1
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Thierer JH, Foresti O, Yadav PK, Wilson MH, Moll TOC, Shen MC, Busch-Nentwich EM, Morash M, Mohlke KL, Rawls JF, Malhotra V, Hussain MM, Farber SA. Pla2g12b drives expansion of triglyceride-rich lipoproteins. Nat Commun 2024; 15:2095. [PMID: 38453914 PMCID: PMC10920679 DOI: 10.1038/s41467-024-46102-4] [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: 03/09/2023] [Accepted: 02/14/2024] [Indexed: 03/09/2024] Open
Abstract
Vertebrates transport hydrophobic triglycerides through the circulatory system by packaging them within amphipathic particles called Triglyceride-Rich Lipoproteins. Yet, it remains largely unknown how triglycerides are loaded onto these particles. Mutations in Phospholipase A2 group 12B (PLA2G12B) are known to disrupt lipoprotein homeostasis, but its mechanistic role in this process remains unclear. Here we report that PLA2G12B channels lipids within the lumen of the endoplasmic reticulum into nascent lipoproteins. This activity promotes efficient lipid secretion while preventing excess accumulation of intracellular lipids. We characterize the functional domains, subcellular localization, and interacting partners of PLA2G12B, demonstrating that PLA2G12B is calcium-dependent and tightly associated with the membrane of the endoplasmic reticulum. We also detect profound resistance to atherosclerosis in PLA2G12B mutant mice, suggesting an evolutionary tradeoff between triglyceride transport and cardiovascular disease risk. Here we identify PLA2G12B as a key driver of triglyceride incorporation into vertebrate lipoproteins.
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Affiliation(s)
- James H Thierer
- Department of Embryology, Carnegie Institution for Science, Baltimore, MD, 21218, USA
- Johns Hopkins University in Baltimore, Maryland Department of biology, Baltimore, MD, 21218, USA
| | - Ombretta Foresti
- Centre for Genomic Regulation (CRG), The Barcelona Institute for Science and Technology, Barcelona, 08003, ES, Spain
| | - Pradeep Kumar Yadav
- Department of Foundations of Medicine, NYU Long Island School of Medicine, Mineola, NY, 11501, USA
- Department of Botany, Faculty of Science, University of Allahabad, Prayagraj, India
| | - Meredith H Wilson
- Department of Embryology, Carnegie Institution for Science, Baltimore, MD, 21218, USA
- Johns Hopkins University in Baltimore, Maryland Department of biology, Baltimore, MD, 21218, USA
| | - Tabea O C Moll
- Department of Embryology, Carnegie Institution for Science, Baltimore, MD, 21218, USA
- Johns Hopkins University in Baltimore, Maryland Department of biology, Baltimore, MD, 21218, USA
| | - Meng-Chieh Shen
- Department of Embryology, Carnegie Institution for Science, Baltimore, MD, 21218, USA
| | | | - Margaret Morash
- Department of Molecular Genetics and Microbiology, Duke University, Durham, NC, 27708, USA
| | - Karen L Mohlke
- Department of Genetics, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - John F Rawls
- Department of Molecular Genetics and Microbiology, Duke University, Durham, NC, 27708, USA
| | - Vivek Malhotra
- Centre for Genomic Regulation (CRG), The Barcelona Institute for Science and Technology, Barcelona, 08003, ES, Spain
- Universitat Pompeu Fabra, Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain
| | - M Mahmood Hussain
- Department of Foundations of Medicine, NYU Long Island School of Medicine, Mineola, NY, 11501, USA
| | - Steven A Farber
- Department of Embryology, Carnegie Institution for Science, Baltimore, MD, 21218, USA.
- Johns Hopkins University in Baltimore, Maryland Department of biology, Baltimore, MD, 21218, USA.
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2
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Anaganti N, Valmiki S, Recacha R, Islam S, Farber S, Ruddock L, Hussain MM. Bulky hydrophobic side chains in the β1-sandwich of microsomal triglyceride transfer protein are critical for the transfer of both triglycerides and phospholipids. J Biol Chem 2024; 300:105726. [PMID: 38325741 PMCID: PMC10907164 DOI: 10.1016/j.jbc.2024.105726] [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: 12/18/2023] [Revised: 01/19/2024] [Accepted: 01/25/2024] [Indexed: 02/09/2024] Open
Abstract
Hyperlipidemia predisposes individuals to cardiometabolic diseases, the most common cause of global mortality. Microsomal triglyceride transfer protein (MTP) transfers multiple lipids and is essential for the assembly of apolipoprotein B-containing lipoproteins. MTP inhibition lowers plasma lipids but causes lipid retention in the liver and intestine. Previous studies suggested two lipid transfer domains in MTP and that specific inhibition of triglyceride (TG) and not phospholipid (PL) transfer can lower plasma lipids without significant tissue lipid accumulation. However, how MTP transfers different lipids and the domains involved in these activities are unknown. Here, we tested a hypothesis that two different β-sandwich domains in MTP transfer TG and PL. Mutagenesis of charged amino acids in β2-sandwich had no effect on PL transfer activity indicating that they are not critical. In contrast, amino acids with bulky hydrophobic side chains in β1-sandwich were critical for both TG and PL transfer activities. Substitutions of these residues with smaller hydrophobic side chains or positive charges reduced, whereas negatively charged side chains severely attenuated MTP lipid transfer activities. These studies point to a common lipid transfer domain for TG and PL in MTP that is enriched with bulky hydrophobic amino acids. Furthermore, we observed a strong correlation in different MTP mutants with respect to loss of both the lipid transfer activities, again implicating a common binding site for TG and PL in MTP. We propose that targeting of areas other than the identified common lipid transfer domain might reduce plasma lipids without causing cellular lipid retention.
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Affiliation(s)
- Narasimha Anaganti
- Department of Foundations of Medicine, NYU Grossman Long Island School of Medicine, Mineola, New York, USA
| | - Swati Valmiki
- Department of Foundations of Medicine, NYU Grossman Long Island School of Medicine, Mineola, New York, USA
| | - Rosario Recacha
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - Shahidul Islam
- Department of Foundations of Medicine, NYU Grossman Long Island School of Medicine, Mineola, New York, USA
| | - Steven Farber
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Lloyd Ruddock
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - M Mahmood Hussain
- Department of Foundations of Medicine, NYU Grossman Long Island School of Medicine, Mineola, New York, USA.
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3
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Kozan DW, Derrick JT, Ludington WB, Farber SA. From worms to humans: Understanding intestinal lipid metabolism via model organisms. Biochim Biophys Acta Mol Cell Biol Lipids 2023; 1868:159290. [PMID: 36738984 PMCID: PMC9974936 DOI: 10.1016/j.bbalip.2023.159290] [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: 08/26/2022] [Revised: 01/10/2023] [Accepted: 01/19/2023] [Indexed: 02/05/2023]
Abstract
The intestine is responsible for efficient absorption and packaging of dietary lipids before they enter the circulatory system. This review provides a comprehensive overview of how intestinal enterocytes from diverse model organisms absorb dietary lipid and subsequently secrete the largest class of lipoproteins (chylomicrons) to meet the unique needs of each animal. We discuss the putative relationship between diet and metabolic disease progression, specifically Type 2 Diabetes Mellitus. Understanding the molecular response of intestinal cells to dietary lipid has the potential to undercover novel therapies to combat metabolic syndrome.
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Affiliation(s)
- Darby W Kozan
- Department of Biology, Johns Hopkins University, Baltimore, MD, United States; Department of Embryology, Carnegie Institute for Science, Baltimore, MD, United States
| | - Joshua T Derrick
- Department of Biology, Johns Hopkins University, Baltimore, MD, United States; Department of Embryology, Carnegie Institute for Science, Baltimore, MD, United States
| | - William B Ludington
- Department of Biology, Johns Hopkins University, Baltimore, MD, United States; Department of Embryology, Carnegie Institute for Science, Baltimore, MD, United States
| | - Steven A Farber
- Department of Biology, Johns Hopkins University, Baltimore, MD, United States; Department of Embryology, Carnegie Institute for Science, Baltimore, MD, United States.
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4
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Rajan S, Hofer P, Christiano A, Stevenson M, Ragolia L, Villa-Cuesta E, Fried SK, Lau R, Braithwaite C, Zechner R, Schwartz GJ, Hussain MM. Microsomal triglyceride transfer protein regulates intracellular lipolysis in adipocytes independent of its lipid transfer activity. Metabolism 2022; 137:155331. [PMID: 36228741 DOI: 10.1016/j.metabol.2022.155331] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 09/21/2022] [Accepted: 10/06/2022] [Indexed: 11/22/2022]
Abstract
BACKGROUND The triglyceride (TG) transfer activity of microsomal triglyceride transfer protein (MTP) is essential for lipoprotein assembly in the liver and intestine; however, its function in adipose tissue, which does not assemble lipoproteins, is unknown. Here we have elucidated the function of MTP in adipocytes. APPROACH AND RESULTS We demonstrated that MTP is present on lipid droplets in human adipocytes. Adipose-specific MTP deficient (A-Mttp-/-) male and female mice fed an obesogenic diet gained less weight than Mttpf/f mice, had less fat mass, smaller adipocytes and were insulin sensitive. A-Mttp-/- mice showed higher energy expenditure than Mttpf/f mice. During a cold challenge, A-Mttp-/- mice maintained higher body temperature by mobilizing more fatty acids. Biochemical studies indicated that MTP deficiency de-repressed adipose triglyceride lipase (ATGL) activity and increased TG lipolysis. Both wild type MTP and mutant MTP deficient in TG transfer activity interacted with and inhibited ATGL activity. Thus, the TG transfer activity of MTP is not required for ATGL inhibition. C-terminally truncated ATGL that retains its lipase activity interacted less efficiently than full-length ATGL. CONCLUSION Our findings demonstrate that adipose-specific MTP deficiency increases ATGL-mediated TG lipolysis and enhances energy expenditure, thereby resisting diet-induced obesity. We speculate that the regulatory function of MTP involving protein-protein interactions might have evolved before the acquisition of TG transfer activity in vertebrates. Adipose-specific inhibition of MTP-ATGL interactions may ameliorate obesity while avoiding the adverse effects associated with inhibition of the lipid transfer activity of MTP.
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Affiliation(s)
- Sujith Rajan
- Department of Foundations of Medicine, New York University Long Island School of Medicine, Mineola, NY 11501, United States of America
| | - Peter Hofer
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Amanda Christiano
- Department of Foundations of Medicine, New York University Long Island School of Medicine, Mineola, NY 11501, United States of America
| | - Matthew Stevenson
- Department of Foundations of Medicine, New York University Long Island School of Medicine, Mineola, NY 11501, United States of America
| | - Louis Ragolia
- Department of Foundations of Medicine, New York University Long Island School of Medicine, Mineola, NY 11501, United States of America
| | - Eugenia Villa-Cuesta
- Department of Biology, College of Arts and Science, Adelphi University, Garden City, NY 11530, United States of America
| | - Susan K Fried
- Diabetes, Obesity, and Metabolism Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
| | - Raymond Lau
- Department of Surgery, New York University Long Island School of Medicine, Mineola, NY 11501, United States of America
| | - Collin Braithwaite
- Department of Surgery, New York University Long Island School of Medicine, Mineola, NY 11501, United States of America
| | - Rudolf Zechner
- Institute of Molecular Biosciences, University of Graz, Graz, Austria; BioTechMed-Graz, Austria; BioHealth Field of Excellence, University of Graz, Graz, Austria
| | - Gary J Schwartz
- Department of Medicine and Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, United States of America.
| | - M Mahmood Hussain
- Department of Foundations of Medicine, New York University Long Island School of Medicine, Mineola, NY 11501, United States of America; Veterans Affairs New York Harbor Healthcare System, Brooklyn, NY, United States of America.
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5
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Anaganti N, Chattopadhyay A, Poirier JT, Hussain MM. Generation of hepatoma cell lines deficient in microsomal triglyceride transfer protein. J Lipid Res 2022; 63:100257. [PMID: 35931202 PMCID: PMC9405095 DOI: 10.1016/j.jlr.2022.100257] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 07/03/2022] [Accepted: 07/08/2022] [Indexed: 01/05/2023] Open
Abstract
The microsomal triglyceride transfer protein (MTP) is essential for the secretion of apolipoprotein B (apoB)48- and apoB100-containing lipoproteins in the intestine and liver, respectively. Loss of function mutations in MTP cause abetalipoproteinemia. Heterologous cells are used to evaluate the function of MTP in apoB secretion to avoid background MTP activity in liver and intestine-derived cells. However, these systems are not suitable to study the role of MTP in the secretion of apoB100-containing lipoproteins, as expression of a large apoB100 peptide using plasmids is difficult. Here, we report a new cell culture model amenable for studying the role of different MTP mutations on apoB100 secretion. The endogenous MTTP gene was ablated in human hepatoma Huh-7 cells using single guide RNA and RNA-guided clustered regularly interspaced short palindromic repeats-associated sequence 9 ribonucleoprotein complexes. We successfully established three different clones that did not express any detectable MTTP mRNA or MTP protein or activity. These cells were defective in secreting apoB-containing lipoproteins and accumulated lipids. Furthermore, we show that transfection of these cells with plasmids expressing human MTTP cDNA resulted in the expression of MTP protein, restoration of triglyceride transfer activity, and secretion of apoB100. Thus, these new cells can be valuable tools for studying structure-function of MTP, roles of different missense mutations in various lipid transfer activities of MTP, and their ability to support apoB100 secretion, compensatory changes associated with loss of MTP, and in the identification of novel proteins that may require MTP for their synthesis and secretion.
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Affiliation(s)
- Narasimha Anaganti
- Department of Foundations of Medicine, NYU Long Island School of Medicine, Mineola, NY, USA
| | - Atrayee Chattopadhyay
- Department of Foundations of Medicine, NYU Long Island School of Medicine, Mineola, NY, USA
| | - John T Poirier
- Perlmutter Cancer Center, New York University Langone Health, New York, NY, USA
| | - M Mahmood Hussain
- Department of Foundations of Medicine, NYU Long Island School of Medicine, Mineola, NY, USA; VA New York Harbor Healthcare System, Brooklyn, NY, USA.
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6
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Wilson MH, Rajan S, Danoff A, White RJ, Hensley MR, Quinlivan VH, Recacha R, Thierer JH, Tan FJ, Busch-Nentwich EM, Ruddock L, Hussain MM, Farber SA. A point mutation decouples the lipid transfer activities of microsomal triglyceride transfer protein. PLoS Genet 2020; 16:e1008941. [PMID: 32760060 PMCID: PMC7444587 DOI: 10.1371/journal.pgen.1008941] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 08/18/2020] [Accepted: 06/17/2020] [Indexed: 01/08/2023] Open
Abstract
Apolipoprotein B-containing lipoproteins (B-lps) are essential for the transport of hydrophobic dietary and endogenous lipids through the circulation in vertebrates. Zebrafish embryos produce large numbers of B-lps in the yolk syncytial layer (YSL) to move lipids from yolk to growing tissues. Disruptions in B-lp production perturb yolk morphology, readily allowing for visual identification of mutants with altered B-lp metabolism. Here we report the discovery of a missense mutation in microsomal triglyceride transfer protein (Mtp), a protein that is essential for B-lp production. This mutation of a conserved glycine residue to valine (zebrafish G863V, human G865V) reduces B-lp production and results in yolk opacity due to aberrant accumulation of cytoplasmic lipid droplets in the YSL. However, this phenotype is milder than that of the previously reported L475P stalactite (stl) mutation. MTP transfers lipids, including triglycerides and phospholipids, to apolipoprotein B in the ER for B-lp assembly. In vitro lipid transfer assays reveal that while both MTP mutations eliminate triglyceride transfer activity, the G863V mutant protein unexpectedly retains ~80% of phospholipid transfer activity. This residual phospholipid transfer activity of the G863V mttp mutant protein is sufficient to support the secretion of small B-lps, which prevents intestinal fat malabsorption and growth defects observed in the mttpstl/stl mutant zebrafish. Modeling based on the recent crystal structure of the heterodimeric human MTP complex suggests the G865V mutation may block triglyceride entry into the lipid-binding cavity. Together, these data argue that selective inhibition of MTP triglyceride transfer activity may be a feasible therapeutic approach to treat dyslipidemia and provide structural insight for drug design. These data also highlight the power of yolk transport studies to identify proteins critical for B-lp biology.
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Affiliation(s)
- Meredith H. Wilson
- Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland, United States of America
| | - Sujith Rajan
- New York University Long Island School of Medicine, Mineola, New York, United States of America
| | - Aidan Danoff
- Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland, United States of America
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Richard J. White
- Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
- Cambridge Institute of Therapeutic Immunology & Infectious Disease, Department of Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Monica R. Hensley
- Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland, United States of America
| | - Vanessa H. Quinlivan
- Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland, United States of America
| | - Rosario Recacha
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - James H. Thierer
- Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland, United States of America
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Frederick J. Tan
- Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland, United States of America
| | - Elisabeth M. Busch-Nentwich
- Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
- Cambridge Institute of Therapeutic Immunology & Infectious Disease, Department of Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Lloyd Ruddock
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - M. Mahmood Hussain
- New York University Long Island School of Medicine, Mineola, New York, United States of America
| | - Steven A. Farber
- Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland, United States of America
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, United States of America
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7
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Iqbal J, Jahangir Z, Al-Qarni AA. Microsomal Triglyceride Transfer Protein: From Lipid Metabolism to Metabolic Diseases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1276:37-52. [DOI: 10.1007/978-981-15-6082-8_4] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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8
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Triacylglycerol Metabolism in Drosophila melanogaster. Genetics 2019; 210:1163-1184. [PMID: 30523167 DOI: 10.1534/genetics.118.301583] [Citation(s) in RCA: 107] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2018] [Accepted: 09/11/2018] [Indexed: 12/11/2022] Open
Abstract
Triacylglycerol (TAG) is the most important caloric source with respect to energy homeostasis in animals. In addition to its evolutionarily conserved importance as an energy source, TAG turnover is crucial to the metabolism of structural and signaling lipids. These neutral lipids are also key players in development and disease. Here, we review the metabolism of TAG in the Drosophila model system. Recently, the fruit fly has attracted renewed attention in research due to the unique experimental approaches it affords in studying the tissue-autonomous and interorgan regulation of lipid metabolism in vivo Following an overview of the systemic control of fly body fat stores, we will cover lipid anabolic, enzymatic, and regulatory processes, which begin with the dietary lipid breakdown and de novo lipogenesis that results in lipid droplet storage. Next, we focus on lipolytic processes, which mobilize storage TAG to make it metabolically accessible as either an energy source or as a building block for biosynthesis of other lipid classes. Since the buildup and breakdown of fat involves various organs, we highlight avenues of lipid transport, which are at the heart of functional integration of organismic lipid metabolism. Finally, we draw attention to some "missing links" in basic neutral lipid metabolism and conclude with a perspective on how fly research can be exploited to study functional metabolic roles of diverse lipids.
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9
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Sirwi A, Hussain MM. Lipid transfer proteins in the assembly of apoB-containing lipoproteins. J Lipid Res 2018; 59:1094-1102. [PMID: 29650752 DOI: 10.1194/jlr.r083451] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Revised: 04/12/2018] [Indexed: 11/20/2022] Open
Abstract
A better understanding of intracellular lipoprotein assembly may help identify proteins with important roles in lipid disorders. apoB-containing lipoproteins (B-lps) are macromolecular lipid and protein micelles that act as specialized transport vehicles for hydrophobic lipids. They are assembled predominantly in enterocytes and hepatocytes to transport dietary and endogenous fat, respectively, to different tissues. Assembly occurs in the endoplasmic reticulum (ER) and is dependent on lipid resynthesis in the ER and on a chaperone, namely, microsomal triglyceride transfer protein (MTTP). Precursors for lipid synthesis are obtained from extracellular sources and from cytoplasmic lipid droplets. MTTP is the major and essential lipid transfer protein that transfers phospholipids and triacylglycerols to nascent apoB for the assembly of lipoproteins. Assembly is aided by cell death-inducing DFF45-like effector B and by phospholipid transfer protein, which may facilitate additional deposition of triacylglycerols and phospholipids, respectively, to apoB. Here, we summarize the current understanding of the different steps in the assembly of B-lps and discuss the role of lipid transfer proteins in these steps to help identify new clinical targets for lipid-associated disorders, such as heart disease.
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Affiliation(s)
- Alaa Sirwi
- School of Graduate Studies, Molecular and Cell Biology Program, State University of New York Downstate Medical Center, Brooklyn, NY
| | - M Mahmood Hussain
- New York University Winthrop Hospital, Mineola, NY and Veterans Affairs New York Harbor Healthcare System, Brooklyn, NY
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10
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Nazario-Yepiz NO, Loustalot-Laclette MR, Carpinteyro-Ponce J, Abreu-Goodger C, Markow TA. Transcriptional responses of ecologically diverse Drosophila species to larval diets differing in relative sugar and protein ratios. PLoS One 2017; 12:e0183007. [PMID: 28832647 PMCID: PMC5568408 DOI: 10.1371/journal.pone.0183007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Accepted: 07/27/2017] [Indexed: 11/22/2022] Open
Abstract
We utilized three ecologically diverse Drosophila species to explore the influence of ecological adaptation on transcriptomic responses to isocaloric diets differing in their relative proportions of protein to sugar. Drosophila melanogaster, a cosmopolitan species that breeds in decaying fruit, exemplifies individuals long exposed to a Western diet higher in sugar, while the natural diet of the cactophilic D. mojavensis, is much lower in carbohydrates. Drosophila arizonae, the sister species of D. mojavensis, is largely cactophilic, but also utilizes rotting fruits that are higher in sugars than cacti. We exposed third instar larvae for 24 hours to diets either (1) high in protein relative to sugar, (2) diets with equal amounts of protein and sugar, and (3) diets low in protein but high in sugar. As we predicted, based upon earlier interspecific studies of development and metabolism, the most extreme differences in gene expression under different dietary conditions were found in D. mojavensis followed by D. arizonae. No differential expression among diets was observed for D. melanogaster, a species that survives well under all three conditions, with little impact on its metabolism. We suggest that these three species together provide a model to examine individual and population differences in vulnerability to lifestyle-associated health problems such as metabolic syndrome and diabetes.
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Affiliation(s)
| | | | - Javier Carpinteyro-Ponce
- Laboratorio Nacional de la Genomica de Biodiversidad, Irapuato, Guanajuato, Mexico
- Department of Biology, University of Maryland, College Park, Maryland, United States of America
| | - Cei Abreu-Goodger
- Laboratorio Nacional de la Genomica de Biodiversidad, Irapuato, Guanajuato, Mexico
| | - Therese Ann Markow
- Laboratorio Nacional de la Genomica de Biodiversidad, Irapuato, Guanajuato, Mexico
- Department of Cell and Molecular Biology, University of California San Diego, La Jolla, California, United States of America
- * E-mail:
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11
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Khan MT, Dalvin S, Nilsen F, Male R. Microsomal triglyceride transfer protein in the ectoparasitic crustacean salmon louse ( Lepeophtheirus salmonis). J Lipid Res 2017; 58:1613-1623. [PMID: 28601811 PMCID: PMC5538283 DOI: 10.1194/jlr.m076430] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Revised: 05/10/2017] [Indexed: 11/20/2022] Open
Abstract
The salmon louse, Lepeophtheirus salmonis, is an endemic ectoparasite on salmonid fish that is challenging for the salmon farming industry and wild fish. Salmon lice produce high numbers of offspring, necessitating sequestration of large amounts of lipids into growing oocytes as a major energy source for larvae, most probably mediated by lipoproteins. The microsomal triglyceride transfer protein (MTP) is essential for the assembly of lipoproteins. Salmon lice have three L. salmonis MTP (LsMTP) transcript variants encoding two different protein isoforms, which are predicted to contain three β-sheets (N, C, and A) and a central helical domain, similar to MTPs from other species. In adult females, the LsMTPs are differently transcribed in the sub-cuticular tissues, the intestine, the ovary, and in the mature eggs. RNA interference-mediated knockdown of LsMTP in mature females gave offspring with significantly fewer neutral lipids in their yolk and only 10-30% survival. The present study suggests the importance of LsMTP in reproduction and lipid metabolism in adult female L. salmonis, a possible metabolic bottleneck that could be exploited for the development of new anti-parasitic treatment methods.
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Affiliation(s)
| | - Sussie Dalvin
- Sea Lice Research Centre, Institute of Marine Research, 5817 Bergen, Norway
| | - Frank Nilsen
- Departments of Biology University of Bergen, N-5020 Bergen, Norway
| | - Rune Male
- Molecular Biology, Sea Lice Research Centre, University of Bergen, N-5020 Bergen, Norway.
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12
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Walsh MT, Hussain MM. Targeting microsomal triglyceride transfer protein and lipoprotein assembly to treat homozygous familial hypercholesterolemia. Crit Rev Clin Lab Sci 2016; 54:26-48. [PMID: 27690713 DOI: 10.1080/10408363.2016.1221883] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Homozygous familial hypercholesterolemia (HoFH) is a polygenic disease arising from defects in the clearance of plasma low-density lipoprotein (LDL), which results in extremely elevated plasma LDL cholesterol (LDL-C) and increased risk of atherosclerosis, coronary heart disease, and premature death. Conventional lipid-lowering therapies, such as statins and ezetimibe, are ineffective at lowering plasma cholesterol to safe levels in these patients. Other therapeutic options, such as LDL apheresis and liver transplantation, are inconvenient, costly, and not readily available. Recently, lomitapide was approved by the Federal Drug Administration as an adjunct therapy for the treatment of HoFH. Lomitapide inhibits microsomal triglyceride transfer protein (MTP), reduces lipoprotein assembly and secretion, and lowers plasma cholesterol levels by over 50%. Here, we explain the steps involved in lipoprotein assembly, summarize the role of MTP in lipoprotein assembly, explore the clinical and molecular basis of HoFH, and review pre-clinical studies and clinical trials with lomitapide and other MTP inhibitors for the treatment of HoFH. In addition, ongoing research and new approaches underway for better treatment modalities are discussed.
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Affiliation(s)
- Meghan T Walsh
- a School of Graduate Studies, Molecular and Cell Biology Program, State University of New York Downstate Medical Center , Brooklyn , NY , USA.,b Department of Cell Biology , State University of New York Downstate Medical Center , Brooklyn , NY , USA
| | - M Mahmood Hussain
- b Department of Cell Biology , State University of New York Downstate Medical Center , Brooklyn , NY , USA.,c Department of Pediatrics , SUNY Downstate Medical Center , Brooklyn , NY , USA.,d VA New York Harbor Healthcare System , Brooklyn , NY , USA , and.,e Winthrop University Hospital , Mineola , NY , USA
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Kanost MR, Arrese EL, Cao X, Chen YR, Chellapilla S, Goldsmith MR, Grosse-Wilde E, Heckel DG, Herndon N, Jiang H, Papanicolaou A, Qu J, Soulages JL, Vogel H, Walters J, Waterhouse RM, Ahn SJ, Almeida FC, An C, Aqrawi P, Bretschneider A, Bryant WB, Bucks S, Chao H, Chevignon G, Christen JM, Clarke DF, Dittmer NT, Ferguson LCF, Garavelou S, Gordon KHJ, Gunaratna RT, Han Y, Hauser F, He Y, Heidel-Fischer H, Hirsh A, Hu Y, Jiang H, Kalra D, Klinner C, König C, Kovar C, Kroll AR, Kuwar SS, Lee SL, Lehman R, Li K, Li Z, Liang H, Lovelace S, Lu Z, Mansfield JH, McCulloch KJ, Mathew T, Morton B, Muzny DM, Neunemann D, Ongeri F, Pauchet Y, Pu LL, Pyrousis I, Rao XJ, Redding A, Roesel C, Sanchez-Gracia A, Schaack S, Shukla A, Tetreau G, Wang Y, Xiong GH, Traut W, Walsh TK, Worley KC, Wu D, Wu W, Wu YQ, Zhang X, Zou Z, Zucker H, Briscoe AD, Burmester T, Clem RJ, Feyereisen R, Grimmelikhuijzen CJP, Hamodrakas SJ, Hansson BS, Huguet E, Jermiin LS, Lan Q, Lehman HK, Lorenzen M, Merzendorfer H, Michalopoulos I, Morton DB, Muthukrishnan S, Oakeshott JG, Palmer W, Park Y, Passarelli AL, Rozas J, Schwartz LM, Smith W, Southgate A, Vilcinskas A, Vogt R, Wang P, Werren J, Yu XQ, Zhou JJ, Brown SJ, Scherer SE, Richards S, Blissard GW. Multifaceted biological insights from a draft genome sequence of the tobacco hornworm moth, Manduca sexta. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2016; 76:118-147. [PMID: 27522922 PMCID: PMC5010457 DOI: 10.1016/j.ibmb.2016.07.005] [Citation(s) in RCA: 120] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 06/27/2016] [Accepted: 07/14/2016] [Indexed: 05/19/2023]
Abstract
Manduca sexta, known as the tobacco hornworm or Carolina sphinx moth, is a lepidopteran insect that is used extensively as a model system for research in insect biochemistry, physiology, neurobiology, development, and immunity. One important benefit of this species as an experimental model is its extremely large size, reaching more than 10 g in the larval stage. M. sexta larvae feed on solanaceous plants and thus must tolerate a substantial challenge from plant allelochemicals, including nicotine. We report the sequence and annotation of the M. sexta genome, and a survey of gene expression in various tissues and developmental stages. The Msex_1.0 genome assembly resulted in a total genome size of 419.4 Mbp. Repetitive sequences accounted for 25.8% of the assembled genome. The official gene set is comprised of 15,451 protein-coding genes, of which 2498 were manually curated. Extensive RNA-seq data from many tissues and developmental stages were used to improve gene models and for insights into gene expression patterns. Genome wide synteny analysis indicated a high level of macrosynteny in the Lepidoptera. Annotation and analyses were carried out for gene families involved in a wide spectrum of biological processes, including apoptosis, vacuole sorting, growth and development, structures of exoskeleton, egg shells, and muscle, vision, chemosensation, ion channels, signal transduction, neuropeptide signaling, neurotransmitter synthesis and transport, nicotine tolerance, lipid metabolism, and immunity. This genome sequence, annotation, and analysis provide an important new resource from a well-studied model insect species and will facilitate further biochemical and mechanistic experimental studies of many biological systems in insects.
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Affiliation(s)
- Michael R Kanost
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS, 66506, USA.
| | - Estela L Arrese
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK, 74078, USA
| | - Xiaolong Cao
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA
| | - Yun-Ru Chen
- Boyce Thompson Institute at Cornell University, Tower Road, Ithaca, NY, 14853, USA
| | - Sanjay Chellapilla
- KSU Bioinformatics Center, Division of Biology, Kansas State University, Manhattan, KS, 66506, USA
| | - Marian R Goldsmith
- Biological Sciences Department, University of Rhode Island, Kingston, RI, 02881, USA
| | - Ewald Grosse-Wilde
- Max Planck Institute for Chemical Ecology, Department of Evolutionary Neuroethology, Hans-Knoell-Strasse, 8, D-07745, Jena, Germany
| | - David G Heckel
- Department of Entomology, Max Planck Institute for Chemical Ecology, Hans-Knoell-Strasse 8, 07745, Jena, Germany
| | - Nicolae Herndon
- KSU Bioinformatics Center, Division of Biology, Kansas State University, Manhattan, KS, 66506, USA
| | - Haobo Jiang
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA
| | - Alexie Papanicolaou
- Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW, 2753, Australia
| | - Jiaxin Qu
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA
| | - Jose L Soulages
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK, 74078, USA
| | - Heiko Vogel
- Department of Entomology, Max Planck Institute for Chemical Ecology, Hans-Knoell-Strasse 8, 07745, Jena, Germany
| | - James Walters
- Department of Ecology and Evolutionary Biology, Univ. Kansas, Lawrence, KS, 66045, USA
| | - Robert M Waterhouse
- Department of Genetic Medicine and Development, University of Geneva Medical School, rue Michel-Servet 1, 1211, Geneva, Switzerland; Swiss Institute of Bioinformatics, rue Michel-Servet 1, 1211, Geneva, Switzerland; Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, 32 Vassar Street, Cambridge, MA, 02139, USA; The Broad Institute of MIT and Harvard, Cambridge, 415 Main Street, MA, 02142, USA
| | - Seung-Joon Ahn
- Department of Entomology, Max Planck Institute for Chemical Ecology, Hans-Knoell-Strasse 8, 07745, Jena, Germany
| | - Francisca C Almeida
- Departament de Genètica and Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Spain
| | - Chunju An
- Department of Entomology, China Agricultural University, Beijing, China
| | - Peshtewani Aqrawi
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA
| | - Anne Bretschneider
- Department of Entomology, Max Planck Institute for Chemical Ecology, Hans-Knoell-Strasse 8, 07745, Jena, Germany
| | - William B Bryant
- Division of Biology, Kansas State University, Manhattan, KS, 66506, USA
| | - Sascha Bucks
- Max Planck Institute for Chemical Ecology, Department of Evolutionary Neuroethology, Hans-Knoell-Strasse, 8, D-07745, Jena, Germany
| | - Hsu Chao
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA
| | - Germain Chevignon
- Institut de Recherche sur la Biologie de l'Insecte, UMR CNRS 7261, UFR Sciences et Techniques, Université François-Rabelais, Tours, France
| | - Jayne M Christen
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS, 66506, USA
| | - David F Clarke
- CSIRO Land and Water, Clunies Ross St, Acton, ACT, 2601, Australia
| | - Neal T Dittmer
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS, 66506, USA
| | | | - Spyridoula Garavelou
- Centre of Systems Biology, Biomedical Research Foundation, Academy of Athens, Athens, Greece
| | - Karl H J Gordon
- CSIRO Health and Biosecurity, Clunies Ross St, Acton, ACT, 2601, Australia
| | - Ramesh T Gunaratna
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA
| | - Yi Han
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA
| | - Frank Hauser
- Center for Functional and Comparative Insect Genomics, Department of Biology, University of Copenhagen, Universitetsparken 15, DK-21oo, Copenhagen, Denmark
| | - Yan He
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA
| | - Hanna Heidel-Fischer
- Department of Entomology, Max Planck Institute for Chemical Ecology, Hans-Knoell-Strasse 8, 07745, Jena, Germany
| | - Ariana Hirsh
- Department of Biology, Barnard College, Columbia University, 3009 Broadway, New York, NY, 10027, USA
| | - Yingxia Hu
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA
| | - Hongbo Jiang
- Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing, 400715, China
| | - Divya Kalra
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA
| | - Christian Klinner
- Max Planck Institute for Chemical Ecology, Department of Evolutionary Neuroethology, Hans-Knoell-Strasse, 8, D-07745, Jena, Germany
| | - Christopher König
- Max Planck Institute for Chemical Ecology, Department of Evolutionary Neuroethology, Hans-Knoell-Strasse, 8, D-07745, Jena, Germany
| | - Christie Kovar
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA
| | - Ashley R Kroll
- Department of Biology, Reed College, Portland, OR, 97202, USA
| | - Suyog S Kuwar
- Department of Entomology, Max Planck Institute for Chemical Ecology, Hans-Knoell-Strasse 8, 07745, Jena, Germany
| | - Sandy L Lee
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA
| | - Rüdiger Lehman
- Fraunhofer Institute for Molecular Biology and Applied Ecology (IME), Bioresources Project Group, Winchesterstrasse 2, 35394, Gießen, Germany
| | - Kai Li
- College of Chemistry, Chemical Engineering, and Biotechnology, Donghua University, Shanghai, 201620, China
| | - Zhaofei Li
- College of Plant Protection, Northwest A&F University, Yangling, Shaanxi, 712100, China
| | - Hanquan Liang
- McDermott Center for Human Growth and Development, UT Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX, 75390, USA
| | - Shanna Lovelace
- Department of Biological Sciences, University of Southern Maine, Portland, ME, 04104, USA
| | - Zhiqiang Lu
- College of Plant Protection, Northwest A&F University, Yangling, Shaanxi, 712100, China
| | - Jennifer H Mansfield
- Department of Biology, Barnard College, Columbia University, 3009 Broadway, New York, NY, 10027, USA
| | - Kyle J McCulloch
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA, 92697, USA
| | - Tittu Mathew
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA
| | - Brian Morton
- Department of Biology, Barnard College, Columbia University, 3009 Broadway, New York, NY, 10027, USA
| | - Donna M Muzny
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA
| | - David Neunemann
- Department of Entomology, Max Planck Institute for Chemical Ecology, Hans-Knoell-Strasse 8, 07745, Jena, Germany
| | - Fiona Ongeri
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA
| | - Yannick Pauchet
- Department of Entomology, Max Planck Institute for Chemical Ecology, Hans-Knoell-Strasse 8, 07745, Jena, Germany
| | - Ling-Ling Pu
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA
| | - Ioannis Pyrousis
- Centre of Systems Biology, Biomedical Research Foundation, Academy of Athens, Athens, Greece
| | - Xiang-Jun Rao
- School of Plant Protection, Anhui Agricultural University, Hefei, Anhui, China
| | - Amanda Redding
- Department of Biology, University of Rochester, Rochester, NY, 14627, USA
| | - Charles Roesel
- Department of Marine and Environmental Sciences, Northeastern University, Boston, MA, 02115, USA
| | - Alejandro Sanchez-Gracia
- Departament de Genètica and Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Spain
| | - Sarah Schaack
- Department of Biology, Reed College, Portland, OR, 97202, USA
| | - Aditi Shukla
- Department of Biology, Barnard College, Columbia University, 3009 Broadway, New York, NY, 10027, USA
| | - Guillaume Tetreau
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, 14456, USA
| | - Yang Wang
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA
| | - Guang-Hua Xiong
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Walther Traut
- Institut fuer Biologie, Universitaet Luebeck, D-23538, Luebeck, Germany
| | - Tom K Walsh
- CSIRO Land and Water, Clunies Ross St, Acton, ACT, 2601, Australia
| | - Kim C Worley
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA
| | - Di Wu
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS, 66506, USA
| | - Wenbi Wu
- Division of Biology, Kansas State University, Manhattan, KS, 66506, USA
| | - Yuan-Qing Wu
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA
| | - Xiufeng Zhang
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA
| | - Zhen Zou
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Hannah Zucker
- Neuroscience Program, Hamilton College, Clinton, NY, 13323, USA
| | - Adriana D Briscoe
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA, 92697, USA
| | | | - Rollie J Clem
- Division of Biology, Kansas State University, Manhattan, KS, 66506, USA
| | - René Feyereisen
- Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Cornelis J P Grimmelikhuijzen
- Center for Functional and Comparative Insect Genomics, Department of Biology, University of Copenhagen, Universitetsparken 15, DK-21oo, Copenhagen, Denmark
| | - Stavros J Hamodrakas
- Department of Cell Biology and Biophysics, Faculty of Biology, University of Athens, Athens, Greece
| | - Bill S Hansson
- Max Planck Institute for Chemical Ecology, Department of Evolutionary Neuroethology, Hans-Knoell-Strasse, 8, D-07745, Jena, Germany
| | - Elisabeth Huguet
- Institut de Recherche sur la Biologie de l'Insecte, UMR CNRS 7261, UFR Sciences et Techniques, Université François-Rabelais, Tours, France
| | - Lars S Jermiin
- CSIRO Land and Water, Clunies Ross St, Acton, ACT, 2601, Australia
| | - Que Lan
- Department of Entomology, University of Wisconsin, Madison, USA
| | - Herman K Lehman
- Biology Department and Neuroscience Program, Hamilton College, Clinton, NY, 13323, USA
| | - Marce Lorenzen
- Dept. Entomology, North Carolina State Univ., Raleigh, NC, 27695, USA
| | - Hans Merzendorfer
- University of Siegen, School of Natural Sciences and Engineering, Institute of Biology - Molecular Biology, Adolf-Reichwein-Strasse. 2, AR-C3010, 57076 Siegen, Germany
| | - Ioannis Michalopoulos
- Centre of Systems Biology, Biomedical Research Foundation, Academy of Athens, Athens, Greece
| | - David B Morton
- Department of Integrative Biosciences, School of Dentistry, BRB421, L595, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd., Portland, OR, 97239, USA
| | - Subbaratnam Muthukrishnan
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS, 66506, USA
| | - John G Oakeshott
- CSIRO Land and Water, Clunies Ross St, Acton, ACT, 2601, Australia
| | - Will Palmer
- Department of Genetics, University of Cambridge, Downing St, Cambridge, CB2 3EH, UK
| | - Yoonseong Park
- Department of Entomology, Kansas State University, Manhattan, KS, 66506, USA
| | | | - Julio Rozas
- Departament de Genètica and Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Spain
| | | | - Wendy Smith
- Department of Biology, Northeastern University, Boston, MA, 02115, USA
| | - Agnes Southgate
- Department of Biology, College of Charleston, Charleston, SC, 29424, USA
| | - Andreas Vilcinskas
- Institute for Insect Biotechnology, Justus-Liebig-University, Heinrich-Buff-Ring 26-32, 35392, Giessen, Germany
| | - Richard Vogt
- Department of Biological Sciences, University of South Carolina, Columbia, SC, 29205, USA
| | - Ping Wang
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, 14456, USA
| | - John Werren
- Department of Biology, University of Rochester, Rochester, NY, 14627, USA
| | - Xiao-Qiang Yu
- University of Missouri-Kansas City, 5007 Rockhill Road, Kansas City, MO, 64110, USA
| | - Jing-Jiang Zhou
- Department of Biological Chemistry and Crop Protection, Rothamsted Research, Harpenden, Herts, AL5 2JQ, UK
| | - Susan J Brown
- KSU Bioinformatics Center, Division of Biology, Kansas State University, Manhattan, KS, 66506, USA
| | - Steven E Scherer
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA
| | - Stephen Richards
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA
| | - Gary W Blissard
- Boyce Thompson Institute at Cornell University, Tower Road, Ithaca, NY, 14853, USA
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Walsh MT, Iqbal J, Josekutty J, Soh J, Di Leo E, Özaydin E, Gündüz M, Tarugi P, Hussain MM. Novel Abetalipoproteinemia Missense Mutation Highlights the Importance of the N-Terminal β-Barrel in Microsomal Triglyceride Transfer Protein Function. ACTA ACUST UNITED AC 2015. [PMID: 26224785 DOI: 10.1161/circgenetics.115.001106] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND The use of microsomal triglyceride transfer protein (MTP) inhibitors is limited to severe hyperlipidemias because of associated hepatosteatosis and gastrointestinal adverse effects. Comprehensive knowledge about the structure-function of MTP might help design new molecules that avoid steatosis. Characterization of mutations in MTP causing abetalipoproteinemia has revealed that the central α-helical and C-terminal β-sheet domains are important for protein disulfide isomerase binding and lipid transfer activity. Our aim was to identify and characterize mutations in the N-terminal domain to understand its function. METHODS AND RESULTS We identified a novel missense mutation (D169V) in a 4-month-old Turkish male child with severe signs of abetalipoproteinemia. To study the effect of this mutation on MTP function, we created mutants via site-directed mutagenesis. Although D169V was expressed in the endoplasmic reticulum and interacted with apolipoprotein B (apoB) 17, it was unable to bind protein disulfide isomerase, transfer lipids, and support apoB secretion. Computational modeling suggested that D169 could form an internal salt bridge with K187 and K189. Mutagenesis of these lysines to leucines abolished protein disulfide isomerase heterodimerization, lipid transfer, and apoB secretion, without affecting apoB17 binding. Furthermore, mutants with preserved charges (D169E, K187R, and K189R) rescued these activities. CONCLUSIONS D169V is detrimental because it disrupts an internal salt bridge leading to loss of protein disulfide isomerase binding and lipid transfer activities; however, it does not affect apoB binding. Thus, the N-terminal domain of MTP is also important for its lipid transfer activity.
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Affiliation(s)
- Meghan T Walsh
- From the School of Graduate Studies, Molecular and Cell Biology Program (M.T.W., J.J., J.S.), Department of Cell Biology (M.T.W., J.I., J.J., J.S., M.M.H.), Department of Pediatrics (M.M.H.), State University of New York Downstate Medical Center, Brooklyn, NY; Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy (E.D.L., P.T.); Infancy Services, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (E.O); Department of Nutrition and Metabolism, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (M.G.); and Department of Research, VA New York Harbor Healthcare System, Brooklyn, NY (M.M.H.)
| | - Jahangir Iqbal
- From the School of Graduate Studies, Molecular and Cell Biology Program (M.T.W., J.J., J.S.), Department of Cell Biology (M.T.W., J.I., J.J., J.S., M.M.H.), Department of Pediatrics (M.M.H.), State University of New York Downstate Medical Center, Brooklyn, NY; Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy (E.D.L., P.T.); Infancy Services, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (E.O); Department of Nutrition and Metabolism, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (M.G.); and Department of Research, VA New York Harbor Healthcare System, Brooklyn, NY (M.M.H.)
| | - Joby Josekutty
- From the School of Graduate Studies, Molecular and Cell Biology Program (M.T.W., J.J., J.S.), Department of Cell Biology (M.T.W., J.I., J.J., J.S., M.M.H.), Department of Pediatrics (M.M.H.), State University of New York Downstate Medical Center, Brooklyn, NY; Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy (E.D.L., P.T.); Infancy Services, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (E.O); Department of Nutrition and Metabolism, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (M.G.); and Department of Research, VA New York Harbor Healthcare System, Brooklyn, NY (M.M.H.)
| | - James Soh
- From the School of Graduate Studies, Molecular and Cell Biology Program (M.T.W., J.J., J.S.), Department of Cell Biology (M.T.W., J.I., J.J., J.S., M.M.H.), Department of Pediatrics (M.M.H.), State University of New York Downstate Medical Center, Brooklyn, NY; Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy (E.D.L., P.T.); Infancy Services, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (E.O); Department of Nutrition and Metabolism, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (M.G.); and Department of Research, VA New York Harbor Healthcare System, Brooklyn, NY (M.M.H.)
| | - Enza Di Leo
- From the School of Graduate Studies, Molecular and Cell Biology Program (M.T.W., J.J., J.S.), Department of Cell Biology (M.T.W., J.I., J.J., J.S., M.M.H.), Department of Pediatrics (M.M.H.), State University of New York Downstate Medical Center, Brooklyn, NY; Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy (E.D.L., P.T.); Infancy Services, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (E.O); Department of Nutrition and Metabolism, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (M.G.); and Department of Research, VA New York Harbor Healthcare System, Brooklyn, NY (M.M.H.)
| | - Eda Özaydin
- From the School of Graduate Studies, Molecular and Cell Biology Program (M.T.W., J.J., J.S.), Department of Cell Biology (M.T.W., J.I., J.J., J.S., M.M.H.), Department of Pediatrics (M.M.H.), State University of New York Downstate Medical Center, Brooklyn, NY; Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy (E.D.L., P.T.); Infancy Services, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (E.O); Department of Nutrition and Metabolism, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (M.G.); and Department of Research, VA New York Harbor Healthcare System, Brooklyn, NY (M.M.H.)
| | - Mehmet Gündüz
- From the School of Graduate Studies, Molecular and Cell Biology Program (M.T.W., J.J., J.S.), Department of Cell Biology (M.T.W., J.I., J.J., J.S., M.M.H.), Department of Pediatrics (M.M.H.), State University of New York Downstate Medical Center, Brooklyn, NY; Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy (E.D.L., P.T.); Infancy Services, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (E.O); Department of Nutrition and Metabolism, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (M.G.); and Department of Research, VA New York Harbor Healthcare System, Brooklyn, NY (M.M.H.)
| | - Patrizia Tarugi
- From the School of Graduate Studies, Molecular and Cell Biology Program (M.T.W., J.J., J.S.), Department of Cell Biology (M.T.W., J.I., J.J., J.S., M.M.H.), Department of Pediatrics (M.M.H.), State University of New York Downstate Medical Center, Brooklyn, NY; Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy (E.D.L., P.T.); Infancy Services, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (E.O); Department of Nutrition and Metabolism, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (M.G.); and Department of Research, VA New York Harbor Healthcare System, Brooklyn, NY (M.M.H.)
| | - M Mahmood Hussain
- From the School of Graduate Studies, Molecular and Cell Biology Program (M.T.W., J.J., J.S.), Department of Cell Biology (M.T.W., J.I., J.J., J.S., M.M.H.), Department of Pediatrics (M.M.H.), State University of New York Downstate Medical Center, Brooklyn, NY; Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy (E.D.L., P.T.); Infancy Services, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (E.O); Department of Nutrition and Metabolism, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (M.G.); and Department of Research, VA New York Harbor Healthcare System, Brooklyn, NY (M.M.H.).
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15
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Van der Horst DJ, Rodenburg KW. Lipoprotein assembly and function in an evolutionary perspective. Biomol Concepts 2015; 1:165-83. [PMID: 25961995 DOI: 10.1515/bmc.2010.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Circulatory fat transport in animals relies on members of the large lipid transfer protein (LLTP) superfamily, including mammalian apolipoprotein B (apoB) and insect apolipophorin II/I (apoLp-II/I). ApoB and apoLp-II/I, constituting the structural (non-exchangeable) basis for the assembly of various lipoproteins, acquire lipids through microsomal triglyceride-transfer protein, another LLTP family member, and bind them by means of amphipathic α-helical and β-sheet structural motifs. Comparative research reveals that LLTPs evolved from the earliest animals and highlights the structural adaptations in these lipid-binding proteins. Thus, in contrast to apoB, apoLp-II/I is cleaved post-translationally by a furin, resulting in the appearance of two non-exchangeable apolipoproteins in the single circulatory lipoprotein in insects, high-density lipophorin (HDLp). The remarkable structural similarities between mammalian and insect lipoproteins notwithstanding important functional differences relate to the mechanism of lipid delivery. Whereas in mammals, partial delipidation of apoB-containing lipoproteins eventually results in endocytic uptake of their remnants, mediated by members of the low-density lipoprotein receptor (LDLR) family, and degradation in lysosomes, insect HDLp functions as a reusable lipid shuttle capable of alternate unloading and reloading of lipid. Also, during muscular efforts (flight activity), an HDLp-based lipoprotein shuttle provides for the transport of lipid for energy generation. Although a lipophorin receptor - a homolog of LDLR - was identified that mediates endocytic uptake of HDLp during specific developmental periods, the endocytosed lipoprotein appears to be recycled in a transferrin-like manner. These data highlight that the functional adaptations in the lipoprotein lipid carriers in mammals and insects also emerge with regard to the functioning of their cognate receptors.
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16
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Molecular cloning, expression, and hormonal regulation of the chicken microsomal triglyceride transfer protein. Gene 2013; 523:1-9. [DOI: 10.1016/j.gene.2013.03.102] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Revised: 03/03/2013] [Accepted: 03/25/2013] [Indexed: 11/18/2022]
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17
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Soh J, Iqbal J, Queiroz J, Fernandez-Hernando C, Hussain MM. MicroRNA-30c reduces hyperlipidemia and atherosclerosis in mice by decreasing lipid synthesis and lipoprotein secretion. Nat Med 2013; 19:892-900. [PMID: 23749231 PMCID: PMC4121125 DOI: 10.1038/nm.3200] [Citation(s) in RCA: 225] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Accepted: 04/16/2013] [Indexed: 02/07/2023]
Abstract
Hyperlipidemia is a risk factor for various cardiovascular and metabolic disorders. Overproduction of lipoproteins, a process critically dependent on microsomal triglyceride transfer protein (MTP), can contribute to hyperlipidemia. We show that microRNA-30c (miR-30c) interacts with the 3′-untranslated region of the MTP mRNA and induces degradation leading to reductions in its activity and media apolipoprotein B. Further, miR-30c reduces hyperlipidemia and atherosclerosis in Western diet fed mice by decreasing lipid synthesis and secretion of triglyceride-rich apoB-containing lipoproteins. Therefore, miR-30c coordinately reduces lipid biosynthesis and lipoprotein secretion to control hepatic and plasma lipids and might be useful in treating hyperlipidemias and associated disorders.
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Affiliation(s)
- James Soh
- School of Graduate Studies, Molecular and Cell Biology Program, State University of New York Downstate Medical Center, Brooklyn, New York, USA
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18
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Khatun I, Walsh MT, Hussain MM. Loss of both phospholipid and triglyceride transfer activities of microsomal triglyceride transfer protein in abetalipoproteinemia. J Lipid Res 2013; 54:1541-1549. [PMID: 23475612 DOI: 10.1194/jlr.m031658] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mutations in microsomal triglyceride transfer protein (MTP) cause abetalipoproteinemia (ABL), characterized by the absence of plasma apoB-containing lipoproteins. In this study, we characterized the effects of various MTP missense mutations found in ABL patients with respect to their expression, subcellular location, and interaction with protein disulfide isomerase (PDI). In addition, we characterized functional properties by analyzing phospholipid and triglyceride transfer activities and studied their ability to support apoB secretion. All the mutants colocalized with calnexin and interacted with PDI. We found that R540H and N780Y, known to be deficient in triglyceride transfer activity, also lacked phospholipid transfer activity. Novel mutants S590I and G746E did not transfer triglycerides and phospholipids and did not assist in apoB secretion. In contrast, D384A displayed both triglyceride and phospholipid transfer activities and supported apoB secretion. These studies point out that ABL is associated with the absence of both triglyceride and phospholipid transfer activities in MTP.
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Affiliation(s)
- Irani Khatun
- Molecular and Cellular Biology Program, SUNY Downstate Medical Center, Brooklyn, NY; School of Graduate Studies, Department of Cell Biology, and SUNY Downstate Medical Center, Brooklyn, NY; Department of Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY
| | - Meghan T Walsh
- Molecular and Cellular Biology Program, SUNY Downstate Medical Center, Brooklyn, NY; School of Graduate Studies, Department of Cell Biology, and SUNY Downstate Medical Center, Brooklyn, NY; Department of Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY
| | - M Mahmood Hussain
- School of Graduate Studies, Department of Cell Biology, and SUNY Downstate Medical Center, Brooklyn, NY; Department of Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY.
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19
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Baer MM, Palm W, Eaton S, Leptin M, Affolter M. Microsomal triacylglycerol transfer protein (MTP) is required to expand tracheal lumen in Drosophila in a cell-autonomous manner. J Cell Sci 2012; 125:6038-48. [PMID: 23132924 DOI: 10.1242/jcs.110452] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The Drosophila tracheal system is a useful model for dissecting the molecular mechanisms controlling the assembly and expansion of tubular organs. We have identified microsomal triacylglycerol transfer protein (MTP) as a new player involved in the lumen expansion in unicellular tubes. MTP is an endoplasmic reticulum resident protein that can transfer triglycerides and phospholipids between membranes in vitro. MTP lipid transfer activity is crucial for the assembly and secretion of apoB family lipoproteins, which are carriers of lipids between different tissues. Here we describe an unexpected role of MTP in tracheal development, which we postulate to be independent of its known function in lipoprotein secretion. We propose that, in tracheal cells, MTP is involved in regulation of de novo apical membrane delivery to the existing lumen and thus promotes proper expansion of the larval tracheal system.
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Affiliation(s)
- Magdalena M Baer
- Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056, Basel, Switzerland
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20
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Avraham-Davidi I, Ely Y, Pham VN, Castranova D, Grunspan M, Malkinson G, Gibbs-Bar L, Mayseless O, Allmog G, Lo B, Warren CM, Chen TT, Ungos J, Kidd K, Shaw K, Rogachev I, Wan W, Murphy PM, Farber SA, Carmel L, Shelness GS, Iruela-Arispe ML, Weinstein BM, Yaniv K. ApoB-containing lipoproteins regulate angiogenesis by modulating expression of VEGF receptor 1. Nat Med 2012; 18:967-73. [PMID: 22581286 DOI: 10.1038/nm.2759] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Accepted: 04/02/2012] [Indexed: 12/15/2022]
Abstract
Despite the clear major contribution of hyperlipidemia to the prevalence of cardiovascular disease in the developed world, the direct effects of lipoproteins on endothelial cells have remained obscure and are under debate. Here we report a previously uncharacterized mechanism of vessel growth modulation by lipoprotein availability. Using a genetic screen for vascular defects in zebrafish, we initially identified a mutation, stalactite (stl), in the gene encoding microsomal triglyceride transfer protein (mtp), which is involved in the biosynthesis of apolipoprotein B (ApoB)-containing lipoproteins. By manipulating lipoprotein concentrations in zebrafish, we found that ApoB negatively regulates angiogenesis and that it is the ApoB protein particle, rather than lipid moieties within ApoB-containing lipoproteins, that is primarily responsible for this effect. Mechanistically, we identified downregulation of vascular endothelial growth factor receptor 1 (VEGFR1), which acts as a decoy receptor for VEGF, as a key mediator of the endothelial response to lipoproteins, and we observed VEGFR1 downregulation in hyperlipidemic mice. These findings may open new avenues for the treatment of lipoprotein-related vascular disorders.
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Affiliation(s)
- Inbal Avraham-Davidi
- Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel
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21
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Lipoproteins in Drosophila melanogaster--assembly, function, and influence on tissue lipid composition. PLoS Genet 2012; 8:e1002828. [PMID: 22844248 PMCID: PMC3406001 DOI: 10.1371/journal.pgen.1002828] [Citation(s) in RCA: 175] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2012] [Accepted: 05/25/2012] [Indexed: 11/19/2022] Open
Abstract
Interorgan lipid transport occurs via lipoproteins, and altered lipoprotein levels correlate with metabolic disease. However, precisely how lipoproteins affect tissue lipid composition has not been comprehensively analyzed. Here, we identify the major lipoproteins of Drosophila melanogaster and use genetics and mass spectrometry to study their assembly, interorgan trafficking, and influence on tissue lipids. The apoB-family lipoprotein Lipophorin (Lpp) is the major hemolymph lipid carrier. It is produced as a phospholipid-rich particle by the fat body, and its secretion requires Microsomal Triglyceride Transfer Protein (MTP). Lpp acquires sterols and most diacylglycerol (DAG) at the gut via Lipid Transfer Particle (LTP), another fat body-derived apoB-family lipoprotein. The gut, like the fat body, is a lipogenic organ, incorporating both de novo-synthesized and dietary fatty acids into DAG for export. We identify distinct requirements for LTP and Lpp-dependent lipid mobilization in contributing to the neutral and polar lipid composition of the brain and wing imaginal disc. These studies define major routes of interorgan lipid transport in Drosophila and uncover surprising tissue-specific differences in lipoprotein lipid utilization.
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22
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Khatun I, Zeissig S, Iqbal J, Wang M, Curiel D, Shelness GS, Blumberg RS, Hussain MM. Phospholipid transfer activity of microsomal triglyceride transfer protein produces apolipoprotein B and reduces hepatosteatosis while maintaining low plasma lipids in mice. Hepatology 2012; 55:1356-68. [PMID: 22121032 PMCID: PMC3299931 DOI: 10.1002/hep.25504] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Accepted: 11/13/2011] [Indexed: 12/12/2022]
Abstract
UNLABELLED Microsomal triglyceride transfer protein (MTP), essential for apolipoprotein B (apoB) biosynthesis, evolved as a phospholipid transfer protein and acquired triglyceride transfer activity during a transition from invertebrates to vertebrates. But it is unknown whether MTP directly transfers lipids onto apoB in vivo and, if it does, whether both neutral and polar lipid transfer activities of MTP are critical for lipoprotein assembly. The molecular bases for differences in lipid transfer activities with respect to distinct domains in Drosophila MTP (dMTP) and human MTP (hMTP) are not obvious because both proteins have very similar primary, secondary, and tertiary structures. We used an in vivo approach to delineate physiological significance of these distinct lipid transfer activities by expressing dMTP (transfers phospholipids) and hMTP (transfers phospholipids and triglycerides) orthologs using adenoviruses in liver-specific MTP-deficient (L-MTP(-/-)) mice that have low plasma and high hepatic lipids. Both orthologs improved plasma lipids but plasma triglycerides were lower in dMTP mice due to lower hepatic triglyceride and apoB production. Hepatosteatosis in L-MTP(-/-) mice was ameliorated to similar levels by both. Attenuation of hepatosteatosis upon dMTP expression pertained to enhanced β-oxidation with no changes in lipogenesis. Phospholipid transfer activity of MTP promoted biogenesis of both apoB48 and apoB100-containing very low density lipoprotein in addition to a phospholipid-rich apoB48-containing high-density lipoprotein particle. Triglyceride transfer activity augmented the biosynthesis of triglyceride-rich lipoproteins by increasing the formation of these particles in the lumen of the endoplasmic reticulum. CONCLUSION Based on these findings, we posit that the selective inhibition of MTP triglyceride transfer activity might reduce hyperlipidemia while protecting liver from excess lipid accumulation.
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Affiliation(s)
- Irani Khatun
- School of Graduate Studies, Molecular and Cellular Biology Program, Brooklyn, NY,Departments of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY
| | - Sebastian Zeissig
- Division of Gastroenterology, Hepatology, and Endoscopy, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA
| | - Jahangir Iqbal
- Departments of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY
| | - Minghui Wang
- University of Alabama, Birmingham, Winston-Salem, NC
| | - David Curiel
- University of Alabama, Birmingham, Winston-Salem, NC
| | | | - Richard S. Blumberg
- Division of Gastroenterology, Hepatology, and Endoscopy, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA
| | - M. Mahmood Hussain
- Departments of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY
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23
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Hussain MM, Rava P, Walsh M, Rana M, Iqbal J. Multiple functions of microsomal triglyceride transfer protein. Nutr Metab (Lond) 2012; 9:14. [PMID: 22353470 PMCID: PMC3337244 DOI: 10.1186/1743-7075-9-14] [Citation(s) in RCA: 175] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Accepted: 02/21/2012] [Indexed: 02/08/2023] Open
Abstract
Microsomal triglyceride transfer protein (MTP) was first identified as a major cellular protein capable of transferring neutral lipids between membrane vesicles. Its role as an essential chaperone for the biosynthesis of apolipoprotein B (apoB)-containing triglyceride-rich lipoproteins was established after the realization that abetalipoproteinemia patients carry mutations in the MTTP gene resulting in the loss of its lipid transfer activity. Now it is known that it also plays a role in the biosynthesis of CD1, glycolipid presenting molecules, as well as in the regulation of cholesterol ester biosynthesis. In this review, we will provide a historical perspective about the identification, purification and characterization of MTP, describe methods used to measure its lipid transfer activity, and discuss tissue expression and function. Finally, we will review the role MTP plays in the assembly of apoB-lipoprotein, the regulation of cholesterol ester synthesis, biosynthesis of CD1 proteins and propagation of hepatitis C virus. We will also provide a brief overview about the clinical potentials of MTP inhibition.
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Affiliation(s)
- M Mahmood Hussain
- Department of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
| | - Paul Rava
- Department of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
| | - Meghan Walsh
- Department of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
| | - Muhammad Rana
- Department of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
| | - Jahangir Iqbal
- Department of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
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24
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Tingaud-Sequeira A, Knoll-Gellida A, André M, Babin PJ. Vitellogenin Expression in White Adipose Tissue in Female Teleost Fish1. Biol Reprod 2012; 86:38. [DOI: 10.1095/biolreprod.111.093757] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
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25
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Weinberg RB, Gallagher JW, Fabritius MA, Shelness GS. ApoA-IV modulates the secretory trafficking of apoB and the size of triglyceride-rich lipoproteins. J Lipid Res 2012; 53:736-43. [PMID: 22257482 DOI: 10.1194/jlr.m019992] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Although the evidence linking apoA-IV expression and triglyceride (TG)-rich lipoprotein assembly and secretion is compelling, the intracellular mechanisms by which apoA-IV could modulate these processes remain poorly understood. We therefore examined the functional impact of apoA-IV expression on endogenous apoB, TG, and VLDL secretion in stably transfected McA-RH7777 rat hepatoma cells. Expression of apoA-IV modified with the endoplasmic reticulum (ER) retention signal KDEL (apoA-IV-KDEL) dramatically decreased both the rate and efficiency of endogenous apoB secretion, suggesting a presecretory interaction between apoA-IV-KDEL and apoB or apoB-containing lipoproteins. Expression of native apoA-IV using either a constitutive or tetracycline-inducible promoter delayed the initial rate of apoB secretion and reduced the final secretion efficiency by ∼40%. However, whereas apoA-IV-KDEL reduced TG secretion by 75%, expression of native apoA-IV caused a 20-35% increase in TG secretion, accompanied by a ∼55% increase in VLDL-associated apoB, an increase in the TG:phospholipid ratio of secreted d < 1.006 lipoproteins, and a 10.1 nm increase in peak VLDL(1) particle diameter. Native apoA-IV expression had a negligible impact on expression of the MTP gene. These data suggest that by interacting with apoB in the secretory pathway, apoA-IV alters the trafficking kinetics of apoB-containing TG-rich lipoproteins through cellular lipidation compartments, which in turn, enhances particle expansion and increases TG secretion.
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Affiliation(s)
- Richard B Weinberg
- Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA
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26
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Blade AM, Fabritius MA, Hou L, Weinberg RB, Shelness GS. Biogenesis of apolipoprotein A-V and its impact on VLDL triglyceride secretion. J Lipid Res 2011; 52:237-44. [PMID: 21115968 PMCID: PMC3023543 DOI: 10.1194/jlr.m010793] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Revised: 11/09/2010] [Indexed: 12/12/2022] Open
Abstract
Apolipoprotein A-V (apoA-V) is a potent regulator of intravascular triglyceride (TG) metabolism, yet its plasma concentration is very low compared with that of other apolipoproteins. To examine the basis for its low plasma concentration, the secretion efficiency of apoA-V was measured in stably transfected McA-RH7777 rat hepatoma cells. Pulse-chase experiments revealed that only ∼20% of newly synthesized apoA-V is secreted into culture medium within 3 h postsynthesis and that ∼65% undergoes presecretory turnover; similar results were obtained with transfected nonhepatic Chinese hamster ovary cells. ApoA-V secreted by McA-RH7777 cells was not associated with cell surface heparin-competable binding sites. When stably transfected McA-RH7777 cells were treated with oleic acid, the resulting increase in TG synthesis caused a reduction in apoA-V secretion, a reciprocal increase in cell-associated apoA-V, and movement of apoA-V onto cytosolic lipid droplets. In a stably transfected doxycycline-inducible McA-RH7777 cell line, apoA-V expression inhibited TG secretion by ∼50%, increased cellular TG, and reduced Z-average VLDL(1) particle diameter from 81 to 67 nm; however, no impact on apoB secretion was observed. These data demonstrate that apoA-V inefficiently traffics within the secretory pathway, that its intracellular itinerary can be regulated by changes in cellular TG accumulation, and that apoA-V synthesis can modulate VLDL TG mobilization and secretion.
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Affiliation(s)
- Anna M. Blade
- Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, NC 27157
| | - Melissa A. Fabritius
- Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, NC 27157
| | - Li Hou
- Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, NC 27157
| | - Richard B. Weinberg
- Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, NC 27157
- Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC 27157
| | - Gregory S. Shelness
- Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, NC 27157
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27
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Cheng D, MacArthur PS, Rong S, Parks JS, Shelness GS. Alternative splicing attenuates transgenic expression directed by the apolipoprotein E promoter-enhancer based expression vector pLIV11. J Lipid Res 2009; 51:849-55. [PMID: 19965599 DOI: 10.1194/jlr.d002709] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The plasmid vector pLIV11 is used commonly to achieve liver-specific expression of genes of interest in transgenic mice and rabbits. Expression is driven by the human apolipoprotein (apo)E 5' proximal promoter, which includes 5 kb of upstream sequence, exon 1, intron 1, and 5 bp of exon 2. A 3.8 kb 3' hepatic control region, derived from a region approximately 18 kb downstream of the apoE gene, enhances liver-specific expression. Here, we report that cDNA sequences inserted into the multiple cloning site (MCS) of pLIV11, which is positioned just downstream of truncated exon 2, can cause exon 2 skipping. Hence, splicing is displaced to downstream cryptic 3' splice acceptor sites causing deletion of cloned 5' untranslated mRNA sequences and, in some cases, deletion of the 5' end of an open reading frame. To prevent use of cryptic splice sites, the pLIV11 vector was modified with an engineered 3' splice acceptor site inserted immediately downstream of truncated apoE exon 2. Presence of this sequence fully shifted splicing of exon 1 from the native intron 1-exon 2 splice acceptor site to the engineered site. This finding confirmed that sequences inserted into the MCS of the vector pLIV11 can affect exon 2 recognition and provides a strategy to protect cloned sequences from alternative splicing and possible attenuation of transgenic expression.
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Affiliation(s)
- Dongmei Cheng
- Department of Pathology Section on Lipid Sciences, Wake Forest University School of Medicine, Winston Salem, NC 27157, USA
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28
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Van der Horst DJ, Roosendaal SD, Rodenburg KW. Circulatory lipid transport: lipoprotein assembly and function from an evolutionary perspective. Mol Cell Biochem 2009; 326:105-19. [PMID: 19130182 DOI: 10.1007/s11010-008-0011-3] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2007] [Accepted: 06/05/2008] [Indexed: 02/07/2023]
Abstract
Circulatory transport of neutral lipids (fat) in animals relies on members of the large lipid transfer protein (LLTP) superfamily, including mammalian apolipoprotein B (apoB) and insect apolipophorin II/I (apoLp-II/I). Latter proteins, which constitute the structural basis for the assembly of various lipoproteins, acquire lipids through microsomal triglyceride transfer protein (MTP)--another LLTP family member--and bind them by means of amphipathic structures. Comparative research reveals that LLTPs have evolved from the earliest animals and additionally highlights the structural and functional adaptations in these lipid carriers. For instance, in contrast to mammalian apoB, the insect apoB homologue, apoLp-II/I, is post-translationally cleaved by a furin, resulting in their appearance of two non-exchangeable apolipoproteins in the insect low-density lipoprotein (LDL) homologue, high-density lipophorin (HDLp). An important difference between mammalian and insect lipoproteins relates to the mechanism of lipid delivery. Whereas in mammals, endocytic uptake of lipoprotein particles, mediated via members of the LDL receptor (LDLR) family, results in their degradation in lysosomes, the insect HDLp was shown to act as a reusable lipid shuttle which is capable of reloading lipid. Although the recent identification of a lipophorin receptor (LpR), a homologue of LDLR, reveals that endocytic uptake of HDLp may constitute an additional mechanism of lipid delivery, the endocytosed lipoprotein appears to be recycled in a transferrin-like manner. Binding studies indicate that the HDLp-LpR complex, in contrast to the LDL-LDLR complex, is resistant to dissociation at endosomal pH as well as by treatment with EDTA mimicking the drop in Ca(2+) concentration in the endosome. This remarkable stability of the ligand-receptor complex may provide a crucial key to the recycling mechanism. Based on the binding and dissociation capacities of mutant and hybrid receptors, the specific binding interaction of the ligand-binding domain of the receptor with HDLp was characterized. These structural similarities and functional adaptations of the lipid transport systems operative in mammals and insects are discussed from an evolutionary perspective.
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Affiliation(s)
- Dick J Van der Horst
- Division of Endocrinology and Metabolism, Department of Biology and Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands.
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29
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Abstract
PURPOSE OF REVIEW Microsomal triglyceride transfer protein (MTP), a chaperone for the biosynthesis of apolipoprotein B lipoproteins and CD1d, is a therapeutic candidate to decrease plasma lipids and to diminish inflammation. MTP inhibition increases plasma transaminases and tissue lipids, and therefore new approaches are needed to avoid them. RECENT FINDINGS Inositol requiring enzyme1beta has been identified as a novel intestine-specific regulator of MTP. A new function of MTP in cholesterol ester biosynthesis has been reported. The importance of the phospholipid transfer activity of MTP in the lipidation of apolipoprotein B and CD1d has been indicated. Diurnal variations in MTP expression and its induction by food availability have been observed. On the basis of these and other findings, we propose that upregulation of inositol requiring enzyme 1beta, a combined reduction of cellular free cholesterol or triglyceride or both and MTP activity, specific inhibition of phospholipid or triglyceride transfer activities, and targeting of apolipoprotein B-MTP protein-protein interactions might be pursued to avoid some of the side effects associated with the inhibition of triglyceride transfer activity of MTP. We further speculate that short-lived MTP antagonists may be useful in controlling plasma and tissue lipids and in avoiding steatosis. SUMMARY We have highlighted the importance of addressing the causal relationship between MTP inhibition and aberrant elevations in plasma liver enzymes. The proposed approaches may show that MTP targeting is a viable approach to lower plasma lipids.
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Affiliation(s)
- Mohammed Mahmood Hussain
- Departments of Anatomy and Cell Biology, and Pediatrics, SUNY Downstate Medical Center, Brooklyn, New York 11203, USA.
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30
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Babin PJ, Gibbons GF. The evolution of plasma cholesterol: direct utility or a "spandrel" of hepatic lipid metabolism? Prog Lipid Res 2008; 48:73-91. [PMID: 19049814 DOI: 10.1016/j.plipres.2008.11.002] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2008] [Revised: 11/06/2008] [Accepted: 11/07/2008] [Indexed: 02/07/2023]
Abstract
Fats provide a concentrated source of energy for multicellular organisms. The efficient transport of fats through aqueous biological environments raises issues concerning effective delivery to target tissues. Furthermore, the utilization of fatty acids presents a high risk of cytotoxicity. Improving the efficiency of fat transport while simultaneously minimizing the cytotoxic risk confers distinct selective advantages. In humans, most of the plasma cholesterol is associated with low-density lipoprotein (LDL), a metabolic by-product of very-low-density lipoprotein (VLDL), which originates in the liver. However, the functions of VLDL are not clear. This paper reviews the evidence that LDL arose as a by-product during the natural selection of VLDL. The latter, in turn, evolved as a means of improving the efficiency of diet-derived fatty acid storage and utilization, as well as neutralizing the potential cytotoxicity of fatty acids while conserving their advantages as a concentrated energy source. The evolutionary biology of lipid transport processes has provided a fascinating insight into how and why these VLDL functions emerged during animal evolution. As causes of historical origin must be separated from current utilities, our spandrel-LDL theory proposes that LDL is a spandrel of VLDL selection, which appeared non-adaptively and may later have become crucial for vertebrate fitness.
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Affiliation(s)
- Patrick J Babin
- Université Bordeaux 1, Génomique et Physiologie des Poissons, UMR NuAGe, 33405 Talence, France
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31
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Serino JC, Almenara DP, Penha-Scarabotto C, de Moura JP, Winter CE. Vitellin-binding proteins in the nematode Oscheius tipulae (Nematoda, Rhabditida). Comp Biochem Physiol B Biochem Mol Biol 2008; 151:330-5. [PMID: 18725312 DOI: 10.1016/j.cbpb.2008.07.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2008] [Revised: 07/24/2008] [Accepted: 07/29/2008] [Indexed: 01/07/2023]
Abstract
We describe the first application of a non-radioactive ligand-blotting technique to the characterization of proteins interacting with nematode vitellins. Chromatographically purified vitellins from the free-living nematode Oscheius tipulae were labeled with fluorescein in vitro. Ligand-blotting assays with horseradish peroxidase-conjugated anti-fluorescein antibodies showed that labeled vitellins reacted specifically with a polypeptide of approximately 100 kDa, which we named P100. This polypeptide is a specific worm's vitellin-binding protein that is present only in adult worms. Blots containing purified O. tipulae vitellin preparations showed no detectable signal in the 100 kDa region, ruling out any possibility of yolk polypeptides self-assembling under the conditions used in our assay. Experiments done in the presence of alpha-methyl mannoside ruled out the possibility of vitellins binding to P100 through mannose residues. Triton X-114 fractionation of whole worm extracts showed that P100 is either a membrane protein or has highly hydrophobic regions.
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Affiliation(s)
- João Carlos Serino
- Department of Parasitology, Instituto de Ciências Biomédicas - Universidade de São Paulo, Av. Prof. Lineu Prestes, 1374, 05508-900 São Paulo - SP, Brazil
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Hussain MM, Rava P, Pan X, Dai K, Dougan SK, Iqbal J, Lazare F, Khatun I. Microsomal triglyceride transfer protein in plasma and cellular lipid metabolism. Curr Opin Lipidol 2008; 19:277-84. [PMID: 18460919 DOI: 10.1097/mol.0b013e3282feea85] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
PURPOSE OF REVIEW This review summarizes recent advances about the role of microsomal triglyceride transfer protein in plasma and tissue lipid homeostasis. RECENT FINDINGS Microsomal triglyceride transfer protein emerged as a phospholipid transfer protein and acquired triacylglycerol transfer activity during evolution from invertebrates to vertebrates. These activities are proposed to participate in 'nucleation' and 'desorption' steps during the biosynthesis of primordial apoB-containing lipoproteins. Microsomal triglyceride transfer protein also transfers phospholipids to the glycolipid antigen presentation molecule CD1d. Under physiologic conditions, plasma apoB-containing lipoproteins and microsomal triglyceride transfer protein expression exhibit diurnal variations synchronized by food and light. Microsomal triglyceride transfer protein is regulated at the transcriptional level. HNF4alpha is critical for its transcription. Other transcription factors along with coactivators and corepressors modulate microsomal triglyceride transfer protein expression. Reductions in microsomal triglyceride transfer protein mRNA and activity are related to steatosis in HCV-3 infected patients. CCl4 induces steatosis by enhancing proteasomal degradation of microsomal triglyceride transfer protein and can be partially avoided by inhibiting this degradation. Chemical antagonists cause hepatosteatosis, but this was not seen in the absence of fatty acid binding protein. SUMMARY Microsomal triglyceride transfer protein is a target to lower plasma lipids and to reduce inflammation in certain immune disorders. More knowledge is required, however, regarding its regulation and its role in the biosynthesis of apoB-containing lipoproteins and CD1d.
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Affiliation(s)
- M Mahmood Hussain
- Department of Anatomy and Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York 11203, USA.
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Iqbal J, Dai K, Seimon T, Jungreis R, Oyadomari M, Kuriakose G, Ron D, Tabas I, Hussain MM. IRE1beta inhibits chylomicron production by selectively degrading MTP mRNA. Cell Metab 2008; 7:445-55. [PMID: 18460335 PMCID: PMC2435513 DOI: 10.1016/j.cmet.2008.03.005] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2007] [Revised: 12/30/2007] [Accepted: 03/10/2008] [Indexed: 01/22/2023]
Abstract
Microsomal triglyceride transfer protein (MTP) is needed to assemble chylomicrons in the endoplasmic reticulum (ER) of enterocytes. We explored the role of an ER stress protein, inositol-requiring enzyme 1beta (IRE1beta), in regulating this process. High-cholesterol and high-fat diets decreased intestinal IRE1beta mRNA in wild-type mice. Ire1b(-/-) mice fed high-cholesterol and high-fat diets developed more pronounced hyperlipidemia because these mice secreted more chylomicrons and expressed more intestinal MTP, though not hepatic MTP, than wild-type mice did. Chylomicron secretion and MTP expression also were increased in primary enterocytes isolated from cholesterol-fed Ire1b(-/-) mice. There was no correlation between ER stress and MTP expression. Instead, cell culture studies revealed that IRE1beta, but not its ubiquitous homolog IRE1alpha, decreased MTP mRNA through increased posttranscriptional degradation. Conversely, knockdown of IRE1beta enhanced MTP expression. These studies show that IRE1beta plays a role in regulating MTP and in chylomicron production.
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Affiliation(s)
- Jahangir Iqbal
- Department of Anatomy and Cell Biology and Department of Pediatrics, The State University of New York Downstate Medical Center, Brooklyn, NY 11203, USA
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Schlegel A, Stainier DYR. Lessons from "lower" organisms: what worms, flies, and zebrafish can teach us about human energy metabolism. PLoS Genet 2008; 3:e199. [PMID: 18081423 PMCID: PMC2098794 DOI: 10.1371/journal.pgen.0030199] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
A pandemic of metabolic diseases (atherosclerosis, diabetes mellitus, and obesity), unleashed by multiple social and economic factors beyond the control of most individuals, threatens to diminish human life span for the first time in the modern era. Given the redundancy and inherent complexity of processes regulating the uptake, transport, catabolism, and synthesis of nutrients, magic bullets to target these diseases will be hard to find. Recent studies using the worm Caenorhabditis elegans, the fly Drosophila melanogaster, and the zebrafish Danio rerio indicate that these “lower” metazoans possess unique attributes that should help in identifying, investigating, and even validating new pharmaceutical targets for these diseases. We summarize findings in these organisms that shed light on highly conserved pathways of energy homeostasis.
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Affiliation(s)
- Amnon Schlegel
- Department of Biochemistry and Biophysics, Division of Endocrinology at the University of California San Francisco, San Francisco, California, United States of America.
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Rava P, Hussain MM. Acquisition of triacylglycerol transfer activity by microsomal triglyceride transfer protein during evolution. Biochemistry 2007; 46:12263-74. [PMID: 17924655 DOI: 10.1021/bi700762z] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Microsomal triglyceride transfer protein (MTP) is essential for the assembly of neutral-lipid-rich apolipoprotein B (apoB) lipoproteins. Previously we reported that the Drosophila MTP transfers phospholipids but does not transfer triglycerides. In contrast, human MTP transfers both lipids. To explore the acquisition of triglyceride transfer activity by MTP, we evaluated amino acid sequences, protein structures, and the biochemical and cellular properties of various MTP orthologues obtained from species that diverged during evolution. All MTP orthologues shared similar secondary and tertiary structures, associated with protein disulfide isomerase, localized to the endoplasmic reticulum, and supported apoB secretion. While vertebrate MTPs transferred triglyceride, invertebrate MTPs lacked this activity. Thus, triglyceride transfer activity was acquired during the transition from invertebrates to vertebrates. Within vertebrates, fish, amphibians, and birds displayed 27%, 40%, and 100% triglyceride transfer activity compared to mammals. We conclude that MTP triglyceride transfer activity first appeared in fish and speculate that the acquisition of triglyceride transfer activity by MTP provided for a significant advantage in the evolution of larger and more complex organisms.
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Affiliation(s)
- Paul Rava
- Molecular and Cellular Biology Program, School of Graduate Studies, SUNY Downstate Medical Center, Brooklyn, New York 11203, USA
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Xie Y, Luo J, Kennedy S, Davidson NO. Conditional intestinal lipotoxicity in Apobec-1-/- Mttp-IKO mice: a survival advantage for mammalian intestinal apolipoprotein B mRNA editing. J Biol Chem 2007; 282:33043-51. [PMID: 17855359 DOI: 10.1074/jbc.m705386200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Mammalian small intestinal lipid absorption requires the coordinated interactions of apolipoprotein B (apoB) and the microsomal triglyceride transfer protein (Mttp). The observation that apoB100 displays greater dependence on Mttp availability than does apoB48 prompted us to examine the phenotype of Mttp deletion in an Apobec-1(-/-) background (i.e. apoB100 Mttp-IKO). 20% apoB100 Mttp-IKO mice died on a chow diet, and >90% died following high fat feeding (versus 0 and 11% apoB48 Mttp-IKO mice, respectively). Intestinal adaptation occurred in apoB48 Mttp-IKO mice in response to high fat feeding, evidenced by increased bromodeoxyuridine incorporation and villus lengthening, changes that did not occur in apoB100 Mttp-IKO mice. There was an exaggerated unfolded protein response (UPR), which became more pronounced in apoB100 Mttp-IKO mice. To examine the role of endoplasmic reticulum stress and the UPR in the lipotoxic effects of Mttp deletion, we administered tauroursodeoxycholate to apoB100 Mttp-IKO mice upon initiation of high fat feeding. Tauroursodeoxycholate administration abrogated the UPR but produced an unexpected acceleration in the onset of lethality in apoB100 Mttp-IKO mice. The findings demonstrate that there is activation of the UPR with lethal lipotoxicity in conditional intestinal apoB100 Mttp-IKO mice. Together the data provide the first plausible biological evidence for a survival advantage for mammalian intestinal apoB mRNA editing.
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Affiliation(s)
- Yan Xie
- Department of Medicine, Washington University School of Medicine, 660 South Euclid, St. Louis, MO 63110, USA
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37
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Smolenaars MMW, de Morrée A, Kerver J, Van der Horst DJ, Rodenburg KW. Insect lipoprotein biogenesis depends on an amphipathic β cluster in apolipophorin II/I and is stimulated by microsomal triglyceride transfer protein. J Lipid Res 2007; 48:1955-65. [PMID: 17568063 DOI: 10.1194/jlr.m600434-jlr200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lipoproteins transport lipids in the circulation of an evolutionally wide diversity of animals. The pathway for lipoprotein biogenesis has been revealed to a large extent in mammals only, in which apolipoprotein B (apoB) acquires lipids via the assistance of microsomal triglyceride transfer protein (MTP) and binds them by means of amphipathic protein structures. To investigate whether this is a common mechanism for lipoprotein biogenesis in animals, we studied the structural elements involved in the assembly of the insect lipoprotein, lipophorin. LOCATE sequence analysis predicted that the insect lipoprotein precursor, apolipophorin II/I (apoLp-II/I), contains clusters of amphipathic alpha-helices and beta-strands, organized along the protein as N-alpha(1)-beta-alpha(2)-C, reminiscent of a truncated form of apoB. Recombinant expression of a series of C-terminal truncation variants of Locusta migratoria apoLp-II/I in an insect cell (Sf9) expression system revealed that the formation of a buoyant high density lipoprotein requires the amphipathic beta cluster. Coexpression of apoLp-II/I with the MTP homolog of Drosophila melanogaster affected insect lipoprotein biogenesis quantitatively as well as qualitatively, as the secretion of apoLp-II/I proteins was increased several-fold and the buoyant density of the secreted lipoprotein decreased concomitantly, indicative of augmented lipidation. Based on these findings, we propose that, despite specific modifications, the assembly of lipoproteins involves MTP as well as amphipathic structures in the apolipoprotein carrier, both in mammals and insects. Thus, lipoprotein biogenesis in animals appears to rely on structural elements that are of early metazoan origin.
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Affiliation(s)
- Marcel M W Smolenaars
- Division of Endocrinology and Metabolism, Department of Biology and Institute of Biomembranes, Utrecht University, Utrecht, The Netherlands
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Temel RE, Hou L, Rudel LL, Shelness GS. ACAT2 stimulates cholesteryl ester secretion in apoB-containing lipoproteins. J Lipid Res 2007; 48:1618-27. [PMID: 17438337 DOI: 10.1194/jlr.m700109-jlr200] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previous studies in nonhuman primates revealed a striking positive correlation between liver cholesteryl ester (CE) secretion rate and the development of coronary artery atherosclerosis. CE incorporated into hepatic VLDL is necessarily synthesized by ACAT2, the cholesterol-esterifying enzyme in hepatocytes. We tested the hypothesis that the level of ACAT2 expression, in concert with cellular cholesterol availability, affects the CE content of apolipoprotein B (apoB)-containing lipoproteins. In a model system of lipoprotein secretion using COS cells cotransfected with microsomal triglyceride transfer protein and truncated forms of apoB, ACAT2 expression resulted in a 3-fold increase in microsomal ACAT activity and a 4-fold increase in the radiolabeled CE content of apoB-lipoproteins. After cholesterol-cyclodextrin (Chol-CD) treatment, CE secretion was increased by 27-fold in ACAT2-transfected cells but by only 7-fold in control cells. Chol-CD treatment also caused the percentage of CE in the apoB-lipoproteins to increase from 3% to 33% in control cells and from 16% to 54% in ACAT2-transfected cells. In addition, ACAT2-transfected cells secreted 3-fold more apoB than control cells. These results indicate that under all conditions of cellular cholesterol availability tested, the relative level of ACAT2 expression affects the CE content and, hence, the potential atherogenicity, of nascent apoB-containing lipoproteins.
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Affiliation(s)
- Ryan E Temel
- Department of Pathology, Section on Lipid Sciences, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
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Avarre JC, Lubzens E, Babin PJ. Apolipocrustacein, formerly vitellogenin, is the major egg yolk precursor protein in decapod crustaceans and is homologous to insect apolipophorin II/I and vertebrate apolipoprotein B. BMC Evol Biol 2007; 7:3. [PMID: 17241455 PMCID: PMC1783640 DOI: 10.1186/1471-2148-7-3] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2006] [Accepted: 01/22/2007] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In animals, the biogenesis of some lipoprotein classes requires members of the ancient large lipid transfer protein (LLTP) superfamily, including the cytosolic large subunit of microsomal triglyceride transfer protein (MTP), vertebrate apolipoprotein B (apoB), vitellogenin (Vtg), and insect apolipophorin II/I precursor (apoLp-II/I). In most oviparous species, Vtg, a large glycolipoprotein, is the main egg yolk precursor protein. RESULTS This report clarifies the phylogenetic relationships of LLTP superfamily members and classifies them into three families and their related subfamilies. This means that the generic term Vtg is no longer a functional term, but is rather based on phylogenetic/structural criteria. In addition, we determined that the main egg yolk precursor protein of decapod crustaceans show an overall greater sequence similarity with apoLp-II/I than other LLTP, including Vtgs. This close association is supported by the phylogenetic analysis, i.e. neighbor-joining, maximum likelihood and Bayesian inference methods, of conserved sequence motifs and the presence of three common conserved domains: an N-terminal large lipid transfer module marker for LLTP, a DUF1081 domain of unknown function in their central region exclusively shared with apoLp-II/I and apoB, and a von Willebrand-factor type D domain at their C-terminal end. Additionally, they share a conserved functional subtilisin-like endoprotease cleavage site with apoLp-II/I, in a similar location. CONCLUSION The structural and phylogenetic data presented indicate that the major egg yolk precursor protein of decapod crustaceans is surprisingly closely related to insect apoLp-II/I and vertebrate apoB and should be known as apolipocrustacein (apoCr) rather than Vtg. These LLTP may arise from an ancient duplication event leading to paralogs of Vtg sequences. The presence of LLTP homologs in one genome may facilitate redundancy, e.g. involvement in lipid metabolism and as egg yolk precursor protein, and neofunctionalization and subfunctionalization, e.g. involvement in clotting cascade and immune response, of extracellular LLTP members. These protein-coding nuclear genes may be used to resolve phylogenetic relationships among the major arthropod groups, especially the Pancrustacea-major splits.
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Affiliation(s)
- Jean-Christophe Avarre
- Israel Oceanographic and Limnological Research, P.O. Box 8030, Haifa 31080, Israel
- Genewave XTEC, Ecole Polytechnique, 91128 Palaiseau, France
| | - Esther Lubzens
- Israel Oceanographic and Limnological Research, P.O. Box 8030, Haifa 31080, Israel
| | - Patrick J Babin
- Génomique et Physiologie des Poissons, Université Bordeaux 1, UMR NuAGe, 33405 Talence cedex, France
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Schlegel A, Stainier DYR. Microsomal triglyceride transfer protein is required for yolk lipid utilization and absorption of dietary lipids in zebrafish larvae. Biochemistry 2006; 45:15179-87. [PMID: 17176039 DOI: 10.1021/bi0619268] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Although the absorption, transport, and catabolism of dietary lipids have been studied extensively in great detail in mammals and other vertebrates, a tractable genetic system for identifying novel genes involved in these physiologic processes is not available. To establish such a model, we monitored neutral lipid by staining fixed zebrafish larvae with oil red o (ORO). The head structures, heart, vasculature, and swim bladder stained with ORO until the yolk was consumed 6 days after fertilization (6 dpf). Thereafter, the heart and vasculature no longer had stainable neutral lipids. Following a high-fat meal, ORO stained the intestine and vasculature of 6 dpf larvae, and whole-larval triacylglycerol (TAG) and apolipoprotein B levels increased. Levels of microsomal triglyceride transfer protein (Mtp), the protein responsible for packaging TAG and betalipoproteins into lipoprotein particles, were unchanged by feeding. Since the developing zebrafish embryo expresses mtp in the yolk cell layer, liver, and intestine, we determined the effect of targeted knockdown of Mtp expression using an antisense morpholino oligonucleotide approach (Mtp MO) on the transport of yolk and dietary lipids. Mtp MO injection led to loss of Mtp expression and of lipid staining in the vasculature, heart, and head structures. Mtp MO-injected larvae were smaller than age-matched, uninjected larvae, consumed very little yolk, and did not absorb dietary neutral lipids; however, they absorbed a short chain fatty acid that does not require Mtp for transport. Importantly, the vasculature appeared unaffected in Mtp MO-injected larvae. These studies indicate that zebrafish larvae are suitable for genetic studies of lipid transport and metabolism.
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Affiliation(s)
- Amnon Schlegel
- Department of Biochemistry and Biophysics, University of California, MC-2711, 1550 Fourth Street, Room 381, San Francisco, California 94143, USA.
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Rava P, Ojakian GK, Shelness GS, Hussain MM. Phospholipid Transfer Activity of Microsomal Triacylglycerol Transfer Protein Is Sufficient for the Assembly and Secretion of Apolipoprotein B Lipoproteins. J Biol Chem 2006; 281:11019-27. [PMID: 16478722 DOI: 10.1074/jbc.m512823200] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human microsomal triacylglycerol transfer protein (hMTP) is essential for apolipoprotein B (apoB)-lipoprotein assembly and secretion and is known to transfer triacylglycerols, cholesterol esters, and phospholipids. To understand the relative importance of each lipid transfer activity, we compared the ability of hMTP and its Drosophila ortholog (dMTP) to assemble apoB lipoproteins and to transfer various lipids. apoB48 secretion was induced when co-expressed with either hMTP or dMTP in COS cells, and oleic acid supplementation further augmented secretion without altering particle density. C-terminal epitope-tagged dMTP (dMTP-FLAG) facilitated the secretion of apoB polypeptides in the range of apoB48 to apoB72 but was approximately 50% as efficient as hMTP-FLAG. Comparison of lipid transfer activities revealed that although phospholipid transfer was similar in both orthologs, dMTP was unable to transfer neutral lipids. We conclude that the phospholipid transfer activity of MTP is sufficient for the assembly and secretion of primordial apoB lipoproteins and may represent its earliest function evolved for the mobilization of lipid in invertebrates. Identification of MTP inhibitors, which selectively affect transfer of a specific lipid class, may have therapeutic potential.
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Affiliation(s)
- Paul Rava
- Department of Anatomy and Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York 11203, USA
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Marza E, Barthe C, André M, Villeneuve L, Hélou C, Babin PJ. Developmental expression and nutritional regulation of a zebrafish gene homologous to mammalian microsomal triglyceride transfer protein large subunit. Dev Dyn 2005; 232:506-18. [PMID: 15614773 DOI: 10.1002/dvdy.20251] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The microsomal triglyceride transfer protein (MTP) large subunit is required for the assembly and secretion of apolipoprotein B-containing lipoproteins. We have found a zebrafish mtp homologous gene coding a protein with 54% identity with human MTP large subunit with the most conserved regions distributed in the corresponding predicted alpha-helical and C- and A-sheet domains. In situ hybridizations showed that zebrafish mtp transcripts were distributed in the yolk syncytial layer during early embryogenesis and in anterior intestine and liver from 48 hr postfertilization onward. Real-time quantitative RT-PCR confirmed the developmental regulation and tissue-specificity of mtp expression. A significant pretranslational up-regulation of mtp expression was observed in the anterior intestine after feeding. The nutritional regulation of zebrafish mtp expression observed in the anterior intestine supports the notion that this protein, similar to mammalian MTP large subunit, could be a factor implicated directly or indirectly in large lipid droplets accumulation observed in the fish enterocyte after feeding.
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Affiliation(s)
- Esther Marza
- Laboratoire Génomique et Physiologie des Poissons, UMR 1067 NUAGE INRA-IFREMER, Université Bordeaux 1, 33405 Talence Cedex, France
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Abstract
PURPOSE OF REVIEW Apolipoprotein B-containing lipoprotein assembly and secretion is critical for lipid absorption and triglyceride homeostasis, and plays a role in atherogenesis and the pathobiology of type 2 diabetes and obesity. This review highlights recent insights into the evolutionary, structural, and cell biology of hepatic and intestinal pathways for lipid mobilization, and the mechanisms and regulation of lipoprotein assembly and secretion. RECENT FINDINGS Until recently it was assumed that microsomal triglyceride transfer protein-dependent apolipoprotein B-containing lipoprotein assembly was a unique adaptation associated with vertebrate lipid homeostasis. However, it is now clear that microsomal triglyceride transfer protein (MTP) exists in species whose last common ancestor diverged over 550 million years ago. In its long evolutionary history, the MTP gene has given rise to a series of paralogous lipid transport proteins, all of which require MTP for their biogenesis. During its evolution, MTP has acquired new functions, enabling it to participate in a disparate array of lipid mobilization and transport pathways, ranging from primitive lipoprotein assembly to antigenic lipid presentation. In addition to the complex and multifunctional role of MTP in apolipoprotein B assembly, other factors responsible for the generation of secretion-coupled lipids and the modulation of apolipoprotein B production are emerging. SUMMARY The phylogenic dissection of MTP and apolipoprotein B function, coupled with ongoing structural and biochemical analyses, provide significant insights into the mechanisms of lipid mobilization and secretion. Some of these factors and processes may be targeted therapeutically to modulate the quantitative and qualitative aspects of apolipoprotein B production.
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Affiliation(s)
- Gregory S Shelness
- Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157-1040, USA
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Smolenaars MMW, Kasperaitis MAM, Richardson PE, Rodenburg KW, Van der Horst DJ. Biosynthesis and secretion of insect lipoprotein: involvement of furin in cleavage of the apoB homolog, apolipophorin-II/I. J Lipid Res 2005; 46:412-21. [PMID: 15604521 DOI: 10.1194/jlr.m400374-jlr200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The biosynthesis of neutral fat-transporting lipoproteins involves the lipidation of their nonexchangeable apolipoprotein. In contrast to its mammalian homolog apolipoprotein B, however, insect apolipophorin-II/I (apoLp-II/I) is cleaved posttranslationally at a consensus substrate sequence for furin, resulting in the appearance of two apolipoproteins in insect lipoprotein. To characterize the cleavage process, a truncated cDNA encoding the N-terminal 38% of Locusta migratoria apoLp-II/I, including the cleavage site, was expressed in insect Sf9 cells. This resulted in the secretion of correctly processed apoLp-II and truncated apoLp-I. The cleavage could be impaired by the furin inhibitor decanoyl-Arg-Val-Lys-Arg-chloromethyl ketone (decRVKRcmk) as well as by mutagenesis of the consensus substrate sequence for furin, as indicated by the secretion of uncleaved apoLp-II/I-38. Treatment of L. migratoria fat body, the physiological site of lipoprotein biosynthesis, with decRVKRcmk similarly resulted in the secretion of uncleaved apoLp-II/I, which was integrated in lipoprotein particles of buoyant density identical to wild-type high density lipophorin (HDLp). These results show that apoLp-II/I is posttranslationally cleaved by an insect furin and that biosynthesis and secretion of HDLp can occur independent of this processing step. Structure modeling indicates that the cleavage of apoLp-II/I represents a molecular adaptation in homologous apolipoprotein structures. We propose that cleavage enables specific features of insect lipoproteins, such as low density lipoprotein formation, endocytic recycling, and involvement in coagulation.
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Affiliation(s)
- Marcel M W Smolenaars
- Department of Biochemical Physiology, Faculty of Biology, Institute of Biomembranes, Utrecht University, Utrecht, The Netherlands
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Sellers JA, Hou L, Schoenberg DR, Batistuzzo de Medeiros SR, Wahli W, Shelness GS. Microsomal triglyceride transfer protein promotes the secretion of Xenopus laevis vitellogenin A1. J Biol Chem 2005; 280:13902-5. [PMID: 15701598 DOI: 10.1074/jbc.m500769200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vitellogenins (Vtg) are ancient lipid transport and storage proteins and members of the large lipid transfer protein (LLTP) gene family, which includes insect apolipophorin II/I, apolipoprotein B (apoB), and the microsomal triglyceride transfer protein (MTP). Lipidation of Vtg occurs at its site of synthesis in vertebrate liver, insect fat body, and nematode intestine; however, the mechanism of Vtg lipid acquisition is unknown. To explore whether Vtg biogenesis requires the apoB cofactor and LLTP family member, MTP, Vtg was expressed in COS cells with and without coexpression of the 97-kDa subunit of human MTP. Expression of Vtg alone gave rise to a approximately 220-kDa apoprotein, which was predominantly confined to an intracellular location. Coexpression of Vtg with human MTP enhanced Vtg secretion by 5-fold, without dramatically affecting its intracellular stability. A comparison of wild type and a triglyceride transfer-defective form of MTP revealed that both were capable of promoting Vtg secretion, whereas only wild type MTP could promote the secretion of apoB41 (amino-terminal 41% of apoB). These studies demonstrate that the biogenesis of Vtg is MTP-dependent and that MTP is the likely ancestral member of the LLTP gene family.
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Affiliation(s)
- Jeremy A Sellers
- Department of Pathology, Wake Forest University School of Medicine Winston-Salem, North Carolina 27157-1040, USA
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46
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Brandt BW, Zwaan BJ, Beekman M, Westendorp RGJ, Slagboom PE. Shuttling between species for pathways of lifespan regulation: A central role for the vitellogenin gene family? Bioessays 2005; 27:339-46. [PMID: 15714554 DOI: 10.1002/bies.20161] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Studies to find genes that affect maximum lifespan aim at identifying important determinants of ageing that may be universal across species. Model organisms show insulin signalling can play an important role in ageing. In view of insulin resistance, such loci can also be important in human ageing and health. The study of long-lived humans and their children points to the relevance of lipoprotein profiles and particle size for longevity. If ageing pathways are conserved, then the genes mediating such pathways may also be conserved. Cross-species sequence comparisons of potential longevity loci may reveal whether the pathways that they represent are central themes in lifespan regulation. Using bioinformatic tools, we performed a sequence comparison of the genes involved in lipid metabolism identified in humans as potential longevity loci. This analysis revealed that lipid storage and transport may be a common theme related to longevity in humans, honeybees and nematodes. Here, the vitellogenin family emerges as a potential key connection between lipid metabolism and the insulin/IGF-1 signalling pathway.
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Affiliation(s)
- Bernd W Brandt
- Section of Molecular Epidemiology, Department of Medical Statistics and Bioinformatics, Leiden University Medical Center, The Netherlands.
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Gallagher JW, Weinberg RB, Shelness GS. apoA-IV tagged with the ER retention signal KDEL perturbs the intracellular trafficking and secretion of apoB. J Lipid Res 2004; 45:1826-34. [PMID: 15258202 DOI: 10.1194/jlr.m400188-jlr200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To examine the role of apolipoprotein A-IV (apoA-IV) in the intracellular trafficking and secretion of apoB, COS cells were cotransfected with microsomal triglyceride transfer protein (MTP), apoB-41 (amino terminal 41% of apoB), and either native apoA-IV or apoA-IV modified with the carboxy-terminal endoplasmic reticulum (ER) retention signal, KDEL (apoA-IV-KDEL). As expected, apoA-IV-KDEL was inefficiently secreted relative to native apoA-IV. Coexpression of apoB-41 with apoA-IV-KDEL reduced the secretion of apoB-41 by approximately 80%. The apoA-IV-KDEL effect was specific, as neither KDEL-modified forms of human serum albumin or apoA-I affected apoB-41 secretion. Similar results were observed in McA-RH7777 rat hepatoma cells, which express endogenous MTP. The full inhibitory effect of apoA-IV-KDEL on apoB secretion was observed only for forms of apoB containing a minimum of the amino-terminal 25% of the protein (apoB-25). However, apoA-IV-KDEL inhibited the secretion of both lipid-associated and lipid-poor forms of apoB-25. Dual-label immunofluorescence microscopy of cells transfected with native apoA-IV and apoB-25 revealed that both apolipoproteins were localized to the ER and Golgi, as expected. However, when apoA-IV-KDEL was cotransfected with apoB-25, both proteins localized primarily to the ER. These data suggest that apoA-IV may physically interact with apoB in the secretory pathway, perhaps reflecting a role in modulating the process of triglyceride-rich lipoprotein assembly and secretion.
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Affiliation(s)
- James W Gallagher
- Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
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Ikonen E. Genetics and molecular biology. Curr Opin Lipidol 2004; 15:219-21. [PMID: 15017366 DOI: 10.1097/00041433-200404000-00016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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