Activation of neuronal caspase-3 by intracellular accumulation of wild-type Alzheimer amyloid precursor protein.
Forced overexpression of wild-type Alzheimer amyloid precursor protein (APP) causes postmitotic neurons to degenerate. Caspase-3 (CPP32) is a principal cell death protease involved in neuronal apoptosis during physiological development and under pathological conditions. Here, we investigated whether APP overexpression activates caspase-3 in human postmitotic neurons using adenovirus-mediated gene transfer. When a recombinant adenovirus vector expressing human wild-type APP695 was infected in vitro into neurally differentiated embryonal carcinoma NT2 cells, only postmitotic neurons underwent severe degeneration. Before neurodegeneration, full-length APP- and Abeta-immunoreactive peptides were accumulated in infected neurons, and caspase-3-like protease activity was markedly elevated. Western blot analysis revealed that activated caspase-3 subunits were generated in APP-accumulating neurons. Such neuronal caspase-3 activation was undetectable in NT2 neurons infected with beta-galactosidase-expressing adenovirus. Addition of the caspase-3 inhibitor acetyl-Asp-Glu-Val-Asp-aldehyde to the culture medium significantly reduced the severity of degeneration exhibited by APP-overexpressing neurons. Immunocytochemical analyses revealed that some APP-accumulating neurons contained activated caspase-3 subunits and exhibited the characteristics of apoptosis, such as chromatin condensation and DNA fragmentation. Activation of caspase-3 was also observed in vivo in rat hippocampal neurons infected with the APP-expressing adenovirus. These results suggest that wild-type APP is an intrinsic activator of caspase-3-mediated death machinery in postmitotic neurons.
Uetsuki
T
T
Division of Regulation of Macromolecular Functions, Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan.
Takemoto
K
K
Nishimura
I
I
Okamoto
M
M
Niinobe
M
M
Momoi
T
T
Miura
M
M
Yoshikawa
K
K
D000256:Adenoviridae / Q000235:genetics; D000544:Alzheimer Disease / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism*; D000818:Animals; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D016923:Cell Death / Q000502:physiology; D004789:Enzyme Activation; D018014:Gene Transfer Techniques; D005822:Genetic Vectors; D006801:Humans; D009474:Neurons / Q000201:enzymology* / Q000473:pathology; D051381:Rats; D014407:Tumor Cells, Cultured
D016564:Amyloid beta-Protein Precursor; C505407:CASP3 protein, human; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases