1
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Cisse A, Desfosses A, Stainer S, Kandiah E, Traore DAK, Bezault A, Schachner-Nedherer AL, Leitinger G, Hoerl G, Hinterdorfer P, Gutsche I, Prassl R, Peters J, Kornmueller K. Targeting structural flexibility in low density lipoprotein by integrating cryo-electron microscopy and high-speed atomic force microscopy. Int J Biol Macromol 2023; 252:126345. [PMID: 37619685 DOI: 10.1016/j.ijbiomac.2023.126345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Revised: 08/08/2023] [Accepted: 08/13/2023] [Indexed: 08/26/2023]
Abstract
Low-density lipoprotein (LDL) plays a crucial role in cholesterol metabolism. Responsible for cholesterol transport from the liver to the organs, LDL accumulation in the arteries is a primary cause of cardiovascular diseases, such as atherosclerosis. This work focuses on the fundamental question of the LDL molecular structure, as well as the topology and molecular motions of apolipoprotein B-100 (apo B-100), which is addressed by single-particle cryo-electron microscopy (cryo-EM) and high-speed atomic force microscopy (HS-AFM). Our results suggest a revised model of the LDL core organization with respect to the cholesterol ester (CE) arrangement. In addition, a high-density region close to the flattened poles could be identified, likely enriched in free cholesterol. The most remarkable new details are two protrusions on the LDL surface, attributed to the protein apo B-100. HS-AFM adds the dimension of time and reveals for the first time a highly dynamic direct description of LDL, where we could follow large domain fluctuations of the protrusions in real time. To tackle the inherent flexibility and heterogeneity of LDL, the cryo-EM maps are further assessed by 3D variability analysis. Our study gives a detailed explanation how to approach the intrinsic flexibility of a complex system comprising lipids and protein.
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Affiliation(s)
- Aline Cisse
- Université Grenoble Alpes, CNRS, LiPhy, Grenoble, France; Institut Laue-Langevin, Grenoble, France
| | - Ambroise Desfosses
- Institut de Biologie Structurale, Université Grenoble Alpes, CEA, CNRS, IBS, Grenoble, France
| | - Sarah Stainer
- Department of Experimental Applied Biophysics, Johannes Kepler University Linz, Linz, Austria
| | | | - Daouda A K Traore
- Institut Laue-Langevin, Grenoble, France; Faculté de Pharmacie, Université des Sciences, des Techniques et des Technologies de Bamako (USTTB), Bamako, Mali; Faculty of Natural Sciences, School of Life Sciences, Keele University, Staffordshire, UK
| | - Armel Bezault
- Institut Européen de Chimie et Biologie, UAR3033/US001, Université de Bordeaux, CNRS, INSERM 2, Pessac, France; Structural Image Analysis Unit, Department of Structural Biology and Chemistry, Institut Pasteur, Université Paris Cité, CNRS UMR3528, Paris, France
| | - Anna-Laurence Schachner-Nedherer
- Gottfried Schatz Research Center for Cell Signaling, Metabolism and Aging, Medical Physics and Biophysics Division, Medical University of Graz, Graz, Austria
| | - Gerd Leitinger
- Gottfried Schatz Research Center for Cell Signaling, Metabolism and Aging, Division of Cell Biology, Histology and Embryology, Medical University of Graz, Graz, Austria
| | - Gerd Hoerl
- Otto Loewi Research Center, Physiological Chemistry, Medical University of Graz, Graz, Austria
| | - Peter Hinterdorfer
- Department of Experimental Applied Biophysics, Johannes Kepler University Linz, Linz, Austria
| | - Irina Gutsche
- Institut de Biologie Structurale, Université Grenoble Alpes, CEA, CNRS, IBS, Grenoble, France
| | - Ruth Prassl
- Gottfried Schatz Research Center for Cell Signaling, Metabolism and Aging, Medical Physics and Biophysics Division, Medical University of Graz, Graz, Austria
| | - Judith Peters
- Université Grenoble Alpes, CNRS, LiPhy, Grenoble, France; Institut Laue-Langevin, Grenoble, France; Institut Universitaire de France, France.
| | - Karin Kornmueller
- Institut Laue-Langevin, Grenoble, France; Gottfried Schatz Research Center for Cell Signaling, Metabolism and Aging, Medical Physics and Biophysics Division, Medical University of Graz, Graz, Austria.
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2
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Molk N, Bitenc M, Urlep D, Zerjav Tansek M, Bertok S, Trebusak Podkrajsek K, Sustar U, Kovac J, Battelino T, Debeljak M, Groselj U. Non-alcoholic fatty liver disease in a pediatric patient with heterozygous familial hypobetalipoproteinemia due to a novel APOB variant: a case report and systematic literature review. Front Med (Lausanne) 2023; 10:1106441. [PMID: 37384046 PMCID: PMC10293746 DOI: 10.3389/fmed.2023.1106441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Accepted: 05/09/2023] [Indexed: 06/30/2023] Open
Abstract
Background Familial hypobetalipoproteinemia (FHBL) is an autosomal semi-dominant disorder usually caused by variants in the APOB gene that frequently interferes with protein length. Clinical manifestations include malabsorption, non-alcoholic fatty liver disease, low levels of lipid-soluble vitamins, and neurological, endocrine, and hematological dysfunction. Methods Genomic DNA was isolated from the blood samples of the pediatric patient with hypocholesterolemia and his parents and brother. Next-generation sequencing (NGS) was performed, and an expanded dyslipidemia panel was employed for genetic analysis. In addition, a systematic review of the literature on FHBL heterozygous patients was performed. Case report Genetic investigation revealed the presence of a heterozygous variant in the APOB (NM_000384.3) gene c.6624dup[=], which changes the open reading frame and leads to early termination of translation into the p.Leu2209IlefsTer5 protein (NP_000375.3). The identified variant was not previously reported. Familial segregation analysis confirmed the variant in the mother of the subject, who also has a low level of low-density lipoprotein and non-alcoholic fatty liver disease. We have introduced therapy that includes limiting fats in the diet and adding lipid-soluble vitamins E, A, K, and D and calcium carbonate. We reported 35 individuals with APOB gene variations linked to FHBL in the systematic review. Conclusion We have identified a novel pathogenic variant in the APOB gene causing FHBL in pediatric patients with hypocholesterolemia and fatty liver disease. This case illustrates the importance of genetic testing for dyslipidemias in patients with significant decreases in plasma cholesterol as we can avoid damaging neurological and ophthalmological effects by sufficient vitamin supplementation and regular follow-ups.
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Affiliation(s)
- Neza Molk
- Department of Pediatric Endocrinology, Diabetes and Metabolism, University Medical Center-University Children's Hospital, Ljubljana, Slovenia
| | - Mojca Bitenc
- Department of Pediatric Endocrinology, Diabetes and Metabolism, University Medical Center-University Children's Hospital, Ljubljana, Slovenia
| | - Darja Urlep
- Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
- Department of Gastroenterology, Hepatology and Nutrition, University Children's Hospital Ljubljana, University Medical Center, Ljubljana, Slovenia
| | - Mojca Zerjav Tansek
- Department of Pediatric Endocrinology, Diabetes and Metabolism, University Medical Center-University Children's Hospital, Ljubljana, Slovenia
- Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Sara Bertok
- Department of Pediatric Endocrinology, Diabetes and Metabolism, University Medical Center-University Children's Hospital, Ljubljana, Slovenia
- Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Katarina Trebusak Podkrajsek
- Department of Gastroenterology, Hepatology and Nutrition, University Children's Hospital Ljubljana, University Medical Center, Ljubljana, Slovenia
- Clinical Institute for Special Laboratory Diagnostics, University Children's Hospital, University Medical Center Ljubljana, Ljubljana, Slovenia
| | - Ursa Sustar
- Department of Pediatric Endocrinology, Diabetes and Metabolism, University Medical Center-University Children's Hospital, Ljubljana, Slovenia
- Clinical Institute for Special Laboratory Diagnostics, University Children's Hospital, University Medical Center Ljubljana, Ljubljana, Slovenia
| | - Jernej Kovac
- Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
- Clinical Institute for Special Laboratory Diagnostics, University Children's Hospital, University Medical Center Ljubljana, Ljubljana, Slovenia
| | - Tadej Battelino
- Department of Pediatric Endocrinology, Diabetes and Metabolism, University Medical Center-University Children's Hospital, Ljubljana, Slovenia
- Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Marusa Debeljak
- Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
- Clinical Institute for Special Laboratory Diagnostics, University Children's Hospital, University Medical Center Ljubljana, Ljubljana, Slovenia
| | - Urh Groselj
- Department of Pediatric Endocrinology, Diabetes and Metabolism, University Medical Center-University Children's Hospital, Ljubljana, Slovenia
- Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
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3
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A New Structural Model of Apolipoprotein B100 Based on Computational Modeling and Cross Linking. Int J Mol Sci 2022; 23:ijms231911480. [PMID: 36232786 PMCID: PMC9569473 DOI: 10.3390/ijms231911480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 09/17/2022] [Accepted: 09/18/2022] [Indexed: 12/02/2022] Open
Abstract
ApoB-100 is a member of a large lipid transfer protein superfamily and is one of the main apolipoproteins found on low-density lipoprotein (LDL) and very low-density lipoprotein (VLDL) particles. Despite its clinical significance for the development of cardiovascular disease, there is limited information on apoB-100 structure. We have developed a novel method based on the “divide and conquer” algorithm, using PSIPRED software, by dividing apoB-100 into five subunits and 11 domains. Models of each domain were prepared using I-TASSER, DEMO, RoseTTAFold, Phyre2, and MODELLER. Subsequently, we used disuccinimidyl sulfoxide (DSSO), a new mass spectrometry cleavable cross-linker, and the known position of disulfide bonds to experimentally validate each model. We obtained 65 unique DSSO cross-links, of which 87.5% were within a 26 Å threshold in the final model. We also evaluated the positions of cysteine residues involved in the eight known disulfide bonds in apoB-100, and each pair was measured within the expected 5.6 Å constraint. Finally, multiple domains were combined by applying constraints based on detected long-range DSSO cross-links to generate five subunits, which were subsequently merged to achieve an uninterrupted architecture for apoB-100 around a lipoprotein particle. Moreover, the dynamics of apoB-100 during particle size transitions was examined by comparing VLDL and LDL computational models and using experimental cross-linking data. In addition, the proposed model of receptor ligand binding of apoB-100 provides new insights into some of its functions.
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4
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Leipart V, Ludvigsen J, Kent M, Sandve S, To TH, Árnyasi M, Kreibich CD, Dahle B, Amdam GV. Identification of 121 variants of honey bee Vitellogenin protein sequences with structural differences at functional sites. Protein Sci 2022; 31:e4369. [PMID: 35762708 PMCID: PMC9207902 DOI: 10.1002/pro.4369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Accepted: 05/21/2022] [Indexed: 12/04/2022]
Abstract
Proteins are under selection to maintain central functions and to accommodate needs that arise in ever‐changing environments. The positive selection and neutral drift that preserve functions result in a diversity of protein variants. The amount of diversity differs between proteins: multifunctional or disease‐related proteins tend to have fewer variants than proteins involved in some aspects of immunity. Our work focuses on the extensively studied protein Vitellogenin (Vg), which in honey bees (Apis mellifera) is multifunctional and highly expressed and plays roles in immunity. Yet, almost nothing is known about the natural variation in the coding sequences of this protein or how amino acid‐altering variants might impact structure–function relationships. Here, we map out allelic variation in honey bee Vg using biological samples from 15 countries. The successful barcoded amplicon Nanopore sequencing of 543 bees revealed 121 protein variants, indicating a high level of diversity in Vg. We find that the distribution of non‐synonymous single nucleotide polymorphisms (nsSNPs) differs between protein regions with different functions; domains involved in DNA and protein–protein interactions contain fewer nsSNPs than the protein's lipid binding cavities. We outline how the central functions of the protein can be maintained in different variants and how the variation pattern may inform about selection from pathogens and nutrition.
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Affiliation(s)
- Vilde Leipart
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Ås, Norway
| | - Jane Ludvigsen
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Ås, Norway.,Fürst Medisinsk Laboratorium, Oslo, Norway
| | - Matthew Kent
- Department of Animal and Aquacultural Sciences, Centre for Integrative Genetics (CIGENE), Norwegian University of Life Sciences, Ås, Norway
| | - Simen Sandve
- Department of Animal and Aquacultural Sciences, Centre for Integrative Genetics (CIGENE), Norwegian University of Life Sciences, Ås, Norway
| | - Thu-Hien To
- Department of Animal and Aquacultural Sciences, Centre for Integrative Genetics (CIGENE), Norwegian University of Life Sciences, Ås, Norway
| | - Mariann Árnyasi
- Department of Animal and Aquacultural Sciences, Centre for Integrative Genetics (CIGENE), Norwegian University of Life Sciences, Ås, Norway
| | - Claus D Kreibich
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Ås, Norway
| | - Bjørn Dahle
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Ås, Norway.,Norwegian Beekeepers Association, Kløfta, Norway
| | - Gro V Amdam
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Ås, Norway.,School of Life Sciences, Arizona State University, Tempe, Arizona, USA
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5
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Leipart V, Halskau Ø, Amdam GV. How Honey Bee Vitellogenin Holds Lipid Cargo: A Role for the C-Terminal. Front Mol Biosci 2022; 9:865194. [PMID: 35755821 PMCID: PMC9219001 DOI: 10.3389/fmolb.2022.865194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2022] [Accepted: 05/19/2022] [Indexed: 11/13/2022] Open
Abstract
Vitellogenin (Vg) is a phylogenetically broad glycolipophosphoprotein. A major function of this protein is holding lipid cargo for storage and transportation. Vg has been extensively studied in honey bees (Apis mellifera) due to additional functions in social traits. Using AlphaFold and EM contour mapping, we recently described the protein structure of honey bee Vg. The full-length protein structure reveals a large hydrophobic lipid binding site and a well-defined fold at the C-terminal region. Now, we outline a shielding mechanism that allows the C-terminal region of Vg to cover a large hydrophobic area exposed in the all-atom model. We propose that this C-terminal movement influences lipid molecules’ uptake, transport, and delivery. The mechanism requires elasticity in the Vg lipid core as described for homologous proteins in the large lipid transfer protein (LLTP) superfamily to which Vg belongs. Honey bee Vg has, additionally, several structural arrangements that we interpret as beneficial for the functional flexibility of the C-terminal region. The mechanism proposed here may be relevant for the Vg molecules of many species.
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Affiliation(s)
- Vilde Leipart
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Ås, Norway
| | - Øyvind Halskau
- Department of Biological Sciences, University of Bergen, Bergen, Norway
| | - Gro V Amdam
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Ås, Norway.,School of Life Sciences, Arizona State University, Tempe, AZ, United States
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6
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Cisse A, Schachner-Nedherer AL, Appel M, Beck C, Ollivier J, Leitinger G, Prassl R, Kornmueller K, Peters J. Dynamics of Apolipoprotein B-100 in Interaction with Detergent Probed by Incoherent Neutron Scattering. J Phys Chem Lett 2021; 12:12402-12410. [PMID: 34939807 DOI: 10.1021/acs.jpclett.1c03141] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Apolipoprotein B-100 (apo B-100) is the protein moiety of both low- and very-low-density lipoproteins, whose role is crucial to cholesterol and triglyceride transport. Aiming at the molecular dynamics' details of apo B-100, scarcely studied, we performed elastic and quasi-elastic incoherent neutron scattering (EINS, QENS) experiments combining different instruments and time scales. Similar to classical membrane proteins, the solubilization results in remaining detergent, here Nonidet P-40 (NP40). Therefore, we propose a framework for QENS studies of protein-detergent complexes, with the introduction of a combined model, including the experimental apo B-100/NP40 ratio. Relying on the simultaneous analysis of all QENS amplitudes, this approach is sensitive enough to separate both contributions. Its application identified two points: (i) apo B-100 slow dynamics and (ii) the acceleration of NP40 dynamics in the presence of apo B-100. Direct translation of the exposed methodology now makes the investigation of more membrane proteins by neutron spectroscopy achievable.
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Affiliation(s)
- Aline Cisse
- Université Grenoble Alpes, CNRS, LiPhy, 38000 Grenoble, France
- Institut Laue Langevin, 38042 Grenoble, France
| | | | | | - Christian Beck
- Institut Laue Langevin, 38042 Grenoble, France
- Institut of Applied Physics, University of Tübingen, 72076 Tübingen, Germany
| | | | | | | | | | - Judith Peters
- Université Grenoble Alpes, CNRS, LiPhy, 38000 Grenoble, France
- Institut Laue Langevin, 38042 Grenoble, France
- Institut Universitaire de France, 75231 Paris, France
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7
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Mirheydari M, Putta P, Mann EK, Kooijman EE. Interaction of Two Amphipathic α-Helix Bundle Proteins, ApoLp-III and ApoE 3, with the Oil-Aqueous Interface. J Phys Chem B 2021; 125:4746-4756. [PMID: 33939404 DOI: 10.1021/acs.jpcb.1c00271] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Protein-lipid interactions govern the structure and function of lipoprotein particles, which transport neutral lipids and other hydrophobic cargo through the blood stream. Apolipoproteins cover the surface of lipoprotein particles, including low-density (LDL) and high-density (HDL) lipoproteins, and determine their function. Previous work has focused on small peptides derived from these apolipoproteins or used such artificial lipid systems as Langmuir monolayers or the lipid disc assay to determine how apolipoproteins interact with the neutral lipid interface. Here, we focus on a recurring protein domain found in many neutral lipid-binding proteins, the amphipathic α-helix bundle. We use liquid droplet tensiometry to investigate protein-lipid interactions on an oil droplet, which mimics the real lipoprotein interface. The N-terminus of apoE 3 and full-length apoLp-III serve as model proteins. We find that each protein interacts with lipid monolayers at the oil-aqueous interface in unique ways. For the first time, we show that helix bundle unfolding is critical for proper protein insertion into the lipid monolayer at the oil-aqueous interface and that specific membrane lipids promote the rebinding of protein upon fluctuation in droplet size. These results shed new light on how amphipathic apolipoprotein α-helix bundles interact with neutral lipid particles.
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8
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Cheng Q, Zhang B, He Y, Lu Q, Kaplan DL. Silk Nanofibers as Robust and Versatile Emulsifiers. ACS APPLIED MATERIALS & INTERFACES 2017; 9:35693-35700. [PMID: 28961401 DOI: 10.1021/acsami.7b13460] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Peptides have been extensively studied as emulsifiers due to their sequence and size control, biocompatibility, versatility, and stabilizing capacity. However, cost and mass production remain the challenges for broader utility for these emulsifiers. Here we demonstrate the utility of silk fibroin nanofibers as emulsifiers, with superior functions to the more traditional peptide emulsifiers. This silk nanofiber system is universal for different oil phases with various polarities and demonstrates control of microcapsule size through tuning the ratio of silk fibroin nanofiber solutions to oils. Besides the improved stabilizing capacity to peptides, these silk fibroin nanofibers endow additional stability to the emulsions formed under high salt concentration and low pH. Highly efficient encapsulation of biomarkers through interfacial networks suggests potential applications in therapeutics, food, and cosmetics. Compared to peptide emulsifiers, these silk fibroin nanofibers offer advantages in terms of cost, purification, and production scale, without compromising biocompatibility, stabilizing capacity, and versatility.
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Affiliation(s)
- Qingqing Cheng
- College of Chemistry, Chemical Engineering and Materials Science & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University , Suzhou 215123, People's Republic of China
- Key Laboratory of Stem Cells and Biomedical Materials of Jiangsu Province and Chinese Ministry of Science and Technology, Soochow University , Suzhou 215123, People's Republic of China
| | - Bingbo Zhang
- The Institute for Advanced Materials & Nano Biomedicine, Tongji University , Shanghai 200092, People's Republic of China
| | - Yao He
- Institute of Functional Nano & Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University , Suzhou 215123, People's Republic of China
| | - Qiang Lu
- College of Chemistry, Chemical Engineering and Materials Science & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University , Suzhou 215123, People's Republic of China
- Key Laboratory of Stem Cells and Biomedical Materials of Jiangsu Province and Chinese Ministry of Science and Technology, Soochow University , Suzhou 215123, People's Republic of China
- National Engineering Laboratory for Modern Silk, Soochow University , Suzhou 215123, People's Republic of China
| | - David L Kaplan
- Department of Biomedical Engineering, Tufts University , Medford, Massachusetts 02155, United States
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9
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Mirheydari M, Mann EK, Kooijman EE. Interaction of a model apolipoprotein, apoLp-III, with an oil-phospholipid interface. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:396-406. [PMID: 29030246 DOI: 10.1016/j.bbamem.2017.10.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 09/22/2017] [Accepted: 10/08/2017] [Indexed: 01/29/2023]
Abstract
Lipid droplets are "small" organelles that play an important role in de novo synthesis of new membrane, and steroid hormones, as well as in energy storage. The way proteins interact specifically with the oil-(phospho-)lipid monolayer interface of lipid droplets is a relatively unexplored but crucial question. Here, we use our home built liquid droplet tensiometer to mimic intracellular lipid droplets and study protein-lipid interactions at this interface. As model neutral lipid binding protein, we use apoLp-III, an amphipathic α-helix bundle protein. This domain is also found in proteins from the perilipin family and in apoE. Protein binding to the monolayer is studied by the decrease in the oil/water surface tension. Previous work used POPC (one of the major lipids found on lipid droplets) to form the phospholipid monolayer on the triolein surface. Here we expand this work by incorporating other lipids with different physico-chemical properties to study the effect of charge and lipid head-group size. This study sheds light on the affinity of this important protein domain to interact with lipids.
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Affiliation(s)
- Mona Mirheydari
- Physics Department, Kent State University, Kent, OH 44242, United States.
| | - Elizabeth K Mann
- Physics Department, Kent State University, Kent, OH 44242, United States
| | - Edgar E Kooijman
- Department of Biological Sciences, Kent State University, Kent, OH 44242, United States
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10
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Golub M, Lehofer B, Martinez N, Ollivier J, Kohlbrecher J, Prassl R, Peters J. High hydrostatic pressure specifically affects molecular dynamics and shape of low-density lipoprotein particles. Sci Rep 2017; 7:46034. [PMID: 28382948 PMCID: PMC5382586 DOI: 10.1038/srep46034] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 03/08/2017] [Indexed: 12/12/2022] Open
Abstract
Lipid composition of human low-density lipoprotein (LDL) and its physicochemical characteristics are relevant for proper functioning of lipid transport in the blood circulation. To explore dynamical and structural features of LDL particles with either a normal or a triglyceride-rich lipid composition we combined coherent and incoherent neutron scattering methods. The investigations were carried out under high hydrostatic pressure (HHP), which is a versatile tool to study the physicochemical behavior of biomolecules in solution at a molecular level. Within both neutron techniques we applied HHP to probe the shape and degree of freedom of the possible motions (within the time windows of 15 and 100 ps) and consequently the flexibility of LDL particles. We found that HHP does not change the types of motion in LDL, but influences the portion of motions participating. Contrary to our assumption that lipoprotein particles, like membranes, are highly sensitive to pressure we determined that LDL copes surprisingly well with high pressure conditions, although the lipid composition, particularly the triglyceride content of the particles, impacts the molecular dynamics and shape arrangement of LDL under pressure.
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Affiliation(s)
- M. Golub
- Univ. Grenoble Alpes, IBS, Grenoble, F-38000, France
- Institut Laue Langevin, Grenoble, F-38000, France
| | - B. Lehofer
- Institute of Biophysics, Medical University of Graz, Graz, A-8010, Austria
| | - N. Martinez
- Univ. Grenoble Alpes, IBS, Grenoble, F-38000, France
- Institut Laue Langevin, Grenoble, F-38000, France
| | - J. Ollivier
- Institut Laue Langevin, Grenoble, F-38000, France
| | | | - R. Prassl
- Institute of Biophysics, Medical University of Graz, Graz, A-8010, Austria
| | - J. Peters
- Institut Laue Langevin, Grenoble, F-38000, France
- Univ. Grenoble Alpes, LiPhy, Grenoble, F-38044, France
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11
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Maric S, Lind TK, Lyngsø J, Cárdenas M, Pedersen JS. Modeling Small-Angle X-ray Scattering Data for Low-Density Lipoproteins: Insights into the Fatty Core Packing and Phase Transition. ACS NANO 2017; 11:1080-1090. [PMID: 28048943 DOI: 10.1021/acsnano.6b08089] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Atherosclerosis and its clinical consequences are the leading cause of death in the western hemisphere. While many studies throughout the last decades have aimed at understanding the disease, the clinical markers in use today still fail to accurately predict the risks. The role of the current main clinical indicator, low density lipoprotein (LDL), in depositing fat to the vessel wall is believed to be the onset of the process. However, many subfractions of the LDL, which differ both in structure and composition, are present in the blood and among different individuals. Understanding the relationship between LDL structure and composition is key to unravel the specific role of various LDL components in the development and/or prevention of atherosclerosis. Here, we describe a model for analyzing small-angle X-ray scattering data for rapid and robust structure determination for the LDL. The model not only gives the overall structure but also the particular internal layering of the fats inside the LDL core. Thus, the melting of the LDL can be followed in situ as a function of temperature for samples extracted from healthy human patients and purified using a double protocol based on ultracentrifugation and size-exclusion chromatography. The model provides information on: (i) the particle-specific melting temperature of the core lipids, (ii) the structural organization of the core fats inside the LDL, (iii) the overall shape of the particle, and (iv) the flexibility and overall conformation of the outer protein/hydrophilic layer at a given temperature as governed by the organization of the core. The advantage of this method over other techniques such as cryo-TEM is the possibility of in situ experiments under near-physiological conditions which can be performed relatively fast (minutes at home source, seconds at synchrotron). This approach now allows the monitoring of structural changes in the LDL upon different stresses from the environment, such as changes in temperature, oxidation, or external agents used or currently in development against atherosclerotic plaque build-up and which are targeting the LDL.
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Affiliation(s)
- Selma Maric
- Biofilms- Research Center for Biointerfaces, Dept. of Biomedical Science, Faculty of Health and Society, Malmö University , Malmö 20506, Sweden
| | - Tania Kjellerup Lind
- Biofilms- Research Center for Biointerfaces, Dept. of Biomedical Science, Faculty of Health and Society, Malmö University , Malmö 20506, Sweden
| | - Jeppe Lyngsø
- Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University , 8000 Aarhus, Denmark
| | - Marité Cárdenas
- Biofilms- Research Center for Biointerfaces, Dept. of Biomedical Science, Faculty of Health and Society, Malmö University , Malmö 20506, Sweden
| | - Jan Skov Pedersen
- Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University , 8000 Aarhus, Denmark
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12
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Mondal S, Varenik M, Bloch DN, Atsmon-Raz Y, Jacoby G, Adler-Abramovich L, Shimon LJ, Beck R, Miller Y, Regev O, Gazit E. A minimal length rigid helical peptide motif allows rational design of modular surfactants. Nat Commun 2017; 8:14018. [PMID: 28084315 PMCID: PMC5241864 DOI: 10.1038/ncomms14018] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2016] [Accepted: 11/15/2016] [Indexed: 01/12/2023] Open
Abstract
Extensive work has been invested in the design of bio-inspired peptide emulsifiers. Yet, none of the formulated surfactants were based on the utilization of the robust conformation and self-assembly tendencies presented by the hydrophobins, which exhibited highest surface activity among all known proteins. Here we show that a minimalist design scheme could be employed to fabricate rigid helical peptides to mimic the rigid conformation and the helical amphipathic organization. These designer building blocks, containing natural non-coded α-aminoisobutyric acid (Aib), form superhelical assemblies as confirmed by crystallography and microscopy. The peptide sequence is amenable to structural modularity and provides the highest stable emulsions reported so far for peptide and protein emulsifiers. Moreover, we establish the ability of short peptides to perform the dual functions of emulsifiers and thickeners, a feature that typically requires synergistic effects of surfactants and polysaccharides. This work provides a different paradigm for the molecular engineering of bioemulsifiers. Emulsifiers are used in the pharmaceutical, food, cosmetic, and biomedical industry. Here the authors fabricate rigid helical peptides that can perform as emulsifiers and thickeners, which typically requires synergistic effects of surfactants and polysaccharides.
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13
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Lipoprotein interactions with a polyurethane and a polyethylene oxide-modified polyurethane at the plasma–material interface. Biointerphases 2016; 11:029810. [PMID: 27306077 DOI: 10.1116/1.4953867] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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14
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Morita SY. Metabolism and Modification of Apolipoprotein B-Containing Lipoproteins Involved in Dyslipidemia and Atherosclerosis. Biol Pharm Bull 2016; 39:1-24. [DOI: 10.1248/bpb.b15-00716] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Shin-ya Morita
- Department of Pharmacy, Shiga University of Medical Science Hospital
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15
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Cornelius RM, Macri J, Cornelius KM, Brash JL. Interactions of Apolipoproteins AI, AII, B and HDL, LDL, VLDL with Polyurethane and Polyurethane-PEO Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:12087-12095. [PMID: 26513526 DOI: 10.1021/acs.langmuir.5b02688] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The lipoproteins (HDL, LDL, VLDL) are important components of blood present in high concentration. Surprisingly, their role in blood-biomaterial interactions has been largely ignored. In previous work apolipoprotein AI (the main protein component of HDL) was identified as a major constituent of protein layers adsorbed from plasma to biomaterials having a wide range of surface properties, and quantitative data on the adsorption of apo AI to a biomedical grade polyurethane were reported. In the present communication quantitative data on the adsorption of apo AI, apo AII and apoB (the latter being a constituent of LDL and VLDL), as well as the lipoprotein particles themselves (HDL, LDL, VLDL), to a biomedical segmented polyurethane (PU) with and without an additive containing poly(ethylene oxide) (material referred to as PEO) are reported. Using radiolabeled apo AI, apo AII, and apoB, adsorption levels on PU from buffer at a protein concentration of 50 μg/mL were found to be 0.34, 0.40, and 0.14 μg/cm(2) (12, 23, and 0.25 nmol/cm(2)) respectively. Adsorption to the PEO surface was <0.02 μg/cm(2) for all three apolipoproteins demonstrating the strong protein resistance of this material. In contrast to the apolipoproteins, significant amounts of the lipoproteins were found to adsorb to the PEO as well as to the PU surface. X-ray photoelectron spectra, following exposure of the surfaces to the lipoproteins, showed a strong phosphorus signal, confirming that adsorption had occurred. It therefore appears that a PEO-containing surface that is resistant to apolipoproteins may be less resistant to the corresponding lipoproteins.
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Affiliation(s)
- R M Cornelius
- Department of Chemical Engineering ‡Department of Pathology & Molecular Medicine §Department of Biology ∥School of Biomedical Engineering McMaster University Hamilton, Ontario Canada
| | - J Macri
- Department of Chemical Engineering ‡Department of Pathology & Molecular Medicine §Department of Biology ∥School of Biomedical Engineering McMaster University Hamilton, Ontario Canada
| | - K M Cornelius
- Department of Chemical Engineering ‡Department of Pathology & Molecular Medicine §Department of Biology ∥School of Biomedical Engineering McMaster University Hamilton, Ontario Canada
| | - J L Brash
- Department of Chemical Engineering ‡Department of Pathology & Molecular Medicine §Department of Biology ∥School of Biomedical Engineering McMaster University Hamilton, Ontario Canada
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16
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Nguyen SD, Javanainen M, Rissanen S, Zhao H, Huusko J, Kivelä AM, Ylä-Herttuala S, Navab M, Fogelman AM, Vattulainen I, Kovanen PT, Öörni K. Apolipoprotein A-I mimetic peptide 4F blocks sphingomyelinase-induced LDL aggregation. J Lipid Res 2015; 56:1206-21. [PMID: 25861792 DOI: 10.1194/jlr.m059485] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Indexed: 12/23/2022] Open
Abstract
Lipolytic modification of LDL particles by SMase generates LDL aggregates with a strong affinity for human arterial proteoglycans and may so enhance LDL retention in the arterial wall. Here, we evaluated the effects of apoA-I mimetic peptide 4F on structural and functional properties of the SMase-modified LDL particles. LDL particles with and without 4F were incubated with SMase, after which their aggregation, structure, and proteoglycan binding were analyzed. At a molar ratio of L-4F to apoB-100 of 2.5 to 20:1, 4F dose-dependently inhibited SMase-induced LDL aggregation. At a molar ratio of 20:1, SMase-induced aggregation was fully blocked. Binding of 4F to LDL particles inhibited SMase-induced hydrolysis of LDL by 10% and prevented SMase-induced LDL aggregation. In addition, the binding of the SMase-modified LDL particles to human aortic proteoglycans was dose-dependently inhibited by pretreating LDL with 4F. The 4F stabilized apoB-100 conformation and inhibited SMase-induced conformational changes of apoB-100. Molecular dynamic simulations showed that upon binding to protein-free LDL surface, 4F locally alters membrane order and fluidity and induces structural changes to the lipid layer. Collectively, 4F stabilizes LDL particles by preventing the SMase-induced conformational changes in apoB-100 and so blocks SMase-induced LDL aggregation and the resulting increase in LDL retention.
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Affiliation(s)
- Su Duy Nguyen
- Wihuri Research Institute, Biomedicum Helsinki, Helsinki, Finland
| | - Matti Javanainen
- Department of Physics, Tampere University of Technology, Tampere, Finland
| | - Sami Rissanen
- Department of Physics, Tampere University of Technology, Tampere, Finland
| | - Hongxia Zhao
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Jenni Huusko
- A.I. Virtanen Institute for Molecular Sciences, Department of Biotechnology and Molecular Medicine, University of Eastern Finland, Kuopio, Finland
| | - Annukka M Kivelä
- A.I. Virtanen Institute for Molecular Sciences, Department of Biotechnology and Molecular Medicine, University of Eastern Finland, Kuopio, Finland
| | - Seppo Ylä-Herttuala
- A.I. Virtanen Institute for Molecular Sciences, Department of Biotechnology and Molecular Medicine, University of Eastern Finland, Kuopio, Finland Science Service Center, Kuopio University Hospital, Kuopio, Finland
| | - Mohamad Navab
- Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - Alan M Fogelman
- Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - Ilpo Vattulainen
- Department of Physics, Tampere University of Technology, Tampere, Finland MEMPHYS-Center for Biomembrane Physics, University of Southern Denmark, Odense, Denmark
| | - Petri T Kovanen
- Wihuri Research Institute, Biomedicum Helsinki, Helsinki, Finland
| | - Katariina Öörni
- Wihuri Research Institute, Biomedicum Helsinki, Helsinki, Finland
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17
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Fernández-Higuero JA, Salvador AM, Martín C, Milicua JCG, Arrondo JLR. Human LDL structural diversity studied by IR spectroscopy. PLoS One 2014; 9:e92426. [PMID: 24642788 PMCID: PMC3958539 DOI: 10.1371/journal.pone.0092426] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Accepted: 02/21/2014] [Indexed: 12/20/2022] Open
Abstract
Lipoproteins are responsible for cholesterol traffic in humans. Low density lipoprotein (LDL) delivers cholesterol from liver to peripheral tissues. A misleading delivery can lead to the formation of atherosclerotic plaques. LDL has a single protein, apoB-100, that binds to a specific receptor. It is known that the failure associated with a deficient protein-receptor binding leads to plaque formation. ApoB-100 is a large single lipid-associated polypeptide difficulting the study of its structure. IR spectroscopy is a technique suitable to follow the different conformational changes produced in apoB-100 because it is not affected by the size of the protein or the turbidity of the sample. We have analyzed LDL spectra of different individuals and shown that, even if there are not big structural changes, a different pattern in the intensity of the band located around 1617 cm−1 related with strands embedded in the lipid monolayer, can be associated with a different conformational rearrangement that could affect to a protein interacting region with the receptor.
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Affiliation(s)
- José A. Fernández-Higuero
- Unidad de Biofísica (CSIC, UPV/EHU) and Departamento de Bioquímica y Biología Molecular, Universidad del País Vasco, Bilbao, Spain
| | - Ana M. Salvador
- Unidad de Biofísica (CSIC, UPV/EHU) and Departamento de Bioquímica y Biología Molecular, Universidad del País Vasco, Bilbao, Spain
| | - Cesar Martín
- Unidad de Biofísica (CSIC, UPV/EHU) and Departamento de Bioquímica y Biología Molecular, Universidad del País Vasco, Bilbao, Spain
| | - José Carlos G. Milicua
- Departamento de Bioquímica y Biología Molecular, Universidad del País Vasco, Bilbao, Spain
| | - José L. R. Arrondo
- Unidad de Biofísica (CSIC, UPV/EHU) and Departamento de Bioquímica y Biología Molecular, Universidad del País Vasco, Bilbao, Spain
- * E-mail:
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18
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Reynolds L, Mulik RS, Wen X, Dilip A, Corbin IR. Low-density lipoprotein-mediated delivery of docosahexaenoic acid selectively kills murine liver cancer cells. Nanomedicine (Lond) 2014; 9:2123-41. [PMID: 24397600 DOI: 10.2217/nnm.13.187] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
AIM The natural omega-3 polyunsaturated fatty acid, docosahexaenoic acid (DHA), has recently been credited for possessing anticancer properties. Herein, we investigate the cytotoxic actions of DHA-loaded low-density lipoprotein (LDL) nanoparticles in normal and liver cancer cells. MATERIALS & METHODS LDL-DHA nanoparticles were prepared and subjected to extensive biophysical characterization. The therapeutic utility of LDL-DHA nanoparticles was evaluated in normal and malignant murine hepatocyte cell lines, TIB-73 and TIB-75, respectively. RESULTS & DISCUSSION The engineered LDL-DHA nanoparticles possessed enhanced physical and oxidative stabilities over native LDL and free DHA. Dose-response studies showed that therapeutic doses of LDL-DHA nanoparticles that completely killed TIB-75 were innocuous to TIB-73. The selective induction of lipid peroxidation and reactive oxygen species in the cancer cells was shown to play a central role in LDL-DHA nanoparticle-mediated cytotoxicity. CONCLUSION In summary, these findings indicate that LDL-DHA nanoparticles show great promise as a selective anticancer agent against hepatocellular carcinoma.
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Affiliation(s)
- Lacy Reynolds
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
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19
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Koivuniemi A, Sysi-Aho M, Orešič M, Ollila S. Interfacial properties of high-density lipoprotein-like lipid droplets with different lipid and apolipoprotein A-I compositions. Biophys J 2013; 104:2193-201. [PMID: 23708359 DOI: 10.1016/j.bpj.2013.02.058] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Revised: 02/06/2013] [Accepted: 02/14/2013] [Indexed: 01/22/2023] Open
Abstract
The surface properties of high-density lipoproteins (HDLs) are important because different enzymes bind and carry out their functions at the surface of HDL particles during metabolic processes. However, the surface properties of HDL and other lipoproteins are poorly known because they cannot be directly measured for nanoscale particles with contemporary experimental methods. In this work, we carried out coarse-grained molecular dynamics simulations to study the concentration of core lipids in the surface monolayer and the interfacial tension of droplets resembling HDL particles. We simulated lipid droplets composed of different amounts of phospholipids, cholesterol esters (CEs), triglycerides (TGs), and apolipoprotein A-Is. Our results reveal that the amount of TGs in the vicinity of water molecules in the phospholipid monolayer is 25-50% higher compared to the amount of CEs in a lipid droplet with a mixed core of an equal amount of TG and CE. In addition, the correlation time for the exchange of molecules between the core and the monolayer is significantly longer for TGs compared to CEs. This suggests that the chemical potential of TG is lower in the vicinity of aqueous phase but the free-energy barrier for the translocation between the monolayer and the core is higher compared to CEs. From the point of view of enzymatic modification, this indicates that TG molecules are more accessible from the aqueous phase. Further, our results point out that CE molecules decrease the interfacial tension of HDL-like lipid droplets whereas TG keeps it constant while the amount of phospholipids varies.
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20
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Wang L, Mei X, Atkinson D, Small DM. Surface behavior of apolipoprotein A-I and its deletion mutants at model lipoprotein interfaces. J Lipid Res 2013; 55:478-92. [PMID: 24308948 DOI: 10.1194/jlr.m044743] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Apolipoprotein A-I (apoA-I) has a great conformational flexibility to exist in lipid-free, lipid-poor, and lipid-bound states during lipid metabolism. To address the lipid binding and the dynamic desorption behavior of apoA-I at lipoprotein surfaces, apoA-I, Δ(185-243)apoA-I, and Δ(1-59)(185-243)apoA-I were studied at triolein/water and phosphatidylcholine/triolein/water interfaces with special attention to surface pressure. All three proteins are surface active to both interfaces lowering the interfacial tension and thus increasing the surface pressure to modify the interfaces. Δ(185-243)apoA-I adsorbs much more slowly and lowers the interfacial tension less than full-length apoA-I, confirming that the C-terminal domain (residues 185-243) initiates the lipid binding. Δ(1-59)(185-243)apoA-I binds more rapidly and lowers the interfacial tension more than Δ(185-243)apoA-I, suggesting that destabilizing the N-terminal α-helical bundle (residues 1-185) restores lipid binding. The three proteins desorb from both interfaces at different surface pressures revealing that different domains of apoA-I possess different lipid affinity. Δ(1-59)(185-243)apoA-I desorbs at lower pressures compared with apoA-I and Δ(185-243)apoA-I indicating that it is missing a strong lipid association motif. We propose that during lipoprotein remodeling, surface pressure mediates the adsorption and partial or full desorption of apoA-I allowing it to exchange among different lipoproteins and adopt various conformations to facilitate its multiple functions.
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Affiliation(s)
- Libo Wang
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118
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21
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Vindigni JD, Wien F, Giuliani A, Erpapazoglou Z, Tache R, Jagic F, Chardot T, Gohon Y, Froissard M. Fold of an oleosin targeted to cellular oil bodies. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:1881-8. [DOI: 10.1016/j.bbamem.2013.04.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Revised: 03/26/2013] [Accepted: 04/09/2013] [Indexed: 01/18/2023]
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23
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C-terminus of apolipoprotein A-I removes phospholipids from a triolein/phospholipids/water interface, but the N-terminus does not: a possible mechanism for nascent HDL assembly. Biophys J 2011; 101:353-61. [PMID: 21767487 DOI: 10.1016/j.bpj.2011.03.055] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Revised: 02/10/2011] [Accepted: 03/15/2011] [Indexed: 01/12/2023] Open
Abstract
Apolipoprotein A-I (ApoA-I) is the principle protein component of HDL, also known as "good cholesterol," which is an inverse marker for cardiovascular disease. The N-terminal 44 amino acids of ApoA-I (N44) are predicted to be responsible for stabilization of soluble ApoA-I, whereas the C-terminal 46 amino acids (C46) are predicted to initiate lipid binding and oligomerization. In this work, we apply what we believe to be a novel application of drop tensiometry to study the adsorption and desorption of N44 and C46 at a triolein/POPC/water (TO/POPC/W) interface. The amount of peptide that adsorbed to the surface was dependent on the surface concentration of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and pressure (Π) before adsorption. At a TO/POPC/W interface, the exclusion pressure (Π(EX)) of C46 was 25.8 mN/m, and was 19.3 mN/m for N44. Once adsorbed, both peptides formed a homogeneous surface with POPC but were progressively ejected from the surface by compression. During a compression, C46 removed POPC from the surface whereas N44 did not. Repeated compressions caused C46 to deplete entirely the surface of phospholipid. If full-length ApoA-I could also remove phospholipid, this could provide a mechanism for the transfer of surface components of chylomicrons and very low density lipoprotein to high density lipoprotein with the assistance of phospholipid transfer protein.
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24
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Mikl C, Peters J, Trapp M, Kornmueller K, Schneider WJ, Prassl R. Softness of atherogenic lipoproteins: a comparison of very low density lipoprotein (VLDL) and low density lipoprotein (LDL) using elastic incoherent neutron scattering (EINS). J Am Chem Soc 2011; 133:13213-5. [PMID: 21790144 DOI: 10.1021/ja203679g] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Apolipoprotein B100 (apoB100)-containing plasma lipoproteins (LDL and VLDL) supply tissues and cells with cholesterol and fat. During lipolytic conversion from VLDL to LDL the size and chemical composition of the particles change, but the apoB100 molecule remains bound to the lipids and regulates the receptor mediated uptake. The molecular physical parameters which control lipoprotein remodeling and enable particle stabilization by apoB100 are largely unknown. Here, we have compared the molecular dynamics and elasticities of VLDL and LDL derived by elastic neutron scattering temperature scans. We have determined thermal motions, dynamical transitions, and molecular fluctuations, which reflect the temperature-dependent motional coupling between lipid and protein. Our results revealed that lipoprotein particles are extremely soft and flexible. We found substantial differences in the molecular resiliences of lipoproteins, especially at higher temperatures. These discrepancies not only can be explained in terms of lipid composition and mobility but also suggest that apoB100 displays different dynamics dependent on the lipoprotein it is bound to. Hence, we suppose that the inherent conformational flexibility of apoB100 permits particle stabilization upon lipid exchange, whereas the dynamic coupling between protein and lipids might be a key determinant for lipoprotein conversion and atherogenicity.
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Affiliation(s)
- Christian Mikl
- Institute of Biophysics and Nanosystems Research, Austrian Academy of Sciences, Graz, Austria
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25
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Kumar V, Butcher SJ, Öörni K, Engelhardt P, Heikkonen J, Kaski K, Ala-Korpela M, Kovanen PT. Three-dimensional cryoEM reconstruction of native LDL particles to 16Å resolution at physiological body temperature. PLoS One 2011; 6:e18841. [PMID: 21573056 PMCID: PMC3090388 DOI: 10.1371/journal.pone.0018841] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Accepted: 03/21/2011] [Indexed: 11/20/2022] Open
Abstract
Background Low-density lipoprotein (LDL) particles, the major carriers of cholesterol in the human circulation, have a key role in cholesterol physiology and in the development of atherosclerosis. The most prominent structural components in LDL are the core-forming cholesteryl esters (CE) and the particle-encircling single copy of a huge, non-exchangeable protein, the apolipoprotein B-100 (apoB-100). The shape of native LDL particles and the conformation of native apoB-100 on the particles remain incompletely characterized at the physiological human body temperature (37°C). Methodology/Principal Findings To study native LDL particles, we applied cryo-electron microscopy to calculate 3D reconstructions of LDL particles in their hydrated state. Images of the particles vitrified at 6°C and 37°C resulted in reconstructions at ∼16 Å resolution at both temperatures. 3D variance map analysis revealed rigid and flexible domains of lipids and apoB-100 at both temperatures. The reconstructions showed less variability at 6°C than at 37°C, which reflected increased order of the core CE molecules, rather than decreased mobility of the apoB-100. Compact molecular packing of the core and order in a lipid-binding domain of apoB-100 were observed at 6°C, but not at 37°C. At 37°C we were able to highlight features in the LDL particles that are not clearly separable in 3D maps at 6°C. Segmentation of apoB-100 density, fitting of lipovitellin X-ray structure, and antibody mapping, jointly revealed the approximate locations of the individual domains of apoB-100 on the surface of native LDL particles. Conclusions/Significance Our study provides molecular background for further understanding of the link between structure and function of native LDL particles at physiological body temperature.
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Affiliation(s)
- Vibhor Kumar
- Department of Biomedical Engineering and Computational Science, School of Science and Technology, Centre of Excellence in Computational Complex Systems Research, Aalto University Aalto, Finland
- Computational and Mathematical Biology, Genome Institute of Singapore, A*STAR, Singapore
| | - Sarah J. Butcher
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Katariina Öörni
- Wihuri Research Institute, Kalliolinnantie 4, Helsinki, Finland
| | - Peter Engelhardt
- Department of Biomedical Engineering and Computational Science, School of Science and Technology, Centre of Excellence in Computational Complex Systems Research, Aalto University Aalto, Finland
- Department of Pathology, Haartman Institute, Haartmaninkatu 3, University of Helsinki, Helsinki, Finland
- Department of Applied Physics, Nanomicroscopy Center, School of Science and Technology, Puumiehenkuja 2, Aalto University, Espoo, Finland
| | - Jukka Heikkonen
- Department of Biomedical Engineering and Computational Science, School of Science and Technology, Centre of Excellence in Computational Complex Systems Research, Aalto University Aalto, Finland
- Department of Information Technology, University of Turku, Turku, Finland
| | - Kimmo Kaski
- Department of Biomedical Engineering and Computational Science, School of Science and Technology, Centre of Excellence in Computational Complex Systems Research, Aalto University Aalto, Finland
| | - Mika Ala-Korpela
- Computational Medicine Research Group, Institute of Clinical Medicine, Faculty of Medicine, Biocenter Oulu, University of Oulu, Oulu, Finland
- Department of Internal Medicine and Biocenter Oulu, Clinical Research Center, University of Oulu, Oulu, Finland
| | - Petri T. Kovanen
- Wihuri Research Institute, Kalliolinnantie 4, Helsinki, Finland
- * E-mail:
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26
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Liu Y, Atkinson D. Immuno-electron cryo-microscopy imaging reveals a looped topology of apoB at the surface of human LDL. J Lipid Res 2011; 52:1111-1116. [PMID: 21460103 DOI: 10.1194/jlr.m013946] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A single copy of apoB is the sole protein component of human LDL. ApoB is crucial for LDL particle stabilization and is the ligand for LDL receptor, through which cholesterol is delivered to cells. Dysregulation of the pathways of LDL metabolism is well documented in the pathophysiology of atherosclerosis. However, an understanding of the structure of LDL and apoB underlying these biological processes remains limited. In this study, we derived a 22 Å-resolution three-dimensional (3D) density map of LDL using cryo-electron microscopy and image reconstruction, which showed a backbone of high-density regions that encircle the LDL particle. Additional high-density belts complemented this backbone high density to enclose the edge of the LDL particle. Image reconstructions of monoclonal antibody-labeled LDL located six epitopes in five putative domains of apoB in 3D. Epitopes in the LDL receptor binding domain were located on one side of the LDL particle, and epitopes in the N-terminal and C-terminal domains of apoB were in close proximity at the front side of the particle. Such image information revealed a looped topology of apoB on the LDL surface and demonstrated the active role of apoB in maintaining the shape of the LDL particle.
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Affiliation(s)
- Yuhang Liu
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118
| | - David Atkinson
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118.
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Jayaraman S, Gantz DL, Gursky O. Effects of phospholipase A(2) and its products on structural stability of human LDL: relevance to formation of LDL-derived lipid droplets. J Lipid Res 2011; 52:549-57. [PMID: 21220788 DOI: 10.1194/jlr.m012567] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Hydrolysis and oxidation of LDL stimulate LDL entrapment in the arterial wall and promote inflammation and atherosclerosis via various mechanisms including lipoprotein fusion and lipid droplet formation. To determine the effects of FFA on these transitions, we hydrolyzed LDL by phospholipase A(2) (PLA(2)), removed FFA by albumin, and analyzed structural stability of the modified lipoproteins. Earlier, we showed that heating induces LDL remodeling, rupture, and coalescence into lipid droplets resembling those found in atherosclerotic lesions. Here, we report how FFA affect these transitions. Circular dichroism showed that mild LDL lipolysis induces partial β-sheet unfolding in apolipoprotein B. Electron microscopy, turbidity, and differential scanning calorimetry showed that mild lipolysis promotes LDL coalescence into lipid droplets. FFA removal by albumin restores LDL stability but not the protein conformation. Consequently, FFA enhance LDL coalescence into lipid droplets. Similar effects of FFA were observed in minimally oxidized LDL, in LDL enriched with exogenous FFA, and in HDL and VLDL. Our results imply that FFA promote lipoprotein coalescence into lipid droplets and explain why LDL oxidation enhances such coalescence in vivo but hampers it in vitro. Such lipid droplet formation potentially contributes to the pro-atherogenic effects of FFA.
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Affiliation(s)
- Shobini Jayaraman
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118, USA.
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28
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Bonsegna S, Bettini S, Pagano R, Zacheo A, Vergaro V, Giovinazzo G, Caminati G, Leporatti S, Valli L, Santino A. Plant Oil Bodies: Novel Carriers to Deliver Lipophilic Molecules. Appl Biochem Biotechnol 2010; 163:792-802. [DOI: 10.1007/s12010-010-9083-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2010] [Accepted: 09/07/2010] [Indexed: 10/19/2022]
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Wang L, Jiang ZG, McKnight CJ, Small DM. Interfacial properties of apolipoprotein B292-593 (B6.4-13) and B611-782 (B13-17). Insights into the structure of the lipovitellin homology region in apolipoprotein B. Biochemistry 2010; 49:3898-907. [PMID: 20353182 DOI: 10.1021/bi100056v] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The N-terminal sequence of apolipoprotein B (apoB) is critical in triacylglycerol-rich lipoprotein assembly. The first 17% of apoB (B17) is thought to consist of three domains: B5.9, a beta-barrel, B6.4-13, a series of 17 alpha-helices, and B13-17, a putative beta-sheet. B5.9 does not bind to lipid, while B6.4-13 and B13-17 contain hydrophobic interfaces that can interact with lipids. To understand how B6.4-13 and B13-17 might interact with triacylglycerol during lipoprotein assembly, the interfacial properties of both peptides were studied at the triolein/water interface. Both B6.4-13 and B13-17 are surface active. Once bound, the peptides can be neither exchanged nor pushed off the interface. Some residues of the peptides can be ejected from the interface upon compression but readsorb on expansion. B13-17 binds to the interface more strongly. The maximum pressure the peptide can withstand without being partially ejected (Pi(max)) is 19.2 mN/m for B13-17 compared to 16.7 mN/m for B6.4-13. B13-17 is purely elastic at the interface, while B6.4-13 forms a viscous-elastic film. When they are spread at an air/water interface, the limiting area and the collapse pressures are 16.6 A(2)/amino acid and 31 mN/m for B6.4-13 and 17.8 A(2)/amino acid and 35 mN/m for B13-17, respectively. The alpha-helical B6.4-13 contains some hydrophobic helices that stay bound and prevent the peptide from leaving the surface. The beta-sheets of B13-17 bind irreversibly to the surface. We suggest that during lipoprotein assembly, the N-terminal apoB starts recruiting lipid as early as B6.4, but additional sequences are essential for formation of a lipid pocket that can stabilize lipoprotein emulsion particles for secretion.
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Affiliation(s)
- Libo Wang
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts 02118, USA
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30
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Sundaram M, Yao Z. Recent progress in understanding protein and lipid factors affecting hepatic VLDL assembly and secretion. Nutr Metab (Lond) 2010; 7:35. [PMID: 20423497 PMCID: PMC2873297 DOI: 10.1186/1743-7075-7-35] [Citation(s) in RCA: 118] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Accepted: 04/27/2010] [Indexed: 02/06/2023] Open
Abstract
Excess lipid induced metabolic disorders are one of the major existing challenges for the society. Among many different causes of lipid disorders, overproduction and compromised catabolism of triacylglycerol-rich very low density lipoproteins (VLDL) have become increasingly prevalent leading to hyperlipidemia worldwide. This review provides the latest understanding in different aspects of VLDL assembly process, including structure-function relationships within apoB, mutations in APOB causing hypobetalipoproteinemia, significance of modulating microsomal triglyceride-transfer protein activity in VLDL assembly, alterations of VLDL assembly by different fatty acid species, and hepatic proteins involved in vesicular trafficking, and cytosolic lipid droplet metabolism that contribute to VLDL assembly. The role of lipoprotein receptors and exchangeable apolipoproteins that promote or diminish VLDL assembly and secretion is discussed. New understanding on dysregulated insulin signaling as a consequence of excessive triacylglycerol-rich VLDL in the plasma is also presented. It is hoped that a comprehensive view of protein and lipid factors that contribute to molecular and cellular events associated with VLDL assembly and secretion will assist in the identification of pharmaceutical targets to reduce disease complications related to hyperlipidemia.
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Affiliation(s)
- Meenakshi Sundaram
- Department of Biochemistry, Microbiology and Immunology, Ottawa Institute of Systems Biology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada
| | - Zemin Yao
- Department of Biochemistry, Microbiology and Immunology, Ottawa Institute of Systems Biology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada
- Department of Pathology and Laboratory Medicine, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada
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31
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Guevara J, Prashad N, Ermolinsky B, Gaubatz JW, Kang D, Schwarzbach AE, Loose DS, Guevara NV. Apo B100 similarities to viral proteins suggest basis for LDL-DNA binding and transfection capacity. J Lipid Res 2010; 51:1704-18. [PMID: 20173184 DOI: 10.1194/jlr.m003277] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
LDL mediates transfection with plasmid DNA in a variety of cell types in vitro and in several tissues in vivo in the rat. The transfection capacity of LDL is based on apo B100, as arginine/lysine clusters, suggestive of nucleic acid-binding domains and nuclear localization signal sequences, are present throughout the molecule. Apo E may also contribute to this capacity because of its similarity to the Dengue virus capsid proteins and its ability to bind DNA. Synthetic peptides representing two apo B100 regions with prominent Arg/Lys clusters were shown to bind DNA. Region 1 (0014Lys-Ser0160) shares sequence motifs present in DNA binding domains of Interferon Regulatory Factors and Flaviviridae capsid/core proteins. It also contains a close analog of the B/E receptor ligand of apo E. Region 1 peptides, B1-1 (0014Lys-Glu0054) and B1-2 (0055Leu-Ala0096), mediate transfection of HeLa cells but are cytotoxic. Region 2 (3313Asp-Thr3431), containing the known B/E receptor ligand, shares analog motifs with the human herpesvirus 5 immediate-early transcriptional regulator (UL122) and Flaviviridae NS3 helicases. Region 2 peptides, B2-1 (3313Asp-Glu3355), and B2-2 (3356Gly-Thr3431) are ineffective in cell transfection and are noncytotoxic. These results confirm the role of LDL as a natural transfection vector in vivo, a capacity imparted by the apo B100, and suggest a basis for Flaviviridae cell entry.
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Affiliation(s)
- Juan Guevara
- Department of Physics and Astronomy, University of Texas Brownsville/Texas Southmost College, Brownsville, TX 78520, USA
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32
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Davidsson P, Hulthe J, Fagerberg B, Camejo G. Proteomics of apolipoproteins and associated proteins from plasma high-density lipoproteins. Arterioscler Thromb Vasc Biol 2009; 30:156-63. [PMID: 19778948 DOI: 10.1161/atvbaha.108.179317] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Proteomics studies have extended the list of identified apolipoproteins and associated proteins present in HDL and its subclasses. These proteins appear to cluster around specific functions related to lipid metabolism, inflammation, the immune system, hormone-binding, hemostasis, and antioxidant properties. Small studies suggest that there are substantial differences between the HDL proteome from cardiovascular disease patients and that from controls. Furthermore, dyslipidemia therapy shifts the HDL proteome from patients toward the profile observed in healthy controls. In addition, the proteome of HDL and LDL from patients with insulin resistance and peripheral atherosclerosis show significant differences with that of matched healthy controls. The proteome of HDL and LDL density subclasses have apolipoproteins and associated proteins profiles that suggest subclass-specific functions. However, proteomics studies of lipoproteins are few and small and should be interpreted with caution. Nonetheless rapid technical progress in proteomic platforms suggest that soon analysis time will be reduced and precise measurement of identified proteins will be possible. This, combined with controlled purification steps of HDL and its subclasses should provide further information about proteins involved in the particles postulated spectrum of functions, including those believed to be atheroprotective.
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33
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Small DM, Wang L, Mitsche MA. The adsorption of biological peptides and proteins at the oil/water interface. A potentially important but largely unexplored field. J Lipid Res 2009; 50 Suppl:S329-34. [PMID: 19029067 PMCID: PMC3283257 DOI: 10.1194/jlr.r800083-jlr200] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2008] [Revised: 11/21/2008] [Indexed: 11/20/2022] Open
Abstract
This review focuses on some new techniques to study the behavior of peptides and proteins bound to oil droplets. We will show how model peptides e.g., amphipathic alpha helices (AalphaH) and amphipathic beta strand (AbetaS) and some apolipoproteins adsorb to triacylglycerol (TAG) droplets and how they behave once adsorbed to the interface. While most of the studies described involve peptides and proteins at an oil/water interface, studies can also be carried out when the surface has been partially covered with phospholipids. This work is important because it examines biophysical changes that take place at lipid droplet interfaces and how this may relate to the metabolism of lipoproteins and lipid droplets.
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Affiliation(s)
- Donald M Small
- Department of Physiology and Biophysics, Boston University School of Medicine, 700 Albany Street, W-302, Boston, MA 02118, USA.
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34
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Wang L, Martin DDO, Genter E, Wang J, McLeod RS, Small DM. Surface study of apoB1694-1880, a sequence that can anchor apoB to lipoproteins and make it nonexchangeable. J Lipid Res 2009; 50:1340-52. [PMID: 19251580 DOI: 10.1194/jlr.m900040-jlr200] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Apolipoprotein B (apoB) is a nonexchangeable apolipoprotein. During lipoprotein assembly, it recruits phospholipids and triacylglycerols (TAG) into TAG-rich lipoprotein particles. It remains bound to secreted lipoproteins during lipid metabolism in plasma. The beta1 region (residues 827-1880) of apoB has a high amphipathic beta strand (AbetaS) content and is proposed to be one region anchoring apoB to lipoproteins. The AbetaS-rich region between apoB37 and apoB41 (residues 1694-1880) was cloned, expressed, and purified. The interfacial properties were studied at the triolein/water (TO/W) and air/water (A/W) interfaces. ApoB[37-41] is surface-active and adsorbs to the TO/W interface. After adsorption the unbound apoB[37-41] was removed from the aqueous phase. Adsorbed apoB[37-41] did not desorb and could not be forced off by increasing the surface pressure up to 23 mN/m. ApoB[37-41] adsorbed on the TO/W interface was completely elastic when compressed and expanded by +/-13% of its area. On an A/W interface, the apoB[37-41] monolayer became solid when compressed to 4 mN/m pressure indicating extended beta-sheet formation. It could be reversibly compressed and expanded between low pressure and its collapse pressure (35 mN/m). Our studies confirm that the AbetaS structure of apoB[37-41] is a lipid-binding motif that can irreversibly anchor apoB to lipoproteins.
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Affiliation(s)
- Libo Wang
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118-2526, USA
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35
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Mitsche MA, Wang L, Jiang ZG, McKnight CJ, Small DM. Interfacial properties of a complex multi-domain 490 amino acid peptide derived from apolipoprotein B (residues 292-782). LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:2322-2330. [PMID: 19146422 DOI: 10.1021/la802663g] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
ApolipoproteinB (ApoB) is a lipid binding protein that is a nonexchangeable component of chylomicrons, VLDL, and LDL. In the liver and intestinal cells ApoB recruits lipid to form nascent triacylglycerol rich particles cotranslationally in the endoplasmic reticulum membrane which are then processed and secreted to form plasma lipoproteins. The N-terminal domain, which comprises the first 22% of apoB, recruits lipid in a controlled manner. The first 6% (residues 1-291) of the N-terminus does not bind lipid. The first lipid binding domain, including residues 292-782 (B6-17), forms a lipid binding pocket which is predicted to consist of 17 alpha-helices and 6 beta-strands. A structural model based on the X-ray structure of the homologues protein lipovitellin suggests that the N-terminal 6-8 helices and the beta-sheet interact with lipid while the C-terminal helices form a structural unit stabilizing the beta-sheet. Using isothermal drop tensiometry we showed that ApoB6.4-17 is surface active and binds to a triolein/water interface and exerts 16-19 mN/m of pressure (Pi) on that surface. The protein initially adsorbs slowly from aqueous solution to the surface but following compression and re-expansion it reaches equilibrium much faster. When Pi exceeds 16.9 mN/m part of the protein is ejected from the surface, but when compressed to high Pi the protein is never completely ejected indicating that part of the peptide is irreversibly anchored to the interface. The surface dilation modulus (epsilon) varies between 25-38 mN/m, and is predominantly elastic with a small viscous component. When compressed at an air/water interface ApoB6.4-17 has a limiting area of approximately 11 A2 per amino acid at lift off and only approximately 7 A2 per amino acid at the collapse Pi (28 mN/m). These values are about half the anticipated values if all the residues are at the surface. This suggests that ApoB6.4-17 retains some globular structure at an interface and does not completely denature at the surface, as many other globular proteins do. We suggest that while bound to the surface ApoB6.4-17 exhibits properties of both alpha and beta structure giving it unique and versatile characteristics at a hydrophobic interface.
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Affiliation(s)
- Matthew A Mitsche
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts 02118, USA
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36
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Morita SY, Deharu Y, Takata E, Nakano M, Handa T. Cytotoxicity of lipid-free apolipoprotein B. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:2594-603. [DOI: 10.1016/j.bbamem.2008.08.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2008] [Revised: 08/19/2008] [Accepted: 08/19/2008] [Indexed: 11/17/2022]
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37
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Molecular structure of low density lipoprotein: current status and future challenges. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2008; 38:145-58. [DOI: 10.1007/s00249-008-0368-y] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2008] [Accepted: 08/28/2008] [Indexed: 01/01/2023]
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38
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Ledford AS, Cook VA, Shelness GS, Weinberg RB. Structural and dynamic interfacial properties of the lipoprotein initiating domain of apolipoprotein B. J Lipid Res 2008; 50:108-15. [PMID: 18711207 DOI: 10.1194/jlr.m800324-jlr200] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To better understand the earliest steps in the assembly of triglyceride (TG)-rich lipoproteins, we compared the biophysical and interfacial properties of two closely related apolipoprotein B (apoB) truncation mutants, one of which contains the complete lipoprotein initiating domain (apoB20.1; residues 1-912), and one of which, by virtue of a 50 amino acid C-terminal truncation, is incapable of forming nascent lipoproteins (apoB19; residues 1-862). Spectroscopic studies detected no major differences in secondary structure, and only minor differences in conformation and thermodynamic stability, between the two truncation mutants. Monolayer studies revealed that both apoB19 and apoB20.1 bound to and penetrated egg phosphatidylcholine (EPC) monolayers; however, the interfacial exclusion pressure of apoB20.1 was higher than apoB19 (25.1 mN/m vs. 22.8 mN/m). Oil drop tensiometry revealed that both proteins bound rapidly to the hydrophobic triolein/water interface, reducing interfacial tension by approximately 20 mN/m. However, when triolein drops were first coated with phospholipids (PL), apoB20.1 bound with faster kinetics than apoB19 and also displayed greater interfacial elasticity (26.9 +/- 0.8 mN/m vs. 22.9 +/- 0.8 mN/m). These data establish that the transition of apoB to assembly competence is accompanied by increases in surface activity and elasticity, but not by significant changes in global structure.
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Affiliation(s)
- Aubrey S Ledford
- Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
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39
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Koivuniemi A, Kovanen PT, Hyvönen MT. Molecular dynamics simulations of a lipovitellin-derived amphiphilic beta-sheet homologous to apoB-100 beta-sheets at a hydrophobic decane-water interface. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2008; 1784:1668-75. [PMID: 18619564 DOI: 10.1016/j.bbapap.2008.06.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2008] [Revised: 05/19/2008] [Accepted: 06/04/2008] [Indexed: 12/12/2022]
Abstract
Lipovitellin, an egg-yolk lipoprotein, transports lipids in a pocket surrounded by amphiphilic beta-sheets. Its X-ray structure provides possibilities to study interactions between lipophilic beta-sheets and lipids at the atomic level. Here, we studied a 67-residue-long amphiphilic beta-sheet of lipovitellin previously suggested a suitable working model for studies of the lipid-binding behaviour of amphiphilic beta-sheet regions in apolipoprotein B-100 (apoB-100). We performed four molecular dynamics simulations with different starting configurations to define characteristics of the amphiphilic beta-sheet model at a decane-water interface. In each simulation the model beta-sheet bound keenly to the decane layer via its hydrophobic surface. The structural profiles showed unchanged secondary structure of the beta-sheet during the attachment. Also, aromatic side chains, especially tryptophans and tyrosines, mediated the attachment to the hydrophobic layer and influenced the orientation of the decane molecules that are in contact with the beta-sheet. In conclusion, the present simulations reveal high affinity of a lipovitellin-derived amphiphilic beta-sheet to a hydrophobic decane layer. They lay thereby the basis for further studies of the interaction between amphiphilic beta-sheets and lipids in complex molecular systems, like LDL particles, in which the large apoB-100 is the main protein component.
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40
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Listenberger LL, Ostermeyer-Fay AG, Goldberg EB, Brown WJ, Brown DA. Adipocyte differentiation-related protein reduces the lipid droplet association of adipose triglyceride lipase and slows triacylglycerol turnover. J Lipid Res 2007; 48:2751-61. [PMID: 17872589 DOI: 10.1194/jlr.m700359-jlr200] [Citation(s) in RCA: 235] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Although neutral lipid storage droplets are ubiquitous in eukaryotic cells, very little is known about how their synthesis and turnover are controlled. Adipocyte differentiation-related protein (ADRP; also known as adipophilin) is found on the surface of lipid droplets in most mammalian cell types. To learn how ADRP affects lipid storage, we stably expressed the protein in human embryonic kidney 293 (HEK 293) cells, which express little endogenous ADRP. As expected, ADRP was targeted to the surface of lipid droplets and caused an increase in triacylglycerol (TAG) mass under both basal and oleate-supplemented conditions. At least part of the increased mass resulted from a 50% decrease in the rate of TAG hydrolysis in ADRP-expressing cells. Furthermore, ADRP expression increased the fraction of total cellular TAG that was stored in lipid droplets. ADRP expression induced a striking decrease in the association of adipose triglyceride lipase (ATGL) and mannose-6-phosphate receptor tail-interacting protein of 47 kDa with lipid droplets and also decreased the lipid droplet association of several other unknown proteins. Transient expression of ADRP in two other cell lines also reduced the lipid droplet association of catalytically inactive ATGL. We conclude that the reduced lipid droplet association of ATGL and/or other lipases may explain the decrease in TAG turnover observed in ADRP-expressing HEK 293 cells.
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Affiliation(s)
- Laura L Listenberger
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794, USA
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41
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Jiang ZG, Simon MN, Wall JS, McKnight CJ. Structural analysis of reconstituted lipoproteins containing the N-terminal domain of apolipoprotein B. Biophys J 2007; 92:4097-108. [PMID: 17369413 PMCID: PMC1868998 DOI: 10.1529/biophysj.106.101105] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Apolipoproteins play a central role in lipoprotein metabolism, and are directly implicated in cardiovascular diseases, but their structural characterization has been complicated by their structural flexibility and heterogeneity. Here we describe the structural characterization of the N-terminal region of apolipoprotein B (apoB), the major protein component of very low-density lipoprotein and low-density lipoprotein, in the presence of phospholipids. Specifically, we focus on the N-terminal 6.4-17% of apoB (B6.4-17) complexed with the phospholipid dimyristoylphosphatidylcholine in vitro. In addition to circular dichroism spectroscopy and limited proteolysis, our strategy incorporates nanogold-labeling of the protein in the reconstituted lipoprotein complex followed by visualization and molecular weight determination with scanning transmission electron microscopy imaging. Based on the scanning transmission electron microscopy imaging analysis of approximately 1300 individual particles where the B6.4-17 is labeled with nanogold through a six-His tag, most complexes contain either two or three B6.4-17 molecules. Circular dichroism spectroscopy and limited proteolysis of these reconstituted particles indicate that there are no large conformational changes in B6.4-17 upon lipoprotein complex formation. This is in contrast to the large structural changes that occur during apolipoprotein A-I-lipid interactions. The method described here allows a direct measurement of the stoichiometry and molecular weight of individual particles, rather than the average of the entire sample. Thus, it represents a useful strategy to characterize the structure of lipoproteins, which are not structurally uniform, but can still be defined by an ensemble of related patterns.
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Affiliation(s)
- Zhenghui Gordon Jiang
- Boston University School of Medicine, Department of Physiology & Biophysics, Boston, Massachusetts, USA
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