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Sappakhaw K, Jantarug K, Slavoff SA, Israsena N, Uttamapinant C. A Genetic Code Expansion-Derived Molecular Beacon for the Detection of Intracellular Amyloid-β Peptide Generation. ANGEWANDTE CHEMIE (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2021; 133:3980-3985. [PMID: 38504667 PMCID: PMC10946459 DOI: 10.1002/ange.202010703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 09/19/2020] [Indexed: 11/09/2022]
Abstract
Polypeptides generated from proteolytic processing of protein precursors, or proteolytic proteoforms, play an important role in diverse biological functions and diseases. However, their often-small size and intricate post-translational biogenesis preclude the use of simple genetic tagging in their cellular studies. Herein, we develop a labeling strategy for this class of proteoforms, based on residue-specific genetic code expansion labeling with a molecular beacon design. We demonstrate the utility of such a design by creating a molecular beacon reporter to detect amyloid-β peptides, known to be involved in the pathogenesis of Alzheimer's disease, as they are produced from amyloid precursor protein (APP) along the endocytic pathway of living cells.
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Affiliation(s)
- Khomkrit Sappakhaw
- School of Biomolecular Science and Engineering Vidyasirimedhi Institute of Science and Technology (VISTEC) Rayong 21210 Thailand
| | - Krittapas Jantarug
- School of Biomolecular Science and Engineering Vidyasirimedhi Institute of Science and Technology (VISTEC) Rayong 21210 Thailand
| | - Sarah A Slavoff
- Department of Chemistry Yale University New Haven CT 06520 USA
| | - Nipan Israsena
- Stem Cell and Cell Therapy Research Unit and Department of Pharmacology Faculty of Medicine Chulalongkorn University Bangkok 10330 Thailand
| | - Chayasith Uttamapinant
- School of Biomolecular Science and Engineering Vidyasirimedhi Institute of Science and Technology (VISTEC) Rayong 21210 Thailand
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Sappakhaw K, Jantarug K, Slavoff SA, Israsena N, Uttamapinant C. A Genetic Code Expansion-Derived Molecular Beacon for the Detection of Intracellular Amyloid-β Peptide Generation. Angew Chem Int Ed Engl 2021; 60:3934-3939. [PMID: 33063327 PMCID: PMC7898502 DOI: 10.1002/anie.202010703] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 09/19/2020] [Indexed: 12/01/2022]
Abstract
Polypeptides generated from proteolytic processing of protein precursors, or proteolytic proteoforms, play an important role in diverse biological functions and diseases. However, their often-small size and intricate post-translational biogenesis preclude the use of simple genetic tagging in their cellular studies. Herein, we develop a labeling strategy for this class of proteoforms, based on residue-specific genetic code expansion labeling with a molecular beacon design. We demonstrate the utility of such a design by creating a molecular beacon reporter to detect amyloid-β peptides, known to be involved in the pathogenesis of Alzheimer's disease, as they are produced from amyloid precursor protein (APP) along the endocytic pathway of living cells.
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Affiliation(s)
- Khomkrit Sappakhaw
- School of Biomolecular Science and EngineeringVidyasirimedhi Institute of Science and Technology (VISTEC)Rayong21210Thailand
| | - Krittapas Jantarug
- School of Biomolecular Science and EngineeringVidyasirimedhi Institute of Science and Technology (VISTEC)Rayong21210Thailand
| | | | - Nipan Israsena
- Stem Cell and Cell Therapy Research Unit and Department of PharmacologyFaculty of MedicineChulalongkorn UniversityBangkok10330Thailand
| | - Chayasith Uttamapinant
- School of Biomolecular Science and EngineeringVidyasirimedhi Institute of Science and Technology (VISTEC)Rayong21210Thailand
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Fabiani C, Antollini SS. Alzheimer's Disease as a Membrane Disorder: Spatial Cross-Talk Among Beta-Amyloid Peptides, Nicotinic Acetylcholine Receptors and Lipid Rafts. Front Cell Neurosci 2019; 13:309. [PMID: 31379503 PMCID: PMC6657435 DOI: 10.3389/fncel.2019.00309] [Citation(s) in RCA: 90] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 06/25/2019] [Indexed: 12/17/2022] Open
Abstract
Biological membranes show lateral and transverse asymmetric lipid distribution. Cholesterol (Chol) localizes in both hemilayers, but in the external one it is mostly condensed in lipid-ordered microdomains (raft domains), together with saturated phosphatidyl lipids and sphingolipids (including sphingomyelin and glycosphingolipids). Membrane asymmetries induce special membrane biophysical properties and behave as signals for several physiological and/or pathological processes. Alzheimer’s disease (AD) is associated with a perturbation in different membrane properties. Amyloid-β (Aβ) plaques and neurofibrillary tangles of tau protein together with neuroinflammation and neurodegeneration are the most characteristic cellular changes observed in this disease. The extracellular presence of Aβ peptides forming senile plaques, together with soluble oligomeric species of Aβ, are considered the major cause of the synaptic dysfunction of AD. The association between Aβ peptide and membrane lipids has been extensively studied. It has been postulated that Chol content and Chol distribution condition Aβ production and posterior accumulation in membranes and, hence, cell dysfunction. Several lines of evidence suggest that Aβ partitions in the cell membrane accumulate mostly in raft domains, the site where the cleavage of the precursor AβPP by β- and γ- secretase is also thought to occur. The main consequence of the pathogenesis of AD is the disruption of the cholinergic pathways in the cerebral cortex and in the basal forebrain. In parallel, the nicotinic acetylcholine receptor has been extensively linked to membrane properties. Since its transmembrane domain exhibits extensive contacts with the surrounding lipids, the acetylcholine receptor function is conditioned by its lipid microenvironment. The nicotinic acetylcholine receptor is present in high-density clusters in the cell membrane where it localizes mainly in lipid-ordered domains. Perturbations of sphingomyelin or cholesterol composition alter acetylcholine receptor location. Therefore, Aβ processing, Aβ partitioning, and acetylcholine receptor location and function can be manipulated by changes in membrane lipid biophysics. Understanding these mechanisms should provide insights into new therapeutic strategies for prevention and/or treatment of AD. Here, we discuss the implications of lipid-protein interactions at the cell membrane level in AD.
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Affiliation(s)
- Camila Fabiani
- Instituto de Investigaciones Bioquímicas de Bahía Blanca CONICET-UNS, Bahía Blanca, Argentina.,Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, Bahía Blanca, Argentina
| | - Silvia S Antollini
- Instituto de Investigaciones Bioquímicas de Bahía Blanca CONICET-UNS, Bahía Blanca, Argentina.,Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, Bahía Blanca, Argentina
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Ghosh AK, Osswald HL. BACE1 (β-secretase) inhibitors for the treatment of Alzheimer's disease. Chem Soc Rev 2015; 43:6765-813. [PMID: 24691405 DOI: 10.1039/c3cs60460h] [Citation(s) in RCA: 233] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
BACE1 (β-secretase, memapsin 2, Asp2) has emerged as a promising target for the treatment of Alzheimer's disease. BACE1 is an aspartic protease which functions in the first step of the pathway leading to the production and deposition of amyloid-β peptide (Aβ). Its gene deletion showed only mild phenotypes. BACE1 inhibition has direct implications in the Alzheimer's disease pathology without largely affecting viability. However, inhibiting BACE1 selectively in vivo has presented many challenges to medicinal chemists. Since its identification in 2000, inhibitors covering many different structural classes have been designed and developed. These inhibitors can be largely classified as either peptidomimetic or non-peptidic inhibitors. Progress in these fields resulted in inhibitors that contain many targeted drug-like characteristics. In this review, we describe structure-based design strategies and evolution of a wide range of BACE1 inhibitors including compounds that have been shown to reduce brain Aβ, rescue the cognitive decline in transgenic AD mice and inhibitor drug candidates that are currently in clinical trials.
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Affiliation(s)
- Arun K Ghosh
- Department of Chemistry and Department of Medicinal Chemistry, Purdue University, West Lafayette, IN 47907, USA
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Soldano A, Hassan BA. Beyond pathology: APP, brain development and Alzheimer's disease. Curr Opin Neurobiol 2014; 27:61-7. [PMID: 24632309 DOI: 10.1016/j.conb.2014.02.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 01/15/2014] [Accepted: 02/06/2014] [Indexed: 12/20/2022]
Abstract
Alzheimer's disease (AD) is the most common form of dementia among the elderly. Research in the AD field has been mostly focused on the biology of the Aβ peptide but increasing evidence is shifting attention toward the physiological role of APP as key to understanding AD pathology. It is becoming apparent that APP plays a central role in the mechanisms that guarantee the accuracy and the robustness of brain wiring. In the present review we explore APP functions with focus on some of the underlying molecular mechanisms.
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Affiliation(s)
- Alessia Soldano
- VIB Center for the Biology of Disease, VIB, 3000 Leuven, Belgium; Center for Human Genetics, University of Leuven School of Medicine, 3000 Leuven, Belgium
| | - Bassem A Hassan
- VIB Center for the Biology of Disease, VIB, 3000 Leuven, Belgium; Center for Human Genetics, University of Leuven School of Medicine, 3000 Leuven, Belgium.
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Abstract
The Alzheimer's disease (AD)-associated amyloid-β protein precursor (AβPP) is cleaved by α-, β-, and presenilin (PS)/γ-secretases through sequential regulated proteolysis. These proteolytic events control the generation of the pathogenic amyloid-β (Aβ) peptide, which excessively accumulates in the brains of individuals afflicted by AD. A growing number of additional proteins cleaved by PS/γ-secretase continue to be discovered. Similarly to AβPP, most of these proteins are type-I transmembrane proteins involved in vital signaling functions regulating cell fate, adhesion, migration, neurite outgrowth, or synaptogenesis. All the identified proteins share common structural features, which are typical for their proteolysis. The consequences of the PS/γ-secretase-mediated cleavage on the function of many of these proteins are largely unknown. Here, we review the current literature on the proteolytic processing mediated by the versatile PS/γ-secretase complex. We begin by discussing the steps of AβPP processing and PS/γ-secretase complex composition and localization, which give clues to how and where the processing of other PS/γ-secretase substrates may take place. Then we summarize the typical features of PS/γ-secretase-mediated protein processing. Finally, we recapitulate the current knowledge on the possible physiological function of PS/γ-secretase-mediated cleavage of specific substrate proteins.
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Affiliation(s)
- Annakaisa Haapasalo
- Institute of Clinical Medicine-Neurology, University of Eastern Finland, Kuopio, Finland.
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Bateman DA, Chakrabartty A. Cell surface binding and internalization of aβ modulated by degree of aggregation. Int J Alzheimers Dis 2011; 2011:962352. [PMID: 21331340 PMCID: PMC3038693 DOI: 10.4061/2011/962352] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Revised: 11/04/2010] [Accepted: 12/14/2010] [Indexed: 11/25/2022] Open
Abstract
The amyloid peptides, Aβ40 and Aβ42, are generated through endoproteolytic cleavage of the amyloid precursor protein. Here we have developed a model to investigate the interaction of living cells with various forms of aggregated Aβ40/42. After incubation at endosomal pH 6, we observed a variety of Aβ conformations after 3 (Aβ3), 24 (Aβ24), and 90 hours (Aβ90). Both Aβ4224 and Aβ4024 were observed to rapidly bind and internalize into differentiated PC12 cells, leading to accumulation in the lysosome. In contrast, Aβ40/4290 were both found to only weakly associate with cells, but were observed as the most aggregated using dynamic light scattering and thioflavin-T. Internalization of Aβ40/4224 was inhibited with treatment of monodansylcadaverine, an endocytosis inhibitor. These studies indicate that the ability of Aβ40/42 to bind and internalize into living cells increases with degree of aggregation until it reaches a maximum beyond which its ability to interact with cells diminishes drastically.
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Affiliation(s)
- David A Bateman
- Laboratory of Biochemistry and Genetics, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0830, USA
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von Arnim CA, Einem BV, Weber P, Wagner M, Schwanzar D, Spoelgen R, Strauss WL, Schneckenburger H. Impact of cholesterol level upon APP and BACE proximity and APP cleavage. Biochem Biophys Res Commun 2008; 370:207-12. [DOI: 10.1016/j.bbrc.2008.03.047] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2008] [Accepted: 03/06/2008] [Indexed: 11/26/2022]
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Rajendran L, Knobloch M, Geiger KD, Dienel S, Nitsch R, Simons K, Konietzko U. Increased Aβ Production Leads to Intracellular Accumulation of Aβ in Flotillin-1-Positive Endosomes. NEURODEGENER DIS 2007; 4:164-70. [PMID: 17596711 DOI: 10.1159/000101841] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Extracellular accumulation of Abeta in beta-amyloid plaques is thought to be associated with the neurodegeneration observed in Alzheimer's disease (AD) patients, although a lack of correlation with cognitive decline raised doubts on this hypothesis. In different transgenic mouse models Abeta accumulates inside the cells and mice develop behavioral deficits well before visible extracellular beta-amyloid accumulation. Here we show that intracellular Abeta accumulates in flotillin-1 positive endocytic vesicles. We also demonstrate that flotillin-1 is not only associated with intracellular Abeta in transgenic mice but also with extracellular beta-amyloid plaques in AD patient brain sections.
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Affiliation(s)
- Lawrence Rajendran
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
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Requirement of aggregation propensity of Alzheimer amyloid peptides for neuronal cell surface binding. BMC Neurosci 2007; 8:29. [PMID: 17475015 PMCID: PMC1871596 DOI: 10.1186/1471-2202-8-29] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2006] [Accepted: 05/02/2007] [Indexed: 02/03/2023] Open
Abstract
Background Aggregation of the amyloid peptides, Aβ40 and Aβ42, is known to be involved in the pathology of Alzheimer's disease (AD). Here we investigate the relationship between peptide aggregation and cell surface binding of three forms of Aβ (Aβ40, Aβ42, and an Aβ mutant). Results Using confocal microscopy and flow cytometry with fluorescently labelled Aβ, we demonstrate a correlation between the aggregation propensity of the Alzheimer amyloid peptides and their neuronal cell surface association. We find that the highly aggregation prone Aβ42 associates with the surface of neuronal cells within one hour, while the less aggregation prone Aβ40 associates over 24 hours. We show that a double mutation in Aβ42 that reduces its aggregation propensity also reduces its association with the cell surface. Furthermore, we find that a cell line that is resistant to Aβ cytotoxicity, the non-neuronal human lymphoma cell line U937, does not bind either Aβ40 or Aβ42. Conclusion Taken together, our findings reveal that amyloid peptide aggregation propensity is an essential determinant of neuronal cell surface association. We anticipate that our approach, involving Aβ imaging in live cells, will be highly useful for evaluating the efficacy of therapeutic drugs that prevent toxic Aβ association with neuronal cells.
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Dominguez DI, Hartmann D, De Strooper B. BACE1 and presenilin: two unusual aspartyl proteases involved in Alzheimer's disease. NEURODEGENER DIS 2006; 1:168-74. [PMID: 16908986 DOI: 10.1159/000080982] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Two enzymatic activities are required to generate the pathogenic beta-amyloid (Abeta) peptide that accumulates in the brain of Alzheimer's disease patients. Both activities are carried out by two unusual aspartyl proteases known as beta- and gamma-secretase. Their therapeutic inhibition appears, therefore, a promising strategy to treat the disease. Transgenic mouse models in which the genes encoding the secretases have been ablated offer an invaluable tool, on the one hand, to gain more insights into the biological function of these proteases and, on the other hand, to predict the consequences that might be associated with enzyme inhibition in vivo.
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Affiliation(s)
- Diana-Ines Dominguez
- Neuronal Cell Biology and Gene Transfer Laboratory, Department of Human Genetics, KU Leuven and VIB4, Leuven, Belgium.
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Zhang M, Haapasalo A, Kim DY, Ingano LAM, Pettingell WH, Kovacs DM. Presenilin/γ‐secretase activity regulates protein clearance from the endocytic recycling compartment. FASEB J 2006; 20:1176-8. [PMID: 16645046 DOI: 10.1096/fj.05-5531fje] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The presenilin (PS)/gamma-secretase complex proteolytically cleaves more than 20 different proteins in addition to the amyloid precursor protein (APP). These substrates are almost exclusively type I membrane proteins. Many undergo internalization from the cell surface followed by degradation or recycling back to the plasma membrane through the endocytic recycling compartment (ERC). Evidence shows that the PSs also regulate intracellular trafficking of APP and its C-terminal fragments (CTFs). To investigate whether PS/gamma-secretase activity is required for normal endosomal recycling, we performed live cell imaging experiments with fluorescently labeled transferrin, reported to specifically traffic through the ERC. By using pharmacological gamma-secretase inhibitors or cell lines lacking functional PS/gamma-secretase, here we show that PS/gamma-secretase activity is required for clearance of transferrin from the ERC. Interestingly, lack of PS/gamma-secretase function also resulted in the accumulation of APP and APP-CTFs in the ERC in addition to the cell surface. Familial Alzheimer's disease mutations in APP-CTFs did not affect endocytic recycling of these proteins. Our results suggest that PS/gamma-secretase activity is required for normal endosomal recycling of soluble and membrane-associated proteins through the ERC and propose a new mechanism by which impaired PS/gamma-secretase function may eventually contribute to neurodegeneration.
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Affiliation(s)
- Mei Zhang
- Neurobiology of Disease Laboratory, Genetics and Aging Research Unit, Department of Neurology/MIND, Massachusetts General Hospital, Harvard Medical School, 114 16th Street, Charlestown, Massachusetts 02129, USA
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Dillen K, Annaert W. A Two Decade Contribution of Molecular Cell Biology to the Centennial of Alzheimer's Disease: Are We Progressing Toward Therapy? INTERNATIONAL REVIEW OF CYTOLOGY 2006; 254:215-300. [PMID: 17148000 DOI: 10.1016/s0074-7696(06)54005-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Alzheimer's disease (AD), described for the first time 100 years ago, is a neurodegenerative disease characterized by two neuropathological hallmarks: neurofibrillary tangles containing hyperphosphorylated tau and senile plaques. These lesions are likely initiated by an imbalance between production and clearance of amyloid beta, leading to increased oligomerization of these peptides, formation of amyloid plaques in the brain of the patient, and final dementia. Amyloid beta is generated from amyloid precursor protein (APP) by subsequent beta- and gamma-secretase cleavage, the latter being a multiprotein complex consisting of presenilin-1 or -2, nicastrin, APH-1, and PEN-2. Alternatively, APP can be cleaved by alpha- and gamma-secretase, precluding the production of Abeta. In this review, we discuss the major breakthroughs during the past two decades of molecular cell biology and the current genetic and cell biological state of the art on APP proteolysis, including structure-function relationships and subcellular localization. Finally, potential directions for cell biological research toward the development of AD therapies are briefly discussed.
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Affiliation(s)
- Katleen Dillen
- Laboratory for Membrane Trafficking, Center for Human Genetics/VIB1104 & KULeuven, Gasthuisberg O&N1, B-3000 Leuven, Belgium
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Carey RM, Balcz BA, Lopez-Coviella I, Slack BE. Inhibition of dynamin-dependent endocytosis increases shedding of the amyloid precursor protein ectodomain and reduces generation of amyloid beta protein. BMC Cell Biol 2005; 6:30. [PMID: 16095541 PMCID: PMC1208872 DOI: 10.1186/1471-2121-6-30] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2005] [Accepted: 08/11/2005] [Indexed: 11/13/2022] Open
Abstract
Background The amyloid precursor protein (APP) is transported via the secretory pathway to the cell surface, where it may be cleaved within its ectodomain by α-secretase, or internalized within clathrin-coated vesicles. An alternative proteolytic pathway occurs within the endocytic compartment, where the sequential action of β- and γ-secretases generates the amyloid β protein (Aβ). In this study, we investigated the effects of modulators of endocytosis on APP processing. Results Human embryonic kidney cells were transfected with a dominant negative mutant of dynamin I, an important mediator of clathrin-dependent endocytosis, and APP proteolysis was analyzed. Overexpression of the mutant dynamin (dyn I K44A) resulted in increased shedding of the APP ectodomain (sAPPα), accumulation of the C-terminal α-secretase product C83, and a reduction in the release of Aβ. Levels of mature APP on the cell surface were increased in cells expressing dyn I K44A, and internalization of surface-immunolabeled APP, assessed by fluorescence microscopy, was inhibited. Dynamin is a substrate for protein kinase C (PKC), and it was hypothesized that activators of PKC, which are known to stimulate α-secretase-mediated cleavage of APP, might exert their effects by inhibiting dynamin-dependent endocytosis. However, the internalization of surface-biotinylated APP was unaffected by treatment of cells with phorbol 12-myristate 13-acetate in the presence of the α-secretase inhibitor TAPI-1. Conclusion The results indicate that APP is internalized by a dynamin-dependent process, and suggest that alterations in the activity of proteins that mediate endocytosis might lead to significant changes in Aβ production.
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Affiliation(s)
- Robyn M Carey
- Department of Pathology and Laboratory Medicine, Boston University School of Medicine, 715 Albany Street, Rm. L808, Boston MA 02118, USA
| | - Brigitte A Balcz
- Department of Pathology and Laboratory Medicine, Boston University School of Medicine, 715 Albany Street, Rm. L808, Boston MA 02118, USA
- Gemeinnützige Salzburger Landeskliniken Betriebsgesellschaft mbH, Universitätsklinik für Innere Medizin III, Paracelsus Medizinische Privatuniversität, Müllner Hauptstrasse 48, A-5020 Salzburg, Austria
| | - Ignacio Lopez-Coviella
- Department of Pathology and Laboratory Medicine, Boston University School of Medicine, 715 Albany Street, Rm. L808, Boston MA 02118, USA
| | - Barbara E Slack
- Department of Pathology and Laboratory Medicine, Boston University School of Medicine, 715 Albany Street, Rm. L808, Boston MA 02118, USA
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Abad-Rodriguez J, Ledesma MD, Craessaerts K, Perga S, Medina M, Delacourte A, Dingwall C, De Strooper B, Dotti CG. Neuronal membrane cholesterol loss enhances amyloid peptide generation. ACTA ACUST UNITED AC 2005; 167:953-60. [PMID: 15583033 PMCID: PMC2172459 DOI: 10.1083/jcb.200404149] [Citation(s) in RCA: 250] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recent experimental and clinical retrospective studies support the view that reduction of brain cholesterol protects against Alzheimer's disease (AD). However, genetic and pharmacological evidence indicates that low brain cholesterol leads to neurodegeneration. This apparent contradiction prompted us to analyze the role of neuronal cholesterol in amyloid peptide generation in experimental systems that closely resemble physiological and pathological situations. We show that, in the hippocampus of control human and transgenic mice, only a small pool of endogenous APP and its beta-secretase, BACE 1, are found in the same membrane environment. Much higher levels of BACE 1-APP colocalization is found in hippocampal membranes from AD patients or in rodent hippocampal neurons with a moderate reduction of membrane cholesterol. Their increased colocalization is associated with elevated production of amyloid peptide. These results suggest that loss of neuronal membrane cholesterol contributes to excessive amyloidogenesis in AD and pave the way for the identification of the cause of cholesterol loss and for the development of specific therapeutic strategies.
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Affiliation(s)
- Jose Abad-Rodriguez
- Cavalieri Ottolenghi Scientific Institute, Universita degli Studi di Torino, Orbassano, Italy
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Cataldo AM, Petanceska S, Terio NB, Peterhoff CM, Durham R, Mercken M, Mehta PD, Buxbaum J, Haroutunian V, Nixon RA. Aβ localization in abnormal endosomes: association with earliest Aβ elevations in AD and Down syndrome. Neurobiol Aging 2004; 25:1263-72. [PMID: 15465622 DOI: 10.1016/j.neurobiolaging.2004.02.027] [Citation(s) in RCA: 269] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2003] [Revised: 01/08/2004] [Accepted: 02/10/2004] [Indexed: 10/26/2022]
Abstract
Early endosomes are a major site of amyloid precursor protein (APP) processing and a convergence point for molecules of pathologic relevance to Alzheimer's disease (AD). Neuronal endosome enlargement, reflecting altered endocytic function, is a disease-specific response that develops years before the earliest stage of AD and Down syndrome (DS). We examined how endocytic dysfunction is related to Abeta accumulation and distribution in early stage AD and DS. We found by ELISA and immunocytochemistry that the appearance of enlarged endosomes coincided with an initial rise in soluble Abeta40 and Abeta42 peptides, which preceded amyloid deposition. Double-immunofluorescence using numerous Abeta antibodies showed that intracellular Abeta localized principally to rab5-positive endosomes in neurons from AD brains and was prominent in enlarged endosomes. Abeta was not detectable in neurons from normal controls and was diminished after amyloid deposition in neuropathologically confirmed AD. These studies support growing evidence that endosomal pathology contributes significantly to Abeta overproduction and accumulation in sporadic AD and in AD associated with DS and may signify earlier disease-relevant disturbances of the signaling functions of endosomes.
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Affiliation(s)
- Anne M Cataldo
- Mailman Research Center, McLean Hospital, 115 Mill Street, Belmont, MA 02478, USA.
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Chang Y, Tesco G, Jeong WJ, Lindsley L, Eckman EA, Eckman CB, Tanzi RE, Guénette SY. Generation of the beta-amyloid peptide and the amyloid precursor protein C-terminal fragment gamma are potentiated by FE65L1. J Biol Chem 2003; 278:51100-7. [PMID: 14527950 DOI: 10.1074/jbc.m309561200] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Members of the FE65 family of adaptor proteins, FE65, FE65L1, and FE65L2, bind the C-terminal region of the amyloid precursor protein (APP). Overexpression of FE65 and FE65L1 was previously reported to increase the levels of alpha-secretase-derived APP (APPs alpha). Increased beta-amyloid (A beta) generation was also observed in cells showing the FE65-dependent increase in APPs alpha. To understand the mechanism for the observed increase in both A beta and APPs alpha given that alpha-secretase cleavage of a single APP molecule precludes A beta generation, we examined the effects of FE65L1 overexpression on APP C-terminal fragments (APP CTFs). Our data show that FE65L1 potentiates gamma-secretase processing of APP CTFs, including the amyloidogenic CTF C99, accounting for the ability of FE65L1 to increase generation of APP C-terminal domain and A beta 40. The FE65L1 modulation of these processing events requires binding of FE65L1 to APP and APP CTFs and is not because of a direct effect on gamma-secretase activity, because Notch intracellular domain generation is not altered by FE65L1. Furthermore, enhanced APP CTF processing can be detected in early endosome vesicles but not in endoplasmic reticulum or Golgi membranes, suggesting that the effects of FE65L1 occur at or near the plasma membrane. Finally, although FE65L1 increases APP C-terminal domain production, it does not mediate the APP-dependent transcriptional activation observed with FE65.
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Affiliation(s)
- Yang Chang
- Genetics and Aging Research Unit, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129-4404, USA
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Ehehalt R, Keller P, Haass C, Thiele C, Simons K. Amyloidogenic processing of the Alzheimer beta-amyloid precursor protein depends on lipid rafts. J Cell Biol 2003; 160:113-23. [PMID: 12515826 PMCID: PMC2172747 DOI: 10.1083/jcb.200207113] [Citation(s) in RCA: 809] [Impact Index Per Article: 38.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Formation of senile plaques containing the beta-amyloid peptide (A beta) derived from the amyloid precursor protein (APP) is an invariant feature of Alzheimer's disease (AD). APP is cleaved either by beta-secretase or by alpha-secretase to initiate amyloidogenic (release of A beta) or nonamyloidogenic processing of APP, respectively. A key to understanding AD is to unravel how access of these enzymes to APP is regulated. Here, we demonstrate that lipid rafts are critically involved in regulating A beta generation. Reducing cholesterol levels in N2a cells decreased A beta production. APP and the beta-site APP cleavage enzyme (BACE1) could be induced to copatch at the plasma membrane upon cross-linking with antibodies and to segregate away from nonraft markers. Antibody cross-linking dramatically increased production of A beta in a cholesterol-dependent manner. A beta generation was dependent on endocytosis and was reduced after expression of the dynamin mutant K44A and the Rab5 GTPase-activating protein, RN-tre. This inhibition could be overcome by antibody cross-linking. These observations suggest the existence of two APP pools. Although APP inside raft clusters seems to be cleaved by beta-secretase, APP outside rafts undergoes cleavage by alpha-secretase. Thus, access of alpha- and beta-secretase to APP, and therefore A beta generation, may be determined by dynamic interactions of APP with lipid rafts.
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Affiliation(s)
- Robert Ehehalt
- Max Planck Institute of Molecular Cell Biology and Genetics, D-01307 Dresden, Germany
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