title: Human macrophage cathepsin B-mediated C-terminal cleavage of apolipoprotein A-I at Ser228 severely impairs antiatherogenic capacity.
abstract: Apolipoprotein A-I (apoA-I) is the major component of HDL and central to the ability of HDL to stimulate ATP-binding cassette transporter A1 (ABCA1)-dependent, antiatherogenic export of cholesterol from macrophage foam cells, a key player in the pathology of atherosclerosis. Cell-mediated modifications of apoA-I, such as chlorination, nitration, oxidation, and proteolysis, can impair its antiatherogenic function, although it is unknown whether macrophages themselves contribute to such modifications. To investigate this, human monocyte-derived macrophages (HMDMs) were incubated with human apoA-I under conditions used to induce cholesterol export. Two-dimensional gel electrophoresis and Western blot analysis identified that apoA-I is cleaved (∼20-80%) by HMDMs in a time-dependent manner, generating apoA-I of lower MW and isoelectric point. Mass spectrometry analysis identified a novel C-terminal cleavage site of apoA-I between Ser228-Phe229Recombinant apoA-I truncated at Ser228demonstrated profound loss of capacity to solubilize lipid and to promote ABCA1-dependent cholesterol efflux. Protease inhibitors, small interfering RNA knockdown in HMDMs, mass spectrometry analysis, and cathepsin B activity assays identified secreted cathepsin B as responsible for apoA-I cleavage at Ser228Importantly, C-terminal cleavage of apoA-I was also detected in human carotid plaque. Cleavage at Ser228is a novel, functionally important post-translational modification of apoA-I mediated by HMDMs that limits the antiatherogenic properties of apoA-I.-Dinnes, D. L. M., White, M. Y., Kockx, M., Traini, M., Hsieh, V., Kim, M.-J., Hou, L., Jessup, W., Rye, K.-A., Thaysen-Andersen, M., Cordwell, S. J., Kritharides, L. Human macrophage cathepsin B-mediated C-terminal cleavage of apolipoprotein A-I at Ser228severely impairs antiatherogenic capacity.
authors.affiliation: Atherosclerosis Laboratory, ANZAC Research Institute, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Donna Lee M
authors.initials: DL
authors.lastname: Dinnes
authors.affiliation: School of Molecular Bioscience, Discipline of Pathology, School of Medical Sciences and Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Melanie Y
authors.initials: MY
authors.lastname: White
authors.affiliation: Atherosclerosis Laboratory, ANZAC Research Institute, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Maaike
authors.initials: M
authors.lastname: Kockx
authors.affiliation: Atherosclerosis Laboratory, ANZAC Research Institute, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Mathew
authors.initials: M
authors.lastname: Traini
authors.affiliation: Department of Cardiology, St. George Hospital, Sydney, New South Wales, Australia.
authors.forename: Victar
authors.initials: V
authors.lastname: Hsieh
authors.affiliation: School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Mi-Jurng
authors.initials: MJ
authors.lastname: Kim
authors.affiliation: Lipid Research Group, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Liming
authors.initials: L
authors.lastname: Hou
authors.affiliation: Atherosclerosis Laboratory, ANZAC Research Institute, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Wendy
authors.initials: W
authors.lastname: Jessup
authors.affiliation: Lipid Research Group, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Kerry-Anne
authors.initials: KA
authors.lastname: Rye
authors.affiliation: Department of Chemistry and Biomolecular Sciences, Faculty of Science and Engineering, Macquarie University, Sydney, New South Wales, Australia; and.
authors.forename: Morten
authors.initials: M
authors.lastname: Thaysen-Andersen
authors.affiliation: School of Molecular Bioscience, Discipline of Pathology, School of Medical Sciences and Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: Cordwell
authors.affiliation: Atherosclerosis Laboratory, ANZAC Research Institute, University of Sydney, Sydney, New South Wales, Australia; leonard.kritharides@sydney.edu.au.|Department of Cardiology, Concord Repatriation General Hospital, Sydney, New South Wales, Australia.
authors.forename: Leonard
authors.initials: L
authors.lastname: Kritharides
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D016632:Apolipoprotein A-I / Q000378:metabolism*; D050197:Atherosclerosis / Q000378:metabolism*; D001692:Biological Transport / Q000502:physiology; D002401:Cathepsin B / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism*; D005487:Foam Cells / Q000378:metabolism; D006801:Humans; D008264:Macrophages / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000502:physiology; D059748:Proteolysis; D012694:Serine / Q000378:metabolism
chemical_list: C505693:APOA1 protein, human; D018528:ATP-Binding Cassette Transporters; D016632:Apolipoprotein A-I; D012694:Serine; D002784:Cholesterol; D002401:Cathepsin B
keywords: atherosclerosis; coronary artery disease; high-density lipoprotein; proteolysis