Depletion of Beclin-1 Due to Proteolytic Cleavage by Caspases in the Alzheimer's Disease Brain

Troy T. Rohn, Boise State University
Ellen Wirawan, VIB
Raquel J. Brown, Boise State University
Jordan R. Harris, Boise State University
Eliezer Masliah, University of California San Diego
Peter Vandenabeele, VIB

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NOTICE: This is the author’s version of a work accepted for publication by Elsevier. Changes resulting from the publishing process, including peer review, editing, corrections, structural formatting and other quality control mechanisms, may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. The definitive version will be published in Neurobiology of Disease, Volume xx, Issue xx, 2010. DOI: 10.1016/j.nbd.2010.11.003

Abstract

The Beclin-1 protein is essential for the initiation of autophagy and recent studies suggest this function may be compromised in Alzheimer’s disease (AD). In addition, in vitro studies have supported a loss of function of Beclin-1 due to proteolytic modification by caspases. In the present study we examined whether caspase-cleavage of Beclin-1 occurs in the AD brain by designing a site-directed caspase-cleavage antibody based upon a known cleavage site within the protein at position D149. We confirmed that Beclin-1 is an excellent substrate for caspase-3 and demonstrate cleavage led to the formation of a 35 kDa C-terminal fragment labeled by our novel antibody following Western blot analysis. Application of this antibody termed Beclin-1 caspase-cleavage product antibody or BeclinCCP in frontal cortex tissue sections revealed strong immunolabeling within astrocytes that localized with plaque-regions and along blood vessels in all AD cases examined. In addition, weaker, more variable BeclinCCP labeling was also observed within neurofibrillary tangles that co-localized with the early tau conformational marker, MC-1 as well as the late tangle marker, PHF-1. Collectively, these data support a depletion of Beclin-1 in AD following caspase-cleavage.