51
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Li L, Li S, Jones MK, Segrest JP. Rotational and hinge dynamics of discoidal high density lipoproteins probed by interchain disulfide bond formation. Biochim Biophys Acta Mol Cell Biol Lipids 2011; 1821:481-9. [PMID: 22063273 DOI: 10.1016/j.bbalip.2011.10.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Revised: 10/10/2011] [Accepted: 10/13/2011] [Indexed: 11/30/2022]
Abstract
To develop a detailed double belt model for discoidal HDL, we previously scored inter-helical salt bridges between all possible registries of two stacked antiparallel amphipathic helical rings of apolipoprotein (apo) A-I. The top score was the antiparallel apposition of helix 5 with 5 followed closely by appositions of helix 5 with 4 and helix 5 with 6. The rationale for the current study is that, for each of the optimal scores, a pair of identical residues can be identified in juxtaposition directly on the contact edge between the two antiparallel helical belts of apoA-I. Further, these residues are always in the '9th position' in one of the eighteen 11-mer repeats that make up the lipid-associating domain of apoA-I. To illustrate our terminology, 129j (LL5/5) refers to the juxtaposition of the Cα atoms of G129 (in a '9th position') in the pairwise helix 5 domains. We reasoned that if identical residues in the double belt juxtapositions were mutated to a cysteine and kept under reducing conditions during disc formation, we would have a precise method for determining registration in discoidal HDL by formation of a disulfide-linked apoA-I homodimer. Using this approach, we conclude that 129j (LL5/5) is the major rotamer orientation for double belt HDL and propose that the small ubiquitous gap between the pairwise helix 5 portions of the double belt in larger HDL discoidal particles is significantly dynamic to hinge off the disc edge under certain conditions, e.g., in smaller particles or perhaps following binding of the enzyme LCAT. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945-2010).
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Affiliation(s)
- Ling Li
- Department of Medicine and Atherosclerosis Research Unit, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
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52
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Sriram R, Lagerstedt JO, Petrlova J, Samardzic H, Kreutzer U, Xie H, Kaysen GA, Desreux JF, Thonon D, Jacques V, Van Loan M, Rutledge JC, Oda MN, Voss JC, Jue T. Imaging apolipoprotein AI in vivo. NMR IN BIOMEDICINE 2011; 24:916-24. [PMID: 21264979 PMCID: PMC3726305 DOI: 10.1002/nbm.1650] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Revised: 10/20/2010] [Accepted: 10/31/2010] [Indexed: 05/30/2023]
Abstract
Coronary disease risk increases inversely with high-density lipoprotein (HDL) level. The measurement of the biodistribution and clearance of HDL in vivo, however, has posed a technical challenge. This study presents an approach to the development of a lipoprotein MRI agent by linking gadolinium methanethiosulfonate (Gd[MTS-ADO3A]) to a selective cysteine mutation in position 55 of apo AI, the major protein of HDL. The contrast agent targets both liver and kidney, the sites of HDL catabolism, whereas the standard MRI contrast agent, gadolinium-diethylenetriaminepentaacetic acid-bismethylamide (GdDTPA-BMA, gadodiamide), enhances only the kidney image. Using a modified apolipoprotein AI to create an HDL contrast agent provides a new approach to investigate HDL biodistribution, metabolism and regulation in vivo.
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Affiliation(s)
- Renuka Sriram
- Biochemistry and Molecular Medicine, University of California Davis, Davis, CA, USA
| | | | - Jitka Petrlova
- Biochemistry and Molecular Medicine, University of California Davis, Davis, CA, USA
| | - Haris Samardzic
- Biochemistry and Molecular Medicine, University of California Davis, Davis, CA, USA
| | - Ulrike Kreutzer
- Biochemistry and Molecular Medicine, University of California Davis, Davis, CA, USA
| | - Hongtao Xie
- Biochemistry and Molecular Medicine, University of California Davis, Davis, CA, USA
| | - George A. Kaysen
- Biochemistry and Molecular Medicine, University of California Davis, Davis, CA, USA
| | - Jean F. Desreux
- Coordination and Radiochemistry, University of Liege, Liege, Belgium
| | - David Thonon
- Coordination and Radiochemistry, University of Liege, Liege, Belgium
| | | | - Martha Van Loan
- Nutrition Department, University of California Davis, Davis, CA, USA
| | - John C. Rutledge
- Division of Endocrinology, Clinical Nutrition and Vascular Medicine, Department of Internal Medicine, University of California Davis, Davis, CA, USA
| | - Michael N. Oda
- Children’s Hospital Oakland Research Institute, Oakland, CA, USA
| | - John C. Voss
- Biochemistry and Molecular Medicine, University of California Davis, Davis, CA, USA
| | - Thomas Jue
- Biochemistry and Molecular Medicine, University of California Davis, Davis, CA, USA
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53
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Abstract
In this article, we provide an overview of lipid simulations, describing how a computer can be used as a laboratory for lipid research. We briefly discuss the methodology of lipid simulations followed by a number of topical applications that show the benefit of computer modeling for complementing experiments. In particular, we show examples of cases in which simulations have made predictions of novel phenomena that have later been confirmed by experimental studies. Overall, the applications discussed in this article focus on the most recent state of the art and aim to provide a perspective of where the field of lipid simulations stands at the moment.
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Affiliation(s)
- Ilpo Vattulainen
- Department of Physics, Tampere University of Technology, Finland.
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54
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Huang R, Silva RAGD, Jerome WG, Kontush A, Chapman MJ, Curtiss LK, Hodges TJ, Davidson WS. Apolipoprotein A-I structural organization in high-density lipoproteins isolated from human plasma. Nat Struct Mol Biol 2011; 18:416-22. [PMID: 21399642 PMCID: PMC3079355 DOI: 10.1038/nsmb.2028] [Citation(s) in RCA: 169] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Accepted: 12/15/2010] [Indexed: 12/31/2022]
Abstract
High density lipoproteins (HDL) mediate cholesterol transport and protection from cardiovascular disease. Although synthetic HDLs have been studied for 30 years, the structure of human plasma-derived HDL, and its major protein apolipoprotein (apo)A-I, is unknown. We separated normal human HDL into 5 density subfractions and then further isolated those containing predominantly apoA-I (LpA-I). Using cross-linking chemistry and mass spectrometry, we found that apoA-I adopts a structural framework in these particles that closely mirrors that in synthetic HDL. We adapted established structural models for synthetic HDL to generate the first detailed models of authentic human plasma HDL in which apoA-I adopts a symmetrical cage-like structure. The models suggest that HDL particle size is modulated via a twisting motion of the resident apoA-I molecules. This understanding offers insights into how apoA-I structure modulates HDL function and its interactions with other apolipoproteins.
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Affiliation(s)
- Rong Huang
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio, USA
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55
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Jones MK, Gu F, Catte A, Li L, Segrest JP. "Sticky" and "promiscuous", the yin and yang of apolipoprotein A-I termini in discoidal high-density lipoproteins: a combined computational-experimental approach. Biochemistry 2011; 50:2249-63. [PMID: 21329368 DOI: 10.1021/bi101301g] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Apolipoprotein (apo) A-I-containing lipoproteins in the form of high-density lipoproteins (HDL) are inversely correlated with atherosclerosis. Because HDL is a soft form of condensed matter easily deformable by thermal fluctuations, the molecular mechanisms for HDL remodeling are not well understood. A promising approach to understanding HDL structure and dynamics is molecular dynamics (MD). In the present study, two computational strategies, MD simulated annealing (MDSA) and MD temperature jump, were combined with experimental particle reconstitution to explore molecular mechanisms for phospholipid- (PL-) rich HDL particle remodeling. The N-terminal domains of full-length apoA-I were shown to be "sticky", acting as a molecular latch largely driven by salt bridges, until, at a critical threshold of particle size, the associated domains released to expose extensive hydrocarbon regions of the PL to solvent. The "sticky" N-termini also associate with other apoA-I domains, perhaps being involved in N-terminal loops suggested by other laboratories. Alternatively, the overlapping helix 10 C-terminal domains of apoA-I were observed to be extremely mobile or "promiscuous", transiently exposing limited hydrocarbon regions of PL. Based upon these models and reconstitution studies, we propose that separation of the N-terminal domains, as particles exceed a critical size, triggers fusion between particles or between particles and membranes, while the C-terminal domains of apoA-I drive the exchange of polar lipids down concentration gradients between particles. This hypothesis has significant biological relevance since lipid exchange and particle remodeling are critically important processes during metabolism of HDL particles at every step in the antiatherogenic process of reverse cholesterol transport.
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Affiliation(s)
- Martin K Jones
- Department of Medicine and Atherosclerosis Research Unit, University of Alabama at Birmingham, Birmingham, Alabama 35294, United States
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56
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Wu Z, Gogonea V, Lee X, May RP, Pipich V, Wagner MA, Undurti A, Tallant TC, Baleanu-Gogonea C, Charlton F, Ioffe A, DiDonato JA, Rye KA, Hazen SL. The low resolution structure of ApoA1 in spherical high density lipoprotein revealed by small angle neutron scattering. J Biol Chem 2011; 286:12495-508. [PMID: 21292766 DOI: 10.1074/jbc.m110.209130] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Spherical high density lipoprotein (sHDL), a key player in reverse cholesterol transport and the most abundant form of HDL, is associated with cardiovascular diseases. Small angle neutron scattering with contrast variation was used to determine the solution structure of protein and lipid components of reconstituted sHDL. Apolipoprotein A1, the major protein of sHDL, forms a hollow structure that cradles a central compact lipid core. Three apoA1 chains are arranged within the low resolution structure of the protein component as one of three possible global architectures: (i) a helical dimer with a hairpin (HdHp), (ii) three hairpins (3Hp), or (iii) an integrated trimer (iT) in which the three apoA1 monomers mutually associate over a portion of the sHDL surface. Cross-linking and mass spectrometry analyses help to discriminate among the three molecular models and are most consistent with the HdHp overall architecture of apoA1 within sHDL.
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Affiliation(s)
- Zhiping Wu
- Department of Cell Biology, Center for Cardiovascular Diagnostics and Prevention, Cleveland Clinic, Cleveland, OH 44195, USA
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57
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Gao T, Blanchette CD, He W, Bourguet F, Ly S, Katzen F, Kudlicki WA, Henderson PT, Laurence TA, Huser T, Coleman MA. Characterizing diffusion dynamics of a membrane protein associated with nanolipoproteins using fluorescence correlation spectroscopy. Protein Sci 2011; 20:437-47. [PMID: 21280134 PMCID: PMC3048428 DOI: 10.1002/pro.577] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2010] [Revised: 11/29/2010] [Accepted: 12/01/2010] [Indexed: 01/28/2023]
Abstract
Nanolipoprotein particles (NLPs) represent a unique nanometer-sized scaffold for supporting membrane proteins (MP). Characterization of their dynamic shape and association with MP in solution remains a challenge. Here, we present a rapid method of analysis by fluorescence correlation spectroscopy (FCS) to characterize bacteriorhodopsin (bR), a membrane protein capable of forming a NLP complex. By selectively labeling individual components of NLPs during cell-free synthesis, FCS enabled us to measure specific NLP diffusion times and infer size information for different NLP species. The resulting bR-loaded NLPs were shown to be dynamically discoidal in solution with a mean diameter of 7.8 nm. The insertion rate of bR in the complex was ∼55% based on a fit model incorporating two separate diffusion properties to best approximate the FCS data. More importantly, based on these data, we infer that membrane protein associated NLPs are thermodynamically constrained as discs in solution, while empty NLPs appear to be less constrained and dynamically spherical.
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Affiliation(s)
- Tingjuan Gao
- NSF Center for Biophotonics Science and Technology, School of Medicine, University of California DavisSacramento, California 95817
| | - Craig D Blanchette
- Lawrence Livermore National Laboratory, Physics and Life SciencesLivermore, California 94550
| | - Wei He
- NSF Center for Biophotonics Science and Technology, School of Medicine, University of California DavisSacramento, California 95817
| | - Feliza Bourguet
- Lawrence Livermore National Laboratory, Physics and Life SciencesLivermore, California 94550
| | - Sonny Ly
- NSF Center for Biophotonics Science and Technology, School of Medicine, University of California DavisSacramento, California 95817
| | | | | | - Paul T Henderson
- NSF Center for Biophotonics Science and Technology, School of Medicine, University of California DavisSacramento, California 95817
| | - Ted A Laurence
- Lawrence Livermore National Laboratory, Physics and Life SciencesLivermore, California 94550
| | - Thomas Huser
- NSF Center for Biophotonics Science and Technology, School of Medicine, University of California DavisSacramento, California 95817
| | - Matthew A Coleman
- NSF Center for Biophotonics Science and Technology, School of Medicine, University of California DavisSacramento, California 95817
- Lawrence Livermore National Laboratory, Physics and Life SciencesLivermore, California 94550
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58
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Bricarello DA, Smilowitz JT, Zivkovic AM, German JB, Parikh AN. Reconstituted lipoprotein: a versatile class of biologically-inspired nanostructures. ACS NANO 2011; 5:42-57. [PMID: 21182259 DOI: 10.1021/nn103098m] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
One of biology's most pervasive nanostructures, the phospholipid membrane, represents an ideal scaffold for a host of nanotechnology applications. Whether engineering biomimetic technologies or designing therapies to interface with the cell, this adaptable membrane can provide the necessary molecular-level control of membrane-anchored proteins, glycopeptides, and glycolipids. If appropriately prepared, these components can replicate in vitro or influence in vivo essential living processes such as signal transduction, mass transport, and chemical or energy conversion. To satisfy these requirements, a lipid-based, synthetic nanoscale architecture with molecular-level tunability is needed. In this regard, discrete lipid particles, including reconstituted high density lipoprotein (HDL), have emerged as a versatile and elegant solution. Structurally diverse, native biological HDLs exist as discoidal lipid bilayers of 5-8 nm diameter and lipid monolayer-coated spheres 10-15 nm in diameter, all belted by a robust scaffolding protein. These supramolecular assemblies can be reconstituted using simple self-assembly methods to incorporate a broad range of amphipathic molecular constituents, natural or artificial, and provide a generic platform for stabilization and transport of amphipathic and hydrophobic elements capable of docking with targets at biological or inorganic surfaces. In conjunction with top-down or bottom-up engineering approaches, synthetic HDL can be designed, arrayed, and manipulated for a host of applications including biochemical analyses and fundamental studies of molecular structure. Also highly biocompatible, these assemblies are suitable for medical diagnostics and therapeutics. The collection of efforts reviewed here focuses on laboratory methods by which synthetic HDLs are produced, the advantages conferred by their nanoscopic dimension, and current and emerging applications.
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Affiliation(s)
- Daniel A Bricarello
- Department of Applied Science, University of California-Davis, Davis, California 95616, United States
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59
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Prieto ED, Garda HA. Membrane insertion topology of the central apolipoprotein A-I region. Fluorescence studies using single tryptophan mutants. Biochemistry 2010; 50:466-79. [PMID: 21141907 DOI: 10.1021/bi1009634] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Apolipoprotein A-I (apoAI) contains several amphipathic α-helices. To carry out its function, it exchanges between lipid-free and different lipidated states as bound to membranes or to lipoprotein complexes of different morphology, size, and composition. When bound to membranes or to spherical lipoprotein surfaces, it is thought that most α-helices arrange with their long axis parallel to the membrane surface. However, we previously found that a central region spanning residues 87-112 is exclusively labeled by photoactivable reagents deeply located into the membrane (Córsico et al. (2001) J. Biol. Chem. 276, 16978-16985). A pair of amphipathic α-helical repeats with a particular charge distribution is predicted in this region. In order to study their insertion topology, three single tryptophan mutants, each one containing the tryptophan residue at a selected position in the hydrophobic face of the central Y-helices (W@93, W@104, and W@108), were used. From the accessibility to quenchers located at different membrane depths, distances from the bilayer center of 13.4, 10.5, and 15.7 Å were estimated for positions 93, 104, and 108, respectively. Reported data also indicate that distances between homologous positions (in particular for W@93 and W@104) are very short in dimers in aqueous solution, but they are larger in membrane-bound dimers. Data indicate that an intermolecular central Y-helix bundle would penetrate the membrane perpendicularly to the membrane surface. Intermolecular helix-helix interactions would occur through the hydrophilic helix faces in the membrane-bound bundle but through the hydrophobic faces in the case of dimers in solution.
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Affiliation(s)
- Eduardo D Prieto
- Instituto de Investigaciones Bioquímicas de La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de La Plata, Facultad de Ciencias Médicas, Calles 60 y 120, La Plata, Argentina
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60
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Bashtovyy D, Jones MK, Anantharamaiah GM, Segrest JP. Sequence conservation of apolipoprotein A-I affords novel insights into HDL structure-function. J Lipid Res 2010; 52:435-50. [PMID: 21159667 DOI: 10.1194/jlr.r012658] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We performed alignment of apolipoprotein A-I (apoA-I) sequences from 31 species of animals. We found there is specific conservation of salt bridge-forming residues in the first 30 residues of apoA-I and general conservation of a variety of residue types in the central domain, helix 2/3 to helix 7/8. In the lipid-associating domain, helix 7 and helix 10 are the most and least conserved helixes, respectively. Furthermore, eight residues are completely conserved: P66, R83, P121, E191, and P220, and three of seven Tyr residues in human apoA-I, Y18, Y115, and Y192, are conserved. Residue Y18 appears to be important for assembly of HDL. E191-Y192 represents the only completely conserved pair of adjacent residues in apoA-I; Y192 is a preferred target for site-specific oxidative modification within atheroma, and molecular dynamic simulations suggest that the conserved pair E191-Y192 is in a solvent-exposed loop-helix-loop. Molecular dynamics testing of human apoA-I showed that M112 and M148 interact with Y115, a microenvironment unique to human apoA-I. Finally, conservation of Arg residues in the α11/3 helical wheel position 7 supports several possibilities: interactions with adjacent phospholipid molecules and/or oxidized lipids and/or binding of antioxidant enzymes through cation-π orbital interactions. We conclude that sequence alignment of apoA-I provides unique insights into apoA-I structure-function relationship.
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Affiliation(s)
- Denys Bashtovyy
- Department of Medicine, Atherosclerosis Research Unit, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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61
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Lagerstedt JO, Cavigiolio G, Budamagunta MS, Pagani I, Voss JC, Oda MN. Structure of apolipoprotein A-I N terminus on nascent high density lipoproteins. J Biol Chem 2010; 286:2966-75. [PMID: 21047795 DOI: 10.1074/jbc.m110.163097] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Apolipoprotein A-I (apoA-I) is the major protein component of high density lipoproteins (HDL) and a critical element of cholesterol metabolism. To better elucidate the role of the apoA-I structure-function in cholesterol metabolism, the conformation of the apoA-I N terminus (residues 6-98) on nascent HDL was examined by electron paramagnetic resonance (EPR) spectroscopic analysis. A series of 93 apoA-I variants bearing single nitroxide spin label at positions 6-98 was reconstituted onto 9.6-nm HDL particles (rHDL). These particles were subjected to EPR spectral analysis, measuring regional flexibility and side chain solvent accessibility. Secondary structure was elucidated from side-chain mobility and molecular accessibility, wherein two major α-helical domains were localized to residues 6-34 and 50-98. We identified an unstructured segment (residues 35-39) and a β-strand (residues 40-49) between the two helices. Residues 14, 19, 34, 37, 41, and 58 were examined by EPR on 7.8, 8.4, and 9.6 nm rHDL to assess the effect of particle size on the N-terminal structure. Residues 14, 19, and 58 showed no significant rHDL size-dependent spectral or accessibility differences, whereas residues 34, 37, and 41 displayed moderate spectral changes along with substantial rHDL size-dependent differences in molecular accessibility. We have elucidated the secondary structure of the N-terminal domain of apoA-I on 9.6 nm rHDL (residues 6-98) and identified residues in this region that are affected by particle size. We conclude that the inter-helical segment (residues 35-49) plays a role in the adaptation of apoA-I to the particle size of HDL.
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Affiliation(s)
- Jens O Lagerstedt
- Department of Experimental Medical Science, Lund University, S-221 84 Lund, Sweden
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62
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Zhang L, Song J, Cavigiolio G, Ishida BY, Zhang S, Kane JP, Weisgraber KH, Oda MN, Rye KA, Pownall HJ, Ren G. Morphology and structure of lipoproteins revealed by an optimized negative-staining protocol of electron microscopy. J Lipid Res 2010; 52:175-84. [PMID: 20978167 PMCID: PMC2999936 DOI: 10.1194/jlr.d010959] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Plasma lipoprotein levels are predictors of risk for coronary artery disease. Lipoprotein structure-function relationships provide important clues that help identify the role of lipoproteins in cardiovascular disease. The compositional and conformational heterogeneity of lipoproteins are major barriers to the identification of their structures, as discovered using traditional approaches. Although electron microscopy (EM) is an alternative approach, conventional negative staining (NS) produces rouleau artifacts. In a previous study of apolipoprotein (apo)E4-containing reconstituted HDL (rHDL) particles, we optimized the NS method in a way that eliminated rouleaux. Here we report that phosphotungstic acid at high buffer salt concentrations plays a key role in rouleau formation. We also validate our protocol for analyzing the major plasma lipoprotein classes HDL, LDL, IDL, and VLDL, as well as homogeneously prepared apoA-I-containing rHDL. High-contrast EM images revealed morphology and detailed structures of lipoproteins, especially apoA-I-containing rHDL, that are amenable to three-dimensional reconstruction by single-particle analysis and electron tomography.
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Affiliation(s)
- Lei Zhang
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
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63
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Jones MK, Zhang L, Catte A, Li L, Oda MN, Ren G, Segrest JP. Assessment of the validity of the double superhelix model for reconstituted high density lipoproteins: a combined computational-experimental approach. J Biol Chem 2010; 285:41161-71. [PMID: 20974855 DOI: 10.1074/jbc.m110.187799] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
For several decades, the standard model for high density lipoprotein (HDL) particles reconstituted from apolipoprotein A-I (apoA-I) and phospholipid (apoA-I/HDL) has been a discoidal particle ∼100 Å in diameter and the thickness of a phospholipid bilayer. Recently, Wu et al. (Wu, Z., Gogonea, V., Lee, X., Wagner, M. A., Li, X. M., Huang, Y., Undurti, A., May, R. P., Haertlein, M., Moulin, M., Gutsche, I., Zaccai, G., Didonato, J. A., and Hazen, S. L. (2009) J. Biol. Chem. 284, 36605-36619) used small angle neutron scattering to develop a new model they termed double superhelix (DSH) apoA-I that is dramatically different from the standard model. Their model possesses an open helical shape that wraps around a prolate ellipsoidal type I hexagonal lyotropic liquid crystalline phase. Here, we used three independent approaches, molecular dynamics, EM tomography, and fluorescence resonance energy transfer spectroscopy (FRET) to assess the validity of the DSH model. (i) By using molecular dynamics, two different approaches, all-atom simulated annealing and coarse-grained simulation, show that initial ellipsoidal DSH particles rapidly collapse to discoidal bilayer structures. These results suggest that, compatible with current knowledge of lipid phase diagrams, apoA-I cannot stabilize hexagonal I phase particles of phospholipid. (ii) By using EM, two different approaches, negative stain and cryo-EM tomography, show that reconstituted apoA-I/HDL particles are discoidal in shape. (iii) By using FRET, reconstituted apoA-I/HDL particles show a 28-34-Å intermolecular separation between terminal domain residues 40 and 240, a distance that is incompatible with the dimensions of the DSH model. Therefore, we suggest that, although novel, the DSH model is energetically unfavorable and not likely to be correct. Rather, we conclude that all evidence supports the likelihood that reconstituted apoA-I/HDL particles, in general, are discoidal in shape.
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Affiliation(s)
- Martin K Jones
- Department of Medicine and Atherosclerosis Research Unit, University of Alabama, Birmingham, Alabama 35294, USA
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64
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Gogonea V, Wu Z, Lee X, Pipich V, Li XM, Ioffe AI, Didonato JA, Hazen SL. Congruency between biophysical data from multiple platforms and molecular dynamics simulation of the double-super helix model of nascent high-density lipoprotein. Biochemistry 2010; 49:7323-43. [PMID: 20687589 DOI: 10.1021/bi100588a] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The predicted structure and molecular trajectories from >80 ns molecular dynamics simulation of the solvated Double-Super Helix (DSH) model of nascent high-density lipoprotein (HDL) were determined and compared with experimental data on reconstituted nascent HDL obtained from multiple biophysical platforms, including small angle neutron scattering (SANS) with contrast variation, hydrogen-deuterium exchange tandem mass spectrometry (H/D-MS/MS), nuclear magnetic resonance spectroscopy (NMR), cross-linking tandem mass spectrometry (MS/MS), fluorescence resonance energy transfer (FRET), electron spin resonance spectroscopy (ESR), and electron microscopy. In general, biophysical constraints experimentally derived from the multiple platforms agree with the same quantities evaluated using the simulation trajectory. Notably, key structural features postulated for the recent DSH model of nascent HDL are retained during the simulation, including (1) the superhelical conformation of the antiparallel apolipoprotein A1 (apoA1) chains, (2) the lipid micellar-pseudolamellar organization, and (3) the solvent-exposed Solar Flare loops, proposed sites of interaction with LCAT (lecithin cholesteryl acyltransferase). Analysis of salt bridge persistence during simulation provides insights into structural features of apoA1 that forms the backbone of the lipoprotein. The combination of molecular dynamics simulation and experimental data from a broad range of biophysical platforms serves as a powerful approach to studying large macromolecular assemblies such as lipoproteins. This application to nascent HDL validates the DSH model proposed earlier and suggests new structural details of nascent HDL.
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Affiliation(s)
- Valentin Gogonea
- Department of Chemistry, Cleveland State University, Cleveland, Ohio 44115, USA.
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65
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A phospholipid-apolipoprotein A-I nanoparticle containing amphotericin B as a drug delivery platform with cell membrane protective properties. Int J Pharm 2010; 399:148-55. [PMID: 20696226 DOI: 10.1016/j.ijpharm.2010.07.057] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Revised: 07/23/2010] [Accepted: 07/30/2010] [Indexed: 11/21/2022]
Abstract
Amphotericin B (AMB), a potent antifungal agent, has been employed as an inhalable therapy for pulmonary fungal infections. We recently described a novel nano-sized delivery vehicle composed of phospholipid (PL) and apolipoprotein A-I, NanoDisk (ND), to which we added AMB as a payload (ND-AMB). The goal of the present study was to evaluate whether ND-AMB, compared to other formulations, preserves lung cell integrity in vitro, as AMB can be toxic to mammalian cells and reduce lung function when inhaled. Epithelial integrity was assessed by measuring K(+) ion flux across a model airway epithelium, Calu-3 cells. In this assay ND-AMB was at least 8-fold less disruptive than AMB/deoxycholate (DOC). Cell viability studies confirmed this observation. Unexpectedly, the ND vehicle restored the integrity of a membrane compromised by prior exposure to AMB. An alternative formulation of ND-AMB containing a high load of AMB per ND was not protective, suggesting that ND with a low ratio of AMB to PL can sequester additional AMB from membranes. ND-AMB also protected HepG2 cells from the cytotoxicity of AMB, as determined by cellular viability and lactate dehydrogenase (LDH) levels. This study suggests that ND-AMB may be safe for administration via inhalation and reveals a unique activity whereby ND-AMB protects lung epithelial membranes from AMB toxicity.
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66
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Bhat S, Sorci-Thomas MG, Calabresi L, Samuel MP, Thomas MJ. Conformation of dimeric apolipoprotein A-I milano on recombinant lipoprotein particles. Biochemistry 2010; 49:5213-24. [PMID: 20524691 DOI: 10.1021/bi1003734] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Apolipoprotein A-I Milano (apoA-I(Milano)) is a naturally occurring human mutation of wild-type apolipoprotein A-I (apoA-I(WT)) having cystine substituted for arginine(173). Two molecules of apo-I(WT) form disks with phospholipid having a defined relationship between the apoA-I(WT) molecules. ApoA-I(Milano) forms cystine homodimers that would not allow the protein to adopt the conformation reported for apoA-I(WT). The conformational constraints for dimeric apoA-I(Milano) recombinant high-density lipoprotein (rHDL) disks made with phospholipid were deduced from a combination of chemical cross-linking and mass spectrometry. Lysine-selective homobifunctional cross-linkers were reacted with homogeneous rHDL having diameters of 78 and 125 A. After reduction, cross-linked apoA-I(Milano) was separated from monomeric apoprotein by gel electrophoresis and then subjected to in-gel trypsin digest. Cross-linked peptides were confirmed by MS/MS sequencing. The cross-links provided distance constraints that were used to refine models of lipid-bound dimeric apoA-I(Milano). These studies suggest that a single dimeric apoA-I(Milano) on 78 A diameter rHDL girdles the edge of a phospholipid disk assuming a "belt" conformation similar to the "belt" region of apoA-I(WT) on rHDL. However, the C-terminal end of dimeric apoA-I(Milano) wraps around the periphery of the particle to shield the fatty acid chains from water rather than folding back onto the "belt" as does apoA-I(WT). The two apoA-I(Milano) dimers on a 125 A diameter rHDL do not encircle the periphery of a phospholipid disk but appear to reside on the surface of a laminar micelle.
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Affiliation(s)
- Shaila Bhat
- Department of Pathology, Center for Lipid Science, Wake Forest University Health Sciences, Medical Center Boulevard, Winston-Salem, North Carolina 27157, USA
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67
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Shao B, Oda MN, Oram JF, Heinecke JW. Myeloperoxidase: an oxidative pathway for generating dysfunctional high-density lipoprotein. Chem Res Toxicol 2010; 23:447-54. [PMID: 20043647 DOI: 10.1021/tx9003775] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Accumulation of low-density lipoprotein (LDL)-derived cholesterol by artery wall macrophages triggers atherosclerosis, the leading cause of cardiovascular disease. Conversely, high-density lipoprotein (HDL) retards atherosclerosis by promoting cholesterol efflux from macrophages by the membrane-associated ATP-binding cassette transporter A1 (ABCA1) pathway. HDL has been proposed to lose its cardioprotective effects in subjects with atherosclerosis, but the underlying mechanisms are poorly understood. One potential pathway involves oxidative damage by myeloperoxidase (MPO), a heme enzyme secreted by human artery wall macrophages. We used mass spectrometry to demonstrate that HDL isolated from patients with established cardiovascular disease contains elevated levels of 3-chlorotyrosine and 3-nitrotyrosine, two characteristic products of MPO. When apolipoprotein A-I (apoA-I), the major HDL protein, was oxidized by MPO, its ability to promote cellular cholesterol efflux by ABCA1 was impaired. Moreover, oxidized apoA-I was unable to activate lecithin:cholesterol acyltransferase (LCAT), which rapidly converts free cholesterol to cholesteryl ester, a critical step in HDL maturation. Biochemical studies implicated tyrosine chlorination and methionine oxygenation in the loss of ABCA1 and LCAT activity by oxidized apoA-I. Oxidation of specific residues in apoA-I inhibited two key steps in cholesterol efflux from macrophages, raising the possibility that MPO initiates a pathway for generating dysfunctional HDL in humans.
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Affiliation(s)
- Baohai Shao
- Department of Medicine, University of Washington, 815 Mercer Street, Seattle, Washington 98109, USA.
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68
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Cavigiolio G, Geier EG, Shao B, Heinecke JW, Oda MN. Exchange of apolipoprotein A-I between lipid-associated and lipid-free states: a potential target for oxidative generation of dysfunctional high density lipoproteins. J Biol Chem 2010; 285:18847-57. [PMID: 20385548 DOI: 10.1074/jbc.m109.098434] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
An important event in cholesterol metabolism is the efflux of cellular cholesterol by apolipoprotein A-I (apoA-I), the major protein of high density lipoproteins (HDL). Lipid-free apoA-I is the preferred substrate for ATP-binding cassette A1, which promotes cholesterol efflux from macrophage foam cells in the arterial wall. However, the vast majority of apoA-I in plasma is associated with HDL, and the mechanisms for the generation of lipid-free apoA-I remain poorly understood. In the current study, we used fluorescently labeled apoA-I that exhibits a distinct fluorescence emission spectrum when in different states of lipid association to establish the kinetics of apoA-I transition between the lipid-associated and lipid-free states. This approach characterized the spontaneous and rapid exchange of apoA-I between the lipid-associated and lipid-free states. In contrast, the kinetics of apoA-I exchange were significantly reduced when apoA-I on HDL was cross-linked with a bi-functional reagent or oxidized by myeloperoxidase. Our observations support the hypothesis that oxidative damage to apoA-I by myeloperoxidase limits the ability of apoA-I to be liberated in a lipid-free form from HDL. This impairment of apoA-I exchange reaction may be a trait of dysfunctional HDL contributing to reduced ATP-binding cassette A1-mediated cholesterol efflux and atherosclerosis.
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Affiliation(s)
- Giorgio Cavigiolio
- Children's Hospital Oakland Research Institute, Oakland, California 94609, USA
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69
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Jones MK, Catte A, Li L, Segrest JP. Dynamics of activation of lecithin:cholesterol acyltransferase by apolipoprotein A-I. Biochemistry 2009; 48:11196-210. [PMID: 19860440 DOI: 10.1021/bi901242k] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The product of transesterification of phospholipid acyl chains and unesterified cholesterol (UC) by the enzyme lecithin:cholesterol acyltransferase (LCAT) is cholesteryl ester (CE). Activation of LCAT by apolipoprotein (apo) A-I on nascent (discoidal) high-density lipoproteins (HDL) is essential for formation of mature (spheroidal) HDL during the antiatherogenic process of reverse cholesterol transport. Here we report all-atom and coarse-grained (CG) molecular dynamics (MD) simulations of HDL particles that have major implications for mechanisms of LCAT activation. Both the all-atom and CG simulations provide support for a model in which the helix 5/5 domains of apoA-I create an amphipathic "presentation tunnel" that exposes methyl ends of acyl chains at the bilayer center to solvent. Further, CG simulations show that UC also becomes inserted with high efficiency into the amphipathic presentation tunnel with its hydroxyl moiety (UC-OH) exposed to solvent; these results are consistent with trajectory analyses of the all-atom simulations showing that UC is being concentrated in the vicinity of the presentation tunnel. Finally, consistent with known product inhibition of CE-rich HDL by CE, CG simulations of CE-rich spheroidal HDL indicate partial blockage of the amphipathic presentation tunnel by CE. These results lead us to propose the following working hypothesis. After attachment of LCAT to discoidal HDL, the helix 5/5 domains in apoA-I form amphipathic presentation tunnels for migration of hydrophobic acyl chains and amphipathic UC from the bilayer to the phospholipase A2-like and esterification active sites of LCAT, respectively. This hypothesis is currently being tested by site-directed mutagenesis.
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Affiliation(s)
- Martin K Jones
- Department of Medicine and Atherosclerosis Research Unit, University ofAlabama, Birmingham, Alabama 35294, USA
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70
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Gu F, Jones MK, Chen J, Patterson JC, Catte A, Jerome WG, Li L, Segrest JP. Structures of discoidal high density lipoproteins: a combined computational-experimental approach. J Biol Chem 2009; 285:4652-65. [PMID: 19948731 DOI: 10.1074/jbc.m109.069914] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Conversion of discoidal phospholipid (PL)-rich high density lipoprotein (HDL) to spheroidal cholesteryl ester-rich HDL is a central step in reverse cholesterol transport. A detailed understanding of this process and the atheroprotective role of apolipoprotein A-I (apoA-I) requires knowledge of the structure and dynamics of these various particles. This study, combining computation with experimentation, illuminates structural features of apoA-I allowing it to incorporate varying amounts of PL. Molecular dynamics simulated annealing of PL-rich HDL models containing unesterified cholesterol results in double belt structures with the same general saddle-shaped conformation of both our previous molecular dynamics simulations at 310 K and the x-ray structure of lipid-free apoA-I. Conversion from a discoidal to a saddle-shaped particle involves loss of helicity and formation of loops in opposing antiparallel parts of the double belt. During surface expansion caused by the temperature-jump step, the curved palmitoyloleoylphosphatidylcholine bilayer surfaces approach planarity. Relaxation back into saddle-shaped structures after cool down and equilibration further supports the saddle-shaped particle model. Our kinetic analyses of reconstituted particles demonstrate that PL-rich particles exist in discrete sizes corresponding to local energetic minima. Agreement of experimental and computational determinations of particle size/shape and apoA-I helicity provide additional support for the saddle-shaped particle model. Truncation experiments combined with simulations suggest that the N-terminal proline-rich domain of apoA-I influences the stability of PL-rich HDL particles. We propose that apoA-I incorporates increasing PL in the form of minimal surface bilayers through the incremental unwinding of an initially twisted saddle-shaped apoA-I double belt structure.
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Affiliation(s)
- Feifei Gu
- Department of Medicine and Atherosclerosis Research Unit, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
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71
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Wong-Mauldin K, Raussens V, Forte TM, Ryan RO. Apolipoprotein A-V N-terminal domain lipid interaction properties in vitro explain the hypertriglyceridemic phenotype associated with natural truncation mutants. J Biol Chem 2009; 284:33369-76. [PMID: 19825998 DOI: 10.1074/jbc.m109.040972] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The N-terminal 146 residues of apolipoprotein (apo) A-V adopt a helix bundle conformation in the absence of lipid. Because similarly sized truncation mutants in human subjects correlate with severe hypertriglyceridemia, the lipid binding properties of apoA-V(1-146) were studied. Upon incubation with phospholipid in vitro, apoA-V(1-146) forms reconstituted high density lipoproteins 15-17 nm in diameter. Far UV circular dichroism spectroscopy analyses of lipid-bound apoA-V(1-146) yielded an alpha-helix secondary structure content of 60%. Fourier transformed infrared spectroscopy analysis revealed that apoA-V(1-146) alpha-helix segments align perpendicular with respect to particle phospholipid fatty acyl chains. Fluorescence spectroscopy of single Trp variant apoA-V(1-146) indicates that lipid interaction is accompanied by a conformational change. The data are consistent with a model wherein apoA-V(1-146) alpha-helices circumscribe the perimeter of a disk-shaped bilayer. The ability of apoA-V(1-146) to solubilize dimyristoylphosphatidylcholine vesicles at a rate faster than full-length apoA-V suggests that N- and C-terminal interactions in the full-length protein modulate its lipid binding properties. Preferential association of apoA-V(1-146) with murine plasma HDL, but not with VLDL, suggests that particle size is a determinant of its lipoprotein binding specificity. It may be concluded that defective lipoprotein binding of truncated apoA-V contributes to the hypertriglyceridemia phenotype associated with truncation mutations in human subjects.
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Affiliation(s)
- Kasuen Wong-Mauldin
- Center for Prevention of Obesity, Diabetes and Cardiovascular Disease, Children's Hospital Oakland Research Institute, Oakland, California 94609, USA
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72
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Wu Z, Gogonea V, Lee X, Wagner MA, Li XM, Huang Y, Undurti A, May RP, Haertlein M, Moulin M, Gutsche I, Zaccai G, DiDonato JA, Hazen SL. Double superhelix model of high density lipoprotein. J Biol Chem 2009; 284:36605-36619. [PMID: 19812036 DOI: 10.1074/jbc.m109.039537] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
High density lipoprotein (HDL), the carrier of so-called "good" cholesterol, serves as the major athero-protective lipoprotein and has emerged as a key therapeutic target for cardiovascular disease. We applied small angle neutron scattering (SANS) with contrast variation and selective isotopic deuteration to the study of nascent HDL to obtain the low resolution structure in solution of the overall time-averaged conformation of apolipoprotein AI (apoA-I) versus the lipid (acyl chain) core of the particle. Remarkably, apoA-I is observed to possess an open helical shape that wraps around a central ellipsoidal lipid phase. Using the low resolution SANS shapes of the protein and lipid core as scaffolding, an all-atom computational model for the protein and lipid components of nascent HDL was developed by integrating complementary structural data from hydrogen/deuterium exchange mass spectrometry and previously published constraints from multiple biophysical techniques. Both SANS data and the new computational model, the double superhelix model, suggest an unexpected structural arrangement of protein and lipids of nascent HDL, an anti-parallel double superhelix wrapped around an ellipsoidal lipid phase. The protein and lipid organization in nascent HDL envisages a potential generalized mechanism for lipoprotein biogenesis and remodeling, biological processes critical to sterol and lipid transport, organismal energy metabolism, and innate immunity.
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Affiliation(s)
- Zhiping Wu
- Department of Cell Biology, Cleveland Clinic, Cleveland, Ohio 44195; Center for Cardiovascular Diagnostics and Prevention, Cleveland Clinic, Cleveland, Ohio 44195
| | - Valentin Gogonea
- Department of Cell Biology, Cleveland Clinic, Cleveland, Ohio 44195; Department of Chemistry, Cleveland State University, Cleveland, Ohio 44115
| | - Xavier Lee
- Department of Cell Biology, Cleveland Clinic, Cleveland, Ohio 44195; Center for Cardiovascular Diagnostics and Prevention, Cleveland Clinic, Cleveland, Ohio 44195
| | - Matthew A Wagner
- Department of Cell Biology, Cleveland Clinic, Cleveland, Ohio 44195; Center for Cardiovascular Diagnostics and Prevention, Cleveland Clinic, Cleveland, Ohio 44195
| | - Xin-Min Li
- Department of Cell Biology, Cleveland Clinic, Cleveland, Ohio 44195; Center for Cardiovascular Diagnostics and Prevention, Cleveland Clinic, Cleveland, Ohio 44195
| | - Ying Huang
- Department of Cell Biology, Cleveland Clinic, Cleveland, Ohio 44195; Center for Cardiovascular Diagnostics and Prevention, Cleveland Clinic, Cleveland, Ohio 44195
| | - Arundhati Undurti
- Department of Cell Biology, Cleveland Clinic, Cleveland, Ohio 44195; Center for Cardiovascular Diagnostics and Prevention, Cleveland Clinic, Cleveland, Ohio 44195
| | - Roland P May
- Institut Laue-Langevin, 6 Rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9, France
| | - Michael Haertlein
- Institut Laue-Langevin, 6 Rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9, France
| | - Martine Moulin
- Institut Laue-Langevin, 6 Rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9, France
| | - Irina Gutsche
- Unit of Virus-Host Interaction, Unité Mixte de Recherche 5233 Université Joseph Fourier-European Molecular Biology Laboratory-CNRS, 6 Rue Jules Horowitz, BP 181, 38042 Grenoble Cedex 9, France
| | - Giuseppe Zaccai
- Institut Laue-Langevin, 6 Rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9, France; Institut de Biologie Structurale, Commissariat à l'Energie Atomique-CNRS-Université Joseph Fourier, 38027 Grenoble, France
| | - Joseph A DiDonato
- Department of Cell Biology, Cleveland Clinic, Cleveland, Ohio 44195; Center for Cardiovascular Diagnostics and Prevention, Cleveland Clinic, Cleveland, Ohio 44195
| | - Stanley L Hazen
- Department of Cell Biology, Cleveland Clinic, Cleveland, Ohio 44195; Center for Cardiovascular Diagnostics and Prevention, Cleveland Clinic, Cleveland, Ohio 44195; Department of Cardiovascular Medicine, Cleveland Clinic, Cleveland, Ohio 44195.
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73
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Narayanaswami V, Kiss RS, Weers PMM. The helix bundle: a reversible lipid binding motif. Comp Biochem Physiol A Mol Integr Physiol 2009; 155:123-33. [PMID: 19770066 DOI: 10.1016/j.cbpa.2009.09.009] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2009] [Revised: 09/09/2009] [Accepted: 09/11/2009] [Indexed: 01/01/2023]
Abstract
Apolipoproteins are the protein components of lipoproteins that have the innate ability to inter convert between a lipid-free and a lipid-bound form in a facile manner, a remarkable property conferred by the helix bundle motif. Composed of a series of four or five amphipathic alpha-helices that fold to form a helix bundle, this motif allows the en face orientation of the hydrophobic faces of the alpha-helices in the protein interior in the lipid-free state. A conformational switch then permits helix-helix interactions to be substituted by helix-lipid interactions upon lipid binding interaction. This review compares the apolipoprotein high-resolution structures and the factors that trigger this switch in insect apolipophorin III and the mammalian apolipoproteins, apolipoprotein E and apolipoprotein A-I, pointing out the commonalities and key differences in the mode of lipid interaction. Further insights into the lipid-bound conformation of apolipoproteins are required to fully understand their functional role under physiological conditions.
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Affiliation(s)
- Vasanthy Narayanaswami
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach CA 90840, USA
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74
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Chen B, Ren X, Neville T, Jerome WG, Hoyt DW, Sparks D, Ren G, Wang J. Apolipoprotein AI tertiary structures determine stability and phospholipid-binding activity of discoidal high-density lipoprotein particles of different sizes. Protein Sci 2009; 18:921-35. [PMID: 19384992 DOI: 10.1002/pro.101] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Human high-density lipoprotein (HDL) plays a key role in the reverse cholesterol transport pathway that delivers excess cholesterol back to the liver for clearance. In vivo, HDL particles vary in size, shape and biological function. The discoidal HDL is a 140-240 kDa, disk-shaped intermediate of mature HDL. During mature spherical HDL formation, discoidal HDLs play a key role in loading cholesterol ester onto the HDL particles by activating the enzyme, lecithin:cholesterol acyltransferase (LCAT). One of the major problems for high-resolution structural studies of discoidal HDL is the difficulty in obtaining pure and, foremost, homogenous sample. We demonstrate here that the commonly used cholate dialysis method for discoidal HDL preparation usually contains 5-10% lipid-poor apoAI that significantly interferes with the high-resolution structural analysis of discoidal HDL using biophysical methods. Using an ultracentrifugation method, we quickly removed lipid-poor apoAI. We also purified discoidal reconstituted HDL (rHDL) into two pure discoidal HDL species of different sizes that are amendable for high-resolution structural studies. A small rHDL has a diameter of 7.6 nm, and a large rHDL has a diameter of 9.8 nm. We show that these two different sizes of discoidal HDL particles display different stability and phospholipid-binding activity. Interestingly, these property/functional differences are independent from the apoAI alpha-helical secondary structure, but are determined by the tertiary structural difference of apoAI on different discoidal rHDL particles, as evidenced by two-dimensional NMR and negative stain electron microscopy data. Our result further provides the first high-resolution NMR data, demonstrating a promise of structural determination of discoidal HDL at atomic resolution using a combination of NMR and other biophysical techniques.
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Affiliation(s)
- Bin Chen
- Department of Biochemistry and Molecular Biology, School of Medicine, Wayne State University, Detroit, Michigan 48201, USA
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75
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Nakano M, Fukuda M, Kudo T, Miyazaki M, Wada Y, Matsuzaki N, Endo H, Handa T. Static and Dynamic Properties of Phospholipid Bilayer Nanodiscs. J Am Chem Soc 2009; 131:8308-12. [DOI: 10.1021/ja9017013] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Minoru Nakano
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan, and Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Masakazu Fukuda
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan, and Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Takayuki Kudo
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan, and Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Masakazu Miyazaki
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan, and Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Yusuke Wada
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan, and Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Naoya Matsuzaki
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan, and Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Hitoshi Endo
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan, and Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Tetsurou Handa
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan, and Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
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76
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Jones MK, Catte A, Patterson JC, Gu F, Chen J, Li L, Segrest JP. Thermal stability of apolipoprotein A-I in high-density lipoproteins by molecular dynamics. Biophys J 2009; 96:354-71. [PMID: 19167289 DOI: 10.1016/j.bpj.2008.09.041] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2008] [Accepted: 09/22/2008] [Indexed: 02/06/2023] Open
Abstract
Apolipoprotein (apo) A-I is an unusually flexible protein whose lipid-associated structure is poorly understood. Thermal denaturation, which is used to measure the global helix stability of high-density lipoprotein (HDL)-associated apoA-I, provides no information about local helix stability. Here we report the use of temperature jump molecular dynamics (MD) simulations to scan the per-residue helix stability of apoA-I in phospholipid-rich HDL. When three 20 ns MD simulations were performed at 500 K on each of two particles created by MD simulations at 310 K, bilayers remained intact but expanded by 40%, and total apoA-I helicity decreased from 95% to 72%. Of significance, the conformations of the overlapping N- and C-terminal domains of apoA-I in the particles were unusually mobile, exposing hydrocarbon regions of the phospholipid to solvent; a lack of buried interhelical salt bridges in the terminal domains correlated with increased mobility. Nondenaturing gradient gels show that 40% expansion of the phospholipid surface of 100:2 particles by addition of palmitoyloleoylphosphatidylcholine exceeds the threshold of particle stability. As a unifying hypothesis, we propose that the terminal domains of apoA-I are phospholipid concentration-sensitive molecular triggers for fusion/remodeling of HDL particles. Since HDL remodeling is necessary for cholesterol transport, our model for remodeling has substantial biomedical implications.
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Affiliation(s)
- Martin K Jones
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA
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77
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Sorci-Thomas MG, Bhat S, Thomas MJ. Activation of lecithin:cholesterol acyltransferase by HDL ApoA-I central helices. CLINICAL LIPIDOLOGY 2009; 4:113-124. [PMID: 20582235 PMCID: PMC2891274 DOI: 10.2217/17584299.4.1.113] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Lecithin:cholesterol acyltransferase (LCAT) is an enzyme that first hydrolyzes the sn-2 position of phospholipids, preferentially a diacylphosphocholine, and then transfers the fatty acid to cholesterol to yield a cholesteryl ester. HDL ApoA-I is the principal catalytic activator for LCAT. Activity of LCAT on nascent or lipid-poor HDL particles composed of phospholipid, cholesterol and ApoA-I allows the maturation of HDL particles into lipid-rich spherical particles that contain a core of cholesteryl ester surrounded by phospholipid and ApoA-I on the surface. This article reviews the recent progress in elucidating structural aspects of the interaction between LCAT and ApoA-I. In the last decade, there has been considerable progress in understanding the structure of ApoA-I and the central helices 5, 6, and 7 that are known to activate LCAT. However, much less information has been forthcoming describing the 3D structure and conformation of LCAT required to catalyze two separate reactions within a single monomeric peptide.
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Affiliation(s)
- Mary G Sorci-Thomas
- Department of Pathology, Wake Forest University School of Medicine, Medical Center Blvd, Winston-Salem, NC 27157-1016, USA, Tel.: +1 336 716 2147, Fax: +1 336 716 6279,
| | - Shaila Bhat
- Department of Pathology, Lipid Sciences Research Center, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA, Tel.: +1 336 716 6062, Fax: +1 336 716 6279,
| | - Michael J Thomas
- Department of Biochemistry, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA, Tel.: +1 336 716 2313, Fax: +1 336 716 6279,
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78
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Tufteland M, Ren G, Ryan RO. Nanodisks derived from amphotericin B lipid complex. J Pharm Sci 2009; 97:4425-32. [PMID: 18271034 DOI: 10.1002/jps.21325] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The goal of this study was to determine the effect of apolipoproteins on Amphotericin B lipid complex (ABLC). We report that incubation of ABLC with recombinant human apolipoprotein A-I (apoA-I) induces solubilization of ABLC by transforming the micron sized phospholipid/AMB assemblies into discrete nanoscale disk-shaped complexes termed nanodisks (ND). ApoA-I induced changes in ABLC solubility and morphology were monitored by spectroscopy and electron microscopy. AMB efficacy was evaluated in yeast and pathogenic fungi growth inhibition assays and the effect of AMB formulation on cell toxicity was assessed in cultured Hep3B cells. AMB associated with ND were more efficiently nebulized than AMB associated with ABLC. Thus, transformation of ABLC into ND preserves the potent biological activity of AMB as well as the reduced toxicity of the ABLC formulation. ABLC derived AMB-ND offer advantages over conventional ABLC in terms of stability, storage, nebulization efficiency and provides an intrinsic "handle" for tissue specific targeting via genetic engineering of its protein component.
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Affiliation(s)
- Megan Tufteland
- Center for Prevention of Obesity, Diabetes & Cardiovascular Diseases, Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr. Way, Oakland, California 94609, USA
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79
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Massey JB, Pownall HJ, Macha S, Morris J, Tubb MR, Silva RAGD. Mass spectrometric determination of apolipoprotein molecular stoichiometry in reconstituted high density lipoprotein particles. J Lipid Res 2009; 50:1229-36. [PMID: 19179308 DOI: 10.1194/jlr.d800044-jlr200] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Plasma HDL-cholesterol and apolipoprotein A-I (apoA-I) levels are strongly inversely associated with cardiovascular disease. However, the structure and protein composition of HDL particles is complex, as native and synthetic discoidal and spherical HDL particles can have from two to five apoA-I molecules per particle. To fully understand structure-function relationships of HDL, a method is required that is capable of directly determining the number of apolipoprotein molecules in heterogeneous HDL particles. Chemical cross-linking followed by SDS polyacrylamide gradient gel electrophoresis has been previously used to determine apolipoprotein stoichiometry in HDL particles. However, this method yields ambiguous results due to effects of cross-linking on protein conformation and, subsequently, its migration pattern on the gel. Here, we describe a new method based on cross-linking chemistry followed by MALDI mass spectrometry that determines the absolute mass of the cross-linked complex, thereby correctly determining the number of apolipoprotein molecules in a given HDL particle. Using well-defined, homogeneous, reconstituted apoA-I-containing HDL, apoA-IV-containing HDL, as well as apoA-I/apoA-II-containing HDL, we have validated this method. The method has the capability to determine the molecular ratio and molecular composition of apolipoprotein molecules in complex reconstituted HDL particles.
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Affiliation(s)
- John B Massey
- Section of Atherosclerosis and Vascular Medicine, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA
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80
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Hatters DM, Voss JC, Budamagunta MS, Newhouse YN, Weisgraber KH. Insight on the molecular envelope of lipid-bound apolipoprotein E from electron paramagnetic resonance spectroscopy. J Mol Biol 2008; 386:261-71. [PMID: 19124026 DOI: 10.1016/j.jmb.2008.12.040] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2008] [Revised: 12/04/2008] [Accepted: 12/10/2008] [Indexed: 10/21/2022]
Abstract
Although a high-resolution X-ray structure for the N-terminal domain of apolipoprotein E (apoE) in the lipid-free state has been solved, our knowledge of the structure of full-length apoE in a lipid-bound state is limited to an X-ray model fitting a molecular envelope at 10-A resolution. To add molecular detail to the molecular envelope, we used cysteine mutagenesis to incorporate spin labels for analysis with electron paramagnetic resonance (EPR) spectroscopy. Twelve cysteine residues were introduced singly and in pairs at unique locations throughout apoE4 and labeled with an EPR spin probe. The labeled apoE4 was combined with dipalmitoylphosphatidylcholine, the particles were purified, and spectra were determined for 24 combinations (single and double) of the cysteine mutants. Data on the conformation, mobility, distance, and surface exposure of regions revealed by the cysteine probes were modeled into the molecular envelope of apoE bound to dipalmitoylphosphatidylcholine that had been determined by X-ray analysis. This EPR model of apoE in a native lipid-bound state validates the structural model derived from X-ray analysis and provides additional insight into apoE structure-function relationships.
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Affiliation(s)
- Danny M Hatters
- Gladstone Institutes of Cardiovascular and Neurological Diseases, 1650 Owens Street, San Francisco, CA 94158, USA
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81
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Kono M, Okumura Y, Tanaka M, Nguyen D, Dhanasekaran P, Lund-Katz S, Phillips MC, Saito H. Conformational flexibility of the N-terminal domain of apolipoprotein a-I bound to spherical lipid particles. Biochemistry 2008; 47:11340-7. [PMID: 18831538 DOI: 10.1021/bi801503r] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Lipid binding of human apolipoprotein A-I (apoA-I) occurs initially through the C-terminal alpha-helices followed by conformational reorganization of the N-terminal helix bundle. This led us to hypothesize that apoA-I has multiple lipid-bound conformations, in which the N-terminal helix bundle adopts either open or closed conformations anchored by the C-terminal domain. To investigate such possible conformations of apoA-I at the surface of a spherical lipid particle, site-specific labeling of the N- and C-terminal helices in apoA-I by N-(1-pyrene)maleimide was employed after substitution of a Cys residue for Val-53 or Phe-229. Neither mutagenesis nor the pyrene labeling caused discernible changes in the lipid-free structure and lipid interaction of apoA-I. Taking advantage of a significant increase in fluorescence when a pyrene-labeled helix is in contact with the lipid surface, we monitored the behaviors of the N- and C-terminal helices upon binding of apoA-I to egg PC small unilamellar vesicles. Comparison of the binding isotherms for pyrene-labeled apoA-I as well as a C-terminal helical peptide suggests that an increase in surface concentration of apoA-I causes dissociation of the N-terminal helix from the surface leaving the C-terminal helix attached. Consistent with this, isothermal titration calorimetry measurements showed that the enthalpy of apoA-I binding to the lipid surface under near saturated conditions is much less exothermic than that for binding at a low surface concentration, indicating the N-terminal helix bundle is out of contact with lipid at high apoA-I surface concentrations. Interestingly, the presence of cholesterol significantly induces the open conformation of the helix bundle. These results provide insight into the multiple lipid-bound conformations that the N-terminal helix bundle of apoA-I can adopt on a lipid or lipoprotein particle, depending upon the availability of space on the surface and the surface composition.
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Affiliation(s)
- Momoe Kono
- Department of Biophysical Chemistry, Kobe Pharmaceutical University, Kobe 658-8558, Japan
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82
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Methionine oxidation impairs reverse cholesterol transport by apolipoprotein A-I. Proc Natl Acad Sci U S A 2008; 105:12224-9. [PMID: 18719109 DOI: 10.1073/pnas.0802025105] [Citation(s) in RCA: 139] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
HDL protects against vascular disease by accepting free cholesterol from macrophage foam cells in the artery wall. This pathway is critically dependent on lecithin:cholesterol acyltransferase (LCAT), which rapidly converts cholesterol to cholesteryl ester. The physiological activator of LCAT is apolipoprotein A-I (apoA-I), the major HDL protein. However, cholesterol removal is compromised if apoA-I is exposed to reactive intermediates. In humans with established cardiovascular disease, myeloperoxidase (MPO) oxidizes HDL, and oxidation by MPO impairs apoA-I's ability to activate LCAT in vitro. Because a single methionine residue in apoA-I, Met-148, resides near the center of the protein's LCAT activation domain, we determined whether its oxidation by MPO could account for the loss of LCAT activity. Mass spectrometric analysis demonstrated that oxidation of Met-148 to methionine sulfoxide associated quantitatively with loss of LCAT activity in both discoidal HDL and HDL(3), the enzyme's physiological substrates. Reversing oxidation with methionine sulfoxide reductase restored HDL's ability to activate LCAT. Discoidal HDL prepared with apoA-I containing a Met-148-->Leu mutation was significantly resistant to inactivation by MPO. Based on structural data in the literature, we propose that oxidation of Met-148 disrupts apoA-I's central loop, which overlaps the LCAT activation domain. These observations implicate oxidation of a single Met in apoA-I in impaired LCAT activation, a critical early step in reverse cholesterol transport.
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83
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Structure of apolipoprotein A-I in spherical high density lipoproteins of different sizes. Proc Natl Acad Sci U S A 2008; 105:12176-81. [PMID: 18719128 DOI: 10.1073/pnas.0803626105] [Citation(s) in RCA: 163] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Spherical high density lipoproteins (HDL) predominate in human plasma. However, little information exists on the structure of the most common HDL protein, apolipoprotein (apo) A-I, in spheres vs. better studied discoidal forms. We produced spherical HDL by incubating reconstituted discoidal HDL with physiological plasma-remodeling enzymes and compared apoA-I structure in discs and spheres of comparable diameter (79-80 and 93-96 A). Using cross-linking chemistry and mass spectrometry, we determined that the general structural organization of apoA-I was overall similar between discs and spheres, regardless of diameter. This was the case despite the fact that the 93 A spheres contained three molecules of apoA-I per particle compared with only two in the discs. Thus, apoA-I adopts a consistent general structural framework in HDL particles-irrespective of shape, size and the number of apoA-Is present. Furthermore, a similar cross-linking pattern was demonstrated in HDL particles isolated from human serum. We propose the first experiment-based molecular model of apoA-I in spherical HDL particles. This model provides a new foundation for understanding how apoA-I structure modulates HDL function and metabolism.
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84
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Vinchurkar MS, Bricarello DA, Lagerstedt JO, Buban JP, Stahlberg H, Oda MN, Voss JC, Parikh AN. Bridging Across Length Scales: Multi-Scale Ordering of Supported Lipid Bilayers via Lipoprotein Self-assembly and Surface Patterning. J Am Chem Soc 2008; 130:11164-9. [DOI: 10.1021/ja803110v] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Madhuri S. Vinchurkar
- Departments of Applied Science, Biochemistry & Molecular Medicine, Molecular and Cellular Biology, University of California, Davis, California 95616, and Lipid Biology in Health and Disease Research Group, Oakland Research Institute, Oakland, California 94609
| | - Daniel A. Bricarello
- Departments of Applied Science, Biochemistry & Molecular Medicine, Molecular and Cellular Biology, University of California, Davis, California 95616, and Lipid Biology in Health and Disease Research Group, Oakland Research Institute, Oakland, California 94609
| | - Jens O. Lagerstedt
- Departments of Applied Science, Biochemistry & Molecular Medicine, Molecular and Cellular Biology, University of California, Davis, California 95616, and Lipid Biology in Health and Disease Research Group, Oakland Research Institute, Oakland, California 94609
| | - James P. Buban
- Departments of Applied Science, Biochemistry & Molecular Medicine, Molecular and Cellular Biology, University of California, Davis, California 95616, and Lipid Biology in Health and Disease Research Group, Oakland Research Institute, Oakland, California 94609
| | - Henning Stahlberg
- Departments of Applied Science, Biochemistry & Molecular Medicine, Molecular and Cellular Biology, University of California, Davis, California 95616, and Lipid Biology in Health and Disease Research Group, Oakland Research Institute, Oakland, California 94609
| | - Michael N. Oda
- Departments of Applied Science, Biochemistry & Molecular Medicine, Molecular and Cellular Biology, University of California, Davis, California 95616, and Lipid Biology in Health and Disease Research Group, Oakland Research Institute, Oakland, California 94609
| | - John C. Voss
- Departments of Applied Science, Biochemistry & Molecular Medicine, Molecular and Cellular Biology, University of California, Davis, California 95616, and Lipid Biology in Health and Disease Research Group, Oakland Research Institute, Oakland, California 94609
| | - Atul N. Parikh
- Departments of Applied Science, Biochemistry & Molecular Medicine, Molecular and Cellular Biology, University of California, Davis, California 95616, and Lipid Biology in Health and Disease Research Group, Oakland Research Institute, Oakland, California 94609
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85
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Carnemolla R, Ren X, Biswas TK, Meredith SC, Reardon CA, Wang J, Getz GS. The specific amino acid sequence between helices 7 and 8 influences the binding specificity of human apolipoprotein A-I for high density lipoprotein (HDL) subclasses: a potential for HDL preferential generation. J Biol Chem 2008; 283:15779-88. [PMID: 18385132 PMCID: PMC2414305 DOI: 10.1074/jbc.m710244200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2007] [Revised: 04/01/2008] [Indexed: 02/02/2023] Open
Abstract
Humans have two major high density lipoprotein (HDL) sub-fractions, HDL(2) and HDL(3), whereas mice have a monodisperse HDL profile. Epidemiological evidence has suggested that HDL(2) is more atheroprotective; however, currently there is no direct experimental evidence to support this postulate. The amino acid sequence of apoA-I is a primary determinant of HDL subclass formation. The majority of the alpha-helical repeats in human apoA-I are proline-punctuated. A notable exception is the boundary between helices 7 and 8, which is located in the transitional segment between the stable N-terminal domain and the C-terminal hydrophobic domain. In this study we ask whether the substitution of a proline-containing sequence (PCS) separating other helices in human apoA-I for the non-proline-containing sequence (NPCS) between helices 7 and 8 (residues 184-190) influences HDL subclass association. The human apoA-I mutant with PCS2 replacing NPCS preferentially bound to HDL(2). In contrast, the mutant where PCS3 replaced NPCS preferentially associated with HDL(3). Thus, the specific amino acid sequence between helices 7 and 8 influences HDL subclass association. The wild-type and mutant proteins exhibited similar physicochemical properties except that the two mutants displayed greater lipid-associated stability versus wild-type human apoA-I. These results focus new attention on the influence of the boundary between helices 7 and 8 on the properties of apoA-I. The expression of these mutants in mice may result in the preferential generation of HDL(2) or HDL(3) and allow us to examine experimentally the anti-atherogenicity of the HDL subclasses.
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Affiliation(s)
- Ronald Carnemolla
- Department of Pathology and the
Committee of Molecular Metabolism and Nutrition,
The University of Chicago, Chicago, Illinois 60637 and the
Department of Biochemistry and Molecular
Biology, Wayne State University, Detroit, Michigan 48201
| | - Xuefeng Ren
- Department of Pathology and the
Committee of Molecular Metabolism and Nutrition,
The University of Chicago, Chicago, Illinois 60637 and the
Department of Biochemistry and Molecular
Biology, Wayne State University, Detroit, Michigan 48201
| | - Tapan K. Biswas
- Department of Pathology and the
Committee of Molecular Metabolism and Nutrition,
The University of Chicago, Chicago, Illinois 60637 and the
Department of Biochemistry and Molecular
Biology, Wayne State University, Detroit, Michigan 48201
| | - Stephen C. Meredith
- Department of Pathology and the
Committee of Molecular Metabolism and Nutrition,
The University of Chicago, Chicago, Illinois 60637 and the
Department of Biochemistry and Molecular
Biology, Wayne State University, Detroit, Michigan 48201
| | - Catherine A. Reardon
- Department of Pathology and the
Committee of Molecular Metabolism and Nutrition,
The University of Chicago, Chicago, Illinois 60637 and the
Department of Biochemistry and Molecular
Biology, Wayne State University, Detroit, Michigan 48201
| | - Jianjun Wang
- Department of Pathology and the
Committee of Molecular Metabolism and Nutrition,
The University of Chicago, Chicago, Illinois 60637 and the
Department of Biochemistry and Molecular
Biology, Wayne State University, Detroit, Michigan 48201
| | - Godfrey S. Getz
- Department of Pathology and the
Committee of Molecular Metabolism and Nutrition,
The University of Chicago, Chicago, Illinois 60637 and the
Department of Biochemistry and Molecular
Biology, Wayne State University, Detroit, Michigan 48201
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86
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Thomas MJ, Bhat S, Sorci-Thomas MG. Three-dimensional models of HDL apoA-I: implications for its assembly and function. J Lipid Res 2008; 49:1875-83. [PMID: 18515783 DOI: 10.1194/jlr.r800010-jlr200] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The purpose of this review is to highlight recent advances toward the refinement of a three-dimensional structure for lipid-bound apolipoprotein A-I (apoA-I) on recombinant HDL. Recently, X-ray crystallography has yielded a new structure for full-length, lipid-free apoA-I. Although this approach has not yet been successful in solving the three-dimensional structure of lipid-bound apoA-I, analysis of the X-ray structures has been of immense help in the interpretation of structural data obtained from other methods that yield structural information. Recent studies emphasize the use of mass spectrometry to unambiguously identify cross-linked peptides or to quantify solvent accessibility using hydrogen-deuterium exchange. The combination of mass spectrometry, molecular modeling, molecular dynamic analysis, and small-angle X-ray diffraction has provided additional structural information on apoA-I folding that complements previous approaches.
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Affiliation(s)
- Michael J Thomas
- Department of Biochemistry, Section on Lipid Sciences, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA.
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87
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Cavigiolio G, Shao B, Geier EG, Ren G, Heinecke JW, Oda MN. The interplay between size, morphology, stability, and functionality of high-density lipoprotein subclasses. Biochemistry 2008; 47:4770-9. [PMID: 18366184 DOI: 10.1021/bi7023354] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
High-density lipoprotein (HDL) mediates reverse cholesterol transport (RCT), wherein excess cholesterol is conveyed from peripheral tissues to the liver and steroidogenic organs. During this process HDL continually transitions between subclass sizes, each with unique biological activities. For instance, RCT is initiated by the interaction of lipid-free/lipid-poor apolipoprotein A-I (apoA-I) with ABCA1, a membrane-associated lipid transporter, to form nascent HDL. Because nearly all circulating apoA-I is lipid-bound, the source of lipid-free/lipid-poor apoA-I is unclear. Lecithin:cholesterol acyltransferase (LCAT) then drives the conversion of nascent HDL to spherical HDL by catalyzing cholesterol esterification, an essential step in RCT. To investigate the relationship between HDL particle size and events critical to RCT such as LCAT activation and lipid-free apoA-I production for ABCA1 interaction, we reconstituted five subclasses of HDL particles (rHDL of 7.8, 8.4, 9.6, 12.2, and 17.0 nm in diameter, respectively) using various molar ratios of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, free cholesterol, and apoA-I. Kinetic analyses of this comprehensive array of rHDL particles suggest that apoA-I stoichiometry in rHDL is a critical factor governing LCAT activation. Electron microscopy revealed specific morphological differences in the HDL subclasses that may affect functionality. Furthermore, stability measurements demonstrated that the previously uncharacterized 8.4 nm rHDL particles rapidly convert to 7.8 nm particles, concomitant with the dissociation of lipid-free/lipid-poor apoA-I. Thus, lipid-free/lipid-poor apoA-I generated by the remodeling of HDL may be an essential intermediate in RCT and HDL's in vivo maturation.
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88
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Graversen JH, Castro G, Kandoussi A, Nielsen H, Christensen EI, Norden A, Moestrup SK. A pivotal role of the human kidney in catabolism of HDL protein components apolipoprotein A-I and A-IV but not of A-II. Lipids 2008; 43:467-70. [PMID: 18350327 DOI: 10.1007/s11745-008-3169-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2007] [Accepted: 02/27/2008] [Indexed: 11/25/2022]
Abstract
Renal handling of major HDL components was studied by analyzing urine from patients with Fanconi syndrome, a rare renal proximal tubular reabsorption failure, including dysfunction of the kidney HDL receptor, cubilin. A high urinary excretion of apolipoprotein A-I and A-IV corresponding to a major part of the metabolism of these proteins was measured. In contrast, no urinary excretion of apolipoprotein A-II which is more hydrophobic and tighter bound to HDL was found. Control urines displayed absence of the three apolipoproteins. Urinary excretion of phospholipids, triglycerides, cholesterol and cholesterol esters in patients was as low as in controls. In conclusion, these data indicate that the human kidney is a major site for filtered nascent apolipoprotein A-I and A-IV but not for HDL particles.
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89
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Wool GD, Reardon CA, Getz GS. Apolipoprotein A-I mimetic peptide helix number and helix linker influence potentially anti-atherogenic properties. J Lipid Res 2008; 49:1268-83. [PMID: 18323574 DOI: 10.1194/jlr.m700552-jlr200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
We hypothesize that apolipoprotein A-I (apoA-I) mimetic peptides better mimicking the punctuated alpha-helical repeats of full-length apoA-I are more anti-inflammatory and anti-atherogenic. This study compares a monomeric apoA-I mimetic helix to three different tandem helix peptides in vitro: 4F (18 mer), 4F-proline-4F (37 mer, Pro), 4F-alanine-4F (37 mer, Ala), and 4F-KVEPLRA-4F [the human apoA-I 4/5 interhelical sequence (IHS), 43 mer]. All peptides cleared turbid lipid suspensions, with 4F being most effective. In contrast to lipid clearance, tandem peptides were more effective at remodeling mouse HDL. All four peptides displaced apoA-I and apoE from the HDL, leaving a larger particle containing apoA-II and peptide. Peptide-remodeled HDL particles show no deficit in ABCG1 cholesterol efflux despite the loss of the majority of apoA-I. Tandem peptides show greater ability to efflux cholesterol from lipid-loaded murine macrophages, compared with 4F. Although 4F inhibited oxidation of purified mouse LDL, the Ala tandem peptide increased oxidation. We compared several tandem 4F-based peptides with monomeric 4F in assays that correlated with suggested anti-inflammatory/anti-atherogenic pathways. Tandem 4F-based peptides, which better mimic full-length apoA-I, exceed monomeric 4F in HDL remodeling and cholesterol efflux but not LDL oxidation protection. In addition, apoA-I mimetic peptides may increase reverse cholesterol transport through both ABCA1 as well as ABCG1 pathways.
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Affiliation(s)
- Geoffrey D Wool
- The University of Chicago, Department of Pathology, Chicago, IL, USA
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90
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Sivashanmugam A, Yang Y, Murray V, McCullough C, Chen B, Ren X, Li Q, Wang J. Chapter 15 Structural Basis of Human High‐density Lipoprotein Formation and Assembly at Sub nanometer Resolution. Methods Cell Biol 2008; 90:327-64. [DOI: 10.1016/s0091-679x(08)00815-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
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91
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Nguyen TS, Weers PMM, Raussens V, Wang Z, Ren G, Sulchek T, Hoeprich PD, Ryan RO. Amphotericin B induces interdigitation of apolipoprotein stabilized nanodisk bilayers. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1778:303-12. [PMID: 17980702 DOI: 10.1016/j.bbamem.2007.10.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2007] [Revised: 09/19/2007] [Accepted: 10/03/2007] [Indexed: 10/22/2022]
Abstract
Amphotericin B nanodisks (AMB-ND) are ternary complexes of AMB, phospholipid and apolipoprotein organized as discrete nanometer scale disk-shaped bilayers. In gel filtration chromatography experiments, empty ND lacking AMB elute as a single population of particles with a molecular weight in the range of 200 kDa. AMB-ND formulated at a 4:1 phospholipid:AMB weight ratio separated into two peaks. One peak eluted at the position of control ND lacking AMB while the second peak, containing all of the AMB present in the original sample, eluted in the void volume. When ND prepared with increased AMB were subjected to gel filtration chromatography an increased proportion of phospholipid and apolipoprotein was recovered in the void volume with AMB. Native gradient gel electrophoresis corroborated the gel filtration chromatography data and electron microscopy studies revealed an AMB concentration-dependent heterogeneity in ND particle size. Stability studies revealed that introduction of AMB into ND decreases the ability of apoA-I to resist denaturation. Atomic force microscopy experiments showed that AMB induces compression of ND bilayer thickness while infrared spectroscopy analysis revealed that the presence of AMB does not induce extreme lipid disorder or alter the mean angle of the molecular axis along fatty acyl chains of ND phospholipids. Taken together the results are consistent with AMB-induced bilayer interdigitation, a phenomenon that likely contributes to AMB-dependent pore formation in susceptible membranes.
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Affiliation(s)
- Thanh-Son Nguyen
- Center for Prevention of Obesity, Diabetes and Cardiovascular Disease, Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr. Way, Oakland, CA 94609, USA
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92
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Wu Z, Wagner MA, Zheng L, Parks JS, Shy JM, Smith JD, Gogonea V, Hazen SL. The refined structure of nascent HDL reveals a key functional domain for particle maturation and dysfunction. Nat Struct Mol Biol 2007; 14:861-8. [PMID: 17676061 DOI: 10.1038/nsmb1284] [Citation(s) in RCA: 167] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2007] [Accepted: 07/02/2007] [Indexed: 11/09/2022]
Abstract
The cardioprotective function of high-density lipoprotein (HDL) is largely attributed to its ability to facilitate transport of cholesterol from peripheral tissues to the liver. However, HDL may become dysfunctional through oxidative modification, impairing cellular cholesterol efflux. Here we report a refined molecular model of nascent discoidal HDL, determined using hydrogen-deuterium exchange mass spectrometry. The model reveals two apolipoprotein A1 (apoA1) molecules arranged in an antiparallel double-belt structure, with residues 159-180 of each apoA1 forming a protruding solvent-exposed loop. We further show that this loop, including Tyr166, a preferred target for site-specific oxidative modification within atheroma, directly interacts with and activates lecithin cholesterol acyl transferase. These studies identify previously uncharacterized structural features of apoA1 in discoidal HDL that are crucial for particle maturation, and elucidate a structural and molecular mechanism for generating a dysfunctional form of HDL in atherosclerosis.
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Affiliation(s)
- Zhiping Wu
- Department of Cell Biology, Cleveland Clinic, 9500 Euclid Avenue, NE-10, Cleveland, Ohio 44195, USA
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93
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Lagerstedt JO, Cavigiolio G, Roberts LM, Hong HS, Jin LW, Fitzgerald P, Oda MN, Voss JC. Mapping the structural transition in an amyloidogenic apolipoprotein A-I. Biochemistry 2007; 46:9693-9. [PMID: 17665932 PMCID: PMC3650831 DOI: 10.1021/bi7005493] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The single amino acid mutation G26R in human apolipoprotein A-I (apoA-IIOWA) leads to the formation of beta-secondary structure rich amyloid fibrils in vivo. Here we show that full-length apoA-IIOWA has a decreased lipid-binding capability, an increased amino-terminal sensitivity to protease, and a propensity to form annular protofibrils visible by electron microscopy. The molecular basis for the conversion of apolipoprotein A-I to a proamyloidogenic form was examined by electron paramagnetic resonance spectroscopy. Our recent findings [Lagerstedt, J. O., Budamagunta, M. S., Oda, M. N., and Voss, J. C. (2007) J. Biol. Chem. 282, 9143-9149] indicate that Gly26 in the native apoprotein separates a preceding beta-strand structure (residues 20-25) from a downstream largely alpha-helical region. The current study demonstrates that the G26R variant promotes a structural transition of positions 27-56 to a mixture of coil and beta-strand secondary structure. Microscopy and staining by amyloidophilic dyes suggest that this alteration extends throughout the protein within 1 week of incubation in vitro, leading to insoluble aggregates of distinct morphology. The severe consequences of the Iowa mutation likely arise from the combination of losing the contribution of the native Gly residue in terminating beta-strand propagation and the promotion of beta-structure when an Arg is introduced adjacent to the succeeding residue of identical charge and size, Arg27.
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Affiliation(s)
- Jens O. Lagerstedt
- Department of Biochemistry and Molecular Medicine, University of California, Davis, CA 95616
- Department of Internal Medicine, University of California, Davis, CA 95616
| | - Giorgio Cavigiolio
- Department of Cell Biology and Human Anatomy, University of California, Davis, CA 95616
| | - Linda M. Roberts
- Department of Chemistry California State University, Sacramento, CA 95819
| | - Hyun-Seok Hong
- Department of Pathology, University of California, Davis, CA 95616
| | - Lee-Way Jin
- Department of Pathology, University of California, Davis, CA 95616
| | - Paul Fitzgerald
- Department of Cell Biology and Human Anatomy, University of California, Davis, CA 95616
| | - Michael N. Oda
- Children’s Hospital Oakland Research Institute, Oakland, CA 94609
| | - John C. Voss
- Department of Biochemistry and Molecular Medicine, University of California, Davis, CA 95616
- Corresponding author: Tel: +1 530 754 7583; Fax: +1 530 752 3516;
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94
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Bhat S, Sorci-Thomas MG, Tuladhar R, Samuel MP, Thomas MJ. Conformational adaptation of apolipoprotein A-I to discretely sized phospholipid complexes. Biochemistry 2007; 46:7811-21. [PMID: 17563120 PMCID: PMC2553278 DOI: 10.1021/bi700384t] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The conformational constraints for apoA-I bound to recombinant phospholipid complexes (rHDL) were attained from a combination of chemical cross-linking and mass spectrometry. Molecular distances were then used to refine models of lipid-bound apoA-I on both 80 and 96 A diameter rHDL particles. To obtain molecular constraints on the protein bound to phospholipid complexes, three different lysine-selective homo-bifunctional cross-linkers with increasing spacer arm lengths (i.e., 7.7, 12.0, and 16.1 A) were reacted with purified, homogeneous recombinant 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) apoA-I rHDL complexes of each diameter. Cross-linked dimeric apoA-I products were separated from monomeric apoprotein using 12% SDS-PAGE, then subjected to in-gel trypsin digest, and identified by MS/MS sequencing. These studies aid in the refinement of our previously published molecular model of two apoA-I molecules bound to approximately 150 molecules of POPC and suggest that the protein hydrophobic interactions at the N- and C-terminal domains decrease as the number of phospholipid molecules or "lipidation state" of apoA-I increases. Thus, it appears that these incremental changes in the interaction between the N- and C-terminal ends of apoA-I stabilize its tertiary conformation in the lipid-free state as well as allowing it to unfold and sequester discrete amounts of phospholipid molecules.
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Affiliation(s)
- Shaila Bhat
- Department of Pathology, Center for Lipid Science, Wake Forest University Medical Center, 391 Technology Way, Building A1, Winston-Salem, NC 27101
| | - Mary G Sorci-Thomas
- Department of Biochemistry, Wake Forest University Medical Center, 391 Technology Way, Building A1, Winston-Salem, NC 27101
- Department of Pathology, Center for Lipid Science, Wake Forest University Medical Center, 391 Technology Way, Building A1, Winston-Salem, NC 27101
| | - Rubina Tuladhar
- Department of Biochemistry, Wake Forest University Medical Center, 391 Technology Way, Building A1, Winston-Salem, NC 27101
| | - Michael P. Samuel
- Department of Biochemistry, Wake Forest University Medical Center, 391 Technology Way, Building A1, Winston-Salem, NC 27101
| | - Michael J. Thomas
- Department of Biochemistry, Wake Forest University Medical Center, 391 Technology Way, Building A1, Winston-Salem, NC 27101
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95
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Davidson WS, Thompson TB. The structure of apolipoprotein A-I in high density lipoproteins. J Biol Chem 2007; 282:22249-53. [PMID: 17526499 DOI: 10.1074/jbc.r700014200] [Citation(s) in RCA: 156] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- W Sean Davidson
- Department of Pathology and Laboratory Medicine, University of Cincinnati, OH 45237, USA.
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96
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Garda HA. Structure–function relationships in human apolipoprotein A-I: role of a central helix pair. ACTA ACUST UNITED AC 2007. [DOI: 10.2217/17460875.2.1.95] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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97
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Lagerstedt JO, Budamagunta MS, Oda MN, Voss JC. Electron paramagnetic resonance spectroscopy of site-directed spin labels reveals the structural heterogeneity in the N-terminal domain of apoA-I in solution. J Biol Chem 2007; 282:9143-9. [PMID: 17204472 DOI: 10.1074/jbc.m608717200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Apolipoprotein A-I (apoA-I) is the major protein constituent of high density lipoprotein (HDL) and plays a central role in phospholipid and cholesterol metabolism. This 243-residue long protein is remarkably flexible and assumes numerous lipid-dependent conformations. Consequently, definitive structural determination of lipid-free apoA-I in solution has been difficult. Using electron paramagnetic spectroscopy of site-directed spin labels in the N-terminal domain of apoA-I (residues 1-98) we have mapped a mixture of secondary structural elements, the composition of which is consistent with findings from other in-solution methods. Based on side chain mobility and their accessibility to polar and non-polar spin relaxers, the precise location of secondary elements for amino acids 14-98 was determined for both lipid-free and lipid-bound apoA-I. Based on intermolecular dipolar coupling at positions 26, 44, and 64, these secondary structural elements were arranged into a tertiary fold to generate a structural model for lipid-free apoA-I in solution.
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Affiliation(s)
- Jens O Lagerstedt
- Department of Biochemistry, University of California, Davis, California 95616, USA
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