Relationship between Cell Survival and Heat-stress Protein Synthesis in a Drosophila Cell Line

Summary

Heat-stress protein (hsp) kinetics and clonogenic survival were studied at 33, 37 and 42°C in a continuous Drosophila cell line, WR69-DM-1. Induction and repression of hsp were temperature-dependent and independently modulated. The subsequent cell-survival curves were complex; however, survival generally decreased in a time- and temperature-dependent manner during continuous heating at 33, 37 or 42°C. Constant 33°C heating induced five hsp at 90, 72, 70, 24 and 19 kilodaltons (kDa). A 30 min 33°C heat dose led to thermotolerance after 1, 3 or 6 h incubations at 28°C. The hsp synthesized after this dose were quickly repressed, suggesting the cells were able to respond to this stress. Increasing the challenge temperature to 37°C induced three additional hsp at 34, 22 and 14 kDa, but hsp synthesis did not lead to thermotolerance over the 6 h interval. The number and intensity of hsp synthesized was higher and repression was much slower than at 33°C. Heating at 42°C inhibited all protein synthesis, and thermotolerance was not observed. Direct survival data are critical to understanding the role and function of hsp in Drosophila thermotolerance since the relevance of information on number and kinetics of hsp synthesis and their subsequent localization is dubious without it.

• thermotolerance
• heat-stress proteins
• Drosophila cell line
• survival