Expression of heat-shock and glucose-regulated genes: differential effects of glucose starvation and hypertonicity

The hsp and grp gene families encode structurally-related proteins which are overexpressed upon physiological stress and which presumably play critical roles in protecting cells against different environmental insults. While the heat-shock proteins induced by hyperthermia have been localized to the nucleus, the glucose-regulated proteins activated by glucose deprivation have been identified in the endoplasmic reticulum. To further our understanding of the regulation of these genes, we have analyzed the expression of individual members of the two gene families under different environmental states. We have observed that, while related members of the same gene family may be coordinately induced under one physiologic state, they may also be differentially activated under a different environmental condition. Furthermore, the induction may be gradual but persistent or abrupt but transient. We have also found that related members of the two gene families may similarly be coordinately or differentially induced in response to different environmental abuses. Our observations are consistent with the belief that the regulation of the expression of stress proteins is complex.