Vesiclepedia 2024: an extracellular vesicles and extracellular particles repository

Vesiclepedia (http://www.microvesicles.org) is a free web-based compendium of DNA, RNA, proteins, lipids and metabolites that are detected or associated with extracellular vesicles (EVs) and extracellular particles (EPs). EVs are membranous vesicles that are secreted ubiquitously by cells from all domains of life from archaea to eukaryotes. In addition to EVs, it was reported recently that EPs like exomeres and supermeres are secreted by some mammalian cells. Both EVs and EPs contain proteins, nucleic acids, lipids and metabolites and has been proposed to be implicated in several key biological functions. Vesiclepedia catalogues proteins, DNA, RNA, lipids and metabolites from both published and unpublished studies. Currently, Vesiclepedia contains data obtained from 3533 EV studies, 50 550 RNA entries, 566 911 protein entries, 3839 lipid entries, 192 metabolite and 167 DNA entries. Quantitative data for 62 822 entries from 47 EV studies is available in Vesiclepedia. The datasets available in Vesiclepedia can be downloaded as tab-delimited files or accessible through the FunRich-based Vesiclepedia plugin.

Proteomic analysis of the small extracellular vesicles and soluble secretory proteins from cachexia inducing and non-inducing cancer cells

Cancer cachexia is a wasting syndrome characterised by the loss of fat and/or muscle mass in advanced cancer patients. It has been well-established that cancer cells themselves can induce cachexia via the release of several pro-cachectic and pro-inflammatory factors. However, it is unclear how this process is regulated and the key cachexins that are involved. In this study, we validated C26 and EL4 as cachexic and non-cachexic cell models, respectively. Treatment of adipocytes and myotubes with C26 conditioned medium induced lipolysis and atrophy, respectively. We profiled soluble secreted proteins (secretome) as well as small extracellular vesicles (sEVs) released from cachexia-inducing (C26) and non-inducing (EL4) cancer cells by label-free quantitative proteomics. A total of 1268 and 1022 proteins were identified in the secretome of C26 and EL4, respectively. Furthermore, proteomic analysis of sEVs derived from C26 and EL4 cancer cells revealed a distinct difference in the protein cargo. Functional enrichment analysis using FunRich highlighted the enrichment of proteins that are implicated in biological processes such as muscle atrophy, lipolysis, and inflammation in both the secretome and sEVs derived from C26 cancer cells. Overall, our characterisation of the proteomic profiles of the secretory factors and sEVs from cachexia-inducing and non-inducing cancer cells provides insights into tumour factors that promote weight loss by mediating protein and lipid loss in various organs and tissues. Further investigation of these proteins may assist in highlighting potential therapeutic targets and biomarkers of cancer cachexia.

Effect of intraradicular reinforcement strategies on the fracture strength of endodontically treated anterior teeth with overflared canals

Background

This study is done to evaluate the effect of different reinforcement techniques of overflared root canals with fiber posts on the fracture resistance of endodontically treated anterior teeth. It also introduces a new technique for simultaneous reinforcement and cementation of fiber posts using dual-cured core build-up composite resin.

Material and Methods

The crowns of 48 single-rooted maxillary anterior teeth were cut and randomly divided into 4 groups (n=12) based on root reinforcement techniques after root canal treatment and post space preparation: Group 1: self-adhesive resin cement (SARC), Group2: dual-cure composite resin (DCC), Group3: Composite resin reinforcement (CRR), Group 4: Direct anatomical post (DAP). Then a core was made for the roots. The periodontal ligament was simulated using a thin layer of PVC impression material. A universal testing machine applied a compressive force to the lingual surface at an angle of 135 ° and 1 mm/min speed. Data were analyzed using One-Way ANOVA and a post-hoc Tukey test. Fracture patterns were analyzed using the Chi-square test (p<0.05).

Results

The difference between the control and DAP group was statistically significant (p=0.01), but there were no significant differences between other groups (p>0.05). Regarding fracture patterns, there were no significant differences between groups.

Conclusions

All reinforcement techniques increased the fracture strength compared to the control group. However, DAP was the only group that had a statistically significant difference. CRR and DCC presented intermediate values without significant differences.

Key words:Fiber post, endodontically treated teeth, root canals, reinforcement, fracture strength.

Oral administration of bovine milk-derived extracellular vesicles induces senescence in the primary tumor but accelerates cancer metastasis

The concept that extracellular vesicles (EVs) from the diet can be absorbed by the intestinal tract of the consuming organism, be bioavailable in various organs, and in-turn exert phenotypic changes is highly debatable. Here, we isolate EVs from both raw and commercial bovine milk and characterize them by electron microscopy, nanoparticle tracking analysis, western blotting, quantitative proteomics and small RNA sequencing analysis. Orally administered bovine milk-derived EVs survive the harsh degrading conditions of the gut, in mice, and is subsequently detected in multiple organs. Milk-derived EVs orally administered to mice implanted with colorectal and breast cancer cells reduce the primary tumor burden. Intriguingly, despite the reduction in primary tumor growth, milk-derived EVs accelerate metastasis in breast and pancreatic cancer mouse models. Proteomic and biochemical analysis reveal the induction of senescence and epithelial-to-mesenchymal transition in cancer cells upon treatment with milk-derived EVs. Timing of EV administration is critical as oral administration after resection of the primary tumor reverses the pro-metastatic effects of milk-derived EVs in breast cancer models. Taken together, our study provides context-based and opposing roles of milk-derived EVs as metastasis inducers and suppressors.

A High-Resolution Mass Spectrometry-Based Quantitative Metabolomic Workflow Highlights Defects in 5-Fluorouracil Metabolism in Cancer Cells with Acquired Chemoresistance

Currently, 5-fluorouracil (5-FU)-based combination chemotherapy is the mainstay in the treatment of metastatic colorectal cancer (CRC), which benefits approximately 50% of the patients. However, these tumors inevitably acquire chemoresistance resulting in treatment failure. The molecular mechanisms driving acquired chemotherapeutic drug resistance in CRC is fundamental for the development of novel strategies for circumventing resistance. However, the specific phenomenon that drives the cancer cells to acquire resistance is poorly understood. Understanding the molecular mechanisms that regulate chemoresistance will uncover new avenues for the treatment of CRC. Among the various mechanisms of acquired chemoresistance, defects in the drug metabolism pathways could play a major role. In the case of 5-FU, it gets converted into various active metabolites, which, directly or indirectly, interferes with the replication and transcription of dividing cells causing DNA and RNA damage. In this project, we developed a high-resolution mass spectrometry-based method to effectively extract and quantify levels of the 5-FU metabolites in cell lysates and media of parental and 5-FU resistant LIM1215 CRC cells. The analysis highlighted that the levels of 5-FU metabolites are significantly reduced in 5-FU resistant cells. Specifically, the level of the nucleotide fluorodeoxyuridine monophosphate (FdUMP) is reduced with treatment of 5-FU clarifying the compromised 5-FU metabolism in resistant cells. Corroborating the metabolomic analysis, treatment of the resistant cells with FdUMP, an active metabolite of 5-FU, resulted in effective killing of the resistant cells. Overall, in this study, an effective protocol was developed for comparative quantitation of polar metabolites and nucleotide analogues from the adherent cells efficiently. Furthermore, the utility of FdUMP as an alternative for CRC therapy is highlighted.

P2506Prognostic importance of ventilatory efficiency in healthy subjects

Background

Low cardiorespiratory fitness, defined by reduced maximal oxygen consumption (VO2), is a predictor of mortality in patients without chronic disease. However, the relation between ventilatory efficiency (as measured by the slope of the relation between ventilation (VE) and carbon dioxide production (VCO2)) and all-cause mortality is unknown.

Purpose

To assess the relation between variables derived from cardiopulmonary exercise testing and long-term survival in normal subjects

Method

We recruited 145 healthy subjects, with no history of chronic disease (57% male, mean age 63±12) from primary care at random. All participants underwent cardiopulmonary exercise testing at baseline. Participants were followed for 15.5±3.5 years. The primary end-point was all-cause mortality. Cox-proportional hazard models were used to assess the relationship between measures of exercise performance and outcome. Hazard ratios (HR) are reported with 95% confidence intervals (CI).

Results

During follow up, 34 participants (23.4%) died. On univariable analysis, VE/VCO2 slope, peak VO2, respiratory exchange ratio at peak exercise, peak heart rate and 6-minute walk test distance were significant predictors of all-cause mortality (table 1). However, only VE/VCO2 slope (HR per unit increase: 1.13, 95% CI: 1.00–1.28, P=0.043) and peak heart rate (HR per 10 unit increase: 0.73, 95% CI: 0.57–0.93, P=0.010) were independent predictors of all-cause mortality on multivariable analysis.

Table 1. Cox regression analysis (univariable and multivariable) for cardiopulmonary exercise testing measures and all-cause mortality HR Presentation Univariable analysis Multivariable analysis HR 95% CI p value HR 95% CI p value Peak VO2 (ml/kg/min) Per unit increase 0.90 0.86–0.95 &lt;0.001 0.94 0.86–1.03 0.214 VE/VCO2 slope Per unit increase 1.08 1.01–1.17 0.049 1.13 1.00–1.28 0.043 Exercise RER Per 0.1 unit increase 0.46 0.31–0.67 &lt;0.001 0.72 0.45–1.17 0.185 Peak heart rate (bpm) Per 10 unit increase 0.73 0.65–0.81 &lt;0.001 0.73 0.57–0.93 0.010 6MWT (metre) Per 25 unit increase 0.92 0.86–0.98 0.009 1.02 0.86–1.17 0.789 Peak systolic BP (mmHg) Per 10 unit increase 1.13 0.98–1.31 0.101 – – – Multivariable analysis is adjusted for age, body mass index, sex, smoking, resting systolic blood pressure and forced vital capacity. Abbreviations: 6MWT, 6-minute walk test; CI, confidence interval; HR, hazard ratio; RER, respiratory exchange ratio.

Conclusions

Raised VE/VCO2 slope is an independent predictor of all-cause mortality in healthy patients with no history of chronic disease.

Excision of rare carotid body tumour without preembolisation: Case report and literature review

INTRODUCTION

Carotid body tumors also known as parganglioma or chemodactomas are one of the rare tumors of head and neck which present as slow growing masses in the neck region. We present a case of 40 years female with painless slow growing mass over left side of her neck for 6 months. Diagnosis was made on basis of clinical history, examination and radiological findings. Tumor was graded as Shamblin grade II. She was managed with excision of the tumor without preoperative embolisation. Intraoperative and postoperative periods were uneventful.

CASE PRESENTATION

A forty years female presented with left sided painless neck swelling∼5 × 4 cm² over left anterior triangle for 6 months with no history of dysphagia, odynophagia, change in voice, shortness of breath, palpitations, tremors or syncopal attacks. She underwent USG neck and CT angiogram. Based upon the radiological and clinical findings, she was diagnosed asCarotid body tumor. She was managed with excision of the tumor without preembolisation. Her diagnosis was confirmed with histopathology.

CONCLUSION

Carotid body tumours are rare entities of head and neck region. They are mostly benign in nature. Though mostly bening, increasing size might result in grave complications. Thus, the recommended treatment for carotid body tumors is early excision with or without pre-embolisation. In our case preembolisation was not performed. Though some studies have suggested the use of preoperative embolisation in large sized tumors, more studies are yet required to justify the choice of preembolisation despite the dreaded complications.

A Pilot Study on Screening of BRCA1 Mutations (185delAG, 1294del40) in Nepalese Breast Cancer Patients

BACKGROUND

Breast cancer is the second most common malignancy among Nepalese women, accounting for 60% of the total cancer cases in females. Women diagnosed with germline mutations in BRCA1 like 185delAG, 1294del40 develop breast and/or ovarian cancer with a lifelong likelihood of up to 85% whereas presence of a mutation increases the risk for mutations to occur in other genes. The major objective of this study was to find the prevalence of these mutations in Nepalese cancer patients.

MATERIALS AND METHODS

This prospective study was carried out at two cancer hospitals in the Kathmandu valley over a period of 11 months. Irrespective of age group and stage of canceran appropriate amount of blood was withdrawn from 50 breast cancer patients and 20 controls. DNA was extracted manually and subjected to PCR using primers for 185delAG and 1294del40 mutations. PCR products were then digested with restriction enzyme (DdeII) followed by electrophoresis.

RESULTS

Prevalence of 185delAG in reference breast cancer patients was found to be 4/50 (8%) but no 1294del40 was apparent.

CONCLUSIONS

Several mutations occurring in different exons of BRCA1 as well as mutations in other genes like BRCA2, for example, should also be taken in account.

Isolates and their Antibiogram in Different Samples from a Tertiary Care Hospital, Kathmandu

Introduction: The emergence and spread of antimicrobial resistance constitutes a major risk for human health by limiting the success of these agents in the therapy. The widespread uses of antibiotics, together with the length of time over which they have been available, have led to major problems of resistant organisms contributing to morbidity and mortality. Knowledge of etiological agent and its sensitivities to available drugs is of immense value to the rational selection and use of antimicrobial agents and to the development of appropriate prescribing policies. The aim of this study was to prepare a local antibiogram of the commonly isolated organism at a tertiary care hospital.Methods: A prospective study was conducted at KMC Teaching Hospital, from April 14th to 17th September 2014. Laboratory data of culture and sensitivity were collected from hospital Microbiology Laboratory and analyzed using SPSS software.Results: In our study most of the isolates were Gram negative with Klebsiella Spp. and Escherichia coli being predominant with many MDR isolates. The isolates were found to be resistant to different groups of drugs. We found least resistance to Chloramphenicol, Imepenem and Amikacin. Most of the resistance was found against Amoxicillin and Erythromycin. Among gram positive S. aureus was predominant with 64.7% MRSA and 23.1% VRSA isolates.Conclusions: The most sensitive drug for gram positive was Chloramphenicol, Cephotaxim and Norfloxacine. The only drug which was 100% sensitive to Gram Negative organism was Chloramphenicol. 

Electrochemical corrosion assessment of RaCe and Mtwo rotary nickle-titanium instruments after clinical use and sterilization

Aim: The aim of the present study was to electrochemically evaluate corrosion resistance of RaCe and Mtwo files after repeated sterilization and preparation procedures. Study Design: A total of 450 rotary files were used. In the working groups, 72 files from each file type were distributed into 4 groups. RaCe and Mtwo files were used to prepare one root canal of the mesial root of extracted human mandibular first molars. The procedure was repeated to prepare 2 to 8 canals. The following irrigation solutions were used: group 1, RaCe files with 2.5% NaOCl; group 2, RaCe files with normal saline; group 3, Mtwo files with 2.5% NaOCl; and group 4, Mtwo files with normal saline in the manner described. In autoclave groups, 72 files from each file type were evenly distributed into 2 groups. Files were used for a cycle of sterilization without the use of files for root canal preparation. Nine new unused files from each file type were used as controls. Then the instruments were sent for corrosion assessment. Mann-Whitney U and Wilcoxon tests were used for independent and dependent groups, respectively. Results: Statistical analysis indicated that there were significant differences in corrosion resistance of files associated with working and autoclave groups between RaCe and Mtwo file types (p<0.001). Conclusions: Corrosion resistance of #25, #30, and #35 Mtwo files is significantly higher than that in RaCe files with similar sizes.

Key words:Corrosion, NiTi instruments, autoclave, RaCe, Mtwo.

Efficacy of different concentrations of sodium hypochlorite and chlorhexidine in disinfection of contaminated Resilon cones

OBJECTIVES

The aim of this study was to evaluate the effectiveness of different concentrations of Chlorhexidine (CHX) and sodium hypochlorite (NaOCl) in disinfecting contaminated Resilon cones within one minute.

STUDY DESIGN

Fifty Resilon cones were divided into seven experimental groups and three control groups of 5 cones each. The cones of experimental groups were contaminated with E. faecalis and subsequently disinfected with different concentrations of NaOCl or CHX. The cones were then transferred into glass tubes containing thioglycollate media and incubated for 7 days. The tubes were examined for turbidity every 24 hours, and if bacterial growth occurred, samples were plated, incubated, gram stained and observed under microscope to confirm E. faecalis growth. Negative, positive, and washing control groups were also used.

RESULTS

All the positive and washing control showed profound E.faecalis growth. All the cones disinfected with CHX showed bacterial growth; however, no E. faecalis growth occurred in any samples disinfected with NaOCl.

CONCLUSION

Sodium hypochlorite, at concentrations of 0.5 to 5.25%, is an effective agent for disinfection of contaminated Resilon cones within one minute; however, chlorhexidine is unable to disinfect Resilon cones during one-minute exposure.

Multi-wavelength laser generation with Bismuthbased Erbium-doped fiber

A multi-wavelength laser comb is demonstrated using a nonlinear effect in a backward pumped Bismuth-based Erbium-doped fiber (Bi-EDF) for the first time. It uses a ring cavity resonator scheme containing a 215 cm long highly nonlinear Bi-EDF, optical isolators, polarisation controller and 10 dB output coupler. The laser generates more than 10 lines of optical comb with a line spacing of approximately 0.41 nm at 1615.5 nm region using 146 mW of 1480 nm pump power.

Compact Brillouin-erbium fiber laser

A single-wavelength Brillouin fiber laser (BFL) is demonstrated at the extended L-band region using bismuth-based erbium-doped fiber (Bi-EDF) for the first time to the best of our knowledge. A 2.15-m-long Bi-EDF is used to provide both nonlinear and linear gains to generate a stimulated Brillouin scattering (SBS) and to amplify the generated SBS, respectively. The BFL operates at 1613.93 nm, which is upshifted by 0.09 nm from the Brillouin pump with a peak power of 2 dBm and a side-mode suppression ratio of more than 22 dB. The generated BFL has a narrow linewidth and many potential applications, such as in optical communication and sensors.

Metabolites of ginsenosides as novel BCRP inhibitors

We have previously shown ginsenosides derived from Panax ginseng exert opposing effects on angiogenesis. Here, we examined protopanaxadiol-containing ginsenosides (Rg3, Rh2, and PPD) and protopanaxatriol-containing ginsenosides (Rg1, Rh1, and PPT) as potential inhibitors of breast cancer resistance protein (BCRP). Among these ginsenosides, metabolites Rh2, PPD, and PPT significantly enhanced the cytotoxicity of mitoxantrone (MX) to human breast carcinoma MCF-7/MX cells which overexpress BCRP. PPD was the most potent followed by Rh2 and PPT. This effect was not seen in sensitive MCF-7 cells. Rg3, Rg1, and Rh1 were ineffective in either MCF-7 or MCF-7/MX cells. PPD, Rh2, and PPT were able to inhibit MX efflux in MCF-7/MX cells. PPD and Rh2 also increased MX uptake. In inside out membrane vesicles from Lactococcus lactis cells expressing BCRP, only PPD was found to significantly inhibit BCRP-associated vanadate sensitive ATPase activity. These results indicate that metabolites PPD, Rh2, and PPT were inhibitors of BCRP.

Similarities between ATP-dependent and ion-coupled multidrug transporters

The movement of drugs across biological membranes is mediated by two major classes of membrane transporters. Primary-active, ABC (ATP-binding cassette) multidrug transporters are dependent on ATP-binding/hydrolysis, whereas secondary-active multidrug transporters are coupled to the proton (or sodium)-motive force that exists across the plasma membrane. Recent work on LmrA, an ABC multidrug transporter in Lactococcus lactis, suggests that primary- and secondary-active multidrug transporters share functional and structural features. Some of these similarities and their implications for the mechanism of transport by ABC multidrug transporters will be discussed.

New light on multidrug binding by an ATP-binding-cassette transporter

ATP-binding-cassette (ABC) multidrug transporters confer multidrug resistance to pathogenic microorganisms and human tumour cells by mediating the extrusion of structurally unrelated chemotherapeutic drugs from the cell. The molecular basis by which ABC multidrug transporters bind and transport drugs is far from clear. Genetic analyses during the past 14 years reveal that the replacement of many individual amino acids in mammalian multidrug resistance P-glycoproteins can affect cellular resistance to drugs, but these studies have failed to identify specific regions in the primary amino acid sequence that are part of a defined drug-binding pocket. The recent publication of an X-ray crystallographic structure of the bacterial P-glycoprotein homologue MsbA and an MsbA-based homology model of human P-glycoprotein creates an opportunity to compare the original mutagenesis data with the three-dimensional structures of transporters. Our comparisons reveal that mutations that alter specificity are present in three-dimensional 'hotspot' regions in the membrane domains of P-glycoprotein.

The role of Trypanosoma brucei MRPA in melarsoprol susceptibility

We previously showed that over-expression of Trypanosoma brucei MRPA, a member of the multidrug resistance protein family in T. brucei, reproducibly resulted in resistance to the anti-trypanosomal drug melarsoprol in vitro. MRPA is predicted to mediate efflux of melarsoprol as a conjugate with trypanothione, a glutathione-spermidine conjugate which is the major small thiol in trypanosomes. Here, we show that depletion of MRPA by RNA interference resulted in moderate hypersensitivity to both melarsoprol and melarsen oxide. Over-expression of MRPA alone is not sufficient to cause melarsoprol resistance in vivo, although it is sufficient in vitro. This discrepancy is not an effect of drug metabolism since over-expression of MRPA alone conferred resistance to melarsoprol and its principle metabolite, melarsen oxide, in vitro. Over-expression of MRPA was not detected in four melarsoprol-resistant trypanosome isolates from sleeping sickness patients.

Modulation of p-glycoprotein and breast cancer resistance protein by some prescribed corticosteroids

Efflux transporters, p-glycoprotein and breast cancer resistance protein (BCRP), located at barrier sites such as the blood-brain barrier may affect distribution of steroids used for treating chronic inflammatory conditions and thus the extent to which they may perturb the hypothalamic-pituitary-adrenal axis. In the present study, six different glucocorticoids were investigated for their possible interactions with these efflux transporters. Beclomethasone dipropionate, mometasone furoate and ciclesonide active principle but not fluticasone propionate or triamcinolone, (all at 0.1 to 10 microM) caused inhibition of efflux, resulting in increased accumulation of mitoxantrone in BCRP-expressing MCF7/MR breast cancer cells and of calcein in p-glycoprotein-expressing SW620/R colon carcinoma cell. At 5 microM the same three increased sensitivity of p-glycoprotein-expressing SW620/R to doxorubicin and stimulated ATPase activity associated with BCRP expressed in bacterial membrane vesicles. Budesonide also stimulated ATPase activity. These data demonstrate the capacity of some clinically used glucocorticoids to interact with efflux transporters.

Drug-lipid A interactions on the Escherichia coli ABC transporter MsbA

MsbA is an essential ATP-binding cassette half-transporter in the cytoplasmic membrane of the gram-negative Escherichia coli and is required for the export of lipopolysaccharides (LPS) to the outer membrane, most likely by transporting the lipid A core moiety. Consistent with the homology of MsbA to the multidrug transporter LmrA in the gram-positive Lactococcus lactis, our recent work in E. coli suggested that MsbA might interact with multiple drugs. To enable a more detailed analysis of multidrug transport by MsbA in an environment deficient in LPS, we functionally expressed MsbA in L. lactis. MsbA expression conferred an 86-fold increase in resistance to the macrolide erythromycin. A kinetic characterization of MsbA-mediated ethidium and Hoechst 33342 transport revealed apparent single-site kinetics and competitive inhibition of these transport reactions by vinblastine with K(i) values of 16 and 11 microM, respectively. We also detected a simple noncompetitive inhibition of Hoechst 33342 transport by free lipid A with a K(i) of 57 microM, in a similar range as the K(i) for vinblastine, underscoring the relevance of our LPS-less lactococcal model for studies on MsbA-mediated drug transport. These observations demonstrate the ability of heterologously expressed MsbA to interact with free lipid A and multiple drugs in the absence of auxiliary E. coli proteins. Our transport data provide further functional support for direct LPS-MsbA interactions as observed in a recent crystal structure for MsbA from Salmonella enterica serovar Typhimurium (C. L. Reyes and G. Chang, Science 308:1028-1031, 2005).

Arginine-482 is not essential for transport of antibiotics, primary bile acids and unconjugated sterols by the human breast cancer resistance protein (ABCG2)

The human BCRP (breast cancer resistance protein, also known as ABCG2) is an ABC (ATP-binding cassette) transporter that extrudes various anticancer drugs from cells, causing multidrug resistance. To study the molecular determinants of drug specificity of BCRP in more detail, we have expressed wild-type BCRP (BCRP-R) and the drug-selected cancer cell line-associated R482G (Arg482-->Gly) mutant BCRP (BCRP-G) in Lactococcus lactis. Drug resistance and the rate of drug efflux in BCRP-expressing cells were proportional to the expression level of the protein and affected by the R482G mutation, pointing to a direct role of BCRP in drug transport in L. lactis. In agreement with observations in mammalian cells, the BCRP-R-mediated transport of the cationic substrates rhodamine 123 and tetramethylrosamine was significantly decreased compared with the activity of BCRP-G. In addition, BCRP-R showed an enhanced interaction with the anionic anticancer drug methotrexate when compared with BCRP-G, suggesting that structure/substrate specificity relationships in BCRP, as observed in eukaryotic expression systems, are maintained in prokaryotic L. lactis. Interestingly, BCRP-R exhibited a previously unestablished ability to transport antibiotics, unconjugated sterols and primary bile acids in L. lactis, for which the R482G mutation was not critical. Since Arg482 is predicted to be present in the intracellular domain of BCRP, close to transmembrane segment 3, our results point to a role of this residue in electrostatic interactions with charged substrates including rhodamine 123 and methotrexate. Since unconjugated sterols are neutral molecules and bile acids and many antibiotics are engaged in protonation/deprotonation equilibria at physiological pH, our observations may point either to a lack of interaction between Arg482 and neutral or neutralized moieties in these substrates during transport or to the interaction of these substrates with regions in BCRP not including Arg482.

The ATP binding cassette multidrug transporter LmrA and lipid transporter MsbA have overlapping substrate specificities

LmrA is an ATP binding cassette (ABC) multidrug transporter in Lactococcus lactis that is a structural and functional homologue of the human multidrug resistance P-glycoprotein MDR1 (ABCB1). LmrA is also homologous to MsbA, an essential ABC transporter in Escherichia coli involved in the trafficking of lipids, including Lipid A. We have compared the substrate specificities of LmrA and MsbA in detail. Surprisingly, LmrA was able to functionally substitute for a temperature-sensitive mutant MsbA in E. coli WD2 at non-permissive temperatures, suggesting that LmrA could transport Lipid A. LmrA also exhibited a Lipid A-stimulated, vanadate-sensitive ATPase activity. Reciprocally, the expression of MsbA conferred multidrug resistance on E. coli. Similar to LmrA, MsbA interacted with photoactivatable substrate [3H]azidopine, displayed a daunomycin, vinblastine, and Hoechst 33342-stimulated vanadate-sensitive ATPase activity, and mediated the transport of ethidium from cells and Hoechst 33342 in proteoliposomes containing purified and functionally reconstituted protein. Taken together, these data demonstrate that MsbA and LmrA have overlapping substrate specificities. Our observations imply the presence of structural elements in the recently published crystal structures of MsbA in E. coli and Vibrio cholera (Chang, G., and Roth, C. B. (2001) Science 293, 1793-1800; Chang, G. (2003) J. Mol. Biol. 330, 419-430) that support drug-protein interactions and suggest a possible role for LmrA in lipid trafficking in L. lactis.

ABC transporters and drug resistance in parasitic protozoa

Parasitic protozoa are responsible for a wide spectrum of diseases in humans and domestic animals. The main line of defence available against these organisms is chemotherapy. However, the application of chemotherapeutic drugs has resulted in the development of resistance mechanisms, which limit the number of antiprotozoal drugs that are effective in the treatment and control of parasitic diseases. Knowledge about the resistance mechanisms involved may allow the development of new drugs that minimise or circumvent drug resistance or may identify new targets for drug development. This review focuses on the role of protozoal ATP-binding cassette (ABC) transporters in drug resistance. These membrane proteins mediate the ATP-dependent transport of a wide variety of chemotherapeutic drugs away from their targets inside the parasites. The genome sequence of Plasmodium falciparum and Plasmodium yoelii has recently been completed, and the sequencing of other parasitic genomes are now underway. As a result, many new membrane transporters belonging to the ABC superfamily are being discovered. We review the ABC transporters in major parasitic protozoa, including Plasmodium, Leishmania, Trypanosoma and Entamoeba species. Transporters with an established role in drug resistance have been emphasised, but newly discovered transporters with a significant amino acid sequence identity to established ABC drug transporters have also been included.

A new dimer interface for an ABC transporter

The crystallization of MsbA, an ATP-binding cassette (ABC) transporter involved in the transport of Lipid A in Escherichia coli, provided a fascinating glimpse into the high-resolution structure of an ABC transporter at 4.8 A. The E. coli crystal structure of MsbA reveals a dimer. Although the structure of the MsbA monomer is consistent with the biochemistry of ABC transporters, including the human multidrug resistance P-glycoprotein, the interface between the monomers in the MsbA dimer may not reflect the biologically relevant interface. We considered the interface in a two-armed MsbA dimer, named spiral. Our findings indicate that (i) the spiral MsbA dimer may have biological relevance for ABC transporters that interact with lipophilic substrates, and (ii) the dimer interface observed in the crystal structure of E. coli MsbA represents a crystallization artefact. A comparison of the spiral MsbA dimer with the recently published structure of MsbA in Vibrio cholera is also described.

Sterol transport by the human breast cancer resistance protein (ABCG2) expressed in Lactococcus lactis

The human breast cancer resistance protein (BCRP, also know as ABCG2, MXR, or ABCP) is one of the more recently discovered ATP-binding cassette (ABC) transporters that confer resistance on cancer cells by mediating multidrug efflux. In the present study, we have obtained functional expression of human BCRP in the Gram-positive bacterium Lactococcus lactis. BCRP expression conferred multidrug resistance on the lactococcal cells, which was based on ATP-dependent drug extrusion. BCRP-mediated ATPase and drug transport activities were inhibited by the BCRP-specific modulator fumitremorgin C. To our knowledge these data represent the first example of the functional expression of a mammalian ABC half-transporter in bacteria. Although members of the ABCG subfamily (such as ABCG1 and ABCG5/8) have been implicated in the transport of sterols, such a role has not yet been established for BCRP. Interestingly, the BCRP-associated ATPase activity in L. lactis was significantly stimulated by (i) sterols including cholesterol and estradiol, (ii) natural steroids such as progesterone and testosterone, and (iii) the anti-estrogen anticancer drug tamoxifen. In addition, BCRP mediated the efflux of [3H]estradiol from lactococcal cells. Our findings suggest that BCRP may play a role in the transport of sterols in human, in addition to its ability to transport multiple drugs and toxins.

Ribozymes that cleave reovirus genome segment S1 also protect cells from pathogenesis caused by reovirus infection

Reovirus genome segment S1 encodes protein final sigma1, which is the receptor binding protein, modulates tissue tropism, and specifies the nature of the antiviral immune response. It makes up less than 2% of reovirus particles and is synthesized in very small amounts in infected cells. Any antiviral strategy aimed at reducing specifically the expression of this genome segment should, in principle, reduce the infectivity of the virus. To test this hypothesis, we have assembled two hammer-head motif-containing ribozymes (Rzs) targeted to cleave at the conserved B and C domains of the reovirus s1 RNA. Protein-independent but Mg(2+)-dependent sequence-specific cleavage of s1 RNA was achieved by both the Rzs in trans. Cells that transiently express these Rzs, when challenged with reovirus, were protected against the cytopathic effects caused by the virus. This protection correlated with the specific intracellular reduction of s1 transcripts that was due to their cleavage by the Rzs. Rz-treated cells that were challenged with reovirus showed almost complete disappearance of protein final sigma1 without significantly altering the levels of the other reovirus structural proteins. Thus, Rzs, besides acting as antiviral agents, could be exploited as biological tools to delineate specific functions of target genes.

Targeted cleavage of HIV-1 envelope gene by a DNA enzyme and inhibition of HIV-1 envelope-CD4 mediated cell fusion

With the ultimate aim of developing an effective antiviral strategy against HIV-1, a mono-DNA enzyme possessing the 10-23 catalytic motif [Santoro and Joyce (1997) Proc. Natl. Acad. Sci. USA 94, 4264-4266] was synthesized against the HIV-1 envelope gene. We tested the in vitro cleavage efficiency of the 178 bp long truncated HIV-1 Env transcript by DNA enzyme 6339. Protein independent and Mg2+ dependent specific cleavage products were obtained. As soon as 5 min after mixing equimolar concentrations of DNA enzyme and substrate RNA, more than 50% cleavage was observed which increased steadily over a period of 4 h. Very little cleavage was obtained at 1 mM MgCl2 concentration which improved significantly when the concentration of MgCl2 was increased up to 20 mM. Specific inhibition of cell membrane fusion caused by the interaction of gp160 and CD4 in HeLa cells was observed when the above DNA enzyme was used. Thus, these chemically synthesized DNA enzymes could prove to be very useful for in vivo application.

Inheritance pattern of mutant human immunodeficiency virus type 1 coreceptor gene CCR5 in an Indian family

The most common form of mutation found in the CCR5 gene has been the precise 32-base pair (bp) deletion in the region corresponding to second extracellular loop of the chemokine receptor CCR5. Individuals homozygous for the delta 32 allele of CCR5 usually remain uninfected despite multiple exposures to HIV, whereas heterozygous individuals support less virus replication and show slower progression of the disease. This mutant allele in either homozygous or heterozygous form is quite common in white people of European heritage. Earlier work involving large populations of Asians and Africans failed to detect the presence of this mutant allele. We screened 145 normal unrelated healthy Indians and found one person who was heterozygous for the delta 32 allele of CCR5. We studied the inheritance of this deleted allele in this person's family. One parent, one of two sons, and the only daughter possessed this mutant allele. We cloned the entire coding region of wild-type and mutant alleles of CCR5 gene from the heterozygous individual mentioned and studied its coreceptor functions. The mutant allele had only a moderate interfering effect on coreceptor activity of the wild-type CCR5 allele in a cell fusion assay. We also report an improved method of genotyping CCR5 gene in this communication.

First report of a healthy Indian heterozygous for delta 32 mutant of HIV-1 co-receptor-CCR5 gene

The beta-chemokine receptor, CCR5, is a major co-receptor for macrophage tropic non-syncytia-inducing isolates of HIV-1. Recently a 32 bp homozygous deletion in the coding region of CCR5 has been reported in a very small percentage (< 1%) of Caucasian individuals who remain uninfected, despite multiple exposure to the wild-type virus. This mutant allele in the heterozygous form (CCR5/32 ccr5) was readily detected in a normal unrelated Caucasian population of European heritage with varying frequencies (13-20%). However, when a large number of the non-Caucasian population (261 Africans and 423 Asians) were screened for the presence of this deleted allele, not a single case of either homozygous or heterozygous mutant for delta 32 allele of CCR5 was detected. We screened 100 normal individuals and found a single heterozygous case with an identical 32 bp deletion in CCR5 gene reported earlier, the rest possessed wild-type alleles. This deleted gene was inherited in Mendelian fashion among the family members of this individual. Thus, the frequency of this deleted allele in India among unrelated normal individuals is likely to be very low (< 1%). We observed a moderate transdominant effect of this mutant allele in a fusion assay. Finally, we show a significant inhibition of fusion of cell membranes when the 176-bp region of CCR5 was used as an antisense.

Immune response against the non-repeat region (293-310) of the circumsporozoite protein of Plasmodium vivax

Immunization by peptides based on the repeat sequences of Plasmodium falciparum or P. vivax antigen(s) have shown inconsistent results during clinical trials in humans. This could be attributed to the lack of T-cell help or antigenic polymorphism. Thus, attention has been focused towards the more conserved non-repeat regions. The present study was undertaken to map the antigenic determinant in the vicinity of region II (outside the repeat) of CS protein of P. vivax. The immunogenicity of the peptide was studied alone and after linking with polytuftsin (PT), using alum and Freund's adjuvant, in inbred strains of mice with different genetic backgrounds. The humoral response and antigen induced T-cell proliferation assays clearly demonstrated the immunomodulatory activity of PT. Comparable results were observed with antigen(s) administered either in alum or Freund's adjuvant. The induction of IgG2a and IgG2b antibody isotypes by both, peptide as well as the conjugate, may indicate that the T-helper response involved is of Th1 type. Further the immunofluorescence studies have shown that antibodies recognized the air dried sporozoites of P. cynomolgi. The results thus show that the above sequence has overlapping B and T-cell determinants and that alum can be substituted for Freund's adjuvant in generating an effective immune response.