ABCMdb

ABCG1 p.Gly121Ala

Predicted by SNAP2:	A: D (91%), C: D (91%), D: D (95%), E: D (95%), F: D (95%), H: D (91%), I: D (95%), K: D (95%), L: D (95%), M: D (91%), N: D (91%), P: D (95%), Q: D (91%), R: D (95%), S: D (85%), T: D (91%), V: D (91%), W: D (95%), Y: D (95%),
Predicted by PROVEAN:	A: D, C: D, D: D, E: D, F: D, H: D, I: D, K: D, L: D, M: D, N: D, P: D, Q: D, R: D, S: D, T: D, V: D, W: D, Y: D,

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Publications
[hide] ABCG1 redistributes cell cholesterol to domains re... J Biol Chem. 2005 Aug 26;280(34):30150-7. Epub 2005 Jun 30. Vaughan AM, Oram JF
ABCG1 redistributes cell cholesterol to domains removable by high density lipoprotein but not by lipid-depleted apolipoproteins.
J Biol Chem. 2005 Aug 26;280(34):30150-7. Epub 2005 Jun 30., 2005-08-26 [PMID:15994327]

Abstract [show]
ATP binding cassette transporter G1 (ABCG1) mediates the transport of cholesterol from cells to high density lipoprotein (HDL) but not to lipid-depleted apolipoprotein A-I. Here we show that human ABCG1 overexpressed in baby hamster kidney cells in the absence of lipoproteins traffics to the plasma membrane and redistributes membrane cholesterol to cell-surface domains accessible to treatment with the enzyme cholesterol oxidase. Cholesterol removed by HDL was largely derived from these domains in ABCG1 transfectants but not in cells lacking ABCG1. Overexpression of ABCG1 also increased cholesterol esterification, which was decreased by the addition of HDL, suggesting that a proportion of the cell-surface cholesterol not removed by HDL is transported to the intracellular esterifying enzyme acyl-CoA:cholesterol acyltransferase. A 638-amino acid ABCG1, which lacked the 40 N-terminal amino acids of the predicted full-length protein, was fully functional and of a similar size to ABCG1 expressed by cholesterol-loaded human monocyte-derived macrophages. Mutating an essential glycine residue in the Walker A motif abolished ABCG1-dependent cholesterol efflux and esterification and prevented localization of ABCG1 to the cell surface, indicating that the ATP binding domain in ABCG1 is essential for both lipid transport activity and protein trafficking. These studies show that ABCG1 redistributes cholesterol to cell-surface domains where it becomes accessible for removal by HDL, consistent with a direct role of ABCG1 in cellular cholesterol transport.

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Sentences [show]
No. Sentence Comment
47 Site-directed mutagenesis of an amino acid residue common to all ABC transporter nucleotide binding domains (NCBI conserved domains data base, cd00267.1) (28) within the Walker A motif (29) of ABCG1 (glycine121 to alanine, GenBankTM accession number NP_004906) was carried out using the QuikChange XL site-directed mutagenesis kit (Stratagene, CA). Login to comment
140 The G121A mutation almost completely abolished the ability of ABCG1 to redistribute cholesterol to oxidase- and ACAT-accessible pools and to promote cholesterol efflux to HDL (Fig. 5D). Login to comment
160 There was no significant decrease in cholesterol content during the HDL incubation in the mock-transfected cells or in the ABCG1 G121A transfectants (Fig. 6C). Login to comment
181 C, equal amounts of cell protein from BHK cells transfected with FLAG-tagged wild type ABCG1 (WT) or a NBD ABCG1 mutant (G121A) were resolved by SDS-PAGE in the presence or absence of beta-mercaptoethanol (BME), and ABCG1 was detected by immunoblot analysis using an anti-FLAG antibody. Login to comment
185 *, p Ͻ 0.03 versus mock- or ABCG1-G121A-transfected cells. Login to comment
186 E, cell-surface (biotinylated) FLAG-tagged ABCG1 and ABCG1 G121A were detected by a streptavidin blotting assay following immunoprecipitation with an anti-FLAG antibody. Login to comment

[hide] Efflux of sphingomyelin, cholesterol, and phosphat... J Lipid Res. 2006 Aug;47(8):1791-802. Epub 2006 May 15. Kobayashi A, Takanezawa Y, Hirata T, Shimizu Y, Misasa K, Kioka N, Arai H, Ueda K, Matsuo M
Efflux of sphingomyelin, cholesterol, and phosphatidylcholine by ABCG1.
J Lipid Res. 2006 Aug;47(8):1791-802. Epub 2006 May 15., [PMID:16702602]

Abstract [show]
Cholesterol and phospholipids are essential to the body, but an excess of cholesterol or lipids is toxic and a risk factor for arteriosclerosis. ABCG1, one of the half-type ABC proteins, is thought to be involved in cholesterol homeostasis. To explore the role of ABCG1 in cholesterol homeostasis, we examined its subcellular localization and function. ABCG1 and ABCG1-K120M, a WalkerA lysine mutant, were localized to the plasma membrane in HEK293 cells stably expressing ABCG1 and formed a homodimer. A stable transformant expressing ABCG1 exhibited efflux of cholesterol and choline phospholipids in the presence of BSA, and the cholesterol efflux was enhanced by the presence of HDL, whereas cells expressing ABCG1-K120M did not, suggesting that ATP binding and/or hydrolysis is required for the efflux. Mass and TLC analyses revealed that ABCG1 and ABCA1 secrete several species of sphingomyelin (SM) and phosphatidylcholine (PC), and SMs were preferentially secreted by ABCG1, whereas PCs were preferentially secreted by ABCA1. These results suggest that ABCA1 and ABCG1 mediate the lipid efflux in different mechanisms, in which different species of phospholipids are secreted, and function coordinately in the removal of cholesterol and phospholipids from peripheral cells.

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Sentences [show]
No. Sentence Comment
250 It was reported that functional NBD is necessary for the trafficking of ABCG1 to the plasma membrane, because the G121A mutation within the WalkerA motif of ABCG1 abolished the cell surface expression (13). Login to comment
248 It was reported that functional NBD is necessary for the trafficking of ABCG1 to the plasma membrane, because the G121A mutation within the WalkerA motif of ABCG1 abolished the cell surface expression (13). Login to comment