Abstract
Amyloid-β proteins (Aβ) of 42 (Aβ42) and 40 aa (Aβ40) accumulate as senile plaques (SP) and cerebrovascular amyloid protein deposits that are defining diagnostic features of Alzheimer’s disease (AD). A number of rare mutations linked to familial AD (FAD) on the Aβ precursor protein (APP), Presenilin-1 (PS1), Presenilin- 2 (PS2), Adamalysin10, and other genetic risk factors for sporadic AD such as the ε4 allele of Apolipoprotein E (ApoE-ε4) foster the accumulation of Aβ and also induce the entire spectrum of pathology associated with the disease. Aβ accumulation is therefore a key pathological event and a prime target for the prevention and treatment of AD. APP is sequentially processed by β-site APP cleaving enzyme (BACE1) and γ-secretase, a multisubunit PS1/PS2-containing integral membrane protease, to generate Aβ. Although Aβ accumulates in all forms of AD, the only pathways known to be affected in FAD increase Aβ production by APP gene duplication or via base substitutions on APP and γ-secretase subunits PS1 and PS2 that either specifically increase the yield of the longer Aβ42 or both Aβ40 and Aβ42. However, the vast majority of AD patients accumulate Aβ without these known mutations. This led to proposals that impairment of Aβ degradation or clearance may play a key role in AD pathogenesis. Several candidate enzymes, including Insulin-degrading enzyme (IDE), Neprilysin (NEP), Endothelin-converting enzyme (ECE), Angiotensin converting enzyme (ACE), Plasmin, and Matrix metalloproteinases (MMPs) have been identified and some have even been successfully evaluated in animal models. Several studies also have demonstrated the capacity of γ-secretase inhibitors to paradoxically increase the yield of Aβ and we have recently established that the mechanism is by skirting Aβ degradation. This review outlines major cellular pathways of Aβ degradation to provide a basis for future efforts to fully characterize the panel of pathways responsible for Aβ turnover.
Keywords: Alzheimer’s disease, amyloid β degradation, amyloid β peptide, endothelin-converting enzyme, insulin-degrading enzyme, neprilysin, neurodegeneration.
Current Alzheimer Research
Title:Amyloid-Beta Protein Clearance and Degradation (ABCD) Pathways and their Role in Alzheimer's Disease
Volume: 12 Issue: 1
Author(s): Robert J. Baranello, Krishna L. Bharani, Vasudevaraju Padmaraju, Nipun Chopra, Debomoy K. Lahiri, Nigel H. Greig, Miguel A. Pappolla and Kumar Sambamurti
Affiliation:
Keywords: Alzheimer’s disease, amyloid β degradation, amyloid β peptide, endothelin-converting enzyme, insulin-degrading enzyme, neprilysin, neurodegeneration.
Abstract: Amyloid-β proteins (Aβ) of 42 (Aβ42) and 40 aa (Aβ40) accumulate as senile plaques (SP) and cerebrovascular amyloid protein deposits that are defining diagnostic features of Alzheimer’s disease (AD). A number of rare mutations linked to familial AD (FAD) on the Aβ precursor protein (APP), Presenilin-1 (PS1), Presenilin- 2 (PS2), Adamalysin10, and other genetic risk factors for sporadic AD such as the ε4 allele of Apolipoprotein E (ApoE-ε4) foster the accumulation of Aβ and also induce the entire spectrum of pathology associated with the disease. Aβ accumulation is therefore a key pathological event and a prime target for the prevention and treatment of AD. APP is sequentially processed by β-site APP cleaving enzyme (BACE1) and γ-secretase, a multisubunit PS1/PS2-containing integral membrane protease, to generate Aβ. Although Aβ accumulates in all forms of AD, the only pathways known to be affected in FAD increase Aβ production by APP gene duplication or via base substitutions on APP and γ-secretase subunits PS1 and PS2 that either specifically increase the yield of the longer Aβ42 or both Aβ40 and Aβ42. However, the vast majority of AD patients accumulate Aβ without these known mutations. This led to proposals that impairment of Aβ degradation or clearance may play a key role in AD pathogenesis. Several candidate enzymes, including Insulin-degrading enzyme (IDE), Neprilysin (NEP), Endothelin-converting enzyme (ECE), Angiotensin converting enzyme (ACE), Plasmin, and Matrix metalloproteinases (MMPs) have been identified and some have even been successfully evaluated in animal models. Several studies also have demonstrated the capacity of γ-secretase inhibitors to paradoxically increase the yield of Aβ and we have recently established that the mechanism is by skirting Aβ degradation. This review outlines major cellular pathways of Aβ degradation to provide a basis for future efforts to fully characterize the panel of pathways responsible for Aβ turnover.
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Baranello J. Robert, Bharani L. Krishna, Padmaraju Vasudevaraju, Chopra Nipun, Lahiri K. Debomoy, Greig H. Nigel, Pappolla A. Miguel and Sambamurti Kumar, Amyloid-Beta Protein Clearance and Degradation (ABCD) Pathways and their Role in Alzheimer's Disease, Current Alzheimer Research 2015; 12 (1) . https://dx.doi.org/10.2174/1567205012666141218140953
DOI https://dx.doi.org/10.2174/1567205012666141218140953 |
Print ISSN 1567-2050 |
Publisher Name Bentham Science Publisher |
Online ISSN 1875-5828 |
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Aims and Scope: Introduction: Alzheimer's disease (AD) poses a significant global health challenge, with an increasing prevalence that demands concerted efforts to advance our understanding and strategies for prevention, diagnosis, treatment, and rehabilitation. This thematic issue aims to bring together cutting-edge research and innovative approaches from multidisciplinary perspectives to address ...read more
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Alzheimer's disease (AD) poses a significant global health challenge, with an increasing number of individuals affected yearly. Deep learning, a subfield of artificial intelligence, has shown immense potential in various domains, including healthcare. This thematic issue of Current Alzheimer Research explores the application of deep learning techniques in advancing our ...read more
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