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Empowerment of 15-Lipoxygenase Catalytic Competence in Selective Oxidation of Membrane ETE-PE to Ferroptotic Death Signals, HpETE-PE.

ABSTRACT: sn2-15-Hydroperoxy-eicasotetraenoyl-phosphatidylethanolamines ( sn2-15-HpETE-PE) generated by mammalian 15-lipoxygenase/phosphatidylethanolamine binding protein-1 (15-LO/PEBP1) complex is a death signal in a recently identified type of programmed cell demise, ferroptosis. How the enzymatic complex selects sn2-ETE-PE as the substrate among 1 of ?100 total oxidizable membrane PUFA phospholipids is a central, yet unresolved question. To unearth the highly selective and specific mechanisms of catalytic competence, we used a combination of redox lipidomics, mutational and computational structural analysis to show they stem from (i) reactivity toward readily accessible hexagonally organized membrane sn2-ETE-PEs, (ii) relative preponderance of sn2-ETE-PE species vs other sn2-ETE-PLs, and (iii) allosteric modification of the enzyme in the complex with PEBP1. This emphasizes the role of enzymatic vs random stochastic free radical reactions in ferroptotic death signaling.

SUBMITTER: Anthonymuthu TS

PROVIDER: S-EPMC6622169 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature

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Resolving the paradox of ferroptotic cell death: Ferrostatin-1 binds to 15LOX/PEBP1 complex, suppresses generation of peroxidized ETE-PE, and protects against ferroptosis.

Project description:Hydroperoxy-eicosatetraenoyl-phosphatidylethanolamine (HpETE-PE) is a ferroptotic cell death signal. HpETE-PE is produced by the 15-Lipoxygenase (15LOX)/Phosphatidylethanolamine Binding Protein-1 (PEBP1) complex or via an Fe-catalyzed non-enzymatic radical reaction. Ferrostatin-1 (Fer-1), a common ferroptosis inhibitor, is a lipophilic radical scavenger but a poor 15LOX inhibitor arguing against 15LOX having a role in ferroptosis. In the current work, we demonstrate that Fer-1 does not affect 15LOX alone, however, it effectively inhibits HpETE-PE production by the 15LOX/PEBP1 complex. Computational molecular modeling shows that Fer-1 binds to the 15LOX/PEBP1 complex at three sites and could disrupt the catalytically required allosteric motions of the 15LOX/PEBP1 complex. Using nine ferroptosis cell/tissue models, we show that HpETE-PE is produced by the 15LOX/PEBP1 complex and resolve the long-existing Fer-1 anti-ferroptotic paradox.

| S-EPMC7596334 | biostudies-literature

P. aeruginosa augments irradiation injury via 15-lipoxygenase-catalyzed generation of 15-HpETE-PE and induction of theft-ferroptosis.

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15-Lipoxygenase-1 biosynthesis of 7S,14S-diHDHA implicates 15-lipoxygenase-2 in biosynthesis of resolvin D5.

Project description:The two oxylipins 7S,14S-dihydroxydocosahexaenoic acid (diHDHA) and 7S,17S-diHDHA [resolvin D5 (RvD5)] have been found in macrophages and infectious inflammatory exudates and are believed to function as specialized pro-resolving mediators (SPMs). Their biosynthesis is thought to proceed through sequential oxidations of DHA by lipoxygenase (LOX) enzymes, specifically, by human 5-LOX (h5-LOX) first to 7(S)-hydroxy-4Z,8E,10Z,13Z,16Z,19Z-DHA (7S-HDHA), followed by human platelet 12-LOX (h12-LOX) to form 7(S),14(S)-dihydroxy-4Z,8E,10Z,12E,16Z,19Z-DHA (7S,14S-diHDHA) or human reticulocyte 15-LOX-1 (h15-LOX-1) to form RvD5. In this work, we determined that oxidation of 7(S)-hydroperoxy-4Z,8E,10Z,13Z,16Z,19Z-DHA to 7S,14S-diHDHA is performed with similar kinetics by either h12-LOX or h15-LOX-1. The oxidation at C14 of DHA by h12-LOX was expected, but the noncanonical reaction of h15-LOX-1 to make over 80% 7S,14S-diHDHA was larger than expected. Results of computer modeling suggested that the alcohol on C7 of 7S-HDHA hydrogen bonds with the backbone carbonyl of Ile399, forcing the hydrogen abstraction from C12 to oxygenate on C14 but not C17. This result raised questions regarding the synthesis of RvD5. Strikingly, we found that h15-LOX-2 oxygenates 7S-HDHA almost exclusively at C17, forming RvD5 with faster kinetics than does h15-LOX-1. The presence of h15-LOX-2 in neutrophils and macrophages suggests that it may have a greater role in biosynthesizing SPMs than previously thought. We also determined that the reactions of h5-LOX with 14(S)-hydroperoxy-4Z,7Z,10Z,12E,16Z,19Z-DHA and 17(S)-hydroperoxy-4Z,7Z,10Z,13Z,15E,19Z-DHA are kinetically slow compared with DHA, suggesting that these reactions may be minor biosynthetic routes in vivo. Additionally, we show that 7S,14S-diHDHA and RvD5 have anti-aggregation properties with platelets at low micromolar potencies, which could directly regulate clot resolution.

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Insulin-like growth factor I reduces lipid oxidation and foam cell formation via downregulation of 12/15-lipoxygenase.

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Project description:The purified 15-lipoxygenase from rabbit reticulocytes is capable of oxidizing NADH in the presence of linoleic acid and oxygen. This co-oxidation proceeds at a rate that amounts to approx. 7% of linoleic acid oxygenation rates. Although NADH inhibits the lipoxygenase reaction with linoleic acid as substrate (46% inhibition at 0.2 mM NADH), the reaction specificity of the enzyme was not altered since (13S)-hydroperoxy-(9Z,11E)-octadecadienoic acid was identified as the major reaction product. NADH oxidation was inhibited by NAD+ (uncompetitive with respect to linoleate and mixed/competitive with respect to NADH), and NADPH or NMNH could substitute for NADH with slightly different apparent Km values. NADH oxidation was enhanced at lower oxygen tension, but was completely prevented under anaerobic conditions. Computer-assisted modelling of 15-lipoxygenase/NADH interaction and sequence alignments of mammalian lipoxygenases with NADH-dependent enzymes suggested that there is no specific binding of the coenzyme at the putative fatty acid-binding site of lipoxygenases. These results suggest that NAD(P)H might be oxidized by a radical intermediate formed during the dioxygenase cycle of the lipoxygenase reaction but that NADH oxidation might not proceed at the active site of the enzyme. The mechanism and possible biological consequences of 15-lipoxygenase-catalysed NAD(P)H oxidation are discussed.

| S-EPMC1218782 | biostudies-other

Gene expression analysis of 15-Lipoxygenase 2 (15-LOX2) transgenic mice

Project description:15-Lipoxygenase 2 (15-LOX2), a human-specific lipid-peroxidizing enzyme, is mainly expressed in luminal compartment of the normal prostate and often decreased or lost in prostate cancer (PCa). Previous studies from our lab implicate 15-LOX2 as a functional tumor suppressor. To better understand the biological role of 15-LOX2 in vivo, we established prostate-specific 15-LOX2 transgenic mice using the ARR2PB promoter. Unexpectedly, 15-LOX2 expression resulted in age-dependent prostatic hyperplasia. Interestingly, transgenic expression of 15-LOX2sv-b, a splice variant that lacks the arachidonic acid metabolizing activity, also induced hyperplasia and enlargement of the prostate. Prostatic hyperplasia induced by both 15-LOX2 and 15-LOX2sv-b was associated with an increase in proliferative (i..e., Ki67+) and luminal cells but 15-LOX2-induced hyperplasia was also accompanied by a prominent increase in basal cells. Microarray analysis revealed distinct gene expression profiles that could help explain the prostate phenotypes. Strikingly, 15-LOX2 (but not 15-LOX2sv-b) transgenic prostate showed up-regulation of several well-known stem/progenitor cell molecules including Sca-1, Trop2, p63 and Psca. Prostatic hyperplasia caused by both 15-LOX2 and 15-LOX2sv-b did not progress to PCa over >5 years of observations. Mechanistically, hyperplastic prostate lobes (especially those of the 15-LOX2 mice) showed a dramatic increase in senescent cells revealed by increased SA-ßgal, HP1, and p27Kip1 staining. Collectively, our results suggest that 15-LOX2 expression in mouse prostate leads to hyperplasia that activates the senescence checkpoint, which may in turn function as a barrier to tumor development.

2010-12-16 | GSE15827 | GEO

Activity-Based Probes for 15-Lipoxygenase-1.

Project description:Human 15-lipoxygenase-1 (15-LOX-1) plays an important role in several inflammatory lung diseases, such as asthma, COPD, and chronic bronchitis, as well as various CNS diseases, such as Alzheimer's disease, Parkinson's disease, and stroke. Activity-based probes of 15-LOX-1 are required to explore the role of this enzyme further and to enable drug discovery. In this study, we developed a 15-LOX-1 activity-based probe for the efficient activity-based labeling of recombinant 15-LOX-1. 15-LOX-1-dependent labeling in cell lysates and tissue samples was also possible. To mimic the natural substrate of the enzyme, we designed activity-based probes that covalently bind to the active enzyme and include a terminal alkene as a chemical reporter for the bioorthogonal linkage of a detectable functionality through an oxidative Heck reaction. The activity-based labeling of 15-LOX-1 should enable the investigation and identification of this enzyme in complex biological samples, thus opening up completely new opportunities for drug discovery.

| S-EPMC5218545 | biostudies-literature

Molecular Targeting of 15-Lipoxygenase-1 (15-LOX-1) for Apoptosis Induction in Human Colorectal Cancers

Project description:Primary Objective: * To determine whether celecoxib downregulates GATA-6 expression to upregulate 15-LOX-1 expression and induce apoptosis in human rectal tumors, researchers will measure GATA-6 and 15-LOX-1 expression, 13-S-HODE levels, and apoptosis rates in normal and colorectal polyp epithelial tissues before and after 6 months of celecoxib treatment of patients with familial adenomatous polyposis (FAP).

| 2042215 | ecrin-mdr-crc

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