title: Neuronal clearance of amyloid-β by endocytic receptor LRP1.
abstract: Alzheimer's disease (AD) is the most prevalent form of dementia in the elderly population. Accumulation, aggregation, and deposition of amyloid-β (Aβ) peptides generated through proteolytic cleavage of amyloid precursor protein (APP) are likely initiating events in the pathogenesis of AD. While Aβ production is accelerated in familial AD, increasing evidence indicates that impaired clearance of Aβ is responsible for late-onset AD. Because Aβ is mainly generated in neurons, these cells are predicted to have the highest risk of encountering Aβ among all cell types in the brain. However, it is still unclear whether they are also involved in Aβ clearance. Here we show that receptor-mediated endocytosis in neurons by the low-density lipoprotein receptor-related protein 1 (LRP1) plays a critical role in brain Aβ clearance. LRP1 is known to be an endocytic receptor for multiple ligands including Aβ. Conditional knock-out of Lrp1 in mouse forebrain neurons leads to increased brain Aβ levels and exacerbated amyloid plaque deposition selectively in the cortex of amyloid model APP/PS1 mice without affecting Aβ production. In vivo microdialysis studies demonstrated that Aβ clearance in brain interstitial fluid is impaired in neuronal Lrp1 knock-out mice. Because the neuronal LRP1-deletion did not affect the mRNA levels of major Aβ degrading enzymes, neprilysin and insulin-degrading enzyme, the disturbed Aβ clearance is likely due to the suppression of LRP1-mediated neuronal Aβ uptake and degradation. Together, our results demonstrate that LRP1 plays an important role in receptor-mediated clearance of Aβ and indicate that neurons not only produce but also clear Aβ.
authors.affiliation: Department of Neuroscience, Mayo Clinic, Jacksonville, Florida 32224, Department of Neurology, Knight Alzheimer's Disease Research Center, and Hope Center for Neurological Disorders, Washington University, St. Louis, Missouri 63110, and Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, College of Medicine, Xiamen University, Xiamen 361005, China.
authors.forename: Takahisa
authors.initials: T
authors.lastname: Kanekiyo
authors.forename: John R
authors.initials: JR
authors.lastname: Cirrito
authors.forename: Chia-Chen
authors.initials: CC
authors.lastname: Liu
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Shinohara
authors.forename: Jie
authors.initials: J
authors.lastname: Li
authors.forename: Dorothy R
authors.initials: DR
authors.lastname: Schuler
authors.forename: Motoko
authors.initials: M
authors.lastname: Shinohara
authors.forename: David M
authors.initials: DM
authors.lastname: Holtzman
authors.forename: Guojun
authors.initials: G
authors.lastname: Bu
mesh_terms: D016229:Amyloid beta-Peptides / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D002540:Cerebral Cortex / Q000378:metabolism / Q000473:pathology; D004797:Enzyme-Linked Immunosorbent Assay; D006624:Hippocampus / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D051379:Mice; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D009474:Neurons / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D011973:Receptors, LDL / Q000378:metabolism*; D022161:Transport Vesicles / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
chemical_list: D016229:Amyloid beta-Peptides; D026503:Low Density Lipoprotein Receptor-Related Protein-1; C486645:Lrp1 protein, mouse; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D011973:Receptors, LDL; D025521:Tumor Suppressor Proteins