Complex regulation of heat shock- and glucose-responsive genes in human cells

We have isolated a human genomic clone that encodes the glucose-responsive protein GRP78 and have used this cloned gene probe, together with a cloned HSP70 gene, to study the expression of both stress-induced genes in response to inhibitors of cellular metabolism. On the basis of the effects of this group of chemicals on GRP78 and HSP70 expression, we have identified three classes of stress gene inducers. The first class induces GRP78 expression and includes inhibitors of glycoprotein processing. The second class results in coordinate activation of both GRP78 and HSP70 synthesis and includes amino acid analogs and heavy metals. Chemicals in the third class coordinately induce GRP78 and repress HSP70 expression; this class includes the calcium ionophore A23187 and the glucose analog 2-deoxyglucose. Whereas induction of GRP78 or HSP70 expression is primarily due to transcriptional activation, chemicals that repress HSP70 expression act through posttranscriptional regulation. These results reveal that the regulation of GRP78 and HSP70 expression is complex and may be dependent on the specificity and magnitude of physiological damage.