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PubMed1998

In vivo characterization of the drug resistance profile of the major ABC transporters and other components of the yeast pleiotropic drug resistance network.

Multidrug resistance (MDR) mediated by broad specificity transporters is one of the most important strategies used by pathogens, including cancer cells, to evade chemotherapy. In the yeast Saccharomyces cerevisiae, a complex pleiotropic drug resistance (PDR) network of genes involved in MDR is composed of the transcriptional regulators Pdr1p and Pdr3p, which activate expression of the ATP-binding cassette (ABC) MDR transporters-encoding genes PDR5, SNQ2, and YOR1 as well as other not yet identified genes. We have screened 349 toxic compounds in isogenic S. cerevisiae strains deleted of PDRS, SNQ2, or YOR1 in different combinations as well as both PDR1 and PDR3. The screen revealed extremely promiscuous, yet limited, and to a large extent overlapping but distinct drug resistance profiles of Pdr5p, Snq2p, and Yor1p. These ABC-MDR transporters mediated resistance to most currently available classes of clinically and agriculturally important fungicides and also to many antibiotics, herbicides, and others. Several classes of compounds were identified for the first time in the drug resistance spectrum of MDR transporters. These are fungicides, such as anilinopyrimidines, benzimidazoles, benzenedicarbonitriles, dithiocarbamates, guanidines, imidothiazoles, polyenes, pyrimidynyl carbinols, and strobilurine analogues; the urea derivative and anilide herbicides; flavonoids, several membrane lipids resembling detergents; and newly synthesized lysosomotropic aminoesters; as well as many others. Identification of compounds showing Pdr1p, Pdr3p-dependent, but Pdr5p-, Snq2p-, and Yor1p-independent toxicity, reflected in the case of rhodamine 6G, by efflux alterations, suggests the involvement of new drug resistance genes and is a first step toward their identification. The highly increased toxicity of bile acids toward the PDR1, PDR3 double disruptant together with the decreased level of BAT1 promoter dependent beta-galactosidase activity suggest that the Bat1p ABC transporter is a new member of the PDR network. Our results may contribute to a better understanding of the mechanism of MDR, in particular in the pathogenic yeast Candida albicans. They also provide and indication of the physiological function of MDR transporters and suggest new approaches for the cloning of the mammalian bile acid transporters.

ATP-Binding Cassette Transporters↗

PubMed2004

Arabidopsis immunophilin-like TWD1 functionally interacts with vacuolar ABC transporters.

Previously, the immunophilin-like protein TWD1 from Arabidopsis has been demonstrated to interact with the ABC transporters AtPGP1 and its closest homologue, AtPGP19. Physiological and biochemical investigation of pgp1/pgp19 and of twd1 plants suggested a regulatory role of TWD1 on AtPGP1/AtPGP19 transport activities. To further understand the dramatic pleiotropic phenotype that is caused by loss-of-function mutation of the TWD1 gene, we were interested in other TWD1 interacting proteins. AtMRP1, a multidrug resistance-associated (MRP/ABCC)-like ABC transporter, has been isolated in a yeast two-hybrid screen. We demonstrate molecular interaction between TWD1 and ABC transporters AtMRP1 and its closest homologue, AtMRP2. Unlike AtPGP1, AtMRP1 binds to the C-terminal tetratricopeptide repeat domain of TWD1, which is well known to mediate protein-protein interactions. Domain mapping proved that TWD1 binds to a motif of AtMRP1 that resembles calmodulin-binding motifs; and calmodulin binding to the C-terminus of MRP1 was verified. By membrane fractionation and GFP-tagging, we localized AtMRP1 to the central vacuolar membrane and the TWD1-AtMRP1 complex was verified in vivo by coimmunoprecipitation. We were able to demonstrate that TWD1 binds to isolated vacuoles and has a significant impact on the uptake of metolachlor-GS and estradiol-beta-glucuronide, well-known substrates of vacuolar transporters AtMRP1 and AtMRP2.

ATP-Binding Cassette Transporters↗

PubMed1984

Immunoperoxidase demonstration of prostatic acid phosphatase in aspiration biopsy cytology (ABC).

The authors investigated the usefulness of immunoperoxidase demonstration of prostate-specific acid phosphatase (PAP) in determining the tissue of origin for carcinoma in aspiration biopsy cytology (ABC) specimens. Antisera from a commercial kit were applied using standard technics directly to Papanicoloau-stained slides. PAP was diffusely positive in numerous tumor cells of 27/28 moderately or poorly differentiated and 17/18 well-differentiated primary prostatic carcinomas. A negative result upon substituting the primary antiserum confirmed the reaction specificity in 18 cases with an additional available slide. PAP was demonstrable in corresponding histologic sections of 16/17 moderately or poorly differentiated and 18/18 well-differentiated carcinomas. Only 2 of 22 nonprostatic carcinomas (both of breast origin) showed very rare positive cells. Four ABC specimens of metastatic prostatic carcinoma were diffusely positive. Thus, diffuse staining of PAP by immunoperoxidase in tumor cells of ABC specimens gives high sensitivity and specificity for prostate as the tissue of origin.

Acid Phosphatase↗

PubMed1989

Sensitivity and detection efficiency of the peroxidase antiperoxidase (PAP), avidin-biotin peroxidase complex (ABC), and peroxidase-labeled avidin-biotin (LAB) methods.

The authors have examined the sensitivity and detection efficiency of the three peroxidase methods that currently have the widest application in diagnostic immunohistochemistry: the peroxidase-antiperoxidase (PAP), the avidin-biotin complex (ABC), and the labeled avidin-biotin (LAB) methods. Sensitivity was evaluated by determining the highest useful dilution of polyclonal antiglucagon antibodies applied to formalin-fixed, paraffin-embedded human pancreas. Detection efficiency was evaluated by tabulation of the total number of positive (three or more positive cells) islets. On direct comparison, the LAB method exceeded the PAP and ABC methods in both sensitivity and detection efficiency, which were essentially equal. Titration of linking antiserum of the PAP method boosted its sensitivity and detection efficiency above that of ABC; the PAP had equal sensitivity to the LAB and exceeded it in detection efficiency. The authors conclude that comparisons of immunohistologic methods are meaningful only if both sensitivity and efficiency are considered along with the unique requirements of any single method.

Avidin↗

PubMed2002

ABC transporters: one, two or four extracytoplasmic substrate-binding sites?

Two families of ATP-binding cassette (ABC) transporters in which one or two extracytoplasmic substrate-binding domains are fused to either the N- or C-terminus of the translocator protein have been detected. This suggests that two, or even four, substrate-binding sites may function in the ABC transporter complex. This domain organization in ABC transporters, widely represented among microorganisms, raises new possibilities for how the substrate-binding protein(s) (SBPs) might interact with the translocator. One appealing hypothesis is that multiple substrate-binding sites in proximity to the entry site of the translocation pore enhance the transport capacity. We also discuss the implications of multiple substrate-binding sites in close proximity to the translocator in terms of broadened substrate specificity and possible cooperative interactions between SBPs and the translocator.

ATP-Binding Cassette Transporters↗

PubMed2003

On the role of the two extracytoplasmic substrate-binding domains in the ABC transporter OpuA.

Members of two transporter families of the ATP-binding cassette (ABC) superfamily use two or even four extracytoplasmic substrate-binding domains (SBDs) for transport. We report on the role of the two SBDs in the translocation cycle of the ABC transporter OpuA from Lactococcus lactis. Heterooligomeric OpuA complexes with only one SBD or one functional and one non-functional SBD (inactivated by covalent linkage of a substrate mimic) have been constructed, and the substrate binding and transport kinetics of the purified transporters, reconstituted in liposomes, have been determined. The data indicate that the two SBDs of OpuA interact in a cooperative manner in the translocation process by stimulating either the docking of the SBDs onto the translocator or the delivery of glycine betaine to the translocator. It appears that one of these initial steps, but not the later steps in translocation or resetting of the system to the initial state, is rate determining for transport. These new insights on the functional role of the extracytoplasmic SBDs are discussed in the light of the current knowledge of substrate-binding-protein-dependent ABC transporters.

ATP-Binding Cassette Transporters↗

PubMed2002

IDI7, a new iron-regulated ABC transporter from barley roots, localizes to the tonoplast.

A new Fe-deficiency-induced cDNA, IDI7, was isolated from the roots of Fe-deficient barley (Hordeum vulgare L. cv. Ehimehadaka no. 1). The transcript levels of IDI7 in roots strongly correlated with iron nutritional status, and induction by Fe-deficiency was restricted to roots. Excess treatment with heavy metal ions, such as copper, manganese, and zinc, did not cause obvious IDI7 induction in either leaves or roots. IDI7 encodes a 644 amino acid protein, and has features typical of ATP-binding cassette (ABC) transporters. Phylogenetic analysis revealed that IDI7 is closely related to the half-type ABC protein subfamily, which includes mammalian transporters associated with antigen processing (TAPs). A transiently expressed fusion protein of IDI7 to green fluorescent protein (GFP) was localized to tonoplasts in suspension-cultured tobacco (Nicotiana tabacum L.) cells. IDI7 and its orthologues are thought to comprise a new class of ABC transporters, located in the tonoplasts of higher plants. A possible Fe-deficiency adaptation role for IDI7 in barley root cells, involving transport across the tonoplast, is proposed.

ATP-Binding Cassette Transporters↗

PubMed2002

Characterization of berberine transport into Coptis japonica cells and the involvement of ABC protein.

Cultured Coptis japonica cells are able to take up berberine, a benzylisoquinoline alkaloid, from the medium and transport it exclusively into the vacuoles. Uptake activity depends on the growth phase of the cultured cells whereas the culture medium had no effect on uptake. Treatment with several inhibitors suggested that berberine uptake depended on the ATP level. Some inhibitors of P-glycoprotein, an ABC transporter involved in multiple drug resistance in cancer cells, strongly inhibited berberine uptake, whereas a specific inhibitor for glutathione biosynthesis and vacuolar ATPase, bafilomycin A1, had little effect. Vanadate-induced ATP trap experiments to detect ABC proteins expressed in C. japonica cells showed that three membrane proteins of between 120 and 150 kDa were photolabelled with 8-azido-[alpha-32P] ATP. Two revealed the same photoaffinity-labelling pattern as P-glycoprotein, and the interaction of these proteins with berberine was also demonstrated. These results suggest that ABC proteins of the MDR-type are involved in the uptake of berberine from the medium.

ATP-Binding Cassette Transporters↗

PubMed2004

NtWBC1, an ABC transporter gene specifically expressed in tobacco reproductive organs.

To identify genes specifically or predominantly expressed in the stigmas/styles and to establish their possible function in the reproductive process of plants, a tobacco stigma/style cDNA library was constructed and differentially screened, resulting in the isolation of several cDNA clones. The molecular characterization of one of these clones is described here. After sequencing the cDNA and the isolated genomic clone, it was determined that the corresponding gene encodes a protein containing an ATP-binding cassette, characteristic of ABC transporters. This gene, designated as NtWBC1 (Nicotiana tabacum ABC transporter of the White-Brown Complex subfamily), encodes a protein that contains the typical structure of the 'half-transporters' of the White subfamily. To establish the spatial expression pattern of the NtWBC1 gene, northern blot and real-time RT-PCR analyses with total RNA from roots, stems, leaves, sepals, petals, stamens, stigmas/styles, ovaries, and seeds were performed. The result revealed a transcript of 2.5 kb present at high levels in stigmas and styles and a smaller transcript (2.3 kb) present at a lower level in stamens. NtWBC1 expression is developmentally regulated in stigmas/styles, with mRNA accumulation increasing toward anthesis. In situ hybridization experiments demonstrated that NtWBC1 is expressed in the stigmatic secretory zone and in anthers, at the stomium region and at the vascular bundle. NtWBC1 is the first ABC transporter gene with specific expression in plant reproductive organs to be identified and its expression pattern suggests important role(s) in the reproductive process.

ATP-Binding Cassette Transporters↗

PubMed2006

Isolation of a novel ABC-transporter gene from soybean induced by salicylic acid.

This paper reports on the identification and characterization of a new ATP-binding cassette (ABC) transporter which was identified as a salicylic acid-induced gene from soybean (Glycine max cv. Williams 82) in a subtractive suppression hybridization approach. A fragment of an ABC-transporter gene was used to isolate a full-length cDNA clone for this gene with a length of 4750 bp. The encoded protein has a length of 1447 amino acids and is composed of two similar repeat units typical of full-size ABC transporters. The sequence displays a close relationship to plant pleiotropic drug resistance (PDR)-type transporters and, on a homology basis, clusters together with the Arabidopsis thaliana PDR12 gene, suggesting GmPDR12 as a name for the gene isolated from soybean. GmPDR12 is rapidly responsive to salicylic acid and methyl jasmonate. The mRNA starts to accumulate 30 min after the addition of the signalling compounds. Salicylic acid is required for the execution of the hypersensitive reaction in soybean cell suspension cultures inoculated with Pseudomonas syringae pv. glycinea. It has been demonstrated previously that salicylic acid can be substituted by a variety of functional analogues of salicylic acid. All of these compounds lead to a strong and rapid transcriptional activation of GmPDR12, suggesting a shared signalling pathway.

ATP-Binding Cassette Transporters↗

PubMed2003

Application of vanadate-induced nucleotide trapping to plant cells for detection of ABC proteins.

The vanadate-induced nucleotide trapping technique, which has been conventionally used to characterize mammalian ATP-binding cassette (ABC) proteins, was applied to berberine-producing plant cell cultures, Thalictrum minus and Coptis japonica. One membrane protein at ca. 180 kDa was photoaffinity-labeled with 8-azido-[alpha-(32)P]ATP in the T. minus cells in the presence of vanadate, which was specifically induced by the addition of benzyladenine in a similar manner as the induction of berberine biosynthesis in these cell cultures, whereas three bands were observed in the C. japonica cells in the size region between 120 and 150 kDa corresponding to full-sized ABC protein. The benzyladenine-induced band in T. minus showed properties similar to those of human MDR1, including the recognition of berberine, which suggests that the ABC protein detected in T. minus takes this endogenous alkaloid as a putative substrate for transport. This is the first application of this technique to plant cells.

ATP-Binding Cassette Transporters↗

PubMed2001

The ABC transporter BcatrB affects the sensitivity of Botrytis cinerea to the phytoalexin resveratrol and the fungicide fenpiclonil.

During pathogenesis, fungal pathogens are exposed to a variety of fungitoxic compounds. This may be particularly relevant to Botrytis cinerea, a plant pathogen that has a broad host range and, consequently, is subjected to exposure to many plant defense compounds. In practice, the pathogen is controlled with fungicides belonging to different chemical groups. ATP-binding cassette (ABC) transporters might provide protection against plant defense compounds and fungicides by ATP-driven efflux mechanisms. To test this hypothesis, we cloned BcatrB, an ABC transporter-encoding gene from B. cinerea. This gene encodes a 1,439 amino acid protein with nucleotide binding fold (NBF) and transmembrane (TM) domains in a [NBF-TM6]2 topology. The amino acid sequence has 31 to 67% identity with ABC transporters from various fungi. The expression of BcatrB is up regulated by treatment of B. cinerea germlings with the grapevine phytoalexin resveratrol and the fungicide fenpiclonil. BcatrB replacement mutants are not affected in saprophytic growth on different media but are more sensitive to resveratrol and fenpiclonil than the parental isolate. Furthermore, virulence of deltaBcatrB mutants on grapevine leaves was slightly reduced. These results indicate that BcatrB is a determinant in sensitivity of B. cinerea to plant defense compounds and fungicides.

ATP-Binding Cassette Transporters↗

PubMedDate not supplied

ABC codes: a new opportunity to capture CNS contributions to US healthcare.

A specialized set of insurance-related codes for integrative healthcare will increase the national influence and patient-specific effectiveness of clinical nurse specialists (CNSs) and others in the US healthcare system because virtually every participant in the healthcare system uses codes for some critical purpose. Inadequate codes prevent decision makers from having essential health-related information at their fingertips. ABC codes improve business processes and health industry efficiencies in the same manner that universal product codes (UPCs/bar codes) improved the retail operations and the retail industry. The codes are essential to research, management, and commerce. In healthcare, the combination of ABC codes with older medical and dental code sets allows many essential business processes (such as forecasting, practice management, insurance billing, claims processing, and third-party reimbursement) to be fully automated. The codes also help digitize information to simplify data collection, analysis, and reporting. This improves the quality of data and accelerates the speed with which conclusions can be drawn from those data about what works in US healthcare and why. By offering CNSs more complete, accurate, and precise information on best practices, ABC codes help ensure that CNSs and others can generate better outcomes in addressing health-related challenges faced by patients/clients, nurses, and nursing practices, and the nation's health-promoting organizations and systems.

Electronic Data Processing↗

PubMed1991

Effects of chondroitinase ABC on intrathecal and peripheral nerve tissue. An in vivo experimental study on rabbits.

The enzyme chondroitinase ABC has recently been suggested for use in chemonucleolysis. The effects of 200 U ml of chondroitinase ABC were studied on intrathecal and peripheral nerve tissue in rabbits. After the intrathecal (subarachnoid) application of 0.2 ml of either the diluent in the control group (N = 2) or chondroitinase in the study group (N = 4), no neurologic deficit was detected. Compared with the control group, no morphologic changes at the light microscopic level were induced in the spinal cord by chondroitinase. No neurophysiologic differences were detected between tibial nerves after exposure to 1 ml of the diluent (control, N = 8) or chondroitinase (the other leg) for 4 weeks, nor did the study group, compared with the control group, show any morphologic changes in the tibial nerves. Because the concentration of chondroitinase ABC tested was approximately 40 times higher than might be used clinically for chemonucleolysis, the present study indicates a wide margin of safety for unwanted side effects on nerve tissue.

Animals↗

PubMed1981

Localization of HLA-ABC and DR antigens in human kidney.

Monoclonal antibodies to human monomorphic class I and class II major histocompatibility complex (MHC) determinants have been used with immunofluorescence and immunoperoxidase techniques, to localize these antigens in normal human kidneys. HLA-DR antigen was located in the glomeruli (probably on endothelium as well as the mesangium) and within the cells of cortical and medullary tubules. Dendritic cells in the renal interstitium stained brightly for the DR antigen and could be distinguished from the staining of capillary endothelium. The vascular endothelium of large vessels stained less densely for the HLA-DR antigen than for HLA-ABC antigens. The glomeruli stained intensely for the HLA-ABC antigens and diffuse staining of HLA-ABC antigens was also noted within renal tubular cells.

Animals↗

PubMed2006

The ABCs of HIV prevention in men: associations with HIV risk and protective behaviors.

OBJECTIVE: To elucidate associations between beliefs in abstinence, fidelity, and condom use (the "ABCs" of preventing HIV and other sexually transmitted infections) and associated self-reported risk behaviors among Kenyan men. METHODS: We assessed associations of beliefs in the ABCs with sociodemographic characteristics and sexual risk behaviors in a respondent-driven sample of 500 men in Nairobi. RESULTS: Younger age, single marital status, and higher education were associated with beliefs in abstinence and condom use as "best" prevention methods; and older age and marriage were associated with belief in fidelity. Many of these and other associations persisted in multivariate models. Men citing abstinence or fidelity belief less often reported sex with a female sex worker (FSW) ever or recent concurrent partnerships less often. Belief in fidelity was negatively associated with reported use of condoms ever. Belief in condom use to prevent HIV was most common among those having recent concurrent partnerships. CONCLUSIONS: Beliefs in abstinence, fidelity ("being faithful"), or condom use were associated, in plausible directions, with life stages and other demographic factors and with corresponding risk and preventive behaviors. Context-specific and selective educational promotion of individual ABC components rather than comprehensive education from an early age in a wide repertoire of prevention strategies ignores the evolution of sexual behaviors and the relative utility of different approaches throughout the life course.

Adolescent↗

PubMed1996

An operon from Lactobacillus helveticus composed of a proline iminopeptidase gene (pepI) and two genes coding for putative members of the ABC transporter family of proteins.

A proline iminopeptidase gene (pepI) of an industrial Lactobacillus helveticus strain was cloned and found to be organized in an operon-like structure of three open reading frames (ORF1, ORF2 and ORF3). ORF1 was preceded by a typical prokaryotic promoter region, and a putative transcription terminator was found downstream of ORF3, identified as the pepI gene. Using primer-extension analyses, only one transcription start site, upstream of ORF1, was identifiable in the predicted operon. Although the size of mRNA could not be judged by Northern analysis either with ORF1-, ORF2- or pepI-specific probes, reverse transcription-PCR analyses further supported the operon structure of the three genes. ORF1, ORF2 and ORF3 had coding capacities for 50.7, 24.5 and 33.8 kDa proteins, respectively. The ORF3-encoded PepI protein showed 65% identity with the PepI proteins from Lactobacillus delbrueckii subsp. bulgaricus and Lactobacillus delbrueckii subsp. lactis. The ORF1-encoded protein had significant homology with several members of the ABC transporter family but, with two distinct putative ATP-binding sites, it would represent an unusual type among the bacterial ABC transporters. ORF2 encoded a putative integral membrane protein also characteristic of the ABC transporter family. The pepI gene was overexpressed in Escherichia coli. Purified PepI hydrolysed only di and tripeptides with proline in the first position. Optimum PepI activity was observed at pH 7.5 and 40 degrees C. A gel filtration analysis indicated that PepI is a dimer of M(r) 53,000. PepI was shown to be a metal-independent serine peptidase having thiol groups at or near the active site. Kinetic studies with proline-p-nitroanilide as substrate revealed Km and Vmax values of 0.8 mM and 350 mmol min-1 mg-1, respectively, and a very high turnover number of 135,000 s-1.

ATP-Binding Cassette Transporters↗

PubMed2001

A plastidic ABC protein involved in intercompartmental communication of light signaling.

Plants perceive light via specialized photoreceptors of which the phytochromes (phyA-E), absorbing far-red (FR) and red light (R) are best understood. Several nuclear and cytoplasmic proteins have been characterized whose deficiencies lead to changes in light-dependent morphological responses and gene expression. However, no plastid protein has yet been identified to play a role in phytochrome signal transduction. We have isolated a new Arabidopsis mutant, laf (long after FR) 6, with reduced responsiveness preferentially toward continuous FR light. The disrupted gene in laf6 encodes a novel plant ATP-binding-cassette (atABC1) protein of 557 amino acids with high homology to ABC-like proteins from lower eukaryotes. In contrast to lower eukaryotic ABCs, however, atABC1 contains an N-terminal transit peptide, which targets it to chloroplasts. atABC1 deficiency in laf6 results in an accumulation of the chlorophyll precursor protoporphyrin IX and in attenuation of FR-regulated gene expression. The long hypocotyl phenotype of laf6 and the accumulation of protoporphyrin IX in the mutant can be recapitulated by treating wild-type (WT) seedlings with flumioxazin, a protoporphyrinogen IX oxidase (PPO) inhibitor. Moreover, protoporphyrin IX accumulation in flumioxazin-treated WT seedlings can be reduced by overexpression of atABC1. Consistent with the notion that ABC proteins are involved in transport, these observations suggest that functional atABC1 is required for the transport and correct distribution of protoporphyrin IX, which may act as a light-specific signaling factor involved in coordinating intercompartmental communication between plastids and the nucleus.

ATP-Binding Cassette Transporters↗