Regulation of the glucose‐regulated protein genes by β‐mercaptoethanol requires de novo protein synthesis and correlates with inhibition of protein glycosylation

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Abstract
Treatment of hamster fibroblasts with the sulfhydryl‐reducing agent β‐mercaptoethanol (β‐ME) results in increased synthesis of the glucose‐regulated proteins (GRPs). The most abundant protein species being induced in 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 β‐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, β‐ME is a more potent inducer of GRP gene expression. In addition, the induction by low dosage of β‐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 ofsome post‐translocational processing step in the endoplasmic reticulum, as a result of β‐ME or other stress treatments, may provide the additional stimulation which transcriptionally activates the GRP genes to high levels.

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