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)

Multidrug transporters are membrane proteins that are able to expel a broad range of toxic molecules from the cell. In humans, the overexpression of the multidrug resistance P-glycoprotein (Pgp) and the multidrug resistance-associated protein MRP1 (MRP) is a principal cause of resistance of cancers to chemotherapy. These multidrug transporters belong to the ATP-binding cassette (ABC) family of transport proteins that utilize the energy of ATP hydrolysis for activity. In microorganisms, multidrug transporters play an important role in conferring antibiotic resistance on pathogens. In the last decade, homologs of human Pgp and MRP have been found in microorganisms such as Plasmodium falciparum, Candida albicans, Saccharomyces cerevisiae and, more recently, in Lactococcus lactis. In this review, we will summarize the current state of knowledge on three major aspects of microbial ABC-type multidrug transporters: (i) the functional and structural similarities among these proteins in prokaryotic and eukaryotic cells, (ii) the molecular mechanism of these transporters, and (iii) their potential physiological role.
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PMID:The ABC family of multidrug transporters in microorganisms. 969 18

Kaposi's sarcoma (KS) is considered a disorder of cytokines. Basic fibroblast growth factor (bFGF) is produced by AIDS-associated KS (AIDS-KS) cells and supports their growth in an autocrine and paracrine manner. bFGF lacks a signal sequence; therefore, its mechanism of secretion is unclear. In this study, we investigate the role of two important members of ATP-binding cassette transport proteins, the P-glycoprotein (P-gp) and multidrug resistance-associated protein (MRP), in the secretion of bFGF from AIDS-KS cells. Expression of P-gp and MRP was examined at both the protein and the mRNA levels by flow cytometry and RT-PCR respectively. Intracellular and secreted bFGF was measured by ELISA. AIDS-KS cells expressed MRP at both the mRNA and the protein levels; however, no P-gp expression was detected at either the mRNA or the protein level. Probenecid, a putative inhibitor of MRP efflux function, in a concentration-dependent manner, inhibited bFGF secretion, with a concomitant increase in intracellular bFGF, demonstrating that probenecid blocks bFGF secretion without inhibiting its synthesis. In addition, probenecid induced apoptosis in AIDS-KS cells. AIDS-KS cells expressed fas, bcl-2, and bcl-xL genes but lacked fasL and bax gene expression. These data suggest that bFGF is secreted from AIDS-KS cells via a probencid-sensitive transporter, most likely in MRP. Furthermore, probenecid appears to induce apoptosis in AIDS-KS cells by depriving them of the growth promoting activity of bFGF. These data suggest that MRP may play a role as a survival molecule in AIDS-KS cells.
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PMID:A possible role of multidrug resistance-associated protein (MRP) in basic fibroblast growth factor secretion by AIDS-associated Kaposi's sarcoma cells: a survival molecule? 971 Jul 42

ATP-binding cassette (ABC), ATP-dependent transporters are a large superfamily of proteins that include the multidrug resistance proteins, P-glycoprotein and MRP (multidrug resistance protein). The ARA (anthracycline resistance-associated) gene that codes for a putative member of the ABC transporters has recently been cloned and shown to have high sequence homology to the gene for MRP. We have previously shown MRP to be deleted in a subset of inv(16) leukemic patients. The deletion of MRP was associated with an improved patient survival compared with inv(16) patients who did not have such a deletion. In this study, the ARA gene is mapped to 16p13.1, in the same physical interval as the inv(16) short-arm breakpoint. It is shown to be situated proximal to both MYH11, the gene involved in the primary breakpoint on the short arm of the inv(16), and MRP. A YAC clone has been isolated containing both MRP and ARA. FISH analysis of metaphase chromosomes from inv(16) patients has established the gene order as telomere-MYH11-MRP-ARA-centromere and demonstrated that both ARA and MRP are deleted in a subgroup of the inv(16) leukemias. ARA and MRP are both shown to be expressed in normal hematopoietic precursors including CD34(+) cells. The mapping of ARA to this region and its homology to MRP raises questions about its potential role in the biology of the inv(16) leukemias.
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PMID:ARA, a novel ABC transporter, is located at 16p13.1, is deleted in inv(16) leukemias, and is shown to be expressed in primitive hematopoietic precursors. 972 Dec 17

Demethylation inhibitor (DMI)-resistant strains of the plant pathogenic fungus Penicillium digitatum were shown to be simultaneously resistant to cycloheximide, 4-nitroquinoline-N-oxide (4NQO), and acriflavine. A PMR1 (Penicillium multidrug resistance) gene encoding an ATP-binding cassette (ABC) transporter (P-glycoprotein) was cloned from a genomic DNA library of a DMI-resistant strain (LC2) of Penicillium digitatum by heterologous hybridization with a DNA fragment containing an ABC-encoding region from Botrytis cinerea. Sequence analysis revealed significant amino acid homology to the primary structures of PMR1 (protein encoded by the PMR1 gene) and ABC transporters of Saccharomyces cerevisiae (PDR5 and SNQ2), Schizosaccharomyces pombe (HBA2), Candida albicans (CDR1), and Aspergillus nidulans (AtrA and AtrB). Disruption of the PMR1 gene of P. digitatum DMI-resistant strain LC2 demonstrated that PMR1 was an important determinant of resistance to DMIs. The effective concentrations inhibiting radial growth by 50% (EC50s) and the MICs of fenarimol and bitertanol for the PMR1 disruptants (Deltapmr1 mutants) were equivalent to those for DMI-sensitive strains. Northern blot analysis indicated that severalfold more PMR1 transcript accumulated in the DMI-resistant strains compared with those in DMI-sensitive strains in the absence of fungicide. In both DMI-resistant and -sensitive strains, transcription of PMR1 was strongly enhanced within 10 min after treatment with the DMI fungicide triflumizole. These results suggested that the toxicant efflux system comprised of PMR1 participates directly in the DMI resistance of the fungus.
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PMID:A novel ATP-binding cassette transporter involved in multidrug resistance in the phytopathogenic fungus Penicillium digitatum. 975 30

Resistance to multiple natural product drugs associated with reduced drug accumulation in human tumor cells may be conferred by either the 170 kDa P-glycoprotein or the 190 kDa multidrug resistance protein, MRP. Both MRP and P-glycoprotein belong to the large and ancient ATP-binding cassette (ABC) superfamily of transport proteins but share only 15% amino acid identify. Unlike P-glycoprotein, MRP actively transports conjugated organic anions such as the cysteinyl leukotriene C4 and glutathione-conjugated aflatoxin B1. Transport of unconjugated chemotherapeutic agents appears to require cotransport of glutathione. MRP and several more recently discovered ABC proteins contain an additional NH2-proximal membrane-spanning domain not found in previously characterized ABC transporters. This domain, whose NH2-terminus is extracytosolic, is essential for MRP-mediated transport activity. This review summarizes current knowledge of the structural and transport characteristics of MRP which suggest that the physiologic functions of this protein could range from a protective role in chemical toxicity and oxidative stress to mediation of inflammatory responses involving cysteinyl leukotrienes.
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PMID:Multidrug resistance mediated by the ATP-binding cassette transporter protein MRP. 987 59

Many membrane proteins that belong to the ATP-binding cassette (ABC) superfamily are clinically important, including the cystic fibrosis transmembrane conductance regulator, the sulphonylurea receptor and P-glycoprotein (multidrug resistance gene product; MDR1). These proteins contain two multispanning transmembrane domains, each followed by one nucleotide-binding domain (NBD) and a linker region distal to the first NBD. ATP hydrolysis by the NBDs is critical for ABC protein function; the linker region seems to have a regulatory role. Previous attempts to express soluble NBDs and/or linker regions without detergent solubilization, or to purify NBDs at high yields as soluble fusion proteins, have been unsuccessful. Here we present a system for the expression in Escherichia coli of the first NBD of MDR1 followed by its linker region (NBD1MLD). A comparison of the expressions of NBD1MLD fused to glutathione S-transferase, thioredoxin and maltose-binding protein (MBP) shows that a high level of expression in the soluble fraction (approx. 8% of total E. coli protein) can be achieved only for MBP-NBD1MLD. The addition of a proteolytic thrombin site just proximal to the N-terminal end of NBD1MLD allows the cleavage of NBD1MLD from MBP, which can be easily purified with retention of its ATPase activity. In summary, success was obtained only when using an MBP fusion protein vector containing a thrombin proteolytic site between MBP and NBD1MLD. The approach described here could be generally applicable to solving the problems of expression and purification of NBDs/linker regions of ABC proteins.
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PMID:Expression and purification of the first nucleotide-binding domain and linker region of human multidrug resistance gene product: comparison of fusions to glutathione S-transferase, thioredoxin and maltose-binding protein. 993 1

Several proteins belonging to the ATP-binding cassette superfamily can affect ion channel function. These include the cystic fibrosis transmembrane conductance regulator, the sulfonylurea receptor, and the multidrug resistance protein P-glycoprotein (MDR1). We measured whole cell swelling-activated Cl- currents (ICl,swell) in parental cells and cells expressing wild-type MDR1 or a phosphorylation-defective mutant (Ser-661, Ser-667, and Ser-671 replaced by Ala). Stimulation of protein kinase C (PKC) with a phorbol ester reduced the rate of increase in ICl,swell only in cells that express MDR1. PKC stimulation had no effect on steady-state ICl,swell. Stimulation of protein kinase A (PKA) with 8-bromoadenosine 3',5'-cyclic monophosphate reduced steady-state ICl, swell only in MDR1-expressing cells. PKA stimulation had no effect on the rate of ICl,swell activation. The effects of stimulation of PKA and PKC on ICl,swell were additive (i.e., decrease in the rate of activation and reduction in steady-state ICl,swell). The effects of PKA and PKC stimulation were absent in cells expressing the phosphorylation-defective mutant. In summary, it is likely that phosphorylation of MDR1 by PKA and by PKC alters swelling-activated Cl- channels by independent mechanisms and that Ser-661, Ser-667, and Ser-671 are involved in the responses of ICl,swell to stimulation of PKA and PKC. These results support the notion that MDR1 phosphorylation affects ICl,swell.
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PMID:Phosphorylation of P-glycoprotein by PKA and PKC modulates swelling-activated Cl- currents. 995 Jul 64

Sister of P-glycoprotein (spgp) is a gene that is closely related to the P-glycoprotein family (Pgps). This class of proteins belongs to the superfamily of ATP-binding cassette transporters and is known for its involvement in pharmacological drug interactions. Therefore, this study investigated the distribution of spgp expression in different tissues known for their high levels of Pgps expression such as brain, liver, kidney, small- and large-gut mucosa. Analysis was done by using the reverse transcription-polymerase chain reaction. In addition to a high expression in the liver, we were able to demonstrate a significant spgp expression in brain grey cortex, small- and large-gut mucosa. Although Pgps are expressed in the kidney and brain capillary endothelial cells, no expression of spgp was detected in these tissues, which might indicate that spgp has no function in the blood-brain barrier and is not involved in the renal excretion of drugs.
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PMID:Sister of P-glycoprotein expression in different tissues. 1007 89

Bile secretion in liver is driven in large part by ATP-binding cassette (ABC)-type proteins that reside in the canalicular membrane and effect ATP-dependent transport of bile acids, phospholipids, and non-bile acid organic anions. Canalicular ABC-type proteins can be classified into two subfamilies based on membrane topology and sequence identity: MDR1, MDR3, and SPGP resemble the multidrug resistance (MDR) P-glycoprotein, whereas MRP2 is similar in structure and sequence to the multidrug resistance protein MRP1 and transports similar substrates. We now report the isolation of the rMRP3 gene from rat liver, which codes for a protein 1522 amino acids in length that exhibits extensive sequence similarity with MRP1 and MRP2. Northern blot analyses indicate that rMRP3 is expressed in lung and intestine of Sprague-Dawley rats as well as in liver of Eisai hyperbilirubinemic rats and TR- mutant rats, which are deficient in MRP2 expression. rMRP3 expression is also transiently induced in liver shortly after birth and during obstructive cholestasis. Antibodies raised against MRP3 recognize a polypeptide of 190-200 kDa, which is reduced in size to 155-165 kDa after treatment with endoglycosidases. Immunoblot analysis and immunoconfocal microscopy indicate that rMRP3 is present in the canalicular membrane, suggesting that it may play a role in bile formation.
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PMID:MRP3, a new ATP-binding cassette protein localized to the canalicular domain of the hepatocyte. 1036 53

Multidrug resistance-associated protein gene MRP/MRP1, and its family genes, including MRP2/cMOAT, have been isolated and characterized. These ATP-binding cassette (ABC) superfamily transporter genes are differentially expressed in various normal tissues and multidrug-resistant cell lines. Transfection of MRP/MRP1 and MRP2/cMOAT cDNA confers drug resistance on different spectra of anticancer agents from that of MDR1 coding P-glycoprotein. Although it remains unclear how MRP/MRP1 and related family genes are specifically involved in drug resistance in clinical cancers, current knowledge of the MRP subfamily suggests the importance of this class of transporters as a molecular target for drug sensitivity to anticancer agents.
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PMID:Multidrug resistance-associated protein subfamily transporters and drug resistance. 1040 39


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