title: Regulated intramembrane proteolysis of the low-density lipoprotein receptor-related protein mediates ischemic cell death.
abstract: The low-density lipoprotein receptor-related protein (LRP), a member of the low-density lipoprotein receptor gene family, mediates cellular signal transduction pathways. In this study we investigated the role of LRP in cell death. We found that incubation of mouse embryonic fibroblasts in serum-free media induces caspase-3 activation, an effect that is attenuated in LRP-deficient (LRP(-/-)) mouse embryonic fibroblasts. Since we previously demonstrated that middle cerebral artery occlusion (MCAO) in mice induces shedding of the LRP ectodomain, we investigated here whether cerebral ischemia induces regulated intramembrane proteolysis of LRP and whether this process is related to cell death. We found that MCAO induces an increase in gamma-secretase activity in the ischemic hemisphere and that treatment with the gamma-secretase inhibitor L-685,458 improves the neurological outcome and results in a 50% decrease in the volume of the ischemic lesion. Furthermore, MCAO caused nuclear translocation of the intracellular domain of LRP in neurons within the area of ischemic penumbra, and this effect was attenuated in mice treated with L-685,458. Finally, inhibition of either LRP or gamma-secretase attenuated cerebral ischemia-induced caspase-3 cleavage and apoptotic cell death. In summary, our results indicate that gamma-secretase-mediated regulated intramembrane proteolysis of LRP results in cell death under ischemic conditions.
authors.affiliation: Department of Neurology and Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, GA 30322, USA.
authors.forename: Rohini
authors.initials: R
authors.lastname: Polavarapu
authors.forename: Jie
authors.initials: J
authors.lastname: An
authors.forename: Chen
authors.initials: C
authors.lastname: Zhang
authors.forename: Manuel
authors.initials: M
authors.lastname: Yepes
mesh_terms: D021581:Active Transport, Cell Nucleus; D053829:Amyloid Precursor Protein Secretases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000378:metabolism; D002545:Brain Ischemia / Q000209:etiology / Q000378:metabolism / Q000473:pathology*; D002219:Carbamates / Q000494:pharmacology; D053148:Caspase 3 / Q000378:metabolism; D016923:Cell Death; D002462:Cell Membrane / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D002544:Cerebral Infarction / Q000209:etiology / Q000378:metabolism / Q000473:pathology; D004151:Dipeptides / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D020244:Infarction, Middle Cerebral Artery / Q000150:complications / Q000378:metabolism / Q000473:pathology; D026503:Low Density Lipoprotein Receptor-Related Protein-1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D009474:Neurons / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D002219:Carbamates; D004151:Dipeptides; C410009:L 685458; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D053829:Amyloid Precursor Protein Secretases; D053148:Caspase 3