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Evidence supporting the role of calpain in the α-processing of amyloid-β precursor protein.
MedLine Citation:
PMID:  22480599     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Amyloid plaques are a hallmark of the aging and senile dementia brains, yet their mechanism of origins has remained elusive. A central issue is the regulatory mechanism and identity of α-secretase, a protease responsible for α-processing of amyloid-β precursor protein (APP). A remarkable feature of this enzyme is its high sensitivity to a wide range of cellular stimulators, many of which are agonists for Ca(2+) signaling. This feature, together with previous work in our laboratory, has suggested that calpain, a Ca(2+)-dependent protease, plays a key role in APP α-processing. In this study we report that overexpression of the μ-calpain gene in HEK293 cells resulted in a 2.7-fold increase of the protein levels. Measurements of intracellular calpain enzymatic activity revealed that the calpain overexpressing cells displayed a prominent elevation of the activity compared to wild-type cells. When the cells were stimulated by nicotine, glutamate or phorbol 12,13-dibutylester, the activity increase was even more remarkable and sensitive to calpeptin, a calpain inhibitor. Meanwhile, APP secretion from the calpain overexpressing cells was robustly increased under both resting and stimulated conditions over wild-type cells. Furthermore, cell surface biotinylation experiments showed that μ-calpain was clearly detected among the cell surface proteins. These data together support our view that calpain should be a reasonable candidate for α-secretase for further study. This model is discussed with an interesting fact that three other deposited proteins (tau, spectrin and crystalline) are also the known substrates of calpain. Finally we discuss some current misconceptions in senile dementia research.
Authors:
Huey T Nguyen; Darrell R Sawmiller; Qi Wu; Jerome J Maleski; Ming Chen
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-4-3
Journal Detail:
Title:  Biochemical and biophysical research communications     Volume:  -     ISSN:  1090-2104     ISO Abbreviation:  -     Publication Date:  2012 Apr 
Date Detail:
Created Date:  2012-4-6     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0372516     Medline TA:  Biochem Biophys Res Commun     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Published by Elsevier Inc.
Affiliation:
Aging Research Laboratory, Bay Pines VA Medical Center, Bay Pines, FL 33744, USA.
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