RT-PCR determination of maspin and mammaglobin B in peripheral blood of healthy donors and breast cancer patients

BACKGROUND

The aim of the present study was to evaluate the accuracy of two markers, maspin and mammaglobin B, singly or in combination, to detect breast cancer. To define better the potential and limits of the two markers for diagnostic purposes, blood positivity was analyzed in relation to clinical, pathological and biological tumor characteristics.

PATIENTS AND METHODS

The markers were determined in peripheral blood (PB) samples from 27 healthy donors and 140 previously untreated patients using nested reverse transcriptase polymerase chain reaction (RT-PCR).

RESULTS

Positivity for maspin in blood samples was observed in 24% of patients with an 89% specificity. For mammaglobin B, positivity was observed in 7% of patients and never in healthy donors. The presence of maspin was correlated with cell proliferation of the primary tumor (P = 0.015), whereas mammaglobin B positivity correlated with pathological stage (P = 0.013). The presence of either marker was significantly related to nodal status.

CONCLUSIONS

Our results indicate that the two markers in association could represent a potentially useful non-invasive tool to detect breast cancer. The validation of these markers as indicators of high risk of relapse is ongoing in a series of patients with an adequate follow-up.

Secretoglobin 2A1 Is under Selective Androgen Control Mediated by a Peculiar Binding Site for Sp Family Transcription Factors

Human secretoglobin (SCGB) 2A1 (or lipophilin C, lacryglobin, mammaglobin B) is a small protein of unknown function that forms heterodimers with secretoglobin 1D1 (lipophilin A) in tears and is expressed in the prostate. Here we show that SCGB 2A1 is under androgen control in the androgen-responsive prostatic cell line LNCaP and can be induced more than 20-fold by dihydrotestosterone. Only 6 h after androgen treatment, a strong DNase I-hypersensitive site is induced in the proximal promoter within chromatin. Within the boundaries of this DNase I-hypersensitive site a minimal 32-bp peculiar dimeric inverted repeat variant GC box (dim-IR-GA box) was found to confer androgen but not glucocorticoid responsiveness in gene transfer experiments. Mutations of both GA boxes that abolish binding of Sp1 and Sp3 also abrogate the androgen response. In an EMSA the DNA binding domain of the androgen receptor (AR) was not able to bind directly to the dim-IR-GA box. However, AR is functionally required for the hormone response because induction can be inhibited with the nonsteroidal antagonist bicalutamide. Chromatin immunoprecipitation experiments demonstrated that AR is recruited to the proximal promoter 10 min after androgen treatment. Therefore we propose that SCGB 2A1 represents a new class of androgen target genes that are purely under indirect AR control mediated by DNA-bound Sp factors.

Mild Pelizaeus-Merzbacher disease caused by a point mutation affecting correct splicing of PLP1 mRNA

We describe a 28-year-old male patient with a mild course of Pelizaeus-Merzbacher disease (PMD) who presented with developmental delay in his second year of life and was able to walk until 12 years of age. Several computed tomography scans in infancy and youth were normal, the diagnosis of PMD was eventually suggested by magnetic resonance imaging at the age of 24 years. Analysis of the proteolipid protein gene (PLP1) revealed a nucleotide exchange (c.762G>T) at the 3' border of exon 6, which did not entail an amino acid exchange but adversely affected splicing. PCR analysis of fibroblast cDNA showed that c.762G>T resulted in partial skipping of exon 6 in the PLP1 mRNA. Exclusion of exon 6 does not alter the reading frame but leads to absence of amino acids 232-253 that constitute a main part of the fourth transmembrane helix of the PLP protein. Remarkably, residual wild-type splicing was also detected in the patient's cultured fibroblasts. This might explain the mild phenotype in this case, as exon 6 skipping mutations resulted in a severe course of disease in other patients.

Interactions of proteoliposomes from serogroup B Neisseria meningitidis with bone marrow-derived dendritic cells and macrophages: adjuvant effects and antigen delivery

Exposure to proteoliposomes from serogroup B Neisseria meningitidis (PL) induced up-regulation of MHC-II, MHC-I, CD40, CD80 and CD86 expression on the surface of murine bone marrow-derived dendritic cells (DC). CD40, CD80 and CD86 were up-regulated on bone marrow-derived macrophages (MPhi) upon stimulation with PL. Both DC and MPhi released TNFalpha, but only DC produced IL12(p70) in response to PL. A small increase in the expression of MHC-II, CD40 and CD86, as well as production of IL12(p70), was observed on the cell surface of DC, but not MPhi from LPS-non-responder C3H/HeJ after exposure to PL. DC, but not MPhi, incubated with PL containing ovalbumin (PL-OVA) presented OVA-specific peptides to CD4+ and CD8+ OVA-specific T-cell hybridomas. These data clearly indicate that PL exert an immunomodulatory effect on DC and MPhi, with some contribution of non-LPS components besides the main role of LPS. The work also shows the potential of PL as a general system to deliver antigens to DC for presentation to CD4+ and CD8+ T-cells.

Ultrafast purification and reconstitution of His-tagged cysteine-less Escherichia coli F1Fo ATP synthase

His-tagged cysteine-less F1Fo ATP synthase from Escherichia coli was purified using Ni-NTA affinity chromatography. During the purification procedure the loss of total ATPase activity did not exceed 50%, and the extent of purification was about 80-fold. The purified enzyme was essentially free of other proteins, was highly active in ATP hydrolysis (75 units/mg at pH 8 and 37 degrees C), and was sensitive to N,N'-dicyclohexylcarbodiimide (70%). Incorporation of F1Fo into soybean liposomes yielded well-coupled and highly active proteoliposomes. The entire procedure, from the disruption of cells by French press to the preparation of proteoliposomes, took only about 8 h. Some improvements in procedures for the estimation of rates of both ATP hydrolysis and ATP-dependent 9-amino-6-chloro-2-methoxyacridine (ACMA) fluorescence quenching are described.

PLP2/A4 interacts with CCR1 and stimulates migration of CCR1-expressing HOS cells

Multiple CC chemokines bind to CCR1, which plays important roles in immune and inflammatory responses. To search for proteins involved in the CCR1 signaling pathway, we screened a yeast two-hybrid library using the cytoplasmic tail of CCR1 as the bait. One of the positive clones contained an open reading frame of 456bp, of which the nucleotide sequence was identical to that of proteolipid protein 2 (PLP2), also known as protein A4. Mammalian two-hybrid and coimmunoprecipitation analyses demonstrated the association of PLP2/A4 with CCR1. Indirect immunofluorescence analysis revealed that PLP2/A4 was predominantly located in plasma membrane and colocalized with CCR1 in transfected human HEK293 cells. In addition, focal staining of CCR1 appeared on the periphery of the membrane upon short exposure to Leukotactin-1(Lkn-1)/CCL15, a CCR1 agonist, and was costained with PLP2/A4 on the focal regions. PLP2/A4 mRNAs were detected in various cells such as U-937, HL-60, HEK293, and HOS cells. Overexpression of PLP2/A4 stimulated a twofold increase in the agonist-induced migration of HOS/CCR1 cells, implicating a functional role for PLP2/A4 in the chemotactic processes via CCR1.

Cytochrome c, an ideal antioxidant

Generation of DeltaPsi (membrane potential) by cytochrome oxidase proteoliposomes oxidizing superoxide-reduced cytochrome c has been demonstrated. XO+HX (xanthine oxidase and hypoxanthine) were used to produce superoxide. It was found that the generation of DeltaPsi is completely abolished by cyanide (an uncoupler) or by superoxide dismutase, and is enhanced by nigericin. Addition of ascorbate after XO+HX causes a further increase in DeltaPsi. On the other hand, XO+HX added after ascorbate do not affect DeltaPsi, indicating that superoxide does not have measurable protonophorous activity. The half-maximal cytochrome c concentration for DeltaPsi generation supported by XO+HX was found to be approx. 1 microM. These data and the results of some other researchers can be rationalized as follows: (1) O(2) accepts an electron to form superoxide; (2) cytochrome c oxidizes superoxide back to O(2); (3) an electron removed from the reduced cytochrome c is transferred to O(2) by cytochrome oxidase in a manner that generates Deltamicro(H(+)) (transmembrane difference in electrochemical H(+) potential). Thus cytochrome c mediates a process of superoxide removal, resulting in regeneration of O(2) and utilization of the electron involved previously in the O(2) reduction. It is important that cytochrome c is not damaged during the antioxidant reaction, in contrast with many other antioxidants.

Lipid composition-dependent incorporation of multiple membrane proteins into liposomes

Membrane proteins from bacteria Pasteurella multocida were used as a model for studying its incorporation into liposomes. An important step to achieve efficient high yield protein incorporation in proteoliposomes is the study of the more suitable lipid composition. To this end, we compared the amount of total protein, reconstituted by co-solubilization methods, into liposomes of phospholipids with different polar head groups and acyl chain lengths. The liposomes and proteoliposomes were characterised by isopycnic centrifugation in sucrose gradient and by dynamic light scattering. Experimental and theoretical results were compared considering the effects exerted through the hydrocarbon chain length, volume, and optimal cross-sectional area of the phospholipid (combined in the geometrical critical packing parameter, lipid-protein matching), critical spontaneous radius of curvature of the bilayer vesicle, phase transition temperature of the lipid and ratio of lipid-protein molecules present in the vesicles. The highest incorporation of multiple proteins was found with dipalmitoylphosphatidylcholine (DPPC), reaching a yield of 93% compared to the lower relative amounts incorporated in proteoliposomes of the other lipids. The incorporation of multiple proteins induces a proportional enhancement of vesicular dimension, since DPPC-proteoliposomes have an average diameter of 1850A, compared to the 1430A for pure DPPC vesicles.

RT-PCR for mammaglobin genes, MGB1 and MGB2, identifies breast cancer micrometastases in sentinel lymph nodes

In the present study, we examined the expression of the mammaglobin genes, MGB1 and MGB2, in the sentinel lymph nodes (SLNs) of patients with breast cancer and compared our results with the histologic status of the same SLNs. Compared with immunohistochemical staining for cytokeratin 8, which detected metastases in 17 of 42 patients, reverse transcription-polymerase chain reaction (RT-PCR) for MGB1 or MGB2 genes was positive in 22 patients. The concordance between the expression of any mammaglobin and histologic status was 79% (33/42), with a sensitivity of 88% and specificity of 72%. The detection of patients with metastases was more sensitive when testing for both MGB1 and MGB2 (P < .0001) rather than MGB2 (P < .0005) or MGB1 (P < .05) alone. The increased detection rate relative to histologic examination suggests that using RT-PCR for the mammaglobin genes might identify patients at higher risk compared with patients with negative RT-PCR results.

Gene profiling reveals increased expression of uteroglobin and other anti-inflammatory genes in glucocorticoid-treated nasal polyps

BACKGROUND

Treatment with local glucocorticoids (GCs) decreases symptoms and the size of nasal polyps. This might depend on the downregulation of proinflammatory genes, as well as the upregulation of anti-inflammatory genes.

OBJECTIVE

We sought to identify GC-regulated anti-inflammatory genes in nasal polyps.

METHODS

Affymetrix DNA microarrays were used to analyze the expression of 22,283 genes in 4 nasal polyps before and after local treatment with fluticasone (400 microg/d). Expression of uteroglobin and mammaglobin B was analyzed with real-time PCR in 6 nasal polyps and in nasal biopsy specimens from 6 healthy control subjects.

RESULTS

Two hundred three genes had changed in expression in treated polyps, and 139 had known functions: 54 genes were downregulated, and 85 were upregulated. Genes associated with inflammation constituted the largest single functional group. These genes affected key steps in inflammation (eg, immunoglobulin production; antigen processing and presentation; and the chemoattraction and activation of granulocytes, T cells, and B cells). Several proinflammatory genes were downregulated. In contrast, some anti-inflammatory genes were upregulated. The gene that increased most in terms of expression was uteroglobin. This was confirmed with real-time PCR. By contrast, expression of uteroglobin was lower in untreated polyps than in healthy nasal mucosa. Immunohistochemical investigation showed staining of uteroglobin in the epithelium and in seromucous glands in control subjects and in nasal polyps.

CONCLUSION

Upregulation of anti-inflammatory genes, such as uteroglobin, might contribute to the effects of local treatment with GCs in nasal polyps.

Imaging single membrane fusion events mediated by SNARE proteins

Using total internal reflection fluorescence microscopy, we have developed an assay to monitor individual fusion events between proteoliposomes containing vesicle soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) and a supported planar bilayer containing cognate target SNAREs. Approach, docking, and fusion of individual vesicles to the target membrane were quantified by delivery and subsequent lateral spread of fluorescent phospholipids from the vesicle membrane into the target bilayer. Fusion probability was increased by raising divalent cations (Ca2+ and Mg2+). Fusion of individual vesicles initiated in <100 ms after the rise of Ca2+ and membrane mixing was complete in 300 ms. Removal of the N-terminal H(abc) domain of syntaxin 1A increased fusion probability >30-fold compared to the full-length protein, but even in the absence of the H(abc) domain, vesicle fusion was still enhanced in response to Ca2+ increase. Our observations establish that the SNARE core complex is sufficient to fuse two opposing membrane bilayers at a speed commensurate with most membrane fusion processes in cells. This real-time analysis of single vesicle fusion opens the door to mechanistic studies of how SNARE and accessory proteins regulate fusion processes in vivo.

High level cell-free expression and specific labeling of integral membrane proteins

We demonstrate the high level expression of integral membrane proteins (IMPs) in a cell-free coupled transcription/translation system using a modified Escherichia coli S30 extract preparation and an optimized protocol. The expression of the E. coli small multidrug transporters EmrE and SugE containing four transmembrane segments (TMS), the multidrug transporter TehA with 10 putative TMS, and the cysteine transporter YfiK with six putative TMS, were analysed. All IMPs were produced at high levels yielding up to 2.7 mg of protein per mL of reaction volume. Whilst the vast majority of the synthesized IMPs were precipitated in the reaction mixture, the expression of a fluorescent EmrE-sgGFP fusion construct showed evidence that a small part of the synthesized protein 'remained soluble and this amount could be significantly increased by the addition of E. coli lipids into the cell-free reaction. Alternatively, the majority of the precipitated IMPs could be solubilized in detergent micelles, and modifications to the solubilization procedures yielded proteins that were almost pure. The folding induced by formation of the proposed alpha-helical secondary structures of the IMPs after solubilization in various micelles was monitored by CD spectroscopy. Furthermore, the reconstitution of EmrE, SugE and TehA into proteoliposomes was demonstrated by freeze-fracture electron microscopy, and the function of EmrE was additionally analysed by the specific transport of ethidium. The cell-free expression technique allowed efficient amino acid specific labeling of the IMPs with 15N isotopes, and the recording of solution NMR spectra of the solubilized EmrE, SugE and YfiK proteins further indicated a correctly folded conformation of the proteins.

Predicting biomarkers for ovarian cancer using gene-expression microarrays

Ovarian cancer has the highest mortality rate of gynaecological cancers. This is partly due to the lack of effective screening markers. Here, we used oligonucleotide microarrays complementary to ∼12 000 genes to establish a gene-expression microarray (GEM) profile for normal ovarian tissue, as compared to stage III ovarian serous adenocarcinoma and omental metastases from the same individuals. We found that the GEM profiles of the primary and secondary tumours from the same individuals were essentially alike, reflecting the fact that these tumours had already metastasised and acquired the metastatic phenotype. We have identified a novel biomarker, mammaglobin-2 (MGB2), which is highly expressed specific to ovarian cancer. MGB2, in combination with other putative markers identified here, could have the potential for screening.

Nasal mucosal gene expression in patients with allergic rhinitis with and without nasal polyps

BACKGROUND

Nasal polyps are a common problem that is difficult to diagnose and treat, in part because the cause of nasal polyposis is unknown. Although information on the pathogenesis of polyposis is lacking, there are reports suggesting that a genetic predisposition underlies this disorder.

OBJECTIVE

We sought to better understand the basis of nasal polyposis associated with allergic rhinitis. We hypothesize that the expression of unique genes is associated with the nasal polyposis phenotype.

METHODS

We examined 12000 human genes transcribed in the nasal mucosa of patients with allergic rhinitis with and without nasal polyps. Biopsy specimens of the mucosa of patients with and without polyps were obtained after the patients refrained from the use of topical or systemic steroid therapy for 2 weeks.

RESULTS

Thirty-four genes were differentially expressed between the patient groups, including those for inflammatory molecules and putative growth factors. The greatest differential expression identified by the array analysis was for a group of genes associated with neoplasia, including mammaglobin, a gene transcribed 12-fold higher in patients with polyps compared with control patients with rhinitis alone. Quantitative RT-PCR confirmed this differential expression and documented that the number of mammaglobin mRNA copies is actually 64-fold greater in tissues of patients with polyps versus control patients. The specificity of mammaglobin protein expression was evaluated by means of immunohistochemistry, which showed specific staining in nasal polyp mucosal goblet cells only in patients with polyps.

CONCLUSION

These data suggest that nasal polyposis involves deregulated cell growth, using gene activation in some ways similar to a neoplasm. In addition, mammaglobin, a gene of unknown function associated with breast neoplasia, might be related to polyp growth.

Patterns of regional lymph node involvement in intrahepatic cholangiocarcinoma of the left lobe

Lymph node involvement is an important prognostic factor in intrahepatic cholangiocarcinoma. Besides the nodes in the hepatoduodenal ligament, recent studies have suggested that the nodes around the cardiac portion of the stomach or along the gastric lesser curvature can be affected when the primary tumor is located in the left hepatic lobe. However, the distribution of metastatic nodes has not been well described in this disease. Thirteen patients with intrahepatic cholangiocarcinoma in the left hepatic lobe were enrolled in this study. Lymphatic mapping was performed by means of both histologic examination and reverse transcriptase-polymerase chain reaction assays. Nodal involvement around the cardiac portion of the stomach or along the lesser gastric curvature (left pathway) was found in 7 (54%) of 13 patients by histologic examination or reverse transcriptase-polymerase chain reaction, whereas positive nodes in the hepatoduodenal ligament (right pathway) were found in 6 (46%) of 13 patients. Two patients (15%) had positive nodes only in the left pathway. Therefore, for a more accurate clinical staging of intrahepatic cholangiocarcinoma in the hepatic left lobe, lymph nodes around the cardiac portion of the stomach and along the lesser gastric curvature should be examined in addition to nodes in the hepatoduodenal ligament.

[Electrogenic reactions in cytochrome bf-complexes in a model system]

By using the direct electrometric technique, the flash-induced generation of the difference in electrical potentials in hybrid proteoliposomes containing photosystem 1 and cytochrome bf complexes from cyanobacteria Synechocystis sp. PCC 6803 was studied. It was shown that the primary donor P700 in photosystem I and cytochrome f are predominantly localized near the outer surface of the proteoliposomal membrane, which made it possible to study for the first time electrogenic reactions of cytochrome bf complexes in a model system. In the presence of decyl plastoquinol and cytochrome c6, besides the fast electrogenic phase determined by the separation of charges in photosystem I, additional electrogenic phases in the submillisecond and millisecond ranges were observed. These phases were partially depressed in the presence of the inhibitor of the plastoquinone reductase site NQNO and fully disappeared after the addition of the inhibitor of the plastoquinol oxidase site stigmatellin. A possible mechanism of the electrogenic reactions in cytochrome bf complexes was considered.

Transcriptional activity of the tandem repeat polymorphism in the 5'-flanking region of the human CYP2E1 gene

BACKGROUND

There are remarkable interindividual differences in the expression of cytochrome P-4502E1(CYP2E1), which in turn may alter susceptibility to alcohol-related diseases and various cancers. We recently characterized the tandem repeat polymorphism in the 5'-flanking region of the human CYP2E1 gene and found that subjects with the homozygous mutant-type (A4/A4) may be at higher risk of developing esophageal cancer. In this study, we determined how this tandem repeat polymorphism alters transcriptional activities of the human CYP2E1 gene by transfection studies.

METHODS

The 5'-flanking region (-2,562 base pair to +9 base pair) of the CYP2E1 gene from three individuals of different genotypes (A2/A2, A2/A4, A4/A4) was amplified by polymerase chain reaction. The polymerase chain reaction products placed in front of a luciferase reporter gene were transfected into human hepatoblastoma cells, human esophageal cancer cells, and human uterus cancer cells. Transcriptional activities were determined by the dual-luciferase assay. When indicated, ethanol (50 mM) was included in the culture medium. CYP2E1 messenger RNA levels in peripheral lymphocytes were measured by the real-time reverse transcription-polymerase chain reaction using the LightCycler system.

RESULTS

The construct including the tandem repeat region exhibited luciferase activities in both A2 and A4 type. It was of note that the activity produced by the A4 allele was significantly greater than that by A2 allele in HeLa cells (p < 0.001). CYP2E1 messenger RNA levels in peripheral blood lymphocytes were comparable between the two genotypes.

CONCLUSION

Transcriptional activity of the mutant allele of the tandem repeat polymorphism in the 5'-flanking region of the CYP2E1 gene is greater than that of the wild type.

[Effects of altered peptide ligands (APLs) of proteolipid(136-150) on T-cell clone 4B.14a]

AIM

By investigating the effects of APLs of PLP(136-150) on T cell clone 4B.14a in-vitro and in-vivo, to determine the feasibility of APLs to prevent relapsing multiple sclerosis (MS) in human.

METHODS

To mimic the clinic course of relapsing MS, SJL/J female mice were first irradiated at 450R and intravenously infused with 1x10(7) resting 4B.14a T cells per mouse. Then mice were immunized with 50 microg/mouse APL for inducing passive experiment allergic encephalomyelitis (EAE). The proliferation and cytokine production of 4B.14a T cells in response to APLs were also examined.

RESULTS

Except 139A, 143A, 144A, 145A and 148A, other APLs triggered T cells to induce passive EAE; 4B.14a T cells well responded to the most APLs, weakly responded to 137A, 144A and 148A, but the response was suppressed by 139A.

CONCLUSION

The effects of some APLs on 4B.14a T cells are different in-vitro and in-vivo. It may be feasible to select some APLs to prevent relapsing MS in human.

Molecular basis for membrane selectivity of NK-2, a potent peptide antibiotic derived from NK-lysin

Increasing resistance of pathogenic bacteria against antibiotics is a severe problem in health care. Natural antimicrobial peptides and derivatives thereof have emerged as promising candidates for "new antibiotics". In contrast to classical antibiotics, these peptides act by direct physical destabilization of the target cell membrane. Nevertheless, they exhibit a high specificity for bacteria over mammalian cells. However, the precise mechanism of action and the molecular basis for membrane selectivity are still a matter of debate. We have designed a new peptide antibiotic (NK-2) with enhanced antimicrobial activity based on an effector protein of mammalian immune cells (NK-lysin). Here we describe the interaction of this alpha-helical synthetic peptide with membrane mimetic systems, designed to mimic the lipid compositions of mammalian and bacterial cytoplasmic membranes. Utilizing fluorescence and biosensor assays, we could show that on one hand, NK-2 strongly interacts with negatively charged membranes; on the other hand, NK-2 is able to discriminate, without the necessity of negative charges, between the zwitterionic phospholipids phosphatidylethanolamine (PE) and phosphatidylcholine (PC), the major constituents of the outer leaflet of the cytoplasmic membranes of bacteria and mammalian cells, respectively.

The mitochondrial oxoglutarate carrier: structural and dynamic properties of transmembrane segment IV studied by site-directed spin labeling

The structural and dynamic features of the fourth transmembrane segment of the mitochondrial oxoglutarate carrier were investigated using site-directed spin labeling and electron paramagnetic resonance (EPR). Using a functional carrier protein with native cysteines replaced with serines, the 18 consecutive residues from S184 to S201 which are believed to form the transmembrane segment IV were substituted individually with cysteine and labeled with a thiol-selective nitroxide reagent. Most of the labeled mutants exhibited significant oxoglutarate transport in reconstituted liposomes, where they were examined by EPR as a function of the incident microwave power in the presence and absence of two paramagnetic perturbants, i.e., the hydrophobic molecular oxygen or the hydrophilic chromium oxalate complex. The periodicity of the sequence-specific variation in the spin-label mobility and the O(2) accessibility parameters unambiguously identifies the fourth transmembrane segment of the mitochondrial oxoglutarate carrier as an alpha-helix. The accessibility to chromium oxalate is out of phase with oxygen accessibility, indicating that the helix is amphipatic, with the hydrophilic face containing the residues found to be important for transport activity by site-directed mutagenesis and chemical modification. The helix is strongly packed, as indicated by the values of normalized mobility, which also suggest that the conformational changes occurring during transport probably involve the N-terminal region of the helix.

CFTR directly mediates nucleotide-regulated glutathione flux

Studies have shown that expression of cystic fibrosis transmembrane conductance regulator (CFTR) is associated with enhanced glutathione (GSH) efflux from airway epithelial cells, implicating a role for CFTR in the control of oxidative stress in the airways. To define the mechanism underlying CFTR-associated GSH flux, we studied wild-type and mutant CFTR proteins expressed in Sf9 membranes, as well as purified and reconstituted CFTR. We show that CFTR-expressing membrane vesicles mediate nucleotide-activated GSH flux, which is disrupted in the R347D pore mutant, and in the Walker A K464A and K1250A mutants. Further, we reveal that purified CFTR protein alone directly mediates nucleotide-dependent GSH flux. Interestingly, although ATP supports GSH flux through CFTR, this activity is enhanced in the presence of the non-hydrolyzable ATP analog AMP-PNP. These findings corroborate previous suggestions that CFTR pore properties can vary with the nature of the nucleotide interaction. In conclusion, our data demonstrate that GSH flux is an intrinsic function of CFTR and prompt future examination of the role of this function in airway biology in health and disease.