title: Lipid raft proteome reveals ATP synthase complex in the cell surface.
abstract: Since detergent-resistant lipid rafts are involved in pathogen invasion, cholesterol homeostasis, angiogenesis, neurodegenerative diseases and signal transduction, protein identification in the rafts could provide important information to study their function. Here, we analyzed detergent-resistant raft proteins isolated from rat liver by capillary liquid chromatography-tandem mass spectrometry. Out of 196 proteins identified, 32% belonged to the raft or plasma membrane, 24% to mitochondrial, 20% to microsomal, 7% to miscellaneous, and 17% are unknown proteins. For example, membrane-bound receptors, trimeric GTP-binding proteins, ATP-binding cassette transporters, and glycosylphosphatidylinositol-anchored proteins were identified in this analysis. Unexpectedly, there were many mitochondrial proteins, raising a new issue for the presence of mitochondrial rafts or the localization of mitochondrial proteins into plasma membrane rafts. We confirmed that ATP synthase alpha and beta were expressed on the surface of the plasma membrane in HepG2 hepatocytes by immunofluorescence, cell surface biotinylation, and cellular fractionation. They had two distinct biochemical properties, detergent insolubility and low density, suggesting that the ATP synthase complex might be located in plasma membrane rafts as well as in the mitochondria.
authors.affiliation: Graduate School of Life Sciences and Biotechnology, Korea University, Seoul, Korea.
authors.forename: Tae-Jung
authors.initials: TJ
authors.lastname: Bae
authors.forename: Min-Sik
authors.initials: MS
authors.lastname: Kim
authors.forename: Jun-Woo
authors.initials: JW
authors.lastname: Kim
authors.forename: Bong-Woo
authors.initials: BW
authors.lastname: Kim
authors.forename: Hyo-Jung
authors.initials: HJ
authors.lastname: Choo
authors.forename: Joong-Won
authors.initials: JW
authors.lastname: Lee
authors.forename: Ki-Bum
authors.initials: KB
authors.lastname: Kim
authors.forename: Chang Seok
authors.initials: CS
authors.lastname: Lee
authors.forename: Ji-Hyun
authors.initials: JH
authors.lastname: Kim
authors.forename: Sun Young
authors.initials: SY
authors.lastname: Chang
authors.forename: Chang-Yuil
authors.initials: CY
authors.lastname: Kang
authors.forename: Sang-Won
authors.initials: SW
authors.lastname: Lee
authors.forename: Song-Won
authors.initials: SW
authors.lastname: Lee
authors.forename: Young-Gyu
authors.initials: YG
authors.lastname: Ko
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D002853:Chromatography, Liquid; D045304:Cytochromes c; D008099:Liver / Q000378:metabolism; D008297:Male; D013058:Mass Spectrometry; D021962:Membrane Microdomains / Q000378:metabolism*; D008565:Membrane Proteins; D025261:Mitochondrial Proton-Translocating ATPases / Q000378:metabolism*; D008969:Molecular Sequence Data; D020543:Proteome / Q000378:metabolism*; D051381:Rats
chemical_list: D008565:Membrane Proteins; D020543:Proteome; C106354:flotillins; D045304:Cytochromes c; C497342:ATP synthase beta subunit, rat; D025261:Mitochondrial Proton-Translocating ATPases