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Keable R, Hu S, Pfundstein G, Kozlova I, Su F, Du X, Yang H, Gunnersen J, Schachner M, Leshchyns'ka I, Sytnyk V. The BACE1-generated C-terminal fragment of the neural cell adhesion molecule 2 (NCAM2) promotes BACE1 targeting to Rab11-positive endosomes. Cell Mol Life Sci 2022; 79:555. [PMID: 36251052 PMCID: PMC9576659 DOI: 10.1007/s00018-022-04575-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 09/16/2022] [Accepted: 09/27/2022] [Indexed: 11/08/2022]
Abstract
Beta-site amyloid precursor protein cleaving enzyme 1 (BACE1), also known as β-secretase, is an aspartic protease. The sorting of this enzyme into Rab11-positive recycling endosomes regulates the BACE1-mediated cleavage of its substrates, however, the mechanisms underlying this targeting remain poorly understood. The neural cell adhesion molecule 2 (NCAM2) is a substrate of BACE1. We show that BACE1 cleaves NCAM2 in cultured hippocampal neurons and NCAM2-transfected CHO cells. The C-terminal fragment of NCAM2 that comprises the intracellular domain and a small portion of NCAM2’s extracellular domain, associates with BACE1. This association is not affected in cells with inhibited endocytosis, indicating that the interaction of NCAM2 and BACE1 precedes the targeting of BACE1 from the cell surface to endosomes. In neurons and CHO cells, this fragment and BACE1 co-localize in Rab11-positive endosomes. Overexpression of full-length NCAM2 or a recombinant NCAM2 fragment containing the transmembrane and intracellular domains but lacking the extracellular domain leads to an increase in BACE1 levels in these organelles. In NCAM2-deficient neurons, the levels of BACE1 are increased at the cell surface and reduced in intracellular organelles. These effects are correlated with increased levels of the soluble extracellular domain of BACE1 in the brains of NCAM2-deficient mice, suggesting increased shedding of BACE1 from the cell surface. Of note, shedding of the extracellular domain of Sez6, a protein cleaved exclusively by BACE1, is reduced in NCAM2-deficient animals. These results indicate that the BACE1-generated fragment of NCAM2 regulates BACE1 activity by promoting the targeting of BACE1 to Rab11-positive endosomes.
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Affiliation(s)
- Ryan Keable
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW, 2052, Australia
| | - Shangfeng Hu
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW, 2052, Australia
| | - Grant Pfundstein
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW, 2052, Australia
| | - Irina Kozlova
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW, 2052, Australia
| | - Feifei Su
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW, 2052, Australia
| | - Ximing Du
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW, 2052, Australia
| | - Hongyuan Yang
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW, 2052, Australia
| | - Jenny Gunnersen
- Department of Anatomy and Physiology, School of Biomedical Sciences, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Parkville, VIC, 3010, Australia
| | - Melitta Schachner
- Department of Cell Biology and Neuroscience, Keck Center for Collaborative Neuroscience, Rutgers University, Piscataway, NJ, 08554, USA
| | - Iryna Leshchyns'ka
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW, 2052, Australia
| | - Vladimir Sytnyk
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW, 2052, Australia.
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Armbrust F, Bickenbach K, Marengo L, Pietrzik C, Becker-Pauly C. The Swedish dilemma - the almost exclusive use of APPswe-based mouse models impedes adequate evaluation of alternative β-secretases. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2021; 1869:119164. [PMID: 34699873 DOI: 10.1016/j.bbamcr.2021.119164] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 09/30/2021] [Accepted: 10/11/2021] [Indexed: 02/07/2023]
Abstract
Alzheimer's disease (AD) is the most common form of dementia, however incurable so far. It is widely accepted that aggregated amyloid β (Aβ) peptides play a crucial role for the pathogenesis of AD, as they cause neurotoxicity and deposit as so-called Aβ plaques in AD patient brains. Aβ peptides derive from the amyloid precursor protein (APP) upon consecutive cleavage at the β- and γ-secretase site. Hence, mutations in the APP gene are often associated with autosomal dominant inherited AD. Almost thirty years ago, two mutations at the β-secretase site were observed in two Swedish families (termed Swedish APP (APPswe) mutations), which led to early-onset AD. Consequently, APPswe was established in almost every common AD mouse model, as it contributes to early Aβ plaque formation and cognitive impairments. Analyzing these APPswe-based mouse models, the aspartyl protease BACE1 has been evolving as the prominent β-secretase responsible for Aβ release in AD and as the most important therapeutic target for AD treatment. However, with respect to β-secretase processing, the very rare occurring APPswe variant substantially differs from wild-type APP. BACE1 dominates APPswe processing resulting in the release of Aβ1-x, whereas N-terminally truncated Aβ forms are scarcely generated. However, these N-terminally truncated Aβ species such as Aβ2-x, Aβ3-x and Aβ4-x are elevated in AD patient brains and exhibit an increased potential to aggregate compared to Aβ1-x peptides. Proteases such as meprin β, cathepsin B and ADAMTS4 were identified as alternative β-secretases being capable of generating these N-terminally truncated Aβ species from wild-type APP. However, neither meprin β nor cathepsin B are capable of generating N-terminally truncated Aβ peptides from APPswe. Hence, the role of BACE1 for the Aβ formation during AD might be overrepresented through the excessive use of APPswe mouse models. In this review we critically discuss the consideration of BACE1 as the most promising therapeutic target. Shifting the focus of AD research towards alternative β secretases might unveil promising alternatives to BACE1 inhibitors constantly failing in clinical trials due to ineffectiveness and harmful side effects.
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Affiliation(s)
- Fred Armbrust
- Biochemical Institute, Unit for Degradomics of the Protease Web, University of Kiel, Kiel, Germany
| | - Kira Bickenbach
- Biochemical Institute, Unit for Degradomics of the Protease Web, University of Kiel, Kiel, Germany
| | - Liana Marengo
- Institute for Pathobiochemistry, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Claus Pietrzik
- Institute for Pathobiochemistry, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany.
| | - Christoph Becker-Pauly
- Biochemical Institute, Unit for Degradomics of the Protease Web, University of Kiel, Kiel, Germany.
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Effect of memantine on expression of Bace1-as and Bace1 genes in STZ-induced Alzheimeric rats. Mol Biol Rep 2020; 47:5737-5745. [PMID: 32648077 DOI: 10.1007/s11033-020-05629-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2020] [Accepted: 06/26/2020] [Indexed: 01/05/2023]
Abstract
Recent studies have showed that the long non-coding RNAs (lncRNAs) expression is dysregulated in different neurodegenerative disorders like Alzheimer's disease (AD). In the present study, the effects of memantine on the level of Bace1-as and Bace1 genes' expression in streptozotocin (STZ)-induced Alzheimer's and memantine treated rats were investigated. The male Wistar rats were randomly divided into four groups: 1-Normal control, 2-Sham-operated control, 3- Alzheimer'scontrol rats (ICV-STZ), 4-Experimental group rats treated by memantine in a dose of 30 mg/kg/day for 28 days in ICV-STZ rats. The expression of Bace1-as and Bace1 genes was measured by quantitative-PCR in the brain and blood tissues. ELISA was used to analyze Bace1 and Aβ proteins. Expression of Bace1-as was significantly increased in the brain and blood tissues of the experimental group (p = 0.032 and p = 0.034, respectively). The expression of Bace1 gene showed no significant changes in the brain. Furthermore, the ELISA analysis revealed that Bace1 protein was significantly increased in the plasma of the Alzheimer's control group (p = 0.000) and in the brain tissue of the experimental group (p = 0.000). Additionally, Aβ levels had no significant changes between all groups studied. The Bace1 protein may be used as a prognostic biomarker in plasma, or before using memantine as a treatment. Furthermore, Bace1-as gene expression may play a role in monitoring the progression of AD.
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Lopez-Font I, Boix CP, Zetterberg H, Blennow K, Sáez-Valero J. Characterization of Cerebrospinal Fluid BACE1 Species. Mol Neurobiol 2019; 56:8603-8616. [PMID: 31290061 DOI: 10.1007/s12035-019-01677-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Accepted: 06/10/2019] [Indexed: 11/30/2022]
Abstract
The β-site amyloid precursor protein cleaving enzyme 1 (BACE1) is the main brain β-secretase responsible for the amyloidogenic processing of the amyloid precursor protein (APP). Previous studies have suggested that cerebrospinal fluid (CSF) β-secretase activity may be a candidate diagnostic biomarker for Alzheimer's disease (AD), but biochemical characterization of BACE1 protein in CSF is needed. CSF samples from 19 AD patients and 19 age-matched non-AD controls (n = 19) were classified according to their Aβ42, total tau, and P-tau CSF biomarker levels. We found that β-secretase activity was higher in the CSF of AD subjects than in that of the controls. We found that the majority of the β-secretase activity in the CSF, measured using a peptide substrate homologous to the BACE1 cleavage site, was not inhibited by specific BACE1 inhibitors. We defined enzymatic activity attributable specifically to BACE1 as the activity that was blocked by the specific inhibitors, which is still higher in AD subjects. BACE1 protein levels were characterized by lectin binding, immunoprecipitation, blue native-PAGE, and western blotting using antibodies against specific protein domains. BACE1 was found to be present in human CSF as a mature form of ~ 70 kDa that probably comprised truncated and full-length species, and also as an immature form of ~ 50 kDa that retains the prodomain. CSF-BACE1 was found to assemble into hetero-complexes containing distinct species. Immunoblotting with an antibody against the C-terminus of BACE1 revealed significantly higher levels of the 70-kDa full-length BACE1, while the 50 kDa immature form remained unaltered. When the 70-kDa species was probed with an antibody against the N-terminus of BACE1 (which does not discriminate between truncated and full-length forms), no increase in immunoreactivity was observed, suggesting that truncated forms of BACE1 do not increase in AD. In conclusion, the complexity of BACE1 species in CSF has to be taken into consideration when determining BACE1 activity and protein levels in CSF as biomarkers of AD.
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Affiliation(s)
- Inmaculada Lopez-Font
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, Av. Ramón y Cajal s/n, E-03550, Sant Joan d'Alacant, Spain. .,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Sant Joan d'Alacant, Spain.
| | - Claudia P Boix
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, Av. Ramón y Cajal s/n, E-03550, Sant Joan d'Alacant, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Sant Joan d'Alacant, Spain
| | - Henrik Zetterberg
- Clinical Neurochemistry Laboratory, Sahlgrenska University Hospital, Mölndal, Sweden.,Department of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Mölndal, Sweden.,Department of Neurodegenerative Disease, UCL Institute of Neurology, Queen Square, London, UK.,UK Dementia Research Institute at UCL, London, UK
| | - Kaj Blennow
- Clinical Neurochemistry Laboratory, Sahlgrenska University Hospital, Mölndal, Sweden.,Department of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Mölndal, Sweden
| | - Javier Sáez-Valero
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, Av. Ramón y Cajal s/n, E-03550, Sant Joan d'Alacant, Spain. .,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Sant Joan d'Alacant, Spain.
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Manzine PR, Souza MDS, Cominetti MR. BACE1 levels are increased in plasma of Alzheimer's disease patients compared with matched cognitively healthy controls. Per Med 2016; 13:531-540. [DOI: 10.2217/pme-2016-0033] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Aim: BACE1 is the secretase that acts in Aβ production in Alzheimer's disease (AD). Materials & methods: We investigated mRNA expression in total blood and the levels of plasma protein BACE1 in AD patients compared with cognitively healthy subjects. Probable AD (n = 47) and non-AD control group (n = 32) were evaluated for mRNA expression for BACE1 using reverse transcription-qPCR. A subsample of n = 21 AD and n = 20 non-AD had plasma BACE1 levels analyzed, using ELISA. Results: No differences were found on BACE1 mRNA between groups. However, higher levels of BACE1 were detected in plasma of AD patients. Discussion: Blood-based diagnostic tools are desired to improve AD diagnosis. BACE1 plasma levels could provide an additional diagnostic tool for AD in association with neuropsychological tests.
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Affiliation(s)
- Patricia Regina Manzine
- Departamento de Gerontologia, Rodovia Washington Luís, Km 235, CEP 13565-905, São Carlos, SP, Brazil
| | - Matheus da Silva Souza
- Departamento de Gerontologia, Rodovia Washington Luís, Km 235, CEP 13565-905, São Carlos, SP, Brazil
| | - Márcia Regina Cominetti
- Departamento de Gerontologia, Rodovia Washington Luís, Km 235, CEP 13565-905, São Carlos, SP, Brazil
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Amyloid β-protein oligomers upregulate the β-secretase, BACE1, through a post-translational mechanism involving its altered subcellular distribution in neurons. Mol Brain 2015; 8:73. [PMID: 26552445 PMCID: PMC4638102 DOI: 10.1186/s13041-015-0163-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Accepted: 11/01/2015] [Indexed: 12/13/2022] Open
Abstract
Background β-Site amyloid precursor protein cleaving enzyme 1 (BACE1) is a membrane-bound aspartyl protease that initiates amyloid β-protein (Aβ) generation. Aberrant elevation of BACE1 levels in brains of Alzheimer’s disease (AD) patients may involve Aβ. In the present study, we used a neuron culture model system to investigate the effects of Aβ on BACE1 expression as well as the underlying mechanisms. Results Rat primary cortical neurons were treated with relatively low concentrations (2.5 μM) of Aβ42 oligomers (Aβ-O) or fibrils (Aβ-F) for 2–3 days. Aβ-O induced a significant increase in protein levels of BACE1, while Aβ-F only had a marginal effect. Levels of amyloid precursor protein (APP) and the major α-secretase, ADAM10, remained unaltered upon treatment with both types of Aβ. Aβ-O treatment resulted in activation of eIF2α and caspase 3 in a time-dependent manner, with no changes in the endoplasmic reticulum (ER) stress marker, GRP78, indicating that a typical ER stress response is not induced under our experimental conditions. Furthermore, Aβ-O did not affect BACE1 mRNA expression but augmented the levels of exogenous BACE1 expressed via recombinant adenoviruses, indicating regulation of BACE1 protein expression, not at the transcriptional or translational but the post-translational level. Immunocytochemical analysis revealed that Aβ-O causes a significant increase in BACE1 immunoreactivity in neurites (both axons and dendrites), but not soma of neurons; this change appears relevant to the mechanism of Aβ-O-induced BACE1 elevation, which may involve impairment of BACE1 trafficking and degradation. In contrast, Aβ-O had no effect on APP immunoreactivity. Conclusion Our results collectively suggest that Aβ oligomers induce BACE1 elevation via a post-translational mechanism involving its altered subcellular distribution in neurons, which possibly triggers a vicious cycle of Aβ generation, thus contributing to the pathogenetic mechanism of AD. Electronic supplementary material The online version of this article (doi:10.1186/s13041-015-0163-5) contains supplementary material, which is available to authorized users.
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Lopez-Font I, Cuchillo-Ibañez I, Sogorb-Esteve A, García-Ayllón MS, Sáez-Valero J. Transmembrane Amyloid-Related Proteins in CSF as Potential Biomarkers for Alzheimer's Disease. Front Neurol 2015; 6:125. [PMID: 26082753 PMCID: PMC4451586 DOI: 10.3389/fneur.2015.00125] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Accepted: 05/17/2015] [Indexed: 02/04/2023] Open
Abstract
In the continuing search for new cerebrospinal fluid (CSF) biomarkers for Alzheimer’s disease (AD), reasonable candidates are the secretase enzymes involved in the processing of the amyloid precursor protein (APP), as well as the large proteolytic cleavage fragments sAPPα and sAPPβ. The enzymatic activities of some of these secretases, such as BACE1 and TACE, have been investigated as potential AD biomarkers, and it has been assumed that these activities present in human CSF result from the soluble truncated forms of the membrane-bound enzymes. However, we and others recently identified soluble forms of BACE1 and APP in CSF containing the intracellular domains, as well as the multi-pass transmembrane presenilin-1 (PS1) and other subunits of γ-secretase. We also review recent findings that suggest that most of these soluble transmembrane proteins could display self-association properties based on hydrophobic and/or ionic interactions leading to the formation of heteromeric complexes. The oligomerization state of these potential new biomarkers needs to be taken into consideration for assessing their real potential as CSF biomarkers for AD by adequate molecular tools.
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Affiliation(s)
- Inmaculada Lopez-Font
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC , Sant Joan d'Alacant , Spain ; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED) , Sant Joan d'Alacant , Spain
| | - Inmaculada Cuchillo-Ibañez
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC , Sant Joan d'Alacant , Spain ; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED) , Sant Joan d'Alacant , Spain
| | - Aitana Sogorb-Esteve
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC , Sant Joan d'Alacant , Spain ; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED) , Sant Joan d'Alacant , Spain
| | - María-Salud García-Ayllón
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC , Sant Joan d'Alacant , Spain ; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED) , Sant Joan d'Alacant , Spain ; Unidad de Investigación, Fundación para el Fomento de la Investigación Sanitaria Biomédica de la Comunidad Valenciana (FISABIO), Hospital General Universitario de Elche , Elche , Spain
| | - Javier Sáez-Valero
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC , Sant Joan d'Alacant , Spain ; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED) , Sant Joan d'Alacant , Spain
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LRP1 Downregulates the Alzheimer's β-Secretase BACE1 by Modulating Its Intraneuronal Trafficking. eNeuro 2015; 2:eN-NWR-0006-15. [PMID: 26464978 PMCID: PMC4596091 DOI: 10.1523/eneuro.0006-15.2015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Revised: 03/26/2015] [Accepted: 03/30/2015] [Indexed: 01/02/2023] Open
Abstract
The β-secretase called BACE1 is a membrane-associated protease that initiates the generation of amyloid β-protein (Aβ), a key event in Alzheimer's disease (AD). However, the mechanism of intraneuronal regulation of BACE1 is poorly understood. Here, we present evidence that low-density lipoprotein receptor-related protein 1 (LRP1), a multi-functional receptor, has a previously unrecognized function to regulate BACE1 in neurons. We show that deficiency of LRP1 exerts promotive effects on the protein expression and function of BACE1, whereas expression of LRP-L4, a functional LRP1 mini-receptor, specifically decreases BACE1 levels in both human embryonic kidney (HEK) 293 cells and rat primary neurons, leading to reduced Aβ production. Our subsequent analyses further demonstrate that (1) both endogenous and exogenous BACE1 and LRP1 interact with each other and are colocalized in soma and neurites of primary neurons, (2) LRP1 reduces the protein stability and cell-surface expression of BACE1, and (3) LRP1 facilitates the shift in intracellular localization of BACE1 from early to late endosomes, thereby promoting lysosomal degradation. These findings establish that LRP1 specifically downregulates BACE1 by modulating its intraneuronal trafficking and stability through protein interaction and highlight LRP1 as a potential therapeutic target in AD.
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Caillava C, Ranaldi S, Lauritzen I, Bauer C, Fareh J, Abraham JD, Checler F. Study on Aβ34 biology and detection in transgenic mice brains. Neurobiol Aging 2014; 35:1570-81. [PMID: 24495834 DOI: 10.1016/j.neurobiolaging.2014.01.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Revised: 01/02/2014] [Accepted: 01/08/2014] [Indexed: 11/28/2022]
Abstract
The β-amyloid precursor protein undergoes cleavages by β- and γ-secretasses yielding amyloid-β peptides (Aβ) that accumulate in Alzheimer's disease. Subsequently, Aβ peptides are targets of additional truncations or endoproteolytic cleavages explaining the diversity of Aβ-related fragments recovered in cell media or pathologic human fluids. Here, we focused on Aβ1-34 (Aβ34) that has been detected both in vitro and in vivo and that derives from the hydrolysis of Aβ by β-secretase. We have obtained and fully characterized by immunologic and biochemical approaches, a polyclonal antibody that specifically recognizes the C-terminus of Aβx-34. We present immunohistochemical evidence for the presence of Aβx-34 in the brain of 3xTg mice and Alzheimer's disease-affected human brains. Finally, we demonstrate a neprilysin-mediated degradation process of Aβ34 and the ability of synthetic Aβ34 to protect HEK cells overexpressing either wild type or Swedish-mutated β-amyloid precursor protein from apoptosis.
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Affiliation(s)
- Céline Caillava
- Institut de Pharmacologie Moléculaire et Cellulaire, UMR7275 CNRS/UNS, Team "Fondation pour la Recherche Médicale" and "Labex Distalz", Valbonne, France
| | | | - Inger Lauritzen
- Institut de Pharmacologie Moléculaire et Cellulaire, UMR7275 CNRS/UNS, Team "Fondation pour la Recherche Médicale" and "Labex Distalz", Valbonne, France
| | - Charlotte Bauer
- Institut de Pharmacologie Moléculaire et Cellulaire, UMR7275 CNRS/UNS, Team "Fondation pour la Recherche Médicale" and "Labex Distalz", Valbonne, France
| | - Jeannette Fareh
- SysDiag CNRS-Bio-Rad, UMR3145, SysDiag,, Montpellier, France
| | | | - Frédéric Checler
- Institut de Pharmacologie Moléculaire et Cellulaire, UMR7275 CNRS/UNS, Team "Fondation pour la Recherche Médicale" and "Labex Distalz", Valbonne, France.
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Macias MP, Gonzales AM, Siniard AL, Walker AW, Corneveaux JJ, Huentelman MJ, Sabbagh MN, Decourt B. A cellular model of amyloid precursor protein processing and amyloid-β peptide production. J Neurosci Methods 2013; 223:114-22. [PMID: 24333289 DOI: 10.1016/j.jneumeth.2013.11.024] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2013] [Revised: 11/24/2013] [Accepted: 11/27/2013] [Indexed: 01/10/2023]
Abstract
BACKGROUND A hallmark pathologic feature of Alzheimer's disease (AD) is accumulation of neuritic senile plaques in the brain parenchyma. Neurotoxic plaque cores are composed predominantly of amyloid-β (Aβ) peptides of 40 and 42 amino acids in length, formed by sequential cleavage of amyloid precursor protein (APP) by β-, and γ-secretases. There is a great interest in approaches to modulate Aβ peptide production and develop therapeutic interventions to reduce Aβ levels to halt or slow the progression of neurodegeneration. NEW METHOD We characterized and present the BE(2)-M17 human neuroblastoma cell line as a novel in vitro model of the APP-cleavage cascade to support future (1) functional studies of molecular regulators in Aβ production, and (2) high-throughput screening assays of new pharmacotherapeutics. RESULTS In BE(2)-M17 cells, both RNA (i.e., RT-PCR, RNA sequencing) and protein analyses (i.e., Western blots, ELISA), show endogenous expression of critical components of the amyloidogenic pathway, APP-cleavage intermediates CTF83 and CTF99, and final cleavage products Aβ40 and Aβ42. We further report effects of retinoic acid-mediated differentiation on morphology and gene expression in this cell line. COMPARISON WITH EXISTING METHOD(S) In contrast to primary isolates or other cell lines reported in current literature, BE(2)-M17 not only sustains baseline expression of the full contingent of APP-processing components, but also remains stably adherent during culture, facilitating experimental manipulations. CONCLUSIONS Our evidence supports the use of BE(2)-M17 as a novel, human, cell-based model of the APP processing pathway that offers a potential streamlined approach to dissect molecular functions of endogenous regulatory pathways, and perform mechanistic studies to identify modulators of Aβ production.
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Affiliation(s)
- Mimi P Macias
- Haldeman Laboratory of Molecular Diagnostics and Therapeutics, Banner Sun Health Research Institute, 10515 W, Santa Fe Drive, Sun City, AZ 85351, USA.
| | - Amanda M Gonzales
- Haldeman Laboratory of Molecular Diagnostics and Therapeutics, Banner Sun Health Research Institute, 10515 W, Santa Fe Drive, Sun City, AZ 85351, USA.
| | - Ashley L Siniard
- Neurogenomics Division, The Translational Genomics Research Institute, 445N, Fifth Street, Phoenix, AZ 85004, USA.
| | - Aaron W Walker
- Haldeman Laboratory of Molecular Diagnostics and Therapeutics, Banner Sun Health Research Institute, 10515 W, Santa Fe Drive, Sun City, AZ 85351, USA.
| | - Jason J Corneveaux
- Neurogenomics Division, The Translational Genomics Research Institute, 445N, Fifth Street, Phoenix, AZ 85004, USA.
| | - Matthew J Huentelman
- Neurogenomics Division, The Translational Genomics Research Institute, 445N, Fifth Street, Phoenix, AZ 85004, USA.
| | - Marwan N Sabbagh
- Haldeman Laboratory of Molecular Diagnostics and Therapeutics, Banner Sun Health Research Institute, 10515 W, Santa Fe Drive, Sun City, AZ 85351, USA.
| | - Boris Decourt
- Haldeman Laboratory of Molecular Diagnostics and Therapeutics, Banner Sun Health Research Institute, 10515 W, Santa Fe Drive, Sun City, AZ 85351, USA.
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Decourt B, Gonzales A, Beach TG, Malek-Ahmadi M, Walker A, Sue L, Walker DG, Sabbagh MN. BACE1 levels by APOE genotype in non-demented and Alzheimer's post-mortem brains. Curr Alzheimer Res 2013; 10:309-15. [PMID: 23036023 PMCID: PMC4104947 DOI: 10.2174/1567205011310030010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Revised: 08/13/2012] [Accepted: 08/27/2012] [Indexed: 01/04/2023]
Abstract
The APOE genotype is a known susceptibility factor for Alzheimer's disease (AD). It is apparent that the presence of the APOE ε40 allele increases the risk for developing AD, lowers the age of onset in AD, and may influence the pathological burden seen in AD. In this study, we asked whether BACE1 levels differ by APOE genotype in the AD and non-demented (ND) brain. We isolated mid-frontal cortex (MFC) and mid-temporal cortex (MTC) from post-mortem ND and AD subjects that were APOE ε3/3, ε3/4, ε4/4 carriers. All AD subjects met NINDS-ADRDA and NIA-Reagan criteria for a diagnosis of AD. The MFC and MTC were homogenized and the lysates underwent ELISA and Western blotting for BACE1. The ELISA revealed that total BACE1 levels were lower in the MFC of AD compared to ND subjects. Furthermore, in APOE ε4 carriers BACE1 levels were lower than ε3/3 carriers in the ND frontal cortex. No difference in BACE1 levels was observed in AD MFC and in ND and AD MTC tissues. The ELISA results were confirmed by Western blotting. Our data suggest that brain BACEl levels may be influenced by the apolipoprotein E genotype before the onset of AD, providing an alternative explanation for the lower amyloid beta 42 levels in CSF in ND and AD subjects.
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Affiliation(s)
- Boris Decourt
- Haldeman Laboratory of Molecular Diagnostics and Therapeutics, Banner Sun Health Research Institute, Sun City AZ 85351, USA
| | - Amanda Gonzales
- Haldeman Laboratory of Molecular Diagnostics and Therapeutics, Banner Sun Health Research Institute, Sun City AZ 85351, USA
| | - Thomas G. Beach
- Civin Laboratory of Neuropathology, Banner Sun Health Research Institute, Sun City AZ 85351, USA
| | - Michael Malek-Ahmadi
- Cleo Roberts Center for Clinical Research, Banner Sun Health Research Institute, Sun City AZ 85351, USA
| | - Aaron Walker
- Haldeman Laboratory of Molecular Diagnostics and Therapeutics, Banner Sun Health Research Institute, Sun City AZ 85351, USA
| | - Lucia Sue
- Civin Laboratory of Neuropathology, Banner Sun Health Research Institute, Sun City AZ 85351, USA
| | - Douglas G. Walker
- Laboratory of Neuroregeneration, Banner Sun Health Research Institute, Sun City AZ 85351, USA
| | - Marwan N. Sabbagh
- Haldeman Laboratory of Molecular Diagnostics and Therapeutics, Banner Sun Health Research Institute, Sun City AZ 85351, USA
- Cleo Roberts Center for Clinical Research, Banner Sun Health Research Institute, Sun City AZ 85351, USA
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Statins reduce amyloid β-peptide production by modulating amyloid precursor protein maturation and phosphorylation through a cholesterol-independent mechanism in cultured neurons. Neurochem Res 2012; 38:589-600. [PMID: 23269484 DOI: 10.1007/s11064-012-0956-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Revised: 12/17/2012] [Accepted: 12/19/2012] [Indexed: 01/19/2023]
Abstract
Statins, 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors, have been reported to attenuate amyloid-β peptide (Aβ) production in various cellular models. However, the mechanisms by which statins affect neuronal Aβ production have not yet been clarified. Here, we investigated this issue in rat primary cortical neurons using two statins, pitavastatin (PV) and atorvastatin (AV). Treatment of neurons with 0.2-2.5 μM PV or AV for 4 days induced a concentration- and time-dependent reduction in the secretion of both Aβ40 and Aβ42. Moreover, Western blot analyses of cell lysates showed that treatment with PV or AV significantly reduced expression levels of the mature form of amyloid precursor protein (APP) and Thr668-phosphorylated APP (P-APP), but not immature form of APP; the decreases in P-APP levels were more notable than those of mature APP levels. The statin treatment did not alter expression of BACE1 (β-site APP-cleaving enzyme 1) or γ-secretase complex proteins (presenilin 1, nicastrin, APH-1, and PEN-2). In neurons overexpressing APP via recombinant adenoviruses, PV or AV similarly reduced Aβ secretion and the levels of mature APP and P-APP. Statins also markedly reduced cellular cholesterol content in neurons in a concentration-dependent manner. Co-treatment with mevalonate reversed the statin-induced decreases in Aβ secretion and mature APP and P-APP levels, whereas co-treatment with cholesterol did not, despite recovery of cellular cholesterol levels. Finally, cell-surface biotinylation experiments revealed that both statins significantly reduced the levels of cell-surface P-APP without changing those of cell surface mature APP. These results suggest that statins reduce Aβ production by selectively modulating APP maturation and phosphorylation through a mechanism independent of cholesterol reduction in cultured neurons.
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Motoki K, Kume H, Oda A, Tamaoka A, Hosaka A, Kametani F, Araki W. Neuronal β-amyloid generation is independent of lipid raft association of β-secretase BACE1: analysis with a palmitoylation-deficient mutant. Brain Behav 2012; 2:270-82. [PMID: 22741101 PMCID: PMC3381632 DOI: 10.1002/brb3.52] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2012] [Revised: 03/03/2012] [Accepted: 03/05/2012] [Indexed: 12/18/2022] Open
Abstract
β-Secretase, BACE1 is a neuron-specific membrane-associated protease that cleaves amyloid precursor protein (APP) to generate β-amyloid protein (Aβ). BACE1 is partially localized in lipid rafts. We investigated whether lipid raft localization of BACE1 affects Aβ production in neurons using a palmitoylation-deficient mutant and further analyzed the relationship between palmitoylation of BACE1 and its shedding and dimerization. We initially confirmed that BACE1 is mainly palmitoylated at four C-terminal cysteine residues in stably transfected neuroblastoma cells. We found that raft localization of mutant BACE1 lacking the palmitoylation modification was markedly reduced in comparison to wild-type BACE1 in neuroblastoma cells as well as rat primary cortical neurons expressing BACE1 via recombinant adenoviruses. In primary neurons, expression of wild-type and mutant BACE1 enhanced production of Aβ from endogenous or overexpressed APP to similar extents with the β-C-terminal fragment (β-CTF) of APP mainly distributed in nonraft fractions. Similarly, β-CTF was recovered mainly in nonraft fractions of neurons expressing Swedish mutant APP only. These results show that raft association of BACE1 does not influence β-cleavage of APP and Aβ production in neurons, and support the view that BACE1 cleaves APP mainly in nonraft domains. Thus, we propose a model of neuronal Aβ generation involving mobilization of β-CTF from nonraft to raft domains. Additionally, we obtained data indicating that palmitoylation plays a role in BACE1 shedding but not dimerization.
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Affiliation(s)
- Kazumi Motoki
- Department of Demyelinating Disease and Aging, National Institute of Neuroscience, NCNP, Kodaira, Tokyo 187‐8502, Japan
| | - Hideaki Kume
- Department of Demyelinating Disease and Aging, National Institute of Neuroscience, NCNP, Kodaira, Tokyo 187‐8502, Japan
| | - Akiko Oda
- Department of Demyelinating Disease and Aging, National Institute of Neuroscience, NCNP, Kodaira, Tokyo 187‐8502, Japan
- Department of Neurology, Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Ibaraki 305‐8575, Japan
| | - Akira Tamaoka
- Department of Neurology, Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Ibaraki 305‐8575, Japan
| | - Ai Hosaka
- Department of Demyelinating Disease and Aging, National Institute of Neuroscience, NCNP, Kodaira, Tokyo 187‐8502, Japan
- Department of Neurology, Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Ibaraki 305‐8575, Japan
| | - Fuyuki Kametani
- Department of Dementia and Higher Brain Function, Tokyo Metropolitan Institute of Medical Science, Setagaya, Tokyo 156‐8506, Japan
| | - Wataru Araki
- Department of Demyelinating Disease and Aging, National Institute of Neuroscience, NCNP, Kodaira, Tokyo 187‐8502, Japan
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Decourt B, Sabbagh MN. BACE1 as a potential biomarker for Alzheimer's disease. J Alzheimers Dis 2011; 24 Suppl 2:53-9. [PMID: 21403391 DOI: 10.3233/jad-2011-110017] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The diagnosis of Alzheimer's disease (AD) relies principally on clinical criteria for probable and possible AD as defined by the NINCDS-ADRDRA. The field is desperately lacking of biological markers to assist with AD diagnosis and verification of treatment efficacy. According to the Consensus Report of the Working Group on Molecular and Biochemical Markers of Alzheimer's Disease, in order to qualify as a biomarker the sample in question must adhere to certain basic requirements, including the ability to: reflect AD pathology and differentiate it from other dementia with an 80% sensitivity; be reliable and reproducible; be easy to perform and analyze; remain relatively inexpensive. Beta secretases are crucial enzymes in the pathogenesis of AD. Given its primary role in brain amyloidogenesis and its ubiquitous expression, one may consider measuring peripheral BACE1 levels and activity as biomarkers of AD, like performed in the brain and cerebrospinal fluid. However, very little is known about the periphery and whether peripheral BACE1 is involved in AD pathogenesis or mirrors AD progression. Moreover, no investigation has focused on the possibility of monitoring peripheral BACE1 to assess the efficiency of BACE1 inhibitors during the course of clinical trials. Part of the problem may be attributed to the lack of sensitive molecular tools which are absolutely necessary to use BACE1 as a biomarker. In this review we evaluate the progress and feasibility of developing BACE1 as a biomarker for AD in different tissues.
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Affiliation(s)
- Boris Decourt
- Banner Sun Health Research Institute, Haldeman Laboratory of Molecular Diagnostics and Therapeutics, Sun City, AZ 85351, USA.
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Gonzales A, Decourt B, Walker A, Condjella R, Nural H, Sabbagh MN. Development of a specific ELISA to measure BACE1 levels in human tissues. J Neurosci Methods 2011; 202:70-6. [PMID: 21889954 DOI: 10.1016/j.jneumeth.2011.08.030] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Revised: 08/12/2011] [Accepted: 08/17/2011] [Indexed: 11/26/2022]
Abstract
The aspartyl protease BACE1 is the rate limiting enzyme in the synthesis of amyloid beta, which accumulation in the human brain is a hallmark of Alzheimer's disease (AD). BACE1 has been proposed as a surrogate marker of AD; however, very few BACE1 immunoassays have been reported. In the present study we have screened ten BACE1 antibodies by Western blot and several antibody pairs to develop a new BACE1 sandwich ELISA procedure. We identified one pair that showed little background and good reproducibility. Several dilution buffers and sample denaturation methods were tried to partially unfold BACE1 before capture. We found that dilution in PBS followed by 10 min incubation at 50°C critically improves the performance of the assay. Finally, we successfully measured BACE1 levels in a few human brain and platelet lysates as well as in plasma and AD CSF. We anticipate that this assay will lay the ground to accurately measure BACE1 levels in human tissues, which could facilitate the molecular diagnosis of AD in the near future.
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Affiliation(s)
- Amanda Gonzales
- Banner Sun Health Research Institute, Haldeman Laboratory of Molecular Diagnostics and Therapeutics, 10515 Santa Fe Drive, Sun City, AZ 85351, USA.
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Cole SL, Vassar R. The Basic Biology of BACE1: A Key Therapeutic Target for Alzheimer's Disease. Curr Genomics 2011; 8:509-30. [PMID: 19415126 PMCID: PMC2647160 DOI: 10.2174/138920207783769512] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2007] [Revised: 12/27/2007] [Accepted: 12/27/2007] [Indexed: 11/22/2022] Open
Abstract
Alzheimer’s disease (AD) is an intractable, neurodegenerative disease that appears to be brought about by both genetic and non-genetic factors. The neuropathology associated with AD is complex, although amyloid plaques composed of the β-amyloid peptide (Aβ) are hallmark neuropathological lesions of AD brain. Indeed, Aβ plays an early and central role in this disease. β-site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1) is the initiating enzyme in Aβ genesis and BACE1 levels are elevated under a variety of conditions. Given the strong correlation between Aβ and AD, and the elevation of BACE1 in this disease, this enzyme is a prime drug target for inhibiting Aβ production in AD. However, nine years on from the initial identification of BACE1, and despite intense research, a number of key questions regarding BACE1 remain unanswered. Indeed, drug discovery and development for AD continues to be challenging. While current AD therapies temporarily slow cognitive decline, treatments that address the underlying pathologic mechanisms of AD are completely lacking. Here we review the basic biology of BACE1. We pay special attention to recent research that has provided some answers to questions such as those involving the identification of novel BACE1 substrates, the potential causes of BACE1 elevation and the putative function of BACE1 in health and disease. Our increasing understanding of BACE1 biology should aid the development of compounds that interfere with BACE1 expression and activity and may lead to the generation of novel therapeutics for AD.
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Affiliation(s)
- S L Cole
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, 303 E. Chicago Avenue, Chicago, IL 60611, USA
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Kume H, Murayama KS, Araki W. The two-hydrophobic domain tertiary structure of reticulon proteins is critical for modulation of beta-secretase BACE1. J Neurosci Res 2010; 87:2963-72. [PMID: 19405102 DOI: 10.1002/jnr.22112] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
beta-Site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1) is a membrane-bound protease that is essential for the production of beta-amyloid protein (Abeta). Given the crucial role of Abeta accumulation in Alzheimer's disease (AD), inhibition of BACE1 activity may represent a feasible therapeutic strategy in the treatment of AD. Recently, we and others identified reticulon 3 (RTN3) and reticulon 4-B/C (RTN4-B/C or Nogo-B/C) as membrane proteins that interact with BACE1 and inhibit its ability to produce Abeta. In this study, we employed various mutants of RTN3 and RTN4-C and C. elegans RTN to investigate the molecular mechanisms by which RTNs regulate BACE1. We found that RTN3 mutants lacking the N-terminal or C-terminal or loop domain as well as a RTN4-C mutant lacking the C-terminal domain bound to BACE1 comparably to wild-type RTN3 and RTN4-C. Furthermore, overexpression of wild-type RTN3, RTN4-C, and these RTN mutants similarly reduced Abeta40 and Abeta42 secretion by cells expressing Swedish mutant APP. C. elegans RTN, which has low homology to human RTNs, also interacted with BACE1 and inhibited Abeta secretion. In contrast, two RTN3 mutants containing deletions of the first or second potential transmembrane domains and an RTN3 swap mutant of the second transmembrane domain bound BACE1 but failed to inhibit Abeta secretion. Collectively, these results suggest that the two-transmembrane-domain tertiary structure of RTN proteins is critical for the ability of RTNs to modulate BACE1 activity, whereas N-terminal, C-terminal and loop regions are not essential for this function.
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Affiliation(s)
- Hideaki Kume
- Department of Demyelinating Disease and Aging, National Institute of Neuroscience, NCNP, Tokyo, Japan
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Kume H, Konishi Y, Murayama KS, Kametani F, Araki W. Expression of reticulon 3 in Alzheimer's disease brain. Neuropathol Appl Neurobiol 2009; 35:178-88. [PMID: 19284479 DOI: 10.1111/j.1365-2990.2008.00974.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
AIMS Reticulon 3 (RTN3), a member of the reticulon family of proteins, interacts with the beta-secretase, beta-site amyloid precursor protein-cleaving enzyme 1 (BACE1), and inhibits its activity to produce beta-amyloid protein. The aim of the present study was to clarify the biological role of RTN3 in the brain and its potential involvement in the neuropathology of Alzheimer's disease (AD). METHODS We performed immunohistochemical and biochemical analyses using a specific antibody against RTN3 to investigate the expression and subcellular localization of RTN3 in control and AD brain tissue samples. RESULTS Western blot analysis revealed no significant differences in the RTN3 levels between control and AD brains. Immunohistochemical staining showed that RTN3 immunoreactivity was predominantly localized in pyramidal neurones of the cerebral cortex. The patterns of RTN3 immunostaining were similar in control and AD cerebral cortices, and senile plaques were generally negative for RTN3. Biochemical subcellular fractionation disclosed that RTN3 colocalized with BACE1 in various fractions, including the endoplasmic reticulum and the Golgi apparatus. Double-immunofluorescence staining additionally indicated that RTN3 was localized in both endoplasmic reticulum and Golgi compartments in neurones. CONCLUSIONS These results show that RTN3 is primarily expressed in pyramidal neurones of the human cerebral cortex and that no clear difference of RTN3 immunoreactivity is observable between control and AD brains. Our data also suggest that there is considerable colocalization of RTN3 with BACE1 at a subcellular level.
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Affiliation(s)
- H Kume
- Department of Demyelinating Disease and Ageing, National Institute of Neuroscience, NCNP, Tokyo, Japan
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Cole SL, Vassar R. The Alzheimer's disease beta-secretase enzyme, BACE1. Mol Neurodegener 2007; 2:22. [PMID: 18005427 PMCID: PMC2211305 DOI: 10.1186/1750-1326-2-22] [Citation(s) in RCA: 349] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2007] [Accepted: 11/15/2007] [Indexed: 12/11/2022] Open
Abstract
The pathogenesis of Alzheimer's disease is highly complex. While several pathologies characterize this disease, amyloid plaques, composed of the β-amyloid peptide are hallmark neuropathological lesions in Alzheimer's disease brain. Indeed, a wealth of evidence suggests that β-amyloid is central to the pathophysiology of AD and is likely to play an early role in this intractable neurodegenerative disorder. The BACE1 enzyme is essential for the generation of β-amyloid. BACE1 knockout mice do not produce β-amyloid and are free from Alzheimer's associated pathologies including neuronal loss and certain memory deficits. The fact that BACE1 initiates the formation of β-amyloid, and the observation that BACE1 levels are elevated in this disease provide direct and compelling reasons to develop therapies directed at BACE1 inhibition thus reducing β-amyloid and its associated toxicities. However, new data indicates that complete abolishment of BACE1 may be associated with specific behavioral and physiological alterations. Recently a number of non-APP BACE1 substrates have been identified. It is plausible that failure to process certain BACE1 substrates may underlie some of the reported abnormalities in the BACE1-deficient mice. Here we review BACE1 biology, covering aspects ranging from the initial identification and characterization of this enzyme to recent data detailing the apparent dysregulation of BACE1 in Alzheimer's disease. We pay special attention to the putative function of BACE1 during healthy conditions and discuss in detail the relationship that exists between key risk factors for AD, such as vascular disease (and downstream cellular consequences), and the pathogenic alterations in BACE1 that are observed in the diseased state.
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Affiliation(s)
- Sarah L Cole
- Department of Cell and Molecular Biology, The Feinberg School of Medicine, Northwestern University, Chicago Avenue, Chicago, IL, USA.
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Murayama KS, Kametani F, Saito S, Kume H, Akiyama H, Araki W. Reticulons RTN3 and RTN4-B/C interact with BACE1 and inhibit its ability to produce amyloid β-protein. Eur J Neurosci 2006; 24:1237-44. [PMID: 16965550 DOI: 10.1111/j.1460-9568.2006.05005.x] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Beta-secretase beta-site APP cleaving enzyme 1 (BACE1), is a membrane-bound aspartyl protease necessary for the generation of amyloid beta-protein (Abeta), which accumulates in the brains of individuals with Alzheimer's disease (AD). To gain insight into the mechanisms by which BACE1 activity is regulated, we used proteomic methods to search for BACE1-interacting proteins in human neuroblastoma SH-SY5Y cells, which overexpress BACE1. We identified reticulon 4-B (RTN4-B; Nogo-B) as a BACE1-associated membrane protein. Co-immunoprecipitation experiments confirmed a physical association between BACE1 and RTN4-B, RTN4-C (the shortest isoform of RTN-4), and their homologue reticulon 3 (RTN3), both in SH-SY5Y cells and in transfected human embryonic kidney (HEK) 293 cells. Overexpression of these reticulons (RTNs) resulted in a 30-50% reduction in the secretion of both Abeta40 and Abeta42 from HEK293 cells expressing the AD-associated Swedish mutant amyloid precursor protein (APP), but did not affect Abeta secretion from cells expressing the APP beta-C-terminal fragment (beta-CTF), indicating that these RTNs can inhibit BACE1 activity. Furthermore, a BACE1 mutant lacking most of the N-terminal ectodomain also interacted with these RTNs, suggesting that the transmembrane region of BACE1 is critical for the interaction. We also observed a similar interaction between these RTNs and the BACE1 homologue BACE2. Because RTN3 and RTN4-B/C are substantially expressed in neural tissues, our findings suggest that they play important roles in the regulation of BACE1 function and Abeta production in the brain.
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Affiliation(s)
- Kiyoko S Murayama
- Department of Demyelinating Disease and Ageing, National Institute of Neuroscience, NCNP, 4-1-1 Ogawahigashi, Kodaira, Tokyo 187-8502, Japan
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