title: Phosphorylated PKR contributes the induction of GRP94 under ER stress.
abstract: Phosphorylated double-stranded RNA-dependent protein kinase (PKR) is thought to play an important role during ER stress induced cell death, but its molecular mechanism of action has not yet been clarified completely. To resolve this issue, we employed a PKR inhibitor together with ER stress inducers (tunicamycin, thapsigargin, and 2-deoxyglucose) and found that this treatment applied to SK-N-SH and HepG2 cells suppressed the expressional induction of 94kDa glucose regulated protein (GRP94) but not GRP78 proteins at both protein and mRNA levels. Although GRP94 mRNA increased, no significant difference was observed in the mRNA level of spliced X box binding protein 1 (XBP1) and reporter gene assay using GRP78 and GRP94 promoter with an ER stress response element (ERSE) showed that PKR inhibitor did not affect their activity. These results suggest that a novel mechanism other than ERSE-dependent mRNA transcription is required for the induction of GRP94 and phosphorylation of PKR contributes to the induction of GRP94 under ER stress.
authors.affiliation: Graduate School of Pharmaceutical Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 13-0033, Japan.
authors.forename: Mototsugu
authors.initials: M
authors.lastname: Ito
authors.forename: Reiko
authors.initials: R
authors.lastname: Onuki
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Bando
authors.forename: Masaya
authors.initials: M
authors.lastname: Tohyama
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Sugiyama
mesh_terms: D002460:Cell Line; D003847:Deoxyglucose / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008562:Membrane Glycoproteins / Q000096:biosynthesis* / Q000235:genetics; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D012333:RNA, Messenger / Q000096:biosynthesis; D020218:Response Elements; D019892:eIF-2 Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D000091342:Endoplasmic Reticulum Chaperone BiP; D004791:Enzyme Inhibitors; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D008562:Membrane Glycoproteins; D018832:Molecular Chaperones; D012333:RNA, Messenger; C053387:endoplasmin; D003847:Deoxyglucose; D019892:eIF-2 Kinase