Purpose: The purpose of this study is to examine the changes in the number of HSF1 granules in the nucleus caused by different degree of heat stress.
Materials and methods: A human esophageal cancer cell line, TE-2, was used. HSF1 granules were examined in an immunofluorescence study, and the changes in the average number of HSF1 granules after heat alone or heat in combination with KNK437, Hsp inhibitor, were evaluated. A band shift of HSF1 was also determined by western blot.
Results: HSF1 granules appeared soon after the start of heating at 43 degrees C and reached a peak at 60 min and gradually disappeared after discontinuation of heat. In the fractionated heat treatment, preheating (43 degrees C, 30 min) suppressed the increase in the number of the granules during the second heating, but suppression of Hsp72 by KNK437 resulted in increase in the number of granules. Continued heating at 43 degrees C with or without KNK437 maintained the number of the granules at the peak level during heat treatment. The band shift of HSF1 examined by western blot correlated with the changes in the number of granules. The number of granules also reflected the degree of stress according to different temperature.
Conclusion: The number of HSF1 granules in the nucleus well reflected heat stress, and was almost consistent with phosphorylation of HSF1. The number of HSF1 granules would be a useful tool for evaluating different degrees of heat stress semiquantitatively.