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.

A rabbit antiserum has been prepared using as antigen the 110,000-dalton mammalian heat-shock protein. This protein was purified for injection by two-dimensional PAGE of heat-shocked Chinese hamster ovary cells. Characterization by immunoautoradiography and immunoprecipitation reveals that the antiserum is specific for the 110,000-dalton protein.Both techniques also reveal that the protein against which the antiserum is directed is induced by heat shock. Indirect immunofluorescence shows that the antigen is primarily localized at or near the nucleolus in cultured cells and numerous murine tissues. Treatment of cultured cells with deoxyribonuclease destroys the organization of staining within the nucleus while ribonuclease appears to completely release the antigen from the nucleus. A binding of the antiserum to cytoplasmic structures is also observed by immunofluorescence. This association with nucleoli may have implications in the regulatory aspects of the heat-shock response.A hyperthermic challenge to a cell can result in a reorganization at translational and transcriptional levels (7, 23) and at the same time protect the cell from additional applications of the same stress (8), probably through the intervention of heatshock proteins (14,15,17,18,27,28). Despite the implications of this, it is important to recognize that the function of heat-shock proteins remains a mystery. However, reports indicate that at least some heat-shock proteins my localize in the nucleus (2,3,13,16,31,32), suggesting a direct role in the regulatory changes associated with this response.To learn more regarding the function of heat-shock proteins and their role in regulation and protection, we investigated mammalian heat-shock proteins using an immunologic approach. We report here on the characterization of an antiserum against the major l l0,000-dalton mammalian heatshock protein (HSP 110). ~ It is demonstrated by indirect immunofluorescence that this protein is localized at or near the nucleolus and is released from the nucleus by treatment with ribonuclease. This suggests that aspects of nucleolar function may be important in the protective and regulatory properties of the heat-shock response. mented with 15% heat-inactivated newborn calf serum. In heat-shock experiments: flasks were immersed horizontally into a constant temperature water bath (Haake FK-2) for the indicated times at 45"C + 0.1°C. 10TY2 mouse embryo fibroblasts were originally obtained from Dr. John Bertram of this Institute. These cells are grown in Eagles basal medium with Earle's salts (Gibco Laboratories) supplemented with 10% heat-inactivated fetal calf serum. Frozen sections were obtained from tissues of BALB/c CR mice supplied by the West Seneca Laboratories of this Institute. MATERIALS AND METHODS Cells Preparation of Antigen and Immunoautoradiography:Heat-shock proteins were identified by autoradiography of two-dimensional O'Farrel gels, as previously modified and described (10,19), by applying a [35S]methionine pulse during the peak induction peri...

Abstract. The sequence of heat shock-induced perturbations in protein synthesis and cytoskeletal organization was investigated in primary cultures of mouse mammary epithelial cells (MMEC). Exposure of the cells to 45°C for 15 min caused a marked inhibition of protein synthesis through 2 h after heat. Resumption of protein synthesis began by 4 h, was complete by 8 h, and was accompanied by induction of four major heat shock proteins (HSPs) of 68, 70, 89, and 110 kD. Fluorescent cytochemistry studies indicated that heat shock elicited a reversible change in the organization of keratin filaments (KFs) and actin filaments but had a negligible effect on microtubules. Changes in the organization of KFs progressed gradually with maximal retraction and collapse into the perinuclear zone occurring at 1-2 h after heat followed by restoration to the fully extended state at 8 h. In contrast, actin illaments disappeared immediately after heat treatment and then rapidly returned within 30-60 min to their original appearance. The translocation of many organelles first into and then away from the juxtanuclear area along with the disruption and reformation of polyribosomes were concurrent with the sequential changes in distribution of KFs. The recovery of the arrangement of KFs coincided with but was independent of the resumption of protein synthesis and induction of HSPs. Thermotolerance could be induced in protein synthesis and KFs, but not in actin filaments, by a conditioning heat treatment. Neither protein synthesis nor induction of HSPs was necessary for the acquisition of thermotolerance in the KFs. The results are compatible with the possibility that protein synthesis may depend on the integrity of the KF network in MMEC. Heat shock thus can efficiently disarrange the KF system in a large population of epithelial cells, thereby facilitating studies on the functions of this cytoskeletal component.T HE effects of temperature elevation on cellular physiology have been studied in widely divergent organisms from bacteria to man (58). The dramatic changes in gene programming characterized by the induction of a specific set of proteins, usually referred to as heat shock proteins (HSPs),t together with inhibition in the synthesis of most other cellular proteins have been recognized as the main features of the heat shock response (43,51,61). This response is thought, at the simplest level, to be homeostatic to protect the cell against the environmental insult and provide it with the capacity to survive the crisis and preserve normal cellular activities. However, the molecular mechanisms responsible for these modifications remain obscure.Along with the rapid and transient reprogramming of transcription and translation, alterations in cellular morphology