title: Protein kinase A modulates the activity of a major human isoform of ABCG1.
abstract: ABCG1 is an ABC half-transporter that exports cholesterol from cells to HDL. This study set out to investigate differences in posttranslational processing of two human ABCG1 protein isoforms, termed ABCG1(+12) and ABCG1(-12), that differ by the presence or absence of a 12 amino acid peptide. ABCG1(+12) is expressed in human cells and tissues, but not in mice. We identified two protein kinase A (PKA) consensus sites in ABCG1(+12), absent from ABCG1(-12). Inhibition of PKA with either of two structurally unrelated inhibitors resulted in a dose-dependent increase in cholesterol export from cells expressing ABCG1(+12), whereas ABCG1(-12)-expressing cells were unaffected. This was associated with stabilization of the ABCG1(+12) protein, and ABCG1(+12)-S389 was necessary to mediate these effects. Mutation of this serine to aspartic acid, simulating a constitutively phosphorylated state, resulted in accelerated degradation of ABCG1(+12) and reduced cholesterol export. Engineering an equivalent PKA site into ABCG1(-12) rendered this isoform responsive to PKA inhibition, confirming the relevance of this sequence. Together, these results demonstrate an additional level of complexity to the posttranslational control of this human ABCG1 isoform that is absent from ABCG1(-12) and the murine ABCG1 homolog.
authors.affiliation: Faculty of Pharmacy, University of Sydney, Sydney, Australia. Electronic address: ingrid.gelissen@sydney.edu.au.
authors.forename: Ingrid C
authors.initials: IC
authors.lastname: Gelissen
authors.affiliation: Faculty of Pharmacy, University of Sydney, Sydney, Australia; School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia.
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Sharpe
authors.affiliation: Centre for Vascular Research, University of New South Wales, Sydney, Australia; Department of Haematology, Prince of Wales Hospital, Sydney, Australia.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Sandoval
authors.affiliation: Faculty of Pharmacy, University of Sydney, Sydney, Australia.
authors.forename: Geetha
authors.initials: G
authors.lastname: Rao
authors.affiliation: Centre for Vascular Research, University of New South Wales, Sydney, Australia; Department of Haematology, Prince of Wales Hospital, Sydney, Australia.
authors.forename: Maaike
authors.initials: M
authors.lastname: Kockx
authors.affiliation: Centre for Vascular Research, University of New South Wales, Sydney, Australia; Department of Haematology, Prince of Wales Hospital, Sydney, Australia; Department of Cardiology, Concord Repatriation General Hospital, Sydney, Australia.
authors.forename: Leonard
authors.initials: L
authors.lastname: Kritharides
authors.affiliation: Centre for Vascular Research, University of New South Wales, Sydney, Australia; Department of Haematology, Prince of Wales Hospital, Sydney, Australia.
authors.forename: Wendy
authors.initials: W
authors.lastname: Jessup
authors.affiliation: School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Brown
mesh_terms: D000070998:ATP Binding Cassette Transporter, Subfamily G, Member 1; D018528:ATP-Binding Cassette Transporters / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D016466:CHO Cells; D002470:Cell Survival; D002784:Cholesterol / Q000378:metabolism; D006224:Cricetinae; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D006801:Humans; D008264:Macrophages; D051379:Mice; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism
chemical_list: C419353:ABCG1 protein, human; D000070998:ATP Binding Cassette Transporter, Subfamily G, Member 1; D018528:ATP-Binding Cassette Transporters; D020033:Protein Isoforms; D012333:RNA, Messenger; D002784:Cholesterol; D017868:Cyclic AMP-Dependent Protein Kinases