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Adaptive regulation of membrane lipids and fluidity during thermal acclimation in Tetrahymena.

Nozawa Y - Proc. Jpn. Acad., Ser. B, Phys. Biol. Sci. (2011)

Bottom Line: Exposure of Tetrahymena cells to the cold temperature induces marked alterations in the lipid composition and the physical properties (fluidity) of various membranes.The increase in fatty acid unsaturation of membrane phospholipids is required to preserve the proper fluidity.In this homeoviscous adaptive response, acyl-CoA desaturase plays a pivotal role and its activity is regulated by induction of the enzyme via transcriptional activation.

View Article: PubMed Central - PubMed

Affiliation: Department of Health and Food Sciences, Tokai Gakuin University, Kakamigahara, Japan. ynozawa@giib.or.jp

ABSTRACT
The free-living eukaryotic protozoan Tetrahymena is a potentially useful model for the thermoadaptive membrane regulation because of easy growth in the axenic culture, systematic isolation of subcellular organelles, and quick response to temperature stress. Exposure of Tetrahymena cells to the cold temperature induces marked alterations in the lipid composition and the physical properties (fluidity) of various membranes. The increase in fatty acid unsaturation of membrane phospholipids is required to preserve the proper fluidity. In this homeoviscous adaptive response, acyl-CoA desaturase plays a pivotal role and its activity is regulated by induction of the enzyme via transcriptional activation.

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Related in: MedlinePlus

Changes in the level of dasaturase mRNA after (A) or during (B) temperature shift-down (39 ℃ to 15 ℃). T. thermophila grown at 35 ℃ were cooled to 15 ℃ over 25 min. After (A) or during (B) the shift-down to 15 ℃, total RNA was extracted at the indicated time intervals. Data from Nakashima et al. (1996).34)
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fig04: Changes in the level of dasaturase mRNA after (A) or during (B) temperature shift-down (39 ℃ to 15 ℃). T. thermophila grown at 35 ℃ were cooled to 15 ℃ over 25 min. After (A) or during (B) the shift-down to 15 ℃, total RNA was extracted at the indicated time intervals. Data from Nakashima et al. (1996).34)

Mentions: In order to gain further insight into induction of desaturase enzyme, we have isolated a gene that encodes Δ9-fatty acid desaturase from T. thermophila and examined its expression during cold acclimation.34) The nucleotide sequence indicates that the 1.4 kbp gene encodes a polypeptide of 292 amino acid residues which shows marked sequence similarity to Δ9 acyl-CoA desaturase from other sources, e.g. rat, mouse, and Saccharomyces. This desaturase protein has three histidine-cluster motifs (one HXXXXH and two HXXHH), and two hydrophobic regions which are conserved among Δ9 acyl-CoA desatuases. The level of the desaturase mRNA was sensitive to decreasing the temperature of the culture media, and was close to maximum immediately after the temperature was shifted down from 35 to 15 ℃ (0.8 ℃/min) (Fig. 4). Thereafter, the amount of mRNA gradually decreased with time, but remained above the control level for at least 5 h. Furthermore, during the cooling process to 15 ℃, the increased expression of the desaturase mRNA became evident at 27 ℃. Nuclear run-on analysis and actinomycin D chase experiments revealed that the elevation of the mRNA level was due to increases in both transcription and mRNA stability. These results suggest that the enhanced desaturase activity during the cold acclimation is controlled, at least in part, at the transcriptional level. However, the molecular mechanisms for signal transduction mediated by the cold stress leading to increased desaturase gene expression remain to be disclosed.


Adaptive regulation of membrane lipids and fluidity during thermal acclimation in Tetrahymena.

Nozawa Y - Proc. Jpn. Acad., Ser. B, Phys. Biol. Sci. (2011)

Changes in the level of dasaturase mRNA after (A) or during (B) temperature shift-down (39 ℃ to 15 ℃). T. thermophila grown at 35 ℃ were cooled to 15 ℃ over 25 min. After (A) or during (B) the shift-down to 15 ℃, total RNA was extracted at the indicated time intervals. Data from Nakashima et al. (1996).34)
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3313689&req=5

fig04: Changes in the level of dasaturase mRNA after (A) or during (B) temperature shift-down (39 ℃ to 15 ℃). T. thermophila grown at 35 ℃ were cooled to 15 ℃ over 25 min. After (A) or during (B) the shift-down to 15 ℃, total RNA was extracted at the indicated time intervals. Data from Nakashima et al. (1996).34)
Mentions: In order to gain further insight into induction of desaturase enzyme, we have isolated a gene that encodes Δ9-fatty acid desaturase from T. thermophila and examined its expression during cold acclimation.34) The nucleotide sequence indicates that the 1.4 kbp gene encodes a polypeptide of 292 amino acid residues which shows marked sequence similarity to Δ9 acyl-CoA desaturase from other sources, e.g. rat, mouse, and Saccharomyces. This desaturase protein has three histidine-cluster motifs (one HXXXXH and two HXXHH), and two hydrophobic regions which are conserved among Δ9 acyl-CoA desatuases. The level of the desaturase mRNA was sensitive to decreasing the temperature of the culture media, and was close to maximum immediately after the temperature was shifted down from 35 to 15 ℃ (0.8 ℃/min) (Fig. 4). Thereafter, the amount of mRNA gradually decreased with time, but remained above the control level for at least 5 h. Furthermore, during the cooling process to 15 ℃, the increased expression of the desaturase mRNA became evident at 27 ℃. Nuclear run-on analysis and actinomycin D chase experiments revealed that the elevation of the mRNA level was due to increases in both transcription and mRNA stability. These results suggest that the enhanced desaturase activity during the cold acclimation is controlled, at least in part, at the transcriptional level. However, the molecular mechanisms for signal transduction mediated by the cold stress leading to increased desaturase gene expression remain to be disclosed.

Bottom Line: Exposure of Tetrahymena cells to the cold temperature induces marked alterations in the lipid composition and the physical properties (fluidity) of various membranes.The increase in fatty acid unsaturation of membrane phospholipids is required to preserve the proper fluidity.In this homeoviscous adaptive response, acyl-CoA desaturase plays a pivotal role and its activity is regulated by induction of the enzyme via transcriptional activation.

View Article: PubMed Central - PubMed

Affiliation: Department of Health and Food Sciences, Tokai Gakuin University, Kakamigahara, Japan. ynozawa@giib.or.jp

ABSTRACT
The free-living eukaryotic protozoan Tetrahymena is a potentially useful model for the thermoadaptive membrane regulation because of easy growth in the axenic culture, systematic isolation of subcellular organelles, and quick response to temperature stress. Exposure of Tetrahymena cells to the cold temperature induces marked alterations in the lipid composition and the physical properties (fluidity) of various membranes. The increase in fatty acid unsaturation of membrane phospholipids is required to preserve the proper fluidity. In this homeoviscous adaptive response, acyl-CoA desaturase plays a pivotal role and its activity is regulated by induction of the enzyme via transcriptional activation.

Show MeSH
Related in: MedlinePlus