title: Involvement of double-stranded RNA-dependent protein kinase and phosphorylation of eukaryotic initiation factor-2alpha in neuronal degeneration.
abstract: Inhibition of protein translation plays an important role in apoptosis. While double-stranded RNA-dependent protein kinase (PKR) is named as it is activated by double-stranded RNA produced by virus, its activation induces an inhibition of protein translation and apoptosis via the phosphorylation of the eukaryotic initiation factor 2alpha (eIF2alpha). PKR is also a stress kinase and its levels increase during ageing. Here we show that PKR activation and eIF2alpha phosphorylation play a significant role in apoptosis of neuroblastoma cells and primary neuronal cultures induced by the beta-amyloid (Abeta) peptides, the calcium ionophore A23187 and flavonoids. The phosphorylation of eIF2alpha and the number of apoptotic cells were enhanced in over-expressed wild-type PKR neuroblastoma cells exposed to Abeta peptide, while dominant-negative PKR reduced eIF2alpha phosphorylation and apoptosis induced by Abeta peptide. Primary cultured neurons from PKR knockout mice were also less sensitive to Abeta peptide toxicity. Activation of PKR and eIF2alpha pathway by Abeta peptide are triggered by an increase in intracellular calcium because the intracellular calcium chelator BAPTA-AM significantly reduced PKR phosphorylation. Taken together, these results reveal that PKR and eIF2alpha phosphorylation could be involved in the molecular signalling events leading to neuronal apoptosis and death and could be a new target in neuroprotection.
authors.affiliation: Department of Anatomy, Faculty of Medicine, and Central Laboratory of the Institute of Molecular Technology for Drug Discovery and Synthesis, The University of Hong Kong, Hong Kong.
authors.forename: Raymond Chuen-Chung
authors.initials: RC
authors.lastname: Chang
authors.forename: Ka-Chun
authors.initials: KC
authors.lastname: Suen
authors.forename: Chi-Him
authors.initials: CH
authors.lastname: Ma
authors.forename: Wassim
authors.initials: W
authors.lastname: Elyaman
authors.forename: Ho-Keung
authors.initials: HK
authors.lastname: Ng
authors.forename: Jacques
authors.initials: J
authors.lastname: Hugon
mesh_terms: D016229:Amyloid beta-Peptides / Q000633:toxicity; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D000001:Calcimycin / Q000633:toxicity; D002118:Calcium / Q000378:metabolism; D002452:Cell Count; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism*; D019833:Genistein / Q000633:toxicity; D006801:Humans; D007476:Ionophores / Q000633:toxicity; D051379:Mice; D008810:Mice, Inbred C57BL; D009447:Neuroblastoma / Q000378:metabolism* / Q000473:pathology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D010446:Peptide Fragments / Q000633:toxicity; D010766:Phosphorylation / Q000187:drug effects; D011794:Quercetin / Q000633:toxicity; D051381:Rats; D017207:Rats, Sprague-Dawley; D019892:eIF-2 Kinase / Q000378:metabolism*
chemical_list: D016229:Amyloid beta-Peptides; D015852:Eukaryotic Initiation Factor-2; D007476:Ionophores; D010446:Peptide Fragments; C075222:amyloid beta-protein (1-42); C074636:amyloid beta-protein (25-35); D000001:Calcimycin; D011794:Quercetin; D019833:Genistein; D019892:eIF-2 Kinase; D002118:Calcium