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Mohamed Yusof NIS, Mohd Fauzi F. Nature's Toolbox for Alzheimer's Disease: A Review on the Potential of Natural Products as Alzheimer's Disease Drugs. Neurochem Int 2024; 176:105738. [PMID: 38616012 DOI: 10.1016/j.neuint.2024.105738] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2024] [Revised: 03/18/2024] [Accepted: 04/06/2024] [Indexed: 04/16/2024]
Abstract
Numerous clinical trials involving natural products have been conducted to observe cognitive performances and biomarkers in Alzheimer's Disease (AD) patients. However, to date, no natural-based drugs have been approved by the FDA as treatments for AD. In this review, natural product-based compounds that were tested in clinical trials from 2011 to 2023, registered at www.clinicaltrials.gov were reviewed. Thirteen compounds, encompassing 7 different mechanisms of action were covered. Several observations were deduced, which are: i) several compounds showed cognitive improvement, but these improvements may not extend to AD, ii) compounds that are endogenous to the human body showed better outcomes, and iii) Docosahexaenoic acid (DHA) and cerebrolysin had the most potential as AD drugs among the 13 compounds. Based on the current findings, natural products may be more suitable as a supplement than AD drugs in most cases. However, the studies covered here were conducted in a relatively short amount of time, where compounds acting on AD pathways may take time to show any effect. Given the diverse pathways that these natural products are involved in, they may potentially produce synergistic effects that would be beneficial in treating AD. Additionally, natural products benefit from both physicochemical properties being in more favorable ranges and active transport playing a more significant role than it does for synthetic compounds.
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Affiliation(s)
| | - Fazlin Mohd Fauzi
- Faculty of Pharmacy, Universiti Teknologi MARA Selangor, Puncak Alam Campus, 42 300 Bandar Puncak Alam, Selangor, Malaysia; Center for Drug Discovery Research, Faculty of Pharmacy, Universiti Teknologi MARA Selangor, Puncak Alam Campus, 42 300 Bandar Puncak Alam, Selangor, Malaysia.
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Ganesan K, Rentsch P, Langdon A, Milham LT, Vissel B. Modeling sporadic Alzheimer's disease in mice by combining Apolipoprotein E4 risk gene with environmental risk factors. Front Aging Neurosci 2024; 16:1357405. [PMID: 38476659 PMCID: PMC10927790 DOI: 10.3389/fnagi.2024.1357405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Accepted: 02/12/2024] [Indexed: 03/14/2024] Open
Abstract
Introduction Developing effective treatment for Alzheimer's disease (AD) remains a challenge. This can be partially attributed to the fact that the mouse models used in preclinical research largely replicate familial form of AD, while majority of human cases are sporadic; both forms differ widely in the onset and origin of pathology, therefore requiring specific/targeted treatments. Methods In this study, we aimed to model sporadic AD in mice by combining two of the many risk factors that are strongly implicated in AD: ApoE4, a major genetic risk factor, together with an inflammatory stimuli. Accordingly, we subjected ApoE4 knock in (KI) mice, expressing humanized ApoE4, to low doses of Lipopolysaccharide (LPS) injections (i.p, weekly, for 4 months). Results We assessed these animals for behavioral impairments at 6 months of age using Open Field, Y-maze, and Barnes Maze Test. LPS induced hypoactivity was observed in the Open Field and Y-maze test, whereas spatial learning and memory was intact. We then quantified differences in dendritic spine density, which is a strong correlate of AD. ApoE4KI mice showed a significant reduction in the number of spines after treatment with LPS, whereas there were no obvious differences in the total number of microglia and astrocytes. Discussion To conclude, in the current study the APoEe4 risk gene increases the vulnerability of hippocampal neurons to inflammation induced spine loss, laying a foundation for an early sporadic AD mouse model.
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Affiliation(s)
- Kiruthika Ganesan
- School of Life Sciences, Faculty of Science, University of Technology Sydney, Sydney, NSW, Australia
| | - Peggy Rentsch
- Centre for Neuroscience and Regenerative Medicine, St. Vincent’s Centre for Applied Medical Research, St Vincent’s Hospital, Sydney, NSW, Australia
- UNSW St. Vincent’s Clinical School, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
| | - Alexander Langdon
- School of Life Sciences, Faculty of Science, University of Technology Sydney, Sydney, NSW, Australia
| | - Luke T. Milham
- Centre for Neuroscience and Regenerative Medicine, St. Vincent’s Centre for Applied Medical Research, St Vincent’s Hospital, Sydney, NSW, Australia
- UNSW St. Vincent’s Clinical School, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
| | - Bryce Vissel
- Centre for Neuroscience and Regenerative Medicine, St. Vincent’s Centre for Applied Medical Research, St Vincent’s Hospital, Sydney, NSW, Australia
- UNSW St. Vincent’s Clinical School, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
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3
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Valencia-Olvera AC, Balu D, Faulk N, Amiridis A, Wang Y, Pham C, Avila-Munoz E, York JM, Thatcher GRJ, LaDu MJ. Inhibition of ACAT as a Therapeutic Target for Alzheimer's Disease Is Independent of ApoE4 Lipidation. Neurotherapeutics 2023; 20:1120-1137. [PMID: 37157042 PMCID: PMC10457278 DOI: 10.1007/s13311-023-01375-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/20/2023] [Indexed: 05/10/2023] Open
Abstract
APOE4, encoding apolipoprotein E4 (apoE4), is the greatest genetic risk factor for Alzheimer's disease (AD), compared to the common APOE3. While the mechanism(s) underlying APOE4-induced AD risk remains unclear, increasing the lipidation of apoE4 is an important therapeutic target as apoE4-lipoproteins are poorly lipidated compared to apoE3-lipoproteins. ACAT (acyl-CoA: cholesterol-acyltransferase) catalyzes the formation of intracellular cholesteryl-ester droplets, reducing the intracellular free cholesterol (FC) pool. Thus, inhibiting ACAT increases the FC pool and facilitates lipid secretion to extracellular apoE-containing lipoproteins. Previous studies using commercial ACAT inhibitors, including avasimibe (AVAS), as well as ACAT-knock out (KO) mice, exhibit reduced AD-like pathology and amyloid precursor protein (APP) processing in familial AD (FAD)-transgenic (Tg) mice. However, the effects of AVAS with human apoE4 remain unknown. In vitro, AVAS induced apoE efflux at concentrations of AVAS measured in the brains of treated mice. AVAS treatment of male E4FAD-Tg mice (5xFAD+/-APOE4+/+) at 6-8 months had no effect on plasma cholesterol levels or distribution, the original mechanism for AVAS treatment of CVD. In the CNS, AVAS reduced intracellular lipid droplets, indirectly demonstrating target engagement. Surrogate efficacy was demonstrated by an increase in Morris water maze measures of memory and postsynaptic protein levels. Amyloid-beta peptide (Aβ) solubility/deposition and neuroinflammation were reduced, critical components of APOE4-modulated pathology. However, there was no increase in apoE4 levels or apoE4 lipidation, while amyloidogenic and non-amyloidogenic processing of APP were significantly reduced. This suggests that the AVAS-induced reduction in Aβ via reduced APP processing was sufficient to reduce AD pathology, as apoE4-lipoproteins remained poorly lipidated.
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Affiliation(s)
- Ana C. Valencia-Olvera
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL 60612 USA
| | - Deebika Balu
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL 60612 USA
| | - Naomi Faulk
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL 60612 USA
| | | | - Yueting Wang
- Department of Pharmaceutical Sciences, University of Illinois at Chicago, Chicago, IL 60612 USA
- Present Address: AbbVie Inc., 1 N. Waukegan Road, North Chicago, IL 60064 USA
| | - Christine Pham
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL 60612 USA
| | - Eva Avila-Munoz
- Syneos Health, Av. Gustavo Baz 309, La Loma, Tlalnepantla de Baz, 54060 Mexico
| | - Jason M. York
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL 60612 USA
| | - Gregory R. J. Thatcher
- Department of Pharmacology & Toxicology, University of Arizona, 1703 E Mabel St., Tucson, AZ 85721 USA
| | - Mary Jo LaDu
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL 60612 USA
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4
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Larsen AH, Johansen NT, Gajhede M, Arleth L, Midtgaard SR. Lipid-bound ApoE3 self-assemble into elliptical disc-shaped particles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1863:183495. [PMID: 33189719 DOI: 10.1016/j.bbamem.2020.183495] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 10/14/2020] [Accepted: 10/26/2020] [Indexed: 11/29/2022]
Abstract
Apolipoproteins are vital to lipid metabolism and cholesterol transport in the human body. Here we present a structural study of the lipid-bound particles formed by ApoE3 in a full-length and a truncated version. The particles are formed with, respectively, POPC and DMPC and investigated by small-angle X-ray scattering and negative stain electron microscopy. We find that lipid-bound ApoE3 particles are elliptical, disc-shaped particles composed of a central lipid bilayer encircled by two amphipathic ApoE3 proteins. We went on to investigate a truncated form of ApoE3 containing only residue 80 to 255 (ApoE380-255), which is the central helical repeat segment of ApoE3. The lipid-bound ApoE380-255 particles are found to have the same morphology as the particles with full-length ApoE3. However, they are larger, and form more heterogeneous discoidal structures with four proteins per particle. This behavior is in contrast to ApoA1 where the highly similar helical repeat domain determines the size and stoichiometry of the formed particles both in the case of full-length and truncated ApoA1. Our data hence points towards different mechanisms for lipid bilayer structural modulation by ApoA1 and ApoE3 due to different roles of the non-repeat segments.
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Affiliation(s)
- Andreas Haahr Larsen
- University of Copenhagen, Niels Bohr Institute, Copenhagen, Denmark; University of Oxford, Department of Biochemistry, Oxford, United Kingdom.
| | | | - Michael Gajhede
- University of Copenhagen, Department of Drug Design and Pharmacology, Copenhagen, Denmark
| | - Lise Arleth
- University of Copenhagen, Niels Bohr Institute, Copenhagen, Denmark.
| | - Søren Roi Midtgaard
- University of Copenhagen, Niels Bohr Institute, Copenhagen, Denmark; Boston University School of Medicine, Department of Physiology and Biophysics, Boston, USA
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5
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Gamache J, Yun Y, Chiba-Falek O. Sex-dependent effect of APOE on Alzheimer's disease and other age-related neurodegenerative disorders. Dis Model Mech 2020; 13:dmm045211. [PMID: 32859588 PMCID: PMC7473656 DOI: 10.1242/dmm.045211] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The importance of apolipoprotein E (APOE) in late-onset Alzheimer's disease (LOAD) has been firmly established, but the mechanisms through which it exerts its pathogenic effects remain elusive. In addition, the sex-dependent effects of APOE on LOAD risk and endophenotypes have yet to be explained. In this Review, we revisit the different aspects of APOE involvement in neurodegeneration and neurological diseases, with particular attention to sex differences in the contribution of APOE to LOAD susceptibility. We discuss the role of APOE in a broader range of age-related neurodegenerative diseases, and summarize the biological factors linking APOE to sex hormones, drawing on supportive findings from rodent models to identify major mechanistic themes underlying the exacerbation of LOAD-associated neurodegeneration and pathology in the female brain. Additionally, we list sex-by-genotype interactions identified across neurodegenerative diseases, proposing APOE variants as a shared etiology for sex differences in the manifestation of these diseases. Finally, we present recent advancements in 'omics' technologies, which provide a new platform for more in-depth investigations of how dysregulation of this gene affects the development and progression of neurodegenerative diseases. Collectively, the evidence summarized in this Review highlights the interplay between APOE and sex as a key factor in the etiology of LOAD and other age-related neurodegenerative diseases. We emphasize the importance of careful examination of sex as a contributing factor in studying the underpinning genetics of neurodegenerative diseases in general, but particularly for LOAD.
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Affiliation(s)
- Julia Gamache
- Division of Translational Brain Sciences, Department of Neurology, Duke University Medical Center, Durham, NC 27710, USA
- Center for Genomic and Computational Biology, Duke University Medical Center, Durham, NC 27708, USA
| | - Young Yun
- Division of Translational Brain Sciences, Department of Neurology, Duke University Medical Center, Durham, NC 27710, USA
- Center for Genomic and Computational Biology, Duke University Medical Center, Durham, NC 27708, USA
| | - Ornit Chiba-Falek
- Division of Translational Brain Sciences, Department of Neurology, Duke University Medical Center, Durham, NC 27710, USA
- Center for Genomic and Computational Biology, Duke University Medical Center, Durham, NC 27708, USA
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Torres ERS, Weber Boutros S, Meshul CK, Raber J. ApoE isoform-specific differences in behavior and cognition associated with subchronic MPTP exposure. ACTA ACUST UNITED AC 2020; 27:372-379. [PMID: 32817303 PMCID: PMC7433653 DOI: 10.1101/lm.052126.120] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 07/07/2020] [Indexed: 12/25/2022]
Abstract
Parkinson's disease (PD) is characterized clinically by progressive motor dysfunction; overt parkinsonism is often preceded by prodromal symptoms including disturbances in the sleep–wake cycle. Up to 80% of patients with PD also develop dementia. In humans, there are three major apolipoprotein E isoforms: E2, E3, and E4. Increased rate of dementia in PD may be associated with E4 isoform. To better understand prodromal changes associated with E4, we exposed young (3–5 mo) male and female mice expressing E3 or E4 via targeted replacement to a subchronic dosage of the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). We hypothesized that E4 mice would be more susceptible to MPTP-related behavioral and cognitive changes. MPTP-treated E4 mice explored novel objects longer than genotype-matched saline-treated mice. In contrast, saline-treated E3 mice preferentially explored the novel object whereas MPTP-treated E3 mice did not and showed impaired object recognition. MPTP treatment altered swim speed of E4, but not E3, mice in the water maze compared to controls. Thus, E4 carriage may influence the preclinical symptoms associated with PD. Increased efforts are warranted to study early time points in this disease model.
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Affiliation(s)
- Eileen Ruth S Torres
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, 97239 Oregon, USA
| | - Sydney Weber Boutros
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, 97239 Oregon, USA
| | - Charles K Meshul
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, 97239 Oregon, USA.,Portland VA Medical Center, Portland, 97239 Oregon, USA
| | - Jacob Raber
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, 97239 Oregon, USA.,Departments of Neurology and Radiation Medicine and Division of Neuroscience, ONPRC, Oregon Health and Science University, Portland, Oregon 97239, USA
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Lewandowski CT, Maldonado Weng J, LaDu MJ. Alzheimer's disease pathology in APOE transgenic mouse models: The Who, What, When, Where, Why, and How. Neurobiol Dis 2020; 139:104811. [PMID: 32087290 DOI: 10.1016/j.nbd.2020.104811] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 02/01/2020] [Accepted: 02/18/2020] [Indexed: 02/07/2023] Open
Abstract
The focus on amyloid plaques and neurofibrillary tangles has yielded no Alzheimer's disease (AD) modifying treatments in the past several decades, despite successful studies in preclinical mouse models. This inconsistency has caused a renewed focus on improving the fidelity and reliability of AD mouse models, with disparate views on how this improvement can be accomplished. However, the interactive effects of the universal biological variables of AD, which include age, APOE genotype, and sex, are often overlooked. Age is the greatest risk factor for AD, while the ε4 allele of the human APOE gene, encoding apolipoprotein E, is the greatest genetic risk factor. Sex is the final universal biological variable of AD, as females develop AD at almost twice the rate of males and, importantly, female sex exacerbates the effects of APOE4 on AD risk and rate of cognitive decline. Therefore, this review evaluates the importance of context for understanding the role of APOE in preclinical mouse models. Specifically, we detail how human AD pathology is mirrored in current transgenic mouse models ("What") and describe the critical need for introducing human APOE into these mouse models ("Who"). We next outline different methods for introducing human APOE into mice ("How") and highlight efforts to develop temporally defined and location-specific human apoE expression models ("When" and "Where"). We conclude with the importance of choosing the human APOE mouse model relevant to the question being addressed, using the selection of transgenic models for testing apoE-targeted therapeutics as an example ("Why").
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Affiliation(s)
- Cutler T Lewandowski
- Department of Pharmaceutical Sciences, University of Illinois at Chicago, 833 S. Wood St., Chicago, IL 60612, USA.
| | - Juan Maldonado Weng
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, 808 S. Wood St., Chicago, IL 60612, USA.
| | - Mary Jo LaDu
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, 808 S. Wood St., Chicago, IL 60612, USA.
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8
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The Genetic Variability of APOE in Different Human Populations and Its Implications for Longevity. Genes (Basel) 2019; 10:genes10030222. [PMID: 30884759 PMCID: PMC6471373 DOI: 10.3390/genes10030222] [Citation(s) in RCA: 88] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 03/01/2019] [Accepted: 03/12/2019] [Indexed: 12/11/2022] Open
Abstract
Human longevity is a complex phenotype resulting from the combinations of context-dependent gene-environment interactions that require analysis as a dynamic process in a cohesive ecological and evolutionary framework. Genome-wide association (GWAS) and whole-genome sequencing (WGS) studies on centenarians pointed toward the inclusion of the apolipoprotein E (APOE) polymorphisms ε2 and ε4, as implicated in the attainment of extreme longevity, which refers to their effect in age-related Alzheimer's disease (AD) and cardiovascular disease (CVD). In this case, the available literature on APOE and its involvement in longevity is described according to an anthropological and population genetics perspective. This aims to highlight the evolutionary history of this gene, how its participation in several biological pathways relates to human longevity, and which evolutionary dynamics may have shaped the distribution of APOE haplotypes across the globe. Its potential adaptive role will be described along with implications for the study of longevity in different human groups. This review also presents an updated overview of the worldwide distribution of APOE alleles based on modern day data from public databases and ancient DNA samples retrieved from literature in the attempt to understand the spatial and temporal frame in which present-day patterns of APOE variation evolved.
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Williams B, Convertino M, Das J, Dokholyan NV. Molecular Mechanisms of the R61T Mutation in Apolipoprotein E4: A Dynamic Rescue. Biophys J 2017; 113:2192-2198. [PMID: 28916386 PMCID: PMC5700245 DOI: 10.1016/j.bpj.2017.08.026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 07/02/2017] [Accepted: 08/17/2017] [Indexed: 10/18/2022] Open
Abstract
The apolipoprotein E4 (ApoE4) gene is the strongest genetic risk factor for Alzheimer's disease (AD). With respect to the other common isoforms of this protein (ApoE2 and ApoE3), ApoE4 is characterized by lower stability that underlies the formation of a stable interaction between the protein's N- and C-terminal domains. AD-related cellular dysfunctions have been linked to this ApoE4 misfolded state. In this regard, it has been reported that the mutation R61T is able to rescue the deleterious cellular effects of ApoE4 by preventing the formation of the misfolded intermediate state. However, a clear description of the structural features at the basis of the R61T-ApoE4 mutant's protective effect is still missing. Recently, using extensive molecular dynamics simulations, we have identified a structural model of an ApoE4 misfolded intermediate state. Building on our previous work, here we explore the dynamical changes induced by the R61T mutation in the ApoE4 native and misfolded states. Notably, we do not observe any local changes in the domains in the R61T-ApoE4 system, rather a general loss of correlated movements in the entire protein structure. More specifically, we detect increased dynamics in the hinge region, which is essential for ApoE4 domain-domain interaction. Consistent with previously reported data on altered phospholipid and receptor binding, we hypothesize that mutations destabilizing the ApoE4 intermediate state change hinge region dynamics, which propagates to distal functional regions of the protein and modifies ApoE4's functional properties. This unique behavior of the ApoE4 hinge region provides, to our knowledge, a novel understanding of ApoE4's role in AD.
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Affiliation(s)
- Benfeard Williams
- Biochemistry and Biophysics Department, University of North Carolina, Chapel Hill, North Carolina
| | - Marino Convertino
- Biochemistry and Biophysics Department, University of North Carolina, Chapel Hill, North Carolina
| | - Jhuma Das
- Biochemistry and Biophysics Department, University of North Carolina, Chapel Hill, North Carolina
| | - Nikolay V Dokholyan
- Biochemistry and Biophysics Department, University of North Carolina, Chapel Hill, North Carolina.
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Wang H, Rempel DL, Giblin D, Frieden C, Gross ML. Peptide-Level Interactions between Proteins and Small-Molecule Drug Candidates by Two Hydrogen-Deuterium Exchange MS-Based Methods: The Example of Apolipoprotein E3. Anal Chem 2017; 89:10687-10695. [PMID: 28901129 DOI: 10.1021/acs.analchem.7b01121] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
We describe a platform utilizing two methods based on hydrogen-deuterium exchange (HDX) coupled with mass spectrometry (MS) to characterize interactions between a protein and a small-molecule ligand. The model system is apolipoprotein E3 (apoE3) and a small-molecule drug candidate. We extended PLIMSTEX (protein-ligand interactions by mass spectrometry, titration, and H/D exchange) to the regional level by incorporating enzymatic digestion to acquire binding information for peptides. In a single experiment, we not only identified putative binding sites, but also obtained affinities of 6.0, 6.8, and 10.6 μM for the three different regions, giving an overall binding affinity of 7.4 μM. These values agree well with literature values determined by accepted methods. Unlike those methods, PLIMSTEX provides site-specific binding information. The second approach, modified SUPREX (stability of unpurified proteins from rates of H/D exchange) coupled with electrospray ionization (ESI), allowed us to obtain detailed understanding about apoE unfolding and its changes upon ligand binding. Three binding regions, along with an additional site, which may be important for lipid binding, show increased stability (less unfolding) upon ligand binding. By employing a single parameter, ΔC1/2%, we compared relative changes of denaturation between peptides. This integrated platform provides information orthogonal to commonly used HDX kinetics experiments, providing a general and novel approach for studying protein-ligand interactions.
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Affiliation(s)
- Hanliu Wang
- Department of Chemistry, Washington University in St. Louis , One Brookings Drive, St. Louis, Missouri 63130, United States.,Analytical Research and Development, Pfizer Incorporated , Chesterfield, Missouri 63017, United States
| | - Don L Rempel
- Department of Chemistry, Washington University in St. Louis , One Brookings Drive, St. Louis, Missouri 63130, United States
| | - Daryl Giblin
- Department of Chemistry, Washington University in St. Louis , One Brookings Drive, St. Louis, Missouri 63130, United States
| | - Carl Frieden
- Department of Biochemistry and Molecular Biophysics, School of Medicine, Washington University in St. Louis , 660 South Euclid Avenue, St. Louis, Missouri 63110, United States
| | - Michael L Gross
- Department of Chemistry, Washington University in St. Louis , One Brookings Drive, St. Louis, Missouri 63130, United States
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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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12
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Lek MT, Cruz S, Ibe NU, Beck WHJ, Bielicki JK, Weers PMM, Narayanaswami V. Swapping the N- and C-terminal domains of human apolipoprotein E3 and AI reveals insights into their structure/activity relationship. PLoS One 2017. [PMID: 28644829 PMCID: PMC5482431 DOI: 10.1371/journal.pone.0178346] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Apolipoprotein (apo) E3 and apoAI are exchangeable apolipoproteins that play a dominant role in regulating plasma lipoprotein metabolism. ApoE3 (299 residues) is composed of an N-terminal (NT) domain bearing a 4-helix bundle and a C-terminal (CT) domain bearing a series of amphipathic α-helices. ApoAI (243 residues) also comprises a highly helical NT domain and a less structured CT tail. The objective of this study was to understand their structural and functional role by generating domain swapped chimeras: apoE3-NT/apoAI-CT and apoAI-NT/apoE-CT. The bacterially overexpressed chimeras were purified by affinity chromatography and their identity confirmed by immunoblotting and mass spectrometry. Their α-helical content was comparable to that of the parent proteins. ApoE3-NT/apoAI-CT retained the denaturation profile of apoE3 NT domain, with apoAI CT tail eliciting a relatively unstructured state; its lipid binding ability improved dramatically compared to apoE3 indicative of a significant role of apoAI CT tail in lipid binding interaction. The LDL receptor interaction and ability to promote ABCA1-mediated cholesterol efflux of apoE3-NT/apoAI-CT was comparable to that of apoE3. In contrast, apoAI-NT/apoE-CT elicited an unfolding pattern and lipid binding ability that were similar to that of apoAI. As expected, DMPC/apoAI-NT/apoE-CT discoidal particles did not elicit LDLr binding ability, and promoted SR-B1 mediated cellular uptake of lipids to a limited extent. However, apoAI-NT/apoE-CT displayed an enhanced ability to promote cholesterol efflux compared to apoAI, indicative of a significant role for apoE CT domain in mediating this function. Together, these results indicate that the functional attributes of apoAI and apoE3 can be conferred on each other and that NT-CT domain interactions significantly modulate their structure and function.
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Affiliation(s)
- Mark T. Lek
- 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
| | - Nnejiuwa U. Ibe
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, United States of America
| | - Wendy H. J. Beck
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, United States of America
| | - John K. Bielicki
- Donner Laboratory, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
| | - Paul M. M. Weers
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, 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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13
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Frieden C, Wang H, Ho CMW. A mechanism for lipid binding to apoE and the role of intrinsically disordered regions coupled to domain-domain interactions. Proc Natl Acad Sci U S A 2017; 114:6292-6297. [PMID: 28559318 PMCID: PMC5474821 DOI: 10.1073/pnas.1705080114] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Relative to the apolipoprotein E (apoE) E3 allele of the APOE gene, apoE4 strongly increases the risk for the development of late-onset Alzheimer's disease. However, apoE4 differs from apoE3 by only a single amino acid at position 112, which is arginine in apoE4 and cysteine in apoE3. It remains unclear why apoE3 and apoE4 are functionally different. Described here is a proposal for understanding the functional differences between these two isoforms with respect to lipid binding. A mechanism is proposed that is based on the full-length monomeric structure of the protein, on hydrogen-deuterium exchange mass spectrometry data, and on the role of intrinsically disordered regions to control protein motions. It is proposed that lipid binds between the N-terminal and C-terminal domains and that separation of the two domains, along with the presence of intrinsically disordered regions, controls this process. The mechanism explains why apoE3 differs from apoE4 with respect to different lipid-binding specificities, why lipid increases the binding of apoE to its receptor, and why specific residues are conserved.
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Affiliation(s)
- Carl Frieden
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110;
| | - Hanliu Wang
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130
| | - Chris M W Ho
- Drug Design Methodologies LLC, St. Louis, MO 63103
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14
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Helical structure, stability, and dynamics in human apolipoprotein E3 and E4 by hydrogen exchange and mass spectrometry. Proc Natl Acad Sci U S A 2017; 114:968-973. [PMID: 28096372 DOI: 10.1073/pnas.1617523114] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Apolipoprotein E (apoE) plays a critical role in cholesterol transport in both peripheral circulation and brain. Human apoE is a polymorphic 299-residue protein in which the less common E4 isoform differs from the major E3 isoform only by a C112R substitution. ApoE4 interacts with lipoprotein particles and with the amyloid-β peptide, and it is associated with increased incidence of cardiovascular and Alzheimer's disease. To understand the structural basis for the differences between apoE3 and E4 functionality, we used hydrogen-deuterium exchange coupled with a fragment separation method and mass spectrometric analysis to compare their secondary structures at near amino acid resolution. We determined the positions, dynamics, and stabilities of the helical segments in these two proteins, in their normal tetrameric state and in mutation-induced monomeric mutants. Consistent with prior X-ray crystallography and NMR results, the N-terminal domain contains four α-helices, 20 to 30 amino acids long. The C-terminal domain is relatively unstructured in the monomeric state but forms an α-helix ∼70 residues long in the self-associated tetrameric state. Helix stabilities are relatively low, 4 kcal/mol to 5 kcal/mol, consistent with flexibility and facile reversible unfolding. Secondary structure in the tetrameric apoE3 and E4 isoforms is similar except that some helical segments in apoE4 spanning residues 12 to 20 and 204 to 210 are unfolded. These conformational differences result from the C112R substitution in the N-terminal helix bundle and likely relate to a reduced ability of apoE4 to form tetramers, thereby increasing the concentration of functional apoE4 monomers, which gives rise to its higher lipid binding compared with apoE3.
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15
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Dose J, Huebbe P, Nebel A, Rimbach G. APOE genotype and stress response - a mini review. Lipids Health Dis 2016; 15:121. [PMID: 27457486 PMCID: PMC4960866 DOI: 10.1186/s12944-016-0288-2] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Accepted: 07/12/2016] [Indexed: 12/31/2022] Open
Abstract
The APOE gene is one of currently only two genes that have consistently been associated with longevity. Apolipoprotein E (APOE) is a plasma protein which plays an important role in lipid and lipoprotein metabolism. In humans, there are three major APOE isoforms, designated APOE2, APOE3, and APOE4. Of these three isoforms, APOE3 is most common while APOE4 was shown to be associated with age-related diseases, including cardiovascular and Alzheimer’s disease, and therefore an increased mortality risk with advanced age. Evidence accumulates, showing that oxidative stress and, correspondingly, mitochondrial function is affected in an APOE isoform-dependent manner. Accordingly, several stress response pathways implicated in the aging process, including the endoplasmic reticulum stress response and immune function, appear to be influenced by the APOE genotype. The investigation and development of treatment strategies targeting APOE4 have not resolved any therapeutic yet that could be entirely recommended. This mini-review provides an overview on the state of research concerning the impact of the APOE genotype on stress response-related processes, emphasizing the strong interconnection between mitochondrial function, endoplasmic reticulum stress and the immune response. Furthermore, this review addresses potential treatment strategies and associated pitfalls as well as lifestyle interventions that could benefit people with an at risk APOE4 genotype.
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Affiliation(s)
- Janina Dose
- Institute of Human Nutrition and Food Science, Kiel University, Hermann-Rodewald-Str. 6, D-24118, Kiel, Germany. .,Institute of Clinical Molecular Biology, Kiel University, Schittenhelmstr. 12, D-24105, Kiel, Germany.
| | - Patricia Huebbe
- Institute of Human Nutrition and Food Science, Kiel University, Hermann-Rodewald-Str. 6, D-24118, Kiel, Germany
| | - Almut Nebel
- Institute of Clinical Molecular Biology, Kiel University, Schittenhelmstr. 12, D-24105, Kiel, Germany
| | - Gerald Rimbach
- Institute of Human Nutrition and Food Science, Kiel University, Hermann-Rodewald-Str. 6, D-24118, Kiel, Germany
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16
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Dose J, Nebel A, Piegholdt S, Rimbach G, Huebbe P. Influence of the APOE genotype on hepatic stress response: Studies in APOE targeted replacement mice and human liver cells. Free Radic Biol Med 2016; 96:264-72. [PMID: 27130033 DOI: 10.1016/j.freeradbiomed.2016.04.031] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 04/22/2016] [Accepted: 04/25/2016] [Indexed: 11/29/2022]
Abstract
Apolipoprotein E (APOE) is a multifunctional plasma protein mainly acting in lipid metabolism. Human APOE is polymorphic with three major isoforms (APOE2, APOE3 and APOE4). Up to 75% of the body's APOE is produced by the liver. There is increasing evidence from studies in brain-derived cells that APOE4 affects mitochondrial function and biogenesis as well as stress and inflammatory responses - processes, whose disturbances are considered hallmarks of the ageing process. However, although the liver is the main production site of APOE, knowledge about the impact of the APOE genotype on hepatic stress response-related processes is rather limited. Therefore, we studied biomarkers of oxidative status (glutathione levels, 3-nitrotyrosine adducts, protein carbonyl concentration), ER stress (XBP1(S), BiP, DDIT3), proteasome activity, mitochondrial function (respiratory complexes, ATP levels and mitochondrial membrane potential as well as biomarkers of mitochondrial biogenesis, fission and fusion), autophagy (LC3, LAMP2A), apoptosis (BCL2, BAX, CYCS) and DNA damage in the liver of APOE targeted replacement (TR) mice and in Huh7 hepatocytes overexpressing the APOE3 and the APOE4 isoform, respectively. APOE4 mice exhibited a lower chymotrypsin-like and a higher trypsin-like proteasome activity. Levels of protein carbonyls were moderately higher in liver tissue of APOE4 vs. APOE3 mice. Other biomarkers of oxidative stress were similar between the two genotypes. Under basal conditions, the stress-response pathways investigated appeared largely unaffected by the APOE genotype. However, upon stress induction, APOE4 expressing cells showed lower levels of adenosine triphosphate (ATP) and lower mRNA levels of the ATP-generating complex V of the mitochondrial respiratory chain. Overall, our findings provide evidence for a rather low influence of the APOE genotype on the hepatic stress response processes investigated in this study.
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Affiliation(s)
- Janina Dose
- Institute of Human Nutrition and Food Science, University of Kiel, Hermann-Rodewald-Str. 6, 24118 Kiel, Germany.
| | - Almut Nebel
- Institute of Clinical Molecular Biology, University of Kiel, University Hospital Schleswig-Holstein, Schittenhelmstr. 12, 24105 Kiel, Germany.
| | - Stefanie Piegholdt
- Institute of Human Nutrition and Food Science, University of Kiel, Hermann-Rodewald-Str. 6, 24118 Kiel, Germany.
| | - Gerald Rimbach
- Institute of Human Nutrition and Food Science, University of Kiel, Hermann-Rodewald-Str. 6, 24118 Kiel, Germany.
| | - Patricia Huebbe
- Institute of Human Nutrition and Food Science, University of Kiel, Hermann-Rodewald-Str. 6, 24118 Kiel, Germany.
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17
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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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Mizuguchi C, Hata M, Dhanasekaran P, Nickel M, Okuhira K, Phillips MC, Lund-Katz S, Saito H. Fluorescence study of domain structure and lipid interaction of human apolipoproteins E3 and E4. Biochim Biophys Acta Mol Cell Biol Lipids 2015; 1841:1716-24. [PMID: 25281910 DOI: 10.1016/j.bbalip.2014.09.019] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 09/06/2014] [Accepted: 09/24/2014] [Indexed: 12/19/2022]
Abstract
Human apolipoprotein E (apoE) isoforms exhibit different conformational stabilities and lipid-binding properties that give rise to altered cholesterol metabolism among the isoforms. Using Trp-substituted mutations and site- directed fluorescence labeling, we made a comprehensive comparison of the conformational organization of the N- and C-terminal domains and lipid interactions between the apoE3 and apoE4 isoforms. Trp fluorescence measurements for selectively Trp-substituted variants of apoE isoforms demonstrated that apoE4 adopts less stable conformations in both the N- and C-terminal domains compared to apoE3. Consistent with this, the conformational reorganization of the N-terminal helix bundle occurs at lower guanidine hydrochloride concentration in apoE4 than in apoE3 as monitored by fluorescence resonance energy transfer (FRET) from Trp residues to acrylodan attached at the N-terminal helix. Upon binding of apoE3 and apoE4 variants to egg phosphatidylcholine small unilamellar vesicles, similar changes in Trp fluorescence or FRET efficiency were observed for the isoforms, indi- cating that the opening of the N-terminal helix bundle occurs similarly in apoE3 and apoE4. Introduction of mutations into the C-terminal domain of the apoE isoforms to prevent self-association and maintain the monomeric state resulted in great increase in the rate of binding of the C-terminal helices to a lipid surface. Overall, our results demonstrate that the different conformational organizations of the N- and C-terminal domains have a minor effect on the steady-state lipid-binding behavior of apoE3 and apoE4: rather, self-association property is a critical determinant in the kinetics of lipid binding through the C-terminal helices of apoE isoforms.
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Amyloid-Forming Properties of Human Apolipoproteins: Sequence Analyses and Structural Insights. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 855:175-211. [PMID: 26149931 DOI: 10.1007/978-3-319-17344-3_8] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Apolipoproteins are protein constituents of lipoproteins that transport cholesterol and fat in circulation and are central to cardiovascular health and disease. Soluble apolipoproteins can transiently dissociate from the lipoprotein surface in a labile free form that can misfold, potentially leading to amyloid disease. Misfolding of apoA-I, apoA-II, and serum amyloid A (SAA) causes systemic amyloidoses, apoE4 is a critical risk factor in Alzheimer's disease, and apolipoprotein misfolding is also implicated in cardiovascular disease. To explain why apolipoproteins are over-represented in amyloidoses, it was proposed that the amphipathic α-helices, which form the lipid surface-binding motif in this protein family, have high amyloid-forming propensity. Here, we use 12 sequence-based bioinformatics approaches to assess amyloid-forming potential of human apolipoproteins and to identify segments that are likely to initiate β-aggregation. Mapping such segments on the available atomic structures of apolipoproteins helps explain why some of them readily form amyloid while others do not. Our analysis shows that nearly all amyloidogenic segments: (i) are largely hydrophobic, (ii) are located in the lipid-binding amphipathic α-helices in the native structures of soluble apolipoproteins, (iii) are predicted in both native α-helices and β-sheets in the insoluble apoB, and (iv) are predicted to form parallel in-register β-sheet in amyloid. Most of these predictions have been verified experimentally for apoC-II, apoA-I, apoA-II and SAA. Surprisingly, the rank order of the amino acid sequence propensity to form amyloid (apoB>apoA-II>apoC-II≥apoA-I, apoC-III, SAA, apoC-I>apoA-IV, apoA-V, apoE) does not correlate with the proteins' involvement in amyloidosis. Rather, it correlates directly with the strength of the protein-lipid association, which increases with increasing protein hydrophobicity. Therefore, the lipid surface-binding function and the amyloid-forming propensity are both rooted in apolipoproteins' hydrophobicity, suggesting that functional constraints make it difficult to completely eliminate pathogenic apolipoprotein misfolding. We propose that apolipoproteins have evolved protective mechanisms against misfolding, such as the sequestration of the amyloidogenic segments via the native protein-lipid and protein-protein interactions involving amphipathic α-helices and, in case of apoB, β-sheets.
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