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Gene Expression in S49 Deathless (D-) cell variant

ABSTRACT: The second messenger cAMP acts via protein kinase A (PKA) to induce apoptosis by mechanisms that are poorly understood. Here, we assessed a role for mitochondria and analyzed gene expression in cAMP/PKA-promoted apoptosis by comparing wild-type (WT) S49 lymphoma cells and the S49 variant, D- (cAMP-deathless), which lacks cAMP-promoted apoptosis but has wild-type levels of PKA activity and cAMP-promoted G1 growth arrest. Treatment of WT, but not D-, S49 cells with 8-CPT-cAMP for 24 h induced loss of mitochondrial membrane potential, mitochondrial release of cytochrome c and Smac and increase in caspase-3 activity. Gene expression analysis (using Affymetrix 430 2.0 Arrays) revealed that WT and D- cells incubated with 8-CPT-cAMP have similar, but non-identical, extents of cAMP-regulated gene expression at 2h (~800 transcripts) and 6h (~1000 transcripts) (|Fold|>2, P<0.06); by contrast, at 24h ~2500 and ~1100 transcripts were changed in WT and D- cells, respectively. Using an approach that combined regression analysis, clustering and functional annotation to identify transcripts that showed differential expression between WT and D- cells, we found differences in cAMP-mediated regulation of mRNAs involved in transcriptional repression, apoptosis, the cell cycle, RNA splicing, Golgi and lysosomes. The 2 cell lines differed in CREB phosphorylation and expression of the transcriptional inhibitor Icer and in cAMP-regulated expression of genes in the Inhibitor of apoptosis (IAP) and Bcl families. The findings indicate that cAMP/PKA-promoted apoptosis of lymphoid cells occurs via mitochondrial-mediated events and imply that such apoptosis involves gene networks in multiple biochemical pathways. Keywords: time course

ORGANISM(S): Mus musculus

PROVIDER: GSE9727 | GEO | 2007/12/12

SECONDARY ACCESSION(S): PRJNA103643

REPOSITORIES: GEO

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Project description:The second messenger cAMP acts via protein kinase A (PKA) to induce apoptosis by mechanisms that are poorly understood. Here, we assessed a role for mitochondria and analyzed gene expression in cAMP/PKA-promoted apoptosis by comparing wild-type (WT) S49 lymphoma cells and the S49 variant, D- (cAMP-deathless), which lacks cAMP-promoted apoptosis but has wild-type levels of PKA activity and cAMP-promoted G1 growth arrest. Treatment of WT, but not D-, S49 cells with 8-CPT-cAMP for 24 h induced loss of mitochondrial membrane potential, mitochondrial release of cytochrome c and Smac and increase in caspase-3 activity. Gene expression analysis (using Affymetrix 430 2.0 Arrays) revealed that WT and D- cells incubated with 8-CPT-cAMP have similar, but non-identical, extents of cAMP-regulated gene expression at 2h (~800 transcripts) and 6h (~1000 transcripts) (|Fold|>2, P<0.06); by contrast, at 24h ~2500 and ~1100 transcripts were changed in WT and D- cells, respectively. Using an approach that combined regression analysis, clustering and functional annotation to identify transcripts that showed differential expression between WT and D- cells, we found differences in cAMP-mediated regulation of mRNAs involved in transcriptional repression, apoptosis, the cell cycle, RNA splicing, Golgi and lysosomes. The 2 cell lines differed in CREB phosphorylation and expression of the transcriptional inhibitor Icer and in cAMP-regulated expression of genes in the Inhibitor of apoptosis (IAP) and Bcl families. The findings indicate that cAMP/PKA-promoted apoptosis of lymphoid cells occurs via mitochondrial-mediated events and imply that such apoptosis involves gene networks in multiple biochemical pathways. Experiment Overall Design: S49 D- cells were treated with 8-CPT-cAMP over the course of 24 hours. Cells were prepared for hybridization to microarrays at times 0-untreated, 2h, 6h, and 24h after treatment with 8-CPT-cAMP. Experimental replicates were as follows n=4 for time 0 and n=3 for 2, 6, and 24h post treatment.

Project description:Damage to the mitochondrial genome (mtDNA) severely affects the cell and causes disease. Mutations to mtDNA also accumulate throughout the lifespan of many organisms and may be a proximal cause of aging. There is no effective treatment for ailments caused by mtDNA mutation. Since mitochondrial function and biogenesis are controlled by the nutrient environment of the cell, it is possible that perturbation of conserved, nutrient-sensing pathways may successfully treat mitochondrial disease. Experiments using the tractable eukaryote Saccharomyces cerevisiae allow us to investigate the connection between nutrient-sensing and mitochondrial function. We have focused our current studies on the protein kinase A (PKA) pathway, which controls S. cerevisiae behavior according to glucose availability. We found that reduced PKA signaling can lead, in a background-dependent manner, to improved fitness after mtDNA loss. Specifically, over-expression of the cyclic AMP phosphodiesterase Pde2p, removal of PKA isoform Tpk3p, or ablation of other proteins promoting PKA activity leads to improved proliferation of cells deleted of the mitochondrial genome. Over-expression of Pde2p also suppresses the inviability of several mutants that normally cannot survive mtDNA loss. Moreover, Pde2p over-expression diminishes the nuclear transcriptional response to mtDNA damage, further supporting the idea that glucose sensation is harmful for cells lacking the mitochondrial genome. These findings are heavily dependent upon yeast genetic background. Interestingly, robust import of mitochondrial polytopic membrane proteins may be required in order for cells with no mtDNA to receive the full benefits of PKA reduction. Our findings support the idea that perturbation of nutrient-sensing pathways, and specifically the sensation of glucose, may benefit cells with dysfunctional mitochondria. Four experimental conditions were used: BY4743 (WT) cells containing empty pRS426 vector and containing mtDNA because EtBr was not used, BY4743 (WT) cells containing empty pRS426 vector and lacking mtDNA after 24 hours of treatment with 25 µg/ml ethidium bromide, BY4743 (WT) cells overexpressing TIP41 from plasmid pRS426 and lacking mtDNA after 24 hours of treatment with 25 µg/ml ethidium bromide, and BY4743 (WT) cells overexpressing PDE2 from plasmid pRS426 and lacking mtDNA after 24 hours of treatment with 25 µg/ml ethidium bromide. Two replicates were performed for each sample type.

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Gene Expression in S49 Deathless (D-) cell variant

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