Protein Disulfide Isomerase Regulates Endoplasmic Reticulum Stress and the Apoptotic Process during Prion Infection and PrP Mutant-Induced Cytotoxicity
et al. (2012) Protein Disulfide Isomerase Regulates Endoplasmic Reticulum Stress and the Apoptotic Process
during Prion Infection and PrP Mutant-Induced Cytotoxicity. PLoS ONE 7(6): e38221. doi:10.1371/journal.pone.0038221
Protein Disulfide Isomerase Regulates Endoplasmic Reticulum Stress and the Apoptotic Process during Prion Infection and PrP Mutant-Induced Cytotoxicity
Shao-Bin Wang 0
Qi Shi 0
Yin Xu 0
Wu-Ling Xie 0
Jin Zhang 0
Chan Tian 0
Yan Guo 0
Ke Wang 0
Bao- Yun Zhang 0
Cao Chen 0
Chen Gao 0
Xiao-Ping Dong 0
Ilia V. Baskakov, University of Maryland, United States of America
0 1 State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention , Beijing , People's Republic of China, 2 Chinese Academy of Sciences Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences , Beijing , China
Background: Protein disulfide isomerase (PDI), is sorted to be enzymatic chaperone for reconstructing misfolded protein in endoplasmic reticulum lumen. Recently, PDI has been identified as a link between misfolded protein and neuron apoptosis. However, the potential for PDI to be involved in the pathogenesis of prion disease remains unknown. In this study, we propose that PDI may function as a pleiotropic regulator in the cytotoxicity induced by mutated prion proteins and in the pathogenesis of prion diseases. Methodology/Principal Findings: To elucidate potential alterations of PDI in prion diseases, the levels of PDI and relevant apoptotic executors in 263K infected hamsters brain tissues were evaluated with the use of Western blots. Abnormal upregulation of PDI, Grp78 and Grp58 was detected. Dynamic assays of PDI alteration identified that the upregulation of PDI started at the early stage and persistently increased till later stage. Obvious increases of PDI and Grp78 levels were also observed in cultured cells transiently expressing PrP mutants, PrP-KDEL or PrP-PG15, accompanied by significant cytotoxicities. Excessive expression of PDI partially eased ER stress and cell apoptosis caused by accumulation of PrP-KDEL, but had less effect on cytotoxicity induced by PrP-PG15. Knockdown of endogenous PDI significantly amended cytotoxicity of PrP-PG15, but had little influence on that of PrP-KDEL. A series of membrane potential assays found that apoptosis induced by misfolded PrP proteins could be regulated by PDI via mitochondrial dysfunction. Moreover, biotin-switch assays demonstrated active S-nitrosylted modifications of PDI (SNO-PDI) both in the brains of scrapie-infected rodents and in the cells with misfolded PrP proteins. Conclusion/Significance: Current data in this study highlight that PDI and its relevant executors may function as a pleiotropic regulator in the processes of different misfolded PrP proteins and at different stages during prion infection. SNO-PDI may feed as an accomplice for PDI apoptosis.
-
Funding: This work was supported by Chinese National Natural Science Foundation Grant (30800975, 81100980, 81101302 and 31100117), National Basic
Research Program of China (973 Program) (2007CB310505), China Mega-Project for Infectious Disease (2009ZX10004-101) and SKLID Development Grant
(2008SKLID102, 2011SKLID211 and 2011SKLID204). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the
manuscript.
Competing Interests: The authors have declared that no competing interests exist.
Prion disorders, or transmissible spongiform encephalopathies
(TSEs), are fatal neurodegenerative diseases affecting humans and
many species of animals, for example Creutzfeldt-Jakob disease
(CJD) in humans, scrapie in sheep and goat, and bovine
spongiform encephalopathy (BSE) in cattle. Prion-related disorders
share common neuropathology characteristics, such as spongiform
degeneration, extensive neuronal loss and the accumulation of
PrPSc, a misfolded and protease-resistant form of the normal prion
protein (PrPC) [1]. Although the mechanism of PrPSc pathogenesis
is still controversial, mounting evidences suggests that
perturbations in endoplasmic reticulum (ER) homeostasis or mitochondrial
dysfunction induced by PrPSc or misfolded prion proteins may
contribute to cell death or neurodegenerative pathology in prion
disease [2,3,4].
When ER homeostasis is perturbed, ER stress triggers the
survival pathway, unfolding protein response (UPR), which is
associated with upregulation of ER-derived chaperones and
protein-folding enzymes leading the misfolded proteins
undergoing the process of degeneration [5,6]. Conventionally, activation
of UPR increase pro-survival effects including an increased
expression of the glucose-related protein (Grp) family, such as
Grp78/Bip, and chaperones with protein disulfide isomerase
(PDI) -like activities, such as PDI and Grp58 (also known as
PDIA3) [7]. In the terminal (...truncated)