Publication details

Stability of yeast cytoskeleton under cell stress



Year of publication 2000
Type Article in Periodical
Magazine / Source Folia Microbiologica
MU Faculty or unit

Faculty of Medicine

Field Microbiology, virology
Description The effects of heat, osmotic and radiation stresses on cells exposed to a lethal heat shock were studied on the model yeast Saccharomyces cerevisiae CCY 21-4-59. Cell thermoresistance or thermosensitivity was detected by their ability to form colonies (CFU) at 25 degrees C. After the transfer from 25 to 46 degrees C most cells lost their viability after a 10-min incubation and this temperature was then referred to as lethal heat shock. A 30-min preincubation of cells at 37 or 41 degrees C (referred to here as a mild heat stress) led to an increase of their resistance to the lethal heat shock. Western blotting technique (+ ECL) revealed that during mild heat stress the concentration of Hsp 104 in cells increased, while in controls only traces of this protein were detected. The Hsp 104 synthesis was apparently adaptive, because cycloheximide present during the mild heat stress effectively prevented the increase of cell thermoresistance. Accumulation of Hsp 104 was detected also by indirect immunofluorescence technique in the cytoplasm of cells after mild heat stress. The resistance to 46 degrees C heat shock could be induced also by previous osmotic shock (1 mol/L KCI) or short UV radiation. However, the stress proteins seemed to form more slowly, because the cells became thermoresistant only after a 3-h adaptation following the heat shock. In control cells the 46 degrees C lethal heat shock caused a rapid disintegration of spindle and cytoplasmic microtubules, leaving preserved only point fluorescence of spindle pole bodies. A mild heat stress (37- 41 degrees C) did not lead to the degradation of microtubules and, surprisingly, the microtubules from these pretreated cells remained stable even after the transfer of cells to 46 degrees C. Similarly, microtubules from mildly stressed cells remained stable after the transfer of cells to 0 degrees C, while in controls this cooling led to microtubule disintegration. Both osmotic and radiation stresses caused a rapid degradation of microtubules. These re-appeared within 2 to 3 h of incubation and remained then stable at 46 degrees C. Actin structures (cables and patches) were more sensitive -actin cables disappeared and polar localization of actin patches was disrupted even in mildly stressed cells. It can be concluded that the stress proteins, including Hsp 104, formed under condition of mild stress, take part in the maintenance of cell integrity during heat shock.
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