title: Cellular localization and trafficking of the human ABCA1 transporter.
abstract: ABCA1, the ATP-binding cassette protein mutated in Tangier disease, mediates the efflux of excess cellular sterol to apoA-I and thereby the formation of high density lipoprotein. The intracellular localization and trafficking of ABCA1 was examined in stably and transiently transfected HeLa cells expressing a functional human ABCA1-green fluorescent protein (GFP) fusion protein. The fluorescent chimeric ABCA1 transporter was found to reside on the cell surface and on intracellular vesicles that include a novel subset of early endosomes, as well as late endosomes and lysosomes. Studies of the localization and trafficking of ABCA1-GFP in the presence of brefeldin A or monensin, agents known to block intracellular vesicular trafficking, as well as apoA-I-mediated cellular lipid efflux, showed that: (i) ABCA1 functions in lipid efflux at the cell surface, and (ii) delivery of ABCA1 to lysosomes for degradation may serve as a mechanism to modulate its surface expression. Time-lapse fluorescence microscopy revealed that ABCA1-GFP-containing early endosomes undergo fusion, fission, and tubulation and transiently interact with one another, late endocytic vesicles, and the cell surface. These studies establish a complex intracellular trafficking pathway for human ABCA1 that may play important roles in modulating ABCA1 transporter activity and cellular cholesterol homeostasis.
authors.affiliation: NHLBI, National Institutes of Health and the NIDDK, National Institutes of Health, Bethesda, Maryland 20892, USA. neufelde@mail.nih.gov
authors.forename: E B
authors.initials: EB
authors.lastname: Neufeld
authors.forename: A T
authors.initials: AT
authors.lastname: Remaley
authors.forename: S J
authors.initials: SJ
authors.lastname: Demosky
authors.forename: J A
authors.initials: JA
authors.lastname: Stonik
authors.forename: A M
authors.initials: AM
authors.lastname: Cooney
authors.forename: M
authors.initials: M
authors.lastname: Comly
authors.forename: N K
authors.initials: NK
authors.lastname: Dwyer
authors.forename: M
authors.initials: M
authors.lastname: Zhang
authors.forename: J
authors.initials: J
authors.lastname: Blanchette-Mackie
authors.forename: S
authors.initials: S
authors.lastname: Santamarina-Fojo
authors.forename: H B
authors.initials: HB
authors.lastname: Brewer
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D016632:Apolipoprotein A-I / Q000378:metabolism; D001692:Biological Transport; D016466:CHO Cells; D002451:Cell Compartmentation; D006224:Cricetinae; D003513:Cycloheximide / Q000494:pharmacology; D004705:Endocytosis; D049452:Green Fluorescent Proteins; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D008164:Luminescent Proteins / Q000235:genetics; D008985:Monensin / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000235:genetics; D013261:Sterols / Q000378:metabolism; D014162:Transfection
chemical_list: C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D016632:Apolipoprotein A-I; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D013261:Sterols; D049452:Green Fluorescent Proteins; D008985:Monensin; D003513:Cycloheximide