Characterization of the ATPase activity of human ATP-binding cassette transporter-2 (ABCA2).
BACKGROUND
ABCA2 is a member of the ATP binding cassette transporter family with functional roles in cholesterol homeostasis and drug resistance.


METHODS
In order to characterize its ATPase activity, we transfected HEK293 cells with an ABCA2 mammalian expression system and isolated ABCA2-enriched membranes.


RESULTS
We found no measurable ATPase activity of ABCA2 in isolated membranes, except in the presence of the methyl-beta-cyclodextrin. However, competitive binding of a pseudo-substrate, 8-azido-[alpha-32P]-ATP, was demonstrated. CHO cells transfected with ABCA2 did not have a higher rate of endogenous ATP hydrolysis when compared to the mock-transfected cells.


CONCLUSIONS
Overall, we conclude that, while ABCA2 may have low levels of ATPase activity that can be substrate-stimulated, it is more likely to have a regulatory role in cell physiology.
Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina, Charleston, SC 29425, USA.
Vladimir
V
Beljanski
Athena
A
Soulika
Jody M
JM
Tucker
Danyelle M
DM
Townsend
Warren
W
Davis
Kenneth D
KD
Tew
D016475:3T3 Cells / Q000187:drug effects / Q000201:enzymology; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D016466:CHO Cells / Q000187:drug effects / Q000201:enzymology; D003001:Cloning, Molecular; D006224:Cricetinae; D003412:Cricetulus; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D007425:Intracellular Membranes / Q000187:drug effects / Q000201:enzymology; D007527:Isoenzymes; D007668:Kidney / Q000187:drug effects / Q000196:embryology / Q000201:enzymology; D051379:Mice; D011817:Rabbits; D014162:Transfection; D047392:beta-Cyclodextrins / Q000494:pharmacology
C418186:ABCA2 protein, human; D018528:ATP-Binding Cassette Transporters; C498824:Abca2 protein, mouse; D007527:Isoenzymes; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; D000251:Adenosine Triphosphatases