Steryl glucoside is a lipid mediator in stress-responsive signal transduction

We previously reported that steryl glucoside (SG) is rapidly induced in cells from molds to humans by exposure to environmental stress (Murakami-Murofushi et al. (1997) J. Biol. Chem., 272, 486-489, Kunimoto et al. (2000) Cell Stress & Chaperones, 5, 3-7), and in mold cells SG production is followed by activation of a certain protein kinase and induction of heat shock proteins (HSP) (Maruya et al. (1997) Cell Struct. Funct., 21, 533-538). To determine the biological significance of SG in stress responsive signal transduction, we added SG to the culture of human fibroblasts and examined its effect on HSP induction. We demonstrated a rapid activation of heat shock transcription factor 1 (HSF1) to bind to heat shock element (HSE) and induction of heat shock protein 70 (HSP70) in fibroblast cells by exposure to exogenously added human major SG, cholesteryl glucoside (CG). In addition, enzyme activity to form CG from cholesterol and UDP-glucose was detected in the homogenate of fibroblast cells. These results strongly suggest that CG acts as a mediator in the early stage of stress responsive signal transduction.