title: A genome wide analysis of ubiquitin ligases in APP processing identifies a novel regulator of BACE1 mRNA levels.
abstract: Proteolysis of beta-amyloid precursor protein (APP) into amyloid beta peptide (Abeta) by beta- and gamma-secretases is a critical step in the pathogenesis of Alzheimer's Disease (AD), but the pathways regulating secretases are not fully characterized. Ubiquitinylation, which is dysregulated in AD, may affect APP processing. Here, we describe a screen for APP processing modulators using an siRNA library targeting 532 predicted ubiquitin ligases. Seven siRNA pools diminished Abeta production. Of these, siRNAs targeting PPIL2 (hCyp-60) suppressed beta-site cleavage. Knockdown of PPIL2 mRNA decreased BACE1 mRNA, while overexpression of PPIL2 cDNA enhanced BACE1 mRNA levels. Microarray analysis of PPIL2 or BACE1 knockdown indicated that genes affected by BACE1 knockdown are a subset of those dependent upon PPIL2; suggesting that BACE1 expression is downstream of PPIL2. The association of PPIL2 with BACE expression and its requirement for Abeta production suggests new approaches to discover disease modifying agents for AD.
authors.affiliation: Department of Molecular and Cellular Technologies, Merck Research Laboratories, P.O. Box 4, West Point, PA 19486, USA.
authors.forename: Amy S
authors.initials: AS
authors.lastname: Espeseth
authors.forename: Qian
authors.initials: Q
authors.lastname: Huang
authors.forename: Adam
authors.initials: A
authors.lastname: Gates
authors.forename: Min
authors.initials: M
authors.lastname: Xu
authors.forename: Yuanjiang
authors.initials: Y
authors.lastname: Yu
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Simon
authors.forename: Xiao-Ping
authors.initials: XP
authors.lastname: Shi
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Zhang
authors.forename: Paul
authors.initials: P
authors.lastname: Hodor
authors.forename: David J
authors.initials: DJ
authors.lastname: Stone
authors.forename: Julja
authors.initials: J
authors.lastname: Burchard
authors.forename: Guy
authors.initials: G
authors.lastname: Cavet
authors.forename: Steven
authors.initials: S
authors.lastname: Bartz
authors.forename: Peter
authors.initials: P
authors.lastname: Linsley
authors.forename: William J
authors.initials: WJ
authors.lastname: Ray
authors.forename: Daria
authors.initials: D
authors.lastname: Hazuda
mesh_terms: D053829:Amyloid Precursor Protein Secretases / Q000235:genetics / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism*; D016282:Aspartic Acid Endopeptidases / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D021983:Cyclophilins / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression / Q000502:physiology; D016678:Genome / Q000502:physiology*; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D046228:Microarray Analysis / Q000379:methods; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D014162:Transfection / Q000379:methods; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D016564:Amyloid beta-Protein Precursor; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D008156:Luciferases; D044767:Ubiquitin-Protein Ligases; D053829:Amyloid Precursor Protein Secretases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human; D021983:Cyclophilins; C099773:PPIL2 protein, human