Some forms of stress, such as heat shock, starvation and high salt, rapidly induced sterylglucoside (SG)in slimemold and human fibroblasts. In a true slime mold, Physarum polycephalum, induction of poriferasteryl glucoside wasfollowed by activation of a novel protein kinase and HSP production. In human fibroblasts, heat shock rapidlyinduced cholesteryl glucoside, then subsequent HSF(heat shock factor)activation and HSP (heat shock protein)induction occurred. As glycosylation of membrane sterol might be a very early and crucial step in the stress-inducedsignal transduction, we hypothesized that SG functions as a crucial lipid mediator in the process of stress responses. We showed that CG itself induced HSF activation and following HSP70 production when CG was added to a cultureof human fibroblasts, and we also showed that CG strongly inhibited gastric ulcer formation in rats under cold-restraint stress. This effect is likely mediated by HSP induction. Also, we compared the effect of CG(cholesteryl glu-coside)on ulcer formation and HSP70 induction with that of a popular effective anti-ulcer agent, geranylgeranylace-tone (GGA). Furthermore, we developed a highly sensitive assay method for the detection of CG formation, and char-acterized novel type of sterol glucosyltransferase (SGTase)in animal tissue and cultured human cells.
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