The Experts below are selected from a list of 88056 Experts worldwide ranked by ideXlab platform
Johnathan A Napier - One of the best experts on this subject based on the ideXlab platform.
-
an Alternative Pathway for the effective production of the omega 3 long chain polyunsaturates epa and eta in transgenic oilseeds
Plant Biotechnology Journal, 2015Co-Authors: Johnathan A Napier, Richard P Haslam, Noemi Ruizlopez, Sarah Usher, Olga SayanovaAbstract:The synthesis and accumulation of omega-3 long-chain polyunsaturated fatty acids in transgenic Camelina sativa is demonstrated using the so-called Alternative Pathway. This aerobic Pathway is found in a small number of taxonomically unrelated unicellular organisms and utilizes a C18 Δ9-elongase to generate C20 PUFAs. Here, we evaluated four different combinations of seed-specific transgene-derived activities to systematically determine the potential of this Pathway to direct the synthesis of eicosapentaenoic acid (EPA) in transgenic plants. The accumulation of EPA and the related omega-3 LC-PUFA eicosatetraenoic acid (ETA) was observed up to 26.4% of total seed fatty acids, of which ETA was 9.5%. Seed oils such as these not only represent an additional source of EPA, but also an entirely new source of the bona fide fish oil ETA. Detailed lipidomic analysis of the Alternative Pathway in Camelina revealed that the acyl-substrate preferences of the different activities in the Pathway can still generate a substrate-dichotomy bottleneck, largely due to inefficient acyl-exchange from phospholipids into the acyl-CoA pool. However, significant levels of EPA and ETA were detected in the triacylglycerols of transgenic seeds, confirming the channelling of these fatty acids into this storage lipid.
-
the Alternative Pathway c20 δ8 desaturase from the non photosynthetic organism acanthamoeba castellanii is an atypical cytochrome b5 fusion desaturase
FEBS Letters, 2006Co-Authors: Olga Sayanova, Richard P Haslam, Colin M Lazarus, Johnathan A NapierAbstract:Abstract A cDNA encoding a C20 Δ8-desaturase was isolated from the free-living soil amoeba, Acanthamoeba castellanii and functionally characterised by heterologous expression. The open reading frame of the A. castellanii C20 Δ8-desaturase showed similarity to other microsomal front-end desaturases, but the N-terminal domain contained a variant form of the conserved heme-binding motif in which H-P-G-G is replaced by H-P-A-G. Co-expression of the A. castellani Δ8-desaturase with the Isochrysis galbana Δ9-elongase in transgenic Arabidopsis plants confirmed the activity observed in yeast and its role in the Alternative Pathway for C20 polyunsaturated fatty acid synthesis. Acyl-CoA profiles of these transgenic plants revealed an unexpected accumulation of C20 fatty acids in the acyl-CoA pool. This is the first report of an Alternative Pathway C20 Δ8-desaturase from a non-photosynthetic organism, and also the first report of a front-end desaturase lacking the canonical cytochrome b5 domain.
-
the Alternative Pathway c20 δ8 desaturase from the non photosynthetic organism acanthamoeba castellanii is an atypical cytochrome b5 fusion desaturase
FEBS Letters, 2006Co-Authors: Olga Sayanova, Richard P Haslam, Colin M Lazarus, Johnathan A NapierAbstract:A cDNA encoding a C20 Delta8-desaturase was isolated from the free-living soil amoeba, Acanthamoeba castellanii and functionally characterised by heterologous expression. The open reading frame of the A. castellanii C20 Delta8-desaturase showed similarity to other microsomal front-end desaturases, but the N-terminal domain contained a variant form of the conserved heme-binding motif in which H-P-G-G is replaced by H-P-A-G. Co-expression of the A. castellani Delta8-desaturase with the Isochrysis galbana Delta9-elongase in transgenic Arabidopsis plants confirmed the activity observed in yeast and its role in the Alternative Pathway for C20 polyunsaturated fatty acid synthesis. Acyl-CoA profiles of these transgenic plants revealed an unexpected accumulation of C20 fatty acids in the acyl-CoA pool. This is the first report of an Alternative Pathway C20 Delta8-desaturase from a non-photosynthetic organism, and also the first report of a front-end desaturase lacking the canonical cytochrome b5 domain.
Olga Sayanova - One of the best experts on this subject based on the ideXlab platform.
-
an Alternative Pathway for the effective production of the omega 3 long chain polyunsaturates epa and eta in transgenic oilseeds
Plant Biotechnology Journal, 2015Co-Authors: Johnathan A Napier, Richard P Haslam, Noemi Ruizlopez, Sarah Usher, Olga SayanovaAbstract:The synthesis and accumulation of omega-3 long-chain polyunsaturated fatty acids in transgenic Camelina sativa is demonstrated using the so-called Alternative Pathway. This aerobic Pathway is found in a small number of taxonomically unrelated unicellular organisms and utilizes a C18 Δ9-elongase to generate C20 PUFAs. Here, we evaluated four different combinations of seed-specific transgene-derived activities to systematically determine the potential of this Pathway to direct the synthesis of eicosapentaenoic acid (EPA) in transgenic plants. The accumulation of EPA and the related omega-3 LC-PUFA eicosatetraenoic acid (ETA) was observed up to 26.4% of total seed fatty acids, of which ETA was 9.5%. Seed oils such as these not only represent an additional source of EPA, but also an entirely new source of the bona fide fish oil ETA. Detailed lipidomic analysis of the Alternative Pathway in Camelina revealed that the acyl-substrate preferences of the different activities in the Pathway can still generate a substrate-dichotomy bottleneck, largely due to inefficient acyl-exchange from phospholipids into the acyl-CoA pool. However, significant levels of EPA and ETA were detected in the triacylglycerols of transgenic seeds, confirming the channelling of these fatty acids into this storage lipid.
-
the Alternative Pathway c20 δ8 desaturase from the non photosynthetic organism acanthamoeba castellanii is an atypical cytochrome b5 fusion desaturase
FEBS Letters, 2006Co-Authors: Olga Sayanova, Richard P Haslam, Colin M Lazarus, Johnathan A NapierAbstract:Abstract A cDNA encoding a C20 Δ8-desaturase was isolated from the free-living soil amoeba, Acanthamoeba castellanii and functionally characterised by heterologous expression. The open reading frame of the A. castellanii C20 Δ8-desaturase showed similarity to other microsomal front-end desaturases, but the N-terminal domain contained a variant form of the conserved heme-binding motif in which H-P-G-G is replaced by H-P-A-G. Co-expression of the A. castellani Δ8-desaturase with the Isochrysis galbana Δ9-elongase in transgenic Arabidopsis plants confirmed the activity observed in yeast and its role in the Alternative Pathway for C20 polyunsaturated fatty acid synthesis. Acyl-CoA profiles of these transgenic plants revealed an unexpected accumulation of C20 fatty acids in the acyl-CoA pool. This is the first report of an Alternative Pathway C20 Δ8-desaturase from a non-photosynthetic organism, and also the first report of a front-end desaturase lacking the canonical cytochrome b5 domain.
-
the Alternative Pathway c20 δ8 desaturase from the non photosynthetic organism acanthamoeba castellanii is an atypical cytochrome b5 fusion desaturase
FEBS Letters, 2006Co-Authors: Olga Sayanova, Richard P Haslam, Colin M Lazarus, Johnathan A NapierAbstract:A cDNA encoding a C20 Delta8-desaturase was isolated from the free-living soil amoeba, Acanthamoeba castellanii and functionally characterised by heterologous expression. The open reading frame of the A. castellanii C20 Delta8-desaturase showed similarity to other microsomal front-end desaturases, but the N-terminal domain contained a variant form of the conserved heme-binding motif in which H-P-G-G is replaced by H-P-A-G. Co-expression of the A. castellani Delta8-desaturase with the Isochrysis galbana Delta9-elongase in transgenic Arabidopsis plants confirmed the activity observed in yeast and its role in the Alternative Pathway for C20 polyunsaturated fatty acid synthesis. Acyl-CoA profiles of these transgenic plants revealed an unexpected accumulation of C20 fatty acids in the acyl-CoA pool. This is the first report of an Alternative Pathway C20 Delta8-desaturase from a non-photosynthetic organism, and also the first report of a front-end desaturase lacking the canonical cytochrome b5 domain.
M. Edward Medof - One of the best experts on this subject based on the ideXlab platform.
-
Decay acceleration of the complement Alternative Pathway C3 convertase.
Immunopharmacology, 1999Co-Authors: Dennis E. Hourcade, L M Mitchell, M. Edward MedofAbstract:An ELISA-based method is described for analyzing the mechanism by which the decay of the Alternative Pathway C3 convertase is accelerated by C3 regulatory proteins. Using this assay, we show that human decay-accelerating factor (DAF) and factor H are active on mature convertase complexes (C3bBb) but not on their nascent precursor (C3bB). This finding has implications on the mechanisms of action of these two regulators. The complement convertases cleave the serum protein C3, and the resulting C3b activation fragments covalently attach to nearby targets where they direct antigen selection, immune clearance, and cell lysis. Several proteins, including the membrane protein DAF, and the serum protein factor H, limit convertase activity by promoting their irreversible dissociation. An understanding of the biochemical mechanisms providing for their activities would be helpful for the therapeutic control of the complement response.
-
localization of classical and Alternative Pathway regulatory activity within the decay accelerating factor
Journal of Immunology, 1996Co-Authors: William G. Brodbeck, Carolyn Mold, M. Edward Medof, Jason L SperryAbstract:Decay-accelerating factor (DAF) is a cell-associated C regulatory protein that protects host cells from autologous C attack. It functions intrinsically in host cell surface membranes to rapidly dissociate autologous classical and Alternative Pathway C3 convertases whenever these amplifying enzymes assemble on host cell surfaces. It is composed of four contiguous approximately 70 amino acid long regions termed short consensus repeats (SCRs) that share homology with similar units in other C3 convertase regulatory proteins. It is attached to the cell surface membrane by a glycoinositol phospholipid (GPI) anchor that is added posttranslationally. In this study, we prepared rGPI-anchored DAF proteins devoid of individual SCRs. We then incorporated the GPI-anchored products into sheep erythrocyte (Esh) hemolytic intermediates and examined their abilities to intrinsically regulate classical or Alternative Pathway activation. We found that classical Pathway C3 convertase regulatory function resides within SCR-2 and SCR-3, while Alternative Pathway C3 convertase regulatory function resides within SCR-2, -3, and -4. Functional comparisons of the variant DAF proteins in fluid phase C3 activation assays established that the differences reflect domain-specific interactions rather than changes in the spatial arrangement of SCRs above the cell surface. In accordance with these findings, we found that variant DAF molecules containing SCR-1, -2, and -3, but not SCR-4, function to selectively inhibit classical Pathway activation.
Richard J.h. Smith - One of the best experts on this subject based on the ideXlab platform.
-
diagnosis of complement Alternative Pathway disorders
Kidney International, 2016Co-Authors: Andrea Angioi, Sanjeev Sethi, Yuzhou Zhang, Fernando Custodio Fervenza, Richard J.h. Smith, David L Murray, Jens Van Praet, Antonello Pani, An S De VrieseAbstract:Kidney diseases resulting from abnormal control of the complement Alternative Pathway include atypical hemolytic uremic syndrome, C3 glomerulonephritis, and dense-deposit disease, as well as atypical postinfectious glomerulonephritis. Although clinically diverse, they all result from loss of surface or fluid-phase complement control, caused by acquired or genetic defects in the complement Alternative Pathway. As such, the diagnostic approach is similar and includes a comprehensive biochemical, genetic, and pathologic analysis of the complement Pathway. The biochemical test battery includes functional activity measurements of the entire complement Pathway, functional and quantitative analysis of individual components and regulators, and quantification of activation products. In patients with a thrombotic microangiopathy, ADAMTS-13 activity should be determined to exclude a thrombotic thrombocytopenic purpura. The spectrum of genes currently known to be involved in the pathogenesis of Alternative Pathway disorders is rapidly expanding. Pathologic analysis of a kidney biopsy specimen is sophisticated with ad hoc immunofluorescence studies and laser microdissection with mass spectrometry. The identification of the underlying defect in the Alternative Pathway based on this comprehensive analysis will allow treatment to be directed to the site of dysregulation.
-
atypical postinfectious glomerulonephritis is associated with abnormalities in the Alternative Pathway of complement
Kidney International, 2013Co-Authors: Sanjeev Sethi, Yuzhou Zhang, Ladan Zand, Nicole C Meyer, Nicolo Borsa, Fernando Custodio Fervenza, Samih H. Nasr, Richard J.h. SmithAbstract:Postinfectious glomerulonephritis is a common disorder that develops following an infection. In the majority of cases, there is complete recovery of renal function within a few days to weeks following resolution of the infection. In a small percentage of patients, however, the glomerulonephritis takes longer to resolve, resulting in persistent hematuria and proteinuria, or even progression to end-stage kidney disease. In some cases of persistent hematuria and proteinuria, kidney biopsies show findings of a postinfectious glomerulonephritis even in the absence of any evidence of a preceding infection. The cause of such ‘atypical’ postinfectious glomerulonephritis, with or without evidence of preceding infection, is unknown. Here we show that most patients diagnosed with this ‘atypical’ postinfectious glomerulonephritis have an underlying defect in the regulation of the Alternative Pathway of complement. These defects include mutations in complement-regulating proteins and antibodies to the C3 convertase known as C3 nephritic factors. As a result, the activated Alternative Pathway is not brought under control even after resolution of the infection. Hence, the sequela is continual glomerular deposition of complement factors with resultant inflammation and development of an ‘atypical’ postinfectious glomerulonephritis.
-
the genetics of the Alternative Pathway of complement in the pathogenesis of hellp syndrome
Journal of Maternal-fetal & Neonatal Medicine, 2012Co-Authors: Francesca Crovetto, Nicolo Borsa, Richard J.h. Smith, Barbara Acaia, Carla Nishimura, Kathy L Frees, Flora Peyvandi, Roberta Palla, Massimo Cugno, Silvana TedeschiAbstract:Objective: Recent preliminary evidence suggests that gene mutations in the Alternative Pathway of complement may play a crucial role in the pathogenesis of HELLP syndrome. To verify this hypothesis, a consecutive series of women who developed the syndrome was screened for variants in Alternative Pathway genes. Methods: The coding sequences and intron-exon boundaries of the complement factor H (CFH), complement factor I (CFI), Membrane Cofactor Protein (MCP), complement factor B (CFB) and C3 were sequenced in 33 women with a diagnosis of HELLP syndrome. Results: Three patients carried heterozygotic variants – two in CFI and one in MCP. One of the two CFI mutations, was previously described as an unremarkable polymorphism. Conversely, computational analyses for the remaining two cases suggest that they may have a functional impact. Conclusions: The present study confirms that the Alternative Pathway of complement may play a role in the pathogenesis of HELLP syndrome. However, its overall contribution to the...
-
proliferative glomerulonephritis secondary to dysfunction of the Alternative Pathway of complement
Clinical Journal of The American Society of Nephrology, 2011Co-Authors: Sanjeev Sethi, Yuzhou Zhang, Samih H. Nasr, Fernando C Fervenza, Nelson Leung, Julie A Vrana, Carl H Cramer, Carla M Nester, Richard J.h. SmithAbstract:Summary Background and objectives dense deposit disease (DDD) is the prototypical membranoproliferative glomerulonephritis (MPGN), in which fluid-phase dysregulation of the Alternative Pathway (AP) of complement results in the accumulation of complement debris in the glomeruli, often producing an MPGN pattern of injury in the absence of immune complexes. A recently described entity referred to as GN with C3 deposition (GN-C3) bears many similarities to DDD. The purpose of this study was to evaluate AP function in cases of GN-C3. Design, setting, participants, & measurements Five recent cases of MPGN with extensive C3 deposition were studied. Renal biopsy in one case exhibited the classic findings of DDD. Three cases showed GN-C3 in the absence of significant Ig deposition; however, the classic hallmark of DDD—dense deposits along the glomerular basement membranes and mesangium—was absent. The remaining case exhibited features of both DDD and GN-C3. Results Evidence of AP activation was demonstrable in all cases and included increased levels of soluble membrane attack complex (all cases), positive AP functional assays (four cases), and a positive hemolytic assay (one case). Autoantibodies were found to C3 convertase (two cases) and to factor H (one case). Factor H mutation screening identified the H402 allele (all cases) and a c.C2867T p.T956M missence mutation (one case). Laser microdissection and mass spectrometry of glomeruli of GN-C3 (two cases) showed a proteomic profile very similar to DDD. Conclusions These studies implicate AP dysregulation in a spectrum of rare renal diseases that includes GN-C3 and DDD. Clin J Am Soc Nephrol 6: 1009–1017, 2011. doi: 10.2215/CJN.07110810
-
mutations in Alternative Pathway complement proteins in american patients with atypical hemolytic uremic syndrome
Human Mutation, 2010Co-Authors: Tara Maga, Kathy L Frees, Carla Nishimura, Amy E Weaver, Richard J.h. SmithAbstract:Atypical hemolytic uremic syndrome (aHUS) is characterized by acute renal failure, thrombocytopenia and microangiopathic hemolytic anemia, and occurs with an estimated incidence in the USA of 2 per 1,000,000. Disease pathogenesis is related to dysregulation of the Alternative Pathway (AP) of the complement cascade at the level of the cell membrane secondary to mutations in a number of complement genes including complement factor H (CFH), complement factor H-related 5 (CFHR5), complement factor I (CFI), CD46 (MCP), complement factor B (CFB), complement component 3 (C3) and thrombomodulin (THBD). Since aHUS is rare, mutation rate data in large patient cohorts are scarce. Here we present the first cohort of American patients in whom mutation screening was completed on all genes currently implicated in aHUS. In addition to identifying a number of novel variants, we provide information on the relative frequency of mutations in these genes in an American aHUS population. Twelve percent (12%) of patients carrying disease-associated genetic variants segregated mutations in more than one gene mandating comprehensive genetic testing in the diagnosis and management of these patients. ©2010 Wiley-Liss, Inc.
Richard P Haslam - One of the best experts on this subject based on the ideXlab platform.
-
an Alternative Pathway for the effective production of the omega 3 long chain polyunsaturates epa and eta in transgenic oilseeds
Plant Biotechnology Journal, 2015Co-Authors: Johnathan A Napier, Richard P Haslam, Noemi Ruizlopez, Sarah Usher, Olga SayanovaAbstract:The synthesis and accumulation of omega-3 long-chain polyunsaturated fatty acids in transgenic Camelina sativa is demonstrated using the so-called Alternative Pathway. This aerobic Pathway is found in a small number of taxonomically unrelated unicellular organisms and utilizes a C18 Δ9-elongase to generate C20 PUFAs. Here, we evaluated four different combinations of seed-specific transgene-derived activities to systematically determine the potential of this Pathway to direct the synthesis of eicosapentaenoic acid (EPA) in transgenic plants. The accumulation of EPA and the related omega-3 LC-PUFA eicosatetraenoic acid (ETA) was observed up to 26.4% of total seed fatty acids, of which ETA was 9.5%. Seed oils such as these not only represent an additional source of EPA, but also an entirely new source of the bona fide fish oil ETA. Detailed lipidomic analysis of the Alternative Pathway in Camelina revealed that the acyl-substrate preferences of the different activities in the Pathway can still generate a substrate-dichotomy bottleneck, largely due to inefficient acyl-exchange from phospholipids into the acyl-CoA pool. However, significant levels of EPA and ETA were detected in the triacylglycerols of transgenic seeds, confirming the channelling of these fatty acids into this storage lipid.
-
the Alternative Pathway c20 δ8 desaturase from the non photosynthetic organism acanthamoeba castellanii is an atypical cytochrome b5 fusion desaturase
FEBS Letters, 2006Co-Authors: Olga Sayanova, Richard P Haslam, Colin M Lazarus, Johnathan A NapierAbstract:Abstract A cDNA encoding a C20 Δ8-desaturase was isolated from the free-living soil amoeba, Acanthamoeba castellanii and functionally characterised by heterologous expression. The open reading frame of the A. castellanii C20 Δ8-desaturase showed similarity to other microsomal front-end desaturases, but the N-terminal domain contained a variant form of the conserved heme-binding motif in which H-P-G-G is replaced by H-P-A-G. Co-expression of the A. castellani Δ8-desaturase with the Isochrysis galbana Δ9-elongase in transgenic Arabidopsis plants confirmed the activity observed in yeast and its role in the Alternative Pathway for C20 polyunsaturated fatty acid synthesis. Acyl-CoA profiles of these transgenic plants revealed an unexpected accumulation of C20 fatty acids in the acyl-CoA pool. This is the first report of an Alternative Pathway C20 Δ8-desaturase from a non-photosynthetic organism, and also the first report of a front-end desaturase lacking the canonical cytochrome b5 domain.
-
the Alternative Pathway c20 δ8 desaturase from the non photosynthetic organism acanthamoeba castellanii is an atypical cytochrome b5 fusion desaturase
FEBS Letters, 2006Co-Authors: Olga Sayanova, Richard P Haslam, Colin M Lazarus, Johnathan A NapierAbstract:A cDNA encoding a C20 Delta8-desaturase was isolated from the free-living soil amoeba, Acanthamoeba castellanii and functionally characterised by heterologous expression. The open reading frame of the A. castellanii C20 Delta8-desaturase showed similarity to other microsomal front-end desaturases, but the N-terminal domain contained a variant form of the conserved heme-binding motif in which H-P-G-G is replaced by H-P-A-G. Co-expression of the A. castellani Delta8-desaturase with the Isochrysis galbana Delta9-elongase in transgenic Arabidopsis plants confirmed the activity observed in yeast and its role in the Alternative Pathway for C20 polyunsaturated fatty acid synthesis. Acyl-CoA profiles of these transgenic plants revealed an unexpected accumulation of C20 fatty acids in the acyl-CoA pool. This is the first report of an Alternative Pathway C20 Delta8-desaturase from a non-photosynthetic organism, and also the first report of a front-end desaturase lacking the canonical cytochrome b5 domain.