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The function of heat-shock proteins in stress tolerance.

1994; Wiley; Volume: 18; Issue: 6 Linguagem: Inglês

10.1006/cbir.1994.1087

1095-8355

A. Venetianer, Melinda K. Pirity, Anna HEVÉR‐SZABÓ,

Genetics, Aging, and Longevity in Model Organisms

ABSTRACT We earlier demonstrated that hsp68 is deficiently induced upon stress in the glucocorticoid‐resistant, dedifferentiated Reuber rat hepatoma clone 2 cells, but is strongly activated in the differentiated, glucocorticoid‐sensitive Faza 967 cells from which clone 2 was derived. We used the two cell types to address the questions whether hsp68 is specifically involved in the development of thermotolerance and/or thermoresistance or drug resistance. Our experiments show that clone 2 cells were not protected from the killing effect of heat by pretreatment with sodium arsenite, whereas Faza 967 cells were. These results strongly suggest a role of hsp68 in the development of thermotolerance in hepatoma cells. Stable heat‐resistant variants of clone 2 cells were also isolated, where an increased basal expression of several hsps was observed together with the (at least partial) restoration of the heat‐inducibility of hsp68. These results suggest that several hsps are needed to protect the critical biological processes at high temperature. The heat‐resistant hepatoma cells also became resistant to several anticancer drugs. The multidrug resistance of the hepatoma variants correlates with the overexpression of the plasma membrane P‐glycoprotein. Our results showing that severely stressed hepatoma cells overexpressed the mdr gene(s) raise the possibility that the P‐gp may participate in protection against environmental stress such as heat.