A Type II Pathway for Fatty Acid Biosynthesis Presents Drug Targets in Plasmodium falciparum

ABSTRACT It has long been held that the malaria parasite, Plasmodium sp., is incapable of de novo fatty acid synthesis. This view has recently been overturned with the emergence of data for the presence of a fatty acid biosynthetic pathway in the relict plastid of P. falciparum (known as the apicoplast). This pathway represents the type II pathway common to plant chloroplasts and bacteria but distinct from the type I pathway of animals including humans. Specific inhibitors of the type II pathway, thiolactomycin and triclosan, have been reported to target this Plasmodium pathway. Here we report further inhibitors of the plastid-based pathway that inhibit Plasmodium parasites. These include several analogues of thiolactomycin, two with sixfold-greater efficacy than thiolactomycin. We also report that parasites respond very rapidly to such inhibitors and that the greatest sensitivity is seen in ring-stage parasites. This study substantiates the importance of fatty acid synthesis for blood-stage parasite survival and shows that this pathway provides scope for the development of novel antimalarial drugs.

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De novo fatty acid synthesis by freshly isolated alveolar type II epithelial cells

Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism ◽

10.1016/0005-2760(83)90307-7 ◽

1983 ◽

Vol 751 (3) ◽

pp. 462-469 ◽

Cited By ~ 37

Author(s):

William M. Maniscalco ◽

Jacob N. Finkelstein ◽

Anita B. Parkhurst

Keyword(s):

Fatty Acid ◽

Epithelial Cells ◽

Fatty Acid Synthesis ◽

De Novo ◽

Acid Synthesis ◽

Alveolar Type ◽

Type Ii

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Mitochondrial Fatty Acid Synthesis in Trypanosoma brucei

Journal of Biological Chemistry ◽

10.1074/jbc.m609037200 ◽

2006 ◽

Vol 282 (7) ◽

pp. 4427-4436 ◽

Cited By ~ 72

Author(s):

Jennifer L. Stephens ◽

Soo Hee Lee ◽

Kimberly S. Paul ◽

Paul T. Englund

Keyword(s):

Fatty Acids ◽

Fatty Acid ◽

Trypanosoma Brucei ◽

Lipoic Acid ◽

Fatty Acid Synthesis ◽

Acid Synthesis ◽

Type I ◽

Type Ii ◽

Acetyl Coa ◽

Acid Product

Whereas other organisms utilize type I or type II synthases to make fatty acids, trypanosomatid parasites such as Trypanosoma brucei are unique in their use of a microsomal elongase pathway (ELO) for de novo fatty acid synthesis (FAS). Because of the unusual lipid metabolism of the trypanosome, it was important to study a second FAS pathway predicted by the genome to be a type II synthase. We localized this pathway to the mitochondrion, and RNA interference (RNAi) or genomic deletion of acyl carrier protein (ACP) and β-ketoacyl-ACP synthase indicated that this pathway is likely essential for bloodstream and procyclic life cycle stages of the parasite. In vitro assays show that the largest major fatty acid product of the pathway is C16, whereas the ELO pathway, utilizing ELOs 1, 2, and 3, synthesizes up to C18. To demonstrate mitochondrial FAS in vivo, we radio-labeled fatty acids in cultured procyclic parasites with [14C]pyruvate or [14C]threonine, either of which is catabolized to [14C]acetyl-CoA in the mitochondrion. Although some of the [14C]acetyl-CoA may be utilized by the ELO pathway, a striking reduction in radiolabeled fatty acids following ACP RNAi confirmed that it is also consumed by mitochondrial FAS. ACP depletion by RNAi or gene knockout also reduces lipoic acid levels and drastically decreases protein lipoylation. Thus, octanoate (C8), the precursor for lipoic acid synthesis, must also be a product of mitochondrial FAS. Trypanosomes employ two FAS systems: the unconventional ELO pathway that synthesizes bulk fatty acids and a mitochondrial pathway that synthesizes specialized fatty acids that are likely utilized intramitochondrially.

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Mechanistic diversity and regulation of Type II fatty acid synthesis

Biochemical Society Transactions ◽

10.1042/bst0301050 ◽

2002 ◽

Vol 30 (6) ◽

pp. 1050-1055 ◽

Cited By ~ 76

Author(s):

H. Marrakchi ◽

Y.-M. Zhang ◽

C. O. Rock

Keyword(s):

Fatty Acid ◽

Fatty Acid Synthesis ◽

Unsaturated Fatty Acid ◽

Fatty Acid Synthase ◽

Fatty Acid Biosynthesis ◽

Specific Interaction ◽

Acid Synthesis ◽

Protein Crystal ◽

Type Ii ◽

Acid Biosynthesis

Fatty acid biosynthesis is catalysed in most bacteria by a group of highly conserved proteins known as the Type II fatty acid synthase (FAS) system. The Type II system organization is distinct from its mammalian counterpart and offers several unique sites for selective inhibition by antibacterial agents. There has been remarkable progress in the understanding of the genetics, biochemistry and regulation of Type II FASs. One important advance is the discovery of the interaction between the fatty acid degradation regulator, FadR, and the fatty acid biosynthesis regulator, FabR, in the transcriptional control of unsaturated fatty acid synthesis in Escherichia coli. The availability of genomic sequences and high-resolution protein crystal structures has expanded our understanding of Type II FASs beyond the E. coli model system to a number of pathogens. The molecular diversity among the pathway enzymes is illustrated by the discovery of a new type of enoyl-reductase in Streptococcus pneumoniae [enoyl-acyl carrier protein (ACP) reductase II, FabK], the presence of two enoyl-reductases in Bacillus subtilis (enoyl-ACP reductases I and III, FabI and FabL), and the use of a new mechanism for unsaturated fatty acid formation in S. pneumoniae (trans-2-cis-3-enoyl-ACP isomerase, FabM). The solution structure of ACP from Mycobacterium tuberculosis revealed features common to all ACPs, but its extended C-terminal domain may reflect a specific interaction with very-long-chain intermediates.

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Effects of Exogenous Fatty Acids and Inhibition of De Novo Fatty Acid Synthesis on Disaturated Phosphatidylcholine Production by Fetal Lung Cells and Adult Type II Cells

Experimental Lung Research ◽

10.3109/01902148909087872 ◽

1989 ◽

Vol 15 (3) ◽

pp. 473-489 ◽

Cited By ~ 11

Author(s):

William M. Maniscalco ◽

Jacob N. Finkelstein ◽

Anita B. Parkhurst

Keyword(s):

Fatty Acids ◽

Fatty Acid ◽

Fatty Acid Synthesis ◽

De Novo ◽

Fetal Lung ◽

Acid Synthesis ◽

Lung Cells ◽

Type Ii Cells ◽

Type Ii ◽

Adult Type

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Divergent Acyl Carrier Protein Mediates Mitochondrial Fe-S Cluster Biosynthesis in Malaria Parasites

10.1101/2021.04.13.439690 ◽

2021 ◽

Author(s):

Seyi Falekun ◽

Jaime Sepulveda ◽

Yasaman Jami-Alahmadi ◽

Hahnbeom Park ◽

James Wohlschlegel ◽

...

Keyword(s):

Fatty Acid ◽

Fatty Acid Synthesis ◽

Drug Targets ◽

Fatty Acid Biosynthesis ◽

Acyl Carrier Protein ◽

Acid Synthesis ◽

Complex Iii ◽

Carrier Protein ◽

Malaria Parasites ◽

Cluster Biosynthesis

Plasmodium falciparum malaria parasites are early-diverging eukaryotes with many unusual metabolic adaptations. Understanding these adaptations will give insight into parasite evolution and unveil new parasite-specific drug targets. In contrast to human cells, the Plasmodium mitochondrion lacks type II fatty acid biosynthesis (FASII) enzymes yet curiously retains a divergent acyl carrier protein (mACP) incapable of modification by a 4-phosphopantetheine (Ppant) group required for canonical ACP function as the scaffold for fatty acid synthesis. We report that ligand-dependent knockdown of mACP expression is lethal to parasites, indicating an essential FASII-independent function. Decyl-ubiquinone rescues parasites temporarily from this lethal phenotype, suggesting a dominant dysfunction of the mitochondrial electron transport chain (ETC) followed by broader defects beyond the ETC. Biochemical studies reveal that Plasmodium mACP binds and stabilizes the Isd11-Nfs1 cysteine desulfurase complex required for Fe-S cluster biosynthesis, and mACP knockdown causes loss of both Nfs1 and the Rieske Fe-S cluster protein in ETC Complex III. This work identifies Ppant-independent mACP as an essential mitochondrial adaptation in Plasmodium malaria parasites that appears to be a shared metabolic feature of Apicomplexan pathogens, including Toxoplasma and Babesia. This parasite-specific adaptation highlights the ancient, fundamental role of ACP in mitochondrial Fe-S cluster biogenesis and reveals an evolutionary driving force to retain this interaction with ACP independent of its eponymous function in fatty acid synthesis.

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Synthesis of fatty acids in the perfused mouse liver

Biochemical Journal ◽

10.1042/bj1420611 ◽

1974 ◽

Vol 142 (3) ◽

pp. 611-618 ◽

Cited By ~ 57

Author(s):

D. Michael W. Salmon ◽

Neil L. Bowen ◽

Douglas A. Hems

Keyword(s):

Fatty Acids ◽

Fatty Acid ◽

Fatty Acid Synthesis ◽

De Novo ◽

Saturated Fatty Acids ◽

Carbon Sources ◽

Acid Synthesis ◽

Hepatic Glycogen ◽

Total Rate ◽

Glucose Carbon

1. Fatty acid synthesis de novo was measured in the perfused liver of fed mice. 2. The total rate, measured by the incorporation into fatty acid of3H from3H2O (1–7μmol of fatty acid/h per g of fresh liver), resembled the rate found in the liver of intact mice. 3. Perfusions with l-[U-14C]lactic acid and [U-14C]glucose showed that circulating glucose at concentrations less than about 17mm was not a major carbon source for newly synthesized fatty acid, whereas lactate (10mm) markedly stimulated fatty acid synthesis, and contributed extensive carbon to lipogenesis. 4. The identification of 50% of the carbon converted into newly synthesized fatty acid lends further credibility to the use of3H2O to measure hepatic fatty acid synthesis. 5. The total rate of fatty acid synthesis, and the contribution of glucose carbon to lipogenesis, were directly proportional to the initial hepatic glycogen concentration. 6. The proportion of total newly synthesized lipid that was released into the perfusion medium was 12–16%. 7. The major products of lipogenesis were saturated fatty acids in triglyceride and phospholipid. 8. The rate of cholesterol synthesis, also measured with3H2O, expressed as acetyl residues consumed, was about one-fourth of the basal rate of fatty acid synthesis. 9. These results are discussed in terms of the carbon sources of hepatic newly synthesized fatty acids, and the effect of glucose, glycogen and lactate in stimulating lipogenesis, independently of their role as precursors.

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