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Kloske CM, Belloy ME, Blue EE, Bowman GR, Carrillo MC, Chen X, Chiba-Falek O, Davis AA, Paolo GD, Garretti F, Gate D, Golden LR, Heinecke JW, Herz J, Huang Y, Iadecola C, Johnson LA, Kanekiyo T, Karch CM, Khvorova A, Koppes-den Hertog SJ, Lamb BT, Lawler PE, Guen YL, Litvinchuk A, Liu CC, Mahinrad S, Marcora E, Marino C, Michaelson DM, Miller JJ, Morganti JM, Narayan PS, Naslavsky MS, Oosthoek M, Ramachandran KV, Ramakrishnan A, Raulin AC, Robert A, Saleh RNM, Sexton C, Shah N, Shue F, Sible IJ, Soranno A, Strickland MR, Tcw J, Thierry M, Tsai LH, Tuckey RA, Ulrich JD, van der Kant R, Wang N, Wellington CL, Weninger SC, Yassine HN, Zhao N, Bu G, Goate AM, Holtzman DM. Advancements in APOE and dementia research: Highlights from the 2023 AAIC Advancements: APOE conference. Alzheimers Dement 2024. [PMID: 39031528 DOI: 10.1002/alz.13877] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Revised: 04/12/2024] [Accepted: 04/15/2024] [Indexed: 07/22/2024]
Abstract
INTRODUCTION The apolipoprotein E gene (APOE) is an established central player in the pathogenesis of Alzheimer's disease (AD), with distinct apoE isoforms exerting diverse effects. apoE influences not only amyloid-beta and tau pathologies but also lipid and energy metabolism, neuroinflammation, cerebral vascular health, and sex-dependent disease manifestations. Furthermore, ancestral background may significantly impact the link between APOE and AD, underscoring the need for more inclusive research. METHODS In 2023, the Alzheimer's Association convened multidisciplinary researchers at the "AAIC Advancements: APOE" conference to discuss various topics, including apoE isoforms and their roles in AD pathogenesis, progress in apoE-targeted therapeutic strategies, updates on disease models and interventions that modulate apoE expression and function. RESULTS This manuscript presents highlights from the conference and provides an overview of opportunities for further research in the field. DISCUSSION Understanding apoE's multifaceted roles in AD pathogenesis will help develop targeted interventions for AD and advance the field of AD precision medicine. HIGHLIGHTS APOE is a central player in the pathogenesis of Alzheimer's disease. APOE exerts a numerous effects throughout the brain on amyloid-beta, tau, and other pathways. The AAIC Advancements: APOE conference encouraged discussions and collaborations on understanding the role of APOE.
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Affiliation(s)
| | - Michael E Belloy
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, Palo Alto, California, USA
- NeuroGenomics and Informatics Center, Washington University School of Medicine, St. Louis, Missouri, USA
- Department of Neurology, Washington University School of Medicine, St. Louis, Missouri, St. Louis, Missouri, USA
| | - Elizabeth E Blue
- Division of Medical Genetics, Department of Medicine, University of Washington, Seattle, Washington, USA
- Institute for Public Health Genetics, University of Washington, Seattle, Washington, USA
| | - Gregory R Bowman
- Departments of Biochemistry & Biophysics and Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | | | - Xiaoying Chen
- Department of Neurology, Hope Center for Neurological Disorders, Knight Alzheimer's Disease Research Center, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Ornit Chiba-Falek
- Division of Translational Brain Sciences, Department of Neurology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Albert A Davis
- Department of Neurology Hope Center for Neurological Disorders Washington University School of Medicine, St. Louis, Missouri, USA
| | | | - Francesca Garretti
- Ronald M. Loeb Center for Alzheimer's Disease, New York, New York, USA
- Department of Genetics & Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - David Gate
- The Ken & Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Lesley R Golden
- Department of Physiology, University of Kentucky, Lexington, Kentucky, USA
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, Kentucky, USA
| | - Jay W Heinecke
- Department of Medicine, University of Washington, UV Medicine, Seattle, Washington, USA
| | - Joachim Herz
- Center for Translational Neurodegeneration Research, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Yadong Huang
- Gladstone Institute of Neurological Disease, Gladstone Institutes, San Francisco, California, USA
- Department of Neurology, University of California, San Francisco, California, USA
| | - Costantino Iadecola
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, New York, USA
| | - Lance A Johnson
- Department of Physiology, University of Kentucky, Lexington, Kentucky, USA
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, Kentucky, USA
| | - Takahisa Kanekiyo
- Department of Neuroscience, Mayo Clinic Jacksonville, Jacksonville, Florida, USA
| | - Celeste M Karch
- Department of Psychiatry, Washington University in St Louis, St. Louis, Missouri, USA
| | - Anastasia Khvorova
- RNA Therapeutic Institute, UMass Chan Medical School, Worcester, Massachusetts, USA
| | - Sascha J Koppes-den Hertog
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research (CNCR), VU University Amsterdam, Amsterdam, USA
- Alzheimer Center Amsterdam, Department of Neurology, Amsterdam Neuroscience, Amsterdam University Medical Center, Amsterdam, USA
| | - Bruce T Lamb
- Stark Neurosciences Research Institute Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Paige E Lawler
- Department of Neurology, Washington University School of Medicine, St. Louis, Missouri, St. Louis, Missouri, USA
- The Tracy Family SILQ Center, Washington University School of Medicine, Indianapolis, Indiana, USA
| | - Yann Le Guen
- Department of Neurology and Neurological Sciences, Stanford University, Palo Alto, California, USA
- Institut du Cerveau-Paris Brain Institute-ICM, Paris, France
| | - Alexandra Litvinchuk
- Department of Neurology, Hope Center for Neurological Disorders, Knight Alzheimer's Disease Research Center, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Chia-Chen Liu
- Department of Neuroscience, Mayo Clinic Jacksonville, Jacksonville, Florida, USA
| | | | - Edoardo Marcora
- Department of Genetics and Genomic Sciences, Nash Family Department of Neuroscience, Icahn Genomics Institute; Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Claudia Marino
- Schepens Eye Research Institute of Mass Eye and Ear and Department of Ophthalmology at Harvard Medical School, Boston, Massachusetts, USA
| | | | - Justin J Miller
- Departments of Biochemistry & Biophysics and Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Josh M Morganti
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, Kentucky, USA
- Department of Neuroscience, University of Kentucky, Lexington, Kentucky, USA
| | - Priyanka S Narayan
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institute of Neurological Disorders and Stroke, Center for Alzheimer's and Related Dementias (CARD), National Institutes of Health, Maryland, USA
| | - Michel S Naslavsky
- Human Genome and Stem-cell Research Center, Biosciences Institute, University of São Paulo, Rua do Matao, São Paulo, Brazil
- Hospital Israelita Albert Einstein, Avenida Albert Einstein, São Paulo, Brazil
| | - Marlies Oosthoek
- Neurochemistry Laboratory, Department of Laboratory Medicine, Vrije Universiteit Amsterdam, Amsterdam UMC, Amsterdam, Netherlands
| | - Kapil V Ramachandran
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University Vagelos College of Physicians and Surgeons, New York, New York, USA
- Department of Neurology, Columbia University Irving Medical Center, New York, New York, USA
- Department of Neuroscience, Columbia University Vagelos College of Physicians and Surgeons, New York, USA
| | - Abhirami Ramakrishnan
- The Ken & Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | | | - Aiko Robert
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research (CNCR), VU University Amsterdam, Amsterdam, USA
- Alzheimer Center Amsterdam, Department of Neurology, Amsterdam Neuroscience, Amsterdam University Medical Center, Amsterdam, USA
| | - Rasha N M Saleh
- Norwich Medical School, University of East Anglia, UK Clinical and Chemical Pathology, Norfolk, UK
- Faculty of Medicine, Alexandria University, Alexandria Governorate, Egypt
| | | | | | | | - Isabel J Sible
- University of Southern California, Los Angeles, California, USA
| | - Andrea Soranno
- Washington University in Saint Louis, St. Louis, Missouri, USA, St. Louis, Missouri, USA
| | - Michael R Strickland
- Department of Neurology, Washington University School of Medicine, St. Louis, Missouri, St. Louis, Missouri, USA
| | - Julia Tcw
- Department of Pharmacology, Physiology & Biophysics, Chobanian and Avedisian School of Medicine, Boston University, Boston, Massachusetts, USA
- Bioinformatics Program, Faculty of Computing & Data Sciences, Boston University, Boston, Massachusetts, USA
| | - Manon Thierry
- Center for Cognitive Neurology, Department of Neurology, New York University Grossman School of Medicine, New York, New York, USA
| | - Li-Huei Tsai
- Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Ryan A Tuckey
- Department of Neurology, Center for Neurodegeneration and Experimental Therapeutics, Medical Scientist Training Program, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Jason D Ulrich
- Department of Neurology, Hope Center for Neurological Disorders, Knight Alzheimer's Disease Research Center, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Rik van der Kant
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research (CNCR), VU University Amsterdam, Amsterdam, USA
- Alzheimer Center Amsterdam, Department of Neurology, Amsterdam Neuroscience, Amsterdam University Medical Center, Amsterdam, USA
| | - Na Wang
- Mayo Clinic Rochester, Rochester, Minnesota, USA
| | - Cheryl L Wellington
- Djavad Mowafaghian Centre for Brain Health Department of Pathology and Laboratory Medicine International Collaboration on Repair Discoveries School of Biomedical Engineering University of British Columbia, Vancouver, Canada
| | | | - Hussein N Yassine
- Department of Neurology, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Na Zhao
- Department of Neuroscience, Mayo Clinic Jacksonville, Jacksonville, Florida, USA
| | - Guojun Bu
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
| | - Alison M Goate
- Department of Genetics & Genomic Sciences, Ronald M. Loeb Center for Alzheimer's disease, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - David M Holtzman
- Department of Neurology, Hope Center for Neurological Disorders, Knight Alzheimer's Disease Research Center, Washington University School of Medicine, St. Louis, Missouri, USA
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Strickland MR, Rau MJ, Summers B, Basore K, Wulf J, Jiang H, Chen Y, Ulrich JD, Randolph GJ, Zhang R, Fitzpatrick JAJ, Cashikar AG, Holtzman DM. Apolipoprotein E secreted by astrocytes forms antiparallel dimers in discoidal lipoproteins. Neuron 2024; 112:1100-1109.e5. [PMID: 38266643 PMCID: PMC10994765 DOI: 10.1016/j.neuron.2023.12.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 11/24/2023] [Accepted: 12/22/2023] [Indexed: 01/26/2024]
Abstract
The Apolipoprotein E gene (APOE) is of great interest due to its role as a risk factor for late-onset Alzheimer's disease. ApoE is secreted by astrocytes in the central nervous system in high-density lipoprotein (HDL)-like lipoproteins. Structural models of lipidated ApoE of high resolution could aid in a mechanistic understanding of how ApoE functions in health and disease. Using monoclonal Fab and F(ab')2 fragments, we characterize the structure of lipidated ApoE on astrocyte-secreted lipoproteins. Our results provide support for the "double-belt" model of ApoE in nascent discoidal HDL-like lipoproteins, where two ApoE proteins wrap around the nanodisc in an antiparallel conformation. We further show that lipidated, recombinant ApoE accurately models astrocyte-secreted ApoE lipoproteins. Cryogenic electron microscopy of recombinant lipidated ApoE further supports ApoE adopting antiparallel dimers in nascent discoidal lipoproteins.
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Affiliation(s)
| | - Michael J Rau
- Washington University Center for Cellular Imaging, 660 S. Euclid Ave., St. Louis, MO 63110, USA
| | - Brock Summers
- Washington University Center for Cellular Imaging, 660 S. Euclid Ave., St. Louis, MO 63110, USA
| | - Katherine Basore
- Washington University Center for Cellular Imaging, 660 S. Euclid Ave., St. Louis, MO 63110, USA
| | - John Wulf
- Washington University Center for Cellular Imaging, 660 S. Euclid Ave., St. Louis, MO 63110, USA
| | - Hong Jiang
- Department of Neurology, 660 S. Euclid Ave., St. Louis, MO 63110, USA
| | - Yun Chen
- Department of Neurology, 660 S. Euclid Ave., St. Louis, MO 63110, USA; Department of Pathology and Immunology, 660 S. Euclid Ave., St. Louis, MO 63110, USA
| | - Jason D Ulrich
- Department of Neurology, 660 S. Euclid Ave., St. Louis, MO 63110, USA; Hope Center for Neurological Disorders, 660 S. Euclid Ave., St. Louis, MO 63110, USA; Knight Alzheimer's Disease Research Center, 4488 Forest Park Ave., St. Louis, MO 63108, USA
| | - Gwendalyn J Randolph
- Department of Pathology and Immunology, 660 S. Euclid Ave., St. Louis, MO 63110, USA
| | - Rui Zhang
- Department of Biochemistry and Molecular Biophysics, 660 S. Euclid Ave., St. Louis, MO 63110, USA
| | - James A J Fitzpatrick
- Washington University Center for Cellular Imaging, 660 S. Euclid Ave., St. Louis, MO 63110, USA
| | - Anil G Cashikar
- Hope Center for Neurological Disorders, 660 S. Euclid Ave., St. Louis, MO 63110, USA; Department of Psychiatry, 660 S. Euclid Ave., St. Louis, MO 63110, USA; Taylor Family institute for Innovative Psychiatric Research, 660 S. Euclid Ave., St. Louis, MO 63110, USA
| | - David M Holtzman
- Department of Neurology, 660 S. Euclid Ave., St. Louis, MO 63110, USA; Hope Center for Neurological Disorders, 660 S. Euclid Ave., St. Louis, MO 63110, USA; Knight Alzheimer's Disease Research Center, 4488 Forest Park Ave., St. Louis, MO 63108, USA.
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Allen P, Smith AC, Benedicto V, Abdulhasan A, Narayanaswami V, Tapavicza E. Molecular dynamics simulation of apolipoprotein E3 lipid nanodiscs. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2024; 1866:184230. [PMID: 37704040 DOI: 10.1016/j.bbamem.2023.184230] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2023] [Revised: 09/06/2023] [Accepted: 09/07/2023] [Indexed: 09/15/2023]
Abstract
Nanodiscs are binary discoidal complexes of a phospholipid bilayer circumscribed by belt-like helical scaffold proteins. Using coarse-grained and all-atom molecular dynamics simulations, we explore the stability, size, and structure of nanodiscs formed between the N-terminal domain of apolipoprotein E3 (apoE3-NT) and variable number of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) molecules. We study both parallel and antiparallel double-belt configurations, consisting of four proteins per nanodisc. Our simulations predict nanodiscs containing between 240 and 420 DMPC molecules to be stable. The antiparallel configurations exhibit an average of 1.6 times more amino acid interactions between protein chains and 2 times more ionic contacts, compared to the parallel configuration. With one exception, DMPC order parameters are consistently larger in the antiparallel configuration than in the parallel one. In most cases, the root mean square deviation of the positions of the protein backbone atoms is smaller in the antiparallel configuration. We further report nanodisc size, thickness, radius of gyration, and solvent accessible surface area. Combining all investigated parameters, we hypothesize the antiparallel protein configuration leading to more stable and more rigid nanodiscs than the parallel one.
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Affiliation(s)
- Patrick Allen
- Department of Chemistry and Biochemistry, California State University, Long Beach, 1250 Bellflower Boulevard, Long Beach, 90840, CA, USA
| | - Adam C Smith
- Department of Chemistry and Biochemistry, California State University, Long Beach, 1250 Bellflower Boulevard, Long Beach, 90840, CA, USA
| | - Vernon Benedicto
- Department of Chemistry and Biochemistry, California State University, Long Beach, 1250 Bellflower Boulevard, Long Beach, 90840, CA, USA
| | - Abbas Abdulhasan
- Department of Chemistry and Biochemistry, California State University, Long Beach, 1250 Bellflower Boulevard, Long Beach, 90840, CA, USA
| | - Vasanthy Narayanaswami
- Department of Chemistry and Biochemistry, California State University, Long Beach, 1250 Bellflower Boulevard, Long Beach, 90840, CA, USA
| | - Enrico Tapavicza
- Department of Chemistry and Biochemistry, California State University, Long Beach, 1250 Bellflower Boulevard, Long Beach, 90840, CA, USA.
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Insights into the C-terminal domain of apolipoprotein E from chimera studies with apolipophorin III. Mol Cell Biochem 2023; 478:173-183. [PMID: 35763125 DOI: 10.1007/s11010-022-04497-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Accepted: 06/01/2022] [Indexed: 01/17/2023]
Abstract
Apolipoprotein E3 (apoE) is a critical cholesterol transport protein in humans and is composed of two domains: a well characterized N-terminal (NT) domain that harbors the low-density lipoprotein LDL receptor, and a less understood C-terminal (CT) domain that is the site of protein oligomerization and initiation of lipid binding. To better understand the domain structure of apoE, the CT domain was fused to apolipophorin III (apoLp-III), a single-domain, monomeric apolipoprotein of insect origin, to yield a chimeric protein, apoLp-III/CT-apoE. Recombinant apoLp-III/CT-apoE maintained an overall helical content similar to that of the parent proteins, while chemical induced unfolding studies indicated that its structural integrity was not compromised. Analysis using 1-anilinonaphthalene-8-sulfonic acid (ANS), a sensitive fluorescent indicator of exposed hydrophobic sites and protein folding, demonstrated that whereas apoLp-III provided few ANS binding sites, apoLp-III/CT-apoE harbored an abundance of ANS binding sites. Thus, this indicated tertiary structure formation in CT-apoE when part of the chimera. Size-exclusion chromatography and chemical crosslinking analysis demonstrated that while apoLp-III is monomeric, the chimeric protein formed large oligomeric complexes, similar to native apoE3. Compared to apoLp-III, the chimera showed a two-fold enhancement in phospholipid vesicle solubilization rates and a significantly improved ability to bind to lipolyzed low-density lipoprotein, preventing the onset of lipoprotein aggregation at concentrations comparable to that of parent CT-apoE. These results confirm that high lipid binding and self-association sites are located in the CT domain of apoE, and that these properties can be transferred to an unrelated apolipoprotein, demonstrating that these properties operate independently from the NT domain.
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Li Z, Shue F, Zhao N, Shinohara M, Bu G. APOE2: protective mechanism and therapeutic implications for Alzheimer's disease. Mol Neurodegener 2020; 15:63. [PMID: 33148290 PMCID: PMC7640652 DOI: 10.1186/s13024-020-00413-4] [Citation(s) in RCA: 103] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Accepted: 10/17/2020] [Indexed: 02/06/2023] Open
Abstract
Investigations of apolipoprotein E (APOE) gene, the major genetic risk modifier for Alzheimer's disease (AD), have yielded significant insights into the pathogenic mechanism. Among the three common coding variants, APOE*ε4 increases, whereas APOE*ε2 decreases the risk of late-onset AD compared with APOE*ε3. Despite increased understanding of the detrimental effect of APOE*ε4, it remains unclear how APOE*ε2 confers protection against AD. Accumulating evidence suggests that APOE*ε2 protects against AD through both amyloid-β (Aβ)-dependent and independent mechanisms. In addition, APOE*ε2 has been identified as a longevity gene, suggesting a systemic effect of APOE*ε2 on the aging process. However, APOE*ε2 is not entirely benign; APOE*ε2 carriers exhibit increased risk of certain cerebrovascular diseases and neurological disorders. Here, we review evidence from both human and animal studies demonstrating the protective effect of APOE*ε2 against AD and propose a working model depicting potential underlying mechanisms. Finally, we discuss potential therapeutic strategies designed to leverage the protective effect of APOE2 to treat AD.
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Affiliation(s)
- Zonghua Li
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA
| | - Francis Shue
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA
- Neuroscience Graduate Program, Mayo Clinic, Jacksonville, FL, USA
| | - Na Zhao
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA
| | - Mitsuru Shinohara
- Department of Aging Neurobiology, National Center for Geriatrics and Gerontology, 7-430 Morioka, Obu, Aichi, 474-8511, Japan.
| | - Guojun Bu
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA.
- Neuroscience Graduate Program, Mayo Clinic, Jacksonville, FL, USA.
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Kai-Han T, Abhari D, Narayanaswami V. Conformational analysis of apolipoprotein E3/E4 heteromerization. FEBS J 2019; 286:1986-1998. [PMID: 30802357 PMCID: PMC6733585 DOI: 10.1111/febs.14794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Revised: 01/29/2019] [Accepted: 02/22/2019] [Indexed: 11/26/2022]
Abstract
Apolipoprotein E (apoE) is a 299 residue, exchangeable apolipoprotein that has essential roles in cholesterol homeostasis and reverse cholesterol transport. It is a two-domain protein with the C-terminal (CT) domain mediating protein self-association via helix-helix interactions. In humans, the APOE gene is polymorphic with three common alleles, ε2, ε3, and ε4, occurring in frequencies of ~ 5%, 77%, and 18%, respectively. Heterozygotes expressing apoE3 and apoE4 isoforms, which differ in residue at position 112 in the N-terminal domain (C112 in apoE3 and R112 in apoE4), represent the highest population of ε4 carriers, an allele highly associated with Alzheimer's disease. The objective of this study was to determine if apoE3 and apoE4 have the ability to hybridize to form a heteromer in lipid-free state. Refolding an equimolar mixture of His-apoE3 and FLAG-apoE4 (or vice versa) followed by pull-down and immunoblotting indicated formation of apoE3/apoE4 heteromers. Förster resonance energy transfer between donor fluorophore on one isoform and acceptor on the other, both located in the respective CT domains, revealed a distance of separation of ~ 46 Å between the donor/acceptor pair. Similarly, a quencher placed on one was able to mediate significant quenching of fluorescence emission on the other, indicative of spatial proximity within collisional distance between the two. ApoE3/apoE4 heteromer association was also noted in lipid-associated state in reconstituted lipoprotein particles. The possibility of heteromerization of apoE3/apoE4 bears implications in the potential mitigating role of apoE3 on the folding and physiological behavior of apoE4 and its role in maintaining cholesterol homeostasis.
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Affiliation(s)
| | | | - Vasanthy Narayanaswami
- Department of Chemistry and Biochemistry, 1250 Bellflower Blvd., California State University Long Beach, Long Beach, CA 90840, USA
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Ordered opening of LDL receptor binding domain of human apolipoprotein E3 revealed by hydrogen/deuterium exchange mass spectrometry and fluorescence spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2018; 1866:1165-1173. [PMID: 30282614 DOI: 10.1016/j.bbapap.2018.08.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2018] [Revised: 07/31/2018] [Accepted: 08/18/2018] [Indexed: 01/18/2023]
Abstract
Apolipoprotein E3 (apoE3) is an exchangeable apolipoprotein that plays a critical role in cholesterol homeostasis. The N-terminal (NT) domain of apoE3 (residues 1-191) is folded into a helix bundle comprised of 4 amphipathic α-helices: H1, H2, H3 and H4, flanked by flexible helices N1 and N2, and Hinge Helix 1 (Hinge H1), at the N-and C-terminal sides of the helix bundle, respectively. The NT domain plays a critical role in binding to the low density lipoprotein receptor (LDLR), which eventually leads to lowering of plasma cholesterol levels. In order to be recognized by the LDLR, the helix bundle has to open and undergo a conformational change. The objective of the study was to understand the mechanism of opening of the helix bundle. Hydrogen/deuterium exchange mass spectrometry (HDX-MS) revealed that apoE3 NT domain adopts several disordered and unfolded regions, with H2 exhibiting relatively little protection against exchange-in compared to H1, H3, and H4. Site-directed fluorescence labeling indicated that H2 not only has the highest degree of solvent exposure but also the most flexibility in the helix bundle. It also indicated that the lipoprotein behavior of H1 was significnatly different from that of H2, H3 and H4. These results suggest that the opening of the helix bundle is likely initiated at the flexible end of H2 and the loop linking H2/H3, and involves movement of H2/H3 away from H1/H4. Together, these observations offer mechanistic insight suggesting a regulated helix bundle opening of apoE3 NT domain can be triggered by lipid binding.
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Henry N, Krammer EM, Stengel F, Adams Q, Van Liefferinge F, Hubin E, Chaves R, Efremov R, Aebersold R, Vandenbussche G, Prévost M, Raussens V, Deroo S. Lipidated apolipoprotein E4 structure and its receptor binding mechanism determined by a combined cross-linking coupled to mass spectrometry and molecular dynamics approach. PLoS Comput Biol 2018; 14:e1006165. [PMID: 29933361 PMCID: PMC6033463 DOI: 10.1371/journal.pcbi.1006165] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 07/05/2018] [Accepted: 04/30/2018] [Indexed: 11/18/2022] Open
Abstract
Apolipoprotein E (apoE) is a forefront actor in the transport of lipids and the maintenance of cholesterol homeostasis, and is also strongly implicated in Alzheimer’s disease. Upon lipid-binding apoE adopts a conformational state that mediates the receptor-induced internalization of lipoproteins. Due to its inherent structural dynamics and the presence of lipids, the structure of the biologically active apoE remains so far poorly described. To address this issue, we developed an innovative hybrid method combining experimental data with molecular modeling and dynamics to generate comprehensive models of the lipidated apoE4 isoform. Chemical cross-linking combined with mass spectrometry provided distance restraints, characterizing the three-dimensional organization of apoE4 molecules at the surface of lipidic nanoparticles. The ensemble of spatial restraints was then rationalized in an original molecular modeling approach to generate monomeric models of apoE4 that advocated the existence of two alternative conformations. These two models point towards an activation mechanism of apoE4 relying on a regulation of the accessibility of its receptor binding region. Further, molecular dynamics simulations of the dimerized and lipidated apoE4 monomeric conformations revealed an elongation of the apoE N-terminal domain, whereby helix 4 is rearranged, together with Arg172, into a proper orientation essential for lipoprotein receptor association. Overall, our results show how apoE4 adapts its conformation for the recognition of the low density lipoprotein receptor and we propose a novel mechanism of activation for apoE4 that is based on accessibility and remodeling of the receptor binding region. Among the proteins involved in the transport of lipids and their distribution to the cells, apolipoprotein E (apoE) mediates the internalization of cholesterol rich lipoproteins by acting as a ligand for cell-surface receptors. In the central nervous system, while apoE is the major cholesterol transport protein, a dysfunction of apoE in the transport and metabolism of lipids is associated with Alzheimer’s disease. A molecular understanding of the mechanisms underlying the receptor binding abilities of apoE is crucial to address its biological functions, but is so far hindered by the dynamic and complex nature of these assemblies. We have designed an original hybrid approach combining experimental data and bioinformatics tools to generate high resolution models of lipidated apoE. Based on these models, we can propose how apoE adapts its conformation at the surface of lipid nanoparticles. Further, we propose a novel mechanism of regulation of the activation and receptor recognition of apoE that could prove valuable to interpret its role in Alzheimer and apoE-related cardiovascular diseases.
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Affiliation(s)
- Nicolas Henry
- Center for Structural Biology and Bioinformatics, Structure and Function of Biological Membranes, Faculté des Sciences, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - Eva-Maria Krammer
- Center for Structural Biology and Bioinformatics, Structure and Function of Biological Membranes, Faculté des Sciences, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - Florian Stengel
- Department of Biology, Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland
- Department of Biology, University of Konstanz, Konstanz, Germany
| | - Quentin Adams
- Center for Structural Biology and Bioinformatics, Structure and Function of Biological Membranes, Faculté des Sciences, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - François Van Liefferinge
- Center for Structural Biology and Bioinformatics, Structure and Function of Biological Membranes, Faculté des Sciences, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - Ellen Hubin
- Structural Biology Research Center, VIB, Brussels, Belgium
- Structural Biology Brussels, Department of Biotechnology (DBIT), Vrije Universiteit Brussel (VUB), Brussels, Belgium
- Nanobiophysics Group, MIRA Institute for Biomedical Technology and Technical Medicine, Faculty of Science and Technology, University of Twente, Enschede, The Netherlands
| | - Rui Chaves
- Structural Biology Research Center, VIB, Brussels, Belgium
- Structural Biology Brussels, Department of Biotechnology (DBIT), Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Rouslan Efremov
- Structural Biology Research Center, VIB, Brussels, Belgium
- Structural Biology Brussels, Department of Biotechnology (DBIT), Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Ruedi Aebersold
- Department of Biology, Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland
- Faculty of Science, University of Zurich, Zurich, Switzerland
| | - Guy Vandenbussche
- Center for Structural Biology and Bioinformatics, Structure and Function of Biological Membranes, Faculté des Sciences, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - Martine Prévost
- Center for Structural Biology and Bioinformatics, Structure and Function of Biological Membranes, Faculté des Sciences, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - Vincent Raussens
- Center for Structural Biology and Bioinformatics, Structure and Function of Biological Membranes, Faculté des Sciences, Université Libre de Bruxelles (ULB), Brussels, Belgium
- * E-mail: (SD); (VT)
| | - Stéphanie Deroo
- Center for Structural Biology and Bioinformatics, Structure and Function of Biological Membranes, Faculté des Sciences, Université Libre de Bruxelles (ULB), Brussels, Belgium
- * E-mail: (SD); (VT)
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9
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Pederzoli F, Tosi G, Genovese F, Belletti D, Vandelli MA, Ballestrazzi A, Forni F, Ruozi B. Qualitative and semiquantitative analysis of the protein coronas associated to different functionalized nanoparticles. Nanomedicine (Lond) 2018; 13:407-422. [PMID: 29345202 DOI: 10.2217/nnm-2017-0250] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
AIM The investigation on protein coronas (PCs) adsorbed onto nanoparticle (NP) surface is representing an open issue due to difficulties in detection and clear isolation of the adsorbed proteins. In this study, we investigated protocols able to isolate the compositions of PCs of three polymeric NPs. MATERIALS & METHODS Unfunctionalized NPs and two functionalized NPs were considered as proof-of-concept for the qualitative and semiquantitative analysis of both the corona levels (stably or weakly adsorbed coronas [SC/WC]) of these different nanocarriers. RESULTS The protocols applied were able to discriminate between the SC and WC. In particular, experimental results indicated that stably adsorbed coronas are prevalently composed by ApoE, while WC by albumin in all the NPs. Otherwise, some differences in WC could be correlated with surface functionalization. CONCLUSION This experimental approach allows characterizing the whole PCs, proposing a protocol for isolation of different types of proteins composing PCs.
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Affiliation(s)
- Francesca Pederzoli
- Department of Life Sciences, University of Modena & Reggio Emilia, Via Campi 103, 41125 Modena, Italy
| | - Giovanni Tosi
- Department of Life Sciences, University of Modena & Reggio Emilia, Via Campi 103, 41125 Modena, Italy
| | - Filippo Genovese
- Centro Interdipartimentale Grandi Strumenti, University of Modena & Reggio Emilia, via Campi 185, 41125 Modena, Italy
| | - Daniela Belletti
- Department of Life Sciences, University of Modena & Reggio Emilia, Via Campi 103, 41125 Modena, Italy
| | - Maria Angela Vandelli
- Department of Life Sciences, University of Modena & Reggio Emilia, Via Campi 103, 41125 Modena, Italy
| | - Antonio Ballestrazzi
- Department of Scienze Fisiche, Informatiche e Matematiche, University of Modena & Reggio Emilia, Via Campi 213/a, 41125 Modena, Italy
| | - Flavio Forni
- Department of Life Sciences, University of Modena & Reggio Emilia, Via Campi 103, 41125 Modena, Italy
| | - Barbara Ruozi
- Department of Life Sciences, University of Modena & Reggio Emilia, Via Campi 103, 41125 Modena, Italy
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10
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Rajora MA, Ding L, Valic M, Jiang W, Overchuk M, Chen J, Zheng G. Tailored theranostic apolipoprotein E3 porphyrin-lipid nanoparticles target glioblastoma. Chem Sci 2017; 8:5371-5384. [PMID: 28970916 PMCID: PMC5609152 DOI: 10.1039/c7sc00732a] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Accepted: 05/18/2017] [Indexed: 12/21/2022] Open
Abstract
Size-controlled discoidal and cholesteryl oleated-loaded spherical, intrinsically multimodal porphyrin-lipid nanoparticles targeted glioblastoma via apoE3 and LDLR.
The development of curative glioblastoma treatments and tumour-specific contrast agents that can overcome the blood–brain barrier (BBB) and infiltrative tumour morphology remains a challenge. Apolipoprotein E3 (apoE3) is a high density lipoprotein apolipoprotein that chaperones the transcytosis of nanoparticles across the BBB, and displays high-affinity binding with the low density lipoprotein receptor (LDLR), a cell-surface receptor overexpressed by glioblastoma cells. This LDLR overexpression and apoE3 binding capacity was exploited for the development of glioblastoma-targeted porphyrin-lipid apoE3 lipid nanoparticles (pyE-LNs) with intrinsic theranostic properties. Size-controlled discoidal and cholesteryl oleate (CO)-loaded spherical pyE-LNs were synthesized through the systematic variation of particle composition, which dictated nanoparticle size and morphology. Composition optimization yielded 30 nm pyE-LNs with stable loading of apoE3 and porphyrin-lipid that simultaneously conferred the nanoparticles with glioblastoma targeting and activatable near-infrared fluorescence imaging functionalities. A 4-fold higher uptake of pyE-LNs by LDLR-expressing U87 glioblastomas cells relative to minimally expressing ldlA7 cells was observed in vitro. This uptake was a result of receptor-mediated endocytosis, which could be inhibited through LDL competition and acetylation of particle apoE3 moieties. ApoE3-dependent delivery of pyE-LN to glioblastomas was also demonstrated in orthotopic U87-GFP tumour-bearing animals. Quantification of CO-loaded pyE-LN biodistribution demonstrated successful selective uptake of porphyrin by malignant tissue, with a 4 : 1 tumour : healthy tissue particle specificity. This allowed for the detection of strong, tumour-localized porphyrin fluorescence, which was diminished when apoE3-devoid py-LN particles were administered. Furthermore, this selective uptake yielded cell-specific potent PDT sensitization in vitro, resulting in an 83% reduction in glioblastoma cell viability. These results highlight the promising capacity of pyE-LNs to target porphyrin delivery to glioblastoma tumours for theranostic applications.
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Affiliation(s)
- M A Rajora
- Princess Margaret Cancer Centre , University Health Network , 101 College Street , Toronto , Ontario M5G 1L7 , Canada . .,Institute of Biomaterials and Biomedical Engineering , University of Toronto , 164 College Street , Toronto , Ontario M5S 3G9 , Canada
| | - L Ding
- Princess Margaret Cancer Centre , University Health Network , 101 College Street , Toronto , Ontario M5G 1L7 , Canada .
| | - M Valic
- Princess Margaret Cancer Centre , University Health Network , 101 College Street , Toronto , Ontario M5G 1L7 , Canada . .,Institute of Biomaterials and Biomedical Engineering , University of Toronto , 164 College Street , Toronto , Ontario M5S 3G9 , Canada
| | - W Jiang
- Princess Margaret Cancer Centre , University Health Network , 101 College Street , Toronto , Ontario M5G 1L7 , Canada .
| | - M Overchuk
- Princess Margaret Cancer Centre , University Health Network , 101 College Street , Toronto , Ontario M5G 1L7 , Canada . .,Institute of Biomaterials and Biomedical Engineering , University of Toronto , 164 College Street , Toronto , Ontario M5S 3G9 , Canada
| | - J Chen
- Princess Margaret Cancer Centre , University Health Network , 101 College Street , Toronto , Ontario M5G 1L7 , Canada .
| | - G Zheng
- Princess Margaret Cancer Centre , University Health Network , 101 College Street , Toronto , Ontario M5G 1L7 , Canada . .,Institute of Biomaterials and Biomedical Engineering , University of Toronto , 164 College Street , Toronto , Ontario M5S 3G9 , Canada.,Department of Medical Biophysics , University of Toronto , 101 College Street , Toronto , Ontario M5G 1L7 , Canada
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11
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Itabe H, Yamaguchi T, Nimura S, Sasabe N. Perilipins: a diversity of intracellular lipid droplet proteins. Lipids Health Dis 2017; 16:83. [PMID: 28454542 PMCID: PMC5410086 DOI: 10.1186/s12944-017-0473-y] [Citation(s) in RCA: 188] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Accepted: 04/22/2017] [Indexed: 01/04/2023] Open
Abstract
Intracellular lipid droplets (LDs) are found in a wide variety of cell types and have been recognized as organelles with unique spherical structures. Although LDs are not stable lipid-depots, they are active sites of neutral lipid metabolism, and comprise neutral lipid or cholesterol cores surrounded by phospholipid monolayers containing specialized proteins. However, sizes and protein compositions vary between cell and tissue types. Proteins of the perilipin family have been associated with surfaces of LDs and all carry a conserved 11-mer repeat motif. Accumulating evidence indicates that all perilipins are involved in LD formation and that all play roles in LD function under differing conditions. In this brief review, we summarize current knowledge of the roles of perilipins and lipid metabolizing enzymes in a variety of mammalian cell types.
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Affiliation(s)
- Hiroyuki Itabe
- Division of Biological Chemistry, Department of Molecular Biology, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo, 142-8555, Japan.
| | - Tomohiro Yamaguchi
- Division of Biological Chemistry, Department of Molecular Biology, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo, 142-8555, Japan.,Present address: College of Pharmacy, Kinjo Gakuin University, 2-1723 Omori, Moriyaka-ku, Nagoya, 463-8521, Japan
| | - Satomi Nimura
- Division of Biological Chemistry, Department of Molecular Biology, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo, 142-8555, Japan.,Department of Hospital Pharmaceutics, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo, 142-8555, Japan
| | - Naoko Sasabe
- Division of Biological Chemistry, Department of Molecular Biology, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo, 142-8555, Japan
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12
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Fabilane CS, Nguyen PN, Hernandez RV, Nirudodhi S, Duong M, Maier CS, Narayanaswami V. Mechanism of Lipid Binding of Human Apolipoprotein E3 by Hydrogen/Deuterium Exchange/Mass Spectrometry and Fluorescence Polarization. Protein Pept Lett 2016; 23:404-13. [PMID: 26902251 DOI: 10.2174/0929866523666160223122257] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 02/18/2016] [Accepted: 02/19/2016] [Indexed: 11/22/2022]
Abstract
BACKGROUND Human apolipoprotein E3 (apoE3) is an exchangeable apolipoprotein that plays a critical role in maintaining plasma cholesterol/triglyceride homeostasis. The C-terminal (CT) domain of apoE3 (residues 201-299) is composed of amphipathic α-helices C1: W210-S223, C2: V236-E266, and C3: D271-W276, which play a dominant role in mediating high-affinity lipid binding. OBJECTIVE The objective is to understand the accessibility of the CT domain at the sub-domain level and the mechanistic details regarding lipid-binding interaction. METHODS Hydrogen-deuterium exchange coupled to mass spectrometry (HDX/MS) of recombinant wild type (WT) apoE(201-299), chemical-induced unfolding monitored as changes in fluorescence polarization (FP) of labeled apoE(201-299) bearing a probe at specified sites, and lipid binding studies were carried out. RESULTS HDX/MS revealed that residues towards the C-terminal end of the domain display significantly lower %D uptake compared to those towards the center, suggesting extensive protein-protein interaction in this segment. Functional assays showed that locking apoE(201-299) in an inter-molecular disulfide-bonded state at position 209, 223, 255, or 277 significantly decreases its ability to interact with lipids, especially when tethered towards the ends; this could be restored by reduction. Unfolding studies indicate that the C-terminal end offers less resistance to unfolding compared to the central portion of the domain. CONCLUSION Taken together, our data suggest that two dimers of CT domain are juxtaposed around helix C3 leading to apoE3 tetramerization, and that dissociation to monomeric units is a required step in lipid binding, with helix C3 likely seeking stability via lipid interaction prior to helices C1 or C2.
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Affiliation(s)
| | | | | | | | | | | | - Vasanthy Narayanaswami
- Department of Chemistry & Biochemistry, 1250 Bellflower Blvd, California State University Long Beach, Long Beach, CA 90840, USA.
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13
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Ganesh HV, Chow AM, Kerman K. Recent advances in biosensors for neurodegenerative disease detection. Trends Analyt Chem 2016. [DOI: 10.1016/j.trac.2016.02.012] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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14
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Kim SH, Adhikari BB, Cruz S, Schramm MP, Vinson JA, Narayanaswami V. Targeted intracellular delivery of resveratrol to glioblastoma cells using apolipoprotein E-containing reconstituted HDL as a nanovehicle. PLoS One 2015; 10:e0135130. [PMID: 26258481 PMCID: PMC4530947 DOI: 10.1371/journal.pone.0135130] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 07/18/2015] [Indexed: 11/23/2022] Open
Abstract
The objective of this study is to transport and deliver resveratrol to intracellular sites using apolipoprotein E3 (apoE3). Reconstituted high-density lipoprotein (rHDL) bearing resveratrol (rHDL/res) was prepared using phospholipids and the low-density lipoprotein receptor (LDLr)-binding domain of apoE3. Biophysical characterization revealed that resveratrol was partitioned into the phospholipid bilayer of discoidal rHDL/res particles (~19 nm diameter). Co-immunoprecipitation studies indicated that the LDLr-binding ability of apoE3 was retained. Cellular uptake of resveratrol to intracellular sites was evaluated in glioblastoma A-172 cells by direct fluorescence using chemically synthesized NBD-labeled resveratrol (res/NBD) embedded in rHDL/res. Competition and inhibition studies indicate that the uptake is by receptor mediated endocytosis via the LDLr, with co-localization of apoE3 and res/NBD in late endosomes/lysosomes. We propose that rHDL provides an ideal hydrophobic milieu to sequester resveratrol and that rHDL containing apoE3 serves as an effective “nanovehicle” to transport and deliver resveratrol to targeted intracellular sites.
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Affiliation(s)
- Sea H. Kim
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, United States of America
| | - Birendra Babu Adhikari
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, United States of America
| | - Siobanth Cruz
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, United States of America
| | - Michael P. Schramm
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, United States of America
| | - Joe A. Vinson
- Chemistry Department, Loyola Science Center, University of Scranton, Scranton, Pennsylvania, United States of America
| | - Vasanthy Narayanaswami
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, United States of America
- * E-mail:
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15
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Phillips MC. Apolipoprotein E isoforms and lipoprotein metabolism. IUBMB Life 2015; 66:616-23. [PMID: 25328986 DOI: 10.1002/iub.1314] [Citation(s) in RCA: 208] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Accepted: 09/09/2014] [Indexed: 11/09/2022]
Abstract
Apolipoprotein (apo) E is a 299-residue protein which functions as a key regulator of plasma lipid levels. Human apoE exists as three common isoforms and the parent form, apoE3, operates optimally in promoting clearance of triglyceride (TG)-rich lipoproteins and is associated with normal plasma lipid levels. This result occurs because apoE3 possesses both the requisite lipid-binding ability and affinity for the low density lipoprotein receptor (LDLR) to mediate appropriate lipolytic processing and endocytosis of TG-rich lipoprotein remnant particles. ApoE2 which differs from apoE3 by the single amino acid substitution Arg158Cys located near the LDLR recognition site exhibits impaired binding to the receptor and an inability to promote clearance of TG-rich lipoprotein remnant particles; this isoform is associated with Type-III hyperlipoproteinemia. ApoE4 which differs from apoE3 by the single amino acid substitution Cys112Arg is also associated with dyslipidemia although binding of this isoform to the LDLR is unaffected. The amino acid substitution affects the organization and stability of both the N-terminal helix bundle domain and separately folded C-terminal domain so that apoE4 has enhanced lipid binding ability. As a consequence, apoE4 binds better than apoE3 to the surface of very low density lipoprotein (VLDL) particles and impairs their lipolytic processing in the circulation so that apoE4 is associated with a more pro-atherogenic lipoprotein-cholesterol distribution (higher VLDL-cholesterol/high density lipoprotein-cholesterol ratio). This review summarizes current understanding of the structural differences between apoE2, apoE3, and apoE4, and the molecular mechanisms responsible for the alterations in lipoprotein metabolism resulting from this polymorphism of apoE. Detailed knowledge of how expression of structurally distinct apoE variants modifies lipoprotein metabolism provides a basis for developing ways to manipulate the functionality of apoE in vivo.
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Affiliation(s)
- Michael C Phillips
- Division of Translational Medicine and Human Genetics, Perelman School of Medicine at the University of Pennsylvania, 11-130 Translational Research Center, Philadelphia, PA, USA
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16
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Hauser PS, Ryan RO. Impact of apolipoprotein E on Alzheimer's disease. Curr Alzheimer Res 2014; 10:809-17. [PMID: 23919769 DOI: 10.2174/15672050113109990156] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Revised: 05/10/2013] [Accepted: 05/12/2013] [Indexed: 11/22/2022]
Abstract
A key feature of Alzheimer's disease (AD) is deposition of extracellular amyloid plaque comprised chiefly of the amyloid β (Aβ) peptide. Studies of Aβ have shown that it may be catabolized by proteolysis or cleared from brain via members of the low-density lipoprotein receptor family. Alternatively, Aβ can undergo a conformational transition from α-helix to β-sheet, a conformer that displays a propensity to self-associate, oligomerize and form fibrils. Furthermore, β- sheet conformers catalyze conversion of other α-helical Aβ peptides to β-sheet, feeding the oligomer and fibril assembly process. A factor that influences the fate of Aβ in the extracellular space is apolipoprotein (apo) E. Polymorphism at position 112 or 158 in apoE give rise to three major isoforms. One isoform in particular, apoE4 (Arg at 112 and 158), has generated considerable interest since the discovery that it is the major genetic risk factor for development of late onset AD. Despite this striking correlation, the molecular mechanism underlying apoE4's association with AD remains unclear. A tertiary structural feature distinguishing apoE4 from apoE2 and apoE3, termed domain interaction, is postulated to affect the conformation and orientation of its' two independently folded domains. This feature has the potential to influence apoE4's interaction with Aβ, its sensitivity to proteolysis or its lipid accrual and receptor binding activities. Thus, domain interaction may constitute the principal molecular feature of apoE4 that predisposes carriers to late onset AD. By understanding the contribution of apoE4 to AD at the molecular level new therapeutic or prevention strategies will emerge.
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Affiliation(s)
- Paul S Hauser
- Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr. Way, Oakland, CA 94609 USA.
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17
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Bains GK, Kim SH, Sorin EJ, Narayanaswami V. The extent of pyrene excimer fluorescence emission is a reflector of distance and flexibility: analysis of the segment linking the LDL receptor-binding and tetramerization domains of apolipoprotein E3. Biochemistry 2012; 51:6207-19. [PMID: 22779734 DOI: 10.1021/bi3005285] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Pyrene is a spatially sensitive probe that displays an ensemble of monomeric fluorescence emission peaks (375-405 nm) and an additional band (called excimer) at ~460 nm when two fluorophores are spatially proximal. We examined if there is a correlation between distance between two pyrenes on an α-helical structure and excimer/monomer (e/m) ratio. Using structure-guided design, pyrene maleimide was attached to pairs of Cys residues separated by ~5 Å increments on helix 2 of the N-terminal domain of apolipoprotein E3 (apoE3). Fluorescence spectral analysis revealed an intense excimer band when the probes were ~5 Å from each other with an e/m ratio of ~3.0, which decreased to ~1.0 at 20 Å. An inverse correlation between e/m ratio and the distance between pyrenes was observed, with the probe and helix flexibility also contributing to the extent of excimer formation. We verified this approach by estimating the distance between T57C and C112 (located on helices 2 and 3, respectively) to be 5.2 Å (4.9 Å from NMR and 5.7 Å from the X-ray structure). Excimer formation was also noted to a significant extent with probes located in the linker segment, suggesting spatial proximity (10-15 Å) to corresponding sites on neighboring molecules in the tetrameric configuration of apoE. We infer that oligomerization via the C-terminal domain juxtaposes the linker segments from neighboring apoE molecules. This study offers new insights into the conformation of tetrameric apoE and presents the use of pyrene as a powerful probe for studying protein spatial organization.
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Affiliation(s)
- Gursharan K Bains
- Department of Chemistry and Biochemistry, 1250 Bellflower Boulevard, California State University Long Beach, Long Beach, CA 90840, USA
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18
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Bains G, Patel AB, Narayanaswami V. Pyrene: a probe to study protein conformation and conformational changes. Molecules 2011; 16:7909-35. [PMID: 22143550 PMCID: PMC6264589 DOI: 10.3390/molecules16097909] [Citation(s) in RCA: 190] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Revised: 09/04/2011] [Accepted: 09/06/2011] [Indexed: 11/18/2022] Open
Abstract
The review focuses on the unique spectral features of pyrene that can be utilized to investigate protein structure and conformation. Pyrene is a fluorescent probe that can be attached covalently to protein side chains, such as sulfhydryl groups. The spectral features of pyrene are exquisitely sensitive to the microenvironment of the probe: it exhibits an ensemble of monomer fluorescence emission peaks that report on the polarity of the probe microenvironment, and an additional band at longer wavelengths, the appearance of which reflects the presence of another pyrene molecule in spatial proximity (~10 Å). Its high extinction coefficient allows us to study labeled proteins in solution at physiologically relevant concentrations. The environmentally- and spatially-sensitive features of pyrene allow monitoring protein conformation, conformational changes, protein folding and unfolding, protein-protein, protein-lipid and protein-membrane interactions.
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Affiliation(s)
- Gursharan Bains
- Department of Chemistry and Biochemistry, 1250 Bellflower Boulevard, California State University Long Beach, Long Beach, CA 90840, USA
| | - Arti B. Patel
- Department of Chemistry and Biochemistry, 1250 Bellflower Boulevard, California State University Long Beach, Long Beach, CA 90840, USA
| | - Vasanthy Narayanaswami
- Department of Chemistry and Biochemistry, 1250 Bellflower Boulevard, California State University Long Beach, Long Beach, CA 90840, USA
- Children’s Hospital Oakland Research Institute, 5700 Martin Luther King Jr. Way, Oakland, CA 94609, USA
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-562-985-4953; Fax: +1-562-985-8557
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Petrlova J, Hong HS, Bricarello DA, Harishchandra G, Lorigan GA, Jin LW, Voss JC. A differential association of Apolipoprotein E isoforms with the amyloid-β oligomer in solution. Proteins 2011; 79:402-16. [PMID: 21069870 DOI: 10.1002/prot.22891] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The molecular pathogenesis of disorders arising from protein misfolding and aggregation is difficult to elucidate, involving a complex ensemble of intermediates, whose toxicity depends upon their state of progression along distinct processing pathways. To address the complex misfolding and aggregation that initiates the toxic cascade resulting in Alzheimer's disease (AD), we have developed a 2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid spin-labeled amyloid-β (Aβ) peptide to observe its isoform-dependent interaction with the apoE protein. Although most individuals carry the E3 isoform of apoE, ∼15% of humans carry the E4 isoform, which is recognized as the most significant genetic determinant for Alzheimer's. ApoE is consistently associated with the amyloid plaque marker for AD. A vital question centers on the influence of the two predominant isoforms, E3 and E4, on Aβ peptide processing and hence Aβ toxicity. We used electron paramagnetic resonance (EPR) spectroscopy of incorporated spin labels to investigate the interaction of apoE with the toxic oligomeric species of Aβ in solution. EPR spectra of the spin-labeled side chain report on side chain and backbone dynamics as well as the spatial proximity of spins in an assembly. Our results indicate oligomer binding involves the C-terminal domain of apoE, with apoE3 reporting a much greater response through this conformational marker. Coupled with SPR binding measurements, apoE3 displays a higher affinity and capacity for the toxic Aβ oligomer. These findings support the hypothesis that apoE polymorphism and Alzheimer's risk can largely be attributed to the reduced ability of apoE4 to function as a clearance vehicle for the toxic form of Aβ.
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Affiliation(s)
- Jitka Petrlova
- Department of Biochemistry and Molecular Medicine, University of California Davis, California, USA
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20
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Hauser PS, Narayanaswami V, Ryan RO. Apolipoprotein E: from lipid transport to neurobiology. Prog Lipid Res 2010; 50:62-74. [PMID: 20854843 DOI: 10.1016/j.plipres.2010.09.001] [Citation(s) in RCA: 222] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Revised: 09/04/2010] [Accepted: 09/12/2010] [Indexed: 12/17/2022]
Abstract
Apolipoprotein (apo) E has a storied history as a lipid transport protein. The integral association between cholesterol homeostasis and lipoprotein clearance from circulation are intimately related to apoE's function as a ligand for cell-surface receptors of the low-density lipoprotein receptor family. The receptor binding properties of apoE are strongly influenced by isoform specific amino acid differences as well as the lipidation state of the protein. As understanding of apoE as a structural component of circulating plasma lipoproteins has evolved, exciting developments in neurobiology have revitalized interest in apoE. The strong and enduring correlation between the apoE4 isoform and age of onset and increased risk of Alzheimer's disease has catapulted apoE to the forefront of neurobiology. Using genetic tools generated for study of apoE lipoprotein metabolism, transgenic "knock-in" and gene-disrupted mice are now favored models for study of its role in a variety of neurodegenerative diseases. Key structural knowledge of apoE and isoform-specific differences is driving research activity designed to elucidate how a single amino acid change can manifest such profoundly significant pathological consequences. This review describes apoE through a lens of structure-based knowledge that leads to hypotheses that attempt to explain the functions of apoE and isoform-specific effects relating to disease mechanism.
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Affiliation(s)
- Paul S Hauser
- Center for Prevention of Obesity, Cardiovascular Disease and Diabetes, Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr. Way, Oakland, CA 94609, USA
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21
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Khumsupan P, Ramirez R, Khumsupan D, Narayanaswami V. Apolipoprotein E LDL receptor-binding domain-containing high-density lipoprotein: a nanovehicle to transport curcumin, an antioxidant and anti-amyloid bioflavonoid. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:352-9. [PMID: 20851099 DOI: 10.1016/j.bbamem.2010.09.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Revised: 09/10/2010] [Accepted: 09/13/2010] [Indexed: 01/21/2023]
Abstract
Curcumin is an antioxidant and anti-inflammatory bioflavonoid that has been recently identified as an anti-amyloid agent as well. To make it more available in its potent form as a potential amyloid disaggregation agent, we employed high-density lipoproteins (HDL), which are lipid-protein complexes that transport plasma cholesterol, to transport curcumin. The objective of this study was to employ reconstituted HDL containing human apoE3 N-terminal (NT) domain, as a vehicle to transport curcumin. The NT domain serves as a ligand to mediate binding and uptake of lipoprotein complexes via the low-density lipoprotein receptor (LDLr) family of proteins located at the cell surface. Reconstituted HDL was prepared with phospholipids and recombinant apoE3-NT domain in the absence or presence of curcumin. Non-denaturing polyacrylamide gel electrophoresis indicated that the molecular mass and Stokes' diameter of HDL bearing curcumin were ~670kDa and ~17nm, respectively, while electron microscopy revealed the presence of discoidal particles. Fluorescence emission spectra of HDL bearing (the intrinsically fluorescent) curcumin indicated that the wavelength of maximal fluorescence emission (λ(max)) of curcumin was ~495nm, which is highly blue-shifted compared to λ(max) of curcumin in solvents of varying polarity (λ(max) ranging from 515-575nm) or in aqueous buffers. In addition, an enormous enhancement in fluorescence emission intensity was noted in curcumin-containing HDL compared to curcumin in aqueous buffers. Curcumin fluorescence emission was quenched to a significant extent by lipid-based quenchers but not by aqueous quenchers. These observations indicate that curcumin has partitioned efficiently into the hydrophobic milieu of the phospholipid bilayer of HDL. Functional assays indicated that the LDLr-binding ability of curcumin-containing HDL with apoE3-NT is similar to that of HDL without curcumin. Taken together, we report that apoE-containing HDL has a tremendous potential as a 'nanovehicle' with a homing device to transport curcumin to target sites.
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Affiliation(s)
- Panupon Khumsupan
- Department of Chemistry and Biochemistry, 1250 Bellflower Boulevard, California State University Long Beach, Long Beach, CA 90840, USA
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22
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Guttman M, Prieto JH, Croy JE, Komives EA. Decoding of lipoprotein-receptor interactions: properties of ligand binding modules governing interactions with apolipoprotein E. Biochemistry 2010; 49:1207-16. [PMID: 20030366 DOI: 10.1021/bi9017208] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Clusters of complement-type ligand binding repeats in the LDL receptor family are thought to mediate the interactions between these receptors and their various ligands. Apolipoprotein E, a key ligand for cholesterol homeostasis, has been shown to interact with LDLR, LRP, and VLDLR, through these clusters. LDLR and VLDLR each contain a single ligand binding repeat cluster, whereas LRP contains three large clusters of ligand binding repeats, each with ligand binding functions. We show that within sLRP3 the three-repeat subcluster CR16-18 recapitulated ligand binding to the isolated receptor binding portion of ApoE (residues 130-149). Binding experiments with LA3-5 of LDLR and CR16-18 showed that a conserved W25/D30 pair appears to be critical for high-affinity binding to ApoE(130-149). The triple repeat LA3-5 showed the expected interaction with ApoE(1-191).DMPC, but surprisingly CR16-18 did not interact with this form of ApoE. To understand these differences in ApoE binding affinity, we introduced mutations of conserved residues from LA5 into CR18 and produced a CR16-18 variant capable of binding ApoE(1-191).DMPC. This change cannot fully be accounted for by the interaction with the proposed ApoE receptor binding region; therefore, we speculate that LA5 is recognizing a distinct epitope on ApoE that may only exist in the lipid-bound form. The combination of avidity effects with this distinct recognition process likely governs the ApoE-LDL receptor interaction.
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Affiliation(s)
- Miklos Guttman
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0378, USA
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23
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Guttman M, Prieto JH, Handel TM, Domaille PJ, Komives EA. Structure of the minimal interface between ApoE and LRP. J Mol Biol 2010; 398:306-19. [PMID: 20303980 DOI: 10.1016/j.jmb.2010.03.022] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2010] [Revised: 03/10/2010] [Accepted: 03/11/2010] [Indexed: 11/24/2022]
Abstract
Clusters of complement-type ligand-binding repeats (CRs) in the low-density lipoprotein receptor (LDLR) family are thought to mediate the interactions with their various ligands. Apolipoprotein E (ApoE), a key ligand for cholesterol homeostasis, has been shown to interact with LDLR-related protein 1 (LRP) through these clusters. The segment comprising the receptor-binding portion of ApoE (residues 130-149) has been found to have a weak affinity for isolated CRs. We have fused this region of ApoE to a high-affinity CR from LRP (CR17) for structural elucidation of the complex. The interface reveals a motif that has previously been observed in CR domains with other binding partners, but with several novel features. Comparison to free CR17 reveals that very few structural changes result from this binding event, but significant changes in intrinsic dynamics are observed upon binding. NMR perturbation experiments suggest that this interface may be similar to several other ligand interactions with LDLRs.
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Affiliation(s)
- Miklos Guttman
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0378, USA
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24
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Tetali SD, Budamagunta MS, Simion C, den Hartigh LJ, Kálai T, Hideg K, Hatters DM, Weisgraber KH, Voss JC, Rutledge JC. VLDL lipolysis products increase VLDL fluidity and convert apolipoprotein E4 into a more expanded conformation. J Lipid Res 2009; 51:1273-83. [PMID: 19965582 DOI: 10.1194/jlr.m000406] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Our previous work indicated that apolipoprotein (apo) E4 assumes a more expanded conformation in the postprandial period. The postprandial state is characterized by increased VLDL lipolysis. In this article, we tested the hypothesis that VLDL lipolysis products increase VLDL particle fluidity, which mediates expansion of apoE4 on the VLDL particle. Plasma from healthy subjects was collected before and after a moderately high-fat meal and incubated with nitroxyl-spin labeled apoE. ApoE conformation was examined by electron paramagnetic resonance spectroscopy using targeted spin probes on cysteines introduced in the N-terminal (S76C) and C-terminal (A241C) domains. Further, we synthesized a novel nitroxyl spin-labeled cholesterol analog, which gave insight into lipoprotein particle fluidity. Our data revealed that the order of lipoprotein fluidity was HDL approximately LDL<VLDL<VLDL+lipoprotein lipase. Moreover, the conformation of apoE4 depended on the lipoprotein fraction: VLDL-associated apoE4 had a more linear conformation than apoE4 associated with LDL or HDL. Further, by changing VLDL fluidity, VLDL lipolysis products significantly altered apoE4 into a more expanded conformation. Our studies indicate that after every meal, VLDL fluidity is increased causing apoE4 associated with VLDL to assume a more expanded conformation, potentially enhancing the pathogenicity of apoE4 in vascular tissue.
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Affiliation(s)
- Sarada D Tetali
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad 500 046, India.
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25
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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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26
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Sivashanmugam A, Wang J. A unified scheme for initiation and conformational adaptation of human apolipoprotein E N-terminal domain upon lipoprotein binding and for receptor binding activity. J Biol Chem 2009; 284:14657-66. [PMID: 19307174 PMCID: PMC2682913 DOI: 10.1074/jbc.m901012200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We report here a high-resolution NMR structure of the complete receptor-binding domain of human apolipoprotein E3 (apoE3-NT). Similar to the crystal structure of apoE-NT, the NMR structure displayed an elongated four-helix bundle. However, additional unique structural features were also observed. The segments in the N and C termini, which were missing in the crystal structure, formed alpha-helices having extensive tertiary contacts with the bundle, which oriented these short helices at specific positions for receptor binding activity. Several buried hydrophilic residues observed in the bundle were located strategically between helices 1 and 2 and between helices 3 and 4, significantly destabilizing these helix-helix interfaces. In addition, these buried hydrophilic residues formed buried H-bonds, which may play a key role in specific lipid-free helix bundle recovery. A short helix, nHelix C, was fully solvent-exposed and nearly perpendicular to the bundle. This short helix likely plays a critical role in initiating protein-lipid interaction, causing a preferred conformational adaptation of the bundle at the weaker helix-helix interfaces. This produces an open conformation with two lobes of helices, helices 1 and 4 and helices 2 and 3, which may be the competent conformation for receptor binding activity. Thus, the NMR structure suggests a unified scheme for the initiation and helix bundle opening of apoE-NT upon lipoprotein-binding and for receptor binding activity.
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Affiliation(s)
- Arun Sivashanmugam
- Department of Biochemistry and Molecular Biology, School of Medicine, Wayne State University, Detroit, Michigan 48201, USA
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27
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Blacklow SC. Versatility in ligand recognition by LDL receptor family proteins: advances and frontiers. Curr Opin Struct Biol 2007; 17:419-26. [PMID: 17870468 PMCID: PMC2766800 DOI: 10.1016/j.sbi.2007.08.017] [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] [Received: 04/30/2007] [Revised: 08/16/2007] [Accepted: 08/22/2007] [Indexed: 01/07/2023]
Abstract
Proteins of the low-density lipoprotein receptor family transport cholesterol-carrying particles into cells, clear protease-inhibitor complexes from the circulation, participate in biological signaling cascades, and even serve as viral receptors. These receptors utilize clusters of cysteine-rich LDL receptor type-A (LA) modules to bind many of their ligands. Recent structures show that these modules typically exhibit a characteristic binding mode to recognize their partners, relying primarily on electrostatic complementarity and avidity effects. The dominant contribution of electrostatic interactions with small interface areas in these complexes allows binding to be regulated by changes in pH via at least two distinct mechanisms. The structure of the subtilisin/kexin family protease PCSK9, a newly identified molecular partner of the LDLR also implicated in LDL-cholesterol homeostasis, also raises the possibility that the LDLR and its related family members may employ other strategies for pH-sensitive binding that have yet to be uncovered.
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Affiliation(s)
- Stephen C Blacklow
- Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
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28
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Tamamizu-Kato S, Wong JY, Jairam V, Uchida K, Raussens V, Kato H, Ruysschaert JM, Narayanaswami V. Modification by acrolein, a component of tobacco smoke and age-related oxidative stress, mediates functional impairment of human apolipoprotein E. Biochemistry 2007; 46:8392-400. [PMID: 17580963 PMCID: PMC2556514 DOI: 10.1021/bi700289k] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Oxidative damage to proteins such as apolipoprotein B-100 increases the atherogenicity of low-density lipoproteins (LDL). However, little is known about the potential oxidative damage to apolipoprotein E (apoE), an exchangeable antiatherogenic apolipoprotein. ApoE plays an integral role in lipoprotein metabolism by regulating the plasma cholesterol and triglyceride levels. Hepatic uptake of lipoproteins is facilitated by apoE's ability to bind with cell surface heparan sulfate proteoglycans and to lipoprotein receptors via basic residues in its 22 kDa N-terminal domain (NT). We investigated the effect of acrolein, an aldehydic product of endogenous lipid peroxidation and a tobacco smoke component, on the conformation and function of recombinant human apoE3-NT. Acrolein caused oxidative modification of apoE3-NT as detected by Western blot with acrolein-lysine-specific antibodies, and tertiary conformational alterations. Acrolein modification impairs the ability of apoE3-NT to interact with heparin and the LDL receptor. Furthermore, acrolein-modified apoE3-NT displayed a 5-fold decrease in its ability to interact with lipid surfaces. Our data indicate that acrolein disrupts the functional integrity of apoE3, which likely interferes with its role in regulating plasma cholesterol homeostasis. These observations have implications regarding the role of apoE in the pathogenesis of smoking- and oxidative stress-mediated cardiovascular and cerebrovascular diseases.
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Affiliation(s)
- Shiori Tamamizu-Kato
- Center for the Prevention of Obesity, Cardiovascular Disease and Diabetes, Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr. Way, Oakland, CA 94609
| | - Jason Yiu Wong
- Center for the Prevention of Obesity, Cardiovascular Disease and Diabetes, Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr. Way, Oakland, CA 94609
| | - Vikram Jairam
- Center for the Prevention of Obesity, Cardiovascular Disease and Diabetes, Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr. Way, Oakland, CA 94609
| | - Koji Uchida
- Graduate School of Agricultural Sciences, Nagoya University, Nagoya, Japan
| | - Vincent Raussens
- Center for Structural Biology and Bioinformatics, Structure and Function of Biological Membranes, Université Libre de Bruxelles, CP-206/2, bd. du Triomphe, B-1050 Brussels, Belgium
| | - Hiroyuki Kato
- Center for the Prevention of Obesity, Cardiovascular Disease and Diabetes, Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr. Way, Oakland, CA 94609
| | - Jean-Marie Ruysschaert
- Center for Structural Biology and Bioinformatics, Structure and Function of Biological Membranes, Université Libre de Bruxelles, CP-206/2, bd. du Triomphe, B-1050 Brussels, Belgium
| | - Vasanthy Narayanaswami
- Center for the Prevention of Obesity, Cardiovascular Disease and Diabetes, Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr. Way, Oakland, CA 94609
- Address correspondence to: Vasanthy Narayanaswami, Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr. Way, Oakland, CA 94609, USA, Tel: (510) 428 3885 ex: 2965, Fax: (510) 450 7910,
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