title: Amyloid-β peptide-induced secretion of endoplasmic reticulum chaperone glycoprotein GRP94.
abstract: Amyloid-β (Aβ) peptide-induced neurotoxicity is typically associated with cell death through mechanisms not entirely understood. Here, we investigated stress signaling events triggered by soluble Aβ in differentiated rat neuronal-like PC12 cells. Morphologic evaluation of apoptosis confirmed that Aβ induced nuclear fragmentation that was prevented by pre-treatment with the antiapoptotic bile acid tauroursodeoxycholic acid (TUDCA). In addition, Aβ exposure triggered an early signaling response by the endoplasmic reticulum (ER) and caspase-12-mediated apoptosis, which, however, was independent of the ER-stress pathway. Furthermore, ER stress markers, including GRP94, ATF-6α, CHOP, and eIF2α, were strongly downregulated by Aβ, independent of protein degradation, and partially restored by TUDCA. Calpain inhibition prevented caspase-12 activation and reduced levels of ATF-6α. Importantly, Aβ-induced GRP94 downregulation was related to protein secretion and partially rescued through inhibition of the secretory pathway by geldanamycin and brefeldin. In conclusion, we showed that the ER is a proximal stress sensor for soluble Aβ-induced toxicity, resulting in caspase-12 activation and cell death in PC12 neuronal cells. Moreover, ER chaperone GRP94 secretion was associated with Aβ-induced apoptotic signaling. These data provide new information linking apoptotic properties of Aβ peptide to distinct subcellular mechanisms of toxicity. Further characterization of this signaling pathway is likely to provide new perspectives for modulation of amyloid-induced apoptosis.
authors.affiliation: Research Institute for Medicines and Pharmaceutical Sciences, Faculty of Pharmacy, University of Lisbon, Lisbon, Portugal.
authors.forename: Ricardo J S
authors.initials: RJ
authors.lastname: Viana
authors.forename: Clifford J
authors.initials: CJ
authors.lastname: Steer
authors.forename: Cecília M P
authors.initials: CM
authors.lastname: Rodrigues
mesh_terms: D051702:Activating Transcription Factor 6 / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D020126:Brefeldin A / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D053454:Caspase 12 / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002756:Cholagogues and Choleretics / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000187:drug effects* / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation / Q000187:drug effects; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D007783:Lactones / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism*; D016716:PC12 Cells / Q000187:drug effects / Q000648:ultrastructure; D010446:Peptide Fragments / Q000494:pharmacology*; D051381:Rats; D012717:Sesquiterpenes / Q000494:pharmacology; D013655:Taurochenodeoxycholic Acid / Q000494:pharmacology; D051742:Transcription Factor CHOP / Q000378:metabolism
chemical_list: D051702:Activating Transcription Factor 6; D016229:Amyloid beta-Peptides; C497113:Atf6 protein, rat; D002756:Cholagogues and Choleretics; D004268:DNA-Binding Proteins; C497251:Ddit3 protein, rat; D004791:Enzyme Inhibitors; D018840:HSP70 Heat-Shock Proteins; D007783:Lactones; D008565:Membrane Proteins; D010446:Peptide Fragments; D012717:Sesquiterpenes; C074636:amyloid beta-protein (25-35); C018551:glucose-regulated proteins; D051742:Transcription Factor CHOP; D020126:Brefeldin A; D013655:Taurochenodeoxycholic Acid; C031655:ursodoxicoltaurine; C046319:thapsigargicin; D053454:Caspase 12; D002118:Calcium