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Girotti AW, Korytowski W. Trafficking of oxidative stress-generated lipid hydroperoxides: pathophysiological implications. Free Radic Res 2023; 57:130-139. [PMID: 37171212 PMCID: PMC10405667 DOI: 10.1080/10715762.2023.2213817] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 04/26/2023] [Accepted: 05/05/2023] [Indexed: 05/13/2023]
Abstract
Lipid hydroperoxides (LOOHs) are reactive intermediates that arise during peroxidation of unsaturated phospholipids, glycolipids and cholesterol in biological membranes and lipoproteins. Non-physiological lipid peroxidation (LPO) typically occurs under oxidative stress conditions associated with pathologies such as atherogenesis, neurodegeneration, and carcinogenesis. As key intermediates in the LPO process, LOOHs are susceptible to one-electron versus two-electron reductive turnover, the former exacerbating membrane or lipoprotein damage/dysfunction and the latter diminishing it. A third possible LOOH fate is translocation to an acceptor membrane/lipoprotein, where one- or two-electron reduction may then ensue. In the case of cholesterol (Ch)-derived hydroperoxides (ChOOHs), translocation can be specifically stimulated by StAR family trafficking proteins, which are normally involved in Ch homeostasis and Ch-mediated steroidogenesis. In this review, we discuss how these processes can be impaired by StAR-mediated ChOOH and Ch co-trafficking to mitochondria of vascular macrophages and steroidogenic cells, respectively. The protective effects of endogenous selenoperoxidase, GPx4, are also discussed. This is the first known example of detrimental ChOOH transfer via a natural Ch trafficking pathway and inhibition thereof by GPx4.
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Affiliation(s)
- Albert W. Girotti
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI, USA
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2
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Girotti AW, Korytowski W. Pathophysiological potential of lipid hydroperoxide intermembrane translocation: Cholesterol hydroperoxide translocation as a special case. Redox Biol 2021; 46:102096. [PMID: 34418596 PMCID: PMC8379493 DOI: 10.1016/j.redox.2021.102096] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 08/04/2021] [Accepted: 08/05/2021] [Indexed: 10/29/2022] Open
Abstract
Peroxidation of unsaturated phospholipids, glycolipids, and cholesterol in biological membranes under oxidative stress conditions can underlie a variety of pathological conditions, including atherogenesis, neurodegeneration, and carcinogenesis. Lipid hydroperoxides (LOOHs) are key intermediates in the peroxidative process. Nascent LOOHs may either undergo one-electron reduction to exacerbate membrane damage/dysfunction or two-electron reduction to attenuate this. Another possibility is LOOH translocation to an acceptor site, followed by either of these competing reductions. Cholesterol (Ch)-derived hydroperoxides (ChOOHs) have several special features that will be highlighted in this review. In addition to being susceptible to one-electron vs. two-electron reduction, ChOOHs can translocate from a membrane of origin to another membrane, where such turnover may ensue. Intracellular StAR family proteins have been shown to deliver not only Ch to mitochondria, but also ChOOHs. StAR-mediated transfer of free radical-generated 7-hydroperoxycholesterol (7-OOH) results in impairment of (a) Ch utilization in steroidogenic cells, and (b) anti-atherogenic reverse Ch transport in vascular macrophages. This is the first known example of how a peroxide derivative can be recognized by a natural lipid trafficking pathway with deleterious consequences. For each example above, we will discuss the underlying mechanism of oxidative damage/dysfunction, and how this might be mitigated by antioxidant intervention.
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Affiliation(s)
- Albert W Girotti
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI, USA.
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3
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Langsted A, Jensen AMR, Varbo A, Nordestgaard BG. Low High-Density Lipoprotein Cholesterol to Monitor Long-Term Average Increased Triglycerides. J Clin Endocrinol Metab 2020; 105:5673158. [PMID: 31822888 DOI: 10.1210/clinem/dgz265] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Accepted: 12/10/2019] [Indexed: 02/13/2023]
Abstract
CONTEXT Increased triglyceride-rich remnants represent a causal risk factor for ischemic cardiovascular disease. OBJECTIVE We tested the hypothesis that low high-density lipoprotein (HDL) cholesterol can be used to monitor long-term high triglycerides/remnant cholesterol, just as high hemoglobin A1c (HbA1c) can be used to monitor long-term high glucose levels. DESIGN, SETTING, PARTICIPANTS, AND INTERVENTIONS We studied cross-sectionally 108 731 individuals, dynamically 1313 individuals with lipid measurement at 10 repeated visits, short-term 305 individuals during a fat load, and long-term 10 479 individuals with 2 lipid measurements 10 years apart. MAIN OUTCOME MEASURES Levels of HDL cholesterol and triglycerides. RESULTS Cross-sectionally, HDL cholesterol was inversely associated with triglycerides (R2 = 0.26) and remnant cholesterol (R2 = 0.26). Dynamically, major changes in triglyceride levels from measurement to measurement were mimicked by corresponding modest changes in HDL cholesterol. In the short-term after a fat load, median triglycerides increased 96% while HDL cholesterol decreased only 1%. Long-term, in individuals with measurements 10 years apart, those who initially had the highest triglycerides and corresponding lowest HDL cholesterol, still had highest triglycerides and lowest HDL cholesterol 10 years later. Prospectively, individuals with increased triglycerides/remnant cholesterol had increased risk of myocardial infarction; however, when the HDL cholesterol monitoring was removed, increased triglycerides/remnant cholesterol were largely no longer associated with increased risk of myocardial infarction. CONCLUSIONS Low HDL cholesterol is a stable marker of average high triglycerides/remnant cholesterol. This suggests that low HDL cholesterol can be used to monitor long-term average high triglycerides and remnant cholesterol, analogous to high HbA1c as a long-term monitor of average high glucose levels.
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Affiliation(s)
- Anne Langsted
- Department of Clinical Biochemistry and the Copenhagen General Population Study, Herlev and Gentofte Hospital, Copenhagen University Hospital, Herlev, Denmark
- Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Anne Marie Reimer Jensen
- Department of Clinical Biochemistry and the Copenhagen General Population Study, Herlev and Gentofte Hospital, Copenhagen University Hospital, Herlev, Denmark
- Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Anette Varbo
- Department of Clinical Biochemistry and the Copenhagen General Population Study, Herlev and Gentofte Hospital, Copenhagen University Hospital, Herlev, Denmark
- Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Børge G Nordestgaard
- Department of Clinical Biochemistry and the Copenhagen General Population Study, Herlev and Gentofte Hospital, Copenhagen University Hospital, Herlev, Denmark
- Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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4
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He H, Wang J, Yannie PJ, Kakiyama G, Korzun WJ, Ghosh S. Sterol carrier protein-2 deficiency attenuates diet-induced dyslipidemia and atherosclerosis in mice. J Biol Chem 2018; 293:9223-9231. [PMID: 29700117 DOI: 10.1074/jbc.ra118.002290] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Revised: 04/25/2018] [Indexed: 01/05/2023] Open
Abstract
Intracellular cholesterol transport proteins move cholesterol to different subcellular compartments and thereby regulate its final metabolic fate. In hepatocytes, for example, delivery of high-density lipoprotein (HDL)-associated cholesterol for bile acid synthesis or secretion into bile facilitates cholesterol elimination from the body (anti-atherogenic effect), whereas delivery for esterification and subsequent incorporation into apolipoprotein B-containing atherogenic lipoproteins (e.g. very-low-density lipoprotein (VLDL)) enhances cholesterol secretion into the systemic circulation (pro-atherogenic effect). Intracellular cholesterol transport proteins such as sterol carrier protein-2 (SCP2) should, therefore, play a role in regulating these pro- or anti-atherosclerotic processes. Here, we sought to evaluate the effects of SCP2 deficiency on the development of diet-induced atherosclerosis. We generated LDLR-/- mice deficient in SCP2/SCPx (LS) and examined the effects of this deficiency on Western diet-induced atherosclerosis. SCP2/SCPx deficiency attenuated atherosclerosis in LS mice by >80% and significantly reduced plasma cholesterol and triglyceride levels. Investigation of the likely underlying mechanisms revealed a significant reduction in intestinal cholesterol absorption (given as an oral gavage) in SCP2/SCPx-deficient mice. Consistently, siRNA-mediated knockdown of SCP2 in intestinal cells significantly reduced cholesterol uptake. Furthermore, hepatic triglyceride/VLDL secretion from the liver or hepatocytes isolated from SCP2/SCPx-deficient mice was significantly reduced. These results indicate an important regulatory role for SCP2 deficiency in attenuating diet-induced atherosclerosis by limiting intestinal cholesterol absorption and decreasing hepatic triglyceride/VLDL secretion. These findings suggest targeted inhibition of SCP2 as a potential therapeutic strategy to reduce Western diet-induced dyslipidemia and atherosclerosis.
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Affiliation(s)
| | - Jing Wang
- From the Departments of Internal Medicine and
| | - Paul J Yannie
- the Hunter Homes McGuire Veterans Affairs Medical Center, Richmond, Virginia 23249
| | - Genta Kakiyama
- the Hunter Homes McGuire Veterans Affairs Medical Center, Richmond, Virginia 23249
| | - William J Korzun
- Clinical and Laboratory Sciences, Virginia Commonwealth University (VCU) Medical Center, Richmond, Virginia 23298 and
| | - Shobha Ghosh
- From the Departments of Internal Medicine and .,the Hunter Homes McGuire Veterans Affairs Medical Center, Richmond, Virginia 23249
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5
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Peyret A, Zhao H, Lecommandoux S. Preparation and Properties of Asymmetric Synthetic Membranes Based on Lipid and Polymer Self-Assembly. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:3376-3385. [PMID: 29486556 DOI: 10.1021/acs.langmuir.7b04233] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Cell membrane asymmetry is a common structural feature of all biological cells. Researchers have tried for decades to better study its formation and its function in membrane-regulated phenomena. In particular, there has been increasing interest in developing synthetic asymmetric membrane models in the laboratory, with the aim of studying basic physical chemistry properties that may be correlated to a relevant biological function. The present article aims to summarize the main presented approaches to prepare asymmetric membranes, which are most often made from lipids, polymers, or a combination of both.
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Affiliation(s)
- Ariane Peyret
- Laboratoire de Chimie des Polymères Organiques, LCPO, Université de Bordeaux, CNRS, Bordeaux INP, UMR 5629 , 16 Avenue Pey Berland F-33600 Pessac , France
| | - Hang Zhao
- Laboratoire de Chimie des Polymères Organiques, LCPO, Université de Bordeaux, CNRS, Bordeaux INP, UMR 5629 , 16 Avenue Pey Berland F-33600 Pessac , France
| | - Sébastien Lecommandoux
- Laboratoire de Chimie des Polymères Organiques, LCPO, Université de Bordeaux, CNRS, Bordeaux INP, UMR 5629 , 16 Avenue Pey Berland F-33600 Pessac , France
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Fernandez-Trillo F, Grover LM, Stephenson-Brown A, Harrison P, Mendes PM. Vesicles in Nature and the Laboratory: Elucidation of Their Biological Properties and Synthesis of Increasingly Complex Synthetic Vesicles. Angew Chem Int Ed Engl 2017; 56:3142-3160. [DOI: 10.1002/anie.201607825] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Revised: 10/12/2016] [Indexed: 12/19/2022]
Affiliation(s)
| | - Liam M. Grover
- School of Chemical Engineering; University of Birmingham; Edgbaston Birmingham B15 2TT UK
| | - Alex Stephenson-Brown
- School of Chemical Engineering; University of Birmingham; Edgbaston Birmingham B15 2TT UK
| | - Paul Harrison
- Institute of Inflammation and Ageing (IIA); University of Birmingham; Edgbaston Birmingham B15 2TT UK
| | - Paula M. Mendes
- School of Chemical Engineering; University of Birmingham; Edgbaston Birmingham B15 2TT UK
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7
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Fernandez-Trillo F, Grover LM, Stephenson-Brown A, Harrison P, Mendes PM. Vesikel in der Natur und im Labor: die Aufklärung der biologischen Eigenschaften und die Synthese zunehmend komplexer synthetischer Vesikel. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201607825] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
| | - Liam M. Grover
- School of Chemical Engineering; University of Birmingham; Edgbaston Birmingham B15 2TT Großbritannien
| | - Alex Stephenson-Brown
- School of Chemical Engineering; University of Birmingham; Edgbaston Birmingham B15 2TT Großbritannien
| | - Paul Harrison
- Institute of Inflammation and Ageing (IIA); University of Birmingham; Edgbaston Birmingham B15 2TT Großbritannien
| | - Paula M. Mendes
- School of Chemical Engineering; University of Birmingham; Edgbaston Birmingham B15 2TT Großbritannien
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8
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Chiapparino A, Maeda K, Turei D, Saez-Rodriguez J, Gavin AC. The orchestra of lipid-transfer proteins at the crossroads between metabolism and signaling. Prog Lipid Res 2015; 61:30-9. [PMID: 26658141 DOI: 10.1016/j.plipres.2015.10.004] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 10/15/2015] [Indexed: 01/12/2023]
Abstract
Within the eukaryotic cell, more than 1000 species of lipids define a series of membranes essential for cell function. Tightly controlled systems of lipid transport underlie the proper spatiotemporal distribution of membrane lipids, the coordination of spatially separated lipid metabolic pathways, and lipid signaling mediated by soluble proteins that may be localized some distance away from membranes. Alongside the well-established vesicular transport of lipids, non-vesicular transport mediated by a group of proteins referred to as lipid-transfer proteins (LTPs) is emerging as a key mechanism of lipid transport in a broad range of biological processes. More than a hundred LTPs exist in humans and these can be divided into at least ten protein families. LTPs are widely distributed in tissues, organelles and membrane contact sites (MCSs), as well as in the extracellular space. They all possess a soluble and globular domain that encapsulates a lipid monomer and they specifically bind and transport a wide range of lipids. Here, we present the most recent discoveries in the functions and physiological roles of LTPs, which have expanded the playground of lipids into the aqueous spaces of cells.
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Affiliation(s)
- Antonella Chiapparino
- European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Meyerhofstrasse 1, D-69117 Heidelberg, Germany
| | - Kenji Maeda
- European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Meyerhofstrasse 1, D-69117 Heidelberg, Germany
| | - Denes Turei
- European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Meyerhofstrasse 1, D-69117 Heidelberg, Germany; European Molecular Biology Laboratory (EMBL), European Bioinformatics Institute (EBI), Cambridge CB10 1SD, UK
| | - Julio Saez-Rodriguez
- European Molecular Biology Laboratory (EMBL), European Bioinformatics Institute (EBI), Cambridge CB10 1SD, UK
| | - Anne-Claude Gavin
- European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Meyerhofstrasse 1, D-69117 Heidelberg, Germany; European Molecular Biology Laboratory (EMBL), Molecular Medicine Partnership Unit (MMPU), Meyerhofstrasse 1, D-69117 Heidelberg, Germany.
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9
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Girotti AW, Kriska T. Binding and cytotoxic trafficking of cholesterol hydroperoxides by sterol carrier protein-2. Methods Mol Biol 2015; 1208:421-35. [PMID: 25323524 DOI: 10.1007/978-1-4939-1441-8_30] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Redox-active cholesterol hydroperoxides (ChOOHs) generated by oxidative stress in eukaryotic cells may propagate cytotoxic membrane damage by undergoing one-electron reduction or, at low levels, act as mobile signaling molecules like H2O2. We discovered that ChOOHs can spontaneously translocate between membranes or membranes and lipoproteins in model systems, and that this can be accelerated by sterol carrier protein-2 (SCP-2), a nonspecific lipid trafficking protein. We found that cells overexpressing SCP-2 were more susceptible to damage/toxicity by 7α-OOH (a free radical-generated ChOOH) than control cells, and that this correlated with 7α-OOH delivery to mitochondria. The methods used for obtaining these results and for establishing that cellular SCP-2 binds and traffics 7α-OOH are described in this chapter.
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Affiliation(s)
- Albert W Girotti
- Department of Biochemistry, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, 53226, USA,
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10
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Current overview of allergens of plant pathogenesis related protein families. ScientificWorldJournal 2014; 2014:543195. [PMID: 24696647 PMCID: PMC3947804 DOI: 10.1155/2014/543195] [Citation(s) in RCA: 108] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Accepted: 12/17/2013] [Indexed: 11/18/2022] Open
Abstract
Pathogenesis related (PR) proteins are one of the major sources of plant derived allergens. These proteins are induced by the plants as a defense response system in stress conditions like microbial and insect infections, wounding, exposure to harsh chemicals, and atmospheric conditions. However, some plant tissues that are more exposed to environmental conditions like UV irradiation and insect or fungal attacks express these proteins constitutively. These proteins are mostly resistant to proteases and most of them show considerable stability at low pH. Many of these plant pathogenesis related proteins are found to act as food allergens, latex allergens, and pollen allergens. Proteins having similar amino acid sequences among the members of PR proteins may be responsible for cross-reactivity among allergens from diverse plants. This review analyzes the different pathogenesis related protein families that have been reported as allergens. Proteins of these families have been characterized in regard to their biological functions, amino acid sequence, and cross-reactivity. The three-dimensional structures of some of these allergens have also been evaluated to elucidate the antigenic determinants of these molecules and to explain the cross-reactivity among the various allergens.
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11
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Abstract
The movement of lipids within and between intracellular membranes is mediated by different lipid transport mechanisms and is crucial for maintaining the identities of different cellular organelles. Non-vesicular lipid transport has a crucial role in intracellular lipid trafficking and distribution, but its underlying mechanisms remain unclear. Lipid-transfer proteins (LTPs), which regulate diverse lipid-mediated cellular processes and accelerate vectorial transport of lipid monomers between membranes in vitro, could potentially mediate non-vesicular intracellular lipid trafficking. Understanding the mechanisms by which lipids are transported and distributed between cellular membranes, and elucidating the role of LTPs in intracellular lipid transport and homeostasis, are currently subjects of intensive study.
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12
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Girotti AW. Translocation as a means of disseminating lipid hydroperoxide-induced oxidative damage and effector action. Free Radic Biol Med 2008; 44:956-68. [PMID: 18206663 PMCID: PMC2361152 DOI: 10.1016/j.freeradbiomed.2007.12.004] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2007] [Revised: 12/06/2007] [Accepted: 12/06/2007] [Indexed: 11/25/2022]
Abstract
Lipid hydroperoxides (LOOHs) generated in cells and lipoproteins under oxidative pressure may induce waves of damaging chain lipid peroxidation near their sites of origin if O2 is readily available and antioxidant capacity is overwhelmed. However, recent studies have demonstrated that chain induction is not necessarily limited to a nascent LOOH's immediate surroundings but can extend to other cell membranes or lipoproteins by means of LOOH translocation through the aqueous phase. Mobilization and translocation can also extend the range of LOOHs as redox signaling molecules and in this sense they could act like the small, readily diffusible inorganic analogue H2O2, which has been studied much more extensively in this regard. In this article, basic mechanisms of free-radical- and singlet-oxygen-mediated LOOH formation and one-electron and two-electron LOOH reduction pathways and their biological consequences are reviewed. The first studies to document spontaneous and protein-assisted LOOH transfer in model systems and cells are described. Finally, LOOH translocation is discussed in the context of cytotoxicity vs detoxification and expanded effector action, i.e., redox signaling activity.
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Affiliation(s)
- Albert W Girotti
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI 53226-4801, USA.
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13
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Kernstock RM, Girotti AW. Lipid transfer protein binding of unmodified natural lipids as assessed by surface plasmon resonance methodology. Anal Biochem 2007; 365:111-21. [PMID: 17376396 PMCID: PMC1975857 DOI: 10.1016/j.ab.2007.02.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2007] [Accepted: 02/16/2007] [Indexed: 12/12/2022]
Abstract
A new approach for analyzing lipid-lipid transfer protein interactions is described. The transfer protein is genetically engineered for expression with a C-terminal biotinylated peptide extension (AviTag). This allows protein anchoring to a streptavidin-coated chip for surface plasmon resonance (SPR)-based assessment of lipid binding. Sterol carrier protein-2 (SCP-2), involved in the intracellular trafficking of cholesterol, fatty acids, and other lipids, was selected as the prototype. Biotinylated SCP-2 (bSCP-2) was expressed in Escherichia coli, purified to homogeneity by mutated streptavidin (SoftLink) affinity chromatography, and confirmed by mass spectrometry to contain one biotin group at the expected position. Intermembrane [(14)C]cholesterol transfer was strongly enhanced by bSCP-2, demonstrating that it was functional. Using bSCP-2 immobilized on a Biacore streptavidin chip, we determined on- and off-rate constants along with equilibrium dissociation constants for the following analytes: oleic acid, linoleic acid, cholesterol, and fluorophore (NBD)-derivatized cholesterol. The dissociation constant for NBD-cholesterol was similar to that determined by fluorescence titration for SCP-2 in solution, thereby validating the SPR approach. This method can be readily adapted to other transfer proteins and has several advantages over existing techniques for measuring lipid binding, including (i) the ability to study lipids in their natural states (i.e., without relatively large reporter groups) and (ii) the ability to measure on- and off- rate constants as well as equilibrium constants.
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Affiliation(s)
| | - Albert W. Girotti
- *To whom correspondence should be addressed: Dr. Albert W. Girotti, Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI, 53226, Tel: 414-456-8432, Fax: 414-456-6510, E-mail:
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14
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Sanyal SN, Goyal M, Kanwar SS, Kaushal S. Use of phospholipid transfer protein as a probe to study the lipid dynamics and alkaline phosphatase activity in the brush border membrane of human term placenta. Chem Biodivers 2006; 3:527-34. [PMID: 17193288 DOI: 10.1002/cbdv.200690056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Incubation of placental brush border membrane (BBM) along with sonicated vesicles of exogenous lipids (egg yolk PC) in the presence of phospholipid-transfer protein (PL-TP) showed a decrease in the alkaline phosphatase activity due to the change in the membrane micro-environment, such as fluidity. Effect of substrate concentration was tested by Lineweaver-Burk plot, which showed decreased V(max) and K(M). The effect of temperature was probed by the Arrhenius plot, which showed no change in transition temperature, but a decline in the energy of activation both below and above the transition temperature. The protein-catalyzed transfer of phospholipid from the donor unilamellar vesicles resulted in a substantial increase in the BBM phospholipid and a net decrease in cholesterol/phospholipid molar ratio. The change in membrane fluidity was assessed by translational as well as rotational diffusion of membrane extrinsic fluorescent probes, pyrene and diphenyl-hexatriene. An increased lateral mobility was recorded by the increased pyrene excimer formation. A decrease in fluorescent polarization of diphenyl-hexatriene was observed, which led to the decrease in fluorescence anisotropy and order parameter, and therefore, an increase in membrane fluidity (rotational diffusion). Mean anisotropy parameter was also decreased in the presence of PL-TP. Thus, the placental BBM alkaline phosphatase activity showed a distinct lipid dependence which may have important physiological consequences.
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Affiliation(s)
- Sankar N Sanyal
- Department of Biophysics, Panjab University, Chandigarh, India. sanyalpu @gmail.com
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15
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Kriska T, Levchenko VV, Korytowski W, Atshaves BP, Schroeder F, Girotti AW. Intracellular Dissemination of Peroxidative Stress. J Biol Chem 2006; 281:23643-51. [PMID: 16772292 DOI: 10.1074/jbc.m600744200] [Citation(s) in RCA: 27] [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
Sterol carrier protein-2 (SCP-2) plays a crucial role in the trafficking and metabolism of cholesterol and other lipids in mammalian cells. Lipid hydroperoxides generated under oxidative stress conditions are relatively long-lived intermediates that damage cell membranes and play an important role in redox signaling. We hypothesized that SCP-2-facilitated translocation of lipid hydroperoxides in oxidatively stressed cells might enhance cytolethality if highly sensitive sites are targeted and detoxification capacity is insufficient. We tested this using a clone (SC2A) of rat hepatoma cells that overexpress mature immunodetectable SCP-2. When challenged with liposomal cholesterol-7alpha-hydroperoxide (7alpha-OOH), SC2A cells were found to be much more sensitive to viability loss than vector control (VC) counterparts. Correspondingly, SC2A cells imported [14C]7alpha-OOH more rapidly. The clones were equally sensitive to tert-butyl hydroperoxide, suggesting that the 7alpha-OOH effect was SCP-2-specific. Fluorescence intensity of the probes 2',7'-dichlorofluorescein and C11-BODIPY increased more rapidly in SC2A than VC cells after 7alpha-OOH exposure, consistent with more rapid internalization and oxidative turnover in the former. [14C]7alpha-OOH radioactivity accumulated much faster in SC2A mitochondria than in VC, whereas other subcellular fractions showed little rate difference. In keeping with this, 7alpha-OOH-stressed SC2A cells exhibited a faster loss of mitochondrial membrane potential and development of apoptosis. This is the first reported evidence that peroxidative stress damage can be selectively targeted and exacerbated by an intracellular lipid transfer protein.
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Affiliation(s)
- Tamas Kriska
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
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16
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Retzinger GS. Fibrinogen-coated chylomicrons in gastrointestinal lymph: a new rationale regarding the arterial deposition of postprandial lipids. Med Hypotheses 2002; 59:718-26. [PMID: 12445516 DOI: 10.1016/s0306-9877(02)00320-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The recent discovery that fibrinogen binds to chylomicrons in gastrointestinal lymph has prompted a new rationale regarding the arterial deposition of postprandial lipids, i.e., dietary fat. According to this new rationale, fibrinogen bound to chylomicrons in the gastrointestinal lymph renders those lipid particles and/or their remnants an adhesive potential, even before the particles reach the arterial system. It is proposed that such an adhesive potential, if realized in the vicinity of the arterial wall, can contribute to the nucleation and growth of atherosclerotic plaques, especially during and immediately following a fat-rich meal. Arguments in support of this proposal are made based on the proximity of the lymph outflow tract to the arteries most susceptible to atherosclerosis, and on the tissue distributions and activities of heparin, diamine oxidase, and lipoprotein lipase. This new rationale reconciles existing theories on atherosclerosis, and it also suggests novel means by which to prevent/treat the disease.
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Affiliation(s)
- Gregory S Retzinger
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio 45267-0529, USA.
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Gallegos AM, Atshaves BP, Storey SM, Starodub O, Petrescu AD, Huang H, McIntosh AL, Martin GG, Chao H, Kier AB, Schroeder F. Gene structure, intracellular localization, and functional roles of sterol carrier protein-2. Prog Lipid Res 2001; 40:498-563. [PMID: 11591437 DOI: 10.1016/s0163-7827(01)00015-7] [Citation(s) in RCA: 175] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Since its discovery three decades ago, sterol carrier protein-2 (SCP-2) has remained a fascinating protein whose physiological function in lipid metabolism remains an enigma. Its multiple proposed functions arise from its complex gene structure, post-translational processing, intracellular localization, and ligand specificity. The SCP-2 gene has two initiation sites coding for proteins that share a common 13 kDa SCP-2 C-terminus: (1) One site codes for 58 kDa SCP-x which is partially post-translationally cleaved to 13 kDa SCP-2 and a 45 kDa protein. (2) A second site codes for 15 kDa pro-SCP-2 which is completely post-translationally cleaved to 13 kDa SCP-2. Very little is yet known regarding how the relative proportions of the two transcripts are regulated. Although all three proteins contain a C-terminal SKL peroxisomal targeting sequence, it is unclear why all three proteins are not exclusively localized in peroxisomes. However, the recent demonstration that the SCP-2 N-terminal presequence in pro-SCP-2 dramatically modulated the intracellular targeting coded by the C-terminal peroxisomal targeting sequence may account for the observation that as much as half of total SCP-2 is localized outside the peroxisome. The tertiary and secondary structure of the 13 kDa SCP-2, but not that of 15 kDa pro-SCP-2 and 58 kDa SCP-x, are now resolved. Increasing evidence suggests that the 58 kDa SCP-x and 45 kDa proteins are peroxisomal 3-ketoacyl-CoA-thiolases involved in the oxidation of branched chain fatty acids. Since 15 kDa pro-SCP-2 is post-translationally completely cleaved to 13 kDa SCP-2, relatively little attention has been focused on this protein. Finally, although the 13 kDa SCP-2 is the most studied of these proteins, because it exhibits diversity of its ligand partners (fatty acids, fatty acyl CoAs, cholesterol, phospholipids), new potential physiological function(s) are still being proposed and questions regarding potential compensation by other proteins with overlapping specificity are only beginning to be resolved.
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Affiliation(s)
- A M Gallegos
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843-4467, USA
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18
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Choinowski T, Hauser H, Piontek K. Structure of sterol carrier protein 2 at 1.8 A resolution reveals a hydrophobic tunnel suitable for lipid binding. Biochemistry 2000; 39:1897-902. [PMID: 10684638 DOI: 10.1021/bi992742e] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Sterol carrier protein 2, also known as nonspecific lipid transfer protein is a ubiquitous, small, basic protein of 13 kDa found in animals. Its primary structure is highly conserved between different species, and it has been implicated in the intracellular transport of lipids and in a wide range of other in vitro functions related to sterol and fatty acid metabolism. Sterol carrier protein 2 deficiency in mice leads to elevated concentrations of phytanic acid in the serum and causes hepatocarcinogenesis. However, its actual physiological role is still unknown. Although sterol carrier protein 2 has been studied extensively in the past 20 years, very little is known concerning its three-dimensional structure. The crystal structure of rabbit sterol carrier protein 2, determined at 1.8 A resolution with the MIRAS method, shows a unique alpha/beta-fold. The core of this protein forms a five-stranded antiparallel beta-sheet flanked by five helices. A C-terminal segment (residues 114-123), together with part of the beta-sheet and four alpha-helices, form a hydrophobic tunnel providing the environment for apolar ligands such as fatty acids and fatty acyl-coenzyme As. Structurally well-characterized nonspecific lipid transfer proteins from plants have hydrophobic tunnel-like cavities, which were identified as the binding site for fatty acids and related apolar ligands. Despite the fact that plant nonspecific lipid transfer proteins are smaller proteins than sterol carrier protein 2, show no sequence homology to sterol carrier protein 2, and are structurally unrelated, the cavities of these two classes of proteins are very similar with respect to size, shape, and hydrophobicity, suggesting a common functional role.
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Affiliation(s)
- T Choinowski
- Institute of Biochemistry, Swiss Federal Institute of Technology (ETH), Universitätstrasse 16, CH-8092 Zürich, Switzerland
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19
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Huang H, Ball JM, Billheimer JT, Schroeder F. The sterol carrier protein-2 amino terminus: a membrane interaction domain. Biochemistry 1999; 38:13231-43. [PMID: 10529196 DOI: 10.1021/bi990870x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Sterol carrier protein-2 (SCP2) is a small, 123 amino acid, protein postulated to play a role in intracellular transport and metabolism of lipids such as cholesterol, phospholipids, and branched chain fatty acids. While it is thought that interaction of SCP2 with membranes is necessary for lipid transfer, evidence for this possibility and identification of a membrane interaction domain within SCP2 has remained elusive. As shown herein with circular dichroism and a direct binding assay, SCP2 bound to small unilamellar vesicle (SUV) membranes to undergo significant alteration in secondary structure. The SCP2 amphipathic N-terminal 32 amino acids, comprised of two alpha-helical segments, were postulated to represent a putative phospholipid interaction site. This hypothesis was tested with a series of SCP2 N-terminal peptides, circular dichroism, and direct binding studies. The SCP2 N-terminal peptide (1-32)SCP2, primarily random coil in aqueous buffer, adopted alpha-helical structure upon interaction with membranes. The induction of alpha-helical structure in the peptide was maximal when the membranes contained a high mole percent of negatively charged phospholipid and of cholesterol. While deletion of the second alpha-helical segment within this peptide had no effect on formation of the first alpha-helix, it significantly weakened the peptide interaction with membranes. Substitution of Leu(20) with Glu(20) in the N-terminal peptide disrupted the alpha-helix structure and greatly weakened the peptide interaction with membranes. Finally, deletion of the first nine nonhelical amino acids had no effect either on formation of alpha-helix or on peptide binding to membranes. N-Terminal peptide (1-32)SCP2 competed with SCP2 for binding to SUV. These data were consistent with the N-terminus of SCP2 providing a membrane interaction domain that preferentially bound to membranes rich in anionic phospholipid and cholesterol.
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Affiliation(s)
- H Huang
- Department of Physiology and Pharmacology, Texas A&M University, College Station 77843-4466, USA
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20
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Chao H, Billheimer JT, Kier AB, Schroeder F. Microsomal long chain fatty acyl-CoA transacylation: differential effect of sterol carrier protein-2. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1439:371-83. [PMID: 10498408 DOI: 10.1016/s1388-1981(99)00109-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The recent discovery that sterol carrier protein-2 (SCP-2) binds long chain++ (LCFA-CoA) with high affinity (A. Frolov et al., J. Biol. Chem. 271 (1997) 31878-31884) suggests new possible functions of this protein in LCFA-CoA metabolism. The purpose of the present investigation was to determine whether SCP-2 differentially modulated microsomal LCFA-CoA transacylation to cholesteryl esters, triacylglycerols, and phospholipids in vitro. Microsomal acyl-CoA:cholesterol acyltransferase (ACAT) activity measured with liposomal membrane cholesterol donors depended on substrate LCFA-CoA level, mol% cholesterol in the liposomal membrane, and total amount of liposomal cholesterol. As compared to basal activity without liposomes, microsomal ACAT was inhibited 30-50% in the presence of cholesterol poor (1.4 mol%) liposomes. In contrast, cholesterol rich (>25 mol%) liposomes stimulated ACAT up to 6.4-fold compared to basal activity without liposomes and nearly 10-fold as compared to cholesterol pool (1.4 mol%) liposomes. Increasing oleoyl-CoA reversed the inhibition of microsomal ACAT by cholesterol poor (1.4 mol%) liposomes, but did not further stimulate ACAT in the presence of cholesterol rich (35 mol%) liposomes. In contrast, high (100 microM) oleoyl-CoA inhibited ACAT nearly 3-fold. This inhibition was reversed by LCFA-CoA binding proteins, bovine serum albumin (BSA) and SCP-2. SCP-2 was 10-fold more effective (mole for mole) than BSA in reversing LCFA-CoA inhibited microsomal ACAT. Concomitantly, under conditions in which SCP-2 stimulated ACAT it equally enhanced transacylation of oleoyl-CoA into phospholipids, and 5.2-fold enhanced oleoyl-CoA transacylation to triacylglycerols. In summary, SCP-2 appeared to exert its greatest effects on microsomal transacylation in vitro by reversing LCFA-CoA inhibition of ACAT and by differentially targeting LCFA-CoA to triacylglycerols. These data suggest that the high affinity interaction of SCP-2s with LCFA-CoA may be physiologically important in microsomal transacylation reactions.
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Affiliation(s)
- H Chao
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX 77843-4467, USA
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21
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Frolov A, Miller K, Billheimer JT, Cho TH, Schroeder F. Lipid specificity and location of the sterol carrier protein-2 fatty acid-binding site: a fluorescence displacement and energy transfer study. Lipids 1997; 32:1201-9. [PMID: 9397406 DOI: 10.1007/s11745-997-0154-5] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Although it was recently recognized that sterol carrier protein-2 (SCP-2) interacts with fatty acids, little is known regarding the specificity of SCP-2 for long-chain fatty acids or branched-chain fatty-acid-like molecules. Likewise the location of the fatty-acid binding site within SCP-2 is unresolved. A fluorescent cis-parinaric acid displacement assay was used to show that SCP-2 optimally interacted with 14-22 carbon chain lipidic molecules: polyunsaturated fatty acids > monounsaturated, saturated > branched-chain isoprenoids > branched-chain phytol-derived fatty acids. In contrast, the other major fatty-acid binding protein in liver, fatty-acid binding protein (L-FABP), displayed a much narrower carbon chain preference in general: polyunsaturated fatty acids > branched-chain phytol-derived fatty acids > 14- and 16-carbon saturated > branched-chain isoprenoids. However, both SCP-2 and L-FABP displayed a very similar unsaturated fatty-acid specificity profile. The presence and location of the SCP-2 lipid binding site were investigated by fluorescence energy transfer. The distance between the SCP-2 Trp50 and bound cis-parinaric acid was determined to be 40 A. Thus, the SCP-2 fatty-acid binding site appeared to be located on the opposite side of the SCP-2 Trp50. These findings not only contribute to our understanding of the SCP-2 ligand binding site but also provide evidence suggesting a potential role for SCP-2 and/or L-FABP in metabolism of branched-chain fatty acids and isoprenoids.
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Affiliation(s)
- A Frolov
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station 77843-4466, USA
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22
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Stolowich NJ, Frolov A, Atshaves B, Murphy EJ, Jolly CA, Billheimer JT, Scott AI, Schroeder F. The sterol carrier protein-2 fatty acid binding site: an NMR, circular dichroic, and fluorescence spectroscopic determination. Biochemistry 1997; 36:1719-29. [PMID: 9048555 DOI: 10.1021/bi962317a] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The interaction and orientation of fatty acids with recombinant human sterol carrier protein-2 (SCP-2) were examined by nuclear magnetic resonance (NMR), circular dichroism (CD), and fluorescence techniques. 13C-NMR spectroscopy of stearic acid and oleic acid as well as fluorescence spectroscopy of cis-parinaric acid demonstrated that SCP-2 bound naturally occurring fatty acids with near 1:1 stoichiometry. Several findings indicated that the fatty acid was oriented in the binding site with its methyl end buried in the protein interior and its carboxylate exposed at the surface: the chemical shift of bound [18-13C]-stearate; dicarboxylic/monocarboxylic acid cis-parinaric acid displacement; complete ionization of the carboxylate group of SCP-2 bound [1-13C]stearate at neutral pH; lack of electrostatic interactions between 13C-fatty acids with SCP-2 cationic residues: pH titratability of the SCP-2 bound [1-13C]stearate carboxylate group. SCP-2 did not undergo global structural changes upon ligand binding or pH decrease as indicated by the absence of significant changes in NMR and only small alterations in time resolved fluorescence parameters. However, SCP-2 did undergo secondary structural changes detected by CD in the pH range 5-6. While these changes in secondary structure did not alter the fatty acid:SCP-2 binding stoichiometry, the affinity for fatty acid was increased severalfold at lower pH. In summary, 13C-NMR, CD, and fluorescence spectroscopy provided a detailed understanding of the interaction of fatty acids with SCP-2 and further showed for the first time the orientation of the fatty acid within the binding site. The pH-induced changes in SCP-2 secondary structure and ligand binding activity may be important to the mechanism whereby this protein interacts with membrane surfaces to enhance lipid binding/transfer.
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Affiliation(s)
- N J Stolowich
- Department of Chemistry, Texas A&M University, College Station 77843-3255, USA
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23
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Weisiger RA. Cytoplasmic transport of lipids: Role of binding proteins. Comp Biochem Physiol B Biochem Mol Biol 1996. [DOI: 10.1016/s0305-0491(96)00179-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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24
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Storch J, Herr FM, Hsu KT, Kim HK, Liou HL, Smith ER. The role of membranes and intracellular binding proteins in cytoplasmic transport of hydrophobic molecules: Fatty acid-binding proteins. Comp Biochem Physiol B Biochem Mol Biol 1996. [DOI: 10.1016/s0305-0491(96)00180-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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25
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Meijer GW, Groener JE, Beynen AC, Van Tol A. CETP activity in liver perfusates and plasma from rabbits hypo- or hyperresponsive to dietary cholesterol. Comp Biochem Physiol B Biochem Mol Biol 1996; 114:403-7. [PMID: 8840515 DOI: 10.1016/0305-0491(96)00070-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We investigated the relationship between the development of hypercholesterolemia in rabbits and cholesteryl ester transfer protein (CETP) activity secretion by their perfused livers. Two inbred strains of rabbits were compared which differ markedly in their hypercholesterolemic response to dietary cholesterol. Feeding a high-cholesterol (0.3%) diet, increased plasma and liver cholesterol level in the two strains, the increments being 15 mM and 30 mumol/g greater in the hyperresponders, respectively. The high-cholesterol diet caused an about 2-fold increased hepatic secretion of CETP activity, but there was no difference between the two rabbit strains. Feeding a lower amount of dietary cholesterol (0.08%) also caused higher cholesterolemic (2 mM) and hepatocholesterolic (28 mumol/g) responses in hyper- than in hyporesponsive rabbits. The activity of hepatic CETP secretion was not increased by the low-cholesterol diet, and there was no difference between hypo- and hyperresponsive rabbits. Cholesterol feeding increased plasma CETP activity by 90% in both rabbit strains, but there was no difference between the strains. Our combined data suggest that with increasing plasma cholesterol levels hepatic CETP secretion may be increased in a parabolic manner, reaching its maximum rate for before plasma cholesterol concentrations are maximal. There were no differences in hepatic CETP activity secretion of plasma CETP activity levels between the genetically different strains of hypo- and hyperresponsive rabbits.
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Affiliation(s)
- G W Meijer
- Department of Laboratory Animal Science, University of Utrecht, The Netherlands
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26
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Christison JK, Rye KA, Stocker R. Exchange of oxidized cholesteryl linoleate between LDL and HDL mediated by cholesteryl ester transfer protein. J Lipid Res 1995. [DOI: 10.1016/s0022-2275(20)41119-8] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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27
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Ohta T, Nakamura R, Frohlich JJ, Pritchard PH, Matsuda I. Characterization of subspecies of lipoprotein containing apolipoprotein A-I in heterozygotes for familial lecithin:cholesterol acyltransferase deficiency. Atherosclerosis 1995; 114:147-55. [PMID: 7605383 DOI: 10.1016/0021-9150(94)05478-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We characterized two species of lipoproteins containing apo A-I, one containing only apo A-I (LpA-I) and the other containing both apo A-I and apo A-II (LpA-I/A-II), in three heterozygotes for familial lecithin:cholesterol acyltransferase deficiency (LCAT). In these patients, particle size and the chemical composition of LpA-I differed from those in normal controls. Small particles < 8.8 nm in diameter were predominant, and protein content was higher in patients' LpA-I than that in normal LpA-I. Changes in LpA-I/A-II were mostly quantitative. Percent lipid and protein composition in LpA-I/A-II were similar to those in normal controls. Despite low LCAT mass and activity in the heterozygotes, the molar and fractional rate of cholesterol esterification in their LpA-I and LpA-I/A-II particles were similar to, or higher than, that of normal controls. We conclude that: (i) low LCAT mass and activity is the likely cause of the quantitative and qualitative differences in LpA-I in heterozygotes; and (ii) a deficiency of normal LpA-I particles 11.1 nm in diameter and the existence of small particles < 8.8 nm in diameter may be responsible for the normal, or higher than normal, cholesterol esterification rate of LpA-I and LpA-I/A-II in heterozygotes.
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Affiliation(s)
- T Ohta
- Department of Pediatrics, Kumamoto University School of Medicine, Japan
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28
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Ikeda Y, Ohta T, Matsuda I. Interaction between apo A-I-containing lipoproteins and lecithin:cholesterol acyltransferase. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1215:307-13. [PMID: 7811716 DOI: 10.1016/0005-2760(94)90058-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
HDL2 and HDL3 subfractions of two species of apo A-I-containing lipoprotein, one containing only apo A-I (LpA-I) and the other containing both apo A-I and apo A-II (LpA-I/A-II), were tested for reactivity to lecithin:cholesterol acyltransferase (LCAT). These subfractions and their mixtures were incubated with lipoprotein-deficient plasma (LCAT source), and the rate of cholesterol esterification and kinetic parameters were determined. Apparent Vmax (appVmax) and apparent Km (appKm) for HDL2 subfractions of LpA-I and LpA-I/A-II were significantly lower than those of their HDL3 counterparts. Differences between subfractions were much more prominent in LpA-I than in LpA-I/A-II. appVmax of the HDL2 subfraction of LpA-I (LpA-IHDL2) was one-fifth, and appKm was one-third of those for the HDL3 subfraction (LpA-IHDL3). appVmax and appKm of LpA-IHDL2 were both lowest among the apo A-I-containing lipoprotein subfractions. When LpA-IHDL2 was added to other subfractions, the molar rate of cholesterol esterification was suppressed. Since LpA-IHDL2 consists of a particle 11.1 nm in diameter, our observations suggest that LpA-IHDL2 suppresses cholesterol esterification in apo A-I-containing lipoprotein, possibly by displacing LCAT from other subfractions with higher appKm and higher appVmax to 11.1 nm LpA-I particles with lower appKm and lower appVmax. All of these data suggest that the relative amount of 11.1 nm LpA-I particles in plasma regulates the reactivity of apo A-I-containing lipoprotein to LCAT and may play a key role on the production of cholesteryl esters in plasma.
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Affiliation(s)
- Y Ikeda
- Department of Pediatrics, Kumamoto University School of Medicine, Kumamoto, Japan
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29
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Evidence for impaired cellular cholesterol removal mediated by APO A-I containing lipoproteins in patients with familial lecithin: cholesterol acyltransferase deficiency. ACTA ACUST UNITED AC 1994. [DOI: 10.1016/0005-2760(94)00056-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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30
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Ohta T, Hattori S, Nakamura R, Horiuchi S, Frohlich J, Takata K, Ikeda Y, Saito Y, Matsuda I. Characterization of subspecies of apolipoprotein A-I-containing lipoprotein in homozygotes for familial lecithin:cholesterol acyltransferase deficiency. ARTERIOSCLEROSIS AND THROMBOSIS : A JOURNAL OF VASCULAR BIOLOGY 1994; 14:1137-45. [PMID: 8018670 DOI: 10.1161/01.atv.14.7.1137] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We characterized the two species of lipoproteins containing apolipoprotein A-I (apoA-I), one containing only apoA-I (LpA-I) and the other containing apoA-I and apoA-II (LpA-I/A-II), in four homozygotes for familial lecithin: cholesterol acyltransferase (LCAT) deficiency. Two homozygotes lacked both LCAT mass and activity, whereas the other two had some residual LCAT mass and activity. In these patients, the amount of all apoA-I-containing lipoproteins was one fourth that of normal control subjects, and > 60% was LpA-I. The chemical composition of both LpA-I and LpA-I/A-II is characterized by markedly decreased ratios of neutral to polar lipids compared with those of normals and the sizes of LpA-I and LpA-I/A-II particles are shifted to smaller and larger diameter ranges when compared with those of normal particles. Changes in particle diameter are also reflected in slower electrophoretic mobilities of both LpA-I and LpA-I/A-II particles. All of these abnormalities were more evident in the two homozygotes who lacked LCAT activity. Incubation of LCAT-deficient plasma with LCAT markedly corrected the chemical and physical abnormalities in both LpA-I and LpA-I/A-II particles. These data, taken together, emphasize the importance of LCAT in modifying the chemical composition, size, and shape of LpA-I and LpA-I/A-II particles.
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Affiliation(s)
- T Ohta
- Department of Pediatrics, Kumamoto University School of Medicine, Japan
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31
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Shina R, Crain RC, Rosenberg P, Condrea E. Exposure of phosphatidylcholine and phosphatidylinositol in plasma membranes from rat brain synaptosomes treated with phospholipase A2 toxins (beta-bungarotoxin, notexin) and enzymes (Naja nigricollis, Naja naja atra). Toxicon 1994; 32:675-85. [PMID: 7940575 DOI: 10.1016/0041-0101(94)90337-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Phospholipase A2 (PLA2) toxins act presynaptically to block acetylcholine release and are much more potent and specific in their actions than PLA2 enzymes even though they have lower enzymatic activity. Since their mechanism of action is not completely understood, it was of interest to examine the toxins' effects on phospholipid asymmetry as changes in asymmetry are associated with changes in membrane functioning. Rat brain synaptosomes were treated with the PLA2 toxins beta-bungarotoxin (beta-BuTx) and notexin and with the PLA2 enzymes Naja nigricollis and Naja naja atra under relatively non-disruptive conditions as judged by leakage of lactate dehydrogenase (LDH) and levels of phospholipid hydrolysis. The exposure of phosphatidylcholine (PC) and phosphatidylinositol (PI) on the synaptosomal surface was investigated by means of a specific PC-exchange protein (PCEP) and a PI-specific phospholipase C (PI-PLC), respectively. Treatment of the synaptosomes with N. nigricollis PLA2, beta-BuTx and notexin did not affect the availability of PC to exchange by PCEP, but significantly increased the exposure of PI to hydrolysis by PI-PLC. In contrast, N. n. atra PLA2 slightly decreased the exposure of PC and did not affect that of PI. The differences between N. n. atra PLA2, on the one hand, and N. nigricollis PLA2, beta-BuTx and notexin, on the other hand, parallel differences in their pharmacological activities. Our earlier studies showed that PLA2 enzymes, and possibly PLA2 toxins, have a pharmacological site separate from the enzymatic site. Since in the present study the effect on PI was abolished by EDTA, the presence of an enzymatic site in addition to the pharmacological site may be required or alternatively divalent cations may be required for the effects on PI asymmetry independent of the inhibition of PLA2 by EDTA.
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Affiliation(s)
- R Shina
- Basil and Gerald Felsenstein Medical Research Center, Petah Tikva, Israel
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32
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Shina R, Crain RC, Rosenberg P, Condrea E. The asymmetric distribution of phosphatidylcholine in rat brain synaptic plasma membranes. Neurochem Int 1993; 22:189-95. [PMID: 8439772 PMCID: PMC7135640 DOI: 10.1016/0197-0186(93)90012-t] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The distribution of phosphatidylcholine between inner and outer monolayers of rat brain synaptic plasma membrane was investigated by means of a phosphatidylcholine specific exchange protein. About 70% of the total membranal phosphatidylcholine was in the outer leaflet, 33% of which was exposed and readily exchanged in intact synaptosomes while the remainder was exchangeable following osmotic shock. Permeabilization of the synaptic plasma membranes by overnight incubation in buffer or by saponin (< 0.08%) exposed an additional 30% of phosphatidylcholine to exchange, presumably from the inner cytoplasmic leaflet. Phosphatidylcholine is therefore asymmetrically distributed in the synaptosomal plasma membrane, as it is in other plasma membranes.
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Affiliation(s)
- R Shina
- Basil and Gerald Felsenstein Medical Research Center, Rogoff-Wellcome Medical Research Institute, Sackler School of Medicine, Tel Aviv University, Beilinson Medical Center, Petah Tikva, Israel
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33
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Tahara D, Nakanishi T, Akazawa S, Yamaguchi Y, Yamamoto H, Akashi M, Chikuba N, Okuno S, Maeda Y, Kusumoto Y. Lecithin-cholesterol acyltransferase and lipid transfer protein activities in liver disease. Metabolism 1993; 42:19-23. [PMID: 8446043 DOI: 10.1016/0026-0495(93)90166-l] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The activities of lecithin-cholesterol acyltransferase (LCAT) and lipid transfer protein (LTP) were assayed using sensitive radioassay methods in controls (n = 113) and in patients with various liver diseases (n = 72). Plasma LCAT activity decreased with progression of hepatocellular damage. Plasma LTP activity in controls was 216 +/- 68 nmol/mL/h, and there were no significant differences between controls and patients with chronic hepatitis ([CH], 193 +/- 70), compensated liver cirrhosis (LC) with or without hepatocellular carcinoma ([HCC], 197 +/- 48 and 193 +/- 62, respectively), or decompensated liver cirrhosis ([dLC], 182 +/- 65). In acute viral hepatitis, LTP activity decreased significantly; however, the degree of reduction was not as dramatic as that for LCAT. There was no correlation between LCAT and LTP activity both in controls and patients with various liver diseases. LCAT activity was positively correlated with serum albumin (r = .52, P < 0.1) and cholinesterase (r = .37, P < .01) levels, and inversely correlated with serum bilirubin level (r = -.38, P < 0.1); there was no correlation between plasma LTP activity and these parameters of liver function. That plasma LTP activity did not change with hepatocellular damage may indicate that the liver in humans may not be the primary site of LTP production.
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Affiliation(s)
- D Tahara
- First Department of Internal Medicine, Nagasaki University School of Medicine, Japan
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34
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Abstract
The distribution of dolichol in rat liver was studied. Upon high-speed centrifugation, 9% of the total tissue dolichol was recovered in the supernatant. Dolichol was enclosed in vesicles and in lipidic particles which were isolated by gel filtration and density gradient centrifugation. The particles had a diameter of 20 nm and contained dolichol, ubiquinone, cholesterol, phospholipid and some protein. Similar particles were recovered upon incubation of isolated hepatocytes with liposomes containing dolichol. From the lysosomal lumen, lipid particles containing dolichol, ubiquinone, cholesterol and phospholipid, but no protein, were isolated. The diameter of the particles was 20-40 nm with a molecular weight of 130 kDa. Puromycin treatment inhibited protein synthesis, but did not affect dolichol transfer from the endoplasmic reticulum to lysosomes, suggesting that the transfer is not mediated by newly synthesized apoprotein. The results indicate that a sizeable portion of the total cellular dolichol is present in cytoplasm and in lysosomal lumen. Furthermore, dolichol probably participates in the translocation process.
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Affiliation(s)
- P Löw
- Department of Biochemistry, University of Stockholm, Sweden
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36
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Mangiapane EH. Mitochondrial phosphatidate is converted to triacylglycerol in rat hepatocytes. Arch Biochem Biophys 1991; 290:445-50. [PMID: 1929411 DOI: 10.1016/0003-9861(91)90564-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Phosphatidate is formed in both the endoplasmic reticulum and the outer mitochondrial membrane in rat liver. To investigate whether the phosphatidate synthesized in mitochondria can be converted to triacylglycerol in vivo, two experimental approaches were employed. (i) [3H]Phosphatidate-labeled mitochondria were enclosed in plasma membrane vesicles and these fused, in the presence of inactivated Sendai virus and calcium ions, to hepatocytes in monolayer culture. The recovery of radioactivity in various cell-associated lipids was measured. (ii) Mitochondrial phosphatidate was labeled with [14C]palmitate in hepatocytes which had been permeabilized with lysophosphatidylcholine and in which the microsomal glycerolphosphate acyltransferase had been inhibited with N-ethylmaleimide. The recovery of radioactivity in various lipids after incubation with particle free supernatant was measured. Evidence was obtained from both these experimental approaches that mitochondrial phosphatidate can be converted to triacylglycerol in rat hepatocytes. The results are discussed in relation to the role of mitochondrial phosphatidate in liver lipid metabolism.
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Affiliation(s)
- E H Mangiapane
- Department of Biochemistry, University of Nottingham Medical School, Queen's Medical Centre, United Kingdom
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37
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Supernovich C, Crain R, Rosenberg P. Phosphatidylcholine asymmetry in electroplax from the electric eel: use of a phosphatidylcholine exchange protein. J Neurochem 1991; 57:575-84. [PMID: 2072103 DOI: 10.1111/j.1471-4159.1991.tb03788.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Phosphatidylcholine asymmetry in the inner and outer leaflets of the plasma membrane bilayer of the innervated and noninnervated surfaces of the electroplax cell was determined, using a phosphatidylcholine exchange protein. The exchange protein from bovine liver catalyzed the exchange of phosphatidylcholine from small unilamellar vesicles to the outer monolayer of the plasma membrane bilayer. The exchange protein did not penetrate to the inner monolayer of the plasma membrane, did not modify the permeability of the electroplax, and did not alter the phospholipid or cholesterol content of the electroplax. In the innervated plasma membrane, 42% of the phosphatidylcholine is in the outer leaflet, 33% is in the inner leaflet, and 25% is inaccessible to the exchange protein. Corresponding values for the noninnervated plasma membrane are 56, 26, and 18%, respectively. These results are similar to phosphatidylcholine asymmetry in other biological membranes. This unique cell can be used as a model to test the effects on phospholipid asymmetry of compounds that act on the membrane.
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Affiliation(s)
- C Supernovich
- Section of Pharmacology and Toxicology, School of Pharmacy, University of Connecticut, Storrs 06269
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38
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Ericsson J, Scallen T, Chojnacki T, Dallner G. Involvement of sterol carrier protein-2 in dolichol biosynthesis. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)99266-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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39
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Green SR, Pittman RC. Comparative acyl specificities for transfer and selective uptake of high density lipoprotein cholesteryl esters. J Lipid Res 1991. [DOI: 10.1016/s0022-2275(20)42069-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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40
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Abstract
Translocations of various lipid species between membranes have been extensively studied. The transport of water-insoluble lipids is thought to require the participation of lipid transfer proteins (LTP). Several LTP, differing in their physiochemical properties and substrate specificities, have been purified to homogeneity from blood plasma, eucaryotic and procaryotic cells. Depending on their site of activity, they can be classified as extracellular and intracellular LTP. Extracellular LTP are found in the blood plasma and intracellular LTP, which were originally characterized as phospholipid exchange proteins, are ubiquitous in nature. Despite the enormous knowledge about their physicochemical properties and their function in vitro their physiological role has not been clearly demonstrated. However, their ubiquitous occurrence indicates an important role in cellular events. This review gives an overview of this interesting category of proteins, which are able to catalyze inter-membrane transfer and exchange of lipids.
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Affiliation(s)
- D G Rueckert
- Department of Surgery, University of Tuebingen, F.R.G
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41
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Bentejac M, Bugaut M, Delachambre MC, Lecerf J. Metabolic fate of sphingomyelin of high-density lipoprotein in rat plasma. Lipids 1990; 25:653-60. [PMID: 2079870 DOI: 10.1007/bf02536017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The metabolic fate of high density lipoprotein (HDL) sphingomyelin in plasma was studied in rats over a 24-hr period after injection of HDL containing sphingomyelin which was 14C-labeled in the stearic (18:0) or lignoceric acid (24:0) moiety and 3H-labeled in the choline methyl groups. Decay of label in plasma followed three phases. The first two phases were similar for both isotopes and both types of sphingomyelin (t1/2 approximately 10 and 110 min). However, during the third phase (from 10 hr after injection), 3H label disappeared more slowly than 14C label from 18:0 sphingomyelin, whereas the 3H/14C ratio remained relatively constant when 24:0 sphingomyelin was used. Intact, doubly-labeled 18:0 sphingomyelin disappeared from HDL rapidly (t1/2 = 38 min) by tissue uptake and by transfer to very low density lipoprotein (VLDL). VLDL contained up to 12% of the sphingomyelin 1 hr after injection. This is the first demonstration of a transfer in vivo of sphingomyelin from HDL to VLDL. A similarly rapid transfer was also observed in vitro. Some nontritiated, [14C]18:0 or [14C]24:0 sphingomyelin was redistributed more slowly into HDL. Doubly-labeled phosphatidylcholine appeared in VLDL and HDL within 1 hr after injection and reached 1.8 and 2.1% of the injected 14C and 3H in VLDL at 1 hr, and 4.8 and 6.9% in HDL at 3 hr, respectively.
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Affiliation(s)
- M Bentejac
- Laboratoire de Physiologie Animale et de la Nutrition, Faculte des Sciences Mirande, Universite de Dijon-BP 138, France
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42
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43
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Affiliation(s)
- R C Crain
- Department of Molecular and Cell Biology, University of Connecticut, Storrs 06268
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44
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Schroeder F, Butko P, Nemecz G, Scallen TJ. Interaction of fluorescent delta 5,7,9(11),22-ergostatetraen-3 beta-ol with sterol carrier protein-2. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)40208-1] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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45
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Reichl D, Miller NE. Pathophysiology of reverse cholesterol transport. Insights from inherited disorders of lipoprotein metabolism. ARTERIOSCLEROSIS (DALLAS, TEX.) 1989; 9:785-97. [PMID: 2686603 DOI: 10.1161/01.atv.9.6.785] [Citation(s) in RCA: 190] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- D Reichl
- Medical Research Council External Scientific Staff, St. Bartholomew's Hospital, London, UK
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46
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Affiliation(s)
- D J Betteridge
- Department of Medicine, University College and Middlesex School of Medicine, London, UK
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47
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Scapin G, Spadon P, Pengo L, Mammi M, Zanotti G, Monaco HL. Chicken liver basic fatty acid-binding protein (pI = 9.0). Purification, crystallization and preliminary X-ray data. FEBS Lett 1988; 240:196-200. [PMID: 3191992 DOI: 10.1016/0014-5793(88)80367-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Chicken liver basic fatty acid-binding protein (pI = 9.0) has been purified with a high yield by a modification of a method originally applied to rat liver. The final product is highly homogeneous and can be used to grow crystals that belong to two different space groups. The crystals are either tetragonal, space group P4(2)2(1)2 with a = b = 60.2 A and c = 138.1 A or orthorhombic, space group P2(1)2(1)2(1) with a = 60.7 A, b = 40.1 A and c = 66.7 A. The second form appears to be more suitable for X-ray diffraction studies, it diffracts to at least 2.8 A resolution and it is believed to contain one protein molecule in the crystallographic asymmetric unit.
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Affiliation(s)
- G Scapin
- Department of Organic Chemistry, University of Padova, Italy
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48
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van Paridon PA, Gadella TW, Somerharju PJ, Wirtz KW. Properties of the binding sites for the sn-1 and sn-2 acyl chains on the phosphatidylinositol transfer protein from bovine brain. Biochemistry 1988; 27:6208-14. [PMID: 3219332 DOI: 10.1021/bi00417a003] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
We have studied the properties of the fatty acyl binding sites of the phosphatidylinositol transfer protein (PI-TP) from bovine brain, by measuring the binding and transfer of pyrenylacyl-containing phosphatidylinositol (PyrPI) species and pyrenylacyl-containing phosphatidylcholine (PyrPC) species as a function of the acyl chain length. The PyrPI species carried a pyrene-labeled acyl chain of variable length in the sn-2 position and either palmitic acid [C(16)], palmitoleic acid [C(16:1)], or stearic acid [C(18:1)] in the sn-1 position. Binding and transfer of the PI species increased in the order C(18) less than C(16) less than C(16:1), with a distinct preference for those species that carry a pyrenyloctanoyl [Pyr(8)] or a pyrenyldecanoyl [Pyr(10)] chain. The PyrPC species studied consisted of two sets of positional isomers: one set contained a pyrenylacyl chain of variable length and a C(16) chain, and the other set contained an unlabeled chain of variable length and a Pyr(10) chain. The binding and transfer experiments showed that PI-TP discriminates between positional isomers with a preference for the species with a pyrenylacyl chain in the sn-1 position. This discrimination is interpreted to indicate that separate binding sites exist for the sn-1 and sn-2 acyl chains. From the binding and transfer profiles it is apparent that the binding sites differ in their preference for a particular acyl chain length. The binding and transfer vs chain length profiles were quite similar for C(16)Pyr(x)PC and C(16)Pyr(x)PI species, suggesting that the sn-2 acyl chains of PI and PC share a common binding site in PI-TP.
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Affiliation(s)
- P A van Paridon
- Laboratory of Biochemistry, State University of Utrecht, The Netherlands
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49
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50
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Shepherd J, Packard CJ. Lipid transport through the plasma: the metabolic basis of hyperlipidaemia. BAILLIERE'S CLINICAL ENDOCRINOLOGY AND METABOLISM 1987; 1:495-514. [PMID: 3330420 DOI: 10.1016/s0950-351x(87)80021-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Plasma lipid abnormalities derive their importance from their association with coronary artery disease. Elevated cholesterol levels accentuate risk, and clinical trials have shown that reductions lead to a decline in coronary events. The major plasma lipids, cholesterol and triglyceride, circulate in association with specific proteins as lipid-protein or lipoprotein complexes. The proteins direct and regulate the metabolism of these complexes by interacting with tissue enzymes and receptors. The metabolic fate of circulating triglyceride is governed by the activity of the enzyme lipoprotein lipase, situated in adipose tissue and skeletal muscle. Cellular demand for cholesterol, on the other hand, is met by activation of a specific receptor which mediates the delivery of sterol-rich lipoproteins to lysosomal degradation in liver and peripheral tissues. In order to prevent excess cholesterol accumulation at the periphery, there is a system of reverse cholesterol transport which involves assimilation and trapping of the sterol in the plasma lipoproteins through the action of the enzyme lecithin:cholesterol acyltransferase. Thereafter, the cholesterol is delivered to the liver, the only organ capable of excreting it in significant amounts. Disturbances in these processes may produce gross changes in the plasma lipid profile, clearly recognizable as hyperlipidaemia. However, it is becoming increasingly clear that a number of inherited traits can subtly perturb the lipoprotein spectrum and increase coronary risk even in subjects whose plasma lipoprotein profile would be considered normal.
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