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Kulatunga DCM, Ranaraja U, Kim EY, Kim RE, Kim DE, Ji KB, Kim MK. A novel APP splice variant-dependent marker system to precisely demarcate maturity in SH-SY5Y cell-derived neurons. Sci Rep 2024; 14:12113. [PMID: 38802572 PMCID: PMC11130256 DOI: 10.1038/s41598-024-63005-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Accepted: 05/23/2024] [Indexed: 05/29/2024] Open
Abstract
SH-SY5Y, a neuroblastoma cell line, can be converted into mature neuronal phenotypes, characterized by the expression of mature neuronal and neurotransmitter markers. However, the mature phenotypes described across multiple studies appear inconsistent. As this cell line expresses common neuronal markers after a simple induction, there is a high chance of misinterpreting its maturity. Therefore, sole reliance on common neuronal markers is presumably inadequate. The Alzheimer's disease (AD) central gene, amyloid precursor protein (APP), has shown contrasting transcript variant dynamics in various cell types. We differentiated SH-SY5Y cells into mature neuron-like cells using a concise protocol and observed the upregulation of total APP throughout differentiation. However, APP transcript variant-1 was upregulated only during the early to middle stages of differentiation and declined in later stages. We identified the maturity state where this post-transcriptional shift occurs, terming it "true maturity." At this stage, we observed a predominant expression of mature neuronal and cholinergic markers, along with a distinct APP variant pattern. Our findings emphasize the necessity of using a differentiation state-sensitive marker system to precisely characterize SH-SY5Y differentiation. Moreover, this study offers an APP-guided, alternative neuronal marker system to enhance the accuracy of the conventional markers.
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Affiliation(s)
- D Chanuka M Kulatunga
- Laboratory of Animal Reproduction and Physiology, College of Agriculture and Life Sciences, Chungnam National University, Yuseong-gu, Daejeon, 34134, Republic of Korea
| | - Umanthi Ranaraja
- Laboratory of Animal Reproduction and Physiology, College of Agriculture and Life Sciences, Chungnam National University, Yuseong-gu, Daejeon, 34134, Republic of Korea
| | | | | | - Dong Ern Kim
- Laboratory of Animal Reproduction and Physiology, College of Agriculture and Life Sciences, Chungnam National University, Yuseong-gu, Daejeon, 34134, Republic of Korea
| | - Kuk Bin Ji
- Laboratory of Animal Reproduction and Physiology, College of Agriculture and Life Sciences, Chungnam National University, Yuseong-gu, Daejeon, 34134, Republic of Korea
| | - Min Kyu Kim
- Laboratory of Animal Reproduction and Physiology, College of Agriculture and Life Sciences, Chungnam National University, Yuseong-gu, Daejeon, 34134, Republic of Korea.
- MK Biotech Inc., Daejeon, Republic of Korea.
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2
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Masi M, Biundo F, Fiou A, Racchi M, Pascale A, Buoso E. The Labyrinthine Landscape of APP Processing: State of the Art and Possible Novel Soluble APP-Related Molecular Players in Traumatic Brain Injury and Neurodegeneration. Int J Mol Sci 2023; 24:ijms24076639. [PMID: 37047617 PMCID: PMC10095589 DOI: 10.3390/ijms24076639] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 03/21/2023] [Accepted: 03/29/2023] [Indexed: 04/05/2023] Open
Abstract
Amyloid Precursor Protein (APP) and its cleavage processes have been widely investigated in the past, in particular in the context of Alzheimer’s Disease (AD). Evidence of an increased expression of APP and its amyloidogenic-related cleavage enzymes, β-secretase 1 (BACE1) and γ-secretase, at the hit axon terminals following Traumatic Brain Injury (TBI), firstly suggested a correlation between TBI and AD. Indeed, mild and severe TBI have been recognised as influential risk factors for different neurodegenerative diseases, including AD. In the present work, we describe the state of the art of APP proteolytic processing, underlining the different roles of its cleavage fragments in both physiological and pathological contexts. Considering the neuroprotective role of the soluble APP alpha (sAPPα) fragment, we hypothesised that sAPPα could modulate the expression of genes of interest for AD and TBI. Hence, we present preliminary experiments addressing sAPPα-mediated regulation of BACE1, Isthmin 2 (ISM2), Tetraspanin-3 (TSPAN3) and the Vascular Endothelial Growth Factor (VEGFA), each discussed from a biological and pharmacological point of view in AD and TBI. We finally propose a neuroprotective interaction network, in which the Receptor for Activated C Kinase 1 (RACK1) and the signalling cascade of PKCβII/nELAV/VEGF play hub roles, suggesting that vasculogenic-targeting therapies could be a feasible approach for vascular-related brain injuries typical of AD and TBI.
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Affiliation(s)
- Mirco Masi
- Computational and Chemical Biology, Italian Institute of Technology, Via Morego 30, 16163 Genova, Italy
| | - Fabrizio Biundo
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, 1300 Morris Park Ave, Bronx, NY 10461, USA
| | - André Fiou
- Department of Drug Sciences, Pharmacology Section, University of Pavia, Via Taramelli 12/14, 27100 Pavia, Italy
| | - Marco Racchi
- Department of Drug Sciences, Pharmacology Section, University of Pavia, Via Taramelli 12/14, 27100 Pavia, Italy
| | - Alessia Pascale
- Department of Drug Sciences, Pharmacology Section, University of Pavia, Via Taramelli 12/14, 27100 Pavia, Italy
| | - Erica Buoso
- Department of Drug Sciences, Pharmacology Section, University of Pavia, Via Taramelli 12/14, 27100 Pavia, Italy
- Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, MA 02118, USA
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3
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A Bioengineering Strategy to Control ADAM10 Activity in Living Cells. Int J Mol Sci 2023; 24:ijms24020917. [PMID: 36674432 PMCID: PMC9863580 DOI: 10.3390/ijms24020917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 12/30/2022] [Accepted: 01/01/2023] [Indexed: 01/06/2023] Open
Abstract
A Disintegrin and Metalloprotease 10, also known as ADAM10, is a cell surface protease ubiquitously expressed in mammalian cells where it cuts several membrane proteins implicated in multiple physiological processes. The dysregulation of ADAM10 expression and function has been implicated in pathological conditions, including Alzheimer's disease (AD). Although it has been suggested that ADAM10 is expressed as a zymogen and the removal of the prodomain results in its activation, other potential mechanisms for the ADAM10 proteolytic function and activation remain unclear. Another suggested mechanism is post-translational modification of the cytoplasmic domain, which regulates ADAM10-dependent protein ectodomain shedding. Therefore, the precise and temporal activation of ADAM10 is highly desirable to reveal the fine details of ADAM10-mediated cleavage mechanisms and protease-dependent therapeutic applications. Here, we present a strategy to control prodomain and cytosolic tail cleavage to regulate ADAM10 shedding activity without the intervention of small endogenous molecule signaling pathways. We generated a series of engineered ADAM10 analogs containing Tobacco Etch Virus protease (TEV) cleavage site (TEVcs), rendering ADAM10 cleavable by TEV. This strategy revealed that, in the absence of other stimuli, the TEV-mediated removal of the prodomain could not activate ADAM10. However, the TEV-mediated cleavage of the cytosolic domain significantly increased ADAM10 activity. Then, we generated ADAM10 with a minimal constitutively catalytic activity that increased significantly in the presence of TEV or after activating a chemically activatable TEV. Our results revealed a bioengineering strategy for controlling the ADAM10 activity in living cells, paving the way to obtain spatiotemporal control of ADAM10. Finally, we proved that our approach of controlling ADAM10 promoted α-secretase activity and the non-amyloidogenic cleavage of amyloid-β precursor protein (APP), thereby increasing the production of the neuroprotective soluble ectodomain (sAPPα). Our bioengineering strategy has the potential to be exploited as a next-generation gene therapy for AD.
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4
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Dar KB, Bhat AH, Amin S, Reshi BA, Zargar MA, Masood A, Ganie SA. Elucidating Critical Proteinopathic Mechanisms and Potential Drug Targets in Neurodegeneration. Cell Mol Neurobiol 2020; 40:313-345. [PMID: 31584139 DOI: 10.1007/s10571-019-00741-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Accepted: 08/06/2019] [Indexed: 12/18/2022]
Abstract
Neurodegeneration entails progressive loss of neuronal structure as well as function leading to cognitive failure, apathy, anxiety, irregular body movements, mood swing and ageing. Proteomic dysregulation is considered the key factor for neurodegeneration. Mechanisms involving deregulated processing of proteins such as amyloid beta (Aβ) oligomerization; tau hyperphosphorylation, prion misfolding; α-synuclein accumulation/lewy body formation, chaperone deregulation, acetylcholine depletion, adenosine 2A (A2A) receptor hyperactivation, secretase deregulation, leucine-rich repeat kinase 2 (LRRK2) mutation and mitochondrial proteinopathies have deeper implications in neurodegenerative disorders. Better understanding of such pathological mechanisms is pivotal for exploring crucial drug targets. Herein, we provide a comprehensive outlook about the diverse proteomic irregularities in Alzheimer's, Parkinson's and Creutzfeldt Jakob disease (CJD). We explicate the role of key neuroproteomic drug targets notably Aβ, tau, alpha synuclein, prions, secretases, acetylcholinesterase (AchE), LRRK2, molecular chaperones, A2A receptors, muscarinic acetylcholine receptors (mAchR), N-methyl-D-aspartate receptor (NMDAR), glial cell line-derived neurotrophic factor (GDNF) family ligands (GFLs) and mitochondrial/oxidative stress-related proteins for combating neurodegeneration and associated cognitive and motor impairment. Cross talk between amyloidopathy, synucleinopathy, tauopathy and several other proteinopathies pinpoints the need to develop safe therapeutics with ability to strike multiple targets in the aetiology of the neurodegenerative disorders. Therapeutics like microtubule stabilisers, chaperones, kinase inhibitors, anti-aggregation agents and antibodies could serve promising regimens for treating neurodegeneration. However, drugs should be target specific, safe and able to penetrate blood-brain barrier.
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Affiliation(s)
- Khalid Bashir Dar
- Department of Clinical Biochemistry, Faculty of Biological Sciences, University of Kashmir, Srinagar, India
- Department of Biochemistry, Faculty of Biological Sciences, University of Kashmir, Srinagar, India
| | - Aashiq Hussain Bhat
- Department of Clinical Biochemistry, Faculty of Biological Sciences, University of Kashmir, Srinagar, India
- Department of Biochemistry, Faculty of Biological Sciences, University of Kashmir, Srinagar, India
| | - Shajrul Amin
- Department of Biochemistry, Faculty of Biological Sciences, University of Kashmir, Srinagar, India
| | - Bilal Ahmad Reshi
- Department of Biotechnology, Faculty of Biological Sciences, University of Kashmir, Srinagar, India
| | - Mohammad Afzal Zargar
- Department of Clinical Biochemistry, Faculty of Biological Sciences, University of Kashmir, Srinagar, India
| | - Akbar Masood
- Department of Biochemistry, Faculty of Biological Sciences, University of Kashmir, Srinagar, India
| | - Showkat Ahmad Ganie
- Department of Clinical Biochemistry, Faculty of Biological Sciences, University of Kashmir, Srinagar, India.
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5
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Truong PH, Ciccotosto GD, Merson TD, Spoerri L, Chuei MJ, Ayers M, Xing YL, Emery B, Cappai R. Amyloid precursor protein and amyloid precursor-like protein 2 have distinct roles in modulating myelination, demyelination, and remyelination of axons. Glia 2018; 67:525-538. [DOI: 10.1002/glia.23561] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 10/18/2018] [Accepted: 10/19/2018] [Indexed: 12/14/2022]
Affiliation(s)
- Phan H. Truong
- Department of Pathology; The University of Melbourne; Melbourne Victoria Australia
- The Bio21 Molecular Science and Biotechnology Institute; The University of Melbourne; Melbourne Victoria Australia
- Department of Pharmacology and Therapeutics; The University of Melbourne; Melbourne Victoria Australia
| | - Giuseppe D. Ciccotosto
- Department of Pathology; The University of Melbourne; Melbourne Victoria Australia
- The Bio21 Molecular Science and Biotechnology Institute; The University of Melbourne; Melbourne Victoria Australia
- Department of Pharmacology and Therapeutics; The University of Melbourne; Melbourne Victoria Australia
| | - Tobias D. Merson
- The Florey Institute of Neuroscience and Mental Health; The University of Melbourne; Melbourne Victoria Australia
| | - Loredana Spoerri
- Department of Pathology; The University of Melbourne; Melbourne Victoria Australia
- The Bio21 Molecular Science and Biotechnology Institute; The University of Melbourne; Melbourne Victoria Australia
| | - Mun Joo Chuei
- Department of Pathology; The University of Melbourne; Melbourne Victoria Australia
- The Bio21 Molecular Science and Biotechnology Institute; The University of Melbourne; Melbourne Victoria Australia
| | - Margaret Ayers
- Department of Pathology; The University of Melbourne; Melbourne Victoria Australia
| | - Yao Lulu Xing
- The Florey Institute of Neuroscience and Mental Health; The University of Melbourne; Melbourne Victoria Australia
| | - Ben Emery
- The Florey Institute of Neuroscience and Mental Health; The University of Melbourne; Melbourne Victoria Australia
- Department of Anatomy and Neuroscience; The University of Melbourne; Melbourne Victoria Australia
| | - Roberto Cappai
- Department of Pathology; The University of Melbourne; Melbourne Victoria Australia
- The Bio21 Molecular Science and Biotechnology Institute; The University of Melbourne; Melbourne Victoria Australia
- Department of Pharmacology and Therapeutics; The University of Melbourne; Melbourne Victoria Australia
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6
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Luu L, Ciccotosto GD, Vella LJ, Cheng L, Roisman LC, Multhaup G, Hill AF, Munter LM, Cappai R. Amyloid Precursor Protein Dimerisation Reduces Neurite Outgrowth. Mol Neurobiol 2018; 56:13-28. [PMID: 29675574 DOI: 10.1007/s12035-018-1070-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 04/09/2018] [Indexed: 02/08/2023]
Abstract
The amyloid precursor protein (APP) undergoes extensive metabolism, and its transport and proteolytic processing can be modulated by its ability to form a homodimer. We have investigated the functional consequences of stabilised APP dimer expression in cells by studying the engineered dimerisation of the APPL17C (residue 17 in Aβ sequence) construct, which is associated with a 30% increase in APP dimer expression, on APP's neurite outgrowth promoting activity. Overexpression of APPL17C in SH-SY5Y cells decreased neurite outgrowth upon retinoic acid differentiation as compared to overexpressing APPWT cells. The APPL17C phenotype was rescued by replacing the APPL17C media with conditioned media from APPWT cells, indicating that the APPL17C mutant is impairing the secretion of a neuritogenic promoting factor. APPL17C had altered transport and was localised in the endoplasmic reticulum. Defining the molecular basis of the APPL17C phenotype showed that RhoA GTPase activity, a negative regulator of neurite outgrowth, was increased in APPL17C cells. RhoA activity was decreased after APPWT conditioned media rescue. Moreover, treatment with the RhoA inhibitor, Y27632, restored a wild-type morphology to the APPL17C cells. Small RNAseq analysis of APPL17C and APPWT cells identified several differentially expressed miRNAs relating to neurite outgrowth. Of these, miR-34a showed the greatest decrease in expression. Lentiviral-mediated overexpression of miR-34a rescued neurite outgrowth in APPL17C cells to APPWT levels and changed RhoA activation. This study has identified a novel link between APP dimerisation and its neuritogenic activity which is mediated by miR-34a expression.
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Affiliation(s)
- Luan Luu
- Department of Pathology, The University of Melbourne, Melbourne, VIC, 3010, Australia
| | - Giuseppe D Ciccotosto
- Department of Pathology, The University of Melbourne, Melbourne, VIC, 3010, Australia.,Department of Pharmacology & Therapeutics, The University of Melbourne, Melbourne, VIC, 3010, Australia.,Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Melbourne, VIC, 3010, Australia
| | - Laura J Vella
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Melbourne, VIC, 3010, Australia
| | - Lesley Cheng
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, VIC, 3086, Australia
| | - Laila C Roisman
- Department of Pathology, The University of Melbourne, Melbourne, VIC, 3010, Australia
| | - Gerhard Multhaup
- Department of Pharmacology & Therapeutics, McGill University, Montreal, QC, H3G 1Y6, Canada
| | - Andrew F Hill
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, VIC, 3086, Australia
| | - Lisa-Marie Munter
- Department of Pharmacology & Therapeutics, McGill University, Montreal, QC, H3G 1Y6, Canada
| | - Roberto Cappai
- Department of Pathology, The University of Melbourne, Melbourne, VIC, 3010, Australia. .,Department of Pharmacology & Therapeutics, The University of Melbourne, Melbourne, VIC, 3010, Australia.
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7
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Endoplasmic Reticulum Stress Induces Myostatin High Molecular Weight Aggregates and Impairs Mature Myostatin Secretion. Mol Neurobiol 2018; 55:8355-8373. [PMID: 29546591 PMCID: PMC6153721 DOI: 10.1007/s12035-018-0997-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Accepted: 03/07/2018] [Indexed: 01/08/2023]
Abstract
Sporadic inclusion body myositis (sIBM) is the most prevalent acquired muscle disorder in the elderly with no defined etiology or effective therapy. Endoplasmic reticulum stress and deposition of myostatin, a secreted negative regulator of muscle growth, have been implicated in disease pathology. The myostatin signaling pathway has emerged as a major target for symptomatic treatment of muscle atrophy. Here, we systematically analyzed the maturation and secretion of myostatin precursor MstnPP and its metabolites in a human muscle cell line. We find that increased MsntPP protein levels induce ER stress. MstnPP metabolites were predominantly retained within the endoplasmic reticulum (ER), also evident in sIBM histology. MstnPP cleavage products formed insoluble high molecular weight aggregates, a process that was aggravated by experimental ER stress. Importantly, ER stress also impaired secretion of mature myostatin. Reduced secretion and aggregation of MstnPP metabolites were not simply caused by overexpression, as both events were also observed in wildtype cells under ER stress. It is tempting to speculate that reduced circulating myostatin growth factor could be one explanation for the poor clinical efficacy of drugs targeting the myostatin pathway in sIBM.
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8
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Lopez-Font I, Boix CP, Zetterberg H, Blennow K, Sáez-Valero J. Alterations in the Balance of Amyloid-β Protein Precursor Species in the Cerebrospinal Fluid of Alzheimer's Disease Patients. J Alzheimers Dis 2018; 57:1281-1291. [PMID: 28372336 DOI: 10.3233/jad-161275] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
We recently demonstrated that soluble forms of the amyloid-β protein precursor (sAβPP) assemble into multimeric complexes in cerebrospinal fluid (CSF), which contributes to the underestimation of specific sAβPP species when assessed by ELISA. To circumvent this issue, we analyzed by SDS-PAGE large fragments of sAβPP and their variants in the CSF from Alzheimer's disease (AD; n = 20) and control (n = 20) subjects, probing with specific antibodies against particular domains. Similar levels of sAβPPα and sAβPPβ protein were found in CSF samples from AD and controls, yet there appeared to be a shift in the balance of the soluble full-length AβPP (sAβPPf) species in AD samples, with a decrease in the proportion of the lower (∼100 kDa) band relative to the upper (∼120 kDa) band. Similar differences were observed in the contribution of the major KPI-immunoreactive AβPP species. CSF samples also displayed differences in the correlations of AβPP species with classical AD biomarkers, particularly with respect to the Aβ42 peptide. The differences reveal alterations that probably reflect pathophysiological changes in the brain.
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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), Spain
| | - Claudia P Boix
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, Sant Joan d'Alacant, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Henrik Zetterberg
- Clinical Neurochemistry Laboratory, Inst. of Neuroscience and Physiology, University of Gothenburg, Mölndal Campus, Sweden.,Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, London, UK
| | - Kaj Blennow
- Clinical Neurochemistry Laboratory, Inst. of Neuroscience and Physiology, University of Gothenburg, Mölndal Campus, Sweden
| | - 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), Spain
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9
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García-Ayllón MS, Lopez-Font I, Boix CP, Fortea J, Sánchez-Valle R, Lleó A, Molinuevo JL, Zetterberg H, Blennow K, Sáez-Valero J. C-terminal fragments of the amyloid precursor protein in cerebrospinal fluid as potential biomarkers for Alzheimer disease. Sci Rep 2017; 7:2477. [PMID: 28559572 PMCID: PMC5449401 DOI: 10.1038/s41598-017-02841-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 04/18/2017] [Indexed: 11/15/2022] Open
Abstract
This study assesses whether C-terminal fragments (CTF) of the amyloid precursor protein (APP) are present in cerebrospinal fluid (CSF) and their potential as biomarkers for Alzheimer’s disease (AD). Immunoprecipitation and simultaneous assay by Western blotting using multiplex fluorescence imaging with specific antibodies against particular domains served to characterize CTFs of APP in human CSF. We demonstrate that APP-CTFs are detectable in human CSF, being the most abundant a 25-kDa fragment, probably resulting from proteolytic processing by η-secretase. The level of the 25-kDa APP-CTF was evaluated in three independent CSF sample sets of patients and controls. The CSF level of this 25-kDa CTF is higher in subjects with autosomal dominant AD linked to PSEN1 mutations, in demented Down syndrome individuals and in sporadic AD subjects compared to age-matched controls. Our data suggest that APP-CTF could be a potential diagnostic biomarker for AD.
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Affiliation(s)
- María-Salud García-Ayllón
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, 03550, Sant Joan d'Alacant, Alicante, España.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Sant Joan d'Alacant, 03550, Alicante, España.,Unidad de Investigación, Hospital General Universitario de Elche, FISABIO, Elche, Spain
| | - Inmaculada Lopez-Font
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, 03550, Sant Joan d'Alacant, Alicante, España.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Sant Joan d'Alacant, 03550, Alicante, España
| | - Claudia P Boix
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, 03550, Sant Joan d'Alacant, Alicante, España.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Sant Joan d'Alacant, 03550, Alicante, España
| | - Juan Fortea
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Sant Joan d'Alacant, 03550, Alicante, España.,Memory Unit, Neurology Department, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain.,Down Medical Center, Fundació Catalana Síndrome de Down, Barcelona, Spain
| | - Raquel Sánchez-Valle
- Alzheimer's Disease and Other Cognitive Disorders Unit, Neurology Service, Hospital Clinic, 08036, Barcelona, Spain
| | - Alberto Lleó
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Sant Joan d'Alacant, 03550, Alicante, España.,Memory Unit, Neurology Department, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - José-Luis Molinuevo
- Alzheimer's Disease and Other Cognitive Disorders Unit, Neurology Service, Hospital Clinic, 08036, Barcelona, Spain
| | - Henrik Zetterberg
- Clinical Neurochemistry Laboratory, Sahlgrenska University Hospital, Mölndal, Sweden.,Institute of Neuroscience and Physiology, University of Gothenburg, Mölndal Campus, Sweden.,Department of Molecular Neuroscience, Institute of Neurology, University College London, London, UK
| | - Kaj Blennow
- Clinical Neurochemistry Laboratory, Sahlgrenska University Hospital, Mölndal, Sweden.,Institute of Neuroscience and Physiology, University of Gothenburg, Mölndal Campus, Sweden
| | - Javier Sáez-Valero
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, 03550, Sant Joan d'Alacant, Alicante, España. .,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Sant Joan d'Alacant, 03550, Alicante, España.
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10
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Montagna E, Dorostkar MM, Herms J. The Role of APP in Structural Spine Plasticity. Front Mol Neurosci 2017; 10:136. [PMID: 28539872 PMCID: PMC5423954 DOI: 10.3389/fnmol.2017.00136] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 04/21/2017] [Indexed: 11/15/2022] Open
Abstract
Amyloid precursor protein (APP) is a transmembrane protein highly expressed in neurons. The full-length protein has cell-adhesion and receptor-like properties, which play roles in synapse formation and stability. Furthermore, APP can be cleaved by several proteases into numerous fragments, many of which affect synaptic function and stability. This review article focuses on the mechanisms of APP in structural spine plasticity, which encompasses the morphological alterations at excitatory synapses. These occur as changes in the number and morphology of dendritic spines, which correspond to the postsynaptic compartment of excitatory synapses. Both overexpression and knockout (KO) of APP lead to impaired synaptic plasticity. Recent data also suggest a role of APP in the regulation of astrocytic D-serine homeostasis, which in turn regulates synaptic plasticity.
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Affiliation(s)
- Elena Montagna
- Department for Translational Brain Research, German Center for Neurodegenerative Diseases (DZNE), Ludwig-Maximilian-University MunichMunich, Germany
| | - Mario M Dorostkar
- Center for Neuropathology and Prion Research, Ludwig-Maximilian-University MunichMunich, Germany
| | - Jochen Herms
- Department for Translational Brain Research, German Center for Neurodegenerative Diseases (DZNE), Ludwig-Maximilian-University MunichMunich, Germany.,Center for Neuropathology and Prion Research, Ludwig-Maximilian-University MunichMunich, Germany.,Munich Cluster of Systems Neurology (SyNergy), Ludwig-Maximilian-University MunichMunich, Germany
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11
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APLP1 Is a Synaptic Cell Adhesion Molecule, Supporting Maintenance of Dendritic Spines and Basal Synaptic Transmission. J Neurosci 2017; 37:5345-5365. [PMID: 28450540 DOI: 10.1523/jneurosci.1875-16.2017] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Revised: 02/22/2017] [Accepted: 03/24/2017] [Indexed: 12/19/2022] Open
Abstract
The amyloid precursor protein (APP), a key player in Alzheimer's disease, belongs to the family of synaptic adhesion molecules (SAMs) due to its impact on synapse formation and synaptic plasticity. These functions are mediated by both the secreted APP ectodomain that acts as a neurotrophic factor and full-length APP forming trans-cellular dimers. Two homologs of APP exist in mammals: the APP like proteins APLP1 and APLP2, exhibiting functions that partly overlap with those of APP. Here we tested whether APLP1 and APLP2 also show features of SAMs. We found that all three family members were upregulated during postnatal development coinciding with synaptogenesis. We observed presynaptic and postsynaptic localization of all APP family members and could show that heterologous expression of APLP1 or APLP2 in non-neuronal cells induces presynaptic differentiation in contacting axons of cocultured neurons, similar to APP and other SAMs. Moreover, APP/APLPs all bind to synaptic-signaling molecules, such as MINT/X11. Furthermore, we report that aged APLP1 knock-out mice show impaired basal transmission and a reduced mEPSC frequency, likely resulting from reduced spine density. This demonstrates an essential nonredundant function of APLP1 at the synapse. Compared to APP, APLP1 exhibits increased trans-cellular binding and elevated cell-surface levels due to reduced endocytosis. In conclusion, our results establish that APLPs show typical features of SAMs and indicate that increased surface expression, as observed for APLP1, is essential for proper synapse formation in vitro and synapse maintenance in vivoSIGNIFICANCE STATEMENT According to the amyloid-cascade hypothesis, Alzheimer's disease is caused by the accumulation of Aβ peptides derived from sequential cleavage of the amyloid precursor protein (APP) by β-site APP cleaving enzyme 1 (BACE1) and γ-secretase. Here we show that all mammalian APP family members (APP, APLP1, and APLP2) exhibit synaptogenic activity, involving trans-synaptic dimerization, similar to other synaptic cell adhesion molecules, such as Neuroligin/Neurexin. Importantly, our study revealed that the loss of APLP1, which is one of the major substrates of BACE1, causes reduced spine density in aged mice. Because some therapeutic interventions target APP processing (e.g., BACE inhibitors), those strategies may alter APP/APLP physiological function. This should be taken into account for the development of pharmaceutical treatments of Alzheimer's disease.
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Vasques JF, Heringer PVB, Gonçalves RGDJ, Campello-Costa P, Serfaty CA, Faria-Melibeu ADC. Monocular denervation of visual nuclei modulates APP processing and sAPPα production: A possible role on neural plasticity. Int J Dev Neurosci 2017; 60:16-25. [PMID: 28323038 DOI: 10.1016/j.ijdevneu.2017.03.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 03/06/2017] [Accepted: 03/06/2017] [Indexed: 12/13/2022] Open
Abstract
Amyloid precursor protein (APP) is essential to physiological processes such as synapse formation and neural plasticity. Sequential proteolysis of APP by beta- and gamma-secretases generates amyloid-beta peptide (Aβ), the main component of senile plaques in Alzheimer Disease. Alternative APP cleavage by alpha-secretase occurs within Aβ domain, releasing soluble α-APP (sAPPα), a neurotrophic fragment. Among other functions, sAPPα is important to synaptogenesis, neural survival and axonal growth. APP and sAPPα levels are increased in models of neuroplasticity, which suggests an important role for APP and its metabolites, especially sAPPα, in the rearranging brain. In this work we analyzed the effects of monocular enucleation (ME), a classical model of lesion-induced plasticity, upon APP content, processing and also in secretases levels. Besides, we addressed whether α-secretase activity is crucial for retinotectal remodeling after ME. Our results showed that ME induced a transient reduction in total APP content. We also detected an increase in α-secretase expression and in sAPP production concomitant with a reduction in Aβ and β-secretase contents. These data suggest that ME facilitates APP processing by the non-amyloidogenic pathway, increasing sAPPα levels. Indeed, the pharmacological inhibition of α-secretase activity reduced the axonal sprouting of ipsilateral retinocollicular projections from the intact eye after ME, suggesting that sAPPα is necessary for synaptic structural rearrangement. Understanding how APP processing is regulated under lesion conditions may provide new insights into APP physiological role on neural plasticity.
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Affiliation(s)
- Juliana Ferreira Vasques
- Programa de Neurociências, Departamento de Neurobiologia, Instituto de Biologia, Universidade Federal Fluminense, CEP 24001-970, Niterói 100180, RJ, Brazil
| | - Pedro Vinícius Bastos Heringer
- Programa de Neurociências, Departamento de Neurobiologia, Instituto de Biologia, Universidade Federal Fluminense, CEP 24001-970, Niterói 100180, RJ, Brazil
| | - Renata Guedes de Jesus Gonçalves
- Programa de Neurociências, Departamento de Neurobiologia, Instituto de Biologia, Universidade Federal Fluminense, CEP 24001-970, Niterói 100180, RJ, Brazil
| | - Paula Campello-Costa
- Programa de Neurociências, Departamento de Neurobiologia, Instituto de Biologia, Universidade Federal Fluminense, CEP 24001-970, Niterói 100180, RJ, Brazil
| | - Claudio Alberto Serfaty
- Programa de Neurociências, Departamento de Neurobiologia, Instituto de Biologia, Universidade Federal Fluminense, CEP 24001-970, Niterói 100180, RJ, Brazil
| | - Adriana da Cunha Faria-Melibeu
- Programa de Neurociências, Departamento de Neurobiologia, Instituto de Biologia, Universidade Federal Fluminense, CEP 24001-970, Niterói 100180, RJ, Brazil.
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13
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Paschkowsky S, Hamzé M, Oestereich F, Munter LM. Alternative Processing of the Amyloid Precursor Protein Family by Rhomboid Protease RHBDL4. J Biol Chem 2016; 291:21903-21912. [PMID: 27563067 DOI: 10.1074/jbc.m116.753582] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Indexed: 12/13/2022] Open
Abstract
The amyloid precursor protein (APP) is an ubiquitously expressed cell surface protein and a key molecule in the etiology of Alzheimer disease. Amyloidogenic processing of APP through secretases leads to the generation of toxic amyloid β (Aβ) peptides, which are regarded as the molecular cause of the disease. We report here an alternative processing pathway of APP through the mammalian intramembrane rhomboid protease RHBDL4. RHBDL4 efficiently cleaves APP inside the cell, thus bypassing APP from amyloidogenic processing, leading to reduced Aβ levels. RHBDL4 cleaves APP multiple times in the ectodomain, resulting in several N- and C-terminal fragments that are not further degraded by classical APP secretases. Knockdown of endogenous RHBDL4 results in decreased levels of C-terminal fragments derived from endogenous APP. Similarly, we found the APP family members APLP1 and APLP2 to be substrates of RHBDL4. We conclude that RHBDL4-mediated APP processing provides insight into APP and rhomboid physiology and qualifies for further investigations to elaborate its impact on Alzheimer disease pathology.
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Affiliation(s)
| | - Mehdi Hamzé
- From the Department of Pharmacology and Therapeutics and
| | - Felix Oestereich
- From the Department of Pharmacology and Therapeutics and Integrated Program in Neuroscience, McGill University, Montreal, Quebec H3G 0B1, Canada
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14
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Andrew RJ, Kellett KAB, Thinakaran G, Hooper NM. A Greek Tragedy: The Growing Complexity of Alzheimer Amyloid Precursor Protein Proteolysis. J Biol Chem 2016; 291:19235-44. [PMID: 27474742 DOI: 10.1074/jbc.r116.746032] [Citation(s) in RCA: 135] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Proteolysis of the amyloid precursor protein (APP) liberates various fragments including the proposed initiator of Alzheimer disease-associated dysfunctions, amyloid-β. However, recent evidence suggests that the accepted view of APP proteolysis by the canonical α-, β-, and γ-secretases is simplistic, with the discovery of a number of novel APP secretases (including δ- and η-secretases, alternative β-secretases) and additional metabolites, some of which may also cause synaptic dysfunction. Furthermore, various proteins have been identified that interact with APP and modulate its cleavage by the secretases. Here, we give an overview of the increasingly complex picture of APP proteolysis.
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Affiliation(s)
- Robert J Andrew
- From the Departments of Neurobiology, Neurology, and Pathology, The University of Chicago, Chicago, Illinois 60637 and
| | - Katherine A B Kellett
- the Division of Neuroscience and Experimental Psychology, Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Gopal Thinakaran
- From the Departments of Neurobiology, Neurology, and Pathology, The University of Chicago, Chicago, Illinois 60637 and
| | - Nigel M Hooper
- the Division of Neuroscience and Experimental Psychology, Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
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15
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Willem M, Tahirovic S, Busche MA, Ovsepian SV, Chafai M, Kootar S, Hornburg D, Evans LDB, Moore S, Daria A, Hampel H, Müller V, Giudici C, Nuscher B, Wenninger-Weinzierl A, Kremmer E, Heneka MT, Thal DR, Giedraitis V, Lannfelt L, Müller U, Livesey FJ, Meissner F, Herms J, Konnerth A, Marie H, Haass C. η-Secretase processing of APP inhibits neuronal activity in the hippocampus. Nature 2015; 526:443-7. [PMID: 26322584 DOI: 10.1038/nature14864] [Citation(s) in RCA: 272] [Impact Index Per Article: 30.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 06/25/2015] [Indexed: 12/24/2022]
Abstract
Alzheimer disease (AD) is characterized by the accumulation of amyloid plaques, which are predominantly composed of amyloid-β peptide. Two principal physiological pathways either prevent or promote amyloid-β generation from its precursor, β-amyloid precursor protein (APP), in a competitive manner. Although APP processing has been studied in great detail, unknown proteolytic events seem to hinder stoichiometric analyses of APP metabolism in vivo. Here we describe a new physiological APP processing pathway, which generates proteolytic fragments capable of inhibiting neuronal activity within the hippocampus. We identify higher molecular mass carboxy-terminal fragments (CTFs) of APP, termed CTF-η, in addition to the long-known CTF-α and CTF-β fragments generated by the α- and β-secretases ADAM10 (a disintegrin and metalloproteinase 10) and BACE1 (β-site APP cleaving enzyme 1), respectively. CTF-η generation is mediated in part by membrane-bound matrix metalloproteinases such as MT5-MMP, referred to as η-secretase activity. η-Secretase cleavage occurs primarily at amino acids 504-505 of APP695, releasing a truncated ectodomain. After shedding of this ectodomain, CTF-η is further processed by ADAM10 and BACE1 to release long and short Aη peptides (termed Aη-α and Aη-β). CTFs produced by η-secretase are enriched in dystrophic neurites in an AD mouse model and in human AD brains. Genetic and pharmacological inhibition of BACE1 activity results in robust accumulation of CTF-η and Aη-α. In mice treated with a potent BACE1 inhibitor, hippocampal long-term potentiation was reduced. Notably, when recombinant or synthetic Aη-α was applied on hippocampal slices ex vivo, long-term potentiation was lowered. Furthermore, in vivo single-cell two-photon calcium imaging showed that hippocampal neuronal activity was attenuated by Aη-α. These findings not only demonstrate a major functionally relevant APP processing pathway, but may also indicate potential translational relevance for therapeutic strategies targeting APP processing.
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Affiliation(s)
- Michael Willem
- Biomedical Center (BMC), Ludwig-Maximilians-University Munich, 81377 Munich, Germany
| | - Sabina Tahirovic
- German Center for Neurodegenerative Diseases (DZNE) Munich, 81377 Munich, Germany
| | - Marc Aurel Busche
- Department of Psychiatry and Psychotherapy, Technische Universität München, 81675 Munich, Germany.,Institute of Neuroscience, Technische Universität München, 80802 Munich, Germany.,Munich Cluster for Systems Neurology (SyNergy), Ludwig-Maximilians-University Munich, 81377 Munich, Germany
| | - Saak V Ovsepian
- German Center for Neurodegenerative Diseases (DZNE) Munich, 81377 Munich, Germany
| | - Magda Chafai
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), Centre National de la Recherche Scientifique (CNRS), Université de Nice Sophia Antipolis, UMR 7275, 06560 Valbonne, France
| | - Scherazad Kootar
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), Centre National de la Recherche Scientifique (CNRS), Université de Nice Sophia Antipolis, UMR 7275, 06560 Valbonne, France
| | - Daniel Hornburg
- Max Planck Institute of Biochemistry, Martinsried 82152, Germany
| | - Lewis D B Evans
- Gurdon Institute, Cambridge Stem Cell Institute &Department of Biochemistry, University of Cambridge, Cambridge CB2 1QN, UK
| | - Steven Moore
- Gurdon Institute, Cambridge Stem Cell Institute &Department of Biochemistry, University of Cambridge, Cambridge CB2 1QN, UK
| | - Anna Daria
- Biomedical Center (BMC), Ludwig-Maximilians-University Munich, 81377 Munich, Germany
| | - Heike Hampel
- Biomedical Center (BMC), Ludwig-Maximilians-University Munich, 81377 Munich, Germany
| | - Veronika Müller
- Biomedical Center (BMC), Ludwig-Maximilians-University Munich, 81377 Munich, Germany
| | - Camilla Giudici
- Biomedical Center (BMC), Ludwig-Maximilians-University Munich, 81377 Munich, Germany
| | - Brigitte Nuscher
- Biomedical Center (BMC), Ludwig-Maximilians-University Munich, 81377 Munich, Germany
| | | | - Elisabeth Kremmer
- German Center for Neurodegenerative Diseases (DZNE) Munich, 81377 Munich, Germany.,Munich Cluster for Systems Neurology (SyNergy), Ludwig-Maximilians-University Munich, 81377 Munich, Germany.,Institute of Molecular Immunology, German Research Center for Environmental Health, 81377 Munich, Germany
| | - Michael T Heneka
- Department of Neurology, Clinical Neuroscience Unit, University of Bonn, 53127 Bonn, Germany.,German Center for Neurodegenerative Diseases (DZNE) Bonn, 53175 Bonn, Germany
| | - Dietmar R Thal
- Institute of Pathology - Laboratory for Neuropathology, University of Ulm, 89081 Ulm, Germany
| | - Vilmantas Giedraitis
- Department of Public Health/Geriatrics, Uppsala University, 751 85 Uppsala, Sweden
| | - Lars Lannfelt
- Department of Public Health/Geriatrics, Uppsala University, 751 85 Uppsala, Sweden
| | - Ulrike Müller
- Institute for Pharmacy and Molecular Biotechnology IPMB, Functional Genomics, University of Heidelberg, 69120 Heidelberg, Germany
| | - Frederick J Livesey
- Gurdon Institute, Cambridge Stem Cell Institute &Department of Biochemistry, University of Cambridge, Cambridge CB2 1QN, UK
| | - Felix Meissner
- Max Planck Institute of Biochemistry, Martinsried 82152, Germany
| | - Jochen Herms
- German Center for Neurodegenerative Diseases (DZNE) Munich, 81377 Munich, Germany
| | - Arthur Konnerth
- Institute of Neuroscience, Technische Universität München, 80802 Munich, Germany.,Munich Cluster for Systems Neurology (SyNergy), Ludwig-Maximilians-University Munich, 81377 Munich, Germany
| | - Hélène Marie
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), Centre National de la Recherche Scientifique (CNRS), Université de Nice Sophia Antipolis, UMR 7275, 06560 Valbonne, France
| | - Christian Haass
- Biomedical Center (BMC), Ludwig-Maximilians-University Munich, 81377 Munich, Germany.,German Center for Neurodegenerative Diseases (DZNE) Munich, 81377 Munich, Germany.,Munich Cluster for Systems Neurology (SyNergy), Ludwig-Maximilians-University Munich, 81377 Munich, Germany
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16
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Najem D, Bamji-Mirza M, Chang N, Liu QY, Zhang W. Insulin resistance, neuroinflammation, and Alzheimer's disease. Rev Neurosci 2015; 25:509-25. [PMID: 24622783 DOI: 10.1515/revneuro-2013-0050] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Accepted: 02/13/2014] [Indexed: 01/02/2023]
Abstract
Alzheimer's disease (AD) is the most common form of dementia. Pathologically, it is characterized by degeneration of neurons and synapses, the deposition of extracellular plaques consisting of aggregated amyloid-β (Aβ) peptides, and intracellular neurofibrillary tangles made up of hyperphosphorylated tau protein. Recently, the spotlights have been centered on two characteristics of AD, neuroinflammation and insulin resistance. Because both of these pathways play roles in synaptic dysfunction and neurodegeneration, they become potential targets for therapeutic intervention that could impede the progression of the disease. Here, we present an overview of the traditional amyloid hypothesis, as well as emerging data on both inflammatory and impaired insulin signaling pathways in AD. It becomes evident that more than one concurrent treatment can be synergistic and various combinations should be discussed as a potential therapeutic strategy to correct the anomalies in AD. Insulin resistance, Aβ/tau pathologies, neuroinflammation, and dysregulation of central nervous system homeostasis are intertwined processes that together create the complex pathology of AD and should be considered as a whole picture.
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17
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The multifaceted nature of amyloid precursor protein and its proteolytic fragments: friends and foes. Acta Neuropathol 2015; 129:1-19. [PMID: 25287911 DOI: 10.1007/s00401-014-1347-2] [Citation(s) in RCA: 154] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2014] [Revised: 09/26/2014] [Accepted: 09/26/2014] [Indexed: 12/29/2022]
Abstract
The amyloid precursor protein (APP) has occupied a central position in Alzheimer's disease (AD) pathophysiology, in large part due to the seminal role of amyloid-β peptide (Aβ), a proteolytic fragment derived from APP. Although the contribution of Aβ to AD pathogenesis is accepted by many in the research community, recent studies have unveiled a more complicated picture of APP's involvement in neurodegeneration in that other APP-derived fragments have been shown to exert pathological influences on neuronal function. However, not all APP-derived peptides are neurotoxic, and some even harbor neuroprotective effects. In this review, we will explore this complex picture by first discussing the pleiotropic effects of the major APP-derived peptides cleaved by multiple proteases, including soluble APP peptides (sAPPα, sAPPβ), various C- and N-terminal fragments, p3, and APP intracellular domain fragments. In addition, we will highlight two interesting sequences within APP that likely contribute to this duality in APP function. First, it has been found that caspase-mediated cleavage of APP in the cytosolic region may release a cytotoxic peptide, C31, which plays a role in synapse loss and neuronal death. Second, recent studies have implicated the -YENPTY- motif in the cytoplasmic region as a domain that modulates several APP activities through phosphorylation and dephosphorylation of the first tyrosine residue. Thus, this review summarizes the current understanding of various APP proteolytic products and the interplay among them to gain deeper insights into the possible mechanisms underlying neurodegeneration and AD pathophysiology.
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18
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Merezhko M, Muggalla P, Nykänen NP, Yan X, Sakha P, Huttunen HJ. Multiplex assay for live-cell monitoring of cellular fates of amyloid-β precursor protein (APP). PLoS One 2014; 9:e98619. [PMID: 24932508 PMCID: PMC4059622 DOI: 10.1371/journal.pone.0098619] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 05/05/2014] [Indexed: 11/19/2022] Open
Abstract
Amyloid-β precursor protein (APP) plays a central role in pathogenesis of Alzheimer's disease. APP has a short half-life and undergoes complex proteolytic processing that is highly responsive to various stimuli such as changes in cellular lipid or energy homeostasis. Cellular trafficking of APP is controlled by its large protein interactome, including dozens of cytosolic adaptor proteins, and also by interactions with lipids. Currently, cellular regulation of APP is mostly studied based on appearance of APP-derived proteolytic fragments to conditioned media and cellular extracts. Here, we have developed a novel live-cell assay system based on several indirect measures that reflect altered APP trafficking and processing in cells. Protein-fragment complementation assay technology for detection of APP-BACE1 protein-protein interaction forms the core of the new assay. In a multiplex form, the assay can measure four endpoints: total cellular APP level, total secreted sAPP level in media, APP-BACE1 interaction in cells and in exosomes released by the cells. Functional validation of the assay with pharmacological and genetic tools revealed distinct patterns of cellular fates of APP, with immediate mechanistic implications. This new technology will facilitate functional genomics studies of late-onset Alzheimer's disease, drug discovery efforts targeting APP and characterization of the physiological functions of APP and its proteolytic fragments.
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Affiliation(s)
- Maria Merezhko
- Neuroscience Center, University of Helsinki, Helsinki, Finland
| | | | | | - Xu Yan
- Neuroscience Center, University of Helsinki, Helsinki, Finland
| | - Prasanna Sakha
- Neuroscience Center, University of Helsinki, Helsinki, Finland
| | - Henri J. Huttunen
- Neuroscience Center, University of Helsinki, Helsinki, Finland
- * E-mail: .
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Dawkins E, Gasperini R, Hu Y, Cui H, Vincent AJ, Bolós M, Young KM, Foa L, Small DH. The N-terminal fragment of the β-amyloid precursor protein of Alzheimer's disease (N-APP) binds to phosphoinositide-rich domains on the surface of hippocampal neurons. J Neurosci Res 2014; 92:1478-89. [PMID: 24916405 DOI: 10.1002/jnr.23422] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 04/22/2014] [Accepted: 05/09/2014] [Indexed: 11/11/2022]
Abstract
The function of the β-amyloid precursor protein (APP) of Alzheimer's disease is poorly understood. The secreted ectodomain fragment of APP (sAPPα) can be readily cleaved to produce a small N-terminal fragment (N-APP) that contains heparin-binding and metal-binding domains and that has been found to have biological activity. In the present study, we examined whether N-APP can bind to lipids. We found that N-APP binds selectively to phosphoinositides (PIPs) but poorly to most other lipids. Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2 )-rich microdomains were identified on the extracellular surface of neurons and glia in primary hippocampal cultures. N-APP bound to neurons and colocalized with PIPs on the cell surface. Furthermore, the binding of N-APP to neurons increased the level of cell-surface PI(4,5)P2 and phosphatidylinositol 3,4,5-trisphosphate. However, PIPs were not the principal cell-surface binding site for N-APP, because N-APP binding to neurons was not inhibited by a short-acyl-chain PIP analogue, and N-APP did not bind to glial cells which also possessed PI(4,5)P2 on the cell surface. The data are explained by a model in which N-APP binds to two distinct components on neurons, one of which is an unidentified receptor and the second of which is a PIP lipid, which binds more weakly to a distinct site within N-APP. Our data provide further support for the idea that N-APP may be an important mediator of APP's biological activity.
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Affiliation(s)
- Edgar Dawkins
- Menzies Research Institute Tasmania, University of Tasmania, Hobart, Tasmania, Australia
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Apolipoprotein E, amyloid-beta, and neuroinflammation in Alzheimer's disease. Neurosci Bull 2014; 30:317-30. [PMID: 24652457 DOI: 10.1007/s12264-013-1422-z] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2013] [Accepted: 01/23/2014] [Indexed: 12/21/2022] Open
Abstract
Alzheimer's disease (AD) is characterized by the accumulation and deposition of amyloid-beta (Aβ) peptides in the brain. Neuroinflammation occurs in the AD brain and plays a critical role in the neurodegenerative pathology. Particularly, Aβ evokes an inflammatory response that leads to synaptic dysfunction, neuronal death, and neurodegeneration. Apolipoprotein E (ApoE) proteins are involved in cholesterol transport, Aβ binding and clearance, and synaptic functions in the brain. The ApoE4 isoform is a key risk factor for AD, while the ApoE2 isoform has a neuroprotective effect. However, studies have reached different conclusions about the roles of the isoforms; some show that both ApoE3 and ApoE4 have anti-inflammatory effects, while others show that ApoE4 causes a predisposition to inflammation or promotes an inflammatory response following lipopolysaccharide treatment. These discrepancies may result from the differences in models, cell types, experimental conditions, and inflammatory stimuli used. Further, little was known about the role of ApoE isoforms in the Aβ-induced inflammatory response and in the neuroinflammation of AD. Our recent work showed that ApoE isoforms differentially regulate and modify the Aβ-induced inflammatory response in neural cells, with ApoE2 suppressing and ApoE4 promoting the response. In this article, we review the roles, mechanisms, and interrelations among Aβ, ApoE, and neuroinflammation in AD.
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Analysis of the overall structure of the multi-domain amyloid precursor protein (APP). PLoS One 2013; 8:e81926. [PMID: 24324731 PMCID: PMC3852973 DOI: 10.1371/journal.pone.0081926] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 10/18/2013] [Indexed: 11/19/2022] Open
Abstract
The amyloid precursor protein (APP) and its processing by the α-, β- and γ-secretases is widely believed to play a central role during the development of Alzheimer´s disease. The three-dimensional structure of the entire protein, its physiologic function and the regulation of its proteolytic processing remain, however, largely unclear to date. To gain a deeper understanding of the structure of APP that underlies all of its functions, we first cloned and recombinantly expressed different constructs in E. coli. Using limited proteolysis followed by mass spectrometry and Edman degradation as well as analytical gel permeation chromatography coupled static light scattering, we experimentally analyzed the structural domain boundaries and determined that the large ectodomain of APP consists of exactly two rigidly folded domains - the E1-domain (Leu18-Ala190) and the E2-domain (Ser295-Asp500). Both, the acidic domain (AcD) connecting E1 and E2 as well as the juxtamembrane region (JMR) connecting E2 to the single transmembrane helix are highly flexible and extended. We identified in-between the E1-domain and the AcD an additional domain of conservation and partial flexibility that we termed extension domain (ED, Glu191-Glu227). Using Bio-layer interferometry, pull-down assays and analytical gel filtration experiments we demonstrated that the E1-domain does not tightly interact with the E2-domain, both in the presence and in the absence of heparin. APP hence forms an extended molecule that is flexibly tethered to the membrane. Its multi-domain architecture enables together with the many known functionalities the concomitant performance of several, independent functions, which might be regulated by cellular, compartment specific pH-changes.
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Iyer A, van Scheppingen J, Anink J, Milenkovic I, Kovács GG, Aronica E. Developmental patterns of DR6 in normal human hippocampus and in Down syndrome. J Neurodev Disord 2013; 5:10. [PMID: 23618225 PMCID: PMC3666921 DOI: 10.1186/1866-1955-5-10] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2012] [Accepted: 04/04/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Death receptor 6 (DR6) is highly expressed in the human brain: it has been shown to induce axon pruning and neuron death via distinct caspases and to mediate axonal degeneration through binding to N-terminal β amyloid precursor protein (N-APP). METHODS We investigated the expression of DR6 during prenatal and postnatal development in human hippocampus and temporal cortex by immunocytochemistry and Western blot analysis (118 normal human brain specimens; 9 to 41 gestational weeks; 1 day to 7 months postnatally; 3 to 91 years). To investigate the role of N-APP/DR6/caspase 6 pathway in the development of hippocampal Alzheimer's disease (AD)-associated pathology, we examined DR6 immunoreactivity (IR) in the developing hippocampus from patients with Down syndrome (DS; 48 brain specimens; 14 to 41 gestational weeks; 7 days to 8 months postnatally; 15 to 64 years) and in adults with DS and AD. RESULTS DR6 was highly expressed in human adult hippocampus and temporal cortex: we observed consistent similar temporal and spatial expression in both control and DS brain. Western blot analysis of total homogenates of temporal cortex and hippocampus showed developmental regulation of DR6. In the hippocampus, DR6 IR was first apparent in the stratum lacunosum-moleculare at 16 weeks of gestation, followed by stratum oriens, radiatum, pyramidale (CA1 to CA4) and molecular layer of the dentate gyrus between 21 and 23 gestational weeks, reaching a pattern similar to adult hippocampus around birth. Increased DR6 expression in dystrophic neurites was detected focally in a 15-year-old DS patient. Abnormal DR6 expression pattern, with increased expression within dystrophic neurites in and around amyloid plaques was observed in adult DS patients with widespread AD-associated neurodegeneration and was similar to the pattern observed in AD hippocampus. Double-labeling experiments demonstrated the colocalization, in dystrophic neurites, of DR6 with APP. We also observed colocalization with hyper-phosphorylated Tau and with caspase 6 (increased in hippocampus with AD pathology) in plaque-associated dystrophic neurites and within the white matter. CONCLUSIONS These findings demonstrate a developmental regulation of DR6 in human hippocampus and suggest an abnormal activation of the N-APP/DR6/caspase 6 pathway, which can contribute to initiation or progression of hippocampal AD-associated pathology.
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Affiliation(s)
- Anand Iyer
- Department of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, Amsterdam, AZ 1105, The Netherlands
| | - Jackelien van Scheppingen
- Department of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, Amsterdam, AZ 1105, The Netherlands
| | - Jasper Anink
- Department of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, Amsterdam, AZ 1105, The Netherlands
| | - Ivan Milenkovic
- Institute of Neurology, Medical University of Vienna, Vienna, Austria
| | - Gabor G Kovács
- Institute of Neurology, Medical University of Vienna, Vienna, Austria
| | - Eleonora Aronica
- Department of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, Amsterdam, AZ 1105, The Netherlands.,SEIN - Stichting Epilepsie Instellingen Nederland, Heemstede, The Netherlands.,Swammerdam Institute for Life Sciences, Center for Neuroscience, University of Amsterdam, Amsterdam, The Netherlands
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Kok WM, Cottam JM, Ciccotosto GD, Miles LA, Karas JA, Scanlon DB, Roberts BR, Parker MW, Cappai R, Barnham KJ, Hutton CA. Synthetic dityrosine-linked β-amyloid dimers form stable, soluble, neurotoxic oligomers. Chem Sci 2013. [DOI: 10.1039/c3sc22295k] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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