Opposing roles of prion protein in oxidative stress- and ER stress-induced apoptotic signaling.
Although the prion protein is abundantly expressed in the CNS, its biological functions remain unclear. To determine the endogenous function of the cellular prion protein (PrP(c)), we compared the effects of oxidative stress and endoplasmic reticulum (ER) stress inducers on apoptotic signaling in PrP(c)-expressing and PrP(ko) (knockout) neural cells. H(2)O(2), brefeldin A (BFA), and tunicamycin (TUN) induced increases in caspase-9 and caspase-3, PKCdelta proteolytic activation, and DNA fragmentation in PrP(c) and PrP(ko) cells. Interestingly, ER stress-induced activation of caspases, PKCdelta, and apoptosis was significantly exacerbated in PrP(c) cells, whereas H(2)O(2)-induced proapoptotic changes were suppressed in PrP(c) compared to PrP(ko) cells. Additionally, caspase-12 and caspase-8 were activated only in the BFA and TUN treatments. Inhibitors of caspase-9, caspase-3, and PKCdelta significantly blocked H(2)O(2)-, BFA-, and TUN-induced apoptosis, whereas the caspase-8 inhibitor attenuated only BFA- and TUN-induced cell death, and the antioxidant MnTBAP blocked only H(2)O(2)-induced apoptosis. Overexpression of the kinase-inactive PKCdelta(K376R) or the cleavage site-resistant PKCdelta(D327A) mutant suppressed both ER and oxidative stress-induced apoptosis. Thus, PrP(c) plays a proapoptotic role during ER stress and an antiapoptotic role during oxidative stress-induced cell death. Together, these results suggest that cellular PrP enhances the susceptibility of neural cells to impairment of protein processing and trafficking, but decreases the vulnerability to oxidative insults, and that PKCdelta is a key downstream mediator of cellular stress-induced neuronal apoptosis.
Department of Biomedical Sciences, Iowa Center for Advanced Neurotoxicology, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA.
Vellareddy
V
Anantharam
Arthi
A
Kanthasamy
Christopher J
CJ
Choi
Dustin P
DP
Martin
Calivarathan
C
Latchoumycandane
Jüergen A
JA
Richt
Anumantha G
AG
Kanthasamy
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D015153:Blotting, Western; D020126:Brefeldin A / Q000494:pharmacology; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D053938:DNA Fragmentation; D004721:Endoplasmic Reticulum / Q000502:physiology* / Q000648:ultrastructure; D005434:Flow Cytometry; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D051379:Mice; D018345:Mice, Knockout; D050505:Mutant Proteins; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D018384:Oxidative Stress / Q000502:physiology*; D018621:PrPC Proteins / Q000378:metabolism*; D051745:Protein Kinase C-delta / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D014415:Tunicamycin / Q000494:pharmacology
D050505:Mutant Proteins; D018621:PrPC Proteins; D017382:Reactive Oxygen Species; D014415:Tunicamycin; D020126:Brefeldin A; D051745:Protein Kinase C-delta; D020169:Caspases