Human microsomal prostaglandin E synthase 1: a member of the MAPEG protein superfamily

Caveolin-1β promotes the production of active human microsomal glutathione S-transferase in induced intracellular vesicles inSpodoptera frugiperda21 insect cells

The heterologous expression in Spodoptera frugiperda 21 (Sf21) insect cells of the β isoform of canine caveolin-1 (caveolin-1β), using a baculovirus-based vector, resulted in intracellular vesicles enriched in caveolin-1β. We investigated whether these vesicles could act as membrane reservoirs, and promote the production of an active membrane protein (MP) when co-expressed with caveolin-1β. We chose hMGST1 (human microsomal glutathione S-transferase 1) as the co-expressed MP. It belongs to the membrane-associated proteins in eicosanoid and glutathione metabolism (MAPEG) family of integral MPs, and, as a phase II detoxification enzyme, it catalyzes glutathione conjugation of lipophilic drugs present in the lipid membranes. In addition to its pharmaceutical interest, its GST activity can be conveniently measured. The expression of both MPs were followed by Western blots and membrane fractionation on density gradient, and their cell localization by immunolabeling and transmission electron microscopy. We showed that caveolin-1β kept its capacity to induce intracellular vesicles in the host when co-expressed with hMGST1, and that hMGST1 is in part addressed to these vesicles. Remarkably, a fourfold increase in the amount of active hMGST1 was found in the most enriched membrane fraction, along with an increase of its specific activity by 60% when it was co-expressed with caveolin-1β. Thus, heterologously expressed caveolin-1β was able to induce cytoplasmic vesicles in which a co-expressed exogenous MP is diverted and sequestered, providing a favorable environment for this cargo.

Glutathione-S-transferase alpha-4 in Hippocampus abdominalis (big-belly seahorse): Molecular characterization, antioxidant properties, and its potent immune response

Glutathione-S-transferase (GST) is a key enzyme in the phase-II detoxification process and is a biomarker of oxidative stress. In this study, we analyzed the molecular, biochemical, and antioxidant properties of GST alpha-4 from Hippocampus abdominalis (HaGSTA-4). Also, the spatial and temporal expression of HaGSTA-4 upon immune challenge with abiotic and biotic stimulants were evaluated. The HaGSTA-4 ORF encodes 223 amino acids with a molecular weight of 25.7 kDa, and an estimated isoelectric point (pI) of 8.47. It consists of the GST_C superfamily and thioredoxin-like superfamily domain. The phylogenetic tree revealed that HaGSTA-4 is evolutionarily conserved with its GST alpha class counterparts. From pairwise alignment, the highest values of identity (78.5%) and similarity (85.7%) were with Parambassis ranga GSTA-4. Protein rHaGSTA-4 exhibited the highest conjugation activity towards 1-chloro-2,4-dinitrobenzene (CDNB) at pH 7 and 20 °C. A disk diffusion assay showed that rHaGSTA-4 significantly protects cells from the stress of exposure to ROS inducers such as CuSO₄, CdCl₂, and ZnCl₂. Furthermore, overexpressed HaGSTA-4 defended cells against oxidative stress caused by H₂O₂; evidence of selenium-independent peroxidase activity. From qPCR, the tissue-specific expression profile demonstrates that HaGSTA-4 is most highly expressed in the kidney, followed by the intestine and stomach, among fourteen different tissues extracted from healthy seahorses. The mRNA expression profile of HaGSTA-4 upon immune challenge varied depending on the tissue and the time after challenge. Altogether, this study suggests that HaGSTA-4 may be involved in protection against oxidative stress, in immune defense regulation, and xenobiotic metabolism.

The glutathione S-transferase genes in marine rotifers and copepods: Identification of GSTs and applications for ecotoxicological studies

Various xenobiotics are constantly being released and accumulated into the aquatic environments and consequently, the aquatic organisms are continuously being exposed to exogenous stressors. Among various xenobiotic detoxifying enzymes, Glutathione S-transferase (GST) is one of the major xenobiotic detoxifying enzyme which is widely distributed among living organisms and thus, understanding of the nature of GSTs is crucial. Previous studies have shown GST activity in response to various xenobiotics yet, full identification of GSTs in marine invertebrates is still limited. This review covers information on the importance of GSTs as a biomarker for emerging chemicals and their response to wide ranges of environmental pollutants as well as in-depth phylogenetic analysis of marine invertebrates, including recently identified GSTs belonging to rotifers (Brachionus spp.) and copepods (Tigriopus japonicus and Paracyclopina nana), with unique class-specific features of GSTs, as well as a new suggestion of GST evolutionary pathway.

The enzymology of the human prostanoid pathway

Prostanoids are short-lived autocrine and paracrine signaling molecules involved in a wide range of biological functions. They have been shown to be intimately involved in many different disease states when their regulation becomes dysfunctional. In order to fully understand the progression of any disease state or the biological functions of the well state, a complete evaluation of the genomics, proteomics, and metabolomics of the system is necessary. This review is focused on the enzymology for the enzymes involved in the synthesis of the prostanoids (prostaglandins, prostacyclins and thromboxanes). In particular, the isolation and purification of the enzymes, their enzymatic parameters and catalytic mechanisms are presented.

The mercapturic acid pathway

The mercapturic acid pathway is a major route for the biotransformation of xenobiotic and endobiotic electrophilic compounds and their metabolites. Mercapturic acids (N-acetyl-l-cysteine S-conjugates) are formed by the sequential action of the glutathione transferases, γ-glutamyltransferases, dipeptidases, and cysteine S-conjugate N-acetyltransferase to yield glutathione S-conjugates, l-cysteinylglycine S-conjugates, l-cysteine S-conjugates, and mercapturic acids; these metabolites constitute a "mercapturomic" profile. Aminoacylases catalyze the hydrolysis of mercapturic acids to form cysteine S-conjugates. Several renal transport systems facilitate the urinary elimination of mercapturic acids; urinary mercapturic acids may serve as biomarkers for exposure to chemicals. Although mercapturic acid formation and elimination is a detoxication reaction, l-cysteine S-conjugates may undergo bioactivation by cysteine S-conjugate β-lyase. Moreover, some l-cysteine S-conjugates, particularly l-cysteinyl-leukotrienes, exert significant pathophysiological effects. Finally, some enzymes of the mercapturic acid pathway are described as the so-called "moonlighting proteins," catalytic proteins that exert multiple biochemical or biophysical functions apart from catalysis.

Regulation of Eicosanoid Pathways by MicroRNAs

Over the last years, many microRNAs (miRNAs) have been identified that regulate the formation of bioactive lipid mediators such as prostanoids and leukotrienes. Many of these miRNAs are involved in complex regulatory circuits necessary for the fine-tuning of biological functions including inflammatory processes or cell growth. A better understanding of these networks will contribute to the development of novel therapeutic strategies for the treatment of inflammatory diseases and cancer. In this review, we provide an overview of the current knowledge of miRNA regulation in eicosanoid pathways with special focus on novel miRNA functions and regulatory circuits of leukotriene and prostaglandin biosynthesis.

Glutathione transferases: substrates, inihibitors and pro-drugs in cancer and neurodegenerative diseases

Glutathione transferase classical GSH conjugation activity plays a critical role in cellular detoxification against xenobiotics and noxious compounds as well as against oxidative stress. However, this feature is also exploited by cancer cells to acquire drug resistance and improve their survival. As a result, various members of the family were found overexpressed in a number of different cancers. Moreover several GST polymorphisms, ranging from null phenotypes to point mutations, were detected in members of the family and found to correlate with the onset of neuro-degenerative diseases. In the last decades, a great deal of research aimed at clarifying the role played by GSTs in drug resistance, at developing inhibitors to counteract this activity but also at exploiting GSTs for prodrugs specific activation in cancer cells. Here we summarize some of the most important achievements reached in this lively area of research.

Microsomal prostaglandin e synthase-1 in rheumatic diseases

Microsomal prostaglandin E synthase-1 (mPGES-1) is a well-recognized target for the development of novel anti-inflammatory drugs that can reduce symptoms of inflammation in rheumatic diseases and other inflammatory conditions. In this review, we focus on mPGES-1 in rheumatic diseases with the aim to cover the most recent advances in the understanding of mPGES-1 in rheumatoid arthritis, osteoarthritis, and inflammatory myopathies. Novel findings regarding regulation of mPGES-1 cell expression as well as enzyme inhibitors are also summarized.

Prostaglandin E2 synthases in neurologic homeostasis and disease

Prostaglandin E(2) synthases (PGES) currently comprise a group of three structurally and biologically distinct molecules. These enzymes are part of an important and complex paracrine signaling system involved in a wide range of biological processes. This review focuses on the normal physiological and pathological roles of these enzymes in the nervous system. Specific topics include the role of PGES(s) in fever and sickness behavior, inflammatory pain, and neural disease. Although the field is in its early stages, ongoing development of selective PGES inhibitors for possible use in people creates a significant need for more fully understanding the biological roles of these important enzymes.

Inhibition of lipoxygenases and cyclooxygenases by linoleyl hydroxamic acid: comparative in vitro studies

In this first comparative in vitro study, linoleyl hydroxamic acid (LHA), a simple and stable derivative of linoleic acid, was tested as an inhibitor of several enzymes involved in arachidonic acid metabolism in mammals. The tested enzymes were human recombinant 5-lipoxygenase (h5-LO), porcine leukocyte 12-LO, rabbit reticulocyte 15-LO, ovine cyclooxygenases 1/2 (COX1/COX2), and human microsomal prostaglandin E synthase-1 (mPGES-1). Potato tuber and soybean lipoxygenases (ptLOX and sLOX, respectively) were studied for comparative purposes. LHA inhibited most of the tested enzymes with the exception of mPGES-1. The LHA inhibitory activity increased as follows: mPGES-1 (no inhibition)<<COX1 = COX2<h5-LO = sLOX = ptLOX<12-LO<<15-LO. The IC(50) values for COX1/COX2, h5-LO, 12-LO, and 15-LO were 60, 7, 0.6, and 0.02 muM, respectively. sLOX was the only tested enzyme that was capable of aerobic oxygenation of LHA, producing 13-hydroperoxy-LHA. The enzyme rapidly inactivated during the reaction. Therefore, LHA could be used as an effective LO/LOX inhibitor without affecting COX1/COX2 and mPGES-1. Possible implications of this observation include treating diseases and pathological states that are caused by (or lead to) hyperproduction of LO-derived metabolites, e.g., inflammation, cardiovascular disorders, cancer, asthma, allergies, psoriasis, and stroke.

The chemical defensome: environmental sensing and response genes in the Strongylocentrotus purpuratus genome

Metazoan genomes contain large numbers of genes that participate in responses to environmental stressors. We surveyed the sea urchin Strongylocentrotus purpuratus genome for homologs of gene families thought to protect against chemical stressors; these genes collectively comprise the 'chemical defensome.' Chemical defense genes include cytochromes P450 and other oxidases, various conjugating enzymes, ATP-dependent efflux transporters, oxidative detoxification proteins, and transcription factors that regulate these genes. Together such genes account for more than 400 genes in the sea urchin genome. The transcription factors include homologs of the aryl hydrocarbon receptor, hypoxia-inducible factor, nuclear factor erythroid-derived 2, heat shock factor, and nuclear hormone receptors, which regulate stress-response genes in vertebrates. Some defense gene families, including the ABCC, the UGT, and the CYP families, have undergone expansion in the urchin relative to other deuterostome genomes, whereas the stress sensor gene families do not show such expansion. More than half of the defense genes are expressed during embryonic or larval life stages, indicating their importance during development. This genome-wide survey of chemical defense genes in the sea urchin reveals evolutionary conservation of this network combined with lineage-specific diversification that together suggest the importance of these chemical stress sensing and response mechanisms in early deuterostomes. These results should facilitate future studies on the evolution of chemical defense gene networks and the role of these networks in protecting embryos from chemical stress during development.