title: S-palmitoylation of gamma-secretase subunits nicastrin and APH-1.
abstract: Proteolytic processing of amyloid precursor protein (APP) by beta- and gamma-secretases generates beta-amyloid (Abeta) peptides, which accumulate in the brains of individuals affected by Alzheimer disease. Detergent-resistant membrane microdomains (DRM) rich in cholesterol and sphingolipid, termed lipid rafts, have been implicated in Abeta production. Previously, we and others reported that the four integral subunits of the gamma-secretase associate with DRM. In this study we investigated the mechanisms underlying DRM association of gamma-secretase subunits. We report that in cultured cells and in brain the gamma-secretase subunits nicastrin and APH-1 undergo S-palmitoylation, the post-translational covalent attachment of the long chain fatty acid palmitate common in lipid raft-associated proteins. By mutagenesis we show that nicastrin is S-palmitoylated at Cys(689), and APH-1 is S-palmitoylated at Cys(182) and Cys(245). S-Palmitoylation-defective nicastrin and APH-1 form stable gamma-secretase complexes when expressed in knock-out fibroblasts lacking wild type subunits, suggesting that S-palmitoylation is not essential for gamma-secretase assembly. Nevertheless, fractionation studies show that S-palmitoylation contributes to DRM association of nicastrin and APH-1. Moreover, pulse-chase analyses reveal that S-palmitoylation is important for nascent polypeptide stability of both proteins. Co-expression of S-palmitoylation-deficient nicastrin and APH-1 in cultured cells neither affects Abeta40, Abeta42, and AICD production, nor intramembrane processing of Notch and N-cadherin. Our findings suggest that S-palmitoylation plays a role in stability and raft localization of nicastrin and APH-1, but does not directly modulate gamma-secretase processing of APP and other substrates.
authors.affiliation: Department of Neurobiology, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Haipeng
authors.initials: H
authors.lastname: Cheng
authors.forename: Kulandaivelu S
authors.initials: KS
authors.lastname: Vetrivel
authors.forename: Renaldo C
authors.initials: RC
authors.lastname: Drisdel
authors.forename: Xavier
authors.initials: X
authors.lastname: Meckler
authors.forename: Ping
authors.initials: P
authors.lastname: Gong
authors.forename: Jae Yoon
authors.initials: JY
authors.lastname: Leem
authors.forename: Tong
authors.initials: T
authors.lastname: Li
authors.forename: Meghan
authors.initials: M
authors.lastname: Carter
authors.forename: Ying
authors.initials: Y
authors.lastname: Chen
authors.forename: Phuong
authors.initials: P
authors.lastname: Nguyen
authors.forename: Takeshi
authors.initials: T
authors.lastname: Iwatsubo
authors.forename: Taisuke
authors.initials: T
authors.lastname: Tomita
authors.forename: Philip C
authors.initials: PC
authors.lastname: Wong
authors.forename: William N
authors.initials: WN
authors.lastname: Green
authors.forename: Maria Z
authors.initials: MZ
authors.lastname: Kounnas
authors.forename: Gopal
authors.initials: G
authors.lastname: Thinakaran
mesh_terms: D000544:Alzheimer Disease / Q000201:enzymology / Q000235:genetics; D053829:Amyloid Precursor Protein Secretases / Q000235:genetics / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000235:genetics / Q000378:metabolism; D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism; D016282:Aspartic Acid Endopeptidases / Q000235:genetics / Q000378:metabolism; D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D010450:Endopeptidases; D004795:Enzyme Stability / Q000502:physiology; D006801:Humans; D054878:Lipoylation / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D008563:Membrane Lipids / Q000235:genetics / Q000378:metabolism; D021962:Membrane Microdomains / Q000201:enzymology* / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D010447:Peptide Hydrolases; D011499:Protein Processing, Post-Translational / Q000502:physiology*; D051880:Receptors, Notch / Q000235:genetics / Q000378:metabolism
chemical_list: D016564:Amyloid beta-Protein Precursor; D015703:Antigens, CD; C050361:CDH2 protein, human; D015820:Cadherins; C489083:Cdh2 protein, mouse; D008562:Membrane Glycoproteins; D008563:Membrane Lipids; D008565:Membrane Proteins; D051880:Receptors, Notch; C413604:nicastrin protein; C475154:APH1A protein, human; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D010447:Peptide Hydrolases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human; C509282:Bace1 protein, mouse