and as powerful prognostic indices for various cancers. Here, we discuss the role of intracellular and extracellular miRNAs in nutritional control of various (patho)physiological processes. In this review, we provide an update of the presentations from the 25th Marabou Symposium (Stockholm, 14-16 June 2013) entitled 'Role of miRNA in health and nutrition', attended by 50 international experts
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Affiliation(s)
- E N M Nolte-'t Hoen
- Department of Biochemistry and Cell Biology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - E Van Rooij
- Hubrecht Institute, Koninklijke Nederlandse Academie van Wetenschappen (KNAW), University Medical Center Utrecht, Utrecht, The Netherlands
| | - M Bushell
- Medical Research Council (MRC) Toxicology Unit, University of Leicester, Leicester, UK
| | - C-Y Zhang
- Jiangsu Engineering Research Center for microRNA Biology and Biotechnology, State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, China
| | - R H Dashwood
- Center for Epigenetics and Disease Prevention, Institute of Biosciences & Technology, Texas A&M Health Science Center, Houston, TX, USA
| | - W P T James
- London School of Hygiene and Tropical Medicine, London, UK
| | - C Harris
- Laboratory of Human Carcinogenesis, National Cancer Institute, Center for Cancer Research, National Institutes of Health, Bethesda, MD, USA
| | - D Baltimore
- Department of Biology, California Institute of Technology, Pasadena, CA, USA
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Lu WT, Bushell M. Old case, new leads: miRNA links Kaposi's sarcoma-associated herpesvirus with sepsis. Cell Death Dis 2014; 5:e1560. [PMID: 25476908 PMCID: PMC4454161 DOI: 10.1038/cddis.2014.516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- W-T Lu
- MRC Toxicology Unit, Hodgkin Building, Leicester, UK
| | - M Bushell
- MRC Toxicology Unit, Hodgkin Building, Leicester, UK
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Wilczynska A, Bushell M. The complexity of miRNA-mediated repression. Cell Death Differ 2014; 22:22-33. [PMID: 25190144 DOI: 10.1038/cdd.2014.112] [Citation(s) in RCA: 322] [Impact Index Per Article: 32.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 06/10/2014] [Accepted: 06/25/2014] [Indexed: 01/01/2023] Open
Abstract
Since their discovery 20 years ago, miRNAs have attracted much attention from all areas of biology. These short (∼22 nt) non-coding RNA molecules are highly conserved in evolution and are present in nearly all eukaryotes. They have critical roles in virtually every cellular process, particularly determination of cell fate in development and regulation of the cell cycle. Although it has long been known that miRNAs bind to mRNAs to trigger translational repression and degradation, there had been much debate regarding their precise mode of action. It is now believed that translational control is the primary event, only later followed by mRNA destabilisation. This review will discuss the most recent advances in our understanding of the molecular underpinnings of miRNA-mediated repression. Moreover, we highlight the multitude of regulatory mechanisms that modulate miRNA function.
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Affiliation(s)
- A Wilczynska
- MRC Toxicology Unit, University of Leicester, Leicester, UK
| | - M Bushell
- MRC Toxicology Unit, University of Leicester, Leicester, UK
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Meijer HA, Kong YW, Lu WT, Wilczynska A, Spriggs RV, Robinson SW, Godfrey JD, Willis AE, Bushell M. Translational repression and eIF4A2 activity are critical for microRNA-mediated gene regulation. Science 2013; 340:82-5. [PMID: 23559250 DOI: 10.1126/science.1231197] [Citation(s) in RCA: 261] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
MicroRNAs (miRNAs) control gene expression through both translational repression and degradation of target messenger RNAs (mRNAs). However, the interplay between these processes and the precise molecular mechanisms involved remain unclear. Here, we show that translational inhibition is the primary event required for mRNA degradation. Translational inhibition depends on miRNAs impairing the function of the eIF4F initiation complex. We define the RNA helicase eIF4A2 as the key factor of eIF4F through which miRNAs function. We uncover a correlation between the presence of miRNA target sites in the 3' untranslated region (3'UTR) of mRNAs and secondary structure in the 5'UTR and show that mRNAs with unstructured 5'UTRs are refractory to miRNA repression. These data support a linear model for miRNA-mediated gene regulation in which translational repression via eIF4A2 is required first, followed by mRNA destabilization.
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Affiliation(s)
- H A Meijer
- Medical Research Council Toxicology Unit, Hodgkin Building, Lancaster Road, Leicester LE1 9HN, UK
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9
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Ferland-McCollough D, Fernandez-Twinn DS, Cannell IG, David H, Warner M, Vaag AA, Bork-Jensen J, Brøns C, Gant TW, Willis AE, Siddle K, Bushell M, Ozanne SE. Programming of adipose tissue miR-483-3p and GDF-3 expression by maternal diet in type 2 diabetes. Cell Death Differ 2012; 19:1003-12. [PMID: 22223106 PMCID: PMC3354052 DOI: 10.1038/cdd.2011.183] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Revised: 11/01/2011] [Accepted: 11/02/2011] [Indexed: 02/06/2023] Open
Abstract
Nutrition during early mammalian development permanently influences health of the adult, including increasing the risk of type 2 diabetes and coronary heart disease. However, the molecular mechanisms underlying such programming are poorly defined. Here we demonstrate that programmed changes in miRNA expression link early-life nutrition to long-term health. Specifically, we show that miR-483-3p is upregulated in adipose tissue from low-birth-weight adult humans and prediabetic adult rats exposed to suboptimal nutrition in early life. We demonstrate that manipulation of miR-483-3p levels in vitro substantially modulates the capacity of adipocytes to differentiate and store lipids. We show that some of these effects are mediated by translational repression of growth/differentiation factor-3, a target of miR-483-3p. We propose that increased miR-483-3p expression in vivo, programmed by early-life nutrition, limits storage of lipids in adipose tissue, causing lipotoxicity and insulin resistance and thus increasing susceptibility to metabolic disease.
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Affiliation(s)
| | - D S Fernandez-Twinn
- University of Cambridge Metabolic Research Laboratories and Department of Clinical Biochemistry, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge CB2 0QQ, UK
| | - I G Cannell
- Koch Institute for Integrative Cancer Research, Massachussets Institue of Technology, Cambridge, MA, USA
| | - H David
- Koch Institute for Integrative Cancer Research, Massachussets Institue of Technology, Cambridge, MA, USA
| | - M Warner
- University of Cambridge Metabolic Research Laboratories and Department of Clinical Biochemistry, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge CB2 0QQ, UK
| | - A A Vaag
- Steno Diabetes Centre, Niels Steensens Vej 2, DK-2820 Gentofte, Denmark
| | - J Bork-Jensen
- Steno Diabetes Centre, Niels Steensens Vej 2, DK-2820 Gentofte, Denmark
| | - C Brøns
- Steno Diabetes Centre, Niels Steensens Vej 2, DK-2820 Gentofte, Denmark
| | - T W Gant
- MRC Toxicology Unit, Lancaster Road, Leicester LE1 9HN, UK
| | - A E Willis
- MRC Toxicology Unit, Lancaster Road, Leicester LE1 9HN, UK
| | - K Siddle
- University of Cambridge Metabolic Research Laboratories and Department of Clinical Biochemistry, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge CB2 0QQ, UK
| | - M Bushell
- MRC Toxicology Unit, Lancaster Road, Leicester LE1 9HN, UK
| | - S E Ozanne
- University of Cambridge Metabolic Research Laboratories and Department of Clinical Biochemistry, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge CB2 0QQ, UK
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Bushell M. MicroRNAs in the cytotoxic response. Toxicol Lett 2011. [DOI: 10.1016/j.toxlet.2011.05.124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Cobbold LC, Wilson LA, Sawicka K, King HA, Kondrashov AV, Spriggs KA, Bushell M, Willis AE. Upregulated c-myc expression in multiple myeloma by internal ribosome entry results from increased interactions with and expression of PTB-1 and YB-1. Oncogene 2010; 29:2884-91. [PMID: 20190818 DOI: 10.1038/onc.2010.31] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The 5' untranslated region of the proto-oncogene c-myc contains an internal ribosome entry segment (IRES) and c-myc translation can therefore be initiated by internal ribosome entry as well as by cap-dependent mechanisms. It has been shown previously that in patients with multiple myeloma (MM) and in MM-derived cell lines there is a C to T mutation in the c-myc IRES that increases IRES activity and the corresponding synthesis of c-myc protein although it is not fully understood how this occurs. Our data show that two recently identified c-myc IRES trans-acting factors, Y-box binding protein 1 (YB-1) and polypyrimidine tract-binding protein 1 (PTB-1), bind more strongly (approximately 3.5- and 2-fold respectively) to the mutated version of the c-myc IRES and in vitro these proteins exert their effect synergistically to stimulate IRES activity of the mutant IRES 4.5-fold more than the wild-type version. Importantly, we show that there is a strong correlation between the expression of PTB-1, YB-1 and c-myc in MM-derived cell lines, suggesting that by reducing either PTB-1 or YB-1 protein levels it is possible to decrease c-myc expression and inhibit cell proliferation of MM-derived cell lines.
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Affiliation(s)
- L C Cobbold
- Centre for Biomolecular Sciences, School of Pharmacy, University of Nottingham, Nottingham, UK
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12
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Grabowska A, Berry C, Bushell M, Willis A, Watson S. 60 POSTER Expression of a gastrin transcript in gastrointestinal cancer cells which allows maintenance of expression in hypoxia. EJC Suppl 2008. [DOI: 10.1016/s1359-6349(08)71992-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
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13
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Dobbyn HC, Hill K, Hamilton TL, Spriggs KA, Pickering BM, Coldwell MJ, de Moor CH, Bushell M, Willis AE. Regulation of BAG-1 IRES-mediated translation following chemotoxic stress. Oncogene 2007; 27:1167-74. [PMID: 17700523 PMCID: PMC2570717 DOI: 10.1038/sj.onc.1210723] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
There are three major isoforms of BAG-1 in mammalian cells, termed BAG-1L (p50), BAG-1M (p46) and BAG-1S (p36) that function as pro-survival proteins and are associated with tumorigenesis and chemoresistance. Initiation of BAG-1 protein synthesis can occur by both cap-dependent and cap-independent mechanisms and it has been shown that synthesis of BAG-1S is dependent upon the presence of an internal ribosome entry segment (IRES) in the 5'-UTR of BAG-1 mRNA. We have shown previously that BAG-1 IRES-meditated initiation of translation requires two trans-acting factors poly (rC) binding protein 1 (PCBP1) and polypyrimidine tract binding protein (PTB) for function. The former protein allows BAG-1 IRES RNA to attain a structure that permits binding of the ribosome, while the latter protein appears to be involved in ribosome recruitment. Here, we show that the BAG-1 IRES maintains synthesis of BAG-1 protein following exposure of cells to the chemotoxic drug vincristine but not to cisplatin and that this is brought about, in part, by the relocalization of PTB and PCBP1 from the nucleus to the cytoplasm.
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Affiliation(s)
- H C Dobbyn
- School of Pharmacy, University of Nottingham, Nottingham, UK
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14
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Abstract
Upon cell-cycle arrest or nutrient deprivation, the cellular rate of ribosome production is reduced significantly. In mammalian cells, this effect is achieved in part through a co-ordinated inhibition of RP (ribosomal protein) synthesis. More specifically, translation initiation on RP mRNAs is inhibited. Translational regulation of RP synthesis is dependent on cis-elements within the 5'-UTRs (5'-untranslated regions) of the RP mRNAs. In particular, a highly conserved 5'-TOP (5'-terminal oligopyrimidine tract) appears to play a key role in the regulation of RP mRNA translation. This article explores recent developments in our understanding of the mechanism of TOP mRNA regulation, focusing on upstream signalling pathways and trans-acting factors, and highlighting some interesting observations which have come to light following the recent development of cDNA microarray technology coupled with polysome analysis.
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Affiliation(s)
- T L Hamilton
- School of Pharmacy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
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15
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Spriggs KA, Bushell M, Mitchell SA, Willis AE. Internal ribosome entry segment-mediated translation during apoptosis: the role of IRES-trans-acting factors. Cell Death Differ 2005; 12:585-91. [PMID: 15900315 DOI: 10.1038/sj.cdd.4401642] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
During apoptosis, there is a reduction in translation initiation caused by caspase cleavage of several of the factors required for the cap-dependent scanning mechanism. Under these circumstances, many proteins that are required for apoptosis are instead translated by the alternative method of internal ribosome entry. This mechanism requires the formation of a complex RNA structural element and in the presence of internal ribosome entry segment (IRES)-trans-acting factors (ITAFs), the ribosome is recruited to the RNA. The interactions of several ITAFs with IRESs have been investigated in detail, and several mechanisms of action have been noted, including acting as chaperones, stabilising and remodelling the RNA structure. Structural remodelling by PTB in particular will be discussed, and how this protein is able to facilitate recruitment of the ribosome to several IRESs by causing previously occluded sites to become more accessible.
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Affiliation(s)
- K A Spriggs
- School of Pharmacy, University of Nottingham, University Park, Nottingham, UK
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16
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Abstract
The induction of apoptosis leads to a substantial inhibition of protein synthesis. During this process changes to the translation-initiation factors, the ribosome and the cellular level of mRNA have been documented. However, it is by no means clear which of these events are necessary to achieve translational shutdown. In this article, we discuss modifications to the translational apparatus that occur during apoptosis and examine the potential contributions that they make to the inhibition of protein synthesis. Moreover, we present evidence that suggests that a global increase in the rate of mRNA degradation occurs before the caspase-dependent cleavage of initiation factors. Increased mRNA decay is temporally correlated with the shutdown of translation and therefore plays a major role in the inhibition of protein synthesis in apoptotic cells.
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Affiliation(s)
- M Bushell
- Department of Biochemistry, University of Leicester, University Rd, Leicester LE1 7RH, UK.
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17
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Bushell M, Wood W, Carpenter G, Pain VM, Morley SJ, Clemens MJ. Disruption of the interaction of mammalian protein synthesis eukaryotic initiation factor 4B with the poly(A)-binding protein by caspase- and viral protease-mediated cleavages. J Biol Chem 2001; 276:23922-8. [PMID: 11274152 DOI: 10.1074/jbc.m100384200] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Eukaryotic initiation factor (eIF) 4B interacts with several components of the initiation pathway and is targeted for cleavage during apoptosis. In a cell-free system, cleavage of eIF4B by caspase-3 coincides with a general inhibition of protein synthetic activity. Affinity chromatography demonstrates that mammalian eIF4B interacts with the poly(A)-binding protein and that a region consisting of the N-terminal 80 amino acids of eIF4B is both necessary and sufficient for such binding. This interaction is lost when eIF4B is cleaved by caspase-3, which removes the N-terminal 45 amino acids. Similarly, the association of eIF4B with the poly(A)-binding protein in vivo is reduced when cells are induced to undergo apoptosis. Cleavage of the poly(A)-binding protein itself, using human rhinovirus 3C protease, also eliminates the interaction with eIF4B. Thus, disruption of the association between mammalian eIF4B and the poly(A)-binding protein can occur during both apoptosis and picornaviral infection and is likely to contribute to the inhibition of translation observed under these conditions.
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Affiliation(s)
- M Bushell
- Department of Biochemistry and Immunology, Cellular and Molecular Sciences Group, St. George's Hospital Medical School, Cranmer Terrace, London SW17 0RE, United Kingdom
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Morley SJ, Jeffrey I, Bushell M, Pain VM, Clemens MJ. Differential requirements for caspase-8 activity in the mechanism of phosphorylation of eIF2alpha, cleavage of eIF4GI and signaling events associated with the inhibition of protein synthesis in apoptotic Jurkat T cells. FEBS Lett 2000; 477:229-36. [PMID: 10908726 DOI: 10.1016/s0014-5793(00)01805-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Previously we have reported that induction of apoptosis in Jurkat cells results in an inhibition of overall protein synthesis with the selective and rapid cleavage of eukaryotic initiation factor (eIF) 4GI. For the cleavage of eIF4GI, caspase-3 activity is both necessary and sufficient in vivo, in a process which does not require signaling through the p38 MAP kinase pathway. We now show that activation of the Fas/CD95 receptor promotes an early, transient increase in the level of eIF2alpha phosphorylation, which is temporally correlated with the onset of the inhibition of translation. This is associated with a modest increase in the autophosphorylation of the protein kinase activated by double-stranded RNA. Using a Jurkat cell line that is deficient in caspase-8 and resistant to anti-Fas-induced apoptosis, we show that whilst the cleavage of eIF4GI is caspase-8-dependent, the enhancement of eIF2alpha phosphorylation does not require caspase-8 activity and occurs prior to the cleavage of eIF4GI. In addition, activation of the Fas/CD95 receptor results in the caspase-8-dependent dephosphorylation and degradation of p70(S6K), the enhanced binding of 4E-BP1 to eIF4E, and, at later times, the cleavage of eIF2alpha. These data suggest that apoptosis impinges upon the activity of several polypeptides which are central to the regulation of protein synthesis and that multiple signaling pathways are involved in vivo.
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Affiliation(s)
- S J Morley
- Biochemistry Laboratory, School of Biological Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK.
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Clemens MJ, Bushell M, Jeffrey IW, Pain VM, Morley SJ. Translation initiation factor modifications and the regulation of protein synthesis in apoptotic cells. Cell Death Differ 2000; 7:603-15. [PMID: 10889505 DOI: 10.1038/sj.cdd.4400695] [Citation(s) in RCA: 182] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
The rate of protein synthesis is rapidly down-regulated in mammalian cells following the induction of apoptosis. Inhibition occurs at the level of polypeptide chain initiation and is accompanied by the phosphorylation of the alpha subunit of initiation factor eIF2 and the caspase-dependent cleavage of initiation factors eIF4G, eIF4B, eIF2alpha and the p35 subunit of eIF3. Proteolytic cleavage of these proteins yields characteristic products which may exert regulatory effects on the translational machinery. Inhibition of caspase activity protects protein synthesis from long-term inhibition in cells treated with some, but not all, inducers of apoptosis. This review describes the initiation factor modifications and the possible signalling pathways by which translation may be regulated during apoptosis. We discuss the significance of the initiation factor cleavages and other changes for protein synthesis, and the implications of these events for our understanding of the cellular changes associated with apoptosis.
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Affiliation(s)
- M J Clemens
- Department of Biochemistry and Immunology, Cellular and Molecular Sciences Group, St George's Hospital Medical School, Cranmer Terrace, London SW17 ORE, UK.
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Bushell M, Poncet D, Marissen WE, Flotow H, Lloyd RE, Clemens MJ, Morley SJ. Cleavage of polypeptide chain initiation factor eIF4GI during apoptosis in lymphoma cells: characterisation of an internal fragment generated by caspase-3-mediated cleavage. Cell Death Differ 2000; 7:628-36. [PMID: 10889507 DOI: 10.1038/sj.cdd.4400699] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Polypeptide chain initiation factor eIF4GI undergoes caspase-mediated degradation during apoptosis to give characteristic fragments. The most prominent of these has an estimated mass of approximately 76 kDa (Middle-Fragment of Apoptotic cleavage of eIF4G; M-FAG). Subcellular fractionation of the BJAB lymphoma cell line after induction of apoptosis indicates that M-FAG occurs in both ribosome-bound and soluble forms. Affinity chromatography on m7GTP-Sepharose shows that M-FAG retains the ability of eIF4GI to associate with both the mRNA cap-binding protein eIF4E and initiation factor eIF4A and that the ribosome-bound form of M-FAG is also present as a complex with eIF4E and eIF4A. These data suggest that the binding sites for eIF4E, eIF4A and eIF3 on eIF4GI are retained in the caspase-generated fragment. M-FAG is also a substrate for cleavage by the Foot-and-Mouth-Disease Virus-encoded L protease. These properties, together with the pattern of recognition by a panel of antibodies, define the origin of the apoptotic cleavage fragment. N-terminal sequencing of the products of caspase-3-mediated eIF4GI cleavage has identified the major cleavage sites. The pattern of eIF4GI degradation and the possible roles of the individual cleavage products in cells undergoing apoptosis are discussed.
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Affiliation(s)
- M Bushell
- Department of Biochemistry and Immunology, Cellular and Molecular Sciences Group, St George's Hospital Medical School, Cranmer Terrace, London SW17 ORE, UK
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Bushell M, Wood W, Clemens MJ, Morley SJ. Changes in integrity and association of eukaryotic protein synthesis initiation factors during apoptosis. Eur J Biochem 2000; 267:1083-91. [PMID: 10672017 DOI: 10.1046/j.1432-1327.2000.01101.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Induction of apoptosis results in inhibition of the rate of overall protein synthesis in a variety of cell types. We have shown previously that polypeptide chain initiation factor eIF4GI is rapidly cleaved by caspase-3, whereas other components of the eIF4F complex are much more stable during apoptosis in BJAB and Jurkat cells. We have now extended our analysis to other factors involved in the initiation of protein synthesis and we report here that eIF4B, the p35 subunit of eIF3, and minor proportions of the alpha subunit of eIF2 and the eIF4E-binding protein 4E-BP1 are also cleaved to give rise to discrete fragments. These cleavages occur with delayed kinetics relative to that seen for eIF4GI, and eIF2beta and eIF2gamma levels also decrease at a relatively late stage of apoptosis. In contrast, the second form of eIF4G described recently, eIF4GII, is cleaved as rapidly as eIF4GI under the same conditions. Purified recombinant caspase-3 is able to degrade eIF4B and eIF3(p35) in vitro, producing fragments of the same sizes as those seen in intact cells. Induction of apoptosis also results in a biphasic change in the association of 4E-BP1 with eIF4E. Thus the progress of apoptosis is characterized by a complex programme of changes in several initiation factors, including the specific fragmentation or complete degradation of some and alterations in the association status of others. These events are likely to contribute to the inhibition of protein synthesis seen under these conditions.
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Affiliation(s)
- M Bushell
- Biochemistry Group, School of Biological Sciences, University of Sussex, Brighton, UK
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Bushell M, McKendrick L, Jänicke RU, Clemens MJ, Morley SJ. Caspase-3 is necessary and sufficient for cleavage of protein synthesis eukaryotic initiation factor 4G during apoptosis. FEBS Lett 1999; 451:332-6. [PMID: 10371215 DOI: 10.1016/s0014-5793(99)00614-6] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Induction of apoptosis BJAB cells is accompanied by the rapid cleavage of protein synthesis eukaryotic initiation factor 4G and the appearance of a fragment of approximately 76 kDa. Inhibition of apoptotic proteases (caspases) has previously been shown to prevent the cleavage of eukaryotic initiation factor 4G. In MCF-7 breast carcinoma cells, which are deficient in caspase-3, eukaryotic initiation factor 4G is not cleaved but in vivo expression of caspase-3 restores eukaryotic initiation factor 4G cleavage following induction of apoptosis. Recombinant caspase-3 can also cleave eukaryotic initiation factor 4G to yield the 76 kDa fragment both in cell extracts and when the eukaryotic initiation factor 4G is presented in a purified eukaryotic initiation factor 4F complex. These results indicate that caspase-3 activity is necessary and sufficient for eukaryotic initiation factor 4G degradation.
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Affiliation(s)
- M Bushell
- Biochemistry Group, School of Biological Sciences, University of Sussex, Brighton, UK
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Clemens MJ, Bushell M, Morley SJ. Degradation of eukaryotic polypeptide chain initiation factor (eIF) 4G in response to induction of apoptosis in human lymphoma cell lines. Oncogene 1998; 17:2921-31. [PMID: 9879998 DOI: 10.1038/sj.onc.1202227] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We have investigated the effect of inducing apoptosis in BJAB and Jurkat cells on the cellular content of several polypeptide chain initiation factors. Serum deprivation results in inhibition of protein synthesis and induction of apoptosis in BJAB cells; at early times, there is selective degradation of polypeptide initiation factor eIF4G but no major losses of other key initiation factors. The disappearance of full length eIF4G is accompanied by the appearance of smaller forms of the protein, including a major product of approximately 76 kDa. Apoptosis induced by cycloheximide results in similar effects. Both total cytoplasmic eIF4G and eIF4G associated with eIF4E are degraded with a half-life of 2-4 h under these conditions. Treatment of serum-starved or cycloheximide-treated cells with Z-VAD.FMK or Z-DEVD.FMK, which inhibit caspases required for apoptosis, protects eIF4G from degradation and blocks the appearance of the ca. 76 kDa product. Exposure of BJAB cells to rapamycin rapidly inhibits protein synthesis but does not lead to acute degradation of eIF4G. In both BJAB and Jurkat cells induction of apoptosis with anti-Fas antibody or etoposide also results in the selective loss of eIF4G, which is inhibitable by Z-VAD.FMK. These data suggest that eIF4G is selectively targeted for cleavage as cells undergo apoptosis and is a substrate for proteases activated during this process.
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Affiliation(s)
- M J Clemens
- Department of Biochemistry, Cellular and Molecular Sciences Group, St George's Hospital Medical School, London, UK
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Morley SJ, McKendrick L, Bushell M. Cleavage of translation initiation factor 4G (eIF4G) during anti-Fas IgM-induced apoptosis does not require signalling through the p38 mitogen-activated protein (MAP) kinase. FEBS Lett 1998; 438:41-8. [PMID: 9821956 DOI: 10.1016/s0014-5793(98)01269-1] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Initiation factor (eIF) 4G plays a key role in the regulation of translation, acting as a bridge between eIF4E and eIF3, to allow an mRNA molecule to associate with the 40S ribosomal subunit. In this study, we show that activation of the Fas/CD95 receptor complex in Jurkat cells induces the degradation of eIF4G, the inhibition of total protein synthesis and cell death. These responses were prevented by the caspase inhibitors, zVAD.FMK and zDEVD.FMK. We also show that, in contrast to Saccharomyces cerevisiae, although rapamycin caused a modest inhibition of protein synthesis it did not induce apoptosis or the cleavage of eIF4G. Studies with the specific inhibitor, SB203580, have shown that signalling through the p38 MAP kinase pathway is not required for either the Fas/CD95-induced cleavage of eIF4G or cell death. These data suggest that the cleavage of eIF4G and the inhibition of translation play an integral role in Fas/CD95-induced cell death in Jurkat cells.
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Affiliation(s)
- S J Morley
- Biochemistry Laboratory, School of Biological Sciences, University of Sussex, Falmer, Brighton, UK.
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Abstract
The effects of cholecystokinin octapeptide (CCK-OP) on the gall-bladder (GB) and sphincter of Oddi (SO) of the Australian brush tailed possum were examined in 45 anaesthetized animals. CCK-OP (20-640 ng/kg) consistently caused the GB to contract in a dose-dependent manner (Kruskal Wallis P less than 0.05). In 20 animals, the same dose range of CCK-OP produced an excitatory response in the SO, increasing the SO motility index (MI = frequency of contractions x mean peak amplitude) dose-dependently (Kruskal Wallis P less than 0.05). In five animals, an inhibitory response, that is, a decrease in MI, was recorded, with 640 ng/kg of CCK-OP producing a 50% decrease in MI. In the remaining 20 animals, variable responses of both excitation and inhibition were elicited within the same animal. The action of CCK-OP on the SO and GB was not modified by atropine, phentolamine or propranolol. Tetrodotoxin (TTX) reversed the inhibitory responses of the SO to CCK-OP such that responses were excitatory (sign test P less than 0.05). TTX did not alter the response of the GB to CCK-OP. It is concluded that CCK-OP acts directly on smooth muscle receptors of the GB. In the SO, its action is mediated via non-cholinergic, non-noradrenergic inhibitory neurons and also by a direct excitatory action on the smooth muscle of the SO.
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Affiliation(s)
- J Iannos
- Department of Surgery, Flinders Medical Centre, Bedford Park, South Australia
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Abstract
Prolonged postoperative peritoneal lavage has been used as a part of the management of 55 patients with diffuse peritonitis. The lavage technique consisted of 60 min cycles of instillation and drainage of a lavage fluid into the peritoneal cavity via a peritoneal dialysis catheter. The lavage fluid was a slightly hypertonic salt solution containing antibiotics, usually cefotaxime and metronidazole. The overall mortality rate in the series was 11% (6/55). Only one of these patients had residual abdominal sepsis present at post-mortem, the remaining deaths being due to a progression of the pre-existing disease. Five patients showed evidence of further intra-abdominal sepsis. In three of these patients this was associated with the presence of a previously well established abscess cavity. The overall results indicate that, for this group of patients recognized to be at high risk of mortality or further sepsis, the use of prolonged postoperative peritoneal lavage is associated with an improved outcome.
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Toouli J, Bushell M, Iannos J, Collinson T, Wearne J, Kitchen D. Peroperative sphincter of Oddi manometry: motility disorder in patients with cholelithiasis. Aust N Z J Surg 1986; 56:625-9. [PMID: 3463290 DOI: 10.1111/j.1445-2197.1986.tb04517.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Intraluminal pressure recordings from the sphincter of Oddi (SO) have made significant contributions towards the understanding of normal SO function and are being used for the diagnosis of SO motility abnormalities. In this study the endoscopic intraluminal methods for measuring SO pressure changes have been adapted for use under sterile conditions during surgery on the biliary system. Sphincter of Oddi pressure measurement in a group of patients undergoing elective cholecystectomy for gallstones, were compared with a group of control subjects undergoing endoscopic study of the SO. There was no significant difference in CBD pressure. SO basal pressure, SO wave amplitude and SO wave frequency. However, a highly significant difference was noted in the propagation direction of the SO contractions. The control subjects had a predominance of antegrade contractions whereas patients undergoing cholecystectomy had a predominance of retrograde contractions. This result suggests an association between SO motility disorder and the presence of gallstones.
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Toouli J, Bushell M, Stevenson G, Dent J, Wycherley A, Iannos J. Gallbladder emptying in man related to fasting duodenal migrating motor contractions. Aust N Z J Surg 1986; 56:147-51. [PMID: 3524524 DOI: 10.1111/j.1445-2197.1986.tb01872.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Animal studies have shown that the gallbladder (GB) empties partially during fasting in relation to phase II of the interdigestive motor cycle (IDMC). It has been assumed that in man the GB remains inert during fasting, although there have been no studies in which repeated sequential measurements of gallbladder volume have been made and related to the IDMC. In this study the possibility of linkage between the IDMC and GB volume has been examined in nine fasting human volunteers (five males/four females). A multilumen constantly perfused manometry catheter was positioned in the duodenum and motor activity recorded continuously. Phase III of the IDMC was characterized by phasic contractions, with a frequency of 10-12/min for at least 2 min, which had a distal propagative pattern and were followed by a motor quiescence (Phase I). GB volume was calculated at 15 min intervals from ultrasound measurements of the maximal length and diameter of the GB by the summation of cylinders method, and related to the time of onset of each phase III of the IDMC. In all nine subjects GB volume decreased prior to the onset of phase III and increased following its passage (P less than 0.01). GB volume decrease ranged between 6 and 56% of maximal GB volume (median 18%) and subsequent filling ranged from 14 to 53% (median 27%). The maximal volume decrease occurred 30 min prior to the onset of phase III (P less than 0.02). These studies have demonstrated that the human GB empties partially during phase II of the IDMC.(ABSTRACT TRUNCATED AT 250 WORDS)
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Bushell M, O'Brien P. Acid-base imbalance and ulceration in the cold restrained rat. Surgery 1982; 91:318-21. [PMID: 7058514] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Using the cold restrained rat model of stress ulceration, we have examined the influence of metabolic acidosis, metabolic alkalosis, and respiratory acidosis on the development of gastric erosions. The rats were restrained in tightly fitting perspex chambers at 6 degrees C for 3 hours. Acid-base imbalance was achieved by infusion of NH4Cl or NaHCO3 or by exposure to 5% CO2. The degree of ulceration was expressed by a lesion score of 0 to 4. The control group showed a score of 2.5 +/- 0.2 (mean +/- SEM). With metabolic acidosis the score was 3.6 +/- 0.2, and with metabolic alkalosis the score was 0.9 +/- 0.4. Both values were significantly different from control values (P less than 0.005). Respiratory acidosis was associated with a score similar to that of the control group. The values obtained appeared to be independent of gastric luminal acidity. The findings indicate that the systemic HCO-3 concentration is a significant determinant of the degree of ulceration in the cold restrained rat.
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O'Brien P, Bushell M. Role of acid-base status in the response of the isolated amphibian gastric mucosa to back diffusion of H+. Gastroenterology 1980; 79:439-46. [PMID: 6776001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
The effect of a period of induced back diffusion of H+ on the isolated amphibian gastric mucosa was studied under various conditions. Under standard conditions (HCO3--buffered nutrient solution; 95% O2-5% CO2), passage of an electrical current of 500 microA/cm2 for 15 min from a secretory fluid of pH 2.10 across the mucosal resulted in a decrease of the transmucosal potential difference (PD) of 10.9 +/- 1.9 mV, a decrease of resistance (R) of 48 +/- 26 ogema cm2 and a decrease of short circuit current (Isc) of 18 +/- 7 microA/cm2. Flux of the neutral molecule, erythritol from secretory (S) to nutrient (N) fluid increased by 66% and the active transport of Cl- N lead to S decreased from 2.9 to 1.9 microeq/cm2/hr. With removal of HCO3- from the nutrient fluid and with inhibition of carbonic anhydrase activity the period of back diffusion induced significantly greater change in the electrical measurements than occurred when under standard conditions. This increased effect of back diffusion of H+ was not changed by change of the nutrient fluid pH from 7.20 to either 6.6 or 8.2. Increase of the HCO3- concentration of the nutrient fluid to 35 mM or decrease of the CO2 content of the aerating gas to 1% were associated with significantly less change of the electrical measurements than occurred with standard conditions. These studies support the proposal that the the neutralizing reaction HCO3- + H+ leads to CO2 + H2O plays a central role in the gastric mucosal handling of backing diffusing H+ and suggests that the capacity and poise of the HCO3-/CO2 buffer system is an important determinant of the ability of the mucosa to tolerate luminal acidity.
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