Impaired induction of heat shock protein implicated in decreased thermotolerance in a temperature-sensitive multinucleated cell line
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- Cao, Y., Matsumoto, T., Motomura, K. et al. Pflügers Arch (1998) 437: 15. doi:10.1007/s004240050740
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Cells of a temperature-sensitive mutant line (tsFT101) derived from a mouse mammary carcinoma cell line (FM3A) become multinucleated at a non-permissive temperature of 39°C because of disturbed cytokinesis. To explore how this relates to thermotolerance, we examined the proliferative activity of, and heat shock protein (HSP) expression in, FM3A and tsFT101 cells cultured at 37°C and 39°C after heat shock pretreatment (15 min exposure at 45°C). FM3A cells developed thermotolerance when cultured at both 37°C and 39°C, but whereas tsFT101 cells developed thermotolerance at 37°C, this was markedly reduced at 39°C. Western blot analysis showed similar degrees of expression of constitutive HSP70 (HSP73) in FM3A and tsFT101 cells after heat shock pretreatment at both 37°C and 39°C. However, expression of inducible HSP70 (HSP72) was reduced in tsFT101 cells at 39°C compared to 37°C and to FM3A cells at both 37°C and 39°C. Heat shock pretreatment activated DNA binding of heat shock transcription factor (HSF) in FM3A cells at 37°C and 39°C, but only at 37°C in tsFT101 cells. These results indicate that (1) multinucleation caused by disturbed cytokinesis increases temperature sensitivity, (2) HSP70 is critical for the development of thermotolerance in both FM3A and tsFT101 cells, and (3) decreased expression of inducible HSP70 parallels deficient development of thermotolerance in tsFT101 cells cultured at a non-permissive temperature.