Endoplasmic Reticulum Stress-induced Cysteine Protease Activation in Cortical Neurons

• Published in: The Journal of biological chemistry Vol. 276; no. 48; pp. 44736 - 44743
• Main Authors: Siman, Robert, Flood, Dorothy G., Thinakaran, Gopal, Neumar, Robert W.
• Format: Journal Article
• Language: English
• Published: American Society for Biochemistry and Molecular Biology 30-11-2001
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M104092200

Endoplasmic reticulum (ER) stress elicits protective responses of chaperone induction and translational suppression and, when
unimpeded, leads to caspase-mediated apoptosis. Alzheimer's disease-linked mutations in presenilin-1 (PS-1) reportedly impair
ER stress-mediated protective responses and enhance vulnerability to degeneration. We used cleavage site-specific antibodies
to characterize the cysteine protease activation responses of primary mouse cortical neurons to ER stress and evaluate the
influence of a PS-1 knock-in mutation on these and other stress responses. Two different ER stressors lead to processing of
the ER-resident protease procaspase-12, activation of calpain, caspase-3, and caspase-6, and degradation of ER and non-ER
protein substrates. Immunocytochemical localization of activated caspase-3 and a cleaved substrate of caspase-6 confirms that
caspase activation extends into the cytosol and nucleus. ER stress-induced proteolysis is unchanged in cortical neurons derived
from the PS-1 P264L knock-in mouse. Furthermore, the PS-1 genotype does not influence stress-induced increases in chaperones
Grp78/BiP and Grp94 or apoptotic neurodegeneration. A similar lack of effect of the PS-1 P264L mutation on the activation
of caspases and induction of chaperones is observed in fibroblasts. Finally, the PS-1 knock-in mutation does not alter activation
of the protein kinase PKR-like ER kinase (PERK), a trigger for stress-induced translational suppression. These data demonstrate
that ER stress in cortical neurons leads to activation of several cysteine proteases within diverse neuronal compartments
and indicate that Alzheimer's disease-linked PS-1 mutations do not invariably alter the proteolytic, chaperone induction,
translational suppression, and apoptotic responses to ER stress.