ABCG2 p.Cys603Gly
| Predicted by SNAP2: | A: D (85%), D: D (95%), E: D (95%), F: D (95%), G: D (95%), H: D (95%), I: D (91%), K: D (95%), L: D (95%), M: D (95%), N: D (95%), P: D (95%), Q: D (95%), R: D (95%), S: D (91%), T: D (91%), V: D (95%), W: D (95%), Y: D (95%), |
| Predicted by PROVEAN: | A: D, D: D, E: D, F: D, G: 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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[hide] Role of Cys-603 in dimer/oligomer formation of the... Cancer Sci. 2005 Dec;96(12):866-72. Kage K, Fujita T, Sugimoto Y
Role of Cys-603 in dimer/oligomer formation of the breast cancer resistance protein BCRP/ABCG2.
Cancer Sci. 2005 Dec;96(12):866-72., [PMID:16367905]
Abstract [show]
Breast cancer resistance protein (BCRP/ABCG2) is a half-molecule ATP-binding cassette transporter that we have previously suggested might function as a homodimer, bridged by disulfide bonds. In the present study, we carried out cysteine-scanning mutagenesis, substituting Ser for Cys, and established 12 PA317 transfectants expressing BCRP mutants with possible disruptions to their S-S bonds. Western blot analysis of BCRP from the wild-type transfectants (PA/WT) confirmed that the wild-type protein migrates as a 140-kDa dimer under non-reducing conditions, but as a 70-kDa monomer under reducing conditions. However, under non-reducing conditions the BCRP-C603S mutant migrated both as a 70-kDa monomer and a 140-kDa dimer, whereas all other mutant BCRP migrated only as dimers. PA317 cells transfected with C603S-BCRP (PA/C603S) showed either similar or only marginally lower SN-38 resistance than PA/WT cells, despite the reduced levels of BCRP dimer in these cells. Moreover, the degree of SN-38 resistance in the mutant BCRP transfectants was found to be associated with the monomer expression levels under reducing conditions. Reverse transcription-polymerase chain reaction analysis showed that the BCRP mRNA levels were similar in the transfectants. We subsequently generated six C603X mutants of BCRP (X=D, H, R, Y, A and W) and carried out western blot analysis and drug sensitivity assays. The results were equivalent to those from the PA/C603S cells, with some variations that again corresponded to the monomer levels. Our findings suggest that Cys-603 is an important residue in the covalent bridge between BCRP monomers but that a functioning unit of BCRP may not necessarily require covalent linkages.
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No. Sentence Comment
91 Similar results were found for PA/ C603H, PA/C603R, PA/C603G and PA/C603W cells (data not shown).
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ABCG2 p.Cys603Gly 16367905:91:55
status: VERIFIED[hide] Human ABC transporter ABCG2 in xenobiotic protecti... Drug Metab Rev. 2006;38(3):371-91. Wakabayashi K, Tamura A, Saito H, Onishi Y, Ishikawa T
Human ABC transporter ABCG2 in xenobiotic protection and redox biology.
Drug Metab Rev. 2006;38(3):371-91., [PMID:16877258]
Abstract [show]
Human ATP-binding cassette (ABC) transporter ABCG2 (BCRP/MXR/ABCP) is regarded as a member of the phase III system of xenobiotic metabolism. This efflux pump is suggested to be responsible for protecting the body from toxic xenobiotics and for removing toxic metabolites. The aim of this review article is to address new aspects of ABCG2 related to redox biology, namely the posttranslational modification (intra- and intermolecular disulfide bond formation) of ABCG2 protein and the transport of porphyrin and chlorophyll metabolites, as well as the high-speed screening and QSAR analysis method to evaluate ABCG2-drug interactions.
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No. Sentence Comment
62 It is important to note that substitution of the amino acid at 603 from Cys to Gly disrupted the ability of homodimer formation.
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ABCG2 p.Cys603Gly 16877258:62:63
status: VERIFIED63 The C603G variant of ABCG2 was a monomer (Fig. 4A), which was unchanged even after reductive treatment with dithiothreitol (DTT) (Fig. 4B).
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ABCG2 p.Cys603Gly 16877258:63:4
status: VERIFIED76 The C603G variant was as active as the wild-type variant in terms of ATP-dependent methotrexate transport and drug resistance profiles to SN-38 and mitoxantrone.
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ABCG2 p.Cys603Gly 16877258:76:4
status: VERIFIED78 Immunoblot detection of ABCG2 (WT) as well as of C603G and C592G/C608G variants expressed in Flp-In-293 cells (A).
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ABCG2 p.Cys603Gly 16877258:78:49
status: VERIFIED80 The effect of DTT treatment on C603G and C592G/C608G variants expressed in Flp-In-293 cells (B).
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ABCG2 p.Cys603Gly 16877258:80:31
status: VERIFIED89 Furthermore, the C603G variant was observed in the plasma membrane.
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ABCG2 p.Cys603Gly 16877258:89:17
status: VERIFIED101 Moreover, the protein level of the C592G/ C603G/C608G variant in Flp-In-293 cells was extremely low (Wakabayashi et al., 2006).
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ABCG2 p.Cys603Gly 16877258:101:42
status: VERIFIED[hide] Interaction with the 5D3 monoclonal antibody is re... J Biol Chem. 2008 Sep 19;283(38):26059-70. Epub 2008 Jul 21. Ozvegy-Laczka C, Laczko R, Hegedus C, Litman T, Varady G, Goda K, Hegedus T, Dokholyan NV, Sorrentino BP, Varadi A, Sarkadi B
Interaction with the 5D3 monoclonal antibody is regulated by intramolecular rearrangements but not by covalent dimer formation of the human ABCG2 multidrug transporter.
J Biol Chem. 2008 Sep 19;283(38):26059-70. Epub 2008 Jul 21., 2008-09-19 [PMID:18644784]
Abstract [show]
Human ABCG2 is a plasma membrane glycoprotein working as a homodimer or homo-oligomer. The protein plays an important role in the protection/detoxification of various tissues and may also be responsible for the multidrug-resistant phenotype of cancer cells. In our previous study we found that the 5D3 monoclonal antibody shows a function-dependent reactivity to an extracellular epitope of the ABCG2 transporter. In the current experiments we have further characterized the 5D3-ABCG2 interaction. The effect of chemical cross-linking and the modulation of extracellular S-S bridges on the transporter function and 5D3 reactivity of ABCG2 were investigated in depth. We found that several protein cross-linkers greatly increased 5D3 labeling in ABCG2 expressing HEK cells; however, there was no correlation between covalent dimer formation, the inhibition of transport activity, and the increase in 5D3 binding. Dithiothreitol treatment, which reduced the extracellular S-S bridge-forming cysteines of ABCG2, had no effect on transport function but caused a significant decrease in 5D3 binding. When analyzing ABCG2 mutants carrying Cys-to-Ala changes in the extracellular loop, we found that the mutant C603A (lacking the intermolecular S-S bond) showed comparable transport activity and 5D3 reactivity to the wild-type ABCG2. However, disruption of the intramolecular S-S bridge (in C592A, C608A, or C592A/C608A mutants) in this loop abolished 5D3 binding, whereas the function of the protein was preserved. Based on these results and ab initio folding simulations, we propose a model for the large extracellular loop of the ABCG2 protein.
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No. Sentence Comment
28 Interestingly, mutation of Cys-603 to Ala, Gly, or Ser does not remarkably influence the expression and functionality of the transporter (9-11).
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ABCG2 p.Cys603Gly 18644784:28:27
status: VERIFIED[hide] Human ABC transporters ABCG2 (BCRP) and ABCG4. Xenobiotica. 2008 Jul;38(7-8):863-88. Koshiba S, An R, Saito H, Wakabayashi K, Tamura A, Ishikawa T
Human ABC transporters ABCG2 (BCRP) and ABCG4.
Xenobiotica. 2008 Jul;38(7-8):863-88., [PMID:18668433]
Abstract [show]
1. The human ABC transporter ABCG2 is regarded as a member of the phase III system for xenobiotic metabolism, and it has been suggested that this efflux pump is responsible for protecting the body from toxic xenobiotics and for removing metabolites. 2. This review paper will address the new aspects of ABCG2 in terms of post-translational modifications (i.e., disulfide bond formation, ubiquitination, and endoplasmic reticulum-associated degradation) of ABCG2 protein, high-speed screening, and quantitative structure-activity relationship (QSAR) analysis to evaluate ABCG2-drug interactions, and genetic polymorphisms potentially associated with photosensitivity. 3. In addition, new aspects of human ABCG4 and mouse Abcg4 are presented with respect to their molecular properties and potential physiological roles. Considering a high sequence similarity between ABCG1 and ABCG4, both Abcg4 and ABCG4 may be involved in the transport of cholesterol from neurons and astrocytes. Furthermore, high expression of the mouse Abcg4 protein in the testis implicates its involvement in transport of certain sex hormones.
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No. Sentence Comment
50 The C603G variant is as active as was the wild-type in terms of ATP-dependent methotrexate (MTX) transport and drug resistance profiles to SN-38 and MTX (Wakabayashi et al. 2006).
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ABCG2 p.Cys603Gly 18668433:50:4
status: VERIFIED51 Furthermore, the C603G variant was observed in the plasma membrane as was the wild-type (Wakabayashi et al. 2006).
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ABCG2 p.Cys603Gly 18668433:51:17
status: VERIFIED[hide] Quality control of human ABCG2 protein in the endo... Adv Drug Deliv Rev. 2009 Jan 31;61(1):66-72. Epub 2008 Dec 11. Wakabayashi-Nakao K, Tamura A, Furukawa T, Nakagawa H, Ishikawa T
Quality control of human ABCG2 protein in the endoplasmic reticulum: ubiquitination and proteasomal degradation.
Adv Drug Deliv Rev. 2009 Jan 31;61(1):66-72. Epub 2008 Dec 11., 2009-01-31 [PMID:19111842]
Abstract [show]
Human ATP-binding cassette (ABC) transporter ABCG2 (BCRP/MXR/ABCP) is a plasma membrane protein carrying intra- and inter-molecular disulfide bonds and an N-linked glycan. Both disulfide bond formation and N-glycosylation are critical check points determining the stability and degradation fate of ABCG2 protein in the endoplasmic reticulum (ER). Misfolded ABCG2 protein without those post-translational modifications is removed from the ER by retrotranslocation to the cytosol compartment, ubiquitination by ubiquitin ligase, and finally degradation by proteasomes. Certain non-synonymous SNP variants of ABCG2 undergo such ER-associated degradation (ERAD).
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No. Sentence Comment
886 The C603G variant was as active as was the wild type in terms of ATP-dependent MTX transport and profiles of drug resistance to SN-38 and mitoxantrone [4,7].
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ABCG2 p.Cys603Gly 19111842:886:4
status: NEW887 Furthermore, the C603G variant was observed in the plasma membrane [7].
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ABCG2 p.Cys603Gly 19111842:887:17
status: NEW892 Moreover, the protein level of the C592G/C603G/ C608G variant in Flp-In-293 cells was extremely low [7].
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ABCG2 p.Cys603Gly 19111842:892:41
status: NEW[hide] Human ABC transporter ABCG2 in cancer chemotherapy... J Exp Ther Oncol. 2009;8(1):5-24. Ishikawa T, Nakagawa H
Human ABC transporter ABCG2 in cancer chemotherapy and pharmacogenomics.
J Exp Ther Oncol. 2009;8(1):5-24., [PMID:19827267]
Abstract [show]
The ability of cancer cells to acquire resistance to multiple anticancer agents, termed multidrug resistance, is often mediated by overexpression of ATP-binding cassette (ABC) transporters that remove drugs out of the cell against a concentration gradient. ABCG2, or breast cancer resistance protein (BCRP), is an ABC transporter that has been the subject of intense study since its discovery a decade ago. While ABCG2 overexpression has been demonstrated in cancer cells after in vitro drug treatment, endogenous ABCG2 expression in certain cancers is considered as a reflection of the differentiated phenotype of the cell of origin and likely contributes to intrinsic drug resistance. Notably, ABCG2 is often expressed in stem cell populations, where it plays a critical role in cellular protection. ABCG2 exhibits a broad range of substrate specificity. New technologies of high-speed screening and quantitative structure-activity-relationship (QSAR) analysis have been developed to analyze the interactions of drugs with ABCG2. As ABCG2 reportedly transports porphyrins, its contribution to photodynamic therapy of human cancer is also implicated. Protein expression levels of ABCG2 in cancer cells are regulated by both transcriptional activation and protein degradation. The ABCG2 protein undergoes endosomal and/or ubiquitin-mediated proteasomal degradations. Furthermore, genetic polymorphisms in the ABCG2 gene are important factors in cancer chemotherapy to circumvent adverse effects and/or to enhance the efficacy of anticancer drugs. The present review article addresses recent advances in molecular pharmacology and pharmacogenomics of ABCG2 and provides novelideas to improve cancer chemotherapy.
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No. Sentence Comment
187 The C603G variant was as active as was the wild type in terms of ATP-dependent MTX transport and profiles of drug resistance to SN-38 and mitoxantrone (Mitomo et al., 2003; Wakabayashi et al., 2006a).
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ABCG2 p.Cys603Gly 19827267:187:4
status: VERIFIED[hide] Ubiquitin-mediated proteasomal degradation of ABC ... J Pharm Sci. 2011 Sep;100(9):3602-19. doi: 10.1002/jps.22615. Epub 2011 May 12. Nakagawa H, Toyoda Y, Wakabayashi-Nakao K, Tamaki H, Osumi M, Ishikawa T
Ubiquitin-mediated proteasomal degradation of ABC transporters: a new aspect of genetic polymorphisms and clinical impacts.
J Pharm Sci. 2011 Sep;100(9):3602-19. doi: 10.1002/jps.22615. Epub 2011 May 12., [PMID:21567408]
Abstract [show]
The interindividual variation in the rate of drug metabolism and disposition has been known for many years. Pharmacogenomics dealing with heredity and response to drugs is a part of science that attempts to explain variability of drug responses and to search for the genetic basis of such variations or differences. Genetic polymorphisms of drug metabolizing enzymes and drug transporters have been found to play a significant role in the patients' responses to medication. Accumulating evidence demonstrates that certain nonsynonymous polymorphisms have great impacts on the protein stability and degradation, as well as the function of drug metabolizing enzymes and transporters. The aim of this review article is to address a new aspect of protein quality control in the endoplasmic reticulum and to present examples regarding the impact of nonsynonymous single-nucleotide polymorphisms on the protein stability of thiopurine S-methyltransferase as well as ATP-binding cassette (ABC) transporters including ABCC4, cystic fibrosis transmembrane conductance regulator (CFTR, ABCC7), ABCC11, and ABCG2. Furthermore, we will discuss the molecular mechanisms underlying posttranslational modifications (intramolecular and intermolecular disulfide bond formation and N-linked glycosylation) and ubiquitin-mediated proteasomal degradation of ABCG2, one of the major drug transporter proteins in humans.
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No. Sentence Comment
92 In fact, substitution of either Cys592 or Cys608 to Gly resulted in a marked decrease in protein levels of ABCG2 in the plasma membrane of Flp-In-293 cells in vitro.77 Moreover, the C592G/ C603G/C608G variant, in which all of the three Cys residues were substituted to Gly, was expressed at an extremely low level.73 The reduced protein levels could not be ascribed to any instability of mRNA encoding those variants because the mRNA levels of ABCG2 WT and those variants were kept at equal levels by Flp-mediated chromosomal integration of one single copy of ABCG2 complementary DNA (cDNA).73 It is important to note that the C592G/C608G variant formed a homodimer, however its cellular localization was remarkably altered.
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ABCG2 p.Cys603Gly 21567408:92:189
status: NEW