Heat phock protein hsp70 overexpression protects cells from heat shock stress in mouse neuroblastoma x glioma hybrid cells

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To elucidate cellular concepts for protection against heat shock, we investigated the effect of heat shock protein (hsp70) overexpression on the receptor-mediated intracellular Ca^<2+> mobilization in mouse neuroblastoma x glioma hybrid (NG108-15) cells. In sham transfected NG108-15 cells, 2 hr-heat shock (42.5℃, 2 hr) decreased bradykinin (BX) -induced Ca mobilization to 25% of the control with restoration beginning at 6 hr and full restoration at 24 hr after heat shock. When the cells were treated with antisensc oligonucleotide to human hsp70 cDNA, heat shock abolished BK-induced Ca mobilization with no restoration thereafter. In the cells, constitutively overexpressing human hsp70, BK-induced Ca^<2+> mobilization was not affected by heat shock. These results provide strong evidence that the expression of hsp70 leads directly to protection from heat shock stress. Experiments for inositol-1,4,5-trisphosphate (IP_3) production and IPs receptor binding in heat shocked cell preparations showed that the overexpression of hsp70 completely suppressed heat shock-induced decrease in IP_3 receptor binding, with no alteration of IP_3 production. In conclusion, hsp70 may function as a cytoprotective molecule by maintaining the functional integrity of IP_3 receptor under heat shock stress.
1997-01-24