title: Astrocytic LRP1 Mediates Brain Aβ Clearance and Impacts Amyloid Deposition.
abstract: Accumulation and deposition of amyloid-β (Aβ) in the brain represent an early and perhaps necessary step in the pathogenesis of Alzheimer's disease (AD). Aβ accumulation leads to the formation of Aβ aggregates, which may directly and indirectly lead to eventual neurodegeneration. While Aβ production is accelerated in many familial forms of early-onset AD, increasing evidence indicates that impaired clearance of Aβ is more evident in late-onset AD. To uncover the mechanisms underlying impaired Aβ clearance in AD, we examined the role of low-density lipoprotein receptor-related protein 1 (LRP1) in astrocytes. Although LRP1 has been shown to play critical roles in brain Aβ metabolism in neurons and vascular mural cells, its role in astrocytes, the most abundant cell type in the brain responsible for maintaining neuronal homeostasis, remains unclear. Here, we show that astrocytic LRP1 plays a critical role in brain Aβ clearance. LRP1 knockdown in primary astrocytes resulted in decreased cellular Aβ uptake and degradation. In addition, silencing of LRP1 in astrocytes led to downregulation of several major Aβ-degrading enzymes, including matrix metalloproteases MMP2, MMP9, and insulin-degrading enzyme. More important, conditional knock-out of theLrp1gene in astrocytes in the background of APP/PS1 mice impaired brain Aβ clearance, exacerbated Aβ accumulation, and accelerated amyloid plaque deposition without affecting its production. Together, our results demonstrate that astrocytic LRP1 plays an important role in Aβ metabolism and that restoring LRP1 expression and function in the brain could be an effective strategy to facilitate Aβ clearance and counter amyloid pathology in AD.SIGNIFICANCE STATEMENTAstrocytes represent a major cell type regulating brain homeostasis; however, their roles in brain clearance of amyloid-β (Aβ) and underlying mechanism are not clear. In this study, we used both cellular models and conditional knock-out mouse models to address the role of a critical Aβ receptor, the low-density lipoprotein receptor-related protein 1 (LRP1) in astrocytes. We found that LRP1 in astrocytes plays a critical role in brain Aβ clearance by modulating several Aβ-degrading enzymes and cellular degradation pathways. Our results establish a critical role of astrocytic LRP1 in brain Aβ clearance and shed light on specific Aβ clearance pathways that may help to establish new targets for AD prevention and therapy.
authors.affiliation: Department of Neuroscience, Mayo Clinic, Jacksonville, Florida 32224, bu.guojun@mayo.edu liu.chiachen@mayo.edu.
authors.forename: Chia-Chen
authors.initials: CC
authors.lastname: Liu
authors.affiliation: Department of Neuroscience, Mayo Clinic, Jacksonville, Florida 32224.|Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, College of Medicine, Xiamen University, Xiamen, Fujian, 361102 China.
authors.forename: Jin
authors.initials: J
authors.lastname: Hu
authors.affiliation: Department of Neuroscience, Mayo Clinic, Jacksonville, Florida 32224.
authors.forename: Na
authors.initials: N
authors.lastname: Zhao
authors.affiliation: Department of Neuroscience, Mayo Clinic, Jacksonville, Florida 32224.
authors.forename: Jian
authors.identifier: 0000-0002-4166-5610
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Neuroscience, Mayo Clinic, Jacksonville, Florida 32224.|Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, College of Medicine, Xiamen University, Xiamen, Fujian, 361102 China.
authors.forename: Na
authors.initials: N
authors.lastname: Wang
authors.affiliation: Department of Neurology, Hope Center for Neurological Disorders, Knight Alzheimer's Disease Research Center, Washington University School of Medicine, St. Louis, Missouri 63110, and.
authors.forename: John R
authors.identifier: 0000-0002-7196-8786
authors.initials: JR
authors.lastname: Cirrito
authors.affiliation: Department of Neuroscience, Mayo Clinic, Jacksonville, Florida 32224.
authors.forename: Takahisa
authors.initials: T
authors.lastname: Kanekiyo
authors.affiliation: Department of Neurology, Hope Center for Neurological Disorders, Knight Alzheimer's Disease Research Center, Washington University School of Medicine, St. Louis, Missouri 63110, and.
authors.forename: David M
authors.initials: DM
authors.lastname: Holtzman
authors.affiliation: Department of Neuroscience, Mayo Clinic, Jacksonville, Florida 32224, bu.guojun@mayo.edu liu.chiachen@mayo.edu.|Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, College of Medicine, Xiamen University, Xiamen, Fujian, 361102 China.
authors.forename: Guojun
authors.initials: G
authors.lastname: Bu
mesh_terms: D016229:Amyloid beta-Peptides / Q000378:metabolism*; D000818:Animals; D001253:Astrocytes / Q000378:metabolism* / Q000473:pathology; D001921:Brain / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D010446:Peptide Fragments / Q000378:metabolism*; D058225:Plaque, Amyloid / Q000378:metabolism*; D011973:Receptors, LDL / Q000502:physiology*; D025521:Tumor Suppressor Proteins / Q000502:physiology*
chemical_list: D016229:Amyloid beta-Peptides; D026503:Low Density Lipoprotein Receptor-Related Protein-1; C486645:Lrp1 protein, mouse; D010446:Peptide Fragments; D011973:Receptors, LDL; D025521:Tumor Suppressor Proteins; C075222:amyloid beta-protein (1-42)
keywords: Alzheimer's disease; LRP1; amyloid-β