Differential expression of Hsp90 isoforms in geldanamycin-treated 9L cells

In mammals, two major Hsp90 isoforms (Hsp90α and Hsp90β) have been identified and found to be highly conserved among different species. However, the expression control of Hsp90 isoforms at both transcriptional and translational levels is largely unknown. Herein, we quantitatively investigate the changes in the total mRNA and inductive protein levels of Hsp90α and Hsp90β in rat gliosarcoma cells treated with geldanamycin (GA). The stability of mRNA and protein was estimated. The translational efficiency of Hsp90 isoforms was measured employing in vitro translation techniques. It was found that Hsp90α was more inducible than Hsp90β after GA treatment, whereas the hsp90α mRNA level was lower than that of hsp90β. In addition, higher translational efficiency of hsp90α mRNA was observed, suggesting that translational control played an important role. Taken together, our results indicate that differential expression between Hsp90α and Hsp90β is a consequence of both distinct mRNA profiles and differential translation processes.