title: The chaperone BiP/GRP78 binds to amyloid precursor protein and decreases Abeta40 and Abeta42 secretion.
abstract: Recent studies of cellular amyloid precursor protein (APP) metabolism demonstrate a beta-/gamma-secretase pathway resident to the endoplasmic reticulum (ER)/Golgi resulting in intracellular generation of soluble APP (APPsbeta) and Abeta42 peptide. Thus, these intracellular compartments may be key sites of amyloidogenic APP metabolism and Alzheimer's disease pathogenesis. We hypothesized that the ER chaperone immunoglobulin binding protein (BiP/GRP78) binds to and facilitates correct folding of nascent APP. Metabolic labeling and immunoprecipitation of transiently transfected human embryonic kidney 293 cells demonstrated co-precipitation of APP with GRP78, revealing their transient interaction in the ER. Maturation of cellular APP was impaired by this interaction. Furthermore, the levels of APPs, Abeta40, and Abeta42 recovered in conditioned medium were lower compared with cells transfected with APP alone. Co-expression with APP of GRP78 T37G, an ATPase mutant, almost completely blocked cellular APP maturation as well as recovery of APPs, Abeta40, and Abeta42 in conditioned medium. The inhibitory effects of GRP78 and GRP78 T37G on Abeta40 and Abeta42 secretion were magnified by co-expression with the Swedish mutation of APP (K670N/M671L). Collectively, these data suggest a transient and direct interaction of GRP78 with APP in the ER that modulates intracellular APP maturation and processing and may facilitate its correct folding.
authors.affiliation: Department of Neurology, University of Michigan Medical Center, and Veterans Affairs Medical Center Geriatric Research, Education and Clinical Center, Ann Arbor, Michigan 48109, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Yang
authors.forename: R S
authors.initials: RS
authors.lastname: Turner
authors.forename: J R
authors.initials: JR
authors.lastname: Gaut
mesh_terms: D000544:Alzheimer Disease / Q000503:physiopathology; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D017077:Culture Media, Conditioned / Q000737:chemistry; D004721:Endoplasmic Reticulum / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; D006801:Humans; D018832:Molecular Chaperones / Q000235:genetics / Q000502:physiology*; D009154:Mutation / Q000235:genetics; D010446:Peptide Fragments / Q000378:metabolism*; D011233:Precipitin Tests; D011485:Protein Binding; D017510:Protein Folding; D011499:Protein Processing, Post-Translational / Q000502:physiology; D014162:Transfection / Q000235:genetics
chemical_list: D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D002352:Carrier Proteins; D017077:Culture Media, Conditioned; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D010446:Peptide Fragments; C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42)