Identification and characterization of PEBP as a calpain substrate.
Calpains are calcium- and thiol-dependent proteases whose dysregulation has been implicated in a number of diseases and conditions such as cardiovascular dysfunction, ischemic stroke, and Alzheimer's disease (AD). While the effects of calpain activity are evident, the precise mechanism(s) by which dysregulated calpain activity results in cellular degeneration are less clear. In order to determine the impact of calpain activity, there is a need to identify the range of specific calpain substrates. Using an in vitro proteomics approach we confirmed that phosphatidylethanolamine-binding protein (PEBP) as a novel in vitro and in situ calpain substrate. We also observed PEBP proteolysis in a model of brain injury in which calpain is clearly activated. In addition, with evidence of calpain dysregulation in AD, we quantitated protein levels of PEBP in postmortem brain samples from the hippocampus of AD and age-matched controls and found that PEBP levels were approximately 20% greater in AD. Finally, with previous evidence that PEBP may act as a serine protease inhibitor, we tested PEBP as an inhibitor of the proteasome and found that PEBP inhibited the chymostrypsin-like activity of the proteasome by approximately 30%. Together these data identify PEBP as a potential in vivo calpain substrate and indicate that increased PEBP levels may contribute to impaired proteasome function.
Chen
Qinghua
Q
Department of Gerontology, University of Kentucky, Lexington, Kentucky 40536, USA.
Wang
Susan
S
Thompson
Stephanie N
SN
Hall
Edward D
ED
Guttmann
Rodney P
RP
D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000201:enzymology* / Q000503:physiopathology; D000818:Animals; D001930:Brain Injuries / Q000201:enzymology / Q000503:physiopathology; D002154:Calpain / Q000378:metabolism*; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D005260:Female; D006624:Hippocampus / Q000201:enzymology* / Q000503:physiopathology; D006801:Humans; D008297:Male; D051379:Mice; D009410:Nerve Degeneration / Q000201:enzymology / Q000503:physiopathology; D049488:Phosphatidylethanolamine Binding Protein / Q000378:metabolism* / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D040901:Proteomics; D015842:Serine Proteinase Inhibitors / Q000378:metabolism* / Q000494:pharmacology
C511482:PEBP1 protein, human; D049488:Phosphatidylethanolamine Binding Protein; D061988:Proteasome Inhibitors; D015842:Serine Proteinase Inhibitors; D002154:Calpain; D046988:Proteasome Endopeptidase Complex