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Triacylglycerol Storage in Lipid Droplets in Procyclic Trypanosoma brucei.

Allmann S, Mazet M, Ziebart N, Bouyssou G, Fouillen L, Dupuy JW, Bonneu M, Moreau P, Bringaud F, Boshart M - PLoS ONE (2014)

Bottom Line: TFEα1 is expressed in procyclic T. brucei and present in glycosomal proteomes, Unexpectedly, a TFEα1 gene knock-out mutant still expressed wild-type levels of previously reported NADP-dependent 3-hydroxyacyl-CoA dehydrogenase activity, and therefore, another gene encodes this enzymatic activity.Homozygous Δtfeα1/Δtfeα1 mutant cells show a normal growth rate and an unchanged glycosomal proteome in procyclic T. brucei.Also, the possibility remains that TAG catabolism is completely repressed by other carbon sources in culture media or developmentally activated in post-procyclic stages in the tsetse.

View Article: PubMed Central - PubMed

Affiliation: Fakultät für Biologie, Genetik, Ludwig-Maximilians-Universität München, Biozentrum, Martinsried, Germany.

ABSTRACT
Carbon storage is likely to enable adaptation of trypanosomes to nutritional challenges or bottlenecks during their stage development and migration in the tsetse. Lipid droplets are candidates for this function. This report shows that feeding of T. brucei with oleate results in a 4-5 fold increase in the number of lipid droplets, as quantified by confocal fluorescence microscopy and by flow cytometry of BODIPY 493/503-stained cells. The triacylglycerol (TAG) content also increased 4-5 fold, and labeled oleate is incorporated into TAG. Fatty acid carbon can thus be stored as TAG in lipid droplets under physiological growth conditions in procyclic T. brucei. β-oxidation has been suggested as a possible catabolic pathway for lipids in T. brucei. A single candidate gene, TFEα1 with coding capacity for a subunit of the trifunctional enzyme complex was identified. TFEα1 is expressed in procyclic T. brucei and present in glycosomal proteomes, Unexpectedly, a TFEα1 gene knock-out mutant still expressed wild-type levels of previously reported NADP-dependent 3-hydroxyacyl-CoA dehydrogenase activity, and therefore, another gene encodes this enzymatic activity. Homozygous Δtfeα1/Δtfeα1 mutant cells show a normal growth rate and an unchanged glycosomal proteome in procyclic T. brucei. The decay kinetics of accumulated lipid droplets upon oleate withdrawal can be fully accounted for by the dilution effect of cell division in wild-type and Δtfeα1/Δtfeα1 cells. The absence of net catabolism of stored TAG in procyclic T. brucei, even under strictly glucose-free conditions, does not formally exclude a flux through TAG, in which biosynthesis equals catabolism. Also, the possibility remains that TAG catabolism is completely repressed by other carbon sources in culture media or developmentally activated in post-procyclic stages in the tsetse.

No MeSH data available.


Related in: MedlinePlus

Dendrogram of trifunctional enzyme (TFE) isoforms.Prokaryotic (black characters) and eukaryotic (colored characters) TFEα sequences are represented by their GenBank accession codes. Glycosomal/peroxisomal (TFEα1) or mitochondrial (TFEα2) proteins are highlighted in blue and red. Experimental evidence for glycosomal localization of trypanosomatid TFEα1 isoforms, which all contain a PTS2 motif, is limited to T. brucei TFEα1 (see [40] and S4 Figure). Mitochondrial localization of the trypanosomatid TFEα2 isoforms is assumed due to an N-terminal mitochondrial targeting motif and the absence of a PTS motif. Abbreviations: Lb, Leishmania braziliensis; Lm, L. major; Lmex, L. mexicana; Lt, L. tarentolae; Tb, T. brucei; Tc, T. cruzi; Tco, T. congolense. The organisms corresponding to the accession numbers are: Canis lupus familiaris (XP_545234.1), Danio rerio (NP_996951.1), Mus musculus (BAB23628.1), Curvibacter putative symbiont of Hydra magnipapillata (CBA26305.1), Janthinobacterium sp. HH01 (WP_008448388.1), Marinobacter sp. BSs20148 (YP_006559517.1), Pseudomonas stutzeri (WP_017245866.1), Ralstonia solanacearum CMR15 (YP_005996751.1), Camponotus floridanus (EFN74066.1), Drosophila grimshawi (XP_001988242.1), γ-proteobacterium HdN1 (YP_003812264.1), Hahella chejuensis KCTC2396 (YP_433438.1), Homo sapiens (P40939), Moritella dasanensis (WP_017223439.1), Parvibaculum lavamentivorans DS-1 (YP_001411745.1), Rhodothermus marinus DSM4252 (YP_003290744.1), Shewanella denitrificans OS217 (ABE53312.1), Vibrio splendidus LGP32 (YP_002416486.1), Escherichia coli (JW2338), Enterovibrio norvegicus (WP_017005631.1), Moritella marina (WP_019442678.1), Myxococcus xanthus DK1622 (YP_633521.1), Shigella flexneri (WP_000965907.1), Shewanella oneidensis MR-1 (NP_718651.1).
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pone-0114628-g004: Dendrogram of trifunctional enzyme (TFE) isoforms.Prokaryotic (black characters) and eukaryotic (colored characters) TFEα sequences are represented by their GenBank accession codes. Glycosomal/peroxisomal (TFEα1) or mitochondrial (TFEα2) proteins are highlighted in blue and red. Experimental evidence for glycosomal localization of trypanosomatid TFEα1 isoforms, which all contain a PTS2 motif, is limited to T. brucei TFEα1 (see [40] and S4 Figure). Mitochondrial localization of the trypanosomatid TFEα2 isoforms is assumed due to an N-terminal mitochondrial targeting motif and the absence of a PTS motif. Abbreviations: Lb, Leishmania braziliensis; Lm, L. major; Lmex, L. mexicana; Lt, L. tarentolae; Tb, T. brucei; Tc, T. cruzi; Tco, T. congolense. The organisms corresponding to the accession numbers are: Canis lupus familiaris (XP_545234.1), Danio rerio (NP_996951.1), Mus musculus (BAB23628.1), Curvibacter putative symbiont of Hydra magnipapillata (CBA26305.1), Janthinobacterium sp. HH01 (WP_008448388.1), Marinobacter sp. BSs20148 (YP_006559517.1), Pseudomonas stutzeri (WP_017245866.1), Ralstonia solanacearum CMR15 (YP_005996751.1), Camponotus floridanus (EFN74066.1), Drosophila grimshawi (XP_001988242.1), γ-proteobacterium HdN1 (YP_003812264.1), Hahella chejuensis KCTC2396 (YP_433438.1), Homo sapiens (P40939), Moritella dasanensis (WP_017223439.1), Parvibaculum lavamentivorans DS-1 (YP_001411745.1), Rhodothermus marinus DSM4252 (YP_003290744.1), Shewanella denitrificans OS217 (ABE53312.1), Vibrio splendidus LGP32 (YP_002416486.1), Escherichia coli (JW2338), Enterovibrio norvegicus (WP_017005631.1), Moritella marina (WP_019442678.1), Myxococcus xanthus DK1622 (YP_633521.1), Shigella flexneri (WP_000965907.1), Shewanella oneidensis MR-1 (NP_718651.1).

Mentions: A likely rationale for uptake and storage of lipids in a specific cellular compartment is later use for energy production by β-oxidation. In cell lysates of procyclic T. brucei the enzymatic activities of 2-enoyl-CoA hydratase and 3-hydroxyacyl-CoA dehydrogenase, two essential enzymatic steps in β-oxidation have previously been detected [9]. In order to explore the genomic capacity for β-oxidation in T. brucei, a bioinformatic search for candidate genes for these two activities was undertaken. The β-oxidation pathway consists of four steps, being an acyl-CoA dehydrogenation, an enoyl-CoA hydratation, a 3-hydroxyacyl-CoA dehydrogenation and a thiolytic cleavage reaction. In most organisms, the first reaction of this pathway is catalyzed by a monofunctional enzyme, while the three other reactions are catalyzed by a trifunctional enzyme (TFE) complex, composed of a bifunctional TFEα subunit (enoyl-CoA hydratase and 3-hydroxyacyl-CoA dehydrogenase activities) and a monofunctional TFEβ subunit (thiolase activity). Most eukaryotes contain two phylogenetically distinct TFEα, one located in the mitochondrion (named TFEα2) and the other in peroxisomes (named TFEα1). The Leishmania spp. and T. cruzi genomes contain one mitochondrial and one glycosomal type gene with a mitochondrial targeting motif or a peroxisomal targeting sequence 2 (PTS2) present, respectively. However, only one gene encoding the putative glycosomal TFEα1 isoform, is detected in the African trypanosome genomes (Fig. 4). We have searched by BLAST not only the Tb427 genome but also the Tb927, T. gambiense and T. congolense genomes in TritrypDB and in addition our unpublished AnTat1.1 genome assembly. There is no trace of a second TFEα-like gene in salivarian trypanosomes. This leaves T. brucei with a single candidate gene for the measured enoyl-CoA hydratase and 3-hydroxyacyl-CoA dehydrogenase activities. Therefore, the TFEα1 candidate gene was deleted by a homologous recombination-mediated homozygous gene replacement with two antibiotic resistance markers. The identity of the resulting Δtfeα1/Δtfeα1 mutant was verified by locus PCR and by Southern blot analysis (S3 Figure). As glucose starvation may induce the putative β-oxidation pathway to restore the energy balance, the growth rate of WT and Δtfeα1/Δtfeα1 mutant cells was determined in our new glucose-free medium (SDM79GluFree, see Methods) supplemented or not with 10 mM glucose. Growth of the mutant is only moderately affected compared to WT regardless of the amount of glucose (Fig. 5A). TFEα1 contains a peroxisomal targeting signal 2 motif (PTS2, RLETISSHV) [38] and has recently been found enriched in glycosomal fractions [39]. In addition, TFEα1 contains a putative 24 amino acid N-terminal mitochondrial target motif predicted by MitoProt (http://ihg.gsf.de/ihg/mitoprot.html) with a moderate probability (0.41). In absence of antibody reagents, we used proteomic analysis of glycosome enriched fractions from WT and Δtfeα1/Δtfeα1 mutant cells to probe expression and subcellular localization. We compared the ratio of peptide counts of WT over Δtfeα1/Δtfeα1 for all glycosomal proteins that Güther et al. [39] detected with confidence in their proteome of affinity purified glycosomes (Fig. 5B, S4 Figure). A ratio around 1 for all proteins detected, showed that the protein composition of glycosomes is not altered in the Δtfeα1/Δtfeα1 mutant cells. Only for TFEα1, a 140-fold ratio of peptide counts of WT over Δtfeα1/Δtfeα1 was detected and demonstrated that the candidate gene product is expressed in procyclic T. brucei. Enzymatic activity was then measured in WT and Δtfeα1/Δtfeα1 knockout cells using whole cell extracts and partially purified glycosome fractions. Only NADPH-dependent 3-hydroxyacyl-CoA dehydrogenase activity was detected with C4 substrate (Table 1), but no NADH-dependent activity (not shown). When considering the different cell fractionation methods, our values for NADPH-dependent 3-hydroxyacyl-CoA dehydrogenase activity are consistent with those previously reported in [9]. Surprisingly, the activity was not significantly different in WT and Δtfeα1/Δtfeα1 whole cell lysates and in the respective glycosome preparations. We conclude that the TFEα1 candidate gene cannot encode NADPH-dependent 3-hydroxyacyl-CoA dehydrogenase activity. A bona fide glycosomal activity, glycerol-3-phosphate dehydrogenase (GPDH), is 7-fold enriched in our partially purified glycosome preparations, while the NADPH-dependent 3-hydroxyacyl-CoA dehydrogenase activity is less than 2-fold enriched (Table 1), which is consistent with previous localization of the latter activity in several subcellular compartments [9]. We cannot formally exclude that the TFEα1 candidate gene encodes a distinct 3-hydroxyacyl-CoA dehydrogenase enzyme that is completely inactive in procyclic trypanosomes. However, the NADPH-dependent 3-hydroxyacyl-CoA dehydrogenase activity reported here and in [9] is clearly not encoded by TFEα1. As the putative β-oxidation pathway may be induced by glucose starvation, we measured the 3-hydroxyacyl-CoA dehydrogenase activity in both WT and Δtfeα1/Δtfeα1 cells grown in SDM79GluFree for one week, but no differences were observed compared to glucose-rich conditions. In summary, previous arguments in favor of a β-oxidation pathway in T. brucei now rely on the NADP-dependent and possibly anabolic activities reported in [9], whereas no metabolic function can be detected so far for the annotated TFEα1 candidate gene [38].


Triacylglycerol Storage in Lipid Droplets in Procyclic Trypanosoma brucei.

Allmann S, Mazet M, Ziebart N, Bouyssou G, Fouillen L, Dupuy JW, Bonneu M, Moreau P, Bringaud F, Boshart M - PLoS ONE (2014)

Dendrogram of trifunctional enzyme (TFE) isoforms.Prokaryotic (black characters) and eukaryotic (colored characters) TFEα sequences are represented by their GenBank accession codes. Glycosomal/peroxisomal (TFEα1) or mitochondrial (TFEα2) proteins are highlighted in blue and red. Experimental evidence for glycosomal localization of trypanosomatid TFEα1 isoforms, which all contain a PTS2 motif, is limited to T. brucei TFEα1 (see [40] and S4 Figure). Mitochondrial localization of the trypanosomatid TFEα2 isoforms is assumed due to an N-terminal mitochondrial targeting motif and the absence of a PTS motif. Abbreviations: Lb, Leishmania braziliensis; Lm, L. major; Lmex, L. mexicana; Lt, L. tarentolae; Tb, T. brucei; Tc, T. cruzi; Tco, T. congolense. The organisms corresponding to the accession numbers are: Canis lupus familiaris (XP_545234.1), Danio rerio (NP_996951.1), Mus musculus (BAB23628.1), Curvibacter putative symbiont of Hydra magnipapillata (CBA26305.1), Janthinobacterium sp. HH01 (WP_008448388.1), Marinobacter sp. BSs20148 (YP_006559517.1), Pseudomonas stutzeri (WP_017245866.1), Ralstonia solanacearum CMR15 (YP_005996751.1), Camponotus floridanus (EFN74066.1), Drosophila grimshawi (XP_001988242.1), γ-proteobacterium HdN1 (YP_003812264.1), Hahella chejuensis KCTC2396 (YP_433438.1), Homo sapiens (P40939), Moritella dasanensis (WP_017223439.1), Parvibaculum lavamentivorans DS-1 (YP_001411745.1), Rhodothermus marinus DSM4252 (YP_003290744.1), Shewanella denitrificans OS217 (ABE53312.1), Vibrio splendidus LGP32 (YP_002416486.1), Escherichia coli (JW2338), Enterovibrio norvegicus (WP_017005631.1), Moritella marina (WP_019442678.1), Myxococcus xanthus DK1622 (YP_633521.1), Shigella flexneri (WP_000965907.1), Shewanella oneidensis MR-1 (NP_718651.1).
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4262433&req=5

pone-0114628-g004: Dendrogram of trifunctional enzyme (TFE) isoforms.Prokaryotic (black characters) and eukaryotic (colored characters) TFEα sequences are represented by their GenBank accession codes. Glycosomal/peroxisomal (TFEα1) or mitochondrial (TFEα2) proteins are highlighted in blue and red. Experimental evidence for glycosomal localization of trypanosomatid TFEα1 isoforms, which all contain a PTS2 motif, is limited to T. brucei TFEα1 (see [40] and S4 Figure). Mitochondrial localization of the trypanosomatid TFEα2 isoforms is assumed due to an N-terminal mitochondrial targeting motif and the absence of a PTS motif. Abbreviations: Lb, Leishmania braziliensis; Lm, L. major; Lmex, L. mexicana; Lt, L. tarentolae; Tb, T. brucei; Tc, T. cruzi; Tco, T. congolense. The organisms corresponding to the accession numbers are: Canis lupus familiaris (XP_545234.1), Danio rerio (NP_996951.1), Mus musculus (BAB23628.1), Curvibacter putative symbiont of Hydra magnipapillata (CBA26305.1), Janthinobacterium sp. HH01 (WP_008448388.1), Marinobacter sp. BSs20148 (YP_006559517.1), Pseudomonas stutzeri (WP_017245866.1), Ralstonia solanacearum CMR15 (YP_005996751.1), Camponotus floridanus (EFN74066.1), Drosophila grimshawi (XP_001988242.1), γ-proteobacterium HdN1 (YP_003812264.1), Hahella chejuensis KCTC2396 (YP_433438.1), Homo sapiens (P40939), Moritella dasanensis (WP_017223439.1), Parvibaculum lavamentivorans DS-1 (YP_001411745.1), Rhodothermus marinus DSM4252 (YP_003290744.1), Shewanella denitrificans OS217 (ABE53312.1), Vibrio splendidus LGP32 (YP_002416486.1), Escherichia coli (JW2338), Enterovibrio norvegicus (WP_017005631.1), Moritella marina (WP_019442678.1), Myxococcus xanthus DK1622 (YP_633521.1), Shigella flexneri (WP_000965907.1), Shewanella oneidensis MR-1 (NP_718651.1).
Mentions: A likely rationale for uptake and storage of lipids in a specific cellular compartment is later use for energy production by β-oxidation. In cell lysates of procyclic T. brucei the enzymatic activities of 2-enoyl-CoA hydratase and 3-hydroxyacyl-CoA dehydrogenase, two essential enzymatic steps in β-oxidation have previously been detected [9]. In order to explore the genomic capacity for β-oxidation in T. brucei, a bioinformatic search for candidate genes for these two activities was undertaken. The β-oxidation pathway consists of four steps, being an acyl-CoA dehydrogenation, an enoyl-CoA hydratation, a 3-hydroxyacyl-CoA dehydrogenation and a thiolytic cleavage reaction. In most organisms, the first reaction of this pathway is catalyzed by a monofunctional enzyme, while the three other reactions are catalyzed by a trifunctional enzyme (TFE) complex, composed of a bifunctional TFEα subunit (enoyl-CoA hydratase and 3-hydroxyacyl-CoA dehydrogenase activities) and a monofunctional TFEβ subunit (thiolase activity). Most eukaryotes contain two phylogenetically distinct TFEα, one located in the mitochondrion (named TFEα2) and the other in peroxisomes (named TFEα1). The Leishmania spp. and T. cruzi genomes contain one mitochondrial and one glycosomal type gene with a mitochondrial targeting motif or a peroxisomal targeting sequence 2 (PTS2) present, respectively. However, only one gene encoding the putative glycosomal TFEα1 isoform, is detected in the African trypanosome genomes (Fig. 4). We have searched by BLAST not only the Tb427 genome but also the Tb927, T. gambiense and T. congolense genomes in TritrypDB and in addition our unpublished AnTat1.1 genome assembly. There is no trace of a second TFEα-like gene in salivarian trypanosomes. This leaves T. brucei with a single candidate gene for the measured enoyl-CoA hydratase and 3-hydroxyacyl-CoA dehydrogenase activities. Therefore, the TFEα1 candidate gene was deleted by a homologous recombination-mediated homozygous gene replacement with two antibiotic resistance markers. The identity of the resulting Δtfeα1/Δtfeα1 mutant was verified by locus PCR and by Southern blot analysis (S3 Figure). As glucose starvation may induce the putative β-oxidation pathway to restore the energy balance, the growth rate of WT and Δtfeα1/Δtfeα1 mutant cells was determined in our new glucose-free medium (SDM79GluFree, see Methods) supplemented or not with 10 mM glucose. Growth of the mutant is only moderately affected compared to WT regardless of the amount of glucose (Fig. 5A). TFEα1 contains a peroxisomal targeting signal 2 motif (PTS2, RLETISSHV) [38] and has recently been found enriched in glycosomal fractions [39]. In addition, TFEα1 contains a putative 24 amino acid N-terminal mitochondrial target motif predicted by MitoProt (http://ihg.gsf.de/ihg/mitoprot.html) with a moderate probability (0.41). In absence of antibody reagents, we used proteomic analysis of glycosome enriched fractions from WT and Δtfeα1/Δtfeα1 mutant cells to probe expression and subcellular localization. We compared the ratio of peptide counts of WT over Δtfeα1/Δtfeα1 for all glycosomal proteins that Güther et al. [39] detected with confidence in their proteome of affinity purified glycosomes (Fig. 5B, S4 Figure). A ratio around 1 for all proteins detected, showed that the protein composition of glycosomes is not altered in the Δtfeα1/Δtfeα1 mutant cells. Only for TFEα1, a 140-fold ratio of peptide counts of WT over Δtfeα1/Δtfeα1 was detected and demonstrated that the candidate gene product is expressed in procyclic T. brucei. Enzymatic activity was then measured in WT and Δtfeα1/Δtfeα1 knockout cells using whole cell extracts and partially purified glycosome fractions. Only NADPH-dependent 3-hydroxyacyl-CoA dehydrogenase activity was detected with C4 substrate (Table 1), but no NADH-dependent activity (not shown). When considering the different cell fractionation methods, our values for NADPH-dependent 3-hydroxyacyl-CoA dehydrogenase activity are consistent with those previously reported in [9]. Surprisingly, the activity was not significantly different in WT and Δtfeα1/Δtfeα1 whole cell lysates and in the respective glycosome preparations. We conclude that the TFEα1 candidate gene cannot encode NADPH-dependent 3-hydroxyacyl-CoA dehydrogenase activity. A bona fide glycosomal activity, glycerol-3-phosphate dehydrogenase (GPDH), is 7-fold enriched in our partially purified glycosome preparations, while the NADPH-dependent 3-hydroxyacyl-CoA dehydrogenase activity is less than 2-fold enriched (Table 1), which is consistent with previous localization of the latter activity in several subcellular compartments [9]. We cannot formally exclude that the TFEα1 candidate gene encodes a distinct 3-hydroxyacyl-CoA dehydrogenase enzyme that is completely inactive in procyclic trypanosomes. However, the NADPH-dependent 3-hydroxyacyl-CoA dehydrogenase activity reported here and in [9] is clearly not encoded by TFEα1. As the putative β-oxidation pathway may be induced by glucose starvation, we measured the 3-hydroxyacyl-CoA dehydrogenase activity in both WT and Δtfeα1/Δtfeα1 cells grown in SDM79GluFree for one week, but no differences were observed compared to glucose-rich conditions. In summary, previous arguments in favor of a β-oxidation pathway in T. brucei now rely on the NADP-dependent and possibly anabolic activities reported in [9], whereas no metabolic function can be detected so far for the annotated TFEα1 candidate gene [38].

Bottom Line: TFEα1 is expressed in procyclic T. brucei and present in glycosomal proteomes, Unexpectedly, a TFEα1 gene knock-out mutant still expressed wild-type levels of previously reported NADP-dependent 3-hydroxyacyl-CoA dehydrogenase activity, and therefore, another gene encodes this enzymatic activity.Homozygous Δtfeα1/Δtfeα1 mutant cells show a normal growth rate and an unchanged glycosomal proteome in procyclic T. brucei.Also, the possibility remains that TAG catabolism is completely repressed by other carbon sources in culture media or developmentally activated in post-procyclic stages in the tsetse.

View Article: PubMed Central - PubMed

Affiliation: Fakultät für Biologie, Genetik, Ludwig-Maximilians-Universität München, Biozentrum, Martinsried, Germany.

ABSTRACT
Carbon storage is likely to enable adaptation of trypanosomes to nutritional challenges or bottlenecks during their stage development and migration in the tsetse. Lipid droplets are candidates for this function. This report shows that feeding of T. brucei with oleate results in a 4-5 fold increase in the number of lipid droplets, as quantified by confocal fluorescence microscopy and by flow cytometry of BODIPY 493/503-stained cells. The triacylglycerol (TAG) content also increased 4-5 fold, and labeled oleate is incorporated into TAG. Fatty acid carbon can thus be stored as TAG in lipid droplets under physiological growth conditions in procyclic T. brucei. β-oxidation has been suggested as a possible catabolic pathway for lipids in T. brucei. A single candidate gene, TFEα1 with coding capacity for a subunit of the trifunctional enzyme complex was identified. TFEα1 is expressed in procyclic T. brucei and present in glycosomal proteomes, Unexpectedly, a TFEα1 gene knock-out mutant still expressed wild-type levels of previously reported NADP-dependent 3-hydroxyacyl-CoA dehydrogenase activity, and therefore, another gene encodes this enzymatic activity. Homozygous Δtfeα1/Δtfeα1 mutant cells show a normal growth rate and an unchanged glycosomal proteome in procyclic T. brucei. The decay kinetics of accumulated lipid droplets upon oleate withdrawal can be fully accounted for by the dilution effect of cell division in wild-type and Δtfeα1/Δtfeα1 cells. The absence of net catabolism of stored TAG in procyclic T. brucei, even under strictly glucose-free conditions, does not formally exclude a flux through TAG, in which biosynthesis equals catabolism. Also, the possibility remains that TAG catabolism is completely repressed by other carbon sources in culture media or developmentally activated in post-procyclic stages in the tsetse.

No MeSH data available.


Related in: MedlinePlus