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The amyloid beta-protein precursor of Alzheimer's disease is degraded extracellularly by a Kunitz protease inhibitor domain-sensitive trypsin-like serine protease in cultures of chick sympathetic neurons

Citation

Caswell, MD and San Mok, S and Henry, A and Cappai, R and Klug, G and Beyreuther, K and Masters, CL and Small, DH, The amyloid beta-protein precursor of Alzheimer's disease is degraded extracellularly by a Kunitz protease inhibitor domain-sensitive trypsin-like serine protease in cultures of chick sympathetic neurons, European Journal of Biochemistry: The Febs Journal, 266, (2) pp. 509-516. ISSN 0014-2956 (1999) [Refereed Article]


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The definitive published version is available online at: http://www3.interscience.wiley.com/

DOI: doi:10.1046/j.1432-1327.1999.00886.x

Abstract

The amyloid β-protein precursor (APP) of Alzheimer's disease (AD) is cleaved either by α-secretase to generate an N-terminally secreted fragment, or by β- and γ-secretases to generate the β-amyloid protein (Aβ). The accumulation of Aβ in the brain is an important step in the pathogenesis of AD. Alternative mRNA splicing can generate isoforms of APP which contain a Kunitz protease inhibitor (KPI) domain. However, little is known about the physiological function of this domain. In the present study, the metabolic turnover of APP was examined in cultured chick sympathetic neurons. APP was labelled by incubating neurons for 5 h with [35S]methionine and [35S]cysteine. Intracellular labelled APP decayed in a biphasic pattern suggesting that trafficking occurs through two metabolic compartments. The half-lives for APP in each compartment were 1.5 and 5.7 h, respectively. A small fraction (10%) of the total APP was secreted into the culture medium where it was degraded with a half-life of 9 h. Studies using specific protease inhibitors demonstrated that this extracellular breakdown was due to cleavage by a trypsin-like serine protease that was secreted into the culture medium. Significantly, this protease was inhibited by a recombinant isoform of APP (sAPP751), which contains a region homologous to the Kunitz protease inhibitor (KPI) domain. These results suggest that KPI forms of APP regulate extracellular cleavage of secreted APP by inhibiting the activity of a secreted APP-degrading protease.

Item Details

Item Type:Refereed Article
Keywords: Alzheimer; amyloid; protease; Kunitz protease inhibitor; proteolytic processing
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:75400
Year Published:1999
Web of Science® Times Cited:12
Deposited By:Research Division
Deposited On:2012-01-30
Last Modified:2012-02-02
Downloads:0

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