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Effect of amiodarone on thermotolerance and Hsp104p synthesis in the yeast Saccharomyces cerevisiae.

Siberian Institute of Plant Physiology and Biochemistry, Siberian Division of the Russian Academy of Sciences, Irkutsk, Russia.
Biochemistry (Moscow) (Impact Factor: 1.15). 01/2012; 77(1):78-86. DOI: 10.1134/S0006297912010099
Source: PubMed

ABSTRACT Amiodarone (AMD) is known to induce a transient increase in cytosolic Ca2+ level in cells of the yeast Saccharomyces cerevisiae. In the present study the effect of AMD on the thermotolerance and Hsp104p synthesis of the yeast was studied. AMD induced Hsp104p synthesis and increased survival of the yeast after a severe heat shock (50°C). The development of thermotolerance to a considerable extent depended on the presence of Hsp104p. The same effect was achieved by treatment with the classical uncoupler CCCP, which is also known to increase the cytosolic Ca2+ level. It is supposed that the change in intracellular Ca2+ concentration plays an important role in activation of the HSP104 gene expression and in increasing the thermotolerance of the yeast. The possible link between mitochondrial activity and calcium homeostasis is discussed.

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    ABSTRACT: Heat stress in plants elevates the potential across the inner mitochondrial membrane (mtΔψ) and activates the expression of heat shock proteins (HSPs). The treatment of Saccharomyces cerevisiae cells with amiodarone (AMD) elevated the cytosolic Ca2+ level ([Ca2+]cyt) in parallel with (mtΔψ) increase and led to the induction of Hsp104 synthesis. The hyperpolarization was presumably due to the increase in [Ca2+]cyt. In the present study the effects of AMD (0–100 μM) on cell viability, HSP expression, mtΔψ, and [Ca2+]cyt were investigated using the cell culture of Arabidopsis thaliana (L.) Heynh. The treatment of cultured cells with AMD led to the elevation of [Ca2+]cyt, which was accompanied by the increase in mtΔψ and by activation of HSP101 expression. The increase in [Ca2+]cyt and expression of HSP101 were also observed upon the treatment with the protonophore CCCP (carbonyl cyanide m-chlorophenylhydrazone, 4 μM) known to diminish mtΔψ. The results suggest that plant cell mitochondria modulate the cytosolic Ca2+ level by changing the potential at the inner mitochondrial membrane and, thereby, participate in the retrograde regulation of HSP101 expression.
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    ABSTRACT: Mild heat stress induces the expression of heat shock proteins (HSPs) that protect plants from death during damaging heat treatments. It was assumed that the appearance in the cell of denatured proteins triggers the expression of HSP; however, recent results show that protein denaturation is not a prerequisite for this process. In this work we discuss a hypothetical mechanism for activation under heat stress of HSP expression promoted by short-term elevation of cytosolic Ca2+ level. According to our hypothesis, a prolonged elevation of Ca2+ has a negative influence on HSP expression. Therefore, calcium is transported from the cytosol into intracellular compartments, including mitochondria. The Ca2+ entry into mitochondria is accompanied by hyperpolarization of the inner mitochondrial membrane and by the increased production of reactive oxygen species (ROS). The increased ROS production contributes to the activation of HSP expression under mild heat stress but leads to plant death under severe heat shock. Thus, mitochondria and, possibly, other organelles play the crucial role in determining life or death fate of heat-treated plant cells by controlling the cytosolic Ca2+ content and ROS production.
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