Stress protein systems of mammalian cells.

Living organisms are known to react to a heat stress by the selective induction in the synthesis of several polypeptides. In this review we list the major stress proteins of mammalian cells that are induced by heat shock and other environments and categorize these proteins into specific subgroups: the major heat shock proteins, the glucose-regulated proteins, and the low-molecular-weight heat shock proteins. Characteristics of the localization and expression of proteins in each of these subgroups are presented. Specifically, the nuclear/nucleolar locale of certain of the major heat shock proteins is considered with respect to their association with RNA and the recovery of cells after a heat exposure. The induction of these major heat shock proteins and the repression of the glucose-regulated proteins as a result of reoxygenation of anoxic cells or by the addition of glucose to glucose-deprived cultures is described. Changes in the expression of these protein systems during embryogenesis and differentiation in mammalian and nonmammalian systems is summarized, and the protective role that some of these proteins appear to play in protecting the animal against the lethal effects of a severe heat treatment and against teratogenesis is critically examined.