Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.3.44 (P-glycoprotein)
13,344 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The human multidrug resistance P-glycoprotein (P-gp, ABCB1) uses ATP to transport many structurally diverse compounds out of the cell. It is an ABC transporter with two nucleotide-binding domains (NBDs) and two transmembrane domains (TMDs). Recently, we showed that the "LSGGQ" motif in one NBD ((531)LSGGQ(535) in NBD1; (1176)LSGGQ(1180) in NBD2) is adjacent to the "Walker A" sequence ((1070)GSSGCGKS(1077) in NBD2; (427)GNSGCGKS(434) in NBD1) in the other NBD (Loo, T. W., Bartlett, M. C., and Clarke, D. M. (2002) J. Biol. Chem. 277, 41303-41306). Drug substrates can stimulate or inhibit the ATPase activity of P-gp. Here, we report the effect of drug binding on cross-linking between the LSGGQ signature and Walker A sites (Cys(431)(NBD1)/C1176C(NBD2) and Cys(1074)(NBD2)/L531C(NBD1), respectively). Seven drug substrates (calcein-AM, demecolcine, cis(Z)-flupentixol, verapamil, cyclosporin A, Hoechst 33342, and trans(E)-flupentixol) were tested for their effect on oxidative cross-linking. Substrates that stimulated the ATPase activity of P-gp (calcein-AM, demecolcine, cis(Z)-flupentixol, and verapamil) increased the rate of cross-linking between Cys(431)(NBD1-Walker A)/C1176C(NBD2-LSGGQ) and between Cys(1074)(NBD2-Walker A)/L531C(NBD1-LSGGQ) when compared with cross-linking in the absence of drug substrate. By contrast, substrates that inhibited ATPase activity (cyclosporin A, Hoechst 33342, and trans(E)-flupentixol) decreased the rate of cross-linking. These results indicate that interaction between the LSGGQ motifs and Walker A sites must be essential for coupling drug binding to ATP hydrolysis. Drug binding in the transmembrane domains can induce long range conformational changes in the NBDs, such that compounds that stimulate or inhibit ATPase activity must decrease and increase, respectively, the distance between the Walker A and LSGGQ sequences.
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PMID:Drug binding in human P-glycoprotein causes conformational changes in both nucleotide-binding domains. 1242 6

The family of adenosine triphosphate (ATP)-binding cassette (ABC) transporters is the largest gene family known. While some ABC transporters translocate single substances across membranes with high specificity, others transport a wide variety of different lipophilic compounds. They are responsible for many physiological processes and are also implicated in a number of diseases. The present review focuses on ABC transporter genes which are involved in ageing and age-related diseases. Expression of ABCB1 (MDR1, P-glycoprotein) increases with age in CD4(+) and CD8(+) T-lymphocytes indicating that P-glycoprotein may be involved in the secretion of cytokines, growth factors, and cytotoxic molecules. As T cells in aged individuals are hyporesponsive leading to a reduced immunodefence capability, a role of ABCB1 in age-related immunological processes is presumed. The ABCA1 (ABC1) gene product translocates intracellular cholesterol and phospholipids out of macrophages. Genetic aberrations in ABCA1 cause perturbations in lipoprotein metabolism and contribute to atherosclerosis. ABCA4 (ABCR) represents a retina-specific ABC transporter expressed in rod photoreceptor cells. The ABCA4 gene product translocates retinyl-derivatives. Mutations in the ABCA4 gene contribute to age-related macular degeneration. Polymorphisms in the sulfonylurea receptor gene (ABCC8, SUR1) are associated with non-insulin-dependent diabetes mellitus (NIDDM). Sulfonylureas inhibit potassium conductance and are used to treat NIDDM by stimulation of insulin secretion across ATP-sensitive potassium channels in pancreatic beta-cell membranes. Possible diagnostic and therapeutic implications of ABC transporters for age-related diseases are discussed.
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PMID:Adenosine triphosphate-binding cassette transporter genes in ageing and age-related diseases. 1243 93

A set of 79 previously mapped bean (Phaseolus vulgaris) genomic (Bng) clones were partially sequenced. BLAST database searches detected homologies between 59 of these clones and genes from a variety of plants, especially Arabidopsis thaliana. Some matches in the database to the Bng clones included a putative P-glycoprotein-ABC transporter from Arabidopsis, an early nodulin-binding protein (ENBPI) from Medicago truncatula, a lon-protease protein from spinach, a branched-chain amino-acid aminotransferase from Arabidopsis, and a vacuolar sorting receptor (BP-80) from Pisum sativum. Additional matches were found for genes involved in isoprenoid biosynthesis, sulfur metabolism, proline biosynthesis, and floral development. Sequence tagged site (STSs) were produced for 16 of the clones, 2 of which contain simple sequence repeats (SSRs). Polymorphisms were detected for six of the STSs.
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PMID:Identification of putative genes in bean (Phaseolus vulgaris) genomic (Bng) RFLP clones and their conversion to STSs. 1250 45

The heterodimeric peptide transporter TAP belongs to the ABC transporter family. Sequence comparisons with the P-glycoprotein and cystic fibrosis transmembrane conductance regulator and the functional properties of selective amino acids in these ABC transporters postulated that the glutamic acid at position 263 and the phenylalanine at position 265 of the TAP1 subunit could affect peptide transporter function. To define the role of both amino acids, TAP1 mutants containing a deletion or a substitution to alanine at position 263 or 265 were generated and stably expressed in murine and human TAP1(-/-) cells. The different TAP1 mutants were characterized in terms of expression and function of TAP, MHC class I surface expression, immune recognition, and species-specific differences. The phenotype of murine and human cells expressing human TAP1 mutants with a deletion or substitution of Glu(263) was comparable to that of TAP1(-/-) cells. In contrast, murine and human TAP1 mutant cells containing a deletion or mutation of Phe(265) of the TAP1 subunit exhibit wild-type TAP function. This was associated with high levels of MHC class I surface expression and recognition by specific CTL, which was comparable to that of wild-type TAP1-transfected control cells. Thus, biochemical and functional evidence is presented that the Glu(263) of the TAP1 protein, but not the Phe(265), is critical for proper TAP function.
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PMID:Impaired transporter associated with antigen processing (TAP) function attributable to a single amino acid alteration in the peptide TAP subunit TAP1. 1251 60

Alkaloids comprise one of the largest groups of plant secondary metabolites. Berberine, a benzylisoquinoline alkaloid, is preferentially accumulated in the rhizome of Coptis japonica, a ranunculaceous plant, whereas gene expression for berberine biosynthetic enzymes has been observed specifically in root tissues, which suggests that berberine synthesized in the root is transported to the rhizome, where there is high accumulation. We recently isolated a cDNA encoding a multidrug-resistance protein (MDR)-type ATP-binding cassette (ABC) transporter (Cjmdr1) from berberine-producing cultured C. japonica cells, which is highly expressed in the rhizome. Functional analysis of Cjmdr1 by using a Xenopus oocyte expression system showed that CjMDR1 transported berberine in an inward direction, resulting in a higher accumulation of berberine in Cjmdr1-injected oocytes than in the control. Typical inhibitors of ABC proteins, such as vanadate, nifedipine, and glibenclamide, as well as ATP depletion, clearly inhibited this CjMDR1-dependent berberine uptake, suggesting that CjMDR1 functioned as an ABC transporter. Conventional membrane separation methods showed that CjMDR1 was localized in the plasma membrane of C. japonica cells. In situ hybridization indicated that Cjmdr1 mRNA was expressed preferentially in xylem tissues of the rhizome. These findings strongly suggest that CjMDR1 is involved in the translocation of berberine from the root to the rhizome.
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PMID:Involvement of CjMDR1, a plant multidrug-resistance-type ATP-binding cassette protein, in alkaloid transport in Coptis japonica. 1252 52

The role of the adenosine triphosphate-binding cassette (ABC) superfamily of membrane transporters is well documented in tumor cell multidrug resistance. More recently, growing evidence of their influence on oral bioavailability, drug excretion rates, and drug-drug interaction potential at the intestinal level has stimulated much investigation. Our laboratory is interested in evaluating the apical (AP) ABC transporter P-glycoprotein (Pgp [mdr-1]) for its role in xenobiotic efflux at the intestinal level. We propagated Caco-2 cells in the presence of vinblastine (a cytotoxic, Pgp substrate) to promote transporter expression though selection. That is, the cell population expressing Pgp, or with the capacity to up-regulate Pgp expression, survived and expanded in the presence of vinblastine. We have used this selected cell line (Caco-2 VinB) to develop a fluorescent-based assay to study the chemical modulators of Pgp activity. Using the Caco-2 VinB cells, we have successfully demonstrated the differential potency of previously characterized Pgp inhibitors. In addition, we conducted a morphological evaluation of the two cell lines using transmission, scanning, and confocal microscopy. Both cell strains differentiated into highly functional, polarized columnar epithelium, although the vinblastine-selected cell line had lost the phenotypic diversity observed in native Caco-2 populations. Increased Pgp expression was noted in Caco-2 VinB cells compared with the native cell line on Western blot analysis, which was localized to the AP surface using confocal microscopy and functionally demonstrated using transport assays. We believe that the Caco2 VinB cell line is a versatile tool for application in pharmaceutical drug development.
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PMID:Characterization and application of a vinblastine-selected CACO-2 cell line for evaluation of p-glycoprotein. 1253 40

Cultured Thalictrum minus cells produce a benzylisoquinoline alkaloid, berberine, in the presence of benzyladenine, and excrete it into the culture medium. T. minus cells excluded berberine, even if berberine was exogenously added to the medium, without benzyladenine treatment. Similarly, T. minus cells excluded a heterocyclic dye (neutral red) and calcein AM, which is used as a fluorescent probe to detect the drug efflux pump activity by ABC transporters. The addition of several inhibitors of P-glycoprotein, a representative ABC transporter, induced the accumulation in of both berberine and calcein AM ATP-dependent manner. The expression of P-glycoprotein-like ABC transporter genes was also demonstrated. The involvement of ABC transporter in the secretion of berberine in T. minus cells is discussed.
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PMID:Thalictrum minus cell cultures and ABC-like transporter. 1262 Mar 61

Molecular modeling and simulation approaches have been use to generate a complete model of the prokaryotic ABC transporter MsbA from Escherichia coli, starting from the low-resolution structure-based Calpha trace (PDB code 1JSQ). MsbA is of some biomedical interest as it is homologous to mammalian transporters such as P-glycoprotein and TAP. The quality of the MsbA model is assessed using a combination of molecular dynamics simulations and static structural analysis. These results suggest that the approach adopted for MsbA may be of general utility for generating all atom models from low-resolution crystal structures of membrane proteins. Molecular dynamics simulations of the MsbA model inserted in a fully solvated octane slab (a membrane mimetic environment) reveal that while the monomer is relatively stable, the dimer is unstable and undergoes significant conformational drift on a nanosecond time scale. This suggests that the MsbA crystal dimer may not correspond to the MsbA dimer in vivo. An alternative model of the dimer is discussed in the context of available experimental data.
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PMID:Extending the structure of an ABC transporter to atomic resolution: modeling and simulation studies of MsbA. 1266 56

In our laboratories, we have been studying molecular targets which might be advantageous for novel cancer therapeutics. In this review, we focus on how ATP-binding cassette (ABC) transporter superfamily genes, Y-box-binding protein-1 (YB-1), and tumor angiogenesis-associated factors could contribute to the development of novel strategies for molecular cancer therapeutics. ABC transporters such as P-glycoprotein/MDR1 and several MRP family proteins function to protect cells from xenobiotics, drugs and poisons, suggesting that ABC transporters are a double-edged sword. In this regard, P-glycoprotein/MDR1 is a representative ABC transporter which plays a critical role in the efflux of a wide range of drugs. We have reported that gene amplification, gene rearrangements, transcription factor YB-1 and CpG methylation on the promoter are involved in MDR1 gene overexpression in cultured cancer cells. Among them, two mechanisms appear to be relevant to the up-regulation of MDR1 gene in human malignancies. We first reported that MDR1 gene promoter is activated in response to environmental stimuli, and is modulated by methylation/demethylation of CpG sites on the MDR1 promoter. We also demonstrated that YB-1 modulates not only transcription of various genes associated with cell growth, drug resistance and DNA synthesis, but also translation, mRNA stabilization and DNA repair/self-defense processes. Angiogenesis is also involved in tumor growth, invasion and metastasis of various malignancies, and so angiogenesis-related molecules also offer novel molecular targets for anticancer therapeutics.
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PMID:The basic and clinical implications of ABC transporters, Y-box-binding protein-1 (YB-1) and angiogenesis-related factors in human malignancies. 1270 67

ATP-binding cassette (ABC) genes play a role in the resistance of malignant cells to anticancer agents. The ABC gene products, including ABCB1 (P-glycoprotein), ABCC1 (MRP1), ABCC2 (MRP2, cMOAT), and ABCG2 (BCRP, MXR, ABCP) are also known to influence oral absorption and disposition of a wide variety of drugs. As a result, the expression levels of these proteins in humans have important consequences for an individual's susceptibility to certain drug-induced side effects, interactions, and treatment efficacy. Naturally occurring variants in ABC transporter genes have been identified that might affect the function and expression of the protein. This review focuses on recent advances in the pharmacogenomics of ABC transporters, and discusses potential implications of genetic variants for the chemotherapeutic treatment of cancer.
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PMID:Pharmacogenomics of ABC transporters and its role in cancer chemotherapy. 1272 5


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