title: Endoplasmic reticulum stress-induced cysteine protease activation in cortical neurons: effect of an Alzheimer's disease-linked presenilin-1 knock-in mutation.
abstract: Endoplasmic reticulum (ER) stress elicits protective responses of chaperone induction and translational suppression and, when unimpeded, leads to caspase-mediated apoptosis. Alzheimer's disease-linked mutations in presenilin-1 (PS-1) reportedly impair ER stress-mediated protective responses and enhance vulnerability to degeneration. We used cleavage site-specific antibodies to characterize the cysteine protease activation responses of primary mouse cortical neurons to ER stress and evaluate the influence of a PS-1 knock-in mutation on these and other stress responses. Two different ER stressors lead to processing of the ER-resident protease procaspase-12, activation of calpain, caspase-3, and caspase-6, and degradation of ER and non-ER protein substrates. Immunocytochemical localization of activated caspase-3 and a cleaved substrate of caspase-6 confirms that caspase activation extends into the cytosol and nucleus. ER stress-induced proteolysis is unchanged in cortical neurons derived from the PS-1 P264L knock-in mouse. Furthermore, the PS-1 genotype does not influence stress-induced increases in chaperones Grp78/BiP and Grp94 or apoptotic neurodegeneration. A similar lack of effect of the PS-1 P264L mutation on the activation of caspases and induction of chaperones is observed in fibroblasts. Finally, the PS-1 knock-in mutation does not alter activation of the protein kinase PKR-like ER kinase (PERK), a trigger for stress-induced translational suppression. These data demonstrate that ER stress in cortical neurons leads to activation of several cysteine proteases within diverse neuronal compartments and indicate that Alzheimer's disease-linked PS-1 mutations do not invariably alter the proteolytic, chaperone induction, translational suppression, and apoptotic responses to ER stress.
authors.affiliation: University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA. siman@pharm.med.upenn.edu
authors.forename: R
authors.initials: R
authors.lastname: Siman
authors.forename: D G
authors.initials: DG
authors.lastname: Flood
authors.forename: G
authors.initials: G
authors.lastname: Thinakaran
authors.forename: R W
authors.initials: RW
authors.lastname: Neumar
mesh_terms: D000544:Alzheimer Disease / Q000235:genetics; D000818:Animals; D017209:Apoptosis; D002154:Calpain / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D053454:Caspase 12; D053148:Caspase 3; D053178:Caspase 6; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000201:enzymology* / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D004789:Enzyme Activation; D006031:Glycosylation; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D018832:Molecular Chaperones / Q000378:metabolism; D009154:Mutation; D009474:Neurons / Q000378:metabolism; D053764:Presenilin-1; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013312:Stress, Physiological; D013347:Subcellular Fractions; D019892:eIF-2 Kinase / Q000378:metabolism
chemical_list: D002154:Calpain; D002352:Carrier Proteins; D053454:Caspase 12; D053148:Caspase 3; D053178:Caspase 6; D020169:Caspases; D003546:Cysteine Endopeptidases; D000091342:Endoplasmic Reticulum Chaperone BiP; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D018832:Molecular Chaperones; D053764:Presenilin-1; D019892:eIF-2 Kinase; C000717247:HSPA5 protein, human; C000717248:Hspa5 protein, mouse; C508853:PSEN1 protein, human; C018551:glucose-regulated proteins; C506444:CASP12 protein, human; C505407:CASP3 protein, human; C505514:CASP6 protein, human; C506440:Casp12 protein, mouse; C505409:Casp3 protein, mouse; C505516:Casp6 protein, mouse