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Asiamah EA, Feng B, Guo R, Yaxing X, Du X, Liu X, Zhang J, Cui H, Ma J. The Contributions of the Endolysosomal Compartment and Autophagy to APOEɛ4 Allele-Mediated Increase in Alzheimer's Disease Risk. J Alzheimers Dis 2024; 97:1007-1031. [PMID: 38306054 DOI: 10.3233/jad-230658] [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] [Indexed: 02/03/2024]
Abstract
Apolipoprotein E4 (APOE4), although yet-to-be fully understood, increases the risk and lowers the age of onset of Alzheimer's disease (AD), which is the major cause of dementia among elderly individuals. The endosome-lysosome and autophagy pathways, which are necessary for homeostasis in both neurons and glia, are dysregulated even in early AD. Nonetheless, the contributory roles of these pathways to developing AD-related pathologies in APOE4 individuals and models are unclear. Therefore, this review summarizes the dysregulations in the endosome-lysosome and autophagy pathways in APOE4 individuals and non-human models, and how these anomalies contribute to developing AD-relevant pathologies. The available literature suggests that APOE4 causes endosomal enlargement, increases endosomal acidification, impairs endosomal recycling, and downregulates exosome production. APOE4 impairs autophagy initiation and inhibits basal autophagy and autophagy flux. APOE4 promotes lysosome formation and trafficking and causes ApoE to accumulate in lysosomes. APOE4-mediated changes in the endosome, autophagosome and lysosome could promote AD-related features including Aβ accumulation, tau hyperphosphorylation, glial dysfunction, lipid dyshomeostasis, and synaptic defects. ApoE4 protein could mediate APOE4-mediated endosome-lysosome-autophagy changes. ApoE4 impairs vesicle recycling and endosome trafficking, impairs the synthesis of autophagy genes, resists being dissociated from its receptors and degradation, and forms a stable folding intermediate that could disrupt lysosome structure. Drugs such as molecular correctors that target ApoE4 molecular structure and enhance autophagy may ameliorate the endosome-lysosome-autophagy-mediated increase in AD risk in APOE4 individuals.
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Affiliation(s)
- Ernest Amponsah Asiamah
- Hebei Medical University-Galway University of Ireland Stem Cell Research Center, Hebei Medical University, Hebei, China
- Department of Biomedical Sciences, College of Health and Allied Sciences, University of Cape Coast, PMB UCC, Cape Coast, Ghana
| | - Baofeng Feng
- Hebei Medical University-Galway University of Ireland Stem Cell Research Center, Hebei Medical University, Hebei, China
- Hebei Research Center for Stem Cell Medical Translational Engineering, Hebei, China
- Hebei Technology Innovation Center for Stem Cell and Regenerative Medicine, Hebei, China
| | - Ruiyun Guo
- Hebei Medical University-Galway University of Ireland Stem Cell Research Center, Hebei Medical University, Hebei, China
- Hebei Research Center for Stem Cell Medical Translational Engineering, Hebei, China
| | - Xu Yaxing
- Hebei Medical University-Galway University of Ireland Stem Cell Research Center, Hebei Medical University, Hebei, China
- Hebei Research Center for Stem Cell Medical Translational Engineering, Hebei, China
| | - Xiaofeng Du
- Hebei Medical University-Galway University of Ireland Stem Cell Research Center, Hebei Medical University, Hebei, China
- Hebei Research Center for Stem Cell Medical Translational Engineering, Hebei, China
| | - Xin Liu
- Hebei Medical University-Galway University of Ireland Stem Cell Research Center, Hebei Medical University, Hebei, China
- Hebei Research Center for Stem Cell Medical Translational Engineering, Hebei, China
| | - Jinyu Zhang
- Hebei Medical University-Galway University of Ireland Stem Cell Research Center, Hebei Medical University, Hebei, China
- Hebei Research Center for Stem Cell Medical Translational Engineering, Hebei, China
| | - Huixian Cui
- Hebei Medical University-Galway University of Ireland Stem Cell Research Center, Hebei Medical University, Hebei, China
- Hebei Research Center for Stem Cell Medical Translational Engineering, Hebei, China
- Hebei Technology Innovation Center for Stem Cell and Regenerative Medicine, Hebei, China
| | - Jun Ma
- Hebei Medical University-Galway University of Ireland Stem Cell Research Center, Hebei Medical University, Hebei, China
- Hebei Research Center for Stem Cell Medical Translational Engineering, Hebei, China
- Hebei Technology Innovation Center for Stem Cell and Regenerative Medicine, Hebei, China
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2
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Abyadeh M, Gupta V, Paulo JA, Sheriff S, Shadfar S, Fitzhenry M, Amirkhani A, Gupta V, Salekdeh GH, Haynes PA, Graham SL, Mirzaei M. Apolipoprotein ε in Brain and Retinal Neurodegenerative Diseases. Aging Dis 2023; 14:1311-1330. [PMID: 37199411 PMCID: PMC10389820 DOI: 10.14336/ad.2023.0312-1] [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: 01/11/2023] [Accepted: 03/12/2023] [Indexed: 05/19/2023] Open
Abstract
Alzheimer's disease (AD) is the most common form of dementia that remains incurable and has become a major medical, social, and economic challenge worldwide. AD is characterized by pathological hallmarks of senile plaques (SP) and neurofibrillary tangles (NFTs) that damage the brain up to twenty years before a clinical diagnosis is made. Interestingly these pathological features have also been observed in retinal neurodegenerative diseases including age related macular degeneration (ARMD), glaucoma and diabetic retinopathy (DR). An association of AD with these diseases has been suggested in epidemiological studies and several common pathological events and risk factors have been identified between these diseases. The E4 allele of Apolipoprotein E (APOE) is a well-established genetic risk factor for late onset AD. The ApoE ε4 allele is also associated with retinal neurodegenerative diseases however in contrast to AD, it is considered protective in AMD, likewise ApoE E2 allele, which is a protective factor for AD, has been implicated as a risk factor for AMD and glaucoma. This review summarizes the evidence on the effects of ApoE in retinal neurodegenerative diseases and discusses the overlapping molecular pathways in AD. The involvement of ApoE in regulating amyloid beta (Aβ) and tau pathology, inflammation, vascular integrity, glucose metabolism and vascular endothelial growth factor (VEGF) signaling is also discussed.
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Affiliation(s)
| | - Vivek Gupta
- Department of Clinical Medicine, Faculty of Medicine, Health and Human Sciences, Macquarie Medical School, Macquarie University, Macquarie Park, North Ryde, Sydney, NSW 2109, Australia.
| | - Joao A Paulo
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
| | - Samran Sheriff
- Department of Clinical Medicine, Faculty of Medicine, Health and Human Sciences, Macquarie Medical School, Macquarie University, Macquarie Park, North Ryde, Sydney, NSW 2109, Australia.
| | - Sina Shadfar
- Department of Clinical Medicine, Faculty of Medicine, Health and Human Sciences, Macquarie Medical School, Macquarie University, Macquarie Park, North Ryde, Sydney, NSW 2109, Australia.
| | - Matthew Fitzhenry
- Australian Proteome Analysis Facility, Macquarie University, Macquarie Park, NSW 2113, Australia.
| | - Ardeshir Amirkhani
- Australian Proteome Analysis Facility, Macquarie University, Macquarie Park, NSW 2113, Australia.
| | - Veer Gupta
- School of Medicine, Deakin University, VIC, Australia.
| | - Ghasem H Salekdeh
- School of Natural Sciences, Macquarie University, Macquarie Park, NSW 2109, Australia.
| | - Paul A Haynes
- School of Natural Sciences, Macquarie University, Macquarie Park, NSW 2109, Australia.
| | - Stuart L Graham
- Department of Clinical Medicine, Faculty of Medicine, Health and Human Sciences, Macquarie Medical School, Macquarie University, Macquarie Park, North Ryde, Sydney, NSW 2109, Australia.
| | - Mehdi Mirzaei
- Department of Clinical Medicine, Faculty of Medicine, Health and Human Sciences, Macquarie Medical School, Macquarie University, Macquarie Park, North Ryde, Sydney, NSW 2109, Australia.
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3
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Steele OG, Stuart AC, Minkley L, Shaw K, Bonnar O, Anderle S, Penn AC, Rusted J, Serpell L, Hall C, King S. A multi-hit hypothesis for an APOE4-dependent pathophysiological state. Eur J Neurosci 2022; 56:5476-5515. [PMID: 35510513 PMCID: PMC9796338 DOI: 10.1111/ejn.15685] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 03/31/2022] [Accepted: 04/25/2022] [Indexed: 01/01/2023]
Abstract
The APOE gene encoding the Apolipoprotein E protein is the single most significant genetic risk factor for late-onset Alzheimer's disease. The APOE4 genotype confers a significantly increased risk relative to the other two common genotypes APOE3 and APOE2. Intriguingly, APOE4 has been associated with neuropathological and cognitive deficits in the absence of Alzheimer's disease-related amyloid or tau pathology. Here, we review the extensive literature surrounding the impact of APOE genotype on central nervous system dysfunction, focussing on preclinical model systems and comparison of APOE3 and APOE4, given the low global prevalence of APOE2. A multi-hit hypothesis is proposed to explain how APOE4 shifts cerebral physiology towards pathophysiology through interconnected hits. These hits include the following: neurodegeneration, neurovascular dysfunction, neuroinflammation, oxidative stress, endosomal trafficking impairments, lipid and cellular metabolism disruption, impaired calcium homeostasis and altered transcriptional regulation. The hits, individually and in combination, leave the APOE4 brain in a vulnerable state where further cumulative insults will exacerbate degeneration and lead to cognitive deficits in the absence of Alzheimer's disease pathology and also a state in which such pathology may more easily take hold. We conclude that current evidence supports an APOE4 multi-hit hypothesis, which contributes to an APOE4 pathophysiological state. We highlight key areas where further study is required to elucidate the complex interplay between these individual mechanisms and downstream consequences, helping to frame the current landscape of existing APOE-centric literature.
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Affiliation(s)
| | | | - Lucy Minkley
- School of Life SciencesUniversity of SussexBrightonUK
| | - Kira Shaw
- School of Life SciencesUniversity of SussexBrightonUK
| | - Orla Bonnar
- School of Life SciencesUniversity of SussexBrightonUK
| | | | | | | | | | | | - Sarah King
- School of PsychologyUniversity of SussexBrightonUK
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4
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Vecchio FL, Bisceglia P, Imbimbo BP, Lozupone M, Latino RR, Resta E, Leone M, Solfrizzi V, Greco A, Daniele A, Watling M, Panza F, Seripa D. Are apolipoprotein E fragments a promising new therapeutic target for Alzheimer’s disease? Ther Adv Chronic Dis 2022; 13:20406223221081605. [PMID: 35321401 PMCID: PMC8935560 DOI: 10.1177/20406223221081605] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Accepted: 01/28/2022] [Indexed: 11/17/2022] Open
Abstract
Human apolipoprotein E (ApoE) is a 299-amino acid secreted glycoprotein that binds cholesterol and phospholipids. ApoE exists as three common isoforms (ApoE2, ApoE3, and ApoE4) and heterozygous carriers of the ε4 allele of the gene encoding ApoE (APOE) have a fourfold greater risk of developing Alzheimer’s disease (AD). The enzymes thrombin, cathepsin D, α-chymotrypsin-like serine protease, and high-temperature requirement serine protease A1 are responsible for ApoE proteolytic processing resulting in bioactive C-terminal-truncated fragments that vary depending on ApoE isoforms, brain region, aging, and neural injury. The objectives of the present narrative review were to describe ApoE processing, discussing current hypotheses about the potential role of various ApoE fragments in AD pathophysiology, and reviewing the current development status of different anti-ApoE drugs. The exact mechanism by which APOE gene variants increase/decrease AD risk and the role of ApoE fragments in the deposition are not fully understood, but APOE is known to directly affect tau-mediated neurodegeneration. ApoE fragments co-localize with neurofibrillary tangles and amyloid β (Aβ) plaques, and may cause neurodegeneration. Among anti-ApoE approaches, a fascinating strategy may be to therapeutically overexpress ApoE2 in APOE ε4/ε4 carriers through vector administration or liposomal delivery systems. Another approach involves reducing ApoE4 expression by intracerebroventricular antisense oligonucleotides that significantly decreased Aβ pathology in transgenic mice. Differences in the proteolytic processing of distinct ApoE isoforms and the use of ApoE fragments as mimetic peptides in AD treatment are also under investigation. Treatment with peptides that mimic the structural and biological properties of native ApoE may reduce Aβ deposition, tau hyperphosphorylation, and glial activation in mouse models of Aβ pathology. Alternative strategies involve the use of ApoE4 structure correctors, passive immunization to target a certain form of ApoE, conversion of the ApoE4 aminoacid sequence into that of ApoE3 or ApoE2, and inhibition of the ApoE-Aβ interaction.
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Affiliation(s)
- Filomena Lo Vecchio
- Research Laboratory, Complex Structure of Geriatrics, Department of Medical Sciences, Fondazione IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, Foggia 71013, Italy
| | - Paola Bisceglia
- Research Laboratory, Complex Structure of Geriatrics, Department of Medical Sciences, Fondazione IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, Italy
| | | | - Madia Lozupone
- Neurodegenerative Disease Unit, Department of Basic Medicine, Neuroscience, and Sense Organs, University of Bari Aldo Moro, Bari, Italy
| | - Raffaela Rita Latino
- Complex Structure of Neurology, Department of Medical Sciences, Fondazione IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, Italy
| | - Emanuela Resta
- Translational Medicine and Management of Health Systems, University of Foggia, Foggia, Italy
| | - Maurizio Leone
- Complex Structure of Neurology, Department of Medical Sciences, Fondazione IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, Italy
| | - Vincenzo Solfrizzi
- ‘Cesare Frugoni’ Internal and Geriatric Medicine and Memory Unit, University of Bari ‘Aldo Moro’, Bari, Italy
| | - Antonio Greco
- Department of Neuroscience, Catholic University of the Sacred Heart, Rome, Italy; Neurology Unit, IRCCS Fondazione Policlinico Universitario A. Gemelli, Rome, Italy
- Research Laboratory, Complex Structure of Geriatrics, Department of Medical Sciences, Fondazione IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, Italy
| | | | - Mark Watling
- CNS & Pain Department, TranScrip Ltd, Reading, UK
| | - Francesco Panza
- Research Laboratory, Complex Structure of Geriatrics, Department of Medical Sciences, Fondazione IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, Foggia, Italy
- Population Health Unit, Healthy Aging Phenotypes Research Unit, ‘Salus in Apulia Study’, National Institute of Gastroenterology ‘Saverio de Bellis’, Research Hospital, Castellana Grotte, Bari 70013, Italy
| | - Davide Seripa
- Research Laboratory, Complex Structure of Geriatrics, Department of Medical Sciences, Fondazione IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, Italy
- Hematology and Stem Cell Transplant Unit, ‘Vito Fazzi’ Hospital, Lecce, Italy
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5
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Lewandowski CT, Laham MS, Thatcher GR. Remembering your A, B, C's: Alzheimer's disease and ABCA1. Acta Pharm Sin B 2022; 12:995-1018. [PMID: 35530134 PMCID: PMC9072248 DOI: 10.1016/j.apsb.2022.01.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 12/27/2021] [Accepted: 01/07/2022] [Indexed: 12/24/2022] Open
Abstract
The function of ATP binding cassette protein A1 (ABCA1) is central to cholesterol mobilization. Reduced ABCA1 expression or activity is implicated in Alzheimer's disease (AD) and other disorders. Therapeutic approaches to boost ABCA1 activity have yet to be translated successfully to the clinic. The risk factors for AD development and progression, including comorbid disorders such as type 2 diabetes and cardiovascular disease, highlight the intersection of cholesterol transport and inflammation. Upregulation of ABCA1 can positively impact APOE lipidation, insulin sensitivity, peripheral vascular and blood–brain barrier integrity, and anti-inflammatory signaling. Various strategies towards ABCA1-boosting compounds have been described, with a bias toward nuclear hormone receptor (NHR) agonists. These agonists display beneficial preclinical effects; however, important side effects have limited development. In particular, ligands that bind liver X receptor (LXR), the primary NHR that controls ABCA1 expression, have shown positive effects in AD mouse models; however, lipogenesis and unwanted increases in triglyceride production are often observed. The longstanding approach, focusing on LXRβ vs. LXRα selectivity, is over-simplistic and has failed. Novel approaches such as phenotypic screening may lead to small molecule NHR modulators that elevate ABCA1 function without inducing lipogenesis and are clinically translatable.
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6
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Konings SC, Torres-Garcia L, Martinsson I, Gouras GK. Astrocytic and Neuronal Apolipoprotein E Isoforms Differentially Affect Neuronal Excitability. Front Neurosci 2021; 15:734001. [PMID: 34621153 PMCID: PMC8490647 DOI: 10.3389/fnins.2021.734001] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 08/23/2021] [Indexed: 11/25/2022] Open
Abstract
Synaptic changes and neuronal network dysfunction are among the earliest changes in Alzheimer’s disease (AD). Apolipoprotein E4 (ApoE4), the major genetic risk factor in AD, has been shown to be present at synapses and to induce hyperexcitability in mouse knock-in brain regions vulnerable to AD. ApoE in the brain is mainly generated by astrocytes, however, neurons can also produce ApoE under stress conditions such as aging. The potential synaptic function(s) of ApoE and whether the cellular source of ApoE might affect neuronal excitability remain poorly understood. Therefore, the aim of this study was to elucidate the synaptic localization and effects on neuronal activity of the two main human ApoE isoforms from different cellular sources in control and AD-like in vitro cultured neuron models. In this study ApoE is seen to localize at or near to synaptic terminals. Additionally, we detected a cellular source-specific effect of ApoE isoforms on neuronal activity measured by live cell Ca2+ imaging. Neuronal activity increases after acute but not long-term administration of ApoE4 astrocyte medium. In contrast, ApoE expressed by neurons appears to induce the highest neuronal firing rate in the presence of ApoE3, rather than ApoE4. Moreover, increased neuronal activity in APP/PS1 AD transgenic compared to wild-type neurons is seen in the absence of astrocytic ApoE and the presence of astrocytic ApoE4, but not ApoE3. In summary, ApoE can target synapses and differentially induce changes in neuronal activity depending on whether ApoE is produced by astrocytes or neurons. Astrocytic ApoE induces the strongest neuronal firing with ApoE4, while the most active and efficient neuronal activity induced by neuronal ApoE is caused by ApoE3. ApoE isoforms also differentially affect neuronal activity in AD transgenic compared to wild-type neurons.
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Affiliation(s)
- Sabine C Konings
- Experimental Dementia Research Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Laura Torres-Garcia
- Experimental Dementia Research Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Isak Martinsson
- Experimental Dementia Research Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Gunnar K Gouras
- Experimental Dementia Research Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
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7
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Amponsah AE, Feng B, Guo R, Zhang W, He J, Kong D, Dong T, Ma J, Cui H. Fragmentation of brain apolipoprotein E (ApoE) and its relevance in Alzheimer's disease. Rev Neurosci 2021; 31:589-603. [PMID: 32364519 DOI: 10.1515/revneuro-2019-0115] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Accepted: 02/01/2020] [Indexed: 11/15/2022]
Abstract
Alzheimer's disease (AD) is a very common cause of dementia in the elderly. It is characterized by progressive amnesia and accretions of neurofibrillary tangles (NFTs) of neurons and senile plaques in the neuropil. After aging, the inheritance of the apolipoprotein E (ApoE) epsilon 4 (ε4) allele is the greatest risk factor for late-onset AD. The ApoE protein is the translated product of the ApoE gene. This protein undergoes proteolysis, and the resulting fragments colocalize with neurofibrillary tangles and amyloid plaques, and for that matter may be involved in AD onset and/or progression. Previous studies have reported the pathogenic potential of various ApoE fragments in AD pathophysiology. However, the pathways activated by the fragments are not fully understood. In this review, ApoE fragments obtained from post-mortem brains and body fluids, cerebrospinal fluid (CSF) and plasma, are discussed. Additionally, current knowledge about the process of fragmentation is summarized. Finally, the mechanisms by which these fragments are involved in AD pathogenesis and pathophysiology are discussed.
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Affiliation(s)
- Asiamah Ernest Amponsah
- Hebei Medical University-National University of Ireland Galway Stem Cell Research Center, Hebei Medical University, Shijiazhuang, 050017, Hebei Province, China.,Hebei Research Center for Stem Cell Medical Translational Engineering, Shijiazhuang, 050017, Hebei Province, China
| | - Baofeng Feng
- Hebei Medical University-National University of Ireland Galway Stem Cell Research Center, Hebei Medical University, Shijiazhuang, 050017, Hebei Province, China.,Hebei Research Center for Stem Cell Medical Translational Engineering, Shijiazhuang, 050017, Hebei Province, China
| | - Ruiyun Guo
- Hebei Medical University-National University of Ireland Galway Stem Cell Research Center, Hebei Medical University, Shijiazhuang, 050017, Hebei Province, China.,Hebei Research Center for Stem Cell Medical Translational Engineering, Shijiazhuang, 050017, Hebei Province, China
| | - Wei Zhang
- Hebei Medical University-National University of Ireland Galway Stem Cell Research Center, Hebei Medical University, Shijiazhuang, 050017, Hebei Province, China.,Hebei Research Center for Stem Cell Medical Translational Engineering, Shijiazhuang, 050017, Hebei Province, China
| | - Jingjing He
- Hebei Medical University-National University of Ireland Galway Stem Cell Research Center, Hebei Medical University, Shijiazhuang, 050017, Hebei Province, China.,Hebei Research Center for Stem Cell Medical Translational Engineering, Shijiazhuang, 050017, Hebei Province, China
| | - Desheng Kong
- Hebei Medical University-National University of Ireland Galway Stem Cell Research Center, Hebei Medical University, Shijiazhuang, 050017, Hebei Province, China.,Hebei Research Center for Stem Cell Medical Translational Engineering, Shijiazhuang, 050017, Hebei Province, China
| | - Tianyu Dong
- Hebei Medical University-National University of Ireland Galway Stem Cell Research Center, Hebei Medical University, Shijiazhuang, 050017, Hebei Province, China.,Hebei Research Center for Stem Cell Medical Translational Engineering, Shijiazhuang, 050017, Hebei Province, China.,Human Anatomy Department, Hebei Medical University, Shijiazhuang, 050017, Hebei Province, China
| | - Jun Ma
- Hebei Medical University-National University of Ireland Galway Stem Cell Research Center, Hebei Medical University, Shijiazhuang, 050017, Hebei Province, China.,Hebei Research Center for Stem Cell Medical Translational Engineering, Shijiazhuang, 050017, Hebei Province, China.,China Human Anatomy Department, Hebei Medical University, Shijiazhuang, 050017, Hebei Province, China
| | - Huixian Cui
- Hebei Medical University-National University of Ireland Galway Stem Cell Research Center, Hebei Medical University, Shijiazhuang, 050017, Hebei Province, China.,Hebei Research Center for Stem Cell Medical Translational Engineering, Shijiazhuang, 050017, Hebei Province, China.,China Human Anatomy Department, Hebei Medical University, Shijiazhuang, 050017, Hebei Province, China
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8
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Lanfranco MF, Sepulveda J, Kopetsky G, Rebeck GW. Expression and secretion of apoE isoforms in astrocytes and microglia during inflammation. Glia 2021; 69:1478-1493. [PMID: 33556209 DOI: 10.1002/glia.23974] [Citation(s) in RCA: 54] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Revised: 01/24/2021] [Accepted: 01/24/2021] [Indexed: 12/15/2022]
Abstract
Neuroinflammation is a common feature in neurodegenerative diseases, modulated by the Alzheimer's disease risk factor, apolipoprotein E (APOE). In the brain, apoE protein is synthesized by astrocytes and microglia. We examined primary cultures of astrocytes and microglia from human APOE (E2, E3, and E4) targeted-replacement mice. Astrocytes secreted two species of apoE, whereas cellular apoE consisted of only one. Both forms of secreted astrocytic apoE were bound during glycoprotein isolation, and enzymatic removal of glycans produced a convergence of the two forms of apoE to a single form; thus, the two species of astrocyte-secreted apoE are differentially glycosylated. Microglia released only a single species of apoE, while cellular apoE consisted of two forms; the secreted apoE and one of the two forms of cellular apoE were glycosylated. We treated the primary glia with either endogenous (TNFα) or exogenous (LPS) pro-inflammatory stimuli. While LPS had no effect on astrocytic apoE, APOE2, and APOE3 microglia increased release of apoE; APOE4 microglia showed no effect. APOE4 microglia showed higher baseline secretion of TNFα compared to APOE2 and APOE3 microglia. TNFα treatment reduced the secretion and cellular expression of apoE only in APOE4 astrocytes. The patterns of apoE species produced by astrocytes and microglia were not affected by inflammation. No changes in APOE mRNA were observed in astrocytes after both treatments. Together, our data demonstrate that astrocytes and microglia differentially express and secrete glycosylated forms of apoE and that APOE4 astrocytes and microglia are deficient in immunomodulation compared to APOE2 and APOE3.
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Affiliation(s)
- Maria Fe Lanfranco
- Department of Neuroscience, Georgetown University Medical Center, Washington, District of Columbia, USA
| | - Jordy Sepulveda
- Department of Pharmacology & Physiology, Georgetown University Medical Center, Washington, District of Columbia, USA
| | - Gregory Kopetsky
- Department of Neuroscience, Georgetown University Medical Center, Washington, District of Columbia, USA
| | - G William Rebeck
- Department of Neuroscience, Georgetown University Medical Center, Washington, District of Columbia, USA
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9
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Raman S, Brookhouser N, Brafman DA. Using human induced pluripotent stem cells (hiPSCs) to investigate the mechanisms by which Apolipoprotein E (APOE) contributes to Alzheimer's disease (AD) risk. Neurobiol Dis 2020; 138:104788. [PMID: 32032733 PMCID: PMC7098264 DOI: 10.1016/j.nbd.2020.104788] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2019] [Revised: 01/14/2020] [Accepted: 01/31/2020] [Indexed: 01/02/2023] Open
Abstract
Although the biochemical and pathological hallmarks of Alzheimer's disease (AD), such as axonal transport defects, synaptic loss, and selective neuronal death, are well characterized, the underlying mechanisms that cause AD are largely unknown, thereby making it difficult to design effective therapeutic interventions. Genome-wide association studies (GWAS) studies have identified several factors associated with increased AD risk. Of these genetic factors, polymorphisms in the Apolipoprotein E (APOE) gene are the strongest and most prevalent. While it has been established that the ApoE protein modulates the formation of amyloid plaques and neurofibrillary tangles, the precise molecular mechanisms by which various ApoE isoforms enhance or mitigate AD onset and progression in aging adults are yet to be elucidated. Advances in cellular reprogramming to generate disease-in-a-dish models now provide a simplified and accessible system that complements animal and primary cell models to study ApoE in the context of AD. In this review, we will describe the use and manipulation of human induced pluripotent stem cells (hiPSCs) in dissecting the interaction between ApoE and AD. First, we will provide an overview of the proposed roles that ApoE plays in modulating pathophysiology of AD. Next, we will summarize the recent studies that have employed hiPSCs to model familial and sporadic AD. Lastly, we will speculate on how current advances in genome editing technologies and organoid culture systems can be used to improve hiPSC-based tools to investigate ApoE-dependent modulation of AD onset and progression.
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Affiliation(s)
- Sreedevi Raman
- School of Biological and Health Systems Engineering, Arizona State University, United States of America
| | - Nicholas Brookhouser
- School of Biological and Health Systems Engineering, Arizona State University, United States of America; Graduate Program in Clinical Translational Sciences, University of Arizona College of Medicine-Phoenix, United States of America
| | - David A Brafman
- School of Biological and Health Systems Engineering, Arizona State University, United States of America.
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10
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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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11
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Muth C, Hartmann A, Sepulveda-Falla D, Glatzel M, Krasemann S. Phagocytosis of Apoptotic Cells Is Specifically Upregulated in ApoE4 Expressing Microglia in vitro. Front Cell Neurosci 2019; 13:181. [PMID: 31130847 PMCID: PMC6509203 DOI: 10.3389/fncel.2019.00181] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 04/12/2019] [Indexed: 01/08/2023] Open
Abstract
Alzheimer’s disease (AD) is characterized by intracellular tau aggregates and extracellular deposition of amyloid-β (Aβ). The major genetic risk factor to develop AD is the Apolipoprotein E isoform 4 (ApoE4). ApoE4 may directly affect Aβ pathology, yet the exact role of ApoE4 in the progression of AD remains unclear. Although astrocytes are the main source of ApoE in brain tissue, other cell types might contribute to ApoE isotype-dependent effects. While ApoE expression does not play a relevant role in homeostatic microglia, we and others could recently show that ApoE expression is significant upregulated in disease-associated microglia including AD-mouse models and human AD. ApoE has been supposed to have an anti-inflammatory effect, with ApoE4 being less effective than ApoE3. However, ApoE-isotype specific effects on microglia function in disease have not been thoroughly investigated to date. In contrast to this, the role of ApoE2, the third most common major ApoE isoform, in neurodegeneration has not been characterized in detail, but it has been shown to delay the onset of disease in familial AD. To elucidate the differential roles of the three-major human ApoE isoforms on microglia function we each expressed the human ApoE isoforms in murine N9 microglia cells. We could show that ApoE4 specifically influences actin cytoskeleton rearrangement and morphology. In migration assays, ApoE4 significantly promotes cell motility. To quantify phagocytosis by microglia we established an uptake assay based on imaging flow cytometry. Although expression of ApoE4 led to significantly reduced uptake of Aβ in contrast to the other isoforms, we could show that ApoE4 specifically increased phagocytosis of apoptotic neuronal cells. Our findings show that ApoE4 intrinsically affects microglia physiology by upregulating motility and phagocytic behavior in vitro and may therefore specifically contribute to microglia dysregulation in AD.
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Affiliation(s)
- Christiane Muth
- Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Alexander Hartmann
- Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Diego Sepulveda-Falla
- Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Markus Glatzel
- Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Susanne Krasemann
- Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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12
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Marais AD. Apolipoprotein E in lipoprotein metabolism, health and cardiovascular disease. Pathology 2018; 51:165-176. [PMID: 30598326 DOI: 10.1016/j.pathol.2018.11.002] [Citation(s) in RCA: 176] [Impact Index Per Article: 29.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 10/31/2018] [Accepted: 11/01/2018] [Indexed: 12/16/2022]
Abstract
Apolipoprotein E (apoE), a 34 kDa circulating glycoprotein of 299 amino acids, predominantly synthesised in the liver, associates with triglyceride-rich lipoproteins to mediate the clearance of their remnants after enzymatic lipolysis in the circulation. Its synthesis in macrophages initiates the formation of high density-like lipoproteins to effect reverse cholesterol transport to the liver. In the nervous system apoE forms similar lipoproteins which perform the function of distributing lipids amongst cells. ApoE accounts for much of the variation in plasma lipoproteins by three common variants (isoforms) that influence low-density lipoprotein concentration and the risk of atherosclerosis. ApoE2 generally is most favourable and apoE4 least favourable for cardiovascular and neurological health. The apoE variants relate to different amino acids at positions 112 and 158: cysteine in both for apoE2, arginine at both sites for apoE4, and respectively cysteine and arginine for apoE3 that is viewed as the wild type. Paradoxically, under metabolic stress, homozygosity for apoE2 may result in dysbetalipoproteinaemia in adults owing to impaired binding of remnant lipoproteins to the LDL receptor and related proteins as well as heparan sulphate proteoglycans. This highly atherogenic condition is also seen with other mutations in apoE, but with autosomal dominant inheritance. Mutations in apoE may also cause lipoprotein glomerulopathy. In the central nervous system apoE binds amyloid β-protein and tau protein and fragments may incur cellular damage. ApoE4 is a strong risk factor for the development of Alzheimer's disease. ApoE has several other physiological effects that may influence health and disease, including supply of docosahexaenoic acid for the brain and modulating immune and inflammatory responses. Genotyping of apoE may have application in disorders of lipoprotein metabolism as well as glomerulopathy and may be relevant to personalised medicine in understanding cardiovascular risk, and the outcome of nutritional and therapeutic interventions. Quantitation of apoE will probably not be clinically useful. ApoE is also of interest as it may generate peptides with biological function and could be employed in nanoparticles that may allow crossing of the blood-brain barrier. Therapeutic options may emerge from these newer insights.
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Affiliation(s)
- A David Marais
- Chemical Pathology Division, Pathology Department, University of Cape Town Health Science Faculty and National Health Laboratory Service, Cape Town, South Africa.
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13
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Dafnis I, Argyri L, Chroni A. Amyloid-peptide β 42 Enhances the Oligomerization and Neurotoxicity of apoE4: The C-terminal Residues Leu279, Lys282 and Gln284 Modulate the Structural and Functional Properties of apoE4. Neuroscience 2018; 394:144-155. [PMID: 30367942 DOI: 10.1016/j.neuroscience.2018.10.026] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 10/12/2018] [Accepted: 10/15/2018] [Indexed: 11/25/2022]
Abstract
Apolipoprotein E4 (apoE4), one of the three apoE isoforms, is the strongest factor for raising the risk for late-onset Alzheimer's disease (AD) and has been proposed to play a major role in AD pathogenesis. Amyloid-peptide β 42 (Aβ42) has also been proposed to affect neuronal degeneration and AD pathogenesis, possibly by interacting with apoE. Previous studies have shown that the functions of apoE forms can be dictated by their structural and biophysical properties. Here we show that apoE4 can form SDS-stable oligomers, possibly reflecting aggregated forms, which increase following incubation of apoE4 with Aβ42. In addition, extracellular apoE4 is cytotoxic for human neuroblastoma SK-N-SH cells, while Aβ42 enhances the cytotoxicity of apoE4. Carboxyl-terminal point mutations L279Q, K282A or Q284A reduced the capacity of apoE4 to form SDS-stable oligomers, as well as its cytotoxicity, both in the absence and presence of Aβ42. Structural and thermodynamic analyses showed that all three apoE4 mutants have significantly increased α-helical and decreased β-sheet content, have reduced portion of hydrophobic surfaces exposed to the solvent and have a reduced conformational stability during chemical denaturation. Overall, our data highlight a pathogenic role of apoE4 that could be linked to the capacity of the protein to form oligomeric species especially in the presence of Aβ42 and to induce cytotoxicity. Carboxyl-terminal residues L279, K282 or Q284 appear to be involved in the conformation of apoE4 that may underlie the protein's functional properties related to neurotoxicity.
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Affiliation(s)
- Ioannis Dafnis
- Institute of Biosciences and Applications, National Center for Scientific Research "Demokritos", Agia Paraskevi, Athens 15341, Greece
| | - Letta Argyri
- Institute of Biosciences and Applications, National Center for Scientific Research "Demokritos", Agia Paraskevi, Athens 15341, Greece
| | - Angeliki Chroni
- Institute of Biosciences and Applications, National Center for Scientific Research "Demokritos", Agia Paraskevi, Athens 15341, Greece.
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14
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Understanding the Role of ApoE Fragments in Alzheimer's Disease. Neurochem Res 2018; 44:1297-1305. [PMID: 30225748 DOI: 10.1007/s11064-018-2629-1] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 08/23/2018] [Accepted: 09/04/2018] [Indexed: 01/05/2023]
Abstract
Alzheimer's disease (AD) is one of the most devastating neurodegenerative diseases. It has been known for decades that the APOE ɛ4 allele is the most significant genetic risk factor for late-onset AD and yet its precise role in the disease remains unclear. The APOE gene encodes apolipoprotein E (apoE), a 35 kDa glycoprotein highly expressed in the brain. There are three different isoforms: apoE3 is the most common allele in the population, whilst apoE2 decreases, and apoE4 increases AD risk. ApoE has numerous functions that affect neuronal and non-neuronal cells, thus how it contributes to disease onset and progression is hotly debated. The apoE4 isoform has been linked to the accumulation of both of the major pathological hallmarks of AD, amyloid plaques containing amyloid β peptides, and neurofibrillary tangles containing hyperphosphorylated tau protein, as well as other hallmarks of the disease, including inflammation and oxidative stress. Numerous studies have shown that apoE undergoes fragmentation in the human brain, and that the fragmentation pattern varies between isoforms. It was previously shown that apoE4 has neurotoxic functions, however recent data has also identified a neuroprotective role for the apoE N-terminal 25 kDa fragment, which is more prevalent in apoE3 individuals. The ability of the apoE 25 kDa fragment to promote neurite outgrowth was recently demonstrated and this suggests there is a potential loss of neuroprotection in apoE4 individuals in addition to the previously described gain of toxic function for specific apoE4 fragments. Here we review the enzymes proposed to be responsible for apoE fragmentation, the specific functions of different apoE fragments and their possible links with AD.
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15
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Hu Z, Yang Y, Zhao Y, Yu H, Ying X, Zhou D, Zhong J, Zheng Z, Liu J, Pan R, Zhang W, Cheng F, Duan S. APOE hypermethylation is associated with autism spectrum disorder in a Chinese population. Exp Ther Med 2018; 15:4749-4754. [PMID: 29844799 PMCID: PMC5958870 DOI: 10.3892/etm.2018.6069] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 03/01/2018] [Indexed: 12/27/2022] Open
Abstract
Abnormal apolipoprotein E (APOE) methylation has been demonstrated to be associated with Alzheimer's disease, which may have overlapping mechanisms with autism spectrum disorder (ASD). Thus, the purpose of the present study was to assess the possible link between APOE methylation and ASD. Genomic DNA was extracted from peripheral blood and subjected to a methylation assay. SYBR green-based quantitative methylation-specific polymerase chain reaction analysis was used to measure APOE methylation in 62 pediatric patients with ASD and 73 age-matched healthy subjects. The APOE methylation in each sample was expressed as a percentage of methylation of a reference (PMR). The results indicated that APOE methylation in pediatric patients with ASD was significantly higher than that in the healthy controls (median PMR, 33 vs. 11%; P=2.36×10−10). Receiver operating characteristic curve demonstrated that PMR of 15.4% was the optimal cut-off for predicting ASD (area under curve, 0.817; sensitivity, 93.5%; specificity, 72.6%; P=2.36×10−10). In summary, the present results indicated that APOE hypermethylation in peripheral blood DNA may be used as a diagnostic biomarker for ASD.
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Affiliation(s)
- Zhenyu Hu
- Department of Child Psychiatry, Ningbo Kangning Hospital, Ningbo University, Ningbo, Zhejiang 315211, P.R. China
| | - Yong Yang
- Zhejiang Provincial Key Laboratory of Pathophysiology, Medical Genetics Center, School of Medicine, Ningbo University, Ningbo, Zhejiang 315211, P.R. China
| | - Yuanzhi Zhao
- Department of Child Psychiatry, Ningbo Kangning Hospital, Ningbo University, Ningbo, Zhejiang 315211, P.R. China
| | - Hang Yu
- Zhejiang Provincial Key Laboratory of Pathophysiology, Medical Genetics Center, School of Medicine, Ningbo University, Ningbo, Zhejiang 315211, P.R. China
| | - Xiuru Ying
- Zhejiang Provincial Key Laboratory of Pathophysiology, Medical Genetics Center, School of Medicine, Ningbo University, Ningbo, Zhejiang 315211, P.R. China
| | - Dongsheng Zhou
- Department of Child Psychiatry, Ningbo Kangning Hospital, Ningbo University, Ningbo, Zhejiang 315211, P.R. China
| | - Jie Zhong
- Zhejiang Provincial Key Laboratory of Pathophysiology, Medical Genetics Center, School of Medicine, Ningbo University, Ningbo, Zhejiang 315211, P.R. China
| | - Zhonghua Zheng
- Zhejiang Provincial Key Laboratory of Pathophysiology, Medical Genetics Center, School of Medicine, Ningbo University, Ningbo, Zhejiang 315211, P.R. China
| | - Jing Liu
- Zhejiang Provincial Key Laboratory of Pathophysiology, Medical Genetics Center, School of Medicine, Ningbo University, Ningbo, Zhejiang 315211, P.R. China
| | - Ranran Pan
- Zhejiang Provincial Key Laboratory of Pathophysiology, Medical Genetics Center, School of Medicine, Ningbo University, Ningbo, Zhejiang 315211, P.R. China
| | - Wenwu Zhang
- Department of Child Psychiatry, Ningbo Kangning Hospital, Ningbo University, Ningbo, Zhejiang 315211, P.R. China
| | - Fang Cheng
- Department of Child Psychiatry, Ningbo Kangning Hospital, Ningbo University, Ningbo, Zhejiang 315211, P.R. China
| | - Shiwei Duan
- Zhejiang Provincial Key Laboratory of Pathophysiology, Medical Genetics Center, School of Medicine, Ningbo University, Ningbo, Zhejiang 315211, P.R. China
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16
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Muñoz SS, Li H, Ruberu K, Chu Q, Saghatelian A, Ooi L, Garner B. The serine protease HtrA1 contributes to the formation of an extracellular 25-kDa apolipoprotein E fragment that stimulates neuritogenesis. J Biol Chem 2018; 293:4071-4084. [PMID: 29414786 PMCID: PMC5857987 DOI: 10.1074/jbc.ra117.001278] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 01/24/2018] [Indexed: 12/31/2022] Open
Abstract
Apolipoprotein-E (apoE) is a glycoprotein highly expressed in the brain, where it appears to play a role in lipid transport, β-amyloid clearance, and neuronal signaling. ApoE proteolytic fragments are also present in the brain, but the enzymes responsible for apoE fragmentation are unknown, and the biological activity of specific apoE fragments remains to be determined. Here we utilized SK-N-SH neuroblastoma cells differentiated into neurons with all-trans-retinoic acid (ATRA) to study extracellular apoE proteolysis. ApoE fragments were detectable in culture supernatants after 3 days, and their levels were increased for up to 9 days in the presence of ATRA. The concentration of apoE fragments was positively correlated with levels of the neuronal maturation markers (PSD95 and SMI32). The most abundant apoE fragments were 25- and 28-kDa N-terminal fragments that both contained sialylated glycosylation and bound to heparin. We detected apoE fragments only in the extracellular milieu and not in cell lysates, suggesting that an extracellular protease contributes to apoE fragmentation. Of note, siRNA-mediated knockdown of high-temperature requirement serine peptidase A1 (HtrA1) and a specific HtrA1 inhibitor reduced apoE 25-kDa fragment formation by 41 and 86%, respectively. Recombinant 25-kDa fragment apoE and full-length apoE both stimulated neuritogenesis in vitro, increasing neuroblastoma neurite growth by more than 2-fold over a 6-day period. This study provides a cellular model for assessing apoE proteolysis, indicates that HtrA1 regulates apoE 25-kDa fragment formation under physiological conditions, and reveals a new neurotrophic function for the apoE 25-kDa fragment.
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Affiliation(s)
- Sonia Sanz Muñoz
- From the Illawarra Health and Medical Research Institute and
- the School of Biological Sciences, University of Wollongong, New South Wales 2522, Australia and
| | - Hongyun Li
- From the Illawarra Health and Medical Research Institute and
- the School of Biological Sciences, University of Wollongong, New South Wales 2522, Australia and
| | - Kalani Ruberu
- From the Illawarra Health and Medical Research Institute and
- the School of Biological Sciences, University of Wollongong, New South Wales 2522, Australia and
| | - Qian Chu
- the Clayton Foundation Laboratories for Peptide Biology, Salk Institute for Biological Studies, La Jolla, California 92037
| | - Alan Saghatelian
- the Clayton Foundation Laboratories for Peptide Biology, Salk Institute for Biological Studies, La Jolla, California 92037
| | - Lezanne Ooi
- From the Illawarra Health and Medical Research Institute and
- the School of Biological Sciences, University of Wollongong, New South Wales 2522, Australia and
| | - Brett Garner
- From the Illawarra Health and Medical Research Institute and
- the School of Biological Sciences, University of Wollongong, New South Wales 2522, Australia and
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17
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Patra K, Soosaipillai A, Sando SB, Lauridsen C, Berge G, Møller I, Grøntvedt GR, Bråthen G, Begcevic I, Moussaud S, Minthon L, Hansson O, Diamandis EP, White LR, Nielsen HM. Assessment of kallikrein 6 as a cross-sectional and longitudinal biomarker for Alzheimer's disease. ALZHEIMERS RESEARCH & THERAPY 2018; 10:9. [PMID: 29378650 PMCID: PMC5789599 DOI: 10.1186/s13195-018-0336-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Accepted: 01/04/2018] [Indexed: 11/15/2022]
Abstract
Background Kallikrein 6 (KLK6) is known to be an age-related protease expressed at high levels in the central nervous system. It was previously shown to be involved in proteolysis of extracellular proteins implicated in neurodegenerative diseases such as Alzheimer’s disease (AD), prompting validation of KLK6 as a potential biomarker of disease. However, analyses of both plasma and cerebrospinal fluid (CSF) levels of KLK6 in patients with AD have been inconclusive. We present a detailed analysis of KLK6 in plasma and CSF in two separate cohorts in a cross-sectional and a longitudinal clinical setting. Methods The cross-sectional cohort included control subjects without dementia and patients with AD, and the longitudinal cohort included patients with MCI and patients with AD followed over a 2-year period. Plasma and CSF levels of KLK6 were quantified by use of a previously developed and validated enzyme-linked immunosorbent assay. Statistical analyses were performed to compare KLK6 levels between diagnostic groups and to identify potential associations between KLK6 level, age, apolipoprotein E (APOE) genotype, total apoE level and the classical CSF AD biomarkers. Results In the cross-sectional setting, KLK6 levels in plasma but not in CSF were significantly higher in the AD group than in control subjects. CSF but not plasma KLK6 levels were positively correlated with age in both the cross-sectional and longitudinal settings. In both cohorts, the CSF KLK6 levels were significantly and positively correlated with the CSF levels of core AD biomarkers. Total plasma and CSF apoE levels were positively associated with KLK6 in the cross-sectional study. Finally, during the 2-year monitoring period of the longitudinal cohort, CSF KLK6 levels increased with disease progression over time in the investigated patient groups. Conclusions In two separate cohorts we have confirmed the previously reported correlation between age and CSF levels of KLK6. Increased plasma KLK6 levels in patients with AD with a more advanced disease stage suggest KLK6 as a potential biomarker in patients with AD with more severe dementia. Significant correlations between KLK6 levels and core CSF AD biomarkers suggest molecular links between KLK6 and AD-related pathological processes.
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Affiliation(s)
- Kalicharan Patra
- Department of Neurochemistry, Stockholm University, Svante Arrhenius väg 16B, 106 91, Stockholm, Sweden
| | - Antoninus Soosaipillai
- Department of Pathology and Laboratory Medicine, Lunenfeld-Tanenbaum Research Institute-Mount Sinai Hospital, Toronto, ON, Canada
| | - Sigrid Botne Sando
- Department of Neurology, University Hospital of Trondheim, Trondheim, Norway.,Department of Neuromedicine and Movement Science, Norwegian University of Science and Technology, Trondheim, Norway
| | - Camilla Lauridsen
- Department of Neuromedicine and Movement Science, Norwegian University of Science and Technology, Trondheim, Norway
| | - Guro Berge
- Department of Neuromedicine and Movement Science, Norwegian University of Science and Technology, Trondheim, Norway
| | - Ina Møller
- Department of Neuromedicine and Movement Science, Norwegian University of Science and Technology, Trondheim, Norway
| | - Gøril Rolfseng Grøntvedt
- Department of Neuromedicine and Movement Science, Norwegian University of Science and Technology, Trondheim, Norway
| | - Geir Bråthen
- Department of Neurology, University Hospital of Trondheim, Trondheim, Norway.,Department of Neuromedicine and Movement Science, Norwegian University of Science and Technology, Trondheim, Norway
| | - Ilijana Begcevic
- Department of Pathology and Laboratory Medicine, Lunenfeld-Tanenbaum Research Institute-Mount Sinai Hospital, Toronto, ON, Canada
| | - Simon Moussaud
- Department of Neurochemistry, Stockholm University, Svante Arrhenius väg 16B, 106 91, Stockholm, Sweden
| | - Lennart Minthon
- Department of Clinical Sciences, Lund University, Lund, Sweden
| | - Oskar Hansson
- Department of Clinical Sciences, Lund University, Lund, Sweden
| | - Eleftherios P Diamandis
- Department of Pathology and Laboratory Medicine, Lunenfeld-Tanenbaum Research Institute-Mount Sinai Hospital, Toronto, ON, Canada
| | - Linda R White
- Department of Neurology, University Hospital of Trondheim, Trondheim, Norway.,Department of Neuromedicine and Movement Science, Norwegian University of Science and Technology, Trondheim, Norway
| | - Henrietta M Nielsen
- Department of Neurochemistry, Stockholm University, Svante Arrhenius väg 16B, 106 91, Stockholm, Sweden.
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18
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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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19
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Abstract
PURPOSE OF REVIEW APOE4 genotype is the strongest genetic risk factor for Alzheimer's disease. Prevailing evidence suggests that amyloid β plays a critical role in Alzheimer's disease. The objective of this article is to review the recent findings about the metabolism of apolipoprotein E (ApoE) and amyloid β and other possible mechanisms by which ApoE contributes to the pathogenesis of Alzheimer's disease. RECENT FINDINGS ApoE isoforms have differential effects on amyloid β metabolism. Recent studies demonstrated that ApoE-interacting proteins, such as ATP-binding cassette A1 (ABCA1) and LDL receptor, may be promising therapeutic targets for Alzheimer's disease treatment. Activation of liver X receptor and retinoid X receptor pathway induces ABCA1 and other genes, leading to amyloid β clearance. Inhibition of the negative regulators of ABCA1, such as microRNA-33, also induces ABCA1 and decreases the levels of ApoE and amyloid β. In addition, genetic inactivation of an E3 ubiquitin ligase, myosin regulatory light chain interacting protein, increases LDL receptor levels and inhibits amyloid accumulation. Although amyloid β-dependent pathways have been extensively investigated, there have been several recent studies linking ApoE with vascular function, neuroinflammation, metabolism, synaptic plasticity, and transcriptional regulation. For example, ApoE was identified as a ligand for a microglial receptor, TREM2, and studies suggested that ApoE may affect the TREM2-mediated microglial phagocytosis. SUMMARY Emerging data suggest that ApoE affects several amyloid β-independent pathways. These underexplored pathways may provide new insights into Alzheimer's disease pathogenesis. However, it will be important to determine to what extent each mechanism contributes to the pathogenesis of Alzheimer's disease.
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Affiliation(s)
- Fan Liao
- Department of Neurology, Washington University School of Medicine, St. Louis, Missouri
| | - Hyejin Yoon
- Neurobiology of Disease Graduate Program, Mayo Graduate School
- Department of Neuroscience, Mayo Clinic, Jacksonville, Florida, USA
| | - Jungsu Kim
- Neurobiology of Disease Graduate Program, Mayo Graduate School
- Department of Neuroscience, Mayo Clinic, Jacksonville, Florida, USA
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20
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Chu Q, Diedrich JK, Vaughan JM, Donaldson CJ, Nunn MF, Lee KF, Saghatelian A. HtrA1 Proteolysis of ApoE In Vitro Is Allele Selective. J Am Chem Soc 2016; 138:9473-8. [PMID: 27379525 PMCID: PMC5063305 DOI: 10.1021/jacs.6b03463] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Apolipoprotein E (ApoE) belongs to a large class of proteins that solubilize lipids for physiological transport. Humans have three different APOE alleles, APOE ε2, APOE ε3, and APOE ε4, and genetic studies identified ApoE4 as the strongest genetic risk factor for Alzheimer's disease (AD). People who are homozygous for ApoE4 (i.e., ApoE4/E4) are an order of magnitude more likely to develop late-onset AD (LOAD) than ApoE3/E3 carriers. Several differences between ApoE3 and ApoE4 may contribute to AD including the observation that ApoE4 is degraded to a greater extent than ApoE3 in the human brain. Experiments with high-temperature requirement serine peptidase A1 (HtrA1), which is found in the nervous system, demonstrate that HtrA1 is an allele-selective ApoE-degrading enzyme that degrades ApoE4 more quickly than ApoE3. This activity is specific to HtrA1, as similar assays with HtrA2 showed minimal ApoE4 proteolysis and trypsin had no preference between ApoE4 and ApoE3. HtrA1 has also been reported to cleave the tau protein (Tau) and the amyloid protein precursor (APP) to hinder the formation of toxic amyloid deposits associated with AD. Competition assays with ApoE4, ApoE3, and Tau revealed that ApoE4 inhibits Tau degradation. Thus, the identification of ApoE4 as an in vitro HtrA1 substrate suggests a potential biochemical mechanism that links ApoE4 regulation of AD proteins such as Tau.
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Affiliation(s)
- Qian Chu
- The Salk Institute for Biological Studies, Clayton Foundation Laboratories for Peptide Biology, 10010 N. Torrey Pines Rd, La Jolla, CA 92037, USA
| | - Jolene K. Diedrich
- The Salk Institute for Biological Studies, Clayton Foundation Laboratories for Peptide Biology, 10010 N. Torrey Pines Rd, La Jolla, CA 92037, USA
- Department of Chemical Physiology, The Scripps Research Institute, 10550 N. Torrey Pines Rd, La Jolla, CA 92037, USA
| | - Joan M. Vaughan
- The Salk Institute for Biological Studies, Clayton Foundation Laboratories for Peptide Biology, 10010 N. Torrey Pines Rd, La Jolla, CA 92037, USA
| | - Cynthia J. Donaldson
- The Salk Institute for Biological Studies, Clayton Foundation Laboratories for Peptide Biology, 10010 N. Torrey Pines Rd, La Jolla, CA 92037, USA
| | - Michael F. Nunn
- The Salk Institute for Biological Studies, Clayton Foundation Laboratories for Peptide Biology, 10010 N. Torrey Pines Rd, La Jolla, CA 92037, USA
| | - Kuo-Fen Lee
- The Salk Institute for Biological Studies, Clayton Foundation Laboratories for Peptide Biology, 10010 N. Torrey Pines Rd, La Jolla, CA 92037, USA
| | - Alan Saghatelian
- The Salk Institute for Biological Studies, Clayton Foundation Laboratories for Peptide Biology, 10010 N. Torrey Pines Rd, La Jolla, CA 92037, USA
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21
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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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22
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Washington PM, Burns MP. The Effect of the APOE4 Gene on Accumulation of Aβ40 After Brain Injury Cannot Be Reversed by Increasing apoE4 Protein. J Neuropathol Exp Neurol 2016; 75:770-778. [PMID: 27297672 PMCID: PMC7299436 DOI: 10.1093/jnen/nlw049] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The apolipoprotein E (apoE) protein is involved in clearance of β-amyloid (Aβ) from the brain; and the APOE4 gene is associated with Aβ plaque formation in humans following traumatic brain injury (TBI). Here, we examined the association between apoE and Aβ40 after experimental TBI and the effects of APOE alleles on this relationship. We report a biphasic response of soluble apoE protein after TBI with an acute reduction at 1 day postinjury followed by an increase at 7 days postinjury. TBI-induced Aβ40 levels decreased as soluble apoE levels increased. In APOE4 mice there was a diminished apoE response to TBI that corresponded to prolonged accumulation of TBI-induced Aβ40 versus that in APOE3 mice. Amyloid precursor protein processing was similar in APOE3 and APOE4 mice suggesting that impaired clearance was responsible for the abnormal accumulation of Aβ40 in the latter. Treatment of APOE4 mice with bexarotene for 7 days increased apoE4 protein levels but was not sufficient to reduce TBI-induced Aβ40 Thus, rapid clearance of TBI-induced Aβ40 occurs in mice but these pathways are impaired in APOE4 carriers. These data may help explain the deposition of Aβ in APOE4 carriers and the increased incidence of brain Aβ plaques following TBI.
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Affiliation(s)
- Patricia M Washington
- From the Laboratory for Brain Injury and Dementia, Department of Neuroscience, Georgetown University Medical Center, Washington, DC (PM, MB)
| | - Mark P Burns
- From the Laboratory for Brain Injury and Dementia, Department of Neuroscience, Georgetown University Medical Center, Washington, DC (PM, MB).
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23
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ApoE4-specific Misfolded Intermediate Identified by Molecular Dynamics Simulations. PLoS Comput Biol 2015; 11:e1004359. [PMID: 26506597 PMCID: PMC4623519 DOI: 10.1371/journal.pcbi.1004359] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Accepted: 05/28/2015] [Indexed: 11/19/2022] Open
Abstract
The increased risk of developing Alzheimer's disease (AD) is associated with the APOE gene, which encodes for three variants of Apolipoprotein E, namely E2, E3, E4, differing only by two amino acids at positions 112 and 158. ApoE4 is known to be the strongest risk factor for AD onset, while ApoE3 and ApoE2 are considered to be the AD-neutral and AD-protective isoforms, respectively. It has been hypothesized that the ApoE isoforms may contribute to the development of AD by modifying the homeostasis of ApoE physiological partners and AD-related proteins in an isoform-specific fashion. Here we find that, despite the high sequence similarity among the three ApoE variants, only ApoE4 exhibits a misfolded intermediate state characterized by isoform-specific domain-domain interactions in molecular dynamics simulations. The existence of an ApoE4-specific intermediate state can contribute to the onset of AD by altering multiple cellular pathways involved in ApoE-dependent lipid transport efficiency or in AD-related protein aggregation and clearance. We present what we believe to be the first structural model of an ApoE4 misfolded intermediate state, which may serve to elucidate the molecular mechanism underlying the role of ApoE4 in AD pathogenesis. The knowledge of the structure for the ApoE4 folding intermediate provides a new platform for the rational design of alternative therapeutic strategies to fight AD.
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24
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Dafnis I, Metso J, Zannis VI, Jauhiainen M, Chroni A. Influence of Isoforms and Carboxyl-Terminal Truncations on the Capacity of Apolipoprotein E To Associate with and Activate Phospholipid Transfer Protein. Biochemistry 2015; 54:5856-66. [PMID: 26337529 DOI: 10.1021/acs.biochem.5b00681] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Phospholipid transfer protein (PLTP), a main protein in lipid and lipoprotein metabolism, exists in high-activity (HA-PLTP) and low-activity (LA-PLTP) forms in human plasma. Proper phospholipid transfer activity of PLTP is modulated by interactions with various apolipoproteins (apo) including apoE. The domains of apoE involved in interactions with PLTP are not known. Here we analyzed the capacity of recombinant apoE isoforms and apoE4 mutants with progressive carboxyl-terminal deletions to bind to and activate HA-PLTP and LA-PLTP. Our analyses demonstrated that lipid-free apoE isoforms bind to both HA-PLTP and LA-PLTP, resulting in phospholipid transfer activation, with apoE3 inducing the highest PLTP activation. The isoform-specific differences in apoE/PLTP binding and PLTP activation were abolished following apoE lipidation. Lipid-free apoE4[Δ(260-299)], apoE4[Δ(230-299)], apoE4[Δ(203-299)], and apoE4[Δ(186-299)] activated HA-PLTP by 120-160% compared to full-length apoE4. Lipid-free apoE4[Δ(186-299)] also activated LA-PLTP by 85% compared to full-length apoE4. All lipidated truncated apoE4 forms displayed a similar effect on HA-PLTP and LA-PLTP activity as full-length apoE4. Strikingly, lipid-free or lipidated full-length apoE4 and apoE4[Δ(186-299)] demonstrated similar binding capacity to LA-PLTP and HA-PLTP. Biophysical studies showed that the carboxyl-terminal truncations of apoE4 resulted in small changes of the structural or thermodynamic properties of lipidated apoE4, that were much less pronounced compared to changes observed previously for lipid-free apoE4. Overall, our findings show an isoform-dependent binding to and activation of PLTP by lipid-free apoE. Furthermore, the domain of apoE4 required for PLTP activation resides within its amino-terminal 1-185 region. The apoE/PLTP interactions can be modulated by the conformation and lipidation state of apoE.
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Affiliation(s)
- Ioannis Dafnis
- Institute of Biosciences and Applications, National Center for Scientific Research "Demokritos" , Agia Paraskevi 15310, Athens, Greece
| | - Jari Metso
- Genomics and Biomarkers Unit, Biomedicum, National Institute for Health and Welfare , Helsinki 00290, Finland
| | - Vassilis I Zannis
- Departments of Medicine and Biochemistry, Molecular Genetics, Whitaker Cardiovascular Institute, Boston University School of Medicine , Boston, Massachusetts 02118, United States
| | - Matti Jauhiainen
- Genomics and Biomarkers Unit, Biomedicum, National Institute for Health and Welfare , Helsinki 00290, Finland
| | - Angeliki Chroni
- Institute of Biosciences and Applications, National Center for Scientific Research "Demokritos" , Agia Paraskevi 15310, Athens, Greece
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25
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Xu H, Gupta VB, Martins IJ, Martins RN, Fowler CJ, Bush AI, Finkelstein DI, Adlard PA. Zinc affects the proteolytic stability of Apolipoprotein E in an isoform-dependent way. Neurobiol Dis 2015; 81:38-48. [PMID: 26117305 DOI: 10.1016/j.nbd.2015.06.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2014] [Revised: 05/26/2015] [Accepted: 06/21/2015] [Indexed: 11/29/2022] Open
Abstract
The pathological role of zinc in Alzheimer's disease (AD) is not yet fully elucidated, but there is strong evidence that zinc homeostasis is impaired in the AD brain and that this contributes to disease pathogenesis. In this study we examined the effects of zinc on the proteolysis of synthetic Apolipoprotein E (ApoE), a protein whose allelic variants differentially contribute to the onset/progression of disease. We have demonstrated that zinc promotes the proteolysis (using plasma kallikrein, thrombin and chymotrypsin) of synthetic ApoE in an isoform-specific way (E4>E2 and E3), resulting in more ApoE fragments, particularly for ApoE4. In the absence of exogenous proteases there was no effect of metal modulation on either lipidated or non-lipidated ApoE isoforms. Thus, increased zinc in the complex milieu of the ageing and AD brain could reduce the level of normal full-length ApoE and increase other forms that are involved in neurodegeneration. We further examined human plasma samples from people with different ApoE genotypes. Consistent with previous studies, plasma ApoE levels varied according to different genotypes, with ApoE2 carriers showing the highest total ApoE levels and ApoE4 carriers the lowest. The levels of plasma ApoE were not affected by either the addition of exogenous metals (copper, zinc or iron) or by chelation. Taken together, our study reveals that zinc may contribute to the pathogenesis of AD by affecting the proteolysis of ApoE, which to some extent explains why APOE4 carriers are more susceptible to AD.
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Affiliation(s)
- He Xu
- The Florey Institute of Neuroscience and Mental Health, Melbourne, Victoria 3010, Australia
| | - Veer B Gupta
- Centre of Excellence for Alzheimer's Disease Research and Care, School of Medical Sciences, Edith Cowan University, 270 Joondalup Drive, Joondalup, 6027 WA, Australia
| | - Ian J Martins
- Centre of Excellence for Alzheimer's Disease Research and Care, School of Medical Sciences, Edith Cowan University, 270 Joondalup Drive, Joondalup, 6027 WA, Australia
| | - Ralph N Martins
- Centre of Excellence for Alzheimer's Disease Research and Care, School of Medical Sciences, Edith Cowan University, 270 Joondalup Drive, Joondalup, 6027 WA, Australia
| | - Christopher J Fowler
- The Florey Institute of Neuroscience and Mental Health, Melbourne, Victoria 3010, Australia
| | - Ashley I Bush
- The Florey Institute of Neuroscience and Mental Health, Melbourne, Victoria 3010, Australia
| | - David I Finkelstein
- The Florey Institute of Neuroscience and Mental Health, Melbourne, Victoria 3010, Australia
| | - Paul A Adlard
- The Florey Institute of Neuroscience and Mental Health, Melbourne, Victoria 3010, Australia.
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26
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Inekci D, Jonesco DS, Kennard S, Karsdal MA, Henriksen K. The potential of pathological protein fragmentation in blood-based biomarker development for dementia - with emphasis on Alzheimer's disease. Front Neurol 2015; 6:90. [PMID: 26029153 PMCID: PMC4426721 DOI: 10.3389/fneur.2015.00090] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Accepted: 04/10/2015] [Indexed: 12/12/2022] Open
Abstract
The diagnosis of dementia is challenging and early stages are rarely detected limiting the possibilities for early intervention. Another challenge is the overlap in the clinical features across the different dementia types leading to difficulties in the differential diagnosis. Identifying biomarkers that can detect the pre-dementia stage and allow differential diagnosis could provide an opportunity for timely and optimal intervention strategies. Also, such biomarkers could help in selection and inclusion of the right patients in clinical trials of both Alzheimer’s disease and other dementia treatment candidates. The cerebrospinal fluid (CSF) has been the most investigated source of biomarkers and several candidate proteins have been identified. However, looking solely at protein levels is too simplistic to provide enough detailed information to differentiate between dementias, as there is a significant crossover between the proteins involved in the different types of dementia. Additionally, CSF sampling makes these biomarkers challenging for presymptomatic identification. We need to focus on disease-specific protein fragmentation to find a fragment pattern unique for each separate dementia type – a form of protein fragmentology. Targeting protein fragments generated by disease-specific combinations of proteins and proteases opposed to detecting the intact protein could reduce the overlap between diagnostic groups as the extent of processing as well as which proteins and proteases constitute the major hallmark of each dementia type differ. In addition, the fragments could be detectable in blood as they may be able to cross the blood–brain barrier due to their smaller size. In this review, the potential of the fragment-based biomarker discovery for dementia diagnosis and prognosis is discussed, especially highlighting how the knowledge from CSF protein biomarkers can be used to guide blood-based biomarker development.
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Affiliation(s)
- Dilek Inekci
- Nordic Bioscience, Biomarkers and Research , Herlev , Denmark ; Systems Biology, Technical University of Denmark , Lyngby , Denmark
| | | | - Sophie Kennard
- Nordic Bioscience, Biomarkers and Research , Herlev , Denmark
| | | | - Kim Henriksen
- Nordic Bioscience, Biomarkers and Research , Herlev , Denmark
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27
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Suenaga M, Furuta A, Wakabayashi K, Saibara T, Matsunaga Y. Monocytic elastase-mediated apolipoprotein-E degradation: Potential involvement of microglial elastase-like proteases in apolipoprotein-E proteolysis in brains with Alzheimers disease. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2015; 1854:1010-8. [PMID: 25956321 DOI: 10.1016/j.bbapap.2015.04.028] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 04/09/2015] [Accepted: 04/28/2015] [Indexed: 01/07/2023]
Abstract
Impaired clearance of soluble Aβ (amyloid-β) promotes Aβ aggregation in brains with Alzheimer's disease (AD), while apolipoprotein-E (ApoE) in microglia mediates Aβ clearance. We studied the protease responsible for ApoE(4) degradation in human peripheral monocyte extracts, which are from the same lineage as microglia. We detected the hydrolytic activity for ApoE(4) in high-salt extracts with 2 M NaCl and found that the activity was inhibited by a serine protease inhibitor and an elastase-specific inhibitor, but not by other protease inhibitors. The extracts exhibited higher activity for the elastase substrate, and we followed the activity with ion-exchange and gel-filtration chromatography. Through silver staining, we partially purified a protein of 28 kDa, which was clarified as elastase by liquid chromatography-tandem mass spectrometry. These observations suggest that elastase is the key protease for ApoE(4) degradation. We also detected ApoE(4) hydrolytic activity in high-salt extracts in mouse microglial (BV-2) cell lysates, and showed that the ApoE(4) fragments by the BV-2 extracts differed from the fragments by the monocyte extracts. Though the ApoE(4) degradation by the extracts was not inhibited with elastase-specific inhibitors, it was inhibited by an elastase-specific monoclonal antibody, suggesting that elastase-like proteases in microglia differ from those of monocytes. Immunohistochemistry revealed that both elastase and ApoE were expressed in the senile plaques of brains with AD. In vitro studies also disclosed the localization of elastase in the microglial cell line, BV-2. Our results suggest that elastase-like proteases in the microglial cells surrounding Aβ plaques are responsible for ApoE degradation in the brain.
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Affiliation(s)
- Midori Suenaga
- Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Nishihama, Yamashiro-cho, Tokushima 770-8514, Japan
| | - Akiko Furuta
- Department of Cellular and Molecular Neuropathology, Juntendo University, School of Medicine, Hongo 2-1-1, Bunkyou-ku, Tokyo 113-8421, Japan
| | - Koichi Wakabayashi
- Department of Neuropathology, Institute of Brain Science, Hirosaki University, Graduate School of Medicine, 5 Zaifu-cho, Hirosaki 036-8562, Japan
| | - Toshiji Saibara
- Department of Gastroenterology and Hepatology, Kochi Medical School, Kochi University, Nankoku, Kochi 783-8505, Japan
| | - Yoichi Matsunaga
- Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Nishihama, Yamashiro-cho, Tokushima 770-8514, Japan.
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28
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Divekar SD, Burrell TC, Lee JE, Weeber EJ, Rebeck GW. Ligand-induced homotypic and heterotypic clustering of apolipoprotein E receptor 2. J Biol Chem 2014; 289:15894-903. [PMID: 24755222 DOI: 10.1074/jbc.m113.537548] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
ApoE Receptor 2 (ApoER2) and the very low density lipoprotein receptor (VLDLR) are type I transmembrane proteins belonging to the LDLR family of receptors. They are neuronal proteins found in synaptic compartments that play an important role in neuronal migration during development. ApoER2 and VLDLR bind to extracellular glycoproteins, such as Reelin and F-spondin, which leads to phosphorylation of adaptor proteins and subsequent activation of downstream signaling pathways. It is thought that ApoER2 and VLDLR undergo clustering upon binding to their ligands, but no direct evidence of clustering has been shown. Here we show strong clustering of ApoER2 induced by the dimeric ligands Fc-RAP, F-spondin, and Reelin but relatively weak clustering with the ligand apoE in the absence of lipoproteins. This clustering involves numerous proteins besides ApoER2, including amyloid precursor protein and the synaptic adaptor protein PSD-95. Interestingly, we did not observe strong clustering of ApoER2 with VLDLR. Clustering was modulated by both extracellular and intracellular domains of ApoER2. Together, our data demonstrate that several multivalent ligands for ApoER2 induce clustering in transfected cells and primary neurons and that these complexes included other synaptic molecules, such as APP and PSD-95.
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Affiliation(s)
- Shailaja D Divekar
- From the Department of Neuroscience, Georgetown University Medical Center, Washington, D. C. 20007 and
| | - Teal C Burrell
- From the Department of Neuroscience, Georgetown University Medical Center, Washington, D. C. 20007 and
| | - Jennifer E Lee
- From the Department of Neuroscience, Georgetown University Medical Center, Washington, D. C. 20007 and
| | - Edwin J Weeber
- the Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, Florida 33613
| | - G William Rebeck
- From the Department of Neuroscience, Georgetown University Medical Center, Washington, D. C. 20007 and
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