Regulation of carbon flux from amino acids into sugar phosphates in Xenopus embryos

Dworkin, Mark B.; Dworkin‐Rastl, Eva

doi:10.1016/0012-1606(90)90187-n

Cited by 21 publications

(27 citation statements)

References 23 publications

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“…Consistent with previous studies on egg metabolism, we observed a robust decrease in aspartate upon extract incubation, indicating the usage of amino acids as a fuel source in this cell type (24,25). The most notable change preceding caspase-2 activation, however, was a marked increase in LCFA metabolites.…”

supporting

confidence: 79%

“…1B). The decrease in aspartate suggests that this amino acid is likely serving as a carbon source to support extract metabolism as has been shown previously in intact Xenopus eggs (24). We also observed changes in the organic acid profile of fresh and aged extracts, including an increase in both pyruvate and lactate following extract incubation (Fig.…”

Section: Amino Acid Metabolism and The Accumulation Of Succinate And supporting

confidence: 58%

“…Several metabolic changes were observed prior to caspase activation, including a decrease in aspartate, an increase in alanine, an accumulation of succinate, and a buildup of multiple long-chain acylcarnitines, which reflect the cognate acyl-CoA pools. Although the utilization of amino acids as a carbon source was not surprising as this had been observed previously in Xenopus eggs (24), the buildup of succinate and LCFA metabolites was not anticipated. Because the metabolic profile of incubated extract showed striking similarity to previous studies of hypoxic systems, we measured mitochondrial oxygen consumption and discovered that extracts fail to consume oxygen during the assessed room temperature incubation period.…”

Section: Discussionmentioning

confidence: 91%

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Metabolomic Profiling Reveals a Role for Caspase-2 in Lipoapoptosis

Johnson

Lindblom

Robeson

et al. 2013

Journal of Biological Chemistry

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Background:Prior experiments described the metabolic regulation of caspase-2, but the underlying caspase-2-activating stimulus was unknown. Results: Metabolomics implicated an accumulation of long-chain fatty acid (LCFA) metabolites in caspase-2 activation. Conclusion: Caspase-2 is activated by an overabundance of saturated LCFAs and is required for cell death. Significance: These findings provide mechanistic insight into LCFA-induced apoptosis, highlighting a novel role for caspase-2 in this setting.

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supporting

confidence: 79%

Section: Amino Acid Metabolism and The Accumulation Of Succinate And supporting

confidence: 58%

Section: Discussionmentioning

confidence: 91%

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Metabolomic Profiling Reveals a Role for Caspase-2 in Lipoapoptosis

Johnson

Lindblom

Robeson

et al. 2013

Journal of Biological Chemistry

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“…Uniformly 14C-labeled compounds were injected into fertilized eggs, and metabolic intermediates analyzed by thin-layer chromatography as previously described (Dworkin and Dworkin-Rastl, 1990a). Extracts were separated on cellulose thin-layer plates, dried, sprayed with 1 M Na-salicylate, dried, and placed under X-ray film for ~2 months (Dworkin and Dworkin-Rastl, 1990a To estimate the accumulation of 114Clglucose-6-phosphate into glycogen, frozen eggs were lysed and suspended in 10% trichloroacetic acid (TCA), 4 x 5 pl of the TCA suspension were spotted on Whatman #I filters, and the remaining 80-pl-aliquot was prepared for chromatography (above).…”

Section: Injection Of Compounds and Analysis Of Intermediatesmentioning

confidence: 99%

Glycogen breakdown in cleaving xenopus embryos is limited by ADP

Dworkin¹,

Dworkin‐Rastl²

1992

Molecular Reproduction Devel

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Xenopus eggs contain large stores of glycogen, but this glycogen is not glycolytically processed during cleavage. The Embden-Meyerhof pathway is inhibited by the absence of pyruvate kinase activity in vivo, and lactate and pyruvate are present at relatively low levels. In the late blastula, just preceding gastrulation, lactate levels increase, indicating the onset of glycogen breakdown and glycolytic flux. Glycolysis from microinjected [14C]glucose-6-phosphate could be transiently activated, however, by the coinjection of ADP into fertilized eggs, and constitutively activated by the injection of the ATPase potato apyrase, indicating the presence of all enzymes necessary for glycolytic activity. The isozyme profiles of pyruvate kinase and malic enzyme, two enzymes involved in carbon metabolism during cleavage or in the subsequent activation of glycogen breakdown, do not change between the egg and gastrula stages. These data suggest that the activation of glycogen breakdown and glycolysis in the late blastula is probably not a result of new gene activity but may be the metabolic consequence of increased free ADP that is then able to support the pyruvate kinase reaction.

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“…Between the first embryonic cleavage and gastrulation, embryos use amino acids from yolk in preference to carbohydrates from stored glycogen as the primary carbon source (18), with mitochondrial glutamate oxidation playing a major role (19,20). Glycolysis is not active during early embryonic cleavage even though the glycolytic machinery is intact (21)(22)(23). Fertilization also triggers transient increases in cytoplasmic calcium (24 -26) which are likely to have profound effects on mitochondrial physiology because calcium regulates oxidative metabolism through effects on several matrix dehydrogenases (27)(28)(29)(30).…”

Section: Discussionmentioning

confidence: 99%

Mitochondrial Gene Expression Is Regulated at the Level of Transcription during Early Embryogenesis of Xenopus laevis

Ammini

Hauswirth

1999

Journal of Biological Chemistry

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Mitochondrial transcription in the early Xenopus laevis embryo resumes several hours before active mtDNA replication, effectively decoupling mtDNA transcription and replication. This developmental feature makes Xenopus embryogenesis an appealing model system to investigate the regulation of mitochondrial transcription. Studies reported here refine our understanding of the timing, magnitude, and mechanism of this transcriptional induction event. Northern analyses of six mitochondrial mRNAs (normalized to mtDNA) reveal that transcript levels remain basal between fertilization and gastrulation and then undergo a coordinate induction, culminating in a 20 -28-fold increase over egg levels by 48 h of development. Measurement of mitochondrial run-on transcription rates demonstrates a good correlation between transcription rates and transcript levels, showing that transcription itself is the primary determinant of transcript abundance. Experimental increases in mitochondrial ATP and energy charge also correlate with patterns of transcript levels and transcription rates, suggesting that developmental changes in the biochemical composition of the mitochondrial matrix could be regulating transcriptional activity. Consistent with this idea, transcriptional run-on rates in mitochondria of early embryos can be stimulated by the addition of tricarboxylic acid cycle intermediates to the run-on reaction. However, mitochondria of later stages do not show this response to the addition of metabolite. In combination, these data suggest that mitochondrial transcription is under metabolic regulation during early Xenopus embryogenesis.

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Regulation of carbon flux from amino acids into sugar phosphates in Xenopus embryos

Cited by 21 publications

References 23 publications

Metabolomic Profiling Reveals a Role for Caspase-2 in Lipoapoptosis

Metabolomic Profiling Reveals a Role for Caspase-2 in Lipoapoptosis

Glycogen breakdown in cleaving xenopus embryos is limited by ADP

Mitochondrial Gene Expression Is Regulated at the Level of Transcription during Early Embryogenesis of Xenopus laevis

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