ABCA1 Increases Extracellular ATP to Mediate Cholesterol Efflux to ApoA-I

FieldValue
dc.contributor.authorLee, Jee Yeon
dc.date.accessioned2012-01-10T17:39:13Z
dc.date.available2012-01-10T17:39:13Z
dc.date.created2012
dc.date.issued2012
dc.identifier.urihttp://hdl.handle.net/10393/20519
dc.identifier.urihttp://dx.doi.org/10.20381/ruor-5132
dc.description.abstractABCA1 is a key plasma membrane protein required for the efflux of cellular cholesterol to extracellular acceptors, particularly to apoA-I. This process is essential to maintain cholesterol homeostasis in the body. The detailed molecular mechanisms, however, are still insufficiently understood. Also, the molecular identity of ABCA1, i.e. channel, pump or flippase, remains unknown. In this study we analyzed the extracellular ATP levels in the medium of ABCA1-expressing BHK cells and RAW macrophages and compared them to the medium of relevant non-expressing cells. We found that the extracellular ATP concentrations are significantly elevated when cells express ABCA1. Importantly, a dysfunctional ABCA1 mutant (A937V), when expressed similarly as WT-ABCA1, is unable to raise extracellular ATP concentration. This suggests a causal relationship between functional ABCA1 and elevated extracellular ATP. To explore the physiological role of elevated extracellular ATP, we analyzed ABCA1-mediated cholesterol efflux under the conditions where extracellular ATP levels were modulated. We found that increasing extracellular ATP within the physiological range, i.e. < μM, promotes cholesterol efflux to apoA-I. On the other hand, removing extracellular ATP, either by adding apyrase to the medium or by expressing a plasma membrane bound ecto-nucleotidase CD39, abolishes cholesterol efflux to apoA-I. Based on these results we conclude that, through direct or indirect mechanisms, ABCA1 functions to raise ATP levels in the medium. This elevated extracellular ATP is required for ABCA1-mediated cholesterol efflux to apoA-I.
dc.language.isoen
dc.publisherUniversité d'Ottawa / University of Ottawa
dc.subjectABCA1
dc.subjectextracellular ATP
dc.subjectRAW macrophages
dc.subjectBHK cells
dc.subjectCD39
dc.subjectapyrase
dc.titleABCA1 Increases Extracellular ATP to Mediate Cholesterol Efflux to ApoA-I
dc.typeThesis
dc.faculty.departmentBiochimie, microbiologie et immunologie / Biochemistry, Microbiology and Immunology
dc.contributor.supervisorZha, Xiaohui
dc.embargo.termsimmediate
dc.degree.nameMSc
dc.degree.levelmasters
dc.degree.disciplineSciences / Science
thesis.degree.nameMSc
thesis.degree.levelMasters
thesis.degree.disciplineSciences / Science
uottawa.departmentBiochimie, microbiologie et immunologie / Biochemistry, Microbiology and Immunology
CollectionThèses, 2011 - // Theses, 2011 -

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