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167. Expression of transcription factors FOXO1 and FOXO3A and genes related to oxidative stress in liver of hibernating ground squirrels
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Abstracts / Cryobiology 55 (2007) 324–378
165. Regulation of PPAR-c and PGC-1a transcription factors during hibernation in heart of thirteen-lined ground squirrels. Tarek Abd El Halim, Melanie Bouffard, Kenneth B. Storey, Carleton University, Ottawa, ON, Canada The peroxisome proliferator activated receptor (PPAR) family of transcription factors plays a key role in lipid metabolism. Appropriate regulation of lipid metabolism is important for successful hibernation. To evaluate the role of PPARs in hibernation, messenger RNA levels of PPAR-c and the PPAR-c coactivator (PGC-1a) were quantified in heart of thirteen-lined ground squirrels (Spermophilus tridecemlineatus) over a hibernation time course. PPAR-c mRNA levels increased significantly during early hibernation compared to squirrels that remained active in the cold room whereas PGC-1a mRNA was elevated during both early and long term hibernation. Western blots measured associated changes in protein levels. PPAR-c protein increased significantly in heart during entry into hibernation and upon arousal from torpor. However, PGC-1a protein was significantly lower during entrance and through to late hibernation but rose during arousal. These findings illustrate a temporal difference between mRNA and protein levels of transcription factors and might shed some light on the formation of stress granules during hibernation. (Conflicts of interest: None declared. Source of funding: NSERC Canada.) doi:10.1016/j.cryobiol.2007.10.168
166. Role of ETS1 (avian erythroblastosis virus E26 oncogene homolog 1) and Rb (Retinoblastoma) proteins in thirteen-lined ground squirrels (Spermophilus tridecemlineatus) during hibernation. Manimegala Mathialagan, Kenneth B. Storey, Carleton University, Ottawa, ON, Canada During winter hibernation in ground squirrels growth and differentiation processes are minimized. ETS transcription factors control specific genes with roles in growth and differentiation. Retinoblastoma protein (pRb) interacts with ETS1 and is a key regulator of cell-cycle progression and determination of cell fate; it also responds to stresses including hypoxia. The protein interacting ability of pRb is controlled by phosphorylation; e.g., the Epidermal Growth Factor Receptor (EGFR) induces phosphorylation of pRb at serine residues S780 and S795. We hypothesized that ETS1 and pRb play an important role in ground squirrel hibernation. Protein levels of ETS1, pRb, phospho-pRB, EGFR and phosphoEGFR were measured by Western blotting in six organs of euthermic versus hibernating squirrels. ETS protein significantly increased in brain, heart, kidney and muscle (P < 0.05) during hibernation as compared with euthermia whereas pRb was significantly higher in five organs but unchanged in heart. EGFR increased significantly in brain, lung and kid-
ney and pRb forms rose in brain, lung and kidney during hibernation. (Conflicts of interest: None declared. Source of funding: NSERC Canada.) doi:10.1016/j.cryobiol.2007.10.169
167. Expression of transcription factors FOXO1 and FOXO3A and genes related to oxidative stress in liver of hibernating ground squirrels. Oscar A. Aguilar, Kenneth B. Storey, Carleton University, Ottawa, ON, Canada Mammalian hibernation involves a strong suppression of all metabolic and physiological processes. Transcriptional suppression is a major factor since it is crucial for the hibernator to implement extreme energy conservation measures in order to survive during the winter months of food scarcity. Nevertheless, the transcriptional machinery does not remain silent during torpor and studies have identified a number of genes that are upregulated and are critical for sustaining the animal over torpor/arousal cycles. Oxidative stress is a consequence of many cellular processes, including hibernation; therefore, it is essential that cells have protective mechanisms that defend against damage caused by reactive oxygen species (ROS). In the present study, the mRNA transcript levels of FOXO1, FOXO3A, MnSOD, and p66 SHC were measured in liver of hibernating thirteen-lined ground squirrels, Spermophilus tridecemlineatus, over a torpor/arousal cycle. The protein products of these genes have distinct roles in antioxidant defence, and as the results demonstrate, are among the few genes that are selectively regulated through the hibernation cycle. FOXO transcription factors are involved in many activities such as cell cycle arrest, apoptosis, and coping with oxidative stress. The MnSOD gene is activated by FOXO transcription factors and the MnSOD enzyme is key for destroying superoxide. The adaptor protein p66SHC has vital functions in inducing signals involved in oxidative stress defence mechanisms and apoptosis. Transcript levels of all genes were highest during entrance into or early hibernation periods. FOXO1 and FOXO3A mRNA levels dropped during torpor and remained low throughout arousal. On the other hand, levels of MnSOD and p66 SHC transcripts were restored to euthermic values upon arousal, and in the case of MnSOD, levels were significantly higher 18 hours after arousal. These results show that there is transcriptional regulation of these genes over the torpor/arousal cycle, suggesting the importance of appropriate regulation of antioxidant defences to hibernation survival. (Conflicts of interest: None declared. Source of funding: NSERC Canada.) doi:10.1016/j.cryobiol.2007.10.170
Abstracts / Cryobiology 55 (2007) 324–378
165. Regulation of PPAR-c and PGC-1a transcription factors during hibernation in heart of thirteen-lined ground squirrels. Tarek Abd El Halim, Melanie Bouffard, Kenneth B. Storey, Carleton University, Ottawa, ON, Canada The peroxisome proliferator activated receptor (PPAR) family of transcription factors plays a key role in lipid metabolism. Appropriate regulation of lipid metabolism is important for successful hibernation. To evaluate the role of PPARs in hibernation, messenger RNA levels of PPAR-c and the PPAR-c coactivator (PGC-1a) were quantified in heart of thirteen-lined ground squirrels (Spermophilus tridecemlineatus) over a hibernation time course. PPAR-c mRNA levels increased significantly during early hibernation compared to squirrels that remained active in the cold room whereas PGC-1a mRNA was elevated during both early and long term hibernation. Western blots measured associated changes in protein levels. PPAR-c protein increased significantly in heart during entry into hibernation and upon arousal from torpor. However, PGC-1a protein was significantly lower during entrance and through to late hibernation but rose during arousal. These findings illustrate a temporal difference between mRNA and protein levels of transcription factors and might shed some light on the formation of stress granules during hibernation. (Conflicts of interest: None declared. Source of funding: NSERC Canada.) doi:10.1016/j.cryobiol.2007.10.168
166. Role of ETS1 (avian erythroblastosis virus E26 oncogene homolog 1) and Rb (Retinoblastoma) proteins in thirteen-lined ground squirrels (Spermophilus tridecemlineatus) during hibernation. Manimegala Mathialagan, Kenneth B. Storey, Carleton University, Ottawa, ON, Canada During winter hibernation in ground squirrels growth and differentiation processes are minimized. ETS transcription factors control specific genes with roles in growth and differentiation. Retinoblastoma protein (pRb) interacts with ETS1 and is a key regulator of cell-cycle progression and determination of cell fate; it also responds to stresses including hypoxia. The protein interacting ability of pRb is controlled by phosphorylation; e.g., the Epidermal Growth Factor Receptor (EGFR) induces phosphorylation of pRb at serine residues S780 and S795. We hypothesized that ETS1 and pRb play an important role in ground squirrel hibernation. Protein levels of ETS1, pRb, phospho-pRB, EGFR and phosphoEGFR were measured by Western blotting in six organs of euthermic versus hibernating squirrels. ETS protein significantly increased in brain, heart, kidney and muscle (P < 0.05) during hibernation as compared with euthermia whereas pRb was significantly higher in five organs but unchanged in heart. EGFR increased significantly in brain, lung and kid-
ney and pRb forms rose in brain, lung and kidney during hibernation. (Conflicts of interest: None declared. Source of funding: NSERC Canada.) doi:10.1016/j.cryobiol.2007.10.169
167. Expression of transcription factors FOXO1 and FOXO3A and genes related to oxidative stress in liver of hibernating ground squirrels. Oscar A. Aguilar, Kenneth B. Storey, Carleton University, Ottawa, ON, Canada Mammalian hibernation involves a strong suppression of all metabolic and physiological processes. Transcriptional suppression is a major factor since it is crucial for the hibernator to implement extreme energy conservation measures in order to survive during the winter months of food scarcity. Nevertheless, the transcriptional machinery does not remain silent during torpor and studies have identified a number of genes that are upregulated and are critical for sustaining the animal over torpor/arousal cycles. Oxidative stress is a consequence of many cellular processes, including hibernation; therefore, it is essential that cells have protective mechanisms that defend against damage caused by reactive oxygen species (ROS). In the present study, the mRNA transcript levels of FOXO1, FOXO3A, MnSOD, and p66 SHC were measured in liver of hibernating thirteen-lined ground squirrels, Spermophilus tridecemlineatus, over a torpor/arousal cycle. The protein products of these genes have distinct roles in antioxidant defence, and as the results demonstrate, are among the few genes that are selectively regulated through the hibernation cycle. FOXO transcription factors are involved in many activities such as cell cycle arrest, apoptosis, and coping with oxidative stress. The MnSOD gene is activated by FOXO transcription factors and the MnSOD enzyme is key for destroying superoxide. The adaptor protein p66SHC has vital functions in inducing signals involved in oxidative stress defence mechanisms and apoptosis. Transcript levels of all genes were highest during entrance into or early hibernation periods. FOXO1 and FOXO3A mRNA levels dropped during torpor and remained low throughout arousal. On the other hand, levels of MnSOD and p66 SHC transcripts were restored to euthermic values upon arousal, and in the case of MnSOD, levels were significantly higher 18 hours after arousal. These results show that there is transcriptional regulation of these genes over the torpor/arousal cycle, suggesting the importance of appropriate regulation of antioxidant defences to hibernation survival. (Conflicts of interest: None declared. Source of funding: NSERC Canada.) doi:10.1016/j.cryobiol.2007.10.170