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He P, Tian N. Curcumin modulates the apolipoprotein B mRNA editing by coordinating the expression of cytidine deamination to uridine editosome components in primary mouse hepatocytes. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY 2019; 23:181-189. [PMID: 31080349 PMCID: PMC6488708 DOI: 10.4196/kjpp.2019.23.3.181] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/23/2018] [Revised: 08/14/2018] [Accepted: 09/12/2018] [Indexed: 11/15/2022]
Abstract
Curcumin, an active ingredient of Curcuma longa L., can reduce the concentration of low-density lipoproteins in plasma, in different ways. We had first reported that curcumin exhibits hypocholesterolemic properties by improving the apolipoprotein B (apoB) mRNA editing in primary rat hepatocytes. However, the role of curcumin in the regulation of apoB mRNA editing is not clear. Thus, we investigated the effect of curcumin on the expression of multiple editing components of apoB mRNA cytidine deamination to uridine (C-to-U) editosome. Our results demonstrated that treatment with 50 µM curcumin markedly increased the amount of edited apoB mRNA in primary mouse hepatocytes from 5.13%–8.05% to 27.63%–35.61%, and significantly elevated the levels of the core components apoB editing catalytic polypeptide-1 (APOBEC-1), apobec-1 complementation factor (ACF), and RNA-binding-motif-protein-47 (RBM47), as well as suppressed the level of the inhibitory component glycine-arginine-tyrosine-rich RNA binding protein. Moreover, the increased apoB RNA editing by 50 µM curcumin was significantly reduced by siRNA-mediated APOBEC-1, ACF, and RBM47 knockdown. These findings suggest that curcumin modulates apoB mRNA editing by coordinating the multiple editing components of the editosome in primary hepatocytes. Our data provided evidence for curcumin to be used therapeutically to prevent atherosclerosis.
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Affiliation(s)
- Pan He
- Institute of Molecular Medicine, Life Science College, Zhejiang Chinese Medical University, Hangzhou 310053, Zhejiang, China
| | - Nan Tian
- Institute of Molecular Medicine, Life Science College, Zhejiang Chinese Medical University, Hangzhou 310053, Zhejiang, China
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Chen Z, Eggerman TL, Patterson AP. ApoB mRNA editing is mediated by a coordinated modulation of multiple apoB mRNA editing enzyme components. Am J Physiol Gastrointest Liver Physiol 2007; 292:G53-65. [PMID: 16920700 DOI: 10.1152/ajpgi.00118.2006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Apolipoprotein (apo)B mRNA editing is accomplished by a large multiprotein complex. How these proteins interact to achieve the precise single-nucleotide change induced by this complex remains unclear. We investigated the relationship between altered apoB mRNA editing and changes in editing enzyme components to evaluate their roles in editing regulation. In the mouse fetal small intestine, we found that the dramatic developmental upregulation of apoB mRNA editing from approximately 3% to 88% begins with decreased levels of inhibitory CUG binding protein 2 (CUGBP2) expression followed by increased levels of apoB mRNA editing enzyme (apobec)-1 and apobec-1 complementation factor (ACF) (4- and 8-fold) and then by decreased levels of the inhibitory components glycine-arginine-tyrosine-rich RNA binding protein (GRY-RBP) and heterogeneous nuclear ribonucleoprotein (hnRNP)-C1 (75% and 56%). In contrast, the expression of KH-type splicing regulatory protein (KSRP), apobec-1 binding protein (ABBP)1, ABBP2, and Bcl-2-associated athanogene 4 (BAG4) were unaltered. In the human intestinal cell line Caco-2, the increase of apoB mRNA editing from approximately 1.7% to approximately 23% was associated with 6- and 3.2-fold increases of apobec-1 and CUGBP2, respectively. In the mouse large intestine, the editing was 48% and had a 2.7-fold relatively greater CUGBP2 level. Caco-2 and the large intestine thus have increased instead of decreased CUGBP2 and a lower level of editing, suggesting that inhibitory CUGBP2 may play a critical role in the magnitude of editing regulation. Short interfering RNA-mediated gene-specific knockdown of CUGBP2, GRY-RBP, and hnRNP-C1 resulted in increased editing in Caco-2 cells, consistent with their known inhibitory function. These data suggest that a coordinated expression of editing components determines the magnitude and specificity of apoB mRNA editing.
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Affiliation(s)
- Zhigang Chen
- Office of Biotechnology Activities, National Institutes of Health, 6705 Rockledge Dr., Suite 750, Bethesda, MD 20892, USA
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Lehmann DM, Galloway CA, MacElrevey C, Sowden MP, Wedekind JE, Smith HC. Functional characterization of APOBEC-1 complementation factor phosphorylation sites. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1773:408-18. [PMID: 17229474 PMCID: PMC1847399 DOI: 10.1016/j.bbamcr.2006.11.019] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2006] [Revised: 11/13/2006] [Accepted: 11/27/2006] [Indexed: 11/17/2022]
Abstract
ApoB mRNA editing involves site-specific deamination of cytidine 6666 producing an in-frame translation stop codon. Editing minimally requires APOBEC-1 and APOBEC-1 complementation factor (ACF). Metabolic stimulation of apoB mRNA editing in hepatocytes is associated with serine phosphorylation of ACF localized to editing competent, nuclear 27S editosomes. We demonstrate that activation of protein kinase C (PKC) stimulated editing and enhanced ACF phosphorylation in rat primary hepatocytes. Conversely, activation of protein kinase A (PKA) had no effect on editing. Recombinant PKC efficiently phosphorylated purified ACF64 protein in vitro, whereas PKA did not. Mutagenesis of predicted PKC phosphorylation sites S154 and S368 to alanine inhibited ethanol-stimulated induction of editing suggesting that these sites function in the metabolic regulation of editing. Consistent with this interpretation, substitution of S154 and S368 with aspartic acid stimulated editing to levels comparable to ethanol treatment in control McArdle RH7777 cells. These data suggest that phosphorylation of ACF by PKC may be a key regulatory mechanism of apoB mRNA editing in rat hepatocytes.
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Affiliation(s)
- David M. Lehmann
- Department of Toxicology, University of Rochester, Rochester, New York 14642
- Environmental Health Sciences Center, University of Rochester, Rochester, New York 14642
| | - Chad A. Galloway
- Department of Biochemistry and Biophysics, University of Rochester, Rochester, New York 14642
| | - Celeste MacElrevey
- Department of Biochemistry and Biophysics, University of Rochester, Rochester, New York 14642
| | - Mark P. Sowden
- Department of Biochemistry and Biophysics, University of Rochester, Rochester, New York 14642
- Department of Pathology and Laboratory Medicine, University of Rochester, Rochester, New York 14642
| | - Joseph E. Wedekind
- Department of Biochemistry and Biophysics, University of Rochester, Rochester, New York 14642
| | - Harold C. Smith
- Department of Biochemistry and Biophysics, University of Rochester, Rochester, New York 14642
- Department of Pathology and Laboratory Medicine, University of Rochester, Rochester, New York 14642
- Department of Toxicology, University of Rochester, Rochester, New York 14642
- Environmental Health Sciences Center, University of Rochester, Rochester, New York 14642
- James P. Wilmot Cancer Center, University of Rochester, Rochester, New York 14642
- * Corresponding author: Department of Biochemistry and Biophysics, University of Rochester, 601 Elmwood Ave., Rochester, NY 14642 Tel.: 585-275-4267 FAX: 585-275-6007 E-mail:
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Lehmann DM, Galloway CA, Sowden MP, Smith HC. Metabolic regulation of apoB mRNA editing is associated with phosphorylation of APOBEC-1 complementation factor. Nucleic Acids Res 2006; 34:3299-308. [PMID: 16820530 PMCID: PMC1500872 DOI: 10.1093/nar/gkl417] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Apolipoprotein B (apoB) mRNA editing is a nuclear event that minimally requires the RNA substrate, APOBEC-1 and APOBEC-1 Complementation Factor (ACF). The co-localization of these macro-molecules within the nucleus and the modulation of hepatic apoB mRNA editing activity have been described following a variety of metabolic perturbations, but the mechanism that regulates editosome assembly is unknown. APOBEC-1 was effectively co-immunoprecipitated with ACF from nuclear, but not cytoplasmic extracts. Moreover, alkaline phosphatase treatment of nuclear extracts reduced the amount of APOBEC-1 co-immunoprecipitated with ACF and inhibited in vitro editing activity. Ethanol stimulated apoB mRNA editing was associated with a 2- to 3-fold increase in ACF phosphorylation relative to that in control primary hepatocytes. Significantly, phosphorylated ACF was restricted to nuclear extracts where it co-sedimented with 27S editing competent complexes. Two-dimensional phosphoamino acid analysis of ACF immunopurified from hepatocyte nuclear extracts demonstrated phosphorylation of serine residues that was increased by ethanol treatment. Inhibition of protein phosphatase I, but not PPIIA or IIB, stimulated apoB mRNA editing activity coincident with enhanced ACF phosphorylation in vivo. These data demonstrate that ACF is a metabolically regulated phosphoprotein and suggest that this post-translational modification increases hepatic apoB mRNA editing activity by enhancing ACF nuclear localization/retention, facilitating the interaction of ACF with APOBEC-1 and thereby increasing the probability of editosome assembly and activity.
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Affiliation(s)
- David M. Lehmann
- Department of Toxicology, University of RochesterRochester, NY 14642, USA
- The Environmental Health Sciences Center, University of RochesterRochester, NY 14642, USA
| | - Chad A. Galloway
- Department of Biochemistry and Biophysics, University of RochesterRochester, NY 14642, USA
| | - Mark P. Sowden
- Department of Biochemistry and Biophysics, University of RochesterRochester, NY 14642, USA
- Department of Pathology and Laboratory Medicine, University of RochesterRochester, NY 14642, USA
| | - Harold C. Smith
- Department of Biochemistry and Biophysics, University of RochesterRochester, NY 14642, USA
- Department of Pathology and Laboratory Medicine, University of RochesterRochester, NY 14642, USA
- Department of Toxicology, University of RochesterRochester, NY 14642, USA
- The Environmental Health Sciences Center, University of RochesterRochester, NY 14642, USA
- James P. Wilmot Cancer Center, University of RochesterRochester, NY 14642, USA
- To whom correspondence should be addressed. Tel: +1 585 275 4267; Fax: +1 585 275 6007;
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Sparks JD, Collins HL, Chirieac DV, Cianci J, Jokinen J, Sowden MP, Galloway CA, Sparks CE. Hepatic very-low-density lipoprotein and apolipoprotein B production are increased following in vivo induction of betaine-homocysteine S-methyltransferase. Biochem J 2006; 395:363-71. [PMID: 16396637 PMCID: PMC1422758 DOI: 10.1042/bj20051966] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
We have previously reported a positive correlation between the expression of BHMT (betaine-homocysteine S-methyltransferase) and ApoB (apolipoprotein B) in rat hepatoma McA (McArdle RH-7777) cells [Sowden, Collins, Smith, Garrow, Sparks and Sparks (1999) Biochem. J. 341, 639-645]. To examine whether a similar relationship occurs in vivo, hepatic BHMT expression was induced by feeding rats a Met (L-methionine)-restricted betaine-containing diet, and parameters of ApoB metabolism were evaluated. There were no generalized metabolic abnormalities associated with Met restriction for 7 days, as evidenced by control levels of serum glucose, ketones, alanine aminotransferase and L-homocysteine levels. Betaine plus the Met restriction resulted in lower serum insulin and non-esterified fatty acid levels. Betaine plus Met restriction induced hepatic BHMT 4-fold and ApoB mRNA 3-fold compared with Met restriction alone. No changes in percentage of edited ApoB mRNA were observed on the test diets. An increase in liver ApoB mRNA correlated with an 82% and 46% increase in ApoB and triacylglycerol production respectively using in vivo Triton WR 1339. Increased secretion of VLDL (very-low-density lipoprotein) with Met restriction plus betaine was associated with a 45% reduction in liver triacylglycerol compared with control. Nuclear run-off assays established that transcription of both bhmt and apob genes was also increased in Met-restricted plus betaine diets. No change in ApoB mRNA stability was detected in BHMT-transfected McA cells. Hepatic ApoB and BHMT mRNA levels were also increased by 1.8- and 3-fold respectively by betaine supplementation of Met-replete diets. Since dietary betaine increased ApoB mRNA, VLDL ApoB and triacylglycerol production and decreased hepatic triacylglycerol, results suggest that induction of apob transcription may provide a potential mechanism for mobilizing hepatic triacylglycerol by increasing ApoB available for VLDL assembly and secretion.
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Affiliation(s)
- Janet D Sparks
- Department of Pathology and Laboratory Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA.
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Sowden MP, Lehmann DM, Lin X, Smith CO, Smith HC. Identification of novel alternative splice variants of APOBEC-1 complementation factor with different capacities to support apolipoprotein B mRNA editing. J Biol Chem 2003; 279:197-206. [PMID: 14570923 DOI: 10.1074/jbc.m307920200] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Two novel mRNA transcripts have been identified that result from species- and tissue-specific, alternative polyadenylation and splicing of the pre-mRNA encoding the apolipoprotein B (apoB) editing catalytic subunit 1 (APOBEC-1) complementation factor (ACF) family of related proteins. The alternatively processed mRNAs encode 43- and 45-kDa proteins that are components of the previously identified p44 cluster of apoB RNA binding, editosomal proteins. Recombinant ACF45 displaced ACF64 and ACF43 in mooring sequence RNA binding but did not demonstrate strong binding to APOBEC-1. In contrast, ACF43 bound strongly to APOBEC-1 but demonstrated weak binding to mooring sequence RNA. Consequently ACF45/43 complemented APOBEC-1 in apoB mRNA editing with less efficiency than full-length ACF64. These data, together with the finding that all ACF variants were co-expressed in rat liver nuclei (the site of apoB mRNA editing), suggested that ACF variants might compete with one another for APOBEC-1 and apoB mRNA binding and thereby contribute to the regulation of apoB mRNA editing. In support for this hypothesis, the ratio of nuclear ACF65/64 to ACF45/43 decreased when hepatic editing was inhibited by fasting and increased when editing was re-stimulated by refeeding. These findings suggested a new model for the regulation of apoB mRNA editing in which the catalytic potential of editosomes is modulated at the level of their assembly by alterations in the relative abundance of multiple related RNA-binding auxiliary proteins and the expression level of APOBEC-1.
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Affiliation(s)
- Mark P Sowden
- Department of Biochemistry and Biophysics, University of Rochester, NY 14642, USA
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Abstract
Apolipoprotein B is a large, amphipathic protein that plays a central role in lipoprotein metabolism. Because its overproduction and deficiency leads to metabolic and pathologic disorders, much effort has been paid to investigate the mechanisms of how its homeostasis is achieved. Earlier and recent studies have showed that apoB gene locus might reside in different chromatin domains in the hepatic and intestinal cells, and two sets of very distinct regulatory elements operate to control its transcription. Posttranscriptional modification of apoB mRNA is performed by a multicomponent enzyme complex, several possible pathways regulate the editing efficiency. Understanding of the mechanism responsible for apoB mRNA editing will provide the basis for C-to-U editing in gene therapy. In addition to apoB mRNA abundance and stability, its translation can be also regulated at the steps of elongation. The translocation of apoB into the ER is an important and complicated process that is less understood. Successful transport and correct folding of apoB may lead to its final secretion, otherwise subject to intracellular degradation, which is accomplished by proteasomal and nonproteasomal pathways at multiple levels and may differ among cell types.
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Affiliation(s)
- Ai-Bing Wang
- National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Beijing 10005, People's Republic of China
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Haorah J, MacDonald RG, Stoner JA, Donohue TM. Ethanol consumption decreases the synthesis of the mannose 6-phosphate/insulin-like growth factor II receptor but does not decrease its messenger RNA. Biochem Pharmacol 2003; 65:637-48. [PMID: 12566093 DOI: 10.1016/s0006-2952(02)01605-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The mannose 6-phosphate/insulin-like growth factor II receptor (M6P/IGF-IIR) is a protein that facilitates the transport of acid hydrolases into the lysosome. We have shown that chronic ethanol consumption lowers the M6P/IGF-IIR content in rat hepatocytes. Here, we determined the steady-state level of mRNA encoding M6P/IGF-IIR, as well as the rate of receptor synthesis, to ascertain whether the ethanol-elicited reduction in receptor protein content is related to changes in either or both of these parameters. Rats were pair-fed the normal carbohydrate (NC) or low carbohydrate high-fat (LC) liquid diets containing either ethanol or isocaloric maltose-dextrin for 7-8 weeks. RNA was isolated from hepatocytes and from whole livers of these animals and subjected to reverse transcription-polymerase chain reaction (RT-PCR) to determine the mRNA levels encoding M6P/IGF-IIR. Hepatocytes isolated from these animals were also radiolabeled with Pro-mix L-[35S] in vitro cell labeling mix to measure incorporation into total cellular protein and the immunoprecipitated M6P/IGF-IIR protein. The steady-state levels of M6P/IGF-IIR mRNA in both hepatocytes and whole livers from ethanol-fed rats were the same as those from their respective controls regardless of whether they were fed the NC or the LC diets. Hepatocytes from ethanol-fed rats showed a 36% lower rate of total protein synthesis and an even greater reduction (70%) in receptor synthesis. When the relative rate of receptor synthesis was calculated, hepatocytes from ethanol-fed rats had a 53% lower relative rate of receptor synthesis compared with controls. Autoradiographic analysis of the immunoprecipitated receptor protein from ethanol-fed rats also indicated a 79% decline in the total M6P/IGF-IIR protein synthetic rate compared with pair-fed controls. We conclude that the ethanol-elicited reduction of M6P/IGF-IIR content was, in part, related to a concomitant reduction of receptor protein synthesis but not to a decline in its mRNA level. Thus, the ethanol-elicited decline in receptor protein synthesis may be due to defective M6P/IGF-IIR mRNA translation.
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Affiliation(s)
- James Haorah
- Liver Study Unit, Research Service (151), The Veterans Affairs (VA) Medical Center, 4101 Woolworth Avenue, Omaha, NE 68105, USA.
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Anant S, Blanc V, Davidson NO. Molecular regulation, evolutionary, and functional adaptations associated with C to U editing of mammalian apolipoproteinB mRNA. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 2003; 75:1-41. [PMID: 14604008 DOI: 10.1016/s0079-6603(03)75001-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
RNA editing encompasses an important class of co- or posttranscriptional nucleic acid modification that has expanded our understanding of the range of mechanisms that facilitate genetic plasticity. Since the initial description of RNA editing in trypanosome mitochondria, a model of gene regulation has emerged that now encompasses a diverse range of biochemical and genetic mechanisms by which nuclear, mitochondrial, and t-RNA sequences are modified from templated versions encoded in the genome. RNA editing is genetically and biochemically distinct from other RNA modifications such as splicing, capping, and polyadenylation although, as discussed in Section I, these modifications may have relevance to the regulation of certain types of mammalian RNA editing. This review will focus on C to U RNA editing, in particular, the biochemical and genetic mechanisms that regulate this process in mammals. These mechanisms will be examined in the context of the prototype model of C to U RNA editing, namely the posttranscriptional cytidine deamination targeting a single nucleotide in mammalian apolipoproteinB (apoB). Other examples of C to U RNA editing will be discussed and the molecular mechanisms--where known--contrasted with those regulating apoB RNA editing.
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Affiliation(s)
- Shrikant Anant
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
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