scholarly journals A Fatty Acid Synthase Gene in Cochliobolus carbonum Required for Production of HC-Toxin, Cyclo(d-Prolyl-l-Alanyl- d-Alanyl- l-2-Amino-9,10-Epoxi-8-Oxodecanoyl)

1997 ◽  
Vol 10 (2) ◽  
pp. 207-214 ◽  
Author(s):  
Joong-Hoon Ahn ◽  
Jonathan D. Walton
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Synthase ◽  
Cyclic Peptide ◽  
Decanoic Acid ◽  
Toxin Production ◽  
Gene Encoding ◽  
Cochliobolus Carbonum ◽  
Primary Amino ◽  
Hc Toxin

The fungal maize pathogen Cochliobolus carbonum produces a phytotoxic and cytostatic cyclic peptide, HC-toxin, of structure cyclo(D-prolyl-L-alanyl-D-alanyl-L-Aeo), in which Aeo stands for 2-amino-9,10-epoxi-8-oxodecanoic acid. Here we report the isolation of a gene, TOXC, that is present only in HC-toxin-producing (Tox2+) fungal strains. TOXC is present in most Tox2+ strains in three functional copies, all of which are on the same chromosome as the gene encoding HC-toxin synthetase. When all copies of TOXC are mutated by targeted gene disruption, the fungus grows and sporulates normally in vitro but no longer makes HC-toxin and is not pathogenic, indicating that TOXC has a specific role in HC-toxin production and hence virulence. The TOXC mRNA is 6.5 kb and the predicted product has 2,080 amino acids and a molecular weight of 233,000. The primary amino acid sequence is highly similar (45 to 47% identity) to the β subunit of fatty acid synthase from several lower eukaryotes, and contains, in the same order as in other β subunits, domains predicted to encode acetyl transferase, enoyl reductase, dehydratase, and malonyl-palmityl transferase. The most plausible function of TOXC is to contribute to the synthesis of the decanoic acid backbone of Aeo.

scholarly journals Reduced Virulence Caused by Meiotic Instability of the TOX2 Chromosome of the Maize Pathogen Cochliobolus carbonum

2000 ◽  
Vol 13 (1) ◽  
pp. 80-87 ◽  
Author(s):  
John W. Pitkin ◽  
Anastasia Nikolskaya ◽  
Joong-Hoon Ahn ◽  
Jonathan D. Walton
Keyword(s):  
Cyclic Peptide ◽  
Normal Growth ◽  
Pathogenic Fungi ◽  
Housekeeping Genes ◽  
Toxin Production ◽  
In Planta ◽  
Cochliobolus Carbonum ◽  
Hc Toxin ◽  
Reduced Rate ◽  
Functional Copy

The mechanisms by which pathogenic fungi evolve are poorly understood. Production of the host-selective cyclic peptide HC-toxin is controlled by a complex locus, TOX2, in the plant pathogen Cochliobolus carbonum. Crosses between toxin-producing (Tox2+) and toxin-nonproducing (Tox2-) isolates, as well as crosses between isolates in which the TOX2 genes were on chromosomes of different size, yielded progeny that had lost one or more copies of one or more of the TOX2 genes. Of approximately 200 progeny analyzed, eight (4%) had lost at least one TOX2 gene. All of them still had at least one functional copy of all of the known genes required for HC-toxin production (HTS1, TOXA, TOXC, and TOXE). Most deletion strains could be explained by simple chromosome breaks resulting in the loss of major contiguous portions (0.8 to 1.4 Mb) of the 3.5-Mb TOX2 chromosome, whereas others had more complicated patterns. All deletion strains had normal growth and were fertile, indicating that the 1.4 Mb of DNA contained no essential housekeeping genes. Most strains were also still virulent (Tox2+), but two had a novel phenotype of reduced virulence (RV), characterized by smaller lesions that expanded at a reduced rate and an inability to colonize plants systemically. Although the RV strains made no detectable HC-toxin in culture, the RV phenotype was dependent on the presence of a functional copy of HTS1, which encodes the central enzyme in HC-toxin biosynthesis. We propose that the RV strains still make a low level of HC-toxin, at least in planta, and that this is due to the loss of one or more genes that contribute to, but are not absolutely required for, HC-toxin synthesis.

scholarly journals Structural comparison of Acinetobacter baumannii β-ketoacyl-acyl carrier protein reductases in fatty acid and aryl polyene biosynthesis

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Woo Cheol Lee ◽  
Sungjae Choi ◽  
Ahjin Jang ◽  
Kkabi Son ◽  
Yangmee Kim
Keyword(s):  
Fatty Acid ◽  
Acinetobacter Baumannii ◽  
Gene Cluster ◽  
Fatty Acid Synthase ◽  
Acyl Carrier Protein ◽  
Gene Clusters ◽  
Carrier Protein ◽  
Aryl Group ◽  
Visible Absorption

AbstractSome Gram-negative bacteria harbor lipids with aryl polyene (APE) moieties. Biosynthesis gene clusters (BGCs) for APE biosynthesis exhibit striking similarities with fatty acid synthase (FAS) genes. Despite their broad distribution among pathogenic and symbiotic bacteria, the detailed roles of the metabolic products of APE gene clusters are unclear. Here, we determined the crystal structures of the β-ketoacyl-acyl carrier protein (ACP) reductase ApeQ produced by an APE gene cluster from clinically isolated virulent Acinetobacter baumannii in two states (bound and unbound to NADPH). An in vitro visible absorption spectrum assay of the APE polyene moiety revealed that the β-ketoacyl-ACP reductase FabG from the A. baumannii FAS gene cluster cannot be substituted for ApeQ in APE biosynthesis. Comparison with the FabG structure exhibited distinct surface electrostatic potential profiles for ApeQ, suggesting a positively charged arginine patch as the cognate ACP-binding site. Binding modeling for the aryl group predicted that Leu185 (Phe183 in FabG) in ApeQ is responsible for 4-benzoyl moiety recognition. Isothermal titration and arginine patch mutagenesis experiments corroborated these results. These structure–function insights of a unique reductase in the APE BGC in comparison with FAS provide new directions for elucidating host–pathogen interaction mechanisms and novel antibiotics discovery.

scholarly journals Targeting de novo lipogenesis and the Lands cycle induces ferroptosis in KRAS-mutant lung cancer

2021 ◽  
Author(s):  
Caterina Bartolacci ◽  
Cristina Andreani ◽  
Goncalo Dias do Vale ◽  
Stefano Berto ◽  
Margherita Melegari ◽  
...  
Keyword(s):  
Lung Cancer ◽  
Fatty Acid ◽  
Metabolic Networks ◽  
Fatty Acid Synthase ◽  
De Novo ◽  
Genetically Engineered ◽  
De Novo Lipogenesis ◽  
Main Process

Mutant KRAS (KM) is the most common oncogene in lung cancer (LC). KM regulates several metabolic networks, but their role in tumorigenesis is still not sufficiently characterized to be exploited in cancer therapy. To identify metabolic networks specifically deregulated in KMLC, we characterized the lipidome of genetically engineered LC mice, cell lines, patient derived xenografts and primary human samples. We also determined that KMLC, but not EGFR-mutant (EGFR-MUT) LC, is enriched in triacylglycerides (TAG) and phosphatidylcholines (PC). We also found that KM upregulates fatty acid synthase (FASN), a rate-limiting enzyme in fatty acid (FA) synthesis promoting the synthesis of palmitate and PC. We determined that FASN is specifically required for the viability of KMLC, but not of LC harboring EGFR-MUT or wild type KRAS. Functional experiments revealed that FASN inhibition leads to ferroptosis, a reactive oxygen species (ROS)-and iron-dependent cell death. Consistently, lipidomic analysis demonstrated that FASN inhibition in KMLC leads to accumulation of PC with polyunsaturated FA (PUFA) chains, which are the substrate of ferroptosis. Integrating lipidomic, transcriptome and functional analyses, we demonstrated that FASN provides saturated (SFA) and monounsaturated FA (MUFA) that feed the Lands cycle, the main process remodeling oxidized phospholipids (PL), such as PC. Accordingly, either inhibition of FASN or suppression of the Lands cycle enzymes PLA2 and LPCAT3, promotes the intracellular accumulation of lipid peroxides and ferroptosis in KMLC both in vitro and in vivo. Our work supports a model whereby the high oxidative stress caused by KM dictates a dependency on newly synthesized FA to repair oxidated phospholipids, establishing a targetable vulnerability. These results connect KM oncogenic signaling, FASN induction and ferroptosis, indicating that FASN inhibitors already in clinical trial in KMLC patients (NCT03808558) may be rapidly deployed as therapy for KMLC.

scholarly journals A kinetic rationale for functional redundancy in fatty acid biosynthesis

2020 ◽  
Vol 117 (38) ◽  
pp. 23557-23564
Author(s):  
Alex Ruppe ◽  
Kathryn Mains ◽  
Jerome M. Fox
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Fatty Acid Synthase ◽  
Unsaturated Fatty Acids ◽  
Fatty Acid Biosynthesis ◽  
Average Length ◽  
Functional Redundancy ◽  
Experimental Investigations ◽  
Total Production

Cells build fatty acids with biocatalytic assembly lines in which a subset of enzymes often exhibit overlapping activities (e.g., two enzymes catalyze one or more identical reactions). Although the discrete enzymes that make up fatty acid pathways are well characterized, the importance of catalytic overlap between them is poorly understood. We developed a detailed kinetic model of the fatty acid synthase (FAS) ofEscherichia coliand paired that model with a fully reconstituted in vitro system to examine the capabilities afforded by functional redundancy in fatty acid synthesis. The model captures—and helps explain—the effects of experimental perturbations to FAS systems and provides a powerful tool for guiding experimental investigations of fatty acid assembly. Compositional analyses carried out in silico and in vitro indicate that FASs with multiple partially redundant enzymes enable tighter (i.e., more independent and/or broader range) control of distinct biochemical objectives—the total production, unsaturated fraction, and average length of fatty acids—than FASs with only a single multifunctional version of each enzyme (i.e., one enzyme with the catalytic capabilities of two partially redundant enzymes). Maximal production of unsaturated fatty acids, for example, requires a second dehydratase that is not essential for their synthesis. This work provides a kinetic, control-theoretic rationale for the inclusion of partially redundant enzymes in fatty acid pathways and supplies a valuable framework for carrying out detailed studies of FAS kinetics.

scholarly journals Fisetin Protects Against Hepatic Steatosis Through Regulation of the Sirt1/AMPK and Fatty Acid β-Oxidation Signaling Pathway in High-Fat Diet-Induced Obese Mice

2018 ◽  
Vol 49 (5) ◽  
pp. 1870-1884 ◽  
Author(s):  
Chian-Jiun Liou ◽  
Ciao-Han Wei ◽  
Ya-Ling Chen ◽  
Ching-Yi Cheng ◽  
Chia-Ling Wang ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Lipid Metabolism ◽  
Hepatic Steatosis ◽  
Lipid Accumulation ◽  
High Fat Diet ◽  
Fatty Acid Synthase ◽  
Epididymal Adipose Tissue ◽  
Obese Mice ◽  
High Fat

Background/Aims: Fisetin is a naturally abundant flavonoid isolated from various fruits and vegetables that was recently identified to have potential biological functions in improving allergic airway inflammation, as well as anti-oxidative and anti-tumor properties. Fisetin has also been demonstrated to have anti-obesity properties in mice. However, the effect of fisetin on nonalcoholic fatty liver disease (NAFLD) is still elusive. Thus, the present study evaluated whether fisetin improves hepatic steatosis in high-fat diet (HFD)-induced obese mice and regulates lipid metabolism of FL83B hepatocytes in vitro. Methods: NAFLD was induced by HFD in male C57BL/6 mice. The mice were then injected intraperitoneally with fisetin for 10 weeks. In another experiment, FL83B cells were challenged with oleic acid to induce lipid accumulation and treated with various concentrations of fisetin. Results: NAFLD mice treated with fisetin had decreased body weight and epididymal adipose tissue weight compared to NAFLD mice. Fisetin treatment also reduced liver lipid droplet and hepatocyte steatosis, alleviated serum free fatty acid, and leptin concentrations, significantly decreased fatty acid synthase, and significantly increased phosphorylation of AMPKα and the production of sirt-1 and carnitine palmitoyltransferase I in the liver tissue. In vitro, fisetin decreased lipid accumulation and increased lipolysis and β-oxidation in hepatocytes. Conclusion: This study suggests that fisetin is a potential novel treatment for alleviating hepatic lipid metabolism and improving NAFLD in mice via activation of the sirt1/AMPK and β-oxidation pathway.

scholarly journals Victorin, the host-selective cyclic peptide toxin from the oat pathogen Cochliobolus victoriae, is ribosomally encoded

2020 ◽  
Vol 117 (39) ◽  
pp. 24243-24250
Author(s):  
Simon C. Kessler ◽  
Xianghui Zhang ◽  
Megan C. McDonald ◽  
Cameron L. M. Gilchrist ◽  
Zeran Lin ◽  
...  
Keyword(s):  
Cyclic Peptide ◽  
Amine Oxidase ◽  
Gene Clusters ◽  
Oxidative Cyclization ◽  
Gene Encoding ◽  
Peptide Backbone ◽  
Cochliobolus Victoriae ◽  
Cyclic Hexapeptides ◽  
Core Peptide

The necrotrophic fungal pathogen Cochliobolus victoriae produces victorin, a host-selective toxin (HST) essential for pathogenicity to certain oat cultivars with resistance against crown rust. Victorin is a mixture of highly modified heterodetic cyclic hexapeptides, previously assumed to be synthesized by a nonribosomal peptide synthetase. Herein, we demonstrate that victorin is a member of the ribosomally synthesized and posttranslationally modified peptide (RiPP) family of natural products. Analysis of a newly generated long-read assembly of the C. victoriae genome revealed three copies of precursor peptide genes (vicA1–3) with variable numbers of “GLKLAF” core peptide repeats corresponding to the victorin peptide backbone. vicA1–3 are located in repeat-rich gene-sparse regions of the genome and are loosely clustered with putative victorin biosynthetic genes, which are supported by the discovery of compact gene clusters harboring corresponding homologs in two distantly related plant-associated Sordariomycete fungi. Deletion of at least one copy of vicA resulted in strongly diminished victorin production. Deletion of a gene encoding a DUF3328 protein (VicYb) abolished the production altogether, supporting its predicted role in oxidative cyclization of the core peptide. In addition, we uncovered a copper amine oxidase (CAO) encoded by vicK, in which its deletion led to the accumulation of new glycine-containing victorin derivatives. The role of VicK in oxidative deamination of the N-terminal glycyl moiety of the hexapeptides to the active glyoxylate forms was confirmed in vitro. This study finally unraveled the genetic and molecular bases for biosynthesis of one of the first discovered HSTs and expanded our understanding of underexplored fungal RiPPs.

scholarly journals FABP5 coordinates lipid signaling that promotes prostate cancer metastasis

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Gregory Carbonetti ◽  
Tessa Wilpshaar ◽  
Jessie Kroonen ◽  
Keith Studholme ◽  
Cynthia Converso ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Fatty Acid ◽  
Lipid Metabolism ◽  
Nuclear Receptor ◽  
Fatty Acid Synthase ◽  
Cancer Metastasis ◽  
Receptor Activation ◽  
Lipid Signaling ◽  
Fatty Acid Binding

AbstractProstate cancer (PCa) is defined by dysregulated lipid signaling and is characterized by upregulation of lipid metabolism-related genes including fatty acid binding protein 5 (FABP5), fatty acid synthase (FASN), and monoacylglycerol lipase (MAGL). FASN and MAGL are enzymes that generate cellular fatty acid pools while FABP5 is an intracellular chaperone that delivers fatty acids to nuclear receptors to enhance PCa metastasis. Since FABP5, FASN, and MAGL have been independently implicated in PCa progression, we hypothesized that FABP5 represents a central mechanism linking cytosolic lipid metabolism to pro-metastatic nuclear receptor signaling. Here, we show that the abilities of FASN and MAGL to promote nuclear receptor activation and PCa metastasis are critically dependent upon co-expression of FABP5 in vitro and in vivo. Our findings position FABP5 as a key driver of lipid-mediated metastasis and suggest that disruption of lipid signaling via FABP5 inhibition may constitute a new avenue to treat metastatic PCa.

scholarly journals Fatty Acid Synthesis Is Essential for Survival of Cryptococcus neoformans and a Potential Fungicidal Target

2007 ◽  
Vol 51 (10) ◽  
pp. 3537-3545 ◽  
Author(s):  
Methee Chayakulkeeree ◽  
Thomas H. Rude ◽  
Dena L. Toffaletti ◽  
John R. Perfect
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Cryptococcus Neoformans ◽  
Fatty Acid Synthase ◽  
Acid Synthesis ◽  
Yeast Cells ◽  
Synthase Inhibitor ◽  
The Brain

ABSTRACT Fatty acid synthase in the yeast Cryptococcus neoformans is composed of two subunits encoded by FAS1 and FAS2 genes. We inserted a copper-regulated promoter (P CTR4-2 ) to regulate FAS1 and FAS2 expression in Cryptococcus neoformans (strains P CTR4-2 /FAS1 and P CTR4-2 /FAS2, respectively). Both mutants showed growth rates similar to those of the wild type in a low-copper medium in which FAS1 and FAS2 were expressed, but even in the presence of exogenous fatty acids, strains were suppressed in growth under high-copper conditions. The treatment of C. neoformans with fluconazole was shown to have an increased inhibitory activity and even became fungicidal when either FAS1 or FAS2 expression was suppressed. Furthermore, a subinhibitory dose of fluconazole showed anticryptococcal activity in vitro in the presence of cerulenin, a fatty acid synthase inhibitor. In a murine model of pulmonary cryptococcosis, a tissue census of yeast cells in P CTR4-2 /FAS2 strain at day 7 of infection was significantly lower than that in mice treated with tetrathiomolybdate, a copper chelator (P < 0.05), and a yeast census of P CTR4-2 /FAS1 strain at day 14 of infection in the brain was lower in the presence of more copper. In fact, no positive cultures from the brain were detected in mice (with or without tetrathiomolybdate treatment) infected with the P CTR4-2 /FAS2 strain, which implies that this mutant did not reach the brain in mice. We conclude that both FAS1 and FAS2 in C. neoformans are essential for in vitro and in vivo growth in conditions with and without exogenous fatty acids and that FAS1 and FAS2 can potentially be fungicidal targets for C. neoformans with a potential for synergistic behavior with azoles.

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