A Plant Homolog of Animal Chloride Intracellular Channels (CLICs) Generates an Ion Conductance in Heterologous Systems

The genome of Arabidopsis thaliana contains unusual members of the glutathione S-transferase (GST) superfamily with a cysteine in place of a serine at the active site. Four of these genes (at-dhar 1-4) have an appreciable homology to intracellular Cl- channels (CLICs) from vertebrates and invertebrates. Transient expression of AtDHAR1 as wild type protein or as a chimera with GFP in mammalian HEK293 or Chinese hamster ovary cells generated a distinct inward rectifying conductance with a characteristic biphasic kinetics but no apparent ion selectivity. Analysis of the subcellular localization of AtDHRA1::GFP showed that the bulk of the protein was located as soluble form in the cytoplasm; however, an appreciable fraction of it could also be found in association with the non-soluble microsomal fraction. These data suggest that plant members of the GST superfamily have similar to those from animals multiple functions. The increase of ion conductance by AtDHAR1 is better explained by a CLIC-like channel activity than by a modification of endogenous channel proteins.

Glutathione S-transferase interacting with far-red insensitive 219 is involved in phytochrome A-mediated signaling in Arabidopsis

Far-red (FR) insensitive 219 (FIN219) was previously shown to be involved in phytochrome A-mediated FR light signaling. To further understand its function and regulatory relation with other light-signaling components, a yeast two-hybrid approach was used to isolate FIN219-interacting partners. Here, we demonstrate that FIN219-interacting protein 1 (FIP1) interacts with FIN219 in vitro and in vivo and is composed of 217 amino acids that belong to the tau class of the large glutathione S-transferase gene family. FIP1 was further shown to have glutathione S-transferase activity. The gain of function and partial loss of function of FIP1 resulted in a hyposensitive hypocotyl phenotype under continuous FR (cFR) light and a delayed flowering phenotype under long-day conditions, which suggests that FIP1 may exist in a complex to function in the regulation of Arabidopsis (Arabidopsis thaliana) development. In addition, FIP1 mRNA was down-regulated in the suppressor of phytochrome A-105 1 mutant and differentially expressed in constitutive photomorphogenic 1-4 (cop1-4) and cop1-5 mutants under cFR. Intriguingly, FIP1 expression was up-regulated in the fin219 mutant under all light conditions, except cFR. Furthermore, promoter activity assays revealed that FIP1 expression was light dependent, mainly associated with vascular tissues, and developmentally regulated. Subcellular localization studies revealed that the beta-glucuronidase-FIP1 fusion protein was localized in the nucleus and cytoplasm. Taken together, these data indicate that FIP1 may interact with FIN219 to regulate cell elongation and flowering in response to light.

Glutathione Transferases Sequester Toxic Dinitrosyl-Iron Complexes in Cells

It is now well established that exposure of cells and tissues to nitric oxide leads to the formation of a dinitrosyl-iron complex bound to intracellular proteins, but little is known about how the complex is formed, the identity of the proteins, and the physiological role of this process. By using EPR spectroscopy and enzyme activity measurements to study the mechanism in hepatocytes, we here identify the complex as a dinitrosyl-diglutathionyl-iron complex (DNDGIC) bound to Alpha class glutathione S-transferases (GSTs) with extraordinary high affinity (K(D) = 10(-10) m). This complex is formed spontaneously through NO-mediated extraction of iron from ferritin and transferrin, in a reaction that requires only glutathione. In hepatocytes, DNDGIC may reach concentrations of 0.19 mm, apparently entirely bound to Alpha class GSTs, present in the cytosol at a concentration of about 0.3 mm. Surprisingly, about 20% of the dinitrosyl-glutathionyl-iron complex-GST is found to be associated with subcellular components, mainly the nucleus, as demonstrated in the accompanying paper (Stella, L., Pallottini, V., Moreno, S., Leoni, S., De Maria, F., Turella, P., Federici, G., Fabrini, R., Dawood, K. F., Lo Bello, M., Pedersen, J. Z., and Ricci, G. (2007) J. Biol. Chem. 282, 6372-6379). DNDGIC is a potent irreversible inhibitor of glutathione reductase, but the strong complex-GST interaction ensures full protection of glutathione reductase activity in the cells, and in vitro experiments show that damage to the reductase only occurs when the DNDGIC concentration exceeds the binding capacity of the intracellular GST pool. Because Pi class GSTs may exert a similar role in other cell types, we suggest that specific sequestering of DNDGIC by GSTs is a physiological protective mechanism operating in conditions of excessive levels of nitric oxide.

Electrostatic Association of Glutathione Transferase to the Nuclear Membrane

The possible nuclear compartmentalization of glutathione S-transferase (GST) isoenzymes has been the subject of contradictory reports. The discovery that the dinitrosyl-diglutathionyl-iron complex binds tightly to Alpha class GSTs in rat hepatocytes and that a significant part of the bound complex is also associated with the nuclear fraction (Pedersen, J. Z., De Maria, F., Turella, P., Federici, G., Mattei, M., Fabrini, R., Dawood, K. F., Massimi, M., Caccuri, A. M., and Ricci, G. (2007) J. Biol. Chem. 282, 6364-6371) prompted us to reconsider the nuclear localization of GSTs in these cells. Surprisingly, we found that a considerable amount of GSTs corresponding to 10% of the cytosolic pool is electrostatically associated with the outer nuclear membrane, and a similar quantity is compartmentalized inside the nucleus. Mainly Alpha class GSTs, in particular GSTA1-1, GSTA2-2, and GSTA3-3, are involved in this double modality of interaction. Confocal microscopy, immunofluorescence experiments, and molecular modeling have been used to detail the electrostatic association in hepatocytes and liposomes. A quantitative analysis of the membrane-bound Alpha GSTs suggests the existence of a multilayer assembly of these enzymes at the outer nuclear envelope that could represent an amazing novelty in cell physiology. The interception of potentially noxious compounds to prevent DNA damage could be the possible physiological role of the perinuclear and intranuclear localization of Alpha GSTs.

Transcriptome analysis of root-knot nematode functions induced in the early stages of parasitism

Root-knot nematodes of the genus Meloidogyne are obligate biotrophic parasites able to infest > 2000 plant species. The nematode effectors responsible for disease development are involved in the adaptation of the parasite to its host environment and host response modulation. Here, the differences between the transcriptomes of preparasitic exophytic second-stage juveniles (J2) and parasitic endophytic third-stage juveniles (J3) of Meloidogyne incognita were investigated. Genes up-regulated at the endophytic stage were isolated by suppression subtractive hybridization and validated by dot blots and real-time quantitative polymerase chain reaction (PCR). Up-regulation was demonstrated for genes involved in detoxification and protein degradation, for a gene encoding a putative secreted protein and for genes of unknown function. Transcripts of the glutathione S-transferase gene Mi-gsts-1 were 27 times more abundant in J3 than in J2. The observed Mi-gsts-1 expression in the oesophageal secretory glands and the results of functional analyses based on RNA interference suggest that glutathione S-transferases are secreted during parasitism and are required for completion of the nematode life cycle in its host. Secreted glutathione S-transferases may protect the parasite against reactive oxygen species or modulate the plant responses triggered by pathogen attack.

Meta- and pooled analysis of GSTT1 and lung cancer: a HuGE-GSEC review

Lung cancer is the most common malignancy in the Western world, and the main risk factor is tobacco smoking. Polymorphisms in metabolic genes may modulate the risk associated with environmental factors. The glutathione S-transferase theta 1 gene (GSTT1) is a particularly attractive candidate for lung cancer susceptibility because of its involvement in the metabolism of polycyclic aromatic hydrocarbons found in tobacco smoke and of other chemicals, pesticides, and industrial solvents. The frequency of the GSTT1 null genotype is lower among Caucasians (10-20%) than among Asians (50-60%). The authors present a meta- and a pooled analysis of case-control, genotype-based studies that examined the association between GSTT1 and lung cancer (34 studies, 7,629 cases and 10,087 controls for the meta-analysis; 34 studies, 7,044 cases and 10,000 controls for the pooled analysis). No association was observed between GSTT1 deletion and lung cancer for Caucasians (odds ratio (OR) = 0.99, 95% confidence interval (CI): 0.87, 1.12); for Asians, a positive association was found (OR = 1.28, 95% CI: 1.10, 1.49). In the pooled analysis, the odds ratios were not significant for either Asians (OR = 0.97, 95% CI: 0.83, 1.13) or Caucasians (OR = 1.09, 95% CI: 0.99, 1.21). No significant interaction was observed between GSTT1 and smoking on lung cancer, whereas GSTT1 appeared to modulate occupational-related lung cancer.

The glutathione S-transferases: a group of multifunctional detoxification proteins

The physiological roles of the glutathione S-transferases, by whatever name, seem to result in detoxification. As is true of albumin, members of this group of proteins bind an enormous number of compounds that appear to have in common only hydrophobic topography; the binding of bilirubin is an example of a major function common to all higher species. If the ligand bears a sufficiently electrophilic center, it will be attacked by the nucleophile GSH; such compounds would be the substrates of the enzyme. And should such a ligand be extraordinarily reactive--as, for example, some of the epoxide carcinogens generated by the cytochrome P450-linked, mixed-function oxidases, or even 1-chloro-2,4-dinitrobenzene--then reaction may occur either with GSH or irreversibly with the transferase itself. By reason of the wide distribution and high intracellular concentration of these proteins, there appears to be sufficient enzyme for all three roles in detoxification.

Glutathione s-transferases M1 and P1 prevent aggravation of allergic responses by secondhand smoke

RATIONALE

Secondhand tobacco smoke (SHS) and traffic-related air pollutants are associated with asthma and allergy. Diesel exhaust particles (DEPs) and SHS can interact with allergens in exacerbating allergic airway diseases through generation of reactive oxygen species. Glutathione S-transferases (GSTs) metabolize reactive oxygen species and detoxify electrophilic xenobiotics present in SHS and DEPs.

OBJECTIVES

We tested the hypotheses that functional GSTM1-null genotype and GSTP1 codon 105 variants (Ile105 and Val105) are determinants of allergic responses to SHS, and that responses to SHS and DEPs are correlated.

METHODS AND MEASUREMENTS

In a randomized, placebo-controlled crossover trial, 19 ragweed allergen-sensitive subjects who had previously participated in a DEP trial were challenged intranasally with allergen after having been exposed to either clean air or SHS at separate visits. Nasal allergen-specific IgE, histamine, IL-4, and IFN-gamma levels were measured before and after allergen challenge.

MAIN RESULTS

Individuals with GSTM1-null or GSTP1 Ile105 genotypes showed larger nasal responses to allergens with SHS compared with clean air. GSTM1-null subjects had a larger increase in IgE than GSTM1-present subjects (median, 173.3 vs. 46.7 U/ml; p = 0.03), and the Ile105 GSTP1 genotype subjects had increased histamine (median, 10.2 vs. 4.6 nM; p = 0.01) after SHS plus allergen challenge. Responses to SHS and DEPs were correlated. Enhancement of IgE and histamine was greatest in the subjects with both the GSTM1-null and GSTP1 Ile/Ile genotypes.

CONCLUSIONS

GSTM1 and GSTP1 are important cytoprotective factors that reduce SHS and DEP exacerbation of allergic responses.

[Adaptation of methods for quantification of the effect of esterase, acetylcholinesterase and glutathione-S-transferase in Blattella germanica (Dictyoptera: Blattellidae)]

The resistance mechanisms of Blatella germanica, one of the most important urban plagues worldwide since it is a mechanical vector that houses a number of highly harmful viruses, fungi, helmints and bacteria were studied. There are different control methods used against Blattella germnanica, with insecticides playing the leading role. Their uncontrolled application has caused the development of insecticice resistance in this species. This paper adapted biochemical methods to detect the enzymes esterase, acetylcholinesterase and glutathine-S-transferase as posible resistance mechanisms. To this end, all the parameters that allow finding out if a strain is susceptible or resistant to each mechanism were set.

Glutathione S-transferase M1 and P1 genotype, passive smoking, and peak expiratory flow in asthma

OBJECTIVES

Our purpose with this work was to assess the contribution of glutathione S-transferase gene variants to asthma susceptibility and pulmonary function in relation to tobacco smoke exposure in the home.

METHODS

Young individuals with asthma (age: 3-21 years; n = 504) were recruited through primary and secondary care throughout Tayside, Scotland (BREATHE Study). Spirometry was obtained on 407 individuals. Binary logistic regression and general linear modeling were used to explore phenotypic characteristics by genotype and tobacco smoke exposure status in younger children (3-12 years; n = 384) and teenagers and young adults (13-21 years; n = 120).

RESULTS

Three- to 12-year-olds with asthma, null for the GSTM1 gene or homozygous for the GSTP1Val105 allele, were overrepresented in the group exposed to environmental tobacco smoke. No differences in lung function values could be detected in this group. In contrast, 13- to 21-year-olds with the GSTM1-null genotype or homozygous for the GSTP1Val105 allele from smoking households were more likely to have a substantially lower percentage of predicted peak expiratory flow rates than those from nonsmoking households (83% vs 98%).

CONCLUSIONS

Three- to 12-year-olds who are null for GSTM1 or homozygous for the GSTP1Val105 allele are more susceptible to asthma associated with environmental tobacco smoke exposure than those with more intact glutathione S-transferase status. In the 13- to 21-year-olds, GSTM1-null status interacts with environmental tobacco smoke exposure to substantially reduce peak expiratory flow rate. The environmental tobacco smoke effect in GSTM1-null children with asthma could be cumulative over time, resulting in detrimental effects on peak expiratory flow rate in 13- to 21-year-olds with asthma.

Relevance of the deletion polymorphisms of the glutathione S-transferases GSTT1 and GSTM1 in pharmacology and toxicology

Although cytosolic glutathione S-transferase (GST) enzymes occupy a key position in biological detoxification processes, two of the most relevant human isoenzymes, GSTT1-1 and GSTM1-1, are genetically deleted (non-functional alleles GSTT1*0 and GSTM1*0) in a high percentage of the human population, with major ethnic differences. The structures of the GSTT and GSTM gene areas explain the underlying genetic processes. GSTT1-1 is highly conserved during evolution and plays a major role in phase-II biotransformation of a number of drugs and industrial chemicals, e.g. cytostatic drugs, hydrocarbons and halogenated hydrocarbons. GSTM1-1 is particularly relevant in the deactivation of carcinogenic intermediates of polycyclic aromatic hydrocarbons. Several lines of evidence suggest that hGSTT1-1 and/or hGSTM1-1 play a role in the deactivation of reactive oxygen species that are likely to be involved in cellular processes of inflammation, ageing and degenerative diseases. There is cumulating evidence that combinations of the GSTM1*0 state with other genetic traits affecting the metabolism of carcinogens (CYP1A1, GSTP1) may predispose the aero-digestive tract and lung, especially in smokers, to a higher risk of cancer. The GSTM1*0 status appears also associated with a modest increase in the risk of bladder cancer, consistent with a GSTM1 interaction with carcinogenic tobacco smoke constituents. Both human GST deletions, although largely counterbalanced by overlapping substrate affinities within the GST superfamily, have consequences when the organism comes into contact with distinct man-made chemicals. This appears relevant in industrial toxicology and in drug metabolism.

GSTM1 and GSTP1 and respiratory health in asthmatic children exposed to ozone

Acute exposure to ozone has been related to a wide spectrum of health effects in susceptible individuals. Genetic factors may influence interindividual variation in ozone response. The current authors investigated the relationships between common polymorphisms in two genes involved in response to oxidative stress, i.e. glutathione S-transferases M1 (GSTM1) and P1 (GSTP1), and both respiratory symptoms and lung function in response to ozone among childhood asthmatics. A total of 151 asthmatic children, who were participants in a randomised controlled trial of antioxidant vitamin supplementation in Mexico City, were studied. Children were genotyped using PCR methods and followed from October 1998-April 2000. Increases in reported breathing difficulty were associated with ozone exposure in children with GSTM1 null (8%, 95% confidence interval (CI) 1-15%, per 20-ppb increase in 1-h maximum daily average over 7 days) or GSTP1 Valine/Valine (Val/Val) genotypes (14%, 95% CI 5-25%). In children with both GSTM1 null and GSTP1 Val/Val genotypes, the increase in breathing difficulty associated with a 20-ppb increase in ozone exposure was even greater (21%, 95% CI 5-39%). GSTP1 genotypes were not significantly associated with ozone-related lung function changes. In conclusion, asthmatic children with glutathione S-transferase M1 null and glutathione S-transferase P1 Valine/Valine genotypes appear more susceptible to developing respiratory symptoms related to ozone exposure.

Functional characterisation of ganglioside-induced differentiation-associated protein 1 as a glutathione transferase

Mutations in the ganglioside-induced differentiation-associated protein 1 (GDAP1) gene have been linked with Charcot-Marie-Tooth (CMT) disease. This protein, and its paralogue GDAP1L1, appear to be structurally related to the cytosolic glutathione S-transferases (GST) including an N-terminal thioredoxin fold domain with conserved active site residues. The specific function, of GDAP1 remains unknown. To further characterise their structure and function we purified recombinant human GDAP1 and GDAP1L1 proteins using bacterial expression and immobilised metal affinity chromatography. Like other cytosolic GSTs, GDAP1 protein has a dimeric structure. Although the full-length proteins were largely insoluble, the deletion of a proposed C-terminal transmembrane domain allowed the preparation of soluble protein. The purified proteins were assayed for glutathione-dependent activity against a library of 'prototypic' GST substrates. No evidence of glutathione-dependent activity or an ability to bind glutathione immobilised on agarose was found.

Isolation and characterization of OsGSTL1 promoter from rice

OsGSTL1 gene was isolated from the rice genomic library. Semi-quantitative RT-PCR analysis demonstrated that the expression of the OsGSTL1 in rice was not induced by chlorsulfuron, ethylene, abscisic acid, salicylic acid, and methyl jasmonate. In order to investigate the cis-elements of OsGSTL1 promoter, the promoter regions with different lengths were fused to the beta-glucuronidase (GUS) reporter gene. All constructs were transformed into onion epidermal cells or A. thaliana plants to detect the expression patterns. In onion epidermal cells, the 160 bp fragment and longer ones were functional for directing GUS expression. In transgenic A. thaliana, the 2,155 bp upstream region of OsGSTL1 gene directed the GUS expression only in cotyledon after germination, but not in the root of young seedlings. In the later seedling, the 2,155 bp upstream region of OsGSTL1 gene directed GUS expression in roots, stems, and leaves. However, the GUS gene directed by a 1,224 bp upstream fragment is expressed in all the checked tissues. These results suggest that the spatiotemporal expression response elements of OsGSTL1 existed in the 5'-upstream region between -2,155 and -1,224 bp.

Biotransformation of Glyceryl Trinitrate by Rat Hepatic Microsomal GlutathioneS-Transferase 1

Although the biotransformation of organic nitrates by the cytosolic glutathione S-transferases (GSTs) is well known, the relative contribution of the microsomal GST (MGST1) to nitrate biotransformation has not been described. We therefore compared the denitration of glyceryl trinitrate (GTN) by purified rat liver MGST1 and cytosolic GSTs. Both MGST1 and cytosolic GSTs catalyzed the denitration of GTN, but the activity of MGST1 toward GTN was 2- to 3-fold higher. To mimic oxidative/nitrosative stress in vitro, we treated enzyme preparations with hydrogen peroxide, S-nitrosoglutathione, and peroxynitrite. Both oxidants and nitrating reagents increased the activity of MGST1 toward the GST substrate, 1-chloro-2,4-dinitrobenzene (CDNB) whereas these treatments inhibited GTN denitration by MGST1. Alkylation of the sole cysteine residue of MGST1 by N-ethylmaleimide markedly increased enzyme activity with CDNB as substrate but decreased the rate of GTN denitration. In aortic microsomes from GTN-tolerant animals, there was a decreased abundance of MGST1 dimers and trimers. In hepatic microsomes from GTN-tolerant animals, GTN biotransformation was unaltered whereas the rate of CDNB conjugation was doubled, suggesting that chronic GTN exposure causes structural modifications to the enzyme, resulting in increased activity to certain substrates. Collectively, these data indicate that MGST1 contributes significantly to the biotransformation of GTN and that chemical modification of the microsomal enzyme has differential effects on the catalytic activity toward different substrates.

Regulatory and functional interactions of plant growth regulators and plant glutathione S-transferases (GSTs)

Plant glutathioneS-transferases (GSTs) are a heterogeneous superfamily of multifunctional proteins, grouped into six classes. The tau (GSTU) and phi (GSTF) class GSTs are the most represented ones and are plant-specific, whereas the smaller theta (GSTT) and zeta (GSTZ) classes are also found in animals. The lambda GSTs (GSTL) and the dehydroascorbate reductases (DHARs) are more distantly related. Plant GSTs perform a variety of pivotal catalytic and non-enzymatic functions in normal plant development and plant stress responses, roles that are only emerging. Catalytic functions include glutathione (GSH)-conjugation in the metabolic detoxification of herbicides and natural products. GSTs can also catalyze GSH-dependent peroxidase reactions that scavenge toxic organic hydroperoxides and protect from oxidative damage. GSTs can furthermore catalyze GSH-dependent isomerizations in endogenous metabolism, exhibit GSH-dependent thioltransferase safeguarding protein function from oxidative damage and DHAR activity functioning in redox homeostasis. Plant GSTs can also function as ligandins or binding proteins for phytohormones (i.e., auxins and cytokinins) or anthocyanins, thereby facilitating their distribution and transport. Finally, GSTs are also indirectly involved in the regulation of apoptosis and possibly also in stress signaling. Plant GST genes exhibit a diversity of expression patterns during biotic and abiotic stresses. Stress-induced plant growth regulators (i.e., jasmonic acid [JA], salicylic acid [SA], ethylene [ETH], and nitric oxide [NO] differentially activate GST gene expression. It is becoming increasingly evident that unique combinations of multiple, often interactive signaling pathways from various phytohormones and reactive oxygen species or antioxidants render the distinct transcriptional activation patterns of individual GSTs during stress. Underestimated post-transcriptional regulations of individual GSTs are becoming increasingly evident and roles for phytohormones (i.e., ABA and JA) in these processes are being anticipated as well. Finally, indications are emerging that NO may regulate the activity of specific plant GSTs. In this review, the current knowledge on the regulatory and functional interactions of phytohormones and plant GSTs are covered. We refer to a previous extensive review on plant GSTs (Marrs, 1996) for most earlier work. An introduction on the classification and roles of plant GSTs is included here, but these topics are more extensively discussed in other reviews (Dixon et al., 2002a; Edwards et al., 2000; Frova, 2003).

[Mode of inheritance of temephos (Abate) resistance in Aedes aegypti (Diptera: Culicidae) from Cuba]

A study on the mode of inheritance of temephos resistance was conducted using a temephos resistant Aedes aegypti reference strain (SAN-F6) with a value of resistance factor of 200x, compared with the insecticide susceptible Aedes aegypti strain (ROCKEFELLER). Genetic crossings were performed between temephos resistant and susceptible strains. An F1 crossing was attained. The females of this F1 crossing were crossed with males from the ROCKEFELLER strain (retrocrossing), and it was found that the temephos resistance was inherited in a semidominant way and as a monofactorial trait. The activity of Est-A4 observed in the polyacrylamide gel electrophoresis and measured by biochemical assays was higher in the strain resistant to temephos (SAN-F6), lower in the susceptible strain (ROCKEFELLER), and intermediate in the crossing of these two strains. A lower effect of the resistant parental strain was observed in the retrocrossing, both in the mortality with temephos and in the activity of Est. A4. These results suggest that the esterase activity may also be inherited, as well as the resistance to temephos, as a semidominant character.

Several glutathione S-transferase isozymes that protect against oxidative injury are expressed in human liver mitochondria

The mitochondrial environment is rich in reactive oxygen species (ROS) that may ultimately peroxidize membrane proteins and generate unsaturated aldehydes such as 4-hydroxy-2-nonenal (4HNE). We had previously demonstrated the presence of hGSTA4-4, an efficient catalyst of 4HNE detoxification, in human liver mitochondria to the exclusion of the cytosol. In the present study, GSH-affinity chromatography was used in conjunction with biochemical and proteomic analysis to determine the presence of additional cytosolic glutathione S-transferases (GSTs) in human hepatic mitochondria. HPLC-subunit analysis of GSH affinity-purified liver mitochondrial proteins indicated the presence of several potential mitochondrial GST isoforms. Electrospray ionization-mass spectrometry analysis of eluted mitochondrial GST subunits yielded molecular masses similar to those of hGSTP1, hGSTA1 and hGSTA2. Octagonal matrix-assisted laser desorption/ionization time of flight mass spectrometry and proteomics analysis using MS-FIT confirmed the presence of these three GST subunits in mitochondria, and HPLC analysis indicated that the relative contents of the mitochondrial GST subunits were hGSTA1>hGSTA2>hGSTP1. The mitochondrial localization of the alpha and pi class GST subunits was consistent with immunoblotting analysis of purified mitochondrial GST. Enzymatic studies using GSH-purified mitochondrial GST fractions demonstrated the presence of significant GST activity using the nonspecific GST substrate 1-chloro-2,4-dinitrobenzene (CDNB), as well as 4HNE, delta(5)-androstene-3,17-dione (ADI), and cumene hydroperoxide (CuOOH). Interestingly, the specific mitochondrial GST activities toward 4HNE, a highly toxic alpha,beta-unsaturated aldehyde produced during the breakdown of membrane lipids, exceeded that observed in liver cytosol. These observations are suggestive of a role of GST in protecting against mitochondrial injury during the secondary phase of oxidative stress, or modulation of 4HNE-mediated mitochondrial signaling pathways. However, other properties of mitochondrial GST, such as conjugation of environmental chemicals and binding of lipophilic non-substrate xenobiotics and endogenous compounds, remain to be investigated.

Axonal transport, amyloid precursor protein, kinesin-1, and the processing apparatus: revisited

The sequential enzymatic actions of beta-APP cleaving enzyme 1 (BACE1), presenilins (PS), and other proteins of the gamma-secretase complex liberate beta-amyloid (Abeta) peptides from larger integral membrane proteins, termed beta-amyloid precursor proteins (APPs). Relatively little is known about the normal function(s) of APP or the neuronal compartment(s) in which APP undergoes proteolytic processing. Recent studies have been interpreted as consistent with the idea that APP serves as a kinesin-1 cargo receptor and that PS and BACE1 are associated with the APP-resident membranous cargos that undergo rapid axonal transport. In this report, derived from a collaboration among several independent laboratories, we examined the potential associations of APP and kinesin-1 using glutathione S-transferase pull-down and coimmunoprecipitation assays. In addition, we assessed the trafficking of membrane proteins in the sciatic nerves of transgenic mice with heterozygous or homozygous deletions of APP. In contrast to previous reports, we were unable to find evidence for direct interactions between APP and kinesin-1. Furthermore, the transport of kinesin-1 and tyrosine kinase receptors, previously reported to require APP, was unchanged in axons of APP-deficient mice. Finally, we show that two components of the APP proteolytic machinery, i.e., PS1 and BACE1, are not cotransported with APP in the sciatic nerves of mice. These findings suggest that the hypothesis that APP serves as a kinesin-1 receptor and that the proteolytic processing machinery responsible for generating Abeta is transported in the same vesicular compartment in axons of peripheral nerves requires revision.

Glutathione S-transferase M1, T1, and P1 polymorphisms and prostate cancer risk in middle-aged men

BACKGROUND

The glutathione S-transferase (GST) enzymes detoxify several carcinogens. Genetic polymorphisms in GSTM1, T1, and P1 (Ile105Val) have been associated with prostate cancer, however, results have been inconsistent across studies.

METHODS

Data from a population-based case-control study in King County, Washington, were used to further evaluate the relationships between these GST polymorphisms and prostate cancer. Incident cases (n = 590) were 40-64 years old, diagnosed from 1993 through 1996, and identified via the SEER cancer registry. Controls (n = 538) were identified via random digit dialing, and frequency age-matched to cases. Logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

Risk of prostate cancer was moderately increased among Caucasians with the GSTM1-null genotype (OR = 1.54; 95% CI 1.19-2.01). There were no associations for either GSTT1 or P1(Ile105Val). The association between the GSTM1-null genotype and prostate cancer was not different according to cancer aggressiveness defined by stage at diagnosis and Gleason score. Among GSTM1-null Caucasians, the relative risk of prostate cancer increased linearly with increasing pack-years of smoking (P-value for trend = 0.007), with the highest ORs observed for smokers of >30 pack-years.

CONCLUSIONS

Findings suggest that the GSTM1-null genotype defines a subgroup of men at higher risk of prostate cancer, particularly if they are heavy smokers.

Glutathione transferases: new functions

Well known as detoxification enzymes, the glutathione transferases also function in prostaglandin and steroid hormone synthesis. New uses for the canonical glutathione transferase fold are becoming apparent; the bacterial stringent starvation protein SspA and the yeast prion protein Ure2p (both transcription factors) were found to adopt this fold, but their roles remain unclear. The intracellular chloride ion channel CLIC1 adopts the canonical glutathione transferase fold in its soluble form and appears to undergo radical structural modification as part of its membrane insertion process. The structures of rat and human mitochondrial glutathione transferases have been solved: they adopt a topology similar to that of bacterial disulfide bond isomerases, leading to the suggestion that they have evolved independently of the canonical enzymes. Recent structural studies of integral membrane glutathione S-transferases from microsomes have revealed common patterns of tertiary and quaternary structure.

Evaluation of the association between null genotypes of glutathione-S-transferases and Behcet’s disease

Glutathione S-transferases (GST) play an important role in oxidative stress related syndromes. An imbalance of the oxidant and antioxidant systems is important in the pathogenesis of Behcet's disease (BD). The objective of this study was to evaluate the association of null genotypes of GST-M1 and GST-T1 with BD since some preliminary molecular genetic data were recently published. Ninety-four Turkish BD patients (42 male, 52 female, 37.1+/-10.4 years) and 140 healthy volunteers (70 male, 70 female, 36.8+/-11.7 years) matched for age and gender with the patients as the control group were included in the study. Distributions of GST-M1 and GST-T1 genotypes were determined by multiplexed PCR using three sets of primers for GST-M1, GST-T1, and beta-globulin genes. There was no association between BD and the frequencies of GST-M1 and GST-T1 null genotypes when compared to controls by separate analysis. However, by cross and pooled combination analysis there was a significant association between the frequencies of pooled GSTs with one or both null genotypes in BD and controls. This is the first evidence that the association between the frequencies of GST-M1 and GST-T1 null genotypes and BD might be dependent on the interaction of multiple null allele polymorphisms rather than a single null allele of GST-M1 and GST-T1.