Lipids are the preferred substrate of the protist<i>Naegleria gruberi</i>, relative of a human brain pathogen

Bexkens, Michiel L.; Zimorski, Verena; Sarink, Maarten J.; Wienk, Hans; Brouwers, Jos F.; Jonckheere, Johan F. De; Martin, William; Opperdoes, Fred R.; Hellemond, Jaap J. van; Tielens, Aloysius G. M.

doi:10.1101/370890

Cited by 5 publications

(12 citation statements)

References 27 publications

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“…Moreover, the carnitine/acylcarnitine carrier was identified in the membrane-enriched proteomic analysis, and its expression was slightly increased in iron-starved cells. This mitochondrial membrane-bound protein is involved in lipid metabolism, which was recently shown to be vital for N. gruberi [33]. Another mitochondrial transport protein, the phosphate carrier, was strongly upregulated in iron-deficient conditions, probably as an effort to compensate for impaired respiration and decreased ATP production in the mitochondria of iron-deficient cells.…”

Section: Discussionmentioning

confidence: 99%

Adaptive iron utilization compensates for the lack of an inducible uptake system inNaegleria fowleriand represents a potential target for therapeutic intervention

Arbon

Ženíšková

Mach

et al. 2019

Preprint

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Warm fresh water is a natural habitat for many single-celled organisms, including protozoan parasites such as the infamous brain-eating amoeba, Naegleria fowleri, which can become pathogenic for mammals, including humans. The condition caused by N. fowleri is known as primary amoebic meningoencephalitis, which is a generic and usually fatal infection of the brain with rapid onset. One of the important factors influencing a wide spectrum of pathogens, including N. fowleri, is the bioavailability of iron in the environment. The strategy of withholding iron evolved in mammalian hosts, and the different strategies of pathogens to obtain it are an important part of host-parasite interactions.In the present study, we employ different biochemical and analytical methods to explore the effect of decreased iron availability on the cellular processes of N. fowleri. We show that under iron starvation, nonessential, iron-dependent, mostly cytosolic pathways in N. fowleri are downregulated, while the metal is utilized in the mitochondria to maintain vital respiratory processes. Surprisingly, N. fowleri fails to respond to acute shortages of iron by the induction of a reductive iron uptake system that seems to be the main iron-obtaining strategy of the parasite. Our work aims to demonstrate the importance of mitochondrial iron in the biology of N. fowleri and to explore the plausibility of exploiting it as a potential target for therapeutic interference.Author SummaryNaegleria fowleri is undoubtedly one of the deadliest parasites of humans, hence the name “brain-eating amoeba”. Being dangerous, but rare, it may be regarded as a highly understudied pathogen of humans. Unfortunately, the symptoms of primary amoebic meningoencephalitis may be confused with much more common bacterial meningoencephalitis; therefore, it is quite probable that many infections caused by N. fowleri have been misdiagnosed as bacterial infections without further inquiry. In many cases, fast diagnosis is vital for commencing the correct therapy, and even then, complete success of the treatment is very rare. Our laboratory focuses on the uptake and intracellular metabolism of metals in unicellular eukaryotes, so we decided to explore the biology of N. fowleri from this aspect. Changes in the proteome, as a direct effect of iron-deficient conditions, were described, and these data were used to further explore the ways in which N. fowleri responds to these conditions on a cellular level and how its biology changes. Based on these findings, we propose that the struggle of N. fowleri to obtain iron from its host could be exploited for therapeutic interference purposes in primary amoebic meningoencephalitis patients.

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Section: Discussionmentioning

confidence: 99%

Adaptive iron utilization compensates for the lack of an inducible uptake system inNaegleria fowleriand represents a potential target for therapeutic intervention

Arbon

Ženíšková

Mach

et al. 2019

Preprint

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“…N. gruberi is a non-pathogenic relative of N. fowleri and genomic analysis has shown that its metabolic machinery is highly similar to that of N. fowleri (14-16). Therefore, the observations in our N. gruberi model indicate that inhibition of fatty acid oxidation as a new treatment strategy for PAM seems promising.…”

Section: Discussionmentioning

confidence: 99%

“…N. gruberi strain NEG-M (ATCC® 30224) was grown axenically at 25 °C in modified PYNFH medium (ATCC medium 1034), as described before (14). Modified PYNFH is composed of peptone, yeast extract, yeast nucleic acid, folic acid, 10% heat-inactivated fetal bovine serum, 100 units/ml penicillin, 100 µg/ml streptomycin and 40 µg/ml gentamicin.…”

Section: Methodsmentioning

confidence: 99%

“…Previous research by our group showed that N. gruberi , a close relative to N. fowleri , prefers fatty acids as a food source (14). This led us to the hypothesis that inhibiting fatty acid oxidation (FAO) could inhibit growth or even kill the amoeba.…”

Section: Introductionmentioning

confidence: 96%

“…We identified several drugs that inhibit fatty acid metabolism in different parts of this pathway. As the metabolic machinery of N. gruberi is highly similar to that of N. fowleri (14-16), we used N. gruberi as a model organism to determine the effects of these compounds. We then compared the effects of these inhibitors to the currently used treatment (AMB and MIL) and determined additive effects of the compounds when they were combined.…”

Section: Introductionmentioning

confidence: 99%

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Inhibition of fatty acid oxidation as a new target to treat Primary Amoebic Meningoencephalitis by repurposing two well-known drugs

Sarink

Verbon

Tielens

et al. 2019

Preprint

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14Primary Amoebic Meningoencephalitis (PAM) is a rapidly fatal infection caused by the free-15 living amoeba Naegleria fowleri. The disease mostly affects healthy children and young 16 adults after contaminated water enters the nose, generally during recreational water activities. 17 The amoeba migrate along the olfactory nerve to the brain, resulting in seizures, coma and 18 eventually death. Previous research has shown that Naegleria gruberi, a close relative of N. 19 fowleri, prefers lipids over glucose as an energy source. Therefore, we tested several 20 inhibitors of fatty acid oxidation alongside the currently used drugs amphotericin B and 21 miltefosine. Our data demonstrate that etomoxir, orlistat, perhexiline, thioridazine and 22 valproic acid inhibited growth of N. gruberi. Furthermore, additive effects were seen when 23 drugs were combined. Both thioridazine and valproic acid inhibit in vitro growth of N. 24 gruberi in concentrations that can be obtained at the site of infection, which is doubtful with 25 the currently used drugs amphotericin B and miltefosine. Both thioridazine and valproic acid 26 have already been used for other diseases. As the development of new drugs and randomized 27 controlled trials for this rare disease is nearly impossible, repurposing drugs is the most 28 promising way to obtain additional drugs to combat PAM. Thioridazine and valproic acid are 29 available drugs without major side-effects and can, therefore, be used as new complementary 30 options in PAM therapy. 31 49 the pathogen to exert their killing effect, such as the antimalarials atovaquone and proguanil, 50 and the broad-spectrum antihelminthic and antiprotozoal nitazoxanide (12, 13). 51Previous research by our group showed that N. gruberi, a close relative to N. fowleri, 52 prefers fatty acids as a food source (14). This led us to the hypothesis that inhibiting fatty acid 53 oxidation (FAO) could inhibit growth or even kill the amoeba. We identified several drugs 54 that inhibit fatty acid metabolism in different parts of this pathway. As the metabolic 55 machinery of N. gruberi is highly similar to that of N. fowleri (14-16), we used N. gruberi as a 56 4 model organism to determine the effects of these compounds. We then compared the effects 57 of these inhibitors to the currently used treatment (AMB and MIL) and determined additive 58 effects of the compounds when they were combined. 59 60 Materials and Methods 61 Chemicals and amoeba culture. N. gruberi strain NEG-M (ATCC® 30224) was grown 62 axenically at 25 ˚C in modified PYNFH medium (ATCC medium 1034), as described before 63 (14). Modified PYNFH is composed of peptone, yeast extract, yeast nucleic acid, folic acid, 64 10% heat-inactivated fetal bovine serum, 100 units/ml penicillin, 100 µg/ml streptomycin and 65 40 µg/ml gentamicin. All experiments were performed using trophozoites harvested during 66 the logarithmic phase of growth. Amphotericin B (AMB), etomoxir (ETO), miltefosine 67 (MIL), thioridazine (TDZ), orlistat (ORL), perhexiline (PHX...

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Energy metabolism in anaerobic eukaryotes and Earth's late oxygenation

Zimorski

Mentel

Tielens

et al. 2019

Free Radical Biology and Medicine

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Eukaryotes arose about 1.6 billion years ago, at a time when oxygen levels were still very low on Earth, both in the atmosphere and in the ocean. According to newer geochemical data, oxygen rose to approximately its present atmospheric levels very late in evolution, perhaps as late as the origin of land plants (only about 450 million years ago). It is therefore natural that many lineages of eukaryotes harbor, and use, enzymes for oxygen-independent energy metabolism. This paper provides a concise overview of anaerobic energy metabolism in eukaryotes with a focus on anaerobic energy metabolism in mitochondria. We also address the widespread assumption that oxygen improves the overall energetic state of a cell. While it is true that ATP yield from glucose or amino acids is increased in the presence of oxygen, it is also true that the synthesis of biomass costs thirteen times more energy per cell in the presence of oxygen than in anoxic conditions. This is because in the reaction of cellular biomass with O2, the equilibrium lies very far on the side of CO2. The absence of oxygen offers energetic benefits of the same magnitude as the presence of oxygen. Anaerobic and low oxygen environments are ancient. During evolution, some eukaryotes have specialized to life in permanently oxic environments (life on land), other eukaryotes have remained specialized to low oxygen habitats. We suggest that the Km of mitochondrial cytochrome c oxidase of 0.1–10 μM for O2, which corresponds to about 0.04%–4% (avg. 0.4%) of present atmospheric O2 levels, reflects environmental O2 concentrations that existed at the time that the eukaryotes arose.

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Lipids are the preferred substrate of the protistNaegleria gruberi, relative of a human brain pathogen

Cited by 5 publications

References 27 publications

Adaptive iron utilization compensates for the lack of an inducible uptake system inNaegleria fowleriand represents a potential target for therapeutic intervention

Adaptive iron utilization compensates for the lack of an inducible uptake system inNaegleria fowleriand represents a potential target for therapeutic intervention

Inhibition of fatty acid oxidation as a new target to treat Primary Amoebic Meningoencephalitis by repurposing two well-known drugs

Energy metabolism in anaerobic eukaryotes and Earth's late oxygenation

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