Regulation of the glucose-regulated protein genes by beta-mercaptoethanol requires de novo protein synthesis and correlates with inhibition of protein glycosylation.

Treatment of hamster fibroblasts with the sulfhydryl-reducing agent beta-mercaptoethanol (beta-ME) results in increased synthesis of the glucose-regulated proteins (GRPs). The most abundant protein species being induced is the GRP78, with a minor increase also observed for GRP94. The enhanced synthesis of the GRP94 and GRP78 is primarily due to an increase in the steady state levels of the two GRP transcripts. Although beta-ME has a general inhibitive affect on amino acid uptake and protein synthesis, compared to other protein synthesis inhibitors such as cycloheximide, puromycin, and amino acid analogue canavanine, beta-ME is a more potent inducer of GRP gene expression. In addition, the induction by low dosage of beta-ME requires de novo protein synthesis and is preceded by a drop in the rate of protein glycosylation. Our results support the hypothesis that denatured proteins can induce the GRP genes; however, a blockage of some post-translocational processing step in the endoplasmic reticulum, as a result of beta-ME or other stress treatments, may provide the additional stimulation which transcriptionally activates the GRP genes to high levels.