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- Krivoruchko, Anastasia, 1984, et al.
(författare)
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Activation of the carbohydrate response element binding protein (ChRESP) in response to anoxia in the turtle Trachemys scripta elegans
- 2014
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Ingår i: Biochimica et Biophysica Acta - General Subjects. - : Elsevier BV. - 1872-8006 .- 0304-4165. ; 1840:10, s. 3000-3005
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Tidskriftsartikel (refereegranskat)abstract
- Background: ChREBP (carbohydrate response element binding protein) is a glucose-responsive transcription factor that is known to be an important regulator of glycolytic and lipogenic genes in response to glucose. We hypothesized that activation of ChREBP could be relevant to anoxia survival by the anoxia-tolerant turtle, Trachemys scripta elegans. Methods: Expression of ChREBP in response to 5 and 20 h of anoxia was examined using RT-PCR and Western immunoblotting. In addition, subcellular localization and DNA-binding activity of ChREBP protein were assessed and transcript levels of liver pyruvate kinase (LPK), a downstream gene under ChREBP control were quantified using RT-PCR. Results: ChREBP was anoxia-responsive in kidney and liver, with transcript levels increasing by 1.2-1.8 fold in response to anoxia and protein levels increasing by 1.8-1.9 fold. Enhanced nuclear presence under anoxia was also observed in both tissues by 22-2.8 fold. A 4.2 fold increase in DNA binding activity of ChREBP was also observed in liver in response to 5 h of anoxia. In addition, transcript levels of LPK increased by 2.1 fold in response to 5 h of anoxia in the liver. Conclusions: The results suggest that activation of ChREBP in response to anoxia might be a crucial factor for anoxia survival in turtle liver by contributing to elevated glycolytic flux in the initial phases of oxygen limitation. General significance: This study provides the first demonstration of activation of ChREBP in response to anoxia in a natural model of anoxia tolerance, further improving our understanding of the molecular nature of anoxia tolerance.
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| 2. |
- Krivoruchko, Anastasia, 1984, et al.
(författare)
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Activation of the unfolded protein response during anoxia exposure in the turtle Trachemys scripta elegans
- 2013
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Ingår i: Molecular and Cellular Biochemistry. - : Springer Science and Business Media LLC. - 0300-8177 .- 1573-4919. ; 374:1-2, s. 91-103
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Tidskriftsartikel (refereegranskat)abstract
- Red-eared slider turtles, Trachemys scripta elegans, can survive for several weeks without oxygen when submerged in cold water. We hypothesized that anaerobiosis is aided by adaptive up-regulation of the unfolded protein response (UPR), a stress-responsive pathway that is activated by accumulation of unfolded proteins in the endoplasmic reticulum (ER) and functions to restore ER homeostasis. RT-PCR, western immunoblotting and DNA-binding assays were used to quantify the responses and/or activation status of UPR-responsive genes and proteins in turtle tissues after animal exposure to 5 or 20 h of anoxic submergence at 4 C. The phosphorylation state of protein kinase-like ER kinase (PERK) (a UPR-regulated kinase) and eukaryotic initiation factor 2 (eIF2α) increased by 1.43-2.50 fold in response to anoxia in turtle heart, kidney, and liver. Activation of the PERK-regulated transcription factor, activating transcription factor 4 (ATF4), during anoxia was documented by elevated atf4 transcripts and total ATF4 protein (1.60-2.43 fold), increased nuclear ATF4 content, and increased DNA-binding activity (1.44-2.32 fold). ATF3 and GADD34 (downstream targets of ATF4) also increased by 1.38-3.32 fold in heart and liver under anoxia, and atf3 transcripts were also elevated in heart. Two characteristic chaperones of the UPR, GRP78, and GRP94, also responded positively to anoxia with strong increases in both the transcript and protein levels. The data demonstrate that the UPR is activated in turtle heart, kidney, and liver in response to anoxia, suggesting that this pathway mediates an integrated stress response to protect tissues during oxygen deprivation. © 2012 Springer Science+Business Media New York.
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| 3. |
- Krivoruchko, Anastasia, 1984, et al.
(författare)
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Anoxia-responsive regulation of the FoxO transcription factors in freshwater turtles, Trachemys scripta elegans
- 2013
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Ingår i: Biochimica et Biophysica Acta - General Subjects. - : Elsevier BV. - 1872-8006 .- 0304-4165. ; 1830:11, s. 4990-4998
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Tidskriftsartikel (refereegranskat)abstract
- Background The forkhead class O (FoxO) transcription factors are important regulators of multiple aspects of cellular metabolism. We hypothesized that activation of these transcription factors could play crucial roles in low oxygen survival in the anoxia-tolerant turtle, Trachemys scripta elegans. Methods Two FoxOs, FoxO1 and FoxO3, were examined in turtle tissues in response to 5 and 20 h of anoxic submergence using techniques of RT-PCR, western immunoblotting and DNA-binding assays to assess activation. Transcript levels of FoxO-responsive genes were also quantified using RT-PCR. Results FoxO1 was anoxia-responsive in the liver, with increases in transcript levels, protein levels, nuclear levels and DNA-binding of 1.7-4.8 fold in response to anoxia. Levels of phosphorylated FoxO1 also decreased to 57% of control values in response to 5 h of anoxia, indicating activation. FoxO3 was activated in the heart, kidney and liver in response to anoxia, with nuclear levels increasing by 1.5-3.7 fold and DNA-binding activity increasing by 1.3-2.9 fold. Transcript levels of two FoxO-target genes, p27kip1 and catalase, also rose by 2.4-2.5 fold in the turtle liver under anoxia. Conclusions The results suggest that the FoxO transcription factors are activated in response to anoxia in T. scripta elegans, potentially contributing to the regulation of stress resistance and metabolic depression. General significance This study provides the first demonstration of activation of FoxOs in a natural model for vertebrate anoxia tolerance, further improving understanding of how tissues can survive without oxygen. © 2013 Elsevier B.V.
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