Abstract
ABSTRACT Geldanamycin (GA) specifically binds to HSP90 and disrupts the interaction of HSP90 and its target proteins. The binding will lead to substrate protein dissociation from HSP90 and may affect their structures and functions. Herein, we showed that exposure of non-small lung cancer H460 cells to 0.5 mM GA leads to enhancement of the synthesis of the 70 kDa heat shock proteins (HSP70s). The induction of HSP70s by GA is concentration- and time-dependent and this process coincides to the accumulation of its mRNA. By using the specific probes for hsp70-1 and hsp70b, we found that HSP70-1 is abundantly involved in GA-induced HSP70s. Furthermore importantly, we demonstrated for the first time that the PKC pathway is significant in this process since it is inhibited by H-7 and H-8 but not affected by HA1043. Similar results can be found in the protein and mRNA level. These data lead us to conclude that PKC pathway plays a major role in the GA-induced HSP70-1 expression in H460 cells. By using the electrophoretic mobility shift assay (EMSA), we showed that proximal Heat shock element (HSE1) was responsible for the inducible expression of HSP70. We found that the nuclear extracts prepared from GA-treated cells exhibited a significant increase in binding activity toward Heat shock element. Moreover, this increase in binding activity toward the Heat shock element is reduced by H-7 and H-8 but not affected by HA1004. We concluded that the PKC pathway is the major pathway involved in GA-induced expression of HSP70-1 in H460 cells.