title: Inhibition of calcineurin-mediated endocytosis and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors prevents amyloid beta oligomer-induced synaptic disruption.
abstract: Synaptic degeneration, including impairment of synaptic plasticity and loss of synapses, is an important feature of Alzheimer disease pathogenesis. Increasing evidence suggests that these degenerative synaptic changes are associated with an accumulation of soluble oligomeric assemblies of amyloid beta (Abeta) known as ADDLs. In primary hippocampal cultures ADDLs bind to a subpopulation of neurons. However the molecular basis of this cell type-selective interaction is not understood. Here, using siRNA screening technology, we identified alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits and calcineurin as candidate genes potentially involved in ADDL-neuron interactions. Immunocolocalization experiments confirmed that ADDL binding occurs in dendritic spines that express surface AMPA receptors, particularly the calcium-impermeable type II AMPA receptor subunit (GluR2). Pharmacological removal of the surface AMPA receptors or inhibition of AMPA receptors with antagonists reduces ADDL binding. Furthermore, using co-immunoprecipitation and photoreactive amino acid cross-linking, we found that ADDLs interact preferentially with GluR2-containing complexes. We demonstrate that calcineurin mediates an endocytotic process that is responsible for the rapid internalization of bound ADDLs along with surface AMPA receptor subunits, which then both colocalize with cpg2, a molecule localized specifically at the postsynaptic endocytic zone of excitatory synapses that plays an important role in activity-dependent glutamate receptor endocytosis. Both AMPA receptor and calcineurin inhibitors prevent oligomer-induced surface AMPAR and spine loss. These results support a model of disease pathogenesis in which Abeta oligomers interact selectively with neurotransmission pathways at excitatory synapses, resulting in synaptic loss via facilitated endocytosis. Validation of this model in human disease would identify therapeutic targets for Alzheimer disease.
authors.affiliation: Department of Neurology, Merck Research Laboratories, West Point, Pennsylvania 19486, USA. wei-qin_zhao@merck.com
authors.forename: Wei-Qin
authors.initials: WQ
authors.lastname: Zhao
authors.forename: Francesca
authors.initials: F
authors.lastname: Santini
authors.forename: Robert
authors.initials: R
authors.lastname: Breese
authors.forename: Dave
authors.initials: D
authors.lastname: Ross
authors.forename: Xiaohua Douglas
authors.initials: XD
authors.lastname: Zhang
authors.forename: David J
authors.initials: DJ
authors.lastname: Stone
authors.forename: Marc
authors.initials: M
authors.lastname: Ferrer
authors.forename: Matthew
authors.initials: M
authors.lastname: Townsend
authors.forename: Abigail L
authors.initials: AL
authors.lastname: Wolfe
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Seager
authors.forename: Gene G
authors.initials: GG
authors.lastname: Kinney
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Shughrue
authors.forename: William J
authors.initials: WJ
authors.lastname: Ray
mesh_terms: D016229:Amyloid beta-Peptides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D019703:Calcineurin / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D004705:Endocytosis / Q000502:physiology*; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D055503:Protein Multimerization; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism* / Q000473:pathology; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000378:metabolism
chemical_list: D016229:Amyloid beta-Peptides; D021122:Protein Subunits; D034741:RNA, Small Interfering; D018091:Receptors, AMPA; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D019703:Calcineurin; C104722:glutamate receptor ionotropic, AMPA 2