title: Inhibition of PKR protects against tunicamycin-induced apoptosis in neuroblastoma cells.
abstract: Endoplasmic reticulum (ER) dysfunction is thought to play a significant role in several neurological disorders, including Alzheimer's disease, Parkinson's disease, Huntington's disease, multiple sclerosis, amyotrophic lateral sclerosis, cerebral ischemia, and the prion diseases. ER dysfunction can be mimicked by cellular stress signals such as disruption of calcium homeostasis, inhibition of protein glycosylation, and reduction of disulfide bonds, which results in accumulation of misfolded proteins in the ER and leads to cell death by apoptosis. Tunicamycin, which is an inhibitor of protein glycosylation, induces ER stress and apoptosis. In this study, we examined the involvement of double stranded (ds) RNA-activated protein kinase PKR in tunicamycin-induced apoptosis. We used overexpression of the trans-dominant negative, catalytically inactive mutant K296R to inhibit PKR activity in neuroblastoma cells. We demonstrate that inhibition of PKR activation in response to tunicamycin protects neuronal cells from undergoing apoptosis. Furthermore, K296R overexpressing cells show defective PKR activation, delayed eIF2α phosphorylation, dramatically delayed ATF4 expression. In addition, both caspase-3 activation and C/EBP homologous protein (CHOP, also known as GADD153) induction, which are markers of apoptotic cells, are absent from K296R overexpression cells in response to tunicamycin. These results establish that PKR activation plays a major regulatory role in induction of apoptosis in response to ER stress and indicates the potential of PKR as possible target for neuroprotective therapeutics.
authors: Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA.
authors: Lauren S
authors: LS
authors: Vaughn
authors: Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA.
authors: Brittany
authors: B
authors: Snee
authors: Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA. Electronic address: patelr@biol.sc.edu.
authors: Rekha C
authors: RC
authors: Patel
mesh_terms: D019943:Amino Acid Substitution; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001120:Arginine / Q000235:genetics; D019610:Cytoprotection / Q000187:drug effects* / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D006801:Humans; D008239:Lysine / Q000235:genetics; D020125:Mutation, Missense / Q000502:physiology; D009447:Neuroblastoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D014407:Tumor Cells, Cultured; D014415:Tunicamycin / Q000494:pharmacology*; D019892:eIF-2 Kinase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000276:immunology / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D014415:Tunicamycin; D001120:Arginine; D019892:eIF-2 Kinase; D008239:Lysine
keywords: ALS; Apoptosis; C/EBP homologous protein; CHOP; ER; EV; IFN; IRES; Neuronal; PERK; PKR; PKR-like endoplasmic reticulum resident kinase; Tunicamycin; UPR; alpha subunit of eukaryotic initiation factor 2; amyotrophic lateral sclerosis; double-stranded; ds; eIF2alpha; eIF2α; empty vector; endoplasmic reticulum; interferon; internal ribosome entry site; protein kinase, RNA-activated; uORFs; unfolded protein response; upstream open reading frames