EFFECTS OF THE OVEREXPRESSION OF THE SMALL HEAT-SHOCK PROTEIN, HSP27,ON THE SENSITIVITY OF HUMAN FIBROBLAST CELLS EXPOSED TO OXIDATIVE STRESS

The role oi the human small heat shock protein (HSP27) in oxidative st ress was examined using stable transformants of an immortalized human fibroblast cell line (KMST-6) isolated by transfection of HSP27 expres sion vectors. Several stable transformants that expressed high or low levels oi HSP27 protein were obtained. Clones expressing high levels o f HSP27 were more sensitive to growth inhibition by a low dose of hydr ogen peroxide (0.1 mM) than those expressing low levels. Clones expres sing high levels of HSP27 did not acquire obvious resistance to hypert hermy and cytotoxic agents, except for one (#13), in which resistance to cytotoxic agents was increased. The level of phosphorylated HSP27 i n clones expressing high levels of this protein increased at 30 min an d was sustained even 4 hours after exposing the cells to 0.1 mM of hyd rogen peroxide. On the other hand, the levels in clones expressing low levels of HSP27 were reduced within 4 hours after exposure to hydroge n peroxide. Furthermore, overexpression of nonphosphorylatable mutant HSP27 did not affect sensitivity to oxidative stress. These results su ggested that constitutively high expression of HSP27 in KMST-6 cells m ake them susceptible to oxidative stress resulting in growth arrest, a nd this mechanism could involve the phosphorylation of HSP27. (C) 1995 Wiley-Liss, Inc.