| Abstract: | Exposure to hyperthermia induces the synthesis of a set of highly conserved polypeptides known as heat shock proteins (HSPs) in cells of most organisms. Since it has been suggested that these proteins may enhance cell survival by protecting cells from heat-inflicted damage, we studied the synthesis of the major HSPs (Mr 70,000 and 85,000) in clones of normal and SV40-transformed mouse embryo cells. These transformed cells had higher basal HSP levels and consistently synthesized the major HSPs at a higher rate both at physiological temperature and after exposure to heat shock (43-45 degrees). Parallel determination of cell survival showed that the transformed cells were, nevertheless, more susceptible to killing by hyperthermia than were their normal counterparts. Therefore, we conclude that the higher intrinsic resistance of the normal cells to killing by heat is not directly related to basal HSP levels or to the degree to which synthesis of these proteins is induced following exposure to hyperthermia. Considering the abnormal energy metabolism of transformed cells and the known sensitivity of HSP synthesis to energy source restriction, we hypothesize that both basal HSP levels and their induction by heat shock are related to alterations in energy metabolism. |
