MOLECULAR MCHANISM OF CYTOSKELETON-MEDIATED STRESS RESPONSE IN GASTRIC MUCOSAL CELLS.

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Oxodative stress initiates S-thiolation of specific proteins including actin in cultured gastric mucosal cells. This reversible modification of actic has been suggested to play an importent role in preserving microfilament dynamics under oxidative stress. To test a hypothesis that intracellular glutathione may regulate in sensing and signal transduction of stress response, I examined the induction of heat shock proteins (HSPs) in glutathione-depleted gastric cells.When primary cultures of gastric mucosal cells from guinea pigs were exposed to heat (43ﾟC), ethanol, hydrogen peroxide, or diamide, they rapidly synthesized HSPs. Heat stress induced HSP90, HSP72, and HSC73, and ethanol prominently induced HSP60. In addition to these HSPs, hydrogen peroxide and diamide increased in the syntheses of several undefined proteins. None of these proteins were induced by exposure to the stressors, when intracellular glutathione was depleted to less than 10% of control values by pretreatment of cells with DL-buthionine-[S,R]-sulfoximine (BSO). Gel morbility shift assay using a synthetic oligonucleotide coding HSP72 heat shock element did not show any activation of heat shock factor (HSF) in glutathione-depleted cells exposed to heat, and subsequently no accumulation of HSP72 mRNA was detected in the cells. Immunoblot analysis with ant-HSF1 showed that the amount of HSF1 protein was not decreased by treatment with BSO,but the protein was not recovered in nuclear proteins extracted from BSO-pretreated cells. These results suggest that glutathione may serve a role in mucosal protection through the transcriptional activation of heat shock genes in gastric mucosal cells.