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Andreou A, Göbel C, Hamberg M, Feussner I. A bisallylic mini-lipoxygenase from cyanobacterium Cyanothece sp. that has an iron as cofactor. J Biol Chem 2010; 285:14178-86. [PMID: 20223828 DOI: 10.1074/jbc.m109.094771] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Lipoxygenases are enzymes that are found ubiquitously in higher animals and plants, but have only recently been identified in a number of bacteria. The genome of the diazotrophic unicellular cyanobacterium Cyanothece sp. harbors two genes with homology to lipoxygenases. Here we describe the isolation of one gene, formerly named csplox2. It was cloned, and the protein was expressed in Escherichia coli and purified. The purified enzyme belongs to the group of prokaryotic mini lipoxygenases, because it had a molecular mass of 65 kDa. Interestingly, it catalyzed the conversion of linoleic acid, the only endogenously found polyunsaturated fatty acid, primarily to the bisallylic hydroperoxide 11R-hydroperoxyoctadecadienoic acid. This product had previously only been described for the manganese lipoxygenase from the take all fungus, Gaeumannomyces graminis. By contrast, CspLOX2 was shown to be an iron lipoxygenase. In addition, CspLOX2 formed a mixture of typical conjugated lipoxygenase products, e.g. 9R- and 13S-hydroperoxide. The conversion of linoleic acid took place with a maximum reaction rate of 31 s(-1). Incubation of the enzyme with [(11S)-(2)H]linoleic acid led to the formation of hydroperoxides that had lost the deuterium label, thus suggesting that CspLOX2 catalyzes antarafacial oxygenation as opposed to the mechanism of manganese lipoxygenase. CspLOX2 could also oxidize diarachidonylglycerophosphatidylcholine with similar specificity as the free fatty acid, indicating that binding of the substrate takes place with a "tail-first" orientation. We conclude that CspLOX2 is a novel iron mini-lipoxygenase that catalyzes the formation of bisallylic hydroperoxide as the major product.
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Affiliation(s)
- Alexandra Andreou
- Department of Plant Biochemistry, Albrecht von Haller Institute for Plant Sciences, Georg August University, Justus-von-Liebig-Weg 11, D-37077 Göttingen, Germany
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Nair DG, Funk CD. A cell-based assay for screening lipoxygenase inhibitors. Prostaglandins Other Lipid Mediat 2009; 90:98-104. [PMID: 19804839 DOI: 10.1016/j.prostaglandins.2009.09.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2009] [Revised: 09/21/2009] [Accepted: 09/24/2009] [Indexed: 12/11/2022]
Abstract
Lipoxygenases (LOX) form a family of lipid peroxidizing enzymes within the plant and animal kingdoms. In humans, six functional lipoxygenase isoforms have been identified. 5-LOX, "platelet-type" 12-LOX (p12-LOX) and 15-LOX type 1 (15-LOX1), originally identified in leukocytes, platelets, and reticulocytes, respectively, generate lipid mediators involved in host cellular functions and in the pathophysiology of asthma, cardiovascular diseases, and cancer. The pharmaceutical industry has reinvigorated their programs to develop novel LOX inhibitors in view of recent findings. However, high throughput LOX screening assays to test novel agents against these intracellular enzymes are limited. We describe a cell-based 96-well microplate fluorescence assay tested against several existing LOX inhibitors, and validate the assay by comparing known IC(50) values and HPLC analysis, which may provide a useful screen for novel LOX inhibitors.
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Affiliation(s)
- Dileep G Nair
- Department of Physiology and Biochemistry, Queen's University, Kingston, ON, Canada
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Abstract
The small GTPase Rab6 regulates vesicle trafficking at the level of Golgi. Recently, the crystal structures of Rab6 in complexes with two unrelated effectors have been determined. The structure of Rab6a-GTP in complex with a 378-residue internal fragment of the effector Rab6IP1 (Rab6-interacting protein 1) has been solved. In addition, the structure of Rab6 with the golgin, GCC185, has also been determined. In both complexes, two α-helices from the effector mediate binding to switch I, switch II and the interswitch region of Rab6. Comparisons of the complexes reveal significant conformational changes in the conserved hydrophobic triad of Rab6. Thus conformational flexibility in the triad mediates recognition of compositionally distinct α-helical coiled coils, providing a rationale for the promiscuity of Rab6 in effector recruitment.
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Grillet N, Schwander M, Hildebrand MS, Sczaniecka A, Kolatkar A, Velasco J, Webster JA, Kahrizi K, Najmabadi H, Kimberling WJ, Stephan D, Bahlo M, Wiltshire T, Tarantino LM, Kuhn P, Smith RJ, Müller U. Mutations in LOXHD1, an evolutionarily conserved stereociliary protein, disrupt hair cell function in mice and cause progressive hearing loss in humans. Am J Hum Genet 2009; 85:328-37. [PMID: 19732867 PMCID: PMC2771534 DOI: 10.1016/j.ajhg.2009.07.017] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2009] [Revised: 07/22/2009] [Accepted: 07/27/2009] [Indexed: 11/23/2022] Open
Abstract
Hearing loss is the most common form of sensory impairment in humans and is frequently progressive in nature. Here we link a previously uncharacterized gene to hearing impairment in mice and humans. We show that hearing loss in the ethylnitrosourea (ENU)-induced samba mouse line is caused by a mutation in Loxhd1. LOXHD1 consists entirely of PLAT (polycystin/lipoxygenase/alpha-toxin) domains and is expressed along the membrane of mature hair cell stereocilia. Stereociliary development is unaffected in samba mice, but hair cell function is perturbed and hair cells eventually degenerate. Based on the studies in mice, we screened DNA from human families segregating deafness and identified a mutation in LOXHD1, which causes DFNB77, a progressive form of autosomal-recessive nonsyndromic hearing loss (ARNSHL). LOXHD1, MYO3a, and PJVK are the only human genes to date linked to progressive ARNSHL. These three genes are required for hair cell function, suggesting that age-dependent hair cell failure is a common mechanism for progressive ARNSHL.
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Affiliation(s)
- Nicolas Grillet
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Martin Schwander
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Michael S. Hildebrand
- Department of Otolaryngology—Head and Neck Surgery, University of Iowa City, IA 55242, USA
| | - Anna Sczaniecka
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Anand Kolatkar
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Janice Velasco
- Genome Institute of the Novartis Research Foundation, San Diego, CA 92121, USA
| | - Jennifer A. Webster
- Neurogenomics Division, Translational Genomics Research Institute, Phoenix, AZ 85004, USA
| | - Kimia Kahrizi
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Hossein Najmabadi
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | | | - Dietrich Stephan
- Genome Institute of the Novartis Research Foundation, San Diego, CA 92121, USA
- Arizona Alzheimer's Consortium, Phoenix, AZ 85004, USA
- Banner Alzheimer's Institute, Phoenix, AZ 85004, USA
| | - Melanie Bahlo
- Bioinformatics Division, The Walter and Eliza Hall Institute of Medical Research, Parkville 3052 VIC, Australia
| | - Tim Wiltshire
- Department of Psychiatry, University of North Carolina, Chapel Hill, NC 27516, USA
| | - Lisa M. Tarantino
- Department of Psychiatry, University of North Carolina, Chapel Hill, NC 27516, USA
| | - Peter Kuhn
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Richard J.H. Smith
- Department of Otolaryngology—Head and Neck Surgery, University of Iowa City, IA 55242, USA
| | - Ulrich Müller
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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Calandria JM, Marcheselli VL, Mukherjee PK, Uddin J, Winkler JW, Petasis NA, Bazan NG. Selective survival rescue in 15-lipoxygenase-1-deficient retinal pigment epithelial cells by the novel docosahexaenoic acid-derived mediator, neuroprotectin D1. J Biol Chem 2009; 284:17877-82. [PMID: 19403949 DOI: 10.1074/jbc.m109.003988] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The integrity of the retinal pigment epithelial (RPE) cell is essential for the survival of rod and cone photoreceptor cells. Several stressors, including reactive oxygen species, trigger apoptotic damage in RPE cells preceded by an anti-inflammatory, pro-survival response, the formation of neuroprotectin D1 (NPD1), an oxygenation product derived from the essential omega-3 fatty acid family member docosahexaenoic acid. To define the ability of NPD1 and other endogenous novel lipid mediators in cell survival, we generated a stable knockdown human RPE (ARPE-19) cell line using short hairpin RNA to target 15-lipoxygenase-1. The 15-lipoxygenase-1-deficient cells exhibited 30% of the protein expression, and 15-lipoxygenase-2 remained unchanged, as compared with an ARPE-19 cell line control established using nonspecific short hairpin RNA transfected cells. NPD1 synthesis was stimulated by tumor necrosis factor alpha/H2O2-mediated oxidative stress in nonspecific cells (controls), whereas in silenced cells, negligible amounts of NPD1, 12(S)- and 15(S)-hydroxyeicosatetraenoic acid, and lipoxin A4 were found under these conditions. Neither control nor the deficient cells showed an increase in 15-lipoxygenase-1 protein content after 16 h of oxidative stress, suggesting that the increased activity of 15-lipoxygenase-1 is due to activation of pre-existing proteins. 15-Lipoxygenase-silenced cells also displayed an exacerbated sensitivity to oxidative stress-induced apoptosis when compared with the control cells. NPD1 selectively and potently rescued 15-lipoxygenase-silenced cells from oxidative stress-induced apoptosis. These results demonstrate that 15-lipoxygenase-1 is activated by oxidative stress in ARPE-19 cells and that NPD1 is part of an early survival signaling in RPE cells.
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Affiliation(s)
- Jorgelina M Calandria
- Neuroscience Center of Excellence, Louisiana State University Health Sciences Center, School of Medicine, New Orleans, Louisiana 70112, USA
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Recacha R, Boulet A, Jollivet F, Monier S, Houdusse A, Goud B, Khan AR. Structural basis for recruitment of Rab6-interacting protein 1 to Golgi via a RUN domain. Structure 2009; 17:21-30. [PMID: 19141279 DOI: 10.1016/j.str.2008.10.014] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2008] [Revised: 10/12/2008] [Accepted: 10/15/2008] [Indexed: 12/31/2022]
Abstract
Small GTPase Rab6 regulates vesicle trafficking at the level of Golgi via recruitment of numerous and unrelated effectors. The crystal structure of Rab6a(GTP) in complex with a 378-residue internal fragment of the effector Rab6IP1 was solved at 3.2 angstroms resolution. This Rab6IP1 region encompasses an all alpha-helical RUN domain followed in tandem by a PLAT domain that adopts a beta sandwich fold. The structure reveals that the first and last alpha helices of the RUN domain mediate binding to switch I, switch II, and the interswitch region of Rab6. It represents the largest Rab-effector complex determined to date. Comparisons with the recent structure of Rab6 in complex with an unrelated effector, human golgin GCC185, reveals significant conformational changes in the conserved hydrophobic triad of Rab6. Flexibility in the switch and interswitch regions of Rab6 mediates recognition of compositionally distinct alpha-helical coiled coils, thereby contributing to Rab6 promiscuity in effector recruitment.
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Affiliation(s)
- Rosario Recacha
- School of Biochemistry and Immunology, Trinity College, Dublin 2, Ireland
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