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

Abstract

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.