Heat shock proteins and thermotolerance in a cultured cell line from the Mediterranean fruit fly, Ceratitis capitata

Heat shock proteins (hsps) were identified in a cell line from the Mediterranean fruit fly, Certatitis capitata Wiedemann (Diptera: Tephritidae) exposed to elevated temperatures. Cells produced three hsps (M r 87,000, 69,000, and 34,000) in response to a temperature shift from 26°C to 37°C (30–60 min) with a concomitant decrease in synthesis of most other cellular proteins. Synthesis of low M r hsps was not evident. The heat shock response is triggered within 30 min at temperatures from 33°C to 41°C. At temperatures >41°C protein synthesis was shut down. Within 2–3 h after return to 26°C, synthesis of proteins repressed at the higher temperatures resumed production while the major hsps disappear. Heat shock proteins were not produced in the presence of actinomycin D. Evaluations on the role of hsps in conferring thermotolerance to the cells showed an increase in cell viability in heat‐shocked cells over nonheat‐shocked cells (after 3 and 10 days) when subsequently placed at 45°C for 1 h, a normally lethal temperature. Heat shock alone had little effect on subsequent cell viability or growth at 26°C. These results suggest that hsps produced by these cells may aid in the maintenance of cell integrity and thus play a transitory role in thermotolerance.