Simultaneous activation of heat shock and oxidative stress pathways by celastrol

Stress response pathways allow cells to rapidly sense and respond to deleterious environmental changes, including those caused by pathophysiological disease states. A previous screen for small molecules capable of activating the human heat shock response identified the triterpenoid celastrol as a potent activator of the heat shock transcription factor HSF1. We show here that celastrol likewise activates the homologous Hsf1 of Saccharomyces cerevisiae. Celastrol induced Hsf1 hyperphosphorylation and concurrently activated a synthetic transcriptional reporter as well as endogenous inducible Hsp70 proteins at the same effective concentration seen in mammalian cells. Moreover, celastrol treatment conferred significant resistance to subsequent lethal heat shock. Transcriptional profiling experiments revealed that in addition to Hsf1, celastrol treatment induced the Yap1-dependent oxidant defense regulon. Oxidative stress-responsive genes were likewise induced in mammalian cells, demonstrating that celastrol simultaneously activates two major cellular stress-mediating pathways. As the induction of cellular stress pathways has implications in the treatment of a variety of human diseases including neurodegenerative diosorders, cardiovascular disease and cancer, celastrol thus represents an attractive therapeutic compound. Keywords: single-dose, single time-point gene induction by natural small molecule celastrol compared to heat shock in wild type (BY4741) Saccahromyces cerevisiae Two heat shock experiments and two drug treatment experiments were conducted and analyzed independently. Heat shock arrays are 39 vs. 30 degrees for 30 min, and drug (celastrol) arrays are 10 µM celastrol in DMSO over DMSO alone, same volumes. Expression numbers are duplicated and averaged on each chip, normalized to the median signal of all hybridizations on the chip.