Project description:Acetyl-CoA is a key metabolite in all organisms, implicated in transcriptional regulation, post-translational modification as well as fuelling the TCA cycle and the synthesis and elongation of fatty acids. The obligate intracellular parasite Toxoplasma gondii possesses two enzymes which produce acetyl-CoA in the cytosol and nucleus: the acetyl-CoA synthase (ACS) and the ATP-citrate lyase (ACL), while the branched chain α-ketoacid dehydrogenase (BCKDH) generates acetyl-CoA in the mitochondrion. Given the diverse functions of acetyl-CoA, we know little about the specific roles of distinct sub-cellular acetyl-CoA pools and how these impact overall parasite physiology. To assess the broad functions of nucleo-cytosolic as well as mitochondrial acetyl-CoA, we analysed the acetylome and total proteome of parasites lacking ACL/ACS or BCKDH.
Project description:Cytosolic acetyl-coenzyme A is a precursor for many biotechnologically relevant compounds produced by Saccharomyces cerevisiae. In this yeast, cytosolic acetyl-CoA synthesis and growth strictly depend on expression of either the Acs1 or Acs2 isoenzyme of acetyl-CoA synthetase (ACS). Since hydrolysis of ATP to AMP and pyrophosphate in the ACS reaction constrains maximum yields of acetyl-CoA-derived products, this study explores replacement of ACS by two ATP-independent pathways for acetyl-CoA synthesis. After evaluating expression of different bacterial genes encoding acetylating acetaldehyde dehydrogenase (A-ALD) and pyruvate-formate lyase (PFL), acs1M-NM-^T acs2M-NM-^T S. cerevisiae strains were constructed in which A-ALD or PFL successfully replaced ACS. In A-ALD-dependent strains, aerobic growth rates of up to 0.27 h-1 were observed, while anaerobic growth rates of PFL-dependent S. cerevisiae (0.21 h-1) were stoichiometrically coupled to formate production. In glucose-limited chemostat cultures, intracellular metabolite analysis did not reveal major differences between A-ALD-dependent and reference strains. However, biomass yields on glucose of A-ALD- and PFL-dependent strains were lower than those of the reference strain. Transcriptome analysis suggested that reduced biomass yields were caused by acetaldehyde and formate in A-ALD- and PFL-dependent strains, respectively. Transcript profiles also indicated that a previously proposed role of Acs2 in histone acetylation is probably linked to cytosolic acetyl-CoA levels rather than to direct involvement of Acs2 in histone acetylation. While, for the first time, demonstrating that yeast ACS can be fully replaced by alternative reactions, this study demonstrates that further modifications are needed to achieve optimal in vivo efficiencies of the supply of acetyl-CoA as product precursor. To investigate the impact of introduced changes in native pathway of cytosolic acetyl-CoA formation in S. cerevisiae, a DNA microarray-based transcriptome analysis was performed on aerobic or anaerobic, glucose-limited chemostat cultures.
Project description:Acetyl-CoA is a key metabolite in all organisms, implicated in transcriptional regulation, post-translational modification as well as fuelling the TCA-cycle and the synthesis and elongation of fatty acids (FAs). The obligate intracellular parasite Toxoplasma gondii possesses two enzymes which produce acetyl-CoA in the cytosol and nucleus: acetyl-CoA synthetase (ACS) and ATP-citrate lyase (ACL), while the branched-chain α-keto acid dehydrogenase-complex (BCKDH) generates acetyl-CoA in the mitochondrion. To obtain a global and integrative picture of the role of distinct sub-cellular acetyl-CoA pools, we measured the acetylome, transcriptome, proteome and metabolome of parasites lacking ACL/ACS or BCKDH. Loss of ACL/ACS results in the hypo-acetylation of nucleo-cytosolic and secretory proteins, alters gene expression broadly and is required for the synthesis of parasite-specific FAs. In contrast, loss of BCKDH causes few specific changes in the acetylome, transcriptome and proteome which allow these parasites to rewire their metabolism to adapt to the obstruction of the TCA-cycle.
Project description:Cytosolic acetyl-coenzyme A is a precursor for many biotechnologically relevant compounds produced by Saccharomyces cerevisiae. In this yeast, cytosolic acetyl-CoA synthesis and growth strictly depend on expression of either the Acs1 or Acs2 isoenzyme of acetyl-CoA synthetase (ACS). Since hydrolysis of ATP to AMP and pyrophosphate in the ACS reaction constrains maximum yields of acetyl-CoA-derived products, this study explores replacement of ACS by two ATP-independent pathways for acetyl-CoA synthesis. After evaluating expression of different bacterial genes encoding acetylating acetaldehyde dehydrogenase (A-ALD) and pyruvate-formate lyase (PFL), acs1Δ acs2Δ S. cerevisiae strains were constructed in which A-ALD or PFL successfully replaced ACS. In A-ALD-dependent strains, aerobic growth rates of up to 0.27 h-1 were observed, while anaerobic growth rates of PFL-dependent S. cerevisiae (0.21 h-1) were stoichiometrically coupled to formate production. In glucose-limited chemostat cultures, intracellular metabolite analysis did not reveal major differences between A-ALD-dependent and reference strains. However, biomass yields on glucose of A-ALD- and PFL-dependent strains were lower than those of the reference strain. Transcriptome analysis suggested that reduced biomass yields were caused by acetaldehyde and formate in A-ALD- and PFL-dependent strains, respectively. Transcript profiles also indicated that a previously proposed role of Acs2 in histone acetylation is probably linked to cytosolic acetyl-CoA levels rather than to direct involvement of Acs2 in histone acetylation. While, for the first time, demonstrating that yeast ACS can be fully replaced by alternative reactions, this study demonstrates that further modifications are needed to achieve optimal in vivo efficiencies of the supply of acetyl-CoA as product precursor.
Project description:The energetic (ATP) cost of biochemical pathways critically determines the maximum yield of metabolites of vital or commercial relevance. Cytosolic acetyl-CoA is a key precursor for biosynthesis in eukaryotes and for many industrially relevant product pathways that have been introduced into Saccharomyces cerevisiae, such as isoprenoids or lipids. In this yeast, synthesis of cytosolic acetyl-CoA via acetyl-CoA synthetase (ACS) involves hydrolysis of ATP to AMP and pyrophosphate. Here, we demonstrate that expression and assembly in the yeast cytosol of a pyruvate dehydrogenase complex (PDH) from Enterococcus faecalis can fully replace the ACS-dependent pathway for cytosolic acetyl-CoA synthesis. In vivo activity of E. faecalis PDH required the simultaneous expression of E. faecalis genes encoding its E1α, E1β, E2 and E3 subunits, as well as genes involved in lipoylation of E2 and addition of lipoate to growth media. A strain lacking ACS, that expressed these E. faecalis genes, grew at near-wild-type rates on glucose synthetic medium supplemented with lipoate, under aerobic and anaerobic conditions. A physiological comparison of the engineered strain and an isogenic Acs+ reference strain showed small differences in biomass yields and metabolic fluxes. Cellular fractionation and gel filtration studies revealed that the E. faecalis PDH subunits were assembled in the yeast cytosol, with a subunit ratio and enzyme activity similar to values reported for PDH purified from E. faecalis. This study indicates that cytosolic expression and assembly of PDH in eukaryotic industrial micro-organisms is a promising option for minimizing the energy costs of precursor supply in acetyl-CoA-dependent product pathways. For both strains - mutant strain IMY104 and reference strain CEN.PK113-7D' three independent chemostat cultures were performed. Each of the chemosta was sampled for transcriptome analysis. Samples were processed as described below.
Project description:The energetic (ATP) cost of biochemical pathways critically determines the maximum yield of metabolites of vital or commercial relevance. Cytosolic acetyl-CoA is a key precursor for biosynthesis in eukaryotes and for many industrially relevant product pathways that have been introduced into Saccharomyces cerevisiae, such as isoprenoids or lipids. In this yeast, synthesis of cytosolic acetyl-CoA via acetyl-CoA synthetase (ACS) involves hydrolysis of ATP to AMP and pyrophosphate. Here, we demonstrate that expression and assembly in the yeast cytosol of a pyruvate dehydrogenase complex (PDH) from Enterococcus faecalis can fully replace the ACS-dependent pathway for cytosolic acetyl-CoA synthesis. In vivo activity of E. faecalis PDH required the simultaneous expression of E. faecalis genes encoding its E1α, E1β, E2 and E3 subunits, as well as genes involved in lipoylation of E2 and addition of lipoate to growth media. A strain lacking ACS, that expressed these E. faecalis genes, grew at near-wild-type rates on glucose synthetic medium supplemented with lipoate, under aerobic and anaerobic conditions. A physiological comparison of the engineered strain and an isogenic Acs+ reference strain showed small differences in biomass yields and metabolic fluxes. Cellular fractionation and gel filtration studies revealed that the E. faecalis PDH subunits were assembled in the yeast cytosol, with a subunit ratio and enzyme activity similar to values reported for PDH purified from E. faecalis. This study indicates that cytosolic expression and assembly of PDH in eukaryotic industrial micro-organisms is a promising option for minimizing the energy costs of precursor supply in acetyl-CoA-dependent product pathways.
Project description:Metabolic production of acetyl-CoA has been linked to histone acetylation and gene regulation, however the mechanisms are largely unknown. We show that the metabolic enzyme acetyl-CoA synthetase 2 (ACSS2) is a critical and direct regulator of histone acetylation in neurons and of long-term mammalian memory. We observe increased nuclear ACSS2 in differentiating neurons in vitro. Genome-wide, ACSS2 binding corresponds with increased histone acetylation and gene expression of key neuronal genes. These data indicate that ACSS2 functions as a chromatin-bound co-activator to increase local concentrations of acetyl-CoA and to locally promote histone acetylation for transcription of neuron-specific genes. Remarkably, in vivo attenuation of hippocampal ACSS2 expression in adult mice impairs long-term spatial memory, a cognitive process reliant on histone acetylation. ACSS2 reduction in hippocampus also leads to a defect in upregulation of key neuronal genes involved in memory. These results reveal a unique connection between cellular metabolism and neural plasticity, and establish a link between generation of acetyl-CoA and neuronal chromatin regulation. Global survey of gene expression in CAD cells and differentiated CAD neurons following lentiviral knockdown of ACSS2 or ATP citrate lyase (ACL) (and control = scramble hairpin); survey of hippocampal gene expression changes associated with retrieval of fear memory, after ACSS2-AAV knockdown or in EGFP-AAV control (comparison of 0h vs. 1h post-memory retrieval).
Project description:Acetyl-Coenzyme A (acetyl-CoA) is a central metabolite and the acetyl source for protein acetylation, particularly histone acetylation that promotes gene expression. However, the effect of acetyl-CoA levels on histone acetylation status in plants remains unknown. Here, we show that malfunctioned cytosolic acetyl-CoA carboxylase1 (ACC1) in Arabidopsis leads to elevated levels of acetyl-CoA and promotes histone hyperacetylation predominantly at lysine 27 of histone H3 (H3K27). The increase of H3K27 acetylation (H3K27ac) is dependent on ATP-citrate lyase which cleaves citrate to acetyl-CoA in the cytoplasm, and requires histone acetyltransferase GCN5. A comprehensive analysis of the transcriptome and metabolome in combination with the genome-wide H3K27ac profiles of acc1 mutants, demonstrate the dynamic changes of H3K27ac, gene transcripts and metabolites occurring in the cell by the increased levels of acetyl-CoA. This study suggests that H3K27ac is an important link between cytosolic acetyl-CoA level and gene expression in response to the dynamic metabolic environments in plants.
Project description:In order to identify regions of the genome that display quantitative changes in acetyl-CoA, we utilized an established “spike-in” normalization method that allows the quantitative comparison of histone modifications across cell populations using defined quantities of a reference epigenome. We found that some regions of the genome are more sensitive to changes in acetyl-CoA compared to others.
Project description:Background: The biotechnology industry has extensively exploited Escherichia coli for producing recombinant proteins, biofuels etc. However, high growth rate aerobic E. coli cultivations are accompanied by acetate excretion i.e. overflow metabolism which is harmful as it inhibits growth, diverts valuable carbon from biomass formation and is detrimental for target product synthesis. Although overflow metabolism has been studied for decades, its regulation mechanisms still remain unclear. Results: In the current work, growth rate dependent acetate overflow metabolism of E. coli was continuously monitored using advanced continuous cultivation methods (A-stat and D-stat). The first step in acetate overflow switch (at μ = 0.27 ± 0.02 1/h) is the repression of acetyl-CoA synthethase (Acs) activity triggered by carbon catabolite repression resulting in decreased assimilation of acetate produced by phosphotransacetylase (Pta), and disruption of the PTA-ACS node. This was indicated by acetate synthesis pathways PTA-ACKA and POXB component expression down-regulation before the overflow switch at μ = 0.27 ± 0.02 1/h with concurrent 5-fold stronger repression of acetate-consuming Acs. This in turn suggests insufficient Acs activity for consuming all the acetate produced by Pta, leading to disruption of the acetate cycling process in PTA-ACS node where constant acetyl phosphate or acetate regeneration is essential for E. coli chemotaxis, proteolysis, pathogenesis etc. regulation. In addition, two-substrate A-stat and D-stat experiments showed that acetate consumption capability of E. coli decreased drastically, just as Acs expression, before the start of overflow metabolism. The second step in overflow switch is the sharp decline in cAMP production at μ = 0.45 1/h leading to total Acs inhibition and fast accumulation of acetate. Accumulation of acetate was also coupled to excretion of products such as orotate and N-carbomoyl-L-aspartate making it a novel carbon spilling mechanism in E. coli. Conclusion: This study is an example of how a systems biology approach allowed to propose a new regulation mechanism for overflow metabolism in E. coli shown by proteomic, transcriptomic and metabolomic levels coupled to two-phase acetate accumulation: acetate overflow metabolism in E. coli is triggered by Acs down-regulation resulting in decreased assimilation of acetic acid produced by Pta, and disruption of the PTA-ACS node. Reference samples at specific growth rate (μ) 0.11 1/h were compared to the ones acquired at μ 0.21, 0.26, 0.31, 0.36, 0.40 and 0.48 1/h