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Lin EY, Hsu SX, Wu BH, Deng YC, Wuli W, Li YS, Lee JH, Lin SZ, Harn HJ, Chiou TW. Engineered Exosomes Containing microRNA-29b-2 and Targeting the Somatostatin Receptor Reduce Presenilin 1 Expression and Decrease the β-Amyloid Accumulation in the Brains of Mice with Alzheimer's Disease. Int J Nanomedicine 2024; 19:4977-4994. [PMID: 38828204 PMCID: PMC11144417 DOI: 10.2147/ijn.s442876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Accepted: 04/26/2024] [Indexed: 06/05/2024] Open
Abstract
Purpose Exosomes are membrane vesicles secreted by various cells and play a crucial role in intercellular communication. They can be excellent delivery vehicles for oligonucleotide drugs, such as microRNAs, due to their high biocompatibility. MicroRNAs have been shown to be more stable when incorporated into exosomes; however, the lack of targeting and immune evasion is still the obstacle to the use of these microRNA-containing nanocarriers in clinical settings. Our goal was to produce functional exosomes loaded with target ligands, immune evasion ligand, and oligonucleotide drug through genetic engineering in order to achieve more precise medical effects. Methods To address the problem, we designed engineered exosomes with exogenous cholecystokinin (CCK) or somatostatin (SST) as the targeting ligand to direct the exosomes to the brain, as well as transduced CD47 proteins to reduce the elimination or phagocytosis of the targeted exosomes. MicroRNA-29b-2 was the tested oligonucleotide drug for delivery because our previous research showed that this type of microRNA was capable of reducing presenilin 1 (PSEN1) gene expression and decreasing the β-amyloid accumulation for Alzheimer's disease (AD) in vitro and in vivo. Results The engineered exosomes, containing miR29b-2 and expressing SST and CD47, were produced by gene-modified dendritic cells and used in the subsequent experiments. In comparison with CD47-CCK exosomes, CD47-SST exosomes showed a more significant increase in delivery efficiency. In addition, CD47-SST exosomes led to a higher delivery level of exosomes to the brains of nude mice when administered intravenously. Moreover, it was found that the miR29b-2-loaded CD47-SST exosomes could effectively reduce PSEN1 in translational levels, which resulted in an inhibition of beta-amyloid oligomers production both in the cell model and in the 3xTg-AD animal model. Conclusion Our results demonstrated the feasibility of the designed engineered exosomes. The application of this exosomal nanocarrier platform can be extended to the delivery of other oligonucleotide drugs to specific tissues for the treatment of diseases while evading the immune system.
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Affiliation(s)
- En-Yi Lin
- Department of Life Science and Graduate Institute of Biotechnology, National Dong Hwa University, Hualien, Taiwan
- Bioinnovation Center, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan
| | - Shao-Xi Hsu
- Department of Life Science and Graduate Institute of Biotechnology, National Dong Hwa University, Hualien, Taiwan
| | - Bing-Hua Wu
- Department of Life Science and Graduate Institute of Biotechnology, National Dong Hwa University, Hualien, Taiwan
| | - Yu-Chen Deng
- Department of Life Science and Graduate Institute of Biotechnology, National Dong Hwa University, Hualien, Taiwan
- Everfront Biotech Inc, Taipei, Taiwan
| | - Wei Wuli
- Department of Life Science and Graduate Institute of Biotechnology, National Dong Hwa University, Hualien, Taiwan
| | | | | | - Shinn-Zong Lin
- Bioinnovation Center, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan
- Department of Neurosurgery, Hualien Tzu Chi Hospital, Hualien, Taiwan
| | - Horng-Jyh Harn
- Bioinnovation Center, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan
- Department of Pathology, Hualien Tzu Chi Hospital, Hualien, Taiwan
| | - Tzyy-Wen Chiou
- Department of Life Science and Graduate Institute of Biotechnology, National Dong Hwa University, Hualien, Taiwan
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Essayan-Perez S, Südhof TC. Neuronal γ-secretase regulates lipid metabolism, linking cholesterol to synaptic dysfunction in Alzheimer's disease. Neuron 2023; 111:3176-3194.e7. [PMID: 37543038 PMCID: PMC10592349 DOI: 10.1016/j.neuron.2023.07.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 06/16/2023] [Accepted: 07/10/2023] [Indexed: 08/07/2023]
Abstract
Presenilin mutations that alter γ-secretase activity cause familial Alzheimer's disease (AD), whereas ApoE4, an apolipoprotein for cholesterol transport, predisposes to sporadic AD. Both sporadic and familial AD feature synaptic dysfunction. Whether γ-secretase is involved in cholesterol metabolism and whether such involvement impacts synaptic function remains unknown. Here, we show that in human neurons, chronic pharmacological or genetic suppression of γ-secretase increases synapse numbers but decreases synaptic transmission by lowering the presynaptic release probability without altering dendritic or axonal arborizations. In search of a mechanism underlying these synaptic impairments, we discovered that chronic γ-secretase suppression robustly decreases cholesterol levels in neurons but not in glia, which in turn stimulates neuron-specific cholesterol-synthesis gene expression. Suppression of cholesterol levels by HMG-CoA reductase inhibitors (statins) impaired synaptic function similar to γ-secretase inhibition. Thus, γ-secretase enables synaptic function by maintaining cholesterol levels, whereas the chronic suppression of γ-secretase impairs synapses by lowering cholesterol levels.
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Affiliation(s)
- Sofia Essayan-Perez
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA.
| | - Thomas C Südhof
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA 94305, USA.
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Macromolecular structures and proteins interacting with the microtubule associated tau protein. Neuroscience 2022; 518:70-82. [PMID: 35609757 DOI: 10.1016/j.neuroscience.2022.05.023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 04/28/2022] [Accepted: 05/17/2022] [Indexed: 12/25/2022]
Abstract
It is well established that neurodegenerative diseases known as tauopathies are characterized by the presence of filamentous forms of phosphorylated tau protein inside neurons. However, the causal relationship between the initial symptoms of a particular disease and the molecular events affecting tau and leading to the appearance of tangles of filamentous forms of this protein remains unknown. Even the main function (or functions) of tau inside neurons is debatable and controversial. Tau seems to be a multifunctional protein. I review here some of the most studied interactions of tau with different macromolecules and proteins, which can be classified according to the structural o functional unit within which the interaction works: Microtubule, Nuclear localization and DNA, Synaptic activity, RNA metabolism, Fats transport, Proteostasis, Amyloid Cascade Hypothesis, Mitochondria and Phosphorylation. Although this seems to be a broad spectrum of tau functions, interactome studies of tau reveal hundreds of plausible partners of tau, suggesting that it engages in an extensive network of interconnected regulatory interactions by means of its high capability to interact with all kinds of proteins and complex structures, combined with its vast number of post-translational modifications. I include also some thermodynamic data concerning the interaction of tau with some partners.
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Wang D, Chen F, Han Z, Yin Z, Ge X, Lei P. Relationship Between Amyloid-β Deposition and Blood-Brain Barrier Dysfunction in Alzheimer's Disease. Front Cell Neurosci 2021; 15:695479. [PMID: 34349624 PMCID: PMC8326917 DOI: 10.3389/fncel.2021.695479] [Citation(s) in RCA: 75] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 06/23/2021] [Indexed: 12/14/2022] Open
Abstract
Amyloid-β (Aβ) is the predominant pathologic protein in Alzheimer's disease (AD). The production and deposition of Aβ are important factors affecting AD progression and prognosis. The deposition of neurotoxic Aβ contributes to damage of the blood-brain barrier. However, the BBB is also crucial in maintaining the normal metabolism of Aβ, and dysfunction of the BBB aggravates Aβ deposition. This review characterizes Aβ deposition and BBB damage in AD, summarizes their interactions, and details their respective mechanisms.
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Affiliation(s)
- Dong Wang
- Department of Geriatrics, Tianjin Medical University General Hospital, Tianjin, China
- Tianjin Geriatrics Institute, Tianjin, China
| | | | - Zhaoli Han
- Department of Geriatrics, Tianjin Medical University General Hospital, Tianjin, China
- Tianjin Geriatrics Institute, Tianjin, China
| | - Zhenyu Yin
- Department of Geriatrics, Tianjin Medical University General Hospital, Tianjin, China
- Tianjin Geriatrics Institute, Tianjin, China
| | - Xintong Ge
- Tianjin Neurological Institute, Tianjin, China
- Department of Neurosurgery, Tianjin Medical University General Hospital, Tianjin, China
| | - Ping Lei
- Department of Geriatrics, Tianjin Medical University General Hospital, Tianjin, China
- Tianjin Geriatrics Institute, Tianjin, China
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Liu L, Lauro BM, Wolfe MS, Selkoe DJ. Hydrophilic loop 1 of Presenilin-1 and the APP GxxxG transmembrane motif regulate γ-secretase function in generating Alzheimer-causing Aβ peptides. J Biol Chem 2021; 296:100393. [PMID: 33571524 PMCID: PMC7961089 DOI: 10.1016/j.jbc.2021.100393] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 01/22/2021] [Accepted: 02/04/2021] [Indexed: 02/06/2023] Open
Abstract
γ-Secretase is responsible for the proteolysis of amyloid precursor protein (APP) into amyloid-beta (Aβ) peptides, which are centrally implicated in the pathogenesis of Alzheimer’s disease (AD). The biochemical mechanism of how processing by γ-secretase is regulated, especially as regards the interaction between enzyme and substrate, remains largely unknown. Here, mutagenesis reveals that the hydrophilic loop-1 (HL-1) of presenilin-1 (PS1) is critical for both γ-secretase step-wise cleavages (processivity) and its allosteric modulation by heterocyclic γ-modulatory compounds. Systematic mutagenesis of HL-1, including all of its familial AD mutations and additional engineered variants, and quantification of the resultant Aβ products show that HL-1 is necessary for proper sequential γ-secretase processivity. We identify Y106, L113, and Y115 in HL-1 as key targets for heterocyclic γ-secretase modulators (GSMs) to stimulate processing of pathogenic Aβ peptides. Further, we confirm that the GxxxG domain in the APP transmembrane region functions as a critical substrate motif for γ-secretase processivity: a G29A substitution in APP-C99 mimics the beneficial effects of GSMs. Together, these findings provide a molecular basis for the structural regulation of γ-processivity by enzyme and substrate, facilitating the rational design of new GSMs that lower AD-initiating amyloidogenic Aβ peptides.
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Affiliation(s)
- Lei Liu
- Ann Romney Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Bianca M Lauro
- Ann Romney Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Michael S Wolfe
- Department of Medical Chemistry, University of Kansas School of Pharmacy, Lawrence, Kansas, USA
| | - Dennis J Selkoe
- Ann Romney Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
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Yang L, Jiang Y, Shi L, Zhong D, Li Y, Li J, Jin R. AMPK: Potential Therapeutic Target for Alzheimer's Disease. Curr Protein Pept Sci 2021; 21:66-77. [PMID: 31424367 DOI: 10.2174/1389203720666190819142746] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 06/30/2019] [Accepted: 08/31/2019] [Indexed: 12/19/2022]
Abstract
Alzheimer's disease (AD) is the most common neurodegenerative disorder. The pathogenesis of AD is very complicated. For decades, the amyloid hypothesis has influenced and guided research in the field of AD. Meanwhile, researchers gradually realized that AD is caused by multiple concomitant factors, such as autophagy, mitochondrial quality control, insulin resistance and oxidative stress. In current clinical trials, the improvement strategies of AD, such as Aβ antibody immunotherapy and gamma secretase inhibitors, are limited. There is mounting evidence of neurodegenerative disorders indicated that activation of AMP-activated protein kinase (AMPK) may have broad neuroprotective effects. We reviewed the researches on AMPK for AD, the results demonstrated that activation of AMPK is controversial in Aβ deposition and tau phosphorylation, but is positive to promote autophagy, maintain mitochondrial quality control, reduce insulin resistance and relieve oxidative stress. It is concluded that AMPK might be a new target for AD by aggressively treating the risk factors in the future.
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Affiliation(s)
- Luping Yang
- Health Preservation and Rehabilitation College, Chengdu University of Traditional Chinese Medicine, Chengdu, 610037, China
| | - Yijing Jiang
- Rehabilitation Hospital affiliated to Fujian University of Traditional Chinese Medicine Fuzhou 350003 Fujian Key Laboratory of Rehabilitation Technology, Fuzhou 350003, China
| | - Lihong Shi
- Health Preservation and Rehabilitation College, Chengdu University of Traditional Chinese Medicine, Chengdu, 610037, China
| | - Dongling Zhong
- Health Preservation and Rehabilitation College, Chengdu University of Traditional Chinese Medicine, Chengdu, 610037, China
| | - Yuxi Li
- Health Preservation and Rehabilitation College, Chengdu University of Traditional Chinese Medicine, Chengdu, 610037, China
| | - Juan Li
- Health Preservation and Rehabilitation College, Chengdu University of Traditional Chinese Medicine, Chengdu, 610037, China
| | - Rongjiang Jin
- Health Preservation and Rehabilitation College, Chengdu University of Traditional Chinese Medicine, Chengdu, 610037, China
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Abstract
PURPOSE OF REVIEW This article reviews the past 2 years of research on Notch signaling as it relates to bone physiology, with the goal of reconciling seemingly discrepant findings and identifying fruitful areas of potential future research. RECENT FINDINGS Conditional animal models and high-throughput omics have contributed to a greater understanding of the context-dependent role of Notch signaling in bone. However, significant gaps remain in our understanding of how spatiotemporal context and epigenetic state dictate downstream Notch phenotypes. Biphasic activation of Notch signaling orchestrates progression of mesenchymal progenitor cells through the osteoblast lineage, but there is a limited understanding of ligand- and receptor-specific functions. Paracrine Notch signaling through non-osteoblastic cell types contributes additional layers of complexity, and we anticipate impactful future work related to the integration of these cell types and signaling mechanisms.
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Affiliation(s)
- Daniel W Youngstrom
- Department of Orthopaedic Surgery, University of Michigan Medical School, 109 Zina Pitcher Pl, Ann Arbor, MI, 48872, USA.
| | - Kurt D Hankenson
- Department of Orthopaedic Surgery, University of Michigan Medical School, 109 Zina Pitcher Pl, Ann Arbor, MI, 48872, USA
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The amyloid cascade and Alzheimer's disease therapeutics: theory versus observation. J Transl Med 2019; 99:958-970. [PMID: 30760863 DOI: 10.1038/s41374-019-0231-z] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 01/22/2019] [Accepted: 01/24/2019] [Indexed: 12/31/2022] Open
Abstract
The identification of amyloid-β precursor protein (APP) pathogenic mutations in familial early onset Alzheimer's disease (AD), along with knowledge that amyloid-β (Aβ) was the principle protein component of senile plaques, led to the establishment of the amyloid cascade hypothesis. Down syndrome substantiated the hypothesis, given an extra copy of the APP gene and invariable AD pathology hallmarks that occur by middle age. An abundance of support for the amyloid cascade hypothesis followed. Prion-like protein misfolding and non-Mendelian transmission of neurotoxicity are among recent areas of investigation. Aβ-targeted clinical trials have been disappointing, with negative results attributed to inadequacies in patient selection, challenges in pharmacology, and incomplete knowledge of the most appropriate target. There is evidence, however, that proof of concept has been achieved, i.e., clearance of Aβ during life, but with no significant changes in cognitive trajectory in AD. Whether the time, effort, and expense of Aβ-targeted therapy will prove valuable will be determined over time, as Aβ-centered clinical trials continue to dominate therapeutic strategies. It seems reasonable to hypothesize that the amyloid cascade is intimately involved in AD, in parallel with disease pathogenesis, but that removal of toxic Aβ is insufficient for an effective disease modification.
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Structural basis of Notch recognition by human γ-secretase. Nature 2018; 565:192-197. [PMID: 30598546 DOI: 10.1038/s41586-018-0813-8] [Citation(s) in RCA: 164] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 11/01/2018] [Indexed: 11/08/2022]
Abstract
Aberrant cleavage of Notch by γ-secretase leads to several types of cancer, but how γ-secretase recognizes its substrate remains unknown. Here we report the cryo-electron microscopy structure of human γ-secretase in complex with a Notch fragment at a resolution of 2.7 Å. The transmembrane helix of Notch is surrounded by three transmembrane domains of PS1, and the carboxyl-terminal β-strand of the Notch fragment forms a β-sheet with two substrate-induced β-strands of PS1 on the intracellular side. Formation of the hybrid β-sheet is essential for substrate cleavage, which occurs at the carboxyl-terminal end of the Notch transmembrane helix. PS1 undergoes pronounced conformational rearrangement upon substrate binding. These features reveal the structural basis of Notch recognition and have implications for the recruitment of the amyloid precursor protein by γ-secretase.
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Lopez-Font I, Iborra-Lazaro G, Sánchez-Valle R, Molinuevo JL, Cuchillo-Ibañez I, Sáez-Valero J. CSF-ApoER2 fragments as a read-out of reelin signaling: Distinct patterns in sporadic and autosomal-dominant Alzheimer disease. Clin Chim Acta 2018; 490:6-11. [PMID: 30552869 DOI: 10.1016/j.cca.2018.12.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Accepted: 12/11/2018] [Indexed: 01/06/2023]
Abstract
Reelin is a glycoprotein associated with synaptic plasticity and neurotransmission. The malfunctioning of reelin signaling in the brain is likely to contribute to the pathogenesis of Alzheimer's disease (AD). Reelin binding to Apolipoprotein E receptor 2 (ApoER2) activates downstream signaling and induces the proteolytic cleavage of ApoER2, resulting in the generation of soluble fragments. To evaluate the efficiency of reelin signaling in AD, we have quantified the levels of reelin and soluble ectodomain fragments of ApoER2 (ectoApoER2) in the cerebrospinal fluid (CSF). CSF from sporadic AD patients (sAD; n = 14, age 54-83 years) had lower levels of ecto-ApoER2 (~31% reduction; p = .005) compared to those in the age-matched controls (n = 10, age 61-80), and a higher reelin/ecto-ApoER2 ratio. In contrast, autosomal dominant AD patients, carriers of PSEN1 mutations (ADAD; n = 7, age 31-49 years) had higher ecto-ApoER2 levels (~109% increment; p = .001) and a lower reelin/ecto-ApoER2 ratio than the non-mutation carriers from the same families (n = 7, age 25-47 years). Our data suggest that the levels of ecto-ApoER2 in CSF could be a suitable read-out of an impaired reelin signaling in AD, but also indicate differences between sAD and ADAD.
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Affiliation(s)
- Inmaculada Lopez-Font
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, 03550 Sant Joan d'Alacant, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Guillermo Iborra-Lazaro
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, 03550 Sant Joan d'Alacant, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Raquel Sánchez-Valle
- Alzheimer's Disease and Other Cognitive Disorders Unit, Neurology Service, Hospital Clinic, 08036 Barcelona, Spain
| | - José-Luis Molinuevo
- Alzheimer's Disease and Other Cognitive Disorders Unit, Neurology Service, Hospital Clinic, 08036 Barcelona, Spain
| | - Inmaculada Cuchillo-Ibañez
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, 03550 Sant Joan d'Alacant, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain.
| | - Javier Sáez-Valero
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, 03550 Sant Joan d'Alacant, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain.
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Gallardo G, Holtzman DM. Antibody Therapeutics Targeting Aβ and Tau. Cold Spring Harb Perspect Med 2017; 7:cshperspect.a024331. [PMID: 28062555 DOI: 10.1101/cshperspect.a024331] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The astonishing findings that active and passive immunization against amyloid-β (Aβ) in mouse models of Alzheimer's disease (AD) dramatically decreased amyloid burden led to a rapid initiation of human clinical trials with much enthusiasm. However, methodological issues and adverse effects relating to these clinical trials arose, challenging the effectiveness and safety of these reagents. Efforts are now underway to develop safer immunotherapeutic approaches toward Aβ and the treatment of individuals at risk for AD before or in the earliest stages of cognitive decline with new hopes. Furthermore, several studies have shown tau as a potential immunotherapeutic target for the treatment of tauopathy-related diseases including frontotemporal lobar dementia (FTLD). Both active and passive immunization targeting tau in mouse models of tauopathy effectively decreased tau pathology while improving cognitive performance. These preclinical studies have highlighted tau as an alternative target with much anticipation of clinical trials to be undertaken.
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Affiliation(s)
- Gilbert Gallardo
- Department of Neurology, Hope Center for Neurological Disorders, and Knight Alzheimer's Disease Research Center, Washington University, St. Louis, Missouri 63110
| | - David M Holtzman
- Department of Neurology, Hope Center for Neurological Disorders, and Knight Alzheimer's Disease Research Center, Washington University, St. Louis, Missouri 63110
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Abstract
Alzheimer's disease (AD) is characterized neuropathologically by neuronal cell loss, extracellular neuritic plaques composed of β-amyloid (Aβ), and intracellular neurofibrillary tangles composed of hyperphosphorylated tau protein. Aβ is generated by proteolytic processing of the β-amyloid precursor protein (APP). Most individuals with Down syndrome (DS) have three copies of APP, leading to elevated APP expression, increased Aβ deposition, and characteristic AD neuropathology. Sequencing of APP in familial early-onset AD identified missense mutations that cause AD, while a recently discovered coding variant, APP A673T, reduces the risk for AD. Cellular and animal studies show that risk-associated mutations increase total Aβ levels, Aβ42 levels, or Aβ fibrillogenesis, while protective alleles reduce Aβ levels. Together, these studies provide compelling evidence for the Aβ hypothesis and suggest that therapeutics that reduces Aβ levels or Aβ fibrillogenesis should lower the risk for or prevent AD.
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Affiliation(s)
- Julia Tcw
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Alison M Goate
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York 10029
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