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Heparin Activates β-Secretase (BACE1) of Alzheimer's Disease and Increases Autocatalysis of the Enzyme

Citation

Beckman, M and Holsinger, RMD and Small, DH, Heparin Activates β-Secretase (BACE1) of Alzheimer's Disease and Increases Autocatalysis of the Enzyme, Biochemistry, 45, (21) pp. 6703-6714. ISSN 0006-2960 (2006) [Refereed Article]

DOI: doi:10.1021/bi052498t

Abstract

BACE1 is an aspartic protease that generates the N-terminus of the β-amyloid protein (Aβ) from the β-amyloid precursor protein (APP). BACE1 is a key target for Alzheimer drug development. However, little is known about the physiological regulation of the enzyme. Heparin can promote β-secretase cleavage of APP in neuroblastoma cells. However, heparin has also been reported to directly inhibit BACE1 activity in vitro. To clarify the role of heparin in regulating BACE1, we examined the effect of heparin on the activity of recombinant human BACE1 (rBACE1) in vitro. Low concentrations (1 μg/mL) of heparin were found to stimulate rBACE1, increasing enzyme V max and decreasing the K M. In contrast, higher concentrations of heparin (10 or 100 μg/mL) were inhibitory. Heparin affinity chromatography demonstrated that heparin interacted strongly with the zymogen form of rBACE1 and bound to a peptide homologous to the N-terminal pro sequence of BACE1. Mature (pro sequence cleaved) enzyme lacked the capacity to be stimulated by heparin, indicating that the pro domain was necessary for the stimulation by heparin. Furthermore, in the presence of stimulatory concentrations of heparin, there was an increase in autocatalytic cleavage of the protease domain and a subsequent loss of enzyme activity in vitro. Our results strongly suggest that heparin stimulates the partially active BACE1 zymogen, and we propose that the activation is mediated by high-affinity binding of heparin to the pro domain. Our study provides evidence that heparan sulfate proteoglycans could regulate the rate of Aβ production in vivo. © 2006 American Chemical Society.

Item Details

Item Type:Refereed Article
Research Division:Medical and Health Sciences
Research Group:Neurosciences
Research Field:Neurosciences not elsewhere classified
Objective Division:Health
Objective Group:Clinical Health (Organs, Diseases and Abnormal Conditions)
Objective Field:Neurodegenerative Disorders Related to Ageing
Author:Small, DH (Professor David Small)
ID Code:61094
Year Published:2006
Web of Science® Times Cited:36
Deposited By:Menzies Institute for Medical Research
Deposited On:2010-02-25
Last Modified:2010-09-16
Downloads:0

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