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Enzymatic chokepoints and synergistic drug targets in the sterol biosynthesis pathway of Naegleria fowleri.
PLoS Pathog. 2018 09; 14(9):e1007245.PP

Abstract

Naegleria fowleri is a free-living amoeba that can also act as an opportunistic pathogen causing severe brain infection, primary amebic meningoencephalitis (PAM), in humans. The high mortality rate of PAM (exceeding 97%) is attributed to (i) delayed diagnosis, (ii) lack of safe and effective anti-N. fowleri drugs, and (iii) difficulty of delivering drugs to the brain. Our work addresses identification of new molecular targets that may link anti-Naegleria drug discovery to the existing pharmacopeia of brain-penetrant drugs. Using inhibitors with known mechanism of action as molecular probes, we mapped the sterol biosynthesis pathway of N. fowleri by GC-MS analysis of metabolites. Based on this analysis, we chemically validated two enzymes downstream to CYP51, sterol C24-methyltransferase (SMT, ERG6) and sterol Δ8-Δ7 -isomerase (ERG2), as potential therapeutic drug targets in N. fowleri. The sterol biosynthetic cascade in N. fowleri displayed a mixture of canonical features peculiar to different domains of life: lower eukaryotes, plants and vertebrates. In addition to the cycloartenol→ergosterol biosynthetic route, a route leading to de novo cholesterol biosynthesis emerged. Isotopic labeling of the de novo-synthesized sterols by feeding N. gruberi trophozoites on the U13C-glucose-containing growth medium identified an exogenous origin of cholesterol, while 7-dehydrocholesterol (7DHC) had enriched 13C-content, suggesting a dual origin of this metabolite both from de novo biosynthesis and metabolism of scavenged cholesterol. Sterol homeostasis in Naegleria may be orchestrated over the course of its life-cycle by a "switch" between ergosterol and cholesterol biosynthesis. By demonstrating the growth inhibition and synergistic effects of the sterol biosynthesis inhibitors, we validated new, potentially druggable, molecular targets in N. fowleri. The similarity of the Naegleria sterol Δ8-Δ7 -isomerase to the human non-opioid σ1 receptor, implicated in human CNS conditions such as addiction, amnesia, pain and depression, provides an incentive to assess structurally diverse small-molecule brain-penetrant drugs targeting the human receptor for anti-Naegleria activity.

Authors+Show Affiliations

Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas, United States of America.Center for Discovery and Innovation in Parasitic Diseases, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California, United States of America.Center for Discovery and Innovation in Parasitic Diseases, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California, United States of America.Center for Discovery and Innovation in Parasitic Diseases, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California, United States of America.Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas, United States of America.Department of Microbiology and Immunology, Meharry Medical College, Nashville, Tennessee, United States of America.Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas, United States of America.Center for Discovery and Innovation in Parasitic Diseases, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California, United States of America.

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

30212566

Citation

Zhou, Wenxu, et al. "Enzymatic Chokepoints and Synergistic Drug Targets in the Sterol Biosynthesis Pathway of Naegleria Fowleri." PLoS Pathogens, vol. 14, no. 9, 2018, pp. e1007245.
Zhou W, Debnath A, Jennings G, et al. Enzymatic chokepoints and synergistic drug targets in the sterol biosynthesis pathway of Naegleria fowleri. PLoS Pathog. 2018;14(9):e1007245.
Zhou, W., Debnath, A., Jennings, G., Hahn, H. J., Vanderloop, B. H., Chaudhuri, M., Nes, W. D., & Podust, L. M. (2018). Enzymatic chokepoints and synergistic drug targets in the sterol biosynthesis pathway of Naegleria fowleri. PLoS Pathogens, 14(9), e1007245. https://doi.org/10.1371/journal.ppat.1007245
Zhou W, et al. Enzymatic Chokepoints and Synergistic Drug Targets in the Sterol Biosynthesis Pathway of Naegleria Fowleri. PLoS Pathog. 2018;14(9):e1007245. PubMed PMID: 30212566.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Enzymatic chokepoints and synergistic drug targets in the sterol biosynthesis pathway of Naegleria fowleri. AU - Zhou,Wenxu, AU - Debnath,Anjan, AU - Jennings,Gareth, AU - Hahn,Hye Jee, AU - Vanderloop,Boden H, AU - Chaudhuri,Minu, AU - Nes,W David, AU - Podust,Larissa M, Y1 - 2018/09/13/ PY - 2018/03/13/received PY - 2018/07/27/accepted PY - 2018/9/14/entrez PY - 2018/9/14/pubmed PY - 2019/1/23/medline SP - e1007245 EP - e1007245 JF - PLoS pathogens JO - PLoS Pathog. VL - 14 IS - 9 N2 - Naegleria fowleri is a free-living amoeba that can also act as an opportunistic pathogen causing severe brain infection, primary amebic meningoencephalitis (PAM), in humans. The high mortality rate of PAM (exceeding 97%) is attributed to (i) delayed diagnosis, (ii) lack of safe and effective anti-N. fowleri drugs, and (iii) difficulty of delivering drugs to the brain. Our work addresses identification of new molecular targets that may link anti-Naegleria drug discovery to the existing pharmacopeia of brain-penetrant drugs. Using inhibitors with known mechanism of action as molecular probes, we mapped the sterol biosynthesis pathway of N. fowleri by GC-MS analysis of metabolites. Based on this analysis, we chemically validated two enzymes downstream to CYP51, sterol C24-methyltransferase (SMT, ERG6) and sterol Δ8-Δ7 -isomerase (ERG2), as potential therapeutic drug targets in N. fowleri. The sterol biosynthetic cascade in N. fowleri displayed a mixture of canonical features peculiar to different domains of life: lower eukaryotes, plants and vertebrates. In addition to the cycloartenol→ergosterol biosynthetic route, a route leading to de novo cholesterol biosynthesis emerged. Isotopic labeling of the de novo-synthesized sterols by feeding N. gruberi trophozoites on the U13C-glucose-containing growth medium identified an exogenous origin of cholesterol, while 7-dehydrocholesterol (7DHC) had enriched 13C-content, suggesting a dual origin of this metabolite both from de novo biosynthesis and metabolism of scavenged cholesterol. Sterol homeostasis in Naegleria may be orchestrated over the course of its life-cycle by a "switch" between ergosterol and cholesterol biosynthesis. By demonstrating the growth inhibition and synergistic effects of the sterol biosynthesis inhibitors, we validated new, potentially druggable, molecular targets in N. fowleri. The similarity of the Naegleria sterol Δ8-Δ7 -isomerase to the human non-opioid σ1 receptor, implicated in human CNS conditions such as addiction, amnesia, pain and depression, provides an incentive to assess structurally diverse small-molecule brain-penetrant drugs targeting the human receptor for anti-Naegleria activity. SN - 1553-7374 UR - https://www.unboundmedicine.com/medline/citation/30212566/Enzymatic_chokepoints_and_synergistic_drug_targets_in_the_sterol_biosynthesis_pathway_of_Naegleria_fowleri_ L2 - http://dx.plos.org/10.1371/journal.ppat.1007245 DB - PRIME DP - Unbound Medicine ER -