ABCG2 p.Asn557Arg
| Predicted by SNAP2: | A: D (91%), C: D (91%), D: D (95%), E: D (95%), F: D (95%), G: D (95%), H: D (95%), I: D (91%), K: D (95%), L: D (91%), M: D (91%), P: D (95%), Q: D (95%), R: D (95%), S: D (95%), T: D (91%), V: D (91%), W: D (95%), Y: D (91%), |
| Predicted by PROVEAN: | A: D, C: D, D: D, E: D, F: D, G: D, H: N, I: D, K: D, L: D, M: D, P: D, Q: D, R: D, S: D, T: D, V: D, W: D, Y: N, |
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[hide] Single amino acid substitutions in the transmembra... Int J Cancer. 2003 Dec 10;107(5):757-63. Miwa M, Tsukahara S, Ishikawa E, Asada S, Imai Y, Sugimoto Y
Single amino acid substitutions in the transmembrane domains of breast cancer resistance protein (BCRP) alter cross resistance patterns in transfectants.
Int J Cancer. 2003 Dec 10;107(5):757-63., 2003-12-10 [PMID:14566825]
Abstract [show]
Breast cancer resistance protein (BCRP) is a member of ATP-binding cassette transporters that has an N-terminal ATP binding domain and a C-terminal transmembrane domain (TM). Expression of wild-type BCRP confers resistance to multiple chemotherapeutic agents such as mitoxantrone, SN-38 and topotecan, but not to doxorubicin. We made 32 BCRP mutants with an amino acid substitution in the TMs (7 E446-mutants in TM2, 15 R482-mutants in TM3, 4 N557-mutants in TM5 and 6 H630-mutants in TM6) and examined the effect of the substitutions on cellular drug resistance. PA317 cells transfected with any one of the 7 E446-mutant BCRP cDNAs did not show drug resistance. Cells transfected with any one of the 13 R482X2-BCRP cDNAs (X2 = N, C, M, S, T, V, A, G, E, W, D, Q and H, but not Y and K) showed higher resistance to mitoxantrone and doxorubicin than the wild-type BCRP-transfected cells. Cells transfected with N557D-BCRP cDNA showed similar resistance to mitoxantrone but lower resistance to SN-38 than the wild-type BCRP-transfected cells. Cells transfected with N557E-, H630E- or H630L-BCRP cDNA showed similar degrees of resistance to mitoxantrone and SN-38. Estrone and fumitremorgin C reversed the drug resistance of cells transfected with R482-, N557- or H630-mutant BCRP cDNA. Cells transfected with R482G- or R482S-BCRP cDNA showed less intracellular accumulation of [3H]mitoxantrone than the wild-type BCRP-transfected cells. These results suggest that E446 in TM2, R482 in TM3, N557 in TM5 and H630 in TM6 play important roles in drug recognition of BCRP.
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No. Sentence Comment
49 Among PA/ N557X3, PA/N557R expressed little BCRP. Among PA/H630X4 transfectants, moderate BCRP expression was observed in PA/ H630E.
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ABCG2 p.Asn557Arg 14566825:49:21
status: VERIFIED112 Such transfectants include PA/E446D, PA/R486D, PA/R486K, PA/N557R, H630K and H630R.
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ABCG2 p.Asn557Arg 14566825:112:60
status: VERIFIED[hide] Absence of N-linked glycosylation does not affect ... Cancer Chemother Pharmacol. 2005 Oct;56(4):344-50. Epub 2005 May 5. Mohrmann K, van Eijndhoven MA, Schinkel AH, Schellens JH
Absence of N-linked glycosylation does not affect plasma membrane localization of breast cancer resistance protein (BCRP/ABCG2).
Cancer Chemother Pharmacol. 2005 Oct;56(4):344-50. Epub 2005 May 5., [PMID:15875186]
Abstract [show]
Breast cancer resistance protein (BCRP/ABCG2) is an ATP-binding cassette (ABC) multidrug transporter that confers resistance to various anticancer drugs like topotecan and mitoxantrone. To obtain more insight in its cellular functioning, we investigated phosphorylation and N-linked glycosylation of BCRP. In the epithelial Madin-Darby canine kidney (MDCK) cell line, we did not detect phosphorylation of BCRP, in contrast to MRP2, which was phosphorylated. In the ovarian carcinoma cell line T8 also no phosphorylated BCRP was detected. As BCRP in both lines effectively transports drugs, it appears that phosphorylation of BCRP (if it occurs at all) is not needed for drug transport. We further mutated the asparagine residues 418, 557 and 596 in three putative N-linked glycosylation motifs of BCRP to alanines. Mutant proteins were expressed in CHO9 and MDCKII cells by transient transfection and characterized by Western blot and immunofluorescence analysis. We found that only BCRP-N596A and a mutant with all three asparagines mutated (triple mutant) were not glycosylated anymore, indicating that only asparagine 596 is normally glycosylated. The mutation of asparagine 596 (or 418) had little effect on the subcellular localization of BCRP, indicating that N-linked glycosylation is not essential for routing to the plasma membrane. However, BCRP-N557A and the triple mutant were mainly localized intracellularly, probably in the endoplasmic reticulum, suggesting that this mutation disrupted proper routing of BCRP.
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166 However, expression of the mutant BCRP-N557R gave a low expression and the Western blot suggests that only one band was detected instead of the two bands in the other BCRP expressing cells in the same experiment.
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ABCG2 p.Asn557Arg 15875186:166:39
status: VERIFIED167 This suggests that the BCRP-N557R mutant also has a (partial) problem with its folding in the ER.
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ABCG2 p.Asn557Arg 15875186:167:28
status: VERIFIED170 The described difference in resistance of the BCRP-N557H, BCRP-N557D, BCRP-N557E and BCRP-N557R mutants could be partially due to a small difference in folding of BCRP next to a difference in affinity.
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ABCG2 p.Asn557Arg 15875186:170:90
status: VERIFIED