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Zhang D, Gao B, Feng Q, Manichaikul A, Peloso GM, Tracy RP, Durda P, Taylor KD, Liu Y, Johnson WC, Gabriel S, Gupta N, Smith JD, Aguet F, Ardlie KG, Blackwell TW, Gerszten RE, Rich SS, Rotter JI, Scott LJ, Zhou X, Lee S. Proteome-Wide Association Studies for Blood Lipids and Comparison with Transcriptome-Wide Association Studies. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.17.553749. [PMID: 37662416 PMCID: PMC10473643 DOI: 10.1101/2023.08.17.553749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
Blood lipid traits are treatable and heritable risk factors for heart disease, a leading cause of mortality worldwide. Although genome-wide association studies (GWAS) have discovered hundreds of variants associated with lipids in humans, most of the causal mechanisms of lipids remain unknown. To better understand the biological processes underlying lipid metabolism, we investigated the associations of plasma protein levels with total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL), and low-density lipoprotein cholesterol (LDL) in blood. We trained protein prediction models based on samples in the Multi-Ethnic Study of Atherosclerosis (MESA) and applied them to conduct proteome-wide association studies (PWAS) for lipids using the Global Lipids Genetics Consortium (GLGC) data. Of the 749 proteins tested, 42 were significantly associated with at least one lipid trait. Furthermore, we performed transcriptome-wide association studies (TWAS) for lipids using 9,714 gene expression prediction models trained on samples from peripheral blood mononuclear cells (PBMCs) in MESA and 49 tissues in the Genotype-Tissue Expression (GTEx) project. We found that although PWAS and TWAS can show different directions of associations in an individual gene, 40 out of 49 tissues showed a positive correlation between PWAS and TWAS signed p-values across all the genes, which suggests a high-level consistency between proteome-lipid associations and transcriptome-lipid associations.
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Affiliation(s)
- Daiwei Zhang
- Department of Biostatistics, Epidemiology and Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA USA
- Department of Biostatistics and Center for Statistical Genetics, University of Michigan, Ann Arbor, MI USA
| | - Boran Gao
- Department of Biostatistics and Center for Statistical Genetics, University of Michigan, Ann Arbor, MI USA
| | - Qidi Feng
- Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, MA USA
- Department of Biostatistics and Center for Statistical Genetics, University of Michigan, Ann Arbor, MI USA
| | - Ani Manichaikul
- Center for Public Health Genomics, University of Virginia, Charlottesville, VA USA
| | - Gina M Peloso
- Department of Biostatistics, Boston University School of Public Health, Boston, MA USA
| | - Russell P Tracy
- Departments of Pathology & Laboratory Medicine, and Biochemistry, Larner College of Medicine, University of Vermont, Burlington, VT USA
| | - Peter Durda
- Departments of Pathology & Laboratory Medicine, Larner College of Medicine, The University of Vermont, Burlington, VT USA
| | - Kent D Taylor
- The Institute for Translational Genomics and Population Sciences, Department of Pediatrics, The Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, CA USA
| | - Yongmei Liu
- Department of Medicine, Divisions of Cardiology and Neurology, Duke University Medical Center, Durham, NC USA
| | - W Craig Johnson
- Department of Biostatistics, University of Washington, Seattle, WA USA
| | - Stacey Gabriel
- Genomics Platform, Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, MA USA
| | - Namrata Gupta
- Genomics Platform, Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, MA USA
| | - Joshua D Smith
- Department of Genome Sciences, Human Genetics and Translational Genomics, The University of Washington, Seattle, WA, USA
| | - Francois Aguet
- Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, MA USA
| | - Kristin G Ardlie
- Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, MA USA
| | - Thomas W Blackwell
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO USA
| | - Robert E Gerszten
- Genomics Platform, Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, MA USA
| | - Stephen S Rich
- Center for Public Health Genomics, University of Virginia, Charlottesville, VA USA
| | - Jerome I Rotter
- The Institute for Translational Genomics and Population Sciences, Department of Pediatrics, The Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, CA USA
| | - Laura J Scott
- Department of Biostatistics and Center for Statistical Genetics, University of Michigan, Ann Arbor, MI USA
| | - Xiang Zhou
- Department of Biostatistics and Center for Statistical Genetics, University of Michigan, Ann Arbor, MI USA
| | - Seunggeun Lee
- Graduate School of Data Science, Seoul National University, Seoul, Republic of Korea
- Department of Biostatistics and Center for Statistical Genetics, University of Michigan, Ann Arbor, MI USA
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2
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Rueter J, Rimbach G, Huebbe P. Functional diversity of apolipoprotein E: from subcellular localization to mitochondrial function. Cell Mol Life Sci 2022; 79:499. [PMID: 36018414 PMCID: PMC9418098 DOI: 10.1007/s00018-022-04516-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 07/27/2022] [Accepted: 08/07/2022] [Indexed: 11/26/2022]
Abstract
Human apolipoprotein E (APOE), originally known for its role in lipid metabolism, is polymorphic with three major allele forms, namely, APOEε2, APOEε3, and APOEε4, leading to three different human APOE isoforms. The ε4 allele is a genetic risk factor for Alzheimer's disease (AD); therefore, the vast majority of APOE research focuses on its role in AD pathology. However, there is increasing evidence for other functions of APOE through the involvement in other biological processes such as transcriptional regulation, mitochondrial metabolism, immune response, and responsiveness to dietary factors. Therefore, the aim of this review is to provide an overview of the potential novel functions of APOE and their characterization. The detection of APOE in various cell organelles points to previously unrecognized roles in mitochondria and others, although it is actually considered a secretory protein. Furthermore, numerous interactions of APOE with other proteins have been detected, providing indications for new metabolic pathways involving APOE. The present review summarizes the current evidence on APOE beyond its original role in lipid metabolism, to change the perspective and encourage novel approaches to future research on APOE and its isoform-dependent role in the cellular metabolism.
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Affiliation(s)
- Johanna Rueter
- Devision of Food Science, Institute of Human Nutrition and Food Science, University of Kiel, Hermann-Rodewald-Strasse 6, 24118, Kiel, Germany
| | - Gerald Rimbach
- Devision of Food Science, Institute of Human Nutrition and Food Science, University of Kiel, Hermann-Rodewald-Strasse 6, 24118, Kiel, Germany.
| | - Patricia Huebbe
- Devision of Food Science, Institute of Human Nutrition and Food Science, University of Kiel, Hermann-Rodewald-Strasse 6, 24118, Kiel, Germany
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3
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Gharibyan AL, Wasana Jayaweera S, Lehmann M, Anan I, Olofsson A. Endogenous Human Proteins Interfering with Amyloid Formation. Biomolecules 2022; 12:biom12030446. [PMID: 35327638 PMCID: PMC8946693 DOI: 10.3390/biom12030446] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 03/08/2022] [Accepted: 03/11/2022] [Indexed: 01/09/2023] Open
Abstract
Amyloid formation is a pathological process associated with a wide range of degenerative disorders, including Alzheimer’s disease, Parkinson’s disease, and diabetes mellitus type 2. During disease progression, abnormal accumulation and deposition of proteinaceous material are accompanied by tissue degradation, inflammation, and dysfunction. Agents that can interfere with the process of amyloid formation or target already formed amyloid assemblies are consequently of therapeutic interest. In this context, a few endogenous proteins have been associated with an anti-amyloidogenic activity. Here, we review the properties of transthyretin, apolipoprotein E, clusterin, and BRICHOS protein domain which all effectively interfere with amyloid in vitro, as well as displaying a clinical impact in humans or animal models. Their involvement in the amyloid formation process is discussed, which may aid and inspire new strategies for therapeutic interventions.
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Affiliation(s)
- Anna L. Gharibyan
- Department of Clinical Microbiology, Umeå University, 901 87 Umeå, Sweden;
- Correspondence: (A.L.G.); (A.O.)
| | | | - Manuela Lehmann
- Department of Public Health and Clinical Medicine, Umeå University, 901 87 Umeå, Sweden; (M.L.); (I.A.)
| | - Intissar Anan
- Department of Public Health and Clinical Medicine, Umeå University, 901 87 Umeå, Sweden; (M.L.); (I.A.)
| | - Anders Olofsson
- Department of Clinical Microbiology, Umeå University, 901 87 Umeå, Sweden;
- Correspondence: (A.L.G.); (A.O.)
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4
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Wang Y, Xue Y, Wang S, Huang J, Yang X. Real-Time Analysis of Specific Binding between Apolipoprotein E Isoforms and Amyloid β-Peptide by Dual Polarization Interferometry. Anal Chem 2021; 93:1472-1479. [PMID: 33342209 DOI: 10.1021/acs.analchem.0c03542] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
One of the pathogenesis hypotheses of Alzheimer's disease (AD) is amyloid depositions and neurofibrillary tangles. Apolipoprotein E (Apo E) acts a vital part in the development of AD by affecting the aggregation and clearance of amyloid-β (Aβ). In this paper, a dual polarization interferometry (DPI) technique was employed for a real-time investigation toward the binding events of Apo E isoforms, for instance, Apo E2, Apo E3, and Apo E4, with Aβ1-40. By evaluation of detailed binding information provided by DPI, the affinities between Apo E isoforms and Aβ1-40 follow the order of E4 > E3 > E2, and the dissociation constants (KD) of Aβ1-40 with Apo E2, Apo E3, and Apo E4 were determined to be 251 ± 37, 40 ± 0.65, and 24.6 ± 2.42 nM, respectively. Our findings reveal the isoform-specific binding behaviors from a kinetics perspective, which can help us understand that Apo E4 has a higher risk of causing AD because of its promoting effect on Aβ aggregation and fibrillation and inefficient clearance of Aβ. Remarkably, this work provides a promising method for exploring the dynamics of interactions between biomolecules and expectantly contributes to the development of AD drugs and therapies targeting Apo E and Aβ.
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Affiliation(s)
- Yu Wang
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Changchun, Jilin 130022, China.,University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Yu Xue
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Changchun, Jilin 130022, China.,University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Shuang Wang
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Changchun, Jilin 130022, China.,University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Jianshe Huang
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Changchun, Jilin 130022, China
| | - Xiurong Yang
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Changchun, Jilin 130022, China.,University of Science and Technology of China, Hefei, Anhui 230026, China
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5
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Gharibyan AL, Islam T, Pettersson N, Golchin SA, Lundgren J, Johansson G, Genot M, Schultz N, Wennström M, Olofsson A. Apolipoprotein E Interferes with IAPP Aggregation and Protects Pericytes from IAPP-Induced Toxicity. Biomolecules 2020; 10:biom10010134. [PMID: 31947546 PMCID: PMC7022431 DOI: 10.3390/biom10010134] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 01/10/2020] [Accepted: 01/12/2020] [Indexed: 02/06/2023] Open
Abstract
Apolipoprotein E (ApoE) has become a primary focus of research after the discovery of its strong linkage to Alzheimer’s disease (AD), where the ApoE4 variant is the highest genetic risk factor for this disease. ApoE is commonly found in amyloid deposits of different origins, and its interaction with amyloid-β peptide (Aβ), the hallmark of AD, is well known. However, studies on the interaction of ApoEs with other amyloid-forming proteins are limited. Islet amyloid polypeptide (IAPP) is an amyloid-forming peptide linked to the development of type-2 diabetes and has also been shown to be involved in AD pathology and vascular dementia. Here we studied the impact of ApoE on IAPP aggregation and IAPP-induced toxicity on blood vessel pericytes. Using both in vitro and cell-based assays, we show that ApoE efficiently inhibits the amyloid formation of IAPP at highly substoichiometric ratios and that it interferes with both nucleation and elongation. We also show that ApoE protects the pericytes against IAPP-induced toxicity, however, the ApoE4 variant displays the weakest protective potential. Taken together, our results suggest that ApoE has a generic amyloid-interfering property and can be protective against amyloid-induced cytotoxicity, but there is a loss of function for the ApoE4 variant.
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Affiliation(s)
- Anna L. Gharibyan
- Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden; (T.I.); (N.P.); (S.A.G.); (J.L.); (G.J.); (M.G.)
- Correspondence: (A.L.G.); (A.O.); Tel.: +46-73-912-54-94 (A.L.G.); +46-70-354-33-01 (A.O.)
| | - Tohidul Islam
- Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden; (T.I.); (N.P.); (S.A.G.); (J.L.); (G.J.); (M.G.)
| | - Nina Pettersson
- Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden; (T.I.); (N.P.); (S.A.G.); (J.L.); (G.J.); (M.G.)
| | - Solmaz A. Golchin
- Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden; (T.I.); (N.P.); (S.A.G.); (J.L.); (G.J.); (M.G.)
| | - Johanna Lundgren
- Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden; (T.I.); (N.P.); (S.A.G.); (J.L.); (G.J.); (M.G.)
| | - Gabriella Johansson
- Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden; (T.I.); (N.P.); (S.A.G.); (J.L.); (G.J.); (M.G.)
| | - Mélany Genot
- Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden; (T.I.); (N.P.); (S.A.G.); (J.L.); (G.J.); (M.G.)
| | - Nina Schultz
- Clinical Memory Research Unit, Department of Clinical Sciences Malmö, Lund University, 21428 Malmö, Sweden; (N.S.); (M.W.)
| | - Malin Wennström
- Clinical Memory Research Unit, Department of Clinical Sciences Malmö, Lund University, 21428 Malmö, Sweden; (N.S.); (M.W.)
| | - Anders Olofsson
- Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden; (T.I.); (N.P.); (S.A.G.); (J.L.); (G.J.); (M.G.)
- Correspondence: (A.L.G.); (A.O.); Tel.: +46-73-912-54-94 (A.L.G.); +46-70-354-33-01 (A.O.)
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6
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Raulin AC, Kraft L, Al-Hilaly YK, Xue WF, McGeehan JE, Atack JR, Serpell L. The Molecular Basis for Apolipoprotein E4 as the Major Risk Factor for Late-Onset Alzheimer's Disease. J Mol Biol 2019; 431:2248-2265. [PMID: 31051176 PMCID: PMC6556554 DOI: 10.1016/j.jmb.2019.04.019] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 04/16/2019] [Accepted: 04/16/2019] [Indexed: 11/28/2022]
Abstract
Apolipoprotein E4 (ApoE4) is one of three (E2, E3 and E4) human isoforms of an α-helical, 299-amino-acid protein. Homozygosity for the ε4 allele is the major genetic risk factor for developing late-onset Alzheimer's disease (AD). ApoE2, ApoE3 and ApoE4 differ at amino acid positions 112 and 158, and these sequence variations may confer conformational differences that underlie their participation in the risk of developing AD. Here, we compared the shape, oligomerization state, conformation and stability of ApoE isoforms using a range of complementary biophysical methods including small-angle x-ray scattering, analytical ultracentrifugation, circular dichroism, x-ray fiber diffraction and transmission electron microscopy We provide an in-depth and definitive study demonstrating that all three proteins are similar in stability and conformation. However, we show that ApoE4 has a propensity to polymerize to form wavy filaments, which do not share the characteristics of cross-β amyloid fibrils. Moreover, we provide evidence for the inhibition of ApoE4 fibril formation by ApoE3. This study shows that recombinant ApoE isoforms show no significant differences at the structural or conformational level. However, self-assembly of the ApoE4 isoform may play a role in pathogenesis, and these results open opportunities for uncovering new triggers for AD onset.
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Affiliation(s)
- Ana-Caroline Raulin
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Falmer, Brighton, East Sussex BN1 6NN, UK
| | - Lucas Kraft
- Sussex Drug Discovery Centre, School of Life Sciences, University of Sussex, Falmer, Brighton, East Sussex , BN1 6NN, UK
| | - Youssra K Al-Hilaly
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Falmer, Brighton, East Sussex BN1 6NN, UK; Chemistry Department, College of Science, Mustansiriyah University, Baghdad, Iraq
| | - Wei-Feng Xue
- School of Biosciences, University of Kent, Canterbury, England CT2 7NJ, UK
| | - John E McGeehan
- School of Biological Sciences, Institute of Biological and Biomedical Sciences, Faculty of Science, University of Portsmouth, Portsmouth, Hampshire PO1 2DY, UK
| | - John R Atack
- Sussex Drug Discovery Centre, School of Life Sciences, University of Sussex, Falmer, Brighton, East Sussex , BN1 6NN, UK
| | - Louise Serpell
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Falmer, Brighton, East Sussex BN1 6NN, UK.
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7
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Katsarou M, Stratikos E, Chroni A. Thermodynamic destabilization and aggregation propensity as the mechanism behind the association of apoE3 mutants and lipoprotein glomerulopathy. J Lipid Res 2018; 59:2339-2348. [PMID: 30309894 PMCID: PMC6277168 DOI: 10.1194/jlr.m088732] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Revised: 10/11/2018] [Indexed: 12/26/2022] Open
Abstract
Lipoprotein glomerulopathy (LPG) is a rare renal disease, characterized by lipoprotein thrombi in glomerular capillaries. A series of apoE mutations have been associated with LPG development. We previously showed that three mutants based on apoE3 sequence, in which an arginine was substituted by proline, are thermodynamically destabilized and aggregation-prone. To examine whether other LPG-associated apoE3 mutations induce similar effects, we characterized three nonproline LPG-associated apoE3 mutations, namely, R25C (apoEKyoto), R114C (apoETsukuba), and A152D (apoELasVegas). All three apoE3 variants are found to have significantly reduced helical content and to be thermodynamically destabilized, both in lipid-free and lipoprotein-associated form, and to expose a larger portion of hydrophobic surface to the solvent compared with WT apoE3. Furthermore, all three apoE3 variants are aggregation-prone, as shown by dynamic light-scattering measurements and by their enhanced capacity to bind the amyloid probe thioflavin T. Overall, our data suggest that the LPG-associated apoE3 mutations R25C, R114C, and A152D induce protein misfolding, which may contribute to protein aggregation in glomerular capillaries. The similar effects of both LPG-associated proline and nonproline mutations on apoE3 structure suggest that the thermodynamic destabilization and enhanced aggregation of apoE3 may constitute a common underlying mechanism behind the pathogenesis of LPG.
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Affiliation(s)
- Maria Katsarou
- Institute of Biosciences and Applications, National Centre for Scientific Research "Demokritos," Agia Paraskevi, Athens 15341, Greece
| | - Efstratios Stratikos
- Protein Chemistry Laboratory, Institute of Nuclear & Radiological Sciences and Technology, Energy & Safety (INRaSTES), National Centre for Scientific Research "Demokritos," Agia Paraskevi, Athens 15341, Greece
| | - Angeliki Chroni
- Institute of Biosciences and Applications, National Centre for Scientific Research "Demokritos," Agia Paraskevi, Athens 15341, Greece
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8
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Dafnis I, Argyri L, Chroni A. Amyloid-peptide β 42 Enhances the Oligomerization and Neurotoxicity of apoE4: The C-terminal Residues Leu279, Lys282 and Gln284 Modulate the Structural and Functional Properties of apoE4. Neuroscience 2018; 394:144-155. [PMID: 30367942 DOI: 10.1016/j.neuroscience.2018.10.026] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 10/12/2018] [Accepted: 10/15/2018] [Indexed: 11/25/2022]
Abstract
Apolipoprotein E4 (apoE4), one of the three apoE isoforms, is the strongest factor for raising the risk for late-onset Alzheimer's disease (AD) and has been proposed to play a major role in AD pathogenesis. Amyloid-peptide β 42 (Aβ42) has also been proposed to affect neuronal degeneration and AD pathogenesis, possibly by interacting with apoE. Previous studies have shown that the functions of apoE forms can be dictated by their structural and biophysical properties. Here we show that apoE4 can form SDS-stable oligomers, possibly reflecting aggregated forms, which increase following incubation of apoE4 with Aβ42. In addition, extracellular apoE4 is cytotoxic for human neuroblastoma SK-N-SH cells, while Aβ42 enhances the cytotoxicity of apoE4. Carboxyl-terminal point mutations L279Q, K282A or Q284A reduced the capacity of apoE4 to form SDS-stable oligomers, as well as its cytotoxicity, both in the absence and presence of Aβ42. Structural and thermodynamic analyses showed that all three apoE4 mutants have significantly increased α-helical and decreased β-sheet content, have reduced portion of hydrophobic surfaces exposed to the solvent and have a reduced conformational stability during chemical denaturation. Overall, our data highlight a pathogenic role of apoE4 that could be linked to the capacity of the protein to form oligomeric species especially in the presence of Aβ42 and to induce cytotoxicity. Carboxyl-terminal residues L279, K282 or Q284 appear to be involved in the conformation of apoE4 that may underlie the protein's functional properties related to neurotoxicity.
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Affiliation(s)
- Ioannis Dafnis
- Institute of Biosciences and Applications, National Center for Scientific Research "Demokritos", Agia Paraskevi, Athens 15341, Greece
| | - Letta Argyri
- Institute of Biosciences and Applications, National Center for Scientific Research "Demokritos", Agia Paraskevi, Athens 15341, Greece
| | - Angeliki Chroni
- Institute of Biosciences and Applications, National Center for Scientific Research "Demokritos", Agia Paraskevi, Athens 15341, Greece.
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9
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Huebbe P, Rimbach G. Evolution of human apolipoprotein E (APOE) isoforms: Gene structure, protein function and interaction with dietary factors. Ageing Res Rev 2017. [PMID: 28647612 DOI: 10.1016/j.arr.2017.06.002] [Citation(s) in RCA: 94] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Apolipoprotein E (APOE) is a member of the vertebrate protein family of exchangeable apolipoproteins that is characterized by amphipathic α-helices encoded by multiple nucleotide tandem repeats. Its equivalent in flying insects - apolipophorin-III - shares structural and functional commonalities with APOE, suggesting the possibility of an evolutionary relationship between the proteins. In contrast to all other known species, human APOE is functionally polymorphic and possesses three major allelic variants (ε4, ε3 and ε2). The present review examines the current knowledge on APOE gene structure, phylogeny and APOE protein topology as well as its human isoforms. The ε4 allele is associated with an increased age-related disease risk but is also the ancestral form. Despite increased mortality in the elderly, ε4 has not become extinct and is the second-most common allele worldwide after ε3. APOE ε4, moreover, shows a non-random geographical distribution, and similarly, the ε2 allele is not homogenously distributed among ethnic populations. This likely suggests the existence of selective forces that are driving the evolution of human APOE isoforms, which may include differential interactions with dietary factors. To that effect, micronutrients such as vitamin D and carotenoids or dietary macronutrient composition are elucidated with respect to APOE evolution.
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Affiliation(s)
- Patricia Huebbe
- Institute of Human Nutrition and Food Science, University of Kiel, H. Rodewald Str. 6, 24118 Kiel, Germany.
| | - Gerald Rimbach
- Institute of Human Nutrition and Food Science, University of Kiel, H. Rodewald Str. 6, 24118 Kiel, Germany.
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10
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Chu Q, Diedrich JK, Vaughan JM, Donaldson CJ, Nunn MF, Lee KF, Saghatelian A. HtrA1 Proteolysis of ApoE In Vitro Is Allele Selective. J Am Chem Soc 2016; 138:9473-8. [PMID: 27379525 PMCID: PMC5063305 DOI: 10.1021/jacs.6b03463] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Apolipoprotein E (ApoE) belongs to a large class of proteins that solubilize lipids for physiological transport. Humans have three different APOE alleles, APOE ε2, APOE ε3, and APOE ε4, and genetic studies identified ApoE4 as the strongest genetic risk factor for Alzheimer's disease (AD). People who are homozygous for ApoE4 (i.e., ApoE4/E4) are an order of magnitude more likely to develop late-onset AD (LOAD) than ApoE3/E3 carriers. Several differences between ApoE3 and ApoE4 may contribute to AD including the observation that ApoE4 is degraded to a greater extent than ApoE3 in the human brain. Experiments with high-temperature requirement serine peptidase A1 (HtrA1), which is found in the nervous system, demonstrate that HtrA1 is an allele-selective ApoE-degrading enzyme that degrades ApoE4 more quickly than ApoE3. This activity is specific to HtrA1, as similar assays with HtrA2 showed minimal ApoE4 proteolysis and trypsin had no preference between ApoE4 and ApoE3. HtrA1 has also been reported to cleave the tau protein (Tau) and the amyloid protein precursor (APP) to hinder the formation of toxic amyloid deposits associated with AD. Competition assays with ApoE4, ApoE3, and Tau revealed that ApoE4 inhibits Tau degradation. Thus, the identification of ApoE4 as an in vitro HtrA1 substrate suggests a potential biochemical mechanism that links ApoE4 regulation of AD proteins such as Tau.
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Affiliation(s)
- Qian Chu
- The Salk Institute for Biological Studies, Clayton Foundation Laboratories for Peptide Biology, 10010 N. Torrey Pines Rd, La Jolla, CA 92037, USA
| | - Jolene K. Diedrich
- The Salk Institute for Biological Studies, Clayton Foundation Laboratories for Peptide Biology, 10010 N. Torrey Pines Rd, La Jolla, CA 92037, USA
- Department of Chemical Physiology, The Scripps Research Institute, 10550 N. Torrey Pines Rd, La Jolla, CA 92037, USA
| | - Joan M. Vaughan
- The Salk Institute for Biological Studies, Clayton Foundation Laboratories for Peptide Biology, 10010 N. Torrey Pines Rd, La Jolla, CA 92037, USA
| | - Cynthia J. Donaldson
- The Salk Institute for Biological Studies, Clayton Foundation Laboratories for Peptide Biology, 10010 N. Torrey Pines Rd, La Jolla, CA 92037, USA
| | - Michael F. Nunn
- The Salk Institute for Biological Studies, Clayton Foundation Laboratories for Peptide Biology, 10010 N. Torrey Pines Rd, La Jolla, CA 92037, USA
| | - Kuo-Fen Lee
- The Salk Institute for Biological Studies, Clayton Foundation Laboratories for Peptide Biology, 10010 N. Torrey Pines Rd, La Jolla, CA 92037, USA
| | - Alan Saghatelian
- The Salk Institute for Biological Studies, Clayton Foundation Laboratories for Peptide Biology, 10010 N. Torrey Pines Rd, La Jolla, CA 92037, USA
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11
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Argyri L, Dafnis I, Theodossiou TA, Gantz D, Stratikos E, Chroni A. Molecular basis for increased risk for late-onset Alzheimer disease due to the naturally occurring L28P mutation in apolipoprotein E4. J Biol Chem 2014; 289:12931-45. [PMID: 24644280 DOI: 10.1074/jbc.m113.538124] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The apolipoprotein (apo) E4 isoform has consistently emerged as a susceptibility factor for late-onset Alzheimer disease (AD), although the exact mechanism is not clear. A rare apoE4 mutant, apoE4[L28P] Pittsburgh, burdens carriers with an added risk for late-onset AD and may be a useful tool for gaining insights into the role of apoE4 in disease pathogenesis. Toward this end, we evaluated the effect of the L28P mutation on the structural and functional properties of apoE4. ApoE4[L28P] was found to have significantly perturbed thermodynamic properties, to have reduced helical content, and to expose a larger portion of the hydrophobic surface to the solvent. Furthermore, this mutant is thermodynamically destabilized and more prone to proteolysis. When interacting with lipids, apoE4[L28P] formed populations of lipoprotein particles with structural defects. The structural perturbations brought about by the mutation were accompanied by aberrant functions associated with the pathogenesis of AD. Specifically, apoE4[L28P] promoted the cellular uptake of extracellular amyloid β peptide 42 (Aβ42) by human neuroblastoma SK-N-SH cells as well as by primary mouse neuronal cells and led to increased formation of intracellular reactive oxygen species that persisted for at least 24 h. Furthermore, lipoprotein particles containing apoE4[L28P] induced intracellular reactive oxygen species formation and reduced SK-N-SH cell viability. Overall, our findings suggest that the L28P mutation leads to significant structural and conformational perturbations in apoE4 and can induce functional defects associated with neuronal Aβ42 accumulation and oxidative stress. We propose that these structural and functional changes underlie the observed added risk for AD development in carriers of apoE4[L28P].
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Affiliation(s)
- Letta Argyri
- From the Institute of Biosciences and Applications
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12
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Georgiadou D, Stamatakis K, Efthimiadou EK, Kordas G, Gantz D, Chroni A, Stratikos E. Thermodynamic and structural destabilization of apoE3 by hereditary mutations associated with the development of lipoprotein glomerulopathy. J Lipid Res 2012; 54:164-76. [PMID: 23110818 DOI: 10.1194/jlr.m030965] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lipoprotein glomerulopathy (LPG) is a dominant inherited kidney disorder characterized by lipoprotein thrombi in glomerular capillaries. Single-amino-acid mutations in apoE have been associated with the development of the disease, although the mechanism is unknown. In an effort to gain mechanistic insight linking the presence of such mutations and the development of LPG, we evaluated the effects of three of the most common apoE3 variants associated with this disease, namely R145P(Sendai), R147P(Chicago), and R158P(Osaka or Kurashiki), on the structural and conformational integrity of the protein. All three variants were found to have significantly reduced helical content, to expose a larger portion of hydrophobic surface to the solvent, and to be significantly thermodynamically destabilized, often lacking functionally relevant unfolding intermediates. Furthermore, all variants were aggregation prone and had enhanced sensitivity to protease digestion. Finally, although the variants were able to form discoidal lipoprotein particles, discrete subpopulations of poorly formed or aberrant particles were evident. Furthermore, these lipoprotein particles were thermodynamically destabilized and aggregation prone. Overall, our data suggest that these mutations induce a generalized unfolding of the N-terminal domain of apoE3 toward a molten-globule-like structure. ApoE3 N-terminal domain unfolding due to mutation may constitute a common mechanism underlying the protein's association with the pathogenesis of LPG.
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Affiliation(s)
- Dimitra Georgiadou
- National Centre for Scientific Research Demokritos, Agia Paraskevi, Athens 15310, Greece
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13
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Georgiadou D, Chroni A, Vezeridis A, Zannis VI, Stratikos E. Biophysical analysis of apolipoprotein E3 variants linked with development of type III hyperlipoproteinemia. PLoS One 2011; 6:e27037. [PMID: 22069485 PMCID: PMC3206067 DOI: 10.1371/journal.pone.0027037] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Accepted: 10/10/2011] [Indexed: 01/20/2023] Open
Abstract
Background Apolipoprotein E (apoE) is a major protein of the lipoprotein transport system that plays important roles in lipid homeostasis and protection from atherosclerosis. ApoE is characterized by structural plasticity and thermodynamic instability and can undergo significant structural rearrangements as part of its biological function. Mutations in the 136–150 region of the N-terminal domain of apoE, reduce its low density lipoprotein (LDL) receptor binding capacity and have been linked with lipoprotein disorders, such as type III hyperlipoproteinemia (HLP) in humans. However, the LDL-receptor binding defects for these apoE variants do not correlate well with the severity of dyslipidemia, indicating that these variants may carry additional properties that contribute to their pathogenic potential. Methodology/Principal Findings In this study we examined whether three type III HLP predisposing apoE3 variants, namely R136S, R145C and K146E affect the biophysical properties of the protein. Circular dichroism (CD) spectroscopy revealed that these mutations do not significantly alter the secondary structure of the protein. Thermal and chemical unfolding analysis revealed small thermodynamic alterations in each variant compared to wild-type apoE3, as well as effects in the reversibility of the unfolding transition. All variants were able to remodel multillamelar 1,2-Dimyristoyl-sn-glycero-3-phosphocholine (DMPC) vesicles, but R136S and R145C had reduced kinetics. Dynamic light scattering analysis indicated that the variant R136S exists in a higher-order oligomerization state in solution. Finally, 1-anilinonaphthalene-8-sulfonic acid (ANS) binding suggested that the variant R145C exposes a larger amount of hydrophobic surface to the solvent. Conclusions/Significance Overall, our findings suggest that single amino acid changes in the functionally important region 136–150 of apoE3 can affect the molecule's stability and conformation in solution and may underlie functional consequences. However, the magnitude and the non-concerted nature of these changes, make it unlikely that they constitute a distinct unifying mechanism leading to type III HLP pathogenesis.
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Affiliation(s)
- Dimitra Georgiadou
- Protein Chemistry Laboratory, National Centre for Scientific Research Demokritos, Agia Paraskevi, Athens, Greece
| | - Angeliki Chroni
- Institute of Biology, National Centre for Scientific Research Demokritos, Agia Paraskevi, Athens, Greece
| | - Alexander Vezeridis
- Molecular Genetics, Departments of Medicine and Biochemistry, Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, Massachusetts, United States of America
| | - Vassilis I. Zannis
- Molecular Genetics, Departments of Medicine and Biochemistry, Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, Massachusetts, United States of America
| | - Efstratios Stratikos
- Protein Chemistry Laboratory, National Centre for Scientific Research Demokritos, Agia Paraskevi, Athens, Greece
- * E-mail:
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14
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Garai K, Baban B, Frieden C. Self-association and stability of the ApoE isoforms at low pH: implications for ApoE-lipid interactions. Biochemistry 2011; 50:6356-64. [PMID: 21699199 DOI: 10.1021/bi2006702] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Apolipoprotein E (apoE) isoforms are known to differentially accumulate in the lysosomes of neuronal cells, and the deleterious effects of the apoE4 isoform in Alzheimer's disease may relate to its properties at the low lysosomal pH. However, the effect of pH on the molecular properties of full-length apoE is unclear. Here we examine the pH dependence of the monomer-dimer-tetramer reaction, of lipid binding, and of the stability of the three major apoE isoforms. Using FRET measurements, we find that the association-dissociation behavior of apoE proteins changes dramatically with changes in pH. At pH 4.5, approximating the pH of the lysosome, rate constants for association and dissociation are 2-10 times faster than those at pH 7.4. Aggregation beyond the tetrameric form is also more evident at lower pH values. Stability, as measured by urea denaturation at pH 4.5, is found to be considerably greater than that at neutral pH and to be isoform dependent. Lipid binding, as measured by turbidity clearance of unilamellar vesicles of DMPC, is faster at acidic pH values and consistent with our previous hypothesis that it is only the monomeric form of apoE that binds lipid tightly. Since apoE is more stable at pH 4.5 than at neutral pH, the more rapid apoE-lipid interactions at low pH are not correlated with the stability of the apoE isoforms, but rather to the faster association-dissociation behavior. Our results indicate that pathological behavior of apoE4 may arise from altered molecular properties of this protein at the acidic pH of the lysosome.
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Affiliation(s)
- Kanchan Garai
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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15
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Argyri L, Skamnaki V, Stratikos E, Chroni A. A simple approach for human recombinant apolipoprotein E4 expression and purification. Protein Expr Purif 2011; 79:251-7. [PMID: 21712092 DOI: 10.1016/j.pep.2011.06.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2011] [Revised: 06/07/2011] [Accepted: 06/13/2011] [Indexed: 10/18/2022]
Abstract
We report a simple expression and purification procedure for the production of recombinant apolipoprotein E4 (apoE4), an important protein for the lipid homeostasis in humans that plays critical roles in the pathogenesis of cardiovascular and neurodegenerative diseases. Our approach is based on the expression of a thioredoxin-apoE4 fusion construct in bacterial cells and subsequent removal of the fused thioredoxin using the highly specific 3C protease, avoiding costly and laborious lipidation-delipidation steps used before. Our approach results in rapid, high-yield production of structurally and functionally competent apoE4 as evidenced by secondary structure measurements, thermal and chemical melting profiles and the kinetic profile of solubilization of dimyristoyl-phosphatidylcholine (DMPC) vesicles. This protocol is appropriate for laboratories with little experience in apolipoprotein biochemistry and will facilitate future studies on the role of apoE4 in the pathogenesis of cardiovascular disease and neurodegenerative diseases, including Alzheimer's disease.
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Affiliation(s)
- Letta Argyri
- Institute of Biology, National Center for Scientific Research Demokritos, Agia Paraskevi, Athens 15310, Greece
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16
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Dergunov AD. Local/bulk determinants of conformational stability of exchangeable apolipoproteins. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1814:1169-77. [PMID: 21600318 DOI: 10.1016/j.bbapap.2011.05.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2011] [Revised: 04/12/2011] [Accepted: 05/03/2011] [Indexed: 11/27/2022]
Abstract
GuHCl-induced denaturation of human plasma apoA-I, apoA-II, apoA-IV, apoE3 and three recombinant apoE isoforms in solution and discoidal complexes with phosphatidylcholine (only plasma proteins) was studied. The protein conformational stability (ΔG(H(2)O)) and a slope of linear dependence of free energy of unfolding on GuHCl concentration (m-value) were estimated with the three equilibrium schemes. The data for all proteins, except apoA-II, fit with the three-state model, thus evidencing two-domain structure. The predicted folding rate of the four apoE in solution correlated with conformational stability. The dependence disappeared at the inclusion of apoA-I and apoA-IV into analysis and the m-values, adjusted for residue number in helices (m(rh)), differed between those for apoE and apoA-I/apoA-IV. However, the m(rh)-values for six proteins correlated positively with the fractional change in accessible surface area at unfolding for Phe, Lys and Asn, while negatively for Arg, Ala and Gly residues. The difference between the adjusted ΔG(rh)(H(2)O) values for apolipoproteins in complexes and in solution decreased at the increase of reduced temperature (T(obs)-T(t))/T(t). The induction of intrinsic disorder by arginine residues may be of primary importance in metabolism and function of exchangeable apolipoproteins, while their stability in nascent discoidal HDL is controlled by the physical state of phosphatidylcholine.
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17
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Leduc V, Domenger D, De Beaumont L, Lalonde D, Bélanger-Jasmin S, Poirier J. Function and comorbidities of apolipoprotein e in Alzheimer's disease. Int J Alzheimers Dis 2011; 2011:974361. [PMID: 21559182 PMCID: PMC3089878 DOI: 10.4061/2011/974361] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Accepted: 02/09/2011] [Indexed: 11/20/2022] Open
Abstract
Alzheimer's disease (AD)—the most common type of dementia among the elderly—represents one of the most challenging and urgent medical mysteries affecting our aging population. Although dominant inherited mutation in genes involved in the amyloid metabolism can elicit familial AD, the overwhelming majority of AD cases, dubbed sporadic AD, do not display this Mendelian inheritance pattern. Apolipoprotein E (APOE), the main lipid carrier protein in the central nervous system, is the only gene that has been robustly and consistently associated with AD risk. The purpose of the current paper is thus to highlight the pleiotropic roles and the structure-function relationship of APOE to stimulate both the functional characterization and the identification of novel lipid homeostasis-related molecular targets involved in AD.
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Affiliation(s)
- Valérie Leduc
- Department of Psychiatry, Douglas Mental Health University Institute, Perry Pavilion, E-3207.1, 6875 Lasalle Boulevard, Verdun, QC, Canada H4H1R3
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18
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Hsieh YH, Chou CY. Structural and functional characterization of human apolipoprotein E 72-166 peptides in both aqueous and lipid environments. J Biomed Sci 2011; 18:4. [PMID: 21219628 PMCID: PMC3022805 DOI: 10.1186/1423-0127-18-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Accepted: 01/10/2011] [Indexed: 12/03/2022] Open
Abstract
Backgrounds There are three apolipoprotein E (apoE) isoforms involved in human lipid homeostasis. In the present study, truncated apoE2-, apoE3- and apoE4-(72-166) peptides that are tailored to lack domain interactions are expressed and elucidated the structural and functional consequences. Methods & Results Circular dichroism analyses indicated that their secondary structure is still well organized. Analytical ultracentrifugation analyses demonstrated that apoE-(72-166) produces more complicated species in PBS. All three isoforms were significantly dissociated in the presence of dihexanoylphosphatidylcholine. Dimyristoylphosphatidylcholine turbidity clearance assay showed that apoE4-(72-166) maintains the highest lipid-binding capacity. Finally, only apoE4-(72-166) still maintained significant LDL receptor binding ability. Conclusions Overall, apoE4-(72-166) peptides displayed a higher lipid-binding and comparable receptor-binding ability as to full-length apoE. These findings provide the explanation of diverged functionality of truncated apoE isoforms.
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Affiliation(s)
- Yi-Hui Hsieh
- Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 112, Taiwan
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19
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Elliott DA, Halliday GM, Garner B. Apolipoprotein-E forms dimers in human frontal cortex and hippocampus. BMC Neurosci 2010; 11:23. [PMID: 20170526 PMCID: PMC2837047 DOI: 10.1186/1471-2202-11-23] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2009] [Accepted: 02/20/2010] [Indexed: 12/01/2022] Open
Abstract
Background Apolipoprotein-E (apoE) plays important roles in neurobiology and the apoE4 isoform increases risk for Alzheimer's disease (AD). ApoE3 and apoE2 are known to form disulphide-linked dimers in plasma and cerebrospinal fluid whereas apoE4 cannot form these dimers as it lacks a cysteine residue. Previous in vitro research indicates dimerisation of apoE3 has a significant impact on its functions related to cholesterol homeostasis and amyloid-beta peptide degradation. The possible occurrence of apoE dimers in cortical tissues has not been examined and was therefore assessed. Human frontal cortex and hippocampus from control and AD post-mortem samples were homogenised and analysed for apoE by western blotting under both reducing and non-reducing conditions. Results In apoE3 homozygous samples, ~12% of apoE was present as a homodimer and ~2% was detected as a 43 kDa heterodimer. The level of dimerisation was not significantly different when control and AD samples were compared. As expected, these dimerised forms of apoE were not detected in apoE4 homozygous samples but were detected in apoE3/4 heterozygotes at a level approximately 60% lower than seen in the apoE3 homozygous samples. Similar apoE3 dimers were also detected in lysates of SK-N-SH neuroblastoma cells and in freshly prepared rabbit brain homogenates. The addition of the thiol trapping agent, iodoacetamide, to block reactive thiols during both human and rabbit brain sample homogenisation and processing did not reduce the amount of apoE homodimer recovered. These data indicate that the apoE dimers we detected in the human brain are not likely to be post-mortem artefacts. Conclusion The identification of disulphide-linked apoE dimers in human cortical and hippocampal tissues represents a distinct structural difference between the apoE3 and apoE4 isoforms that may have functional consequences.
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Affiliation(s)
- David A Elliott
- Prince of Wales Medical Research Institute, Randwick NSW 2031, Australia
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20
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Elliott DA, Tsoi K, Holinkova S, Chan SL, Kim WS, Halliday GM, Rye KA, Garner B. Isoform-specific proteolysis of apolipoprotein-E in the brain. Neurobiol Aging 2009; 32:257-71. [PMID: 19278755 DOI: 10.1016/j.neurobiolaging.2009.02.006] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2008] [Revised: 02/01/2009] [Accepted: 02/03/2009] [Indexed: 11/19/2022]
Abstract
Apolipoprotein-E (apoE) plays important roles in neurobiology and the apoE4 isoform increases risk for Alzheimer's disease (AD). ApoE peptides are biologically active and may be produced in the brain. It is unclear if apoE proteolysis is dependent on isoform or AD status and this was addressed here. Hippocampus, frontal cortex, occipital lobe and cerebellum samples were homogenized into fractions that were soluble in Tris-buffered saline (TBS), Triton X-100 or guanidine hydrochloride and analysed for apoE fragmentation by Western blotting. Approximately 20% of apoE3 was detected as fragments and this was predominantly as a 25 kDa peptide in TBS-soluble fractions. The concentration of TBS-soluble apoE fragments was two- to three-fold higher in apoE3 compared to apoE4 subjects. This difference was observed in all areas of the brain examined and was not related to AD status. Cathepsin-D treatment generated apoE fragments that were very similar to those detected in brain, however, no apoE isoform-specific differences in susceptibility to cathepsin-D proteolysis were detected. This indicates that proteolytic processing of apoE to form soluble fragments in the human brain is dependent on apoE isoform but not AD status.
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Affiliation(s)
- David A Elliott
- Prince of Wales Medical Research Institute, Randwick, NSW 2031, Australia
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21
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Capillary isotachophoresis study of lipoprotein network sensitive to apolipoprotein E phenotype. 1. ApoE distribution between lipoproteins. Mol Cell Biochem 2009; 325:41-51. [DOI: 10.1007/s11010-008-0018-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2008] [Accepted: 12/30/2008] [Indexed: 10/21/2022]
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22
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Hauser PS, Raussens V, Yamamoto T, Abdullahi GE, Weers PMM, Sykes BD, Ryan RO. Semisynthesis and segmental isotope labeling of the apoE3 N-terminal domain using expressed protein ligation. J Lipid Res 2008; 50:1548-55. [PMID: 19098282 DOI: 10.1194/jlr.m800554-jlr200] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Apolipoprotein E (apoE) is an exchangeable apolipoprotein that functions as a ligand for members of the LDL receptor family, promoting lipoprotein clearance from the circulation. Productive receptor binding requires that apoE adopt an LDL receptor-active conformation through lipid association, and studies have shown that the 22 kDa N-terminal (NT) domain (residues 1-183) of apoE is both necessary and sufficient for receptor interaction. Using intein-mediated expressed protein ligation (EPL), a semisynthetic apoE3 NT has been generated for use in structure-function studies designed to probe the nature of the lipid-associated conformation of the protein. Circular dichroism spectroscopy of EPL-generated apoE3 NT revealed a secondary structure content similar to wild-type apoE3 NT. Likewise, lipid and LDL receptor binding studies revealed that EPL-generated apoE3 NT is functional. Subsequently, EPL was used to construct an apoE3 NT enriched with 15N solely and specifically in residues 112-183. 1H-15N heteronuclear single quantum correlation spectroscopy experiments revealed that the ligation product is correctly folded in solution, adopting a conformation similar to wild-type apoE3-NT. The results indicate that segmental isotope labeling can be used to define the lipid bound conformation of the receptor binding element of apoE as well as molecular details of its interaction with the LDL receptor.
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Affiliation(s)
- Paul S Hauser
- Center for Prevention of Obesity, Diabetes, and Cardiovascular Disease, Children's Hospital Oakland Research Institute, Oakland, CA 94609, USA
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23
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Dergunov AD, Visvikis-Siest S, Siest G. Statins as effectors of key activities involved in apoE-dependent VLDL metabolism: Review and hypothesis. Vascul Pharmacol 2008; 48:70-5. [DOI: 10.1016/j.vph.2007.12.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2007] [Revised: 10/31/2007] [Accepted: 12/05/2007] [Indexed: 11/26/2022]
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24
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Dergunov AD. Role of ApoE in conformation-prone diseases and atherosclerosis. BIOCHEMISTRY (MOSCOW) 2006; 71:707-12. [PMID: 16903824 DOI: 10.1134/s0006297906070029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Three isoforms of human plasma apolipoprotein E (apoE) are ligands to lipoprotein receptors and influence in different manner the synthesis and catabolism of pro-atherogenic triglyceride-rich lipoproteins. Among three isoforms, the apoE4 isoform is associated with increased frequency of atherosclerosis and Alzheimer's disease (AD). The conformational transitions of beta-amyloid (Abeta) influenced by apoE and serum amyloid P (SAP) component are key events in AD development, the accumulation of intermediate diffusible and soluble oligomers of Abeta being of particular significance. SAP and apoE, in a different manner for the three isoforms, serve as "pathological" chaperones during the aggregation of Abeta considered as a conformation-prone process. In turn, apoE consisting of two domains self-associates in solution and intermediate structures differently populated for the three isoforms exist. The different structures of the three isoforms determine their different distribution among various plasma lipoproteins. The structural and metabolic consideration of the common apoE pathway(s) in two pathologies assumes four molecular targets for AD correction: (i) inhibition of the accumulation of diffusible soluble Abeta oligomers; (ii) inhibition of apoE synthesis and secretion by astrocytes, in particular, under lipid-lowering therapy; (iii) inhibition of the binding of apoE and/or SAP to Abeta; (iv) stimulation of the expression of cholesterol transporter ABCA1.
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Affiliation(s)
- A D Dergunov
- National Research Center for Preventive Medicine, Moscow, 101990, Russia.
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25
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Zhang L, Guo P, Zhang H, Jing G. Cooperative unfolding of Escherichia coli ribosome recycling factor originating from its domain-domain interaction and its implication for function. Arch Biochem Biophys 2006; 450:191-202. [PMID: 16684502 DOI: 10.1016/j.abb.2006.03.029] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2006] [Revised: 03/24/2006] [Accepted: 03/27/2006] [Indexed: 11/27/2022]
Abstract
Cooperative unfolding of Escherichia coli ribosome recycling factor (RRF) and its implication for function were investigated by comparing the in vitro unfolding and the in vivo activity of wild-type E. coli RRF and its temperature-sensitive mutant RRF(V117D). The experiments show that mutation V117D at domain I could perturb the domain II structure as evidenced in the near-UV CD and tyrosine fluorescence spectra though no significant globular conformation change occurred. Both equilibrium unfolding induced by heat or denaturant and kinetic unfolding induced by denaturant obey the two-state transition model, indicating V117D mutation does not perturb the efficient interdomain interaction, which results in cooperative unfolding of the RRF protein. However, the mutation significantly destabilizes the E. coli RRF protein, moving the thermal unfolding transition temperature range from 50-65 to 35-50 degrees C, which spans the non-permissive temperature for the growth of E. coli LJ14 strain (frr(ts)). The in vivo activity assays showed that although V117D mutation results in a temperature sensitive phenotype of E. coli LJ14 strain (frr(ts)), over-expression of mutant RRF(V117D) can eliminate the temperature sensitive phenotype at the non-permissive temperature (42 degrees C). Taking all the results into consideration, it can be suggested that the mechanism of the temperature sensitive phenotype of the E. coli LJ14 cells is due to inactivation of mutant RRF(V117D) caused by unfolding at the non-permissive temperatures.
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Affiliation(s)
- Liqiang Zhang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, China
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