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Effect of Aβ Oligomers on Neuronal APP Triggers a Vicious Cycle Leading to the Propagation of Synaptic Plasticity Alterations to Healthy Neurons. J Neurosci 2020; 40:5161-5176. [PMID: 32444385 DOI: 10.1523/jneurosci.2501-19.2020] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 03/04/2020] [Accepted: 04/03/2020] [Indexed: 01/04/2023] Open
Abstract
Alterations of excitatory synaptic function are the strongest correlate to the pathologic disturbance of cognitive ability observed in the early stages of Alzheimer's disease (AD). This pathologic feature is driven by amyloid-β oligomers (Aβos) and propagates from neuron to neuron. Here, we investigated the mechanism by which Aβos affect the function of synapses and how these alterations propagate to surrounding healthy neurons. We used complementary techniques ranging from electrophysiological recordings and molecular biology to confocal microscopy in primary cortical cultures, and from acute hippocampal and cortical slices from male wild-type and amyloid precursor protein (APP) knock-out (KO) mice to assess the effects of Aβos on glutamatergic transmission, synaptic plasticity, and dendritic spine structure. We showed that extracellular application of Aβos reduced glutamatergic synaptic transmission and long-term potentiation. These alterations were not observed in APP KO neurons, suggesting that APP expression is required. We demonstrated that Aβos/APP interaction increases the amyloidogenic processing of APP leading to intracellular accumulation of newly produced Aβos. Intracellular Aβos participate in synaptic dysfunctions as shown by pharmacological inhibition of APP processing or by intraneuronal infusion of an antibody raised against Aβos. Furthermore, we provide evidence that following APP processing, extracellular release of Aβos mediates the propagation of the synaptic pathology characterized by a decreased spine density of neighboring healthy neurons in an APP-dependent manner. Together, our data unveil a complementary role for Aβos in AD, while intracellular Aβos alter synaptic function, extracellular Aβos promote a vicious cycle that propagates synaptic pathology from diseased to healthy neurons.SIGNIFICANCE STATEMENT Here we provide the proof that a vicious cycle between extracellular and intracellular pools of Aβ oligomers (Aβos) is required for the spreading of Alzheimer's disease (AD) pathology. We showed that extracellular Aβos propagate excitatory synaptic alterations by promoting amyloid precursor protein (APP) processing. Our results also suggest that subsequent to APP cleavage two pools of Aβos are produced. One pool accumulates inside the cytosol, inducing the loss of synaptic plasticity potential. The other pool is released into the extracellular space and contributes to the propagation of the pathology from diseased to healthy neurons. Pharmacological strategies targeting the proteolytic cleavage of APP disrupt the relationship between extracellular and intracellular Aβ, providing a therapeutic approach for the disease.
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Afghah Z, Chen X, Geiger JD. Role of endolysosomes and inter-organellar signaling in brain disease. Neurobiol Dis 2020; 134:104670. [PMID: 31707116 PMCID: PMC7184921 DOI: 10.1016/j.nbd.2019.104670] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 10/14/2019] [Accepted: 11/05/2019] [Indexed: 12/29/2022] Open
Abstract
Endosomes and lysosomes (endolysosomes) are membrane bounded organelles that play a key role in cell survival and cell death. These acidic intracellular organelles are the principal sites for intracellular hydrolytic activity required for the maintenance of cellular homeostasis. Endolysosomes are involved in the degradation of plasma membrane components, extracellular macromolecules as well as intracellular macromolecules and cellular fragments. Understanding the physiological significance and pathological relevance of endolysosomes is now complicated by relatively recent findings of physical and functional interactions between endolysosomes with other intracellular organelles including endoplasmic reticulum, mitochondria, plasma membranes, and peroxisomes. Indeed, evidence clearly indicates that endolysosome dysfunction and inter-organellar signaling occurs in different neurodegenerative diseases including Alzheimer's disease (AD), HIV-1 associated neurocognitive disease (HAND), Parkinson's disease (PD) as well as various forms of brain cancer such as glioblastoma multiforme (GBM). These findings open new areas of cell biology research focusing on understanding the physiological actions and pathophysiological consequences of inter-organellar communication. Here, we will review findings of others and us that endolysosome de-acidification and dysfunction coupled with impaired inter-organellar signaling is involved in the pathogenesis of AD, HAND, PD, and GBM. A more comprehensive appreciation of cell biology and inter-organellar signaling could lead to the development of new drugs to prevent or cure these diseases.
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Affiliation(s)
- Zahra Afghah
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58201, United States of America
| | - Xuesong Chen
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58201, United States of America
| | - Jonathan D Geiger
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58201, United States of America.
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3
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Matrone C, Iannuzzi F, Annunziato L. The Y 682ENPTY 687 motif of APP: Progress and insights toward a targeted therapy for Alzheimer's disease patients. Ageing Res Rev 2019; 52:120-128. [PMID: 31039414 DOI: 10.1016/j.arr.2019.04.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Revised: 03/04/2019] [Accepted: 04/10/2019] [Indexed: 12/14/2022]
Abstract
Alzheimer's disease (AD) is a devastating neurodegenerative disorder for which no curative treatments, disease modifying strategies or effective symptomatic therapies exist. Current pharmacologic treatments for AD can only decelerate the progression of the disease for a short time, often at the cost of severe side effects. Therefore, there is an urgent need for biomarkers able to diagnose AD at its earliest stages, to conclusively track disease progression, and to accelerate the clinical development of innovative therapies. Scientific research and economic efforts for the development of pharmacotherapies have recently homed in on the hypothesis that neurotoxic β-amyloid (Aβ) peptides in their oligomeric or fibrillary forms are primarily responsible for the cognitive impairment and neuronal death seen in AD. As such, modern pharmacologic approaches are largely based on reducing production by inhibiting β and γ secretase cleavage of the amyloid precursor protein (APP) or on dissolving existing cerebral Aβ plaques or to favor Aβ clearance from the brain. The following short review aims to persuade the reader of the idea that APP plays a much larger role in AD pathogenesis. APP plays a greater role in AD pathogenesis than its role as the precursor for Aβ peptides: both the abnormal cleavage of APP leading to Aβ peptide accumulation and the disruption of APP physiological functions contribute to AD pathogenesis. We summarize our recent results on the role played by the C-terminal APP motif -the Y682ENPTY68 motif- in APP function and dysfunction, and we provide insights into targeting the Tyr682 residue of APP as putative novel strategy in AD.
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de Oliveira PG, Ramos MLS, Amaro AJ, Dias RA, Vieira SI. G i/o-Protein Coupled Receptors in the Aging Brain. Front Aging Neurosci 2019; 11:89. [PMID: 31105551 PMCID: PMC6492497 DOI: 10.3389/fnagi.2019.00089] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Accepted: 04/03/2019] [Indexed: 12/18/2022] Open
Abstract
Cells translate extracellular signals to regulate processes such as differentiation, metabolism and proliferation, via transmembranar receptors. G protein-coupled receptors (GPCRs) belong to the largest family of transmembrane receptors, with over 800 members in the human species. Given the variety of key physiological functions regulated by GPCRs, these are main targets of existing drugs. During normal aging, alterations in the expression and activity of GPCRs have been observed. The central nervous system (CNS) is particularly affected by these alterations, which results in decreased brain functions, impaired neuroregeneration, and increased vulnerability to neuropathologies, such as Alzheimer's and Parkinson diseases. GPCRs signal via heterotrimeric G proteins, such as Go, the most abundant heterotrimeric G protein in CNS. We here review age-induced effects of GPCR signaling via the Gi/o subfamily at the CNS. During the aging process, a reduction in protein density is observed for almost half of the Gi/o-coupled GPCRs, particularly in age-vulnerable regions such as the frontal cortex, hippocampus, substantia nigra and striatum. Gi/o levels also tend to decrease with aging, particularly in regions such as the frontal cortex. Alterations in the expression and activity of GPCRs and coupled G proteins result from altered proteostasis, peroxidation of membranar lipids and age-associated neuronal degeneration and death, and have impact on aging hallmarks and age-related neuropathologies. Further, due to oligomerization of GPCRs at the membrane and their cooperative signaling, down-regulation of a specific Gi/o-coupled GPCR may affect signaling and drug targeting of other types/subtypes of GPCRs with which it dimerizes. Gi/o-coupled GPCRs receptorsomes are thus the focus of more effective therapeutic drugs aiming to prevent or revert the decline in brain functions and increased risk of neuropathologies at advanced ages.
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Affiliation(s)
- Patrícia G de Oliveira
- Department of Medical Sciences, Institute of Biomedicine (iBiMED) and The Discovery CTR, Universidade de Aveiro, Aveiro, Portugal
| | - Marta L S Ramos
- Department of Medical Sciences, Institute of Biomedicine (iBiMED) and The Discovery CTR, Universidade de Aveiro, Aveiro, Portugal
| | - António J Amaro
- School of Health Sciences (ESSUA), Universidade de Aveiro, Aveiro, Portugal
| | - Roberto A Dias
- Department of Medical Sciences, Institute of Biomedicine (iBiMED) and The Discovery CTR, Universidade de Aveiro, Aveiro, Portugal
| | - Sandra I Vieira
- Department of Medical Sciences, Institute of Biomedicine (iBiMED) and The Discovery CTR, Universidade de Aveiro, Aveiro, Portugal
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5
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Bignante EA, Ponce NE, Heredia F, Musso J, Krawczyk MC, Millán J, Pigino GF, Inestrosa NC, Boccia MM, Lorenzo A. APP/Go protein Gβγ-complex signaling mediates Aβ degeneration and cognitive impairment in Alzheimer's disease models. Neurobiol Aging 2017; 64:44-57. [PMID: 29331876 DOI: 10.1016/j.neurobiolaging.2017.12.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 12/05/2017] [Accepted: 12/10/2017] [Indexed: 11/15/2022]
Abstract
Deposition of amyloid-β (Aβ), the proteolytic product of the amyloid precursor protein (APP), might cause neurodegeneration and cognitive decline in Alzheimer's disease (AD). However, the direct involvement of APP in the mechanism of Aβ-induced degeneration in AD remains on debate. Here, we analyzed the interaction of APP with heterotrimeric Go protein in primary hippocampal cultures and found that Aβ deposition dramatically enhanced APP-Go protein interaction in dystrophic neurites. APP overexpression rendered neurons vulnerable to Aβ toxicity by a mechanism that required Go-Gβγ complex signaling and p38-mitogen-activated protein kinase activation. Gallein, a selective pharmacological inhibitor of Gβγ complex, inhibited Aβ-induced dendritic and axonal dystrophy, abnormal tau phosphorylation, synaptic loss, and neuronal cell death in hippocampal neurons expressing endogenous protein levels. In the 3xTg-AD mice, intrahippocampal application of gallein reversed memory impairment associated with early Aβ pathology. Our data provide further evidence for the involvement of APP/Go protein in Aβ-induced degeneration and reveal that Gβγ complex is a signaling target potentially relevant for developing therapies for halting Aβ degeneration in AD.
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Affiliation(s)
- Elena Anahi Bignante
- Instituto de Investigación Médica "Mercedes y Martín Ferreyra", INIMEC-CONICET- Universidad Nacional de Córdoba, Córdoba, Argentina; Instituto Universitario de Ciencias Biomédicas de Córdoda (IUCBC), Argentina
| | - Nicolás Eric Ponce
- Instituto de Investigación Médica "Mercedes y Martín Ferreyra", INIMEC-CONICET- Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Florencia Heredia
- Instituto de Investigación Médica "Mercedes y Martín Ferreyra", INIMEC-CONICET- Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Juliana Musso
- Instituto de Investigación Médica "Mercedes y Martín Ferreyra", INIMEC-CONICET- Universidad Nacional de Córdoba, Córdoba, Argentina
| | - María C Krawczyk
- Laboratorio de Neurofarmacología de los Procesos de Memoria, Cátedra de Farmacología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Julieta Millán
- Laboratorio de Neurofarmacología de los Procesos de Memoria, Cátedra de Farmacología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Gustavo F Pigino
- Instituto de Investigación Médica "Mercedes y Martín Ferreyra", INIMEC-CONICET- Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Nibaldo C Inestrosa
- Centro de Envejecimiento y Regeneración (CARE), Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile; Centro de Excelencia en Biomedicina de Magallanes (CEBIMA), Punta Arenas, Chile
| | - Mariano M Boccia
- Laboratorio de Neurofarmacología de los Procesos de Memoria, Cátedra de Farmacología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Alfredo Lorenzo
- Instituto de Investigación Médica "Mercedes y Martín Ferreyra", INIMEC-CONICET- Universidad Nacional de Córdoba, Córdoba, Argentina; Departamento de Farmacología, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Argentina.
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Sosa LJ, Cáceres A, Dupraz S, Oksdath M, Quiroga S, Lorenzo A. The physiological role of the amyloid precursor protein as an adhesion molecule in the developing nervous system. J Neurochem 2017; 143:11-29. [PMID: 28677143 DOI: 10.1111/jnc.14122] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 06/28/2017] [Accepted: 06/29/2017] [Indexed: 12/12/2022]
Abstract
The amyloid precursor protein (APP) is a type I transmembrane glycoprotein better known for its participation in the physiopathology of Alzheimer disease as the source of the beta amyloid fragment. However, the physiological functions of the full length protein and its proteolytic fragments have remained elusive. APP was first described as a cell-surface receptor; nevertheless, increasing evidence highlighted APP as a cell adhesion molecule. In this review, we will focus on the current knowledge of the physiological role of APP as a cell adhesion molecule and its involvement in key events of neuronal development, such as migration, neurite outgrowth, growth cone pathfinding, and synaptogenesis. Finally, since APP is over-expressed in Down syndrome individuals because of the extra copy of chromosome 21, in the last section of the review, we discuss the potential contribution of APP to the neuronal and synaptic defects described in this genetic condition. Read the Editorial Highlight for this article on page 9. Cover Image for this issue: doi. 10.1111/jnc.13817.
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Affiliation(s)
- Lucas J Sosa
- Departamento de Química Biológica Ranwell Caputto, Facultad de Ciencias Químicas, CIQUIBIC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Alfredo Cáceres
- Laboratorio Neurobiología, Instituto Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina.,Instituto Universitario Ciencias Biomédicas Córdoba, Córdoba, Argentina
| | - Sebastián Dupraz
- Axonal Growth and Regeneration, German Center for Neurodegenarative Diseases, Bonn, Germany
| | - Mariana Oksdath
- Departamento de Química Biológica Ranwell Caputto, Facultad de Ciencias Químicas, CIQUIBIC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Santiago Quiroga
- Departamento de Química Biológica Ranwell Caputto, Facultad de Ciencias Químicas, CIQUIBIC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Alfredo Lorenzo
- Laboratorio de Neuropatología Experimental, Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina
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Ramaker JM, Copenhaver PF. Amyloid Precursor Protein family as unconventional Go-coupled receptors and the control of neuronal motility. NEUROGENESIS 2017; 4:e1288510. [PMID: 28321435 PMCID: PMC5345750 DOI: 10.1080/23262133.2017.1288510] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 01/21/2017] [Accepted: 01/25/2017] [Indexed: 01/06/2023]
Abstract
Cleavage of the Amyloid Precursor Protein (APP) generates amyloid peptides that accumulate in Alzheimer Disease (AD), but APP is also upregulated by developing and injured neurons, suggesting that it regulates neuronal motility. APP can also function as a G protein-coupled receptor that signals via the heterotrimeric G protein Gαo, but evidence for APP-Gαo signaling in vivo has been lacking. Using Manduca as a model system, we showed that insect APP (APPL) regulates neuronal migration in a Gαo-dependent manner. Recently, we also demonstrated that Manduca Contactin (expressed by glial cells) induces APPL-Gαo retraction responses in migratory neurons, consistent with evidence that mammalian Contactins also interact with APP family members. Preliminary studies using cultured hippocampal neurons suggest that APP-Gαo signaling can similarly regulate growth cone motility. Whether Contactins (or other APP ligands) induce this response within the developing nervous system, and how this pathway is disrupted in AD, remains to be explored.
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Affiliation(s)
- Jenna M Ramaker
- Department of Cell, Developmental and Cancer Biology L-215, Oregon Health & Sciences University , Portland, OR, USA
| | - Philip F Copenhaver
- Department of Cell, Developmental and Cancer Biology L-215, Oregon Health & Sciences University , Portland, OR, USA
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Copenhaver PF, Kögel D. Role of APP Interactions with Heterotrimeric G Proteins: Physiological Functions and Pathological Consequences. Front Mol Neurosci 2017; 10:3. [PMID: 28197070 PMCID: PMC5281615 DOI: 10.3389/fnmol.2017.00003] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Accepted: 01/05/2017] [Indexed: 12/27/2022] Open
Abstract
Following the discovery that the amyloid precursor protein (APP) is the source of β-amyloid peptides (Aβ) that accumulate in Alzheimer’s disease (AD), structural analyses suggested that the holoprotein resembles a transmembrane receptor. Initial studies using reconstituted membranes demonstrated that APP can directly interact with the heterotrimeric G protein Gαo (but not other G proteins) via an evolutionarily G protein-binding motif in its cytoplasmic domain. Subsequent investigations in cell culture showed that antibodies against the extracellular domain of APP could stimulate Gαo activity, presumably mimicking endogenous APP ligands. In addition, chronically activating wild type APP or overexpressing mutant APP isoforms linked with familial AD could provoke Go-dependent neurotoxic responses, while biochemical assays using human brain samples suggested that the endogenous APP-Go interactions are perturbed in AD patients. More recently, several G protein-dependent pathways have been implicated in the physiological roles of APP, coupled with evidence that APP interacts both physically and functionally with Gαo in a variety of contexts. Work in insect models has demonstrated that the APP ortholog APPL directly interacts with Gαo in motile neurons, whereby APPL-Gαo signaling regulates the response of migratory neurons to ligands encountered in the developing nervous system. Concurrent studies using cultured mammalian neurons and organotypic hippocampal slice preparations have shown that APP signaling transduces the neuroprotective effects of soluble sAPPα fragments via modulation of the PI3K/Akt pathway, providing a mechanism for integrating the stress and survival responses regulated by APP. Notably, this effect was also inhibited by pertussis toxin, indicating an essential role for Gαo/i proteins. Unexpectedly, C-terminal fragments (CTFs) derived from APP have also been found to interact with Gαs, whereby CTF-Gαs signaling can promote neurite outgrowth via adenylyl cyclase/PKA-dependent pathways. These reports offer the intriguing perspective that G protein switching might modulate APP-dependent responses in a context-dependent manner. In this review, we provide an up-to-date perspective on the model that APP plays a variety of roles as an atypical G protein-coupled receptor in both the developing and adult nervous system, and we discuss the hypothesis that disruption of these normal functions might contribute to the progressive neuropathologies that typify AD.
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Affiliation(s)
- Philip F Copenhaver
- Department of Cell, Developmental and Cancer Biology, Oregon Health & Sciences University, Portland OR, USA
| | - Donat Kögel
- Experimental Neurosurgery, Goethe University Frankfurt Frankfurt am Main, Germany
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Ramaker JM, Cargill RS, Swanson TL, Quirindongo H, Cassar M, Kretzschmar D, Copenhaver PF. Amyloid Precursor Proteins Are Dynamically Trafficked and Processed during Neuronal Development. Front Mol Neurosci 2016; 9:130. [PMID: 27932950 PMCID: PMC5122739 DOI: 10.3389/fnmol.2016.00130] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 11/10/2016] [Indexed: 01/10/2023] Open
Abstract
Proteolytic processing of the Amyloid Precursor Protein (APP) produces beta-amyloid (Aβ) peptide fragments that accumulate in Alzheimer's Disease (AD), but APP may also regulate multiple aspects of neuronal development, albeit via mechanisms that are not well understood. APP is a member of a family of transmembrane glycoproteins expressed by all higher organisms, including two mammalian orthologs (APLP1 and APLP2) that have complicated investigations into the specific activities of APP. By comparison, insects express only a single APP-related protein (APP-Like, or APPL) that contains the same protein interaction domains identified in APP. However, unlike its mammalian orthologs, APPL is only expressed by neurons, greatly simplifying an analysis of its functions in vivo. Like APP, APPL is processed by secretases to generate a similar array of extracellular and intracellular cleavage fragments, as well as an Aβ-like fragment that can induce neurotoxic responses in the brain. Exploiting the complementary advantages of two insect models (Drosophila melanogaster and Manduca sexta), we have investigated the regulation of APPL trafficking and processing with respect to different aspects of neuronal development. By comparing the behavior of endogenously expressed APPL with fluorescently tagged versions of APPL and APP, we have shown that some full-length protein is consistently trafficked into the most motile regions of developing neurons both in vitro and in vivo. Concurrently, much of the holoprotein is rapidly processed into N- and C-terminal fragments that undergo bi-directional transport within distinct vesicle populations. Unexpectedly, we also discovered that APPL can be transiently sequestered into an amphisome-like compartment in developing neurons, while manipulations targeting APPL cleavage altered their motile behavior in cultured embryos. These data suggest that multiple mechanisms restrict the bioavailability of the holoprotein to regulate APPL-dependent responses within the nervous system. Lastly, targeted expression of our double-tagged constructs (combined with time-lapse imaging) revealed that APP family proteins are subject to complex patterns of trafficking and processing that vary dramatically between different neuronal subtypes. In combination, our results provide a new perspective on how the regulation of APP family proteins can be modulated to accommodate a variety of cell type-specific responses within the embryonic and adult nervous system.
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Affiliation(s)
- Jenna M Ramaker
- Department of Cell, Developmental and Cancer Biology, Oregon Health and Science UniversityPortland, OR, USA; Neuroscience Graduate Program, Oregon Health and Science UniversityPortland, OR, USA
| | - Robert S Cargill
- Oregon Institute of Occupational Health Sciences, Oregon Health and Science University Portland, OR, USA
| | - Tracy L Swanson
- Department of Cell, Developmental and Cancer Biology, Oregon Health and Science University Portland, OR, USA
| | - Hanil Quirindongo
- Oregon Institute of Occupational Health Sciences, Oregon Health and Science University Portland, OR, USA
| | - Marlène Cassar
- Oregon Institute of Occupational Health Sciences, Oregon Health and Science University Portland, OR, USA
| | - Doris Kretzschmar
- Oregon Institute of Occupational Health Sciences, Oregon Health and Science University Portland, OR, USA
| | - Philip F Copenhaver
- Department of Cell, Developmental and Cancer Biology, Oregon Health and Science University Portland, OR, USA
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10
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APP Receptor? To Be or Not To Be. Trends Pharmacol Sci 2016; 37:390-411. [PMID: 26837733 DOI: 10.1016/j.tips.2016.01.005] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 01/07/2016] [Accepted: 01/11/2016] [Indexed: 11/22/2022]
Abstract
Amyloid precursor protein (APP) and its metabolites play a key role in Alzheimer's disease pathogenesis. The idea that APP may function as a receptor has gained momentum based on its structural similarities to type I transmembrane receptors and the identification of putative APP ligands. We review the recent experimental evidence in support of this notion and discuss how this concept is viewed in the field. Specifically, we focus on the structural and functional characteristics of APP as a cell surface receptor, and on its interaction with adaptors and signaling proteins. We also address the importance of APP function as a receptor in Alzheimer's disease etiology and discuss how this function might be potentially important for the development of novel therapeutic approaches.
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Fogel H, Frere S, Segev O, Bharill S, Shapira I, Gazit N, O'Malley T, Slomowitz E, Berdichevsky Y, Walsh DM, Isacoff EY, Hirsch JA, Slutsky I. APP homodimers transduce an amyloid-β-mediated increase in release probability at excitatory synapses. Cell Rep 2014; 7:1560-1576. [PMID: 24835997 DOI: 10.1016/j.celrep.2014.04.024] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Revised: 03/12/2014] [Accepted: 04/12/2014] [Indexed: 10/25/2022] Open
Abstract
Accumulation of amyloid-β peptides (Aβ), the proteolytic products of the amyloid precursor protein (APP), induces a variety of synaptic dysfunctions ranging from hyperactivity to depression that are thought to cause cognitive decline in Alzheimer's disease. While depression of synaptic transmission has been extensively studied, the mechanisms underlying synaptic hyperactivity remain unknown. Here, we show that Aβ40 monomers and dimers augment release probability through local fine-tuning of APP-APP interactions at excitatory hippocampal boutons. Aβ40 binds to the APP, increases the APP homodimer fraction at the plasma membrane, and promotes APP-APP interactions. The APP activation induces structural rearrangements in the APP/Gi/o-protein complex, boosting presynaptic calcium flux and vesicle release. The APP growth-factor-like domain (GFLD) mediates APP-APP conformational changes and presynaptic enhancement. Thus, the APP homodimer constitutes a presynaptic receptor that transduces signal from Aβ40 to glutamate release. Excessive APP activation may initiate a positive feedback loop, contributing to hippocampal hyperactivity in Alzheimer's disease.
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Affiliation(s)
- Hilla Fogel
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Samuel Frere
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Oshik Segev
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Shashank Bharill
- Department of Molecular and Cell Biology and Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA 94720, USA
| | - Ilana Shapira
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Neta Gazit
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, 69978 Tel Aviv, Israel; Sagol School of Neuroscience, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Tiernan O'Malley
- Laboratory for Neurodegenerative Research, School of Biomolecular and Biomedical Science, Conway Institute, University College Dublin, Dublin 4, Republic of Ireland; Laboratory for Neurodegenerative Research, Center for Neurologic Diseases, Brigham & Women's Hospital, Harvard Institutes of Medicine, Boston, MA 02115, USA
| | - Edden Slomowitz
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Yevgeny Berdichevsky
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Dominic M Walsh
- Laboratory for Neurodegenerative Research, Center for Neurologic Diseases, Brigham & Women's Hospital, Harvard Institutes of Medicine, Boston, MA 02115, USA
| | - Ehud Y Isacoff
- Department of Molecular and Cell Biology and Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA 94720, USA
| | - Joel A Hirsch
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Inna Slutsky
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, 69978 Tel Aviv, Israel; Sagol School of Neuroscience, Tel Aviv University, 69978 Tel Aviv, Israel.
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Weyer SW, Zagrebelsky M, Herrmann U, Hick M, Ganss L, Gobbert J, Gruber M, Altmann C, Korte M, Deller T, Müller UC. Comparative analysis of single and combined APP/APLP knockouts reveals reduced spine density in APP-KO mice that is prevented by APPsα expression. Acta Neuropathol Commun 2014; 2:36. [PMID: 24684730 PMCID: PMC4023627 DOI: 10.1186/2051-5960-2-36] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Accepted: 03/07/2014] [Indexed: 11/21/2022] Open
Abstract
Synaptic dysfunction and synapse loss are key features of Alzheimer's pathogenesis. Previously, we showed an essential function of APP and APLP2 for synaptic plasticity, learning and memory. Here, we used organotypic hippocampal cultures to investigate the specific role(s) of APP family members and their fragments for dendritic complexity and spine formation of principal neurons within the hippocampus. Whereas CA1 neurons from APLP1-KO or APLP2-KO mice showed normal neuronal morphology and spine density, APP-KO mice revealed a highly reduced dendritic complexity in mid-apical dendrites. Despite unaltered morphology of APLP2-KO neurons, combined APP/APLP2-DKO mutants showed an additional branching defect in proximal apical dendrites, indicating redundancy and a combined function of APP and APLP2 for dendritic architecture. Remarkably, APP-KO neurons showed a pronounced decrease in spine density and reductions in the number of mushroom spines. No further decrease in spine density, however, was detectable in APP/APLP2-DKO mice. Mechanistically, using APPsα-KI mice lacking transmembrane APP and expressing solely the secreted APPsα fragment we demonstrate that APPsα expression alone is sufficient to prevent the defects in spine density observed in APP-KO mice. Collectively, these studies reveal a combined role of APP and APLP2 for dendritic architecture and a unique function of secreted APPs for spine density.
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Affiliation(s)
- Sascha W Weyer
- Department of Bioinformatics and Functional Genomics, Ruprecht-Karls University Heidelberg, Institute of Pharmacy and Molecular Biotechnology, Im Neuenheimer Feld 364, Heidelberg D-69120, Germany
| | - Marta Zagrebelsky
- TU Braunschweig, Zoological Institute, Cellular Neurobiology, Spielmannstr. 7, Braunschweig D-38106, Germany
| | - Ulrike Herrmann
- TU Braunschweig, Zoological Institute, Cellular Neurobiology, Spielmannstr. 7, Braunschweig D-38106, Germany
| | - Meike Hick
- Department of Bioinformatics and Functional Genomics, Ruprecht-Karls University Heidelberg, Institute of Pharmacy and Molecular Biotechnology, Im Neuenheimer Feld 364, Heidelberg D-69120, Germany
| | - Lennard Ganss
- Department of Bioinformatics and Functional Genomics, Ruprecht-Karls University Heidelberg, Institute of Pharmacy and Molecular Biotechnology, Im Neuenheimer Feld 364, Heidelberg D-69120, Germany
- Present address: Department of Applied Tumor Biology, Ruprecht-Karls University Heidelberg, Institute of Pathology, University of Heidelberg, Heidelberg D-69120, Germany
| | - Julia Gobbert
- Department of Bioinformatics and Functional Genomics, Ruprecht-Karls University Heidelberg, Institute of Pharmacy and Molecular Biotechnology, Im Neuenheimer Feld 364, Heidelberg D-69120, Germany
| | - Morna Gruber
- Goethe University Frankfurt, Institute of Clinical Neuroanatomy, Neuroscience Center, Theodor-Stern-Kai 7, Frankfurt am Main D-60596, Germany
| | - Christine Altmann
- Goethe University Frankfurt, Institute of Clinical Neuroanatomy, Neuroscience Center, Theodor-Stern-Kai 7, Frankfurt am Main D-60596, Germany
| | - Martin Korte
- TU Braunschweig, Zoological Institute, Cellular Neurobiology, Spielmannstr. 7, Braunschweig D-38106, Germany
| | - Thomas Deller
- Goethe University Frankfurt, Institute of Clinical Neuroanatomy, Neuroscience Center, Theodor-Stern-Kai 7, Frankfurt am Main D-60596, Germany
| | - Ulrike C Müller
- Department of Bioinformatics and Functional Genomics, Ruprecht-Karls University Heidelberg, Institute of Pharmacy and Molecular Biotechnology, Im Neuenheimer Feld 364, Heidelberg D-69120, Germany
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13
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Sheng L, Leshchyns'ka I, Sytnyk V. Cell adhesion and intracellular calcium signaling in neurons. Cell Commun Signal 2013; 11:94. [PMID: 24330678 PMCID: PMC3878801 DOI: 10.1186/1478-811x-11-94] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Accepted: 12/05/2013] [Indexed: 01/10/2023] Open
Abstract
Cell adhesion molecules (CAMs) play indispensable roles in the developing and mature brain by regulating neuronal migration and differentiation, neurite outgrowth, axonal fasciculation, synapse formation and synaptic plasticity. CAM-mediated changes in neuronal behavior depend on a number of intracellular signaling cascades including changes in various second messengers, among which CAM-dependent changes in intracellular Ca2+ levels play a prominent role. Ca2+ is an essential secondary intracellular signaling molecule that regulates fundamental cellular functions in various cell types, including neurons. We present a systematic review of the studies reporting changes in intracellular Ca2+ levels in response to activation of the immunoglobulin superfamily CAMs, cadherins and integrins in neurons. We also analyze current experimental evidence on the Ca2+ sources and channels involved in intracellular Ca2+ increases mediated by CAMs of these families, and systematically review the role of the voltage-dependent Ca2+ channels (VDCCs) in neurite outgrowth induced by activation of these CAMs. Molecular mechanisms linking CAMs to VDCCs and intracellular Ca2+ stores in neurons are discussed.
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Affiliation(s)
| | | | - Vladimir Sytnyk
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, New South Wales 2052, Australia.
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14
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Amyloid precursor proteins interact with the heterotrimeric G protein Go in the control of neuronal migration. J Neurosci 2013; 33:10165-81. [PMID: 23761911 DOI: 10.1523/jneurosci.1146-13.2013] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Amyloid precursor protein (APP) belongs to a family of evolutionarily conserved transmembrane glycoproteins that has been proposed to regulate multiple aspects of cell motility in the nervous system. Although APP is best known as the source of β-amyloid fragments (Aβ) that accumulate in Alzheimer's disease, perturbations affecting normal APP signaling events may also contribute to disease progression. Previous in vitro studies showed that interactions between APP and the heterotrimeric G protein Goα-regulated Goα activity and Go-dependent apoptotic responses, independent of Aβ. However, evidence for authentic APP-Go interactions within the healthy nervous system has been lacking. To address this issue, we have used a combination of in vitro and in vivo strategies to show that endogenously expressed APP family proteins colocalize with Goα in both insect and mammalian nervous systems, including human brain. Using biochemical, pharmacological, and Bimolecular Fluorescence Complementation assays, we have shown that insect APP (APPL) directly interacts with Goα in cell culture and at synaptic terminals within the insect brain, and that this interaction is regulated by Goα activity. We have also adapted a well characterized assay of neuronal migration in the hawkmoth Manduca to show that perturbations affecting APPL and Goα signaling induce the same unique pattern of ectopic, inappropriate growth and migration, analogous to defective migration patterns seen in mice lacking all APP family proteins. These results support the model that APP and its orthologs regulate conserved aspects of neuronal migration and outgrowth in the nervous system by functioning as unconventional Goα-coupled receptors.
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15
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Heese K. G proteins, p60TRP, and neurodegenerative diseases. Mol Neurobiol 2013; 47:1103-11. [PMID: 23345134 DOI: 10.1007/s12035-013-8410-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2012] [Accepted: 01/13/2013] [Indexed: 12/20/2022]
Abstract
Alzheimer's disease (AD) is a complex brain disorder of the limbic system and association cortices. The disease is characterized by the production and deposition of the amyloid β-peptide (Aβ) in the brain, and the neuropathological mechanisms involved must be deciphered to gain further insights into the fundamental aspects of the protein biology responsible for the development and progression of this disease. Aβ is generated by the intramembranous cleavage of the β-amyloid precursor protein, which is mediated by the proteases β- and γ-secretase. Accumulating evidence suggests the importance of the coupling of this cleavage mechanism to G protein signaling. Heterotrimeric G proteins play pivotal roles as molecular switches in signal transduction pathways mediated by G protein-coupled receptors (GPCRs). Extracellular stimuli activate these receptors, which in turn catalyze guanosine triphosphate-guanosine diphosphate exchange on the G protein α-subunit. The activation-deactivation cycles of G proteins underlie their crucial functions as molecular switches for a vast array of biological responses. The novel transcription regulator protein p60 transcription regulator protein and its related GPCR signaling pathways have recently been described as potential targets for the development of alternative strategies for inhibiting the early signaling mechanisms involved in neurodegenerative diseases such as AD.
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Affiliation(s)
- Klaus Heese
- Department of Biomedical Engineering, College of Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 133-791, Republic of Korea.
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16
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Hunter S, Brayne C. Relationships between the amyloid precursor protein and its various proteolytic fragments and neuronal systems. Alzheimers Res Ther 2012; 4:10. [PMID: 22498202 PMCID: PMC3583130 DOI: 10.1186/alzrt108] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Alzheimer's disease (AD) is a progressive neurodegenerative disease and in its familial form is associated with mutations in the amyloid precursor protein (APP) and the presenilins (PSs). Much data regarding the interactions of APP, its proteolytic fragments and PS have been generated, expanding our understanding of the roles of these proteins in mechanisms underlying cognitive function and revealing many complex relationships with wide ranging cellular systems. In this review, we examine the multiple interactions of APP and its proteolytic fragments with other neuronal systems in terms of feedback loops and use these relationships to build a map. We highlight the complexity involved in the APP proteolytic system and discuss alternative perspectives on the roles of APP and its proteolytic fragments in dynamic processes associated with disease progression in AD. We highlight areas where data are missing and suggest potential confounding factors. We suggest that a systems biology approach enhances representations of the data and may be more useful in modelling both normal cognition and disease processes.
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Affiliation(s)
- Sally Hunter
- Institute of Public Health, University of Cambridge, Forvie site, Robinson Way, Cambridge CB2 0SR, UK
| | - Carol Brayne
- Institute of Public Health, University of Cambridge, Forvie site, Robinson Way, Cambridge CB2 0SR, UK
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17
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Mishra M, Heese K. P60TRP interferes with the GPCR/secretase pathway to mediate neuronal survival and synaptogenesis. J Cell Mol Med 2012; 15:2462-77. [PMID: 21199326 PMCID: PMC3822957 DOI: 10.1111/j.1582-4934.2010.01248.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
In the present study, we show that overexpression of the G-protein-coupled receptor (GPCR)-associated sorting protein p60TRP (transcription regulator protein) in neural stem cells (NSCs) and in a transgenic mouse model modulates the phosphorylation and proteolytic processing of amyloid precursor protein (App), N-cadherin (Cdh2), presenilin (Psen) and τ protein (Mapt). Our results suggest that p60TRP is an inhibitor of Bace1 (β-site App cleaving enzyme) and Psen. We performed several apoptosis assays [Annexin-V, TdT-mediated dUTP Nick-End Labeling (TUNEL), caspase-3/7] using NSCs and PC12 cells (overexpressing p60TRP and knockdown of p60TRP) to substantiate the neuroprotective role of p60TRP. Functional analyses, both in vitro and in vivo, revealed that p60TRP promotes neurosynaptogenesis. Characterization of the cognitive function of p60TRP transgenic mice using the radial arm water maze test demonstrated that p60TRP improved memory and learning abilities. The improved cognitive functions could be attributed to increased synaptic connections and plasticity, which was confirmed by the modulation of the γ-aminobutyric acid receptor system and the elevated expression of microtubule-associated protein 2, synaptophysin and Slc17a7 (vesicle glutamate transporter, Vglut1), as well as by the inhibition of Cdh2 cleavage. In conclusion, interference with the p60TRP/ GPCR/secretase signalling pathway might be a new therapeutic target for the treatment of Alzheimer's disease (AD).
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Affiliation(s)
- Manisha Mishra
- Department of Molecular and Cell Biology, School of Biological Sciences, College of Science, Nanyang Technological University, Singapore
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18
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Novel GαS-protein signaling associated with membrane-tethered amyloid precursor protein intracellular domain. J Neurosci 2012; 32:1714-29. [PMID: 22302812 DOI: 10.1523/jneurosci.5433-11.2012] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Numerous physiological functions, including a role as a cell surface receptor, have been ascribed to Alzheimer's disease-associated amyloid precursor protein (APP). However, detailed analysis of intracellular signaling mediated by APP in neurons has been lacking. Here, we characterized intrinsic signaling associated with membrane-bound APP C-terminal fragments, which are generated following APP ectodomain release by α- or β-secretase cleavage. We found that accumulation of APP C-terminal fragments or expression of membrane-tethered APP intracellular domain results in adenylate cyclase-dependent activation of PKA (protein kinase A) and inhibition of GSK3β signaling cascades, and enhancement of axodendritic arborization in rat immortalized hippocampal neurons, mouse primary cortical neurons, and mouse neuroblastoma. We discovered an interaction between BBXXB motif of APP intracellular domain and the heterotrimeric G-protein subunit Gα(S), and demonstrate that Gα(S) coupling to adenylate cyclase mediates membrane-tethered APP intracellular domain-induced neurite outgrowth. Our study provides clear evidence that APP intracellular domain can have a nontranscriptional role in regulating neurite outgrowth through its membrane association. The novel functional coupling of membrane-bound APP C-terminal fragments with Gα(S) signaling identified in this study could impact several brain functions such as synaptic plasticity and memory formation.
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19
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Desbène C, Malaplate-Armand C, Youssef I, Garcia P, Stenger C, Sauvée M, Fischer N, Rimet D, Koziel V, Escanyé MC, Oster T, Kriem B, Yen FT, Pillot T, Olivier JL. Critical role of cPLA2 in Aβ oligomer-induced neurodegeneration and memory deficit. Neurobiol Aging 2011; 33:1123.e17-29. [PMID: 22188721 DOI: 10.1016/j.neurobiolaging.2011.11.008] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2010] [Revised: 11/03/2011] [Accepted: 11/04/2011] [Indexed: 12/23/2022]
Abstract
Soluble beta-amyloid (Aβ) oligomers are considered to putatively play a critical role in the early synapse loss and cognitive impairment observed in Alzheimer's disease. We previously demonstrated that Aβ oligomers activate cytosolic phospholipase A(2) (cPLA(2)), which specifically releases arachidonic acid from membrane phospholipids. We here observed that cPLA(2) gene inactivation prevented the alterations of cognitive abilities and the reduction of hippocampal synaptic markers levels noticed upon a single intracerebroventricular injection of Aβ oligomers in wild type mice. We further demonstrated that the Aβ oligomer-induced sphingomyelinase activation was suppressed and that phosphorylation of Akt/protein kinase B (PKB) was preserved in neuronal cells isolated from cPLA(2)(-/-) mice. Interestingly, expression of the Aβ precursor protein (APP) was reduced in hippocampus homogenates and neuronal cells from cPLA(2)(-/-) mice, but the relationship with the resistance of these mice to the Aβ oligomer toxicity requires further investigation. These results therefore show that cPLA(2) plays a key role in the Aβ oligomer-associated neurodegeneration, and as such represents a potential therapeutic target for the treatment of Alzheimer's disease.
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Affiliation(s)
- Cédric Desbène
- Lipidomix (EA 4422), INPL-ENSAIA, Université de Lorraine, Vandœuvre-lès-Nancy, France
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20
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Abstract
Intracellular Ca(2+) signaling is fundamental to neuronal physiology and viability. Because of its ubiquitous roles, disruptions in Ca(2+) homeostasis are implicated in diverse disease processes and have become a major focus of study in multifactorial neurodegenerative diseases such as Alzheimer disease (AD). A hallmark of AD is the excessive production of beta-amyloid (Abeta) and its massive accumulation in amyloid plaques. In this minireview, we highlight the pathogenic interactions between altered cellular Ca(2+) signaling and Abeta in its different aggregation states and how these elements coalesce to alter the course of the neurodegenerative disease. Ca(2+) and Abeta intersect at several functional levels and temporal stages of AD, thereby altering neurotransmitter receptor properties, disrupting membrane integrity, and initiating apoptotic signaling cascades. Notably, there are reciprocal interactions between Ca(2+) pathways and amyloid pathology; altered Ca(2+) signaling accelerates Abeta formation, whereas Abeta peptides, particularly in soluble oligomeric forms, induce Ca(2+) disruptions. A degenerative feed-forward cycle of toxic Abeta generation and Ca(2+) perturbations results, which in turn can spin off to accelerate more global neuropathological cascades, ultimately leading to synaptic breakdown, cell death, and devastating memory loss. Although no cause or cure is currently known, targeting Ca(2+) dyshomeostasis as an underlying and integral component of AD pathology may result in novel and effective treatments for AD.
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Affiliation(s)
- Angelo Demuro
- From the Departments of
Neurobiology and Behavior and
| | - Ian Parker
- From the Departments of
Neurobiology and Behavior and
- Physiology and Biophysics, University of California, Irvine, California 92697 and
| | - Grace E. Stutzmann
- the
Department of Neuroscience, The Chicago Medical School, Rosalind Franklin University, North Chicago, Illinois 60064
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21
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Diarra A, Geetha T, Potter P, Babu JR. Signaling of the neurotrophin receptor p75 in relation to Alzheimer's disease. Biochem Biophys Res Commun 2009; 390:352-6. [PMID: 19818333 DOI: 10.1016/j.bbrc.2009.09.116] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Accepted: 09/24/2009] [Indexed: 01/29/2023]
Abstract
The cellular mechanism of neuronal apoptosis in Alzheimer's disease (AD) is poorly understood. Many hypotheses have been put fourth to explain the underlying reason for neuro-degeneration in AD. Here, it is demonstrated that all neurotrophins that activated p75, without co-activation of the relevant Trk co-receptor, mediated apoptosis in hippocampal neurons. Thus, proneurotrophins and amyloid beta peptides (Abeta) can induce p75-mediated apoptosis in hippocampal neurons since they do not bind or activate Trk receptors. Based on the combined effects of aging, proneurotrophins, neurotrophins, and Abeta, a novel model of pathogenesis in AD is proposed. This mini-review explores the ligand and cell type based signaling pathways of the neurotrophin receptor p75 relating to Alzheimer's disease.
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Affiliation(s)
- Adama Diarra
- Department of Biochemistry, Arizona College of Osteopathic Medicine, Midwestern University, Glendale, AZ 85308, USA
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