title: β-COP as a Component of Transport Vesicles for HDL Apolipoprotein-Mediated Cholesterol Exocytosis.
abstract: OBJECTIVE
  HDL and its apolipoproteins protect against atherosclerotic disease partly by removing excess cholesterol from macrophage foam cells. But the underlying mechanisms of cholesterol clearance are still not well defined. We investigated roles of vesicle trafficking of coatomer β-COP in delivering cholesterol to the cell surface during apoA-1 and apoE-mediated lipid efflux from fibroblasts and THP-1 macrophages.
  
  
  METHODS
  shRNA knockout, confocal and electron microscopy and biochemical analysis were used to investigate the roles of β-COP in apolipoprotein-mediated cholesterol efflux in fibroblasts and THP-1 macrophages.
  
  
  RESULTS
  We showed that β-COP knockdown by lentiviral shRNA resulted in reduced apoA-1-mediated cholesterol efflux, while increased cholesterol accumulation and formation of larger vesicles were observed in THP-1 macrophages by laser scanning confocal microscopy. Immunogold electron microscopy showed that β-COP appeared on the membrane protrusion complexes and colocalized with apoA-1 or apoE during cholesterol efflux. This was associated with releasing heterogeneous sizes of small particles into the culture media of THP-1 macrophage. Western blotting also showed that apoA-1 promotes β-COP translocation to the cell membrane and secretion into culture media, in which a total of 17 proteins were identified by proteomics. Moreover, β-COP exclusively associated with human plasma HDL fractions.
  
  
  CONCLUSIONS
  ApoA-1 and apoE promoted transport vesicles consisting of β-COP and other candidate proteins to exocytose cholesterol, forming the protrusion complexes on cell surface, which were then released from the cell membrane as small particles to media.
authors.affiliation: Department of Biochemistry and Molecular Biology, Key Laboratory of Medical Molecular Diagnostics of Guangdong Province, Guangdong Medical University, Dongguan, Guangdong, 523808, China.
authors.forename: Weilie
authors.initials: W
authors.lastname: Ma
authors.affiliation: Department of Biochemistry and Molecular Biology, Key Laboratory of Medical Molecular Diagnostics of Guangdong Province, Guangdong Medical University, Dongguan, Guangdong, 523808, China.
authors.forename: Margarita
authors.initials: M
authors.lastname: Lin
authors.affiliation: Department of Biochemistry and Molecular Biology, Key Laboratory of Medical Molecular Diagnostics of Guangdong Province, Guangdong Medical University, Dongguan, Guangdong, 523808, China.
authors.forename: Hang
authors.initials: H
authors.lastname: Ding
authors.affiliation: Department of Biochemistry and Molecular Biology, Key Laboratory of Medical Molecular Diagnostics of Guangdong Province, Guangdong Medical University, Dongguan, Guangdong, 523808, China.
authors.forename: Guorong
authors.initials: G
authors.lastname: Lin
authors.affiliation: Department of Biochemistry and Molecular Biology, Key Laboratory of Medical Molecular Diagnostics of Guangdong Province, Guangdong Medical University, Dongguan, Guangdong, 523808, China.
authors.forename: Zhizhen
authors.initials: Z
authors.lastname: Zhang
mesh_terms: D016632:Apolipoprotein A-I / Q000502:physiology*; D001057:Apolipoproteins E / Q000502:physiology*; D015153:Blotting, Western; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D020756:Coatomer Protein / Q000502:physiology*; D005089:Exocytosis / Q000502:physiology*; D005347:Fibroblasts / Q000378:metabolism; D055786:Gene Knockout Techniques; D006801:Humans; D008264:Macrophages / Q000378:metabolism; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D034741:RNA, Small Interfering / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D022161:Transport Vesicles / Q000378:metabolism / Q000502:physiology*
chemical_list: D016632:Apolipoprotein A-I; D001057:Apolipoproteins E; D020756:Coatomer Protein; D034741:RNA, Small Interfering; D002784:Cholesterol