Acquisition of thermotolerance during development of Blastocladiella emersonii

In the fungus Blastocladiella emersonii the synthesis of heat-shock proteins is developmentally regulated; particular subsets of heat-shock proteins are induced by heat shock during sporulation, germination and growth and some heat shock-related proteins are spontaneously expressed during sporulation (Bonato et al., 1987, Eur. J. Biochem., in press). Nevertheless, acquisition of thermotolerance can be induced at any stage of the life cycle. The development of thermotolerance is correlated with the enhanced synthesis of some heat-shock proteins: hsp 82a, hsp 82b, hsp 76, hsp 70, hsp 60, hsp 25, hsp 17b. Other hsps are not specifically involved in thermotolerance.     

Characterization of the functional properties of the 70-kDa protein of Mycobacterium bovis.

A number of mycobacterial proteins have been shown to induce strong humoral and cellular immune responses, including the 70-kDa antigen (p70) of Mycobacterium leprae and Mycobacterium bovis. On the basis of sequence homology and an ATP binding ability, p70 has previously been tentatively allocated to the 70-kDa family of heat shock proteins (hsp70). We have purified the M. bovis p70 antigen and described ATPase and Ca(2+)-dependent autophosphorylating activities. These co-purified with p70 on gel chromatography and were up-regulated by native proteins and down-regulated by peptides. Inhibitory peptides were shown to bind p70. These data imply close functional similarities of mycobacterial p70 to other members of the hsp70 family, the Escherichia coli homologue dnaK in particular.     

The heat shock response in hydra: immunological relationship of hsp60, the major heat shock protein of Hydra vulgaris,to the ubiquitous hsp70 family

The major heat shock protein (hsp) of Hydra vulgaris has recently been found to be a 60 kDa protein. Since in all organisms studied so far, the major heat shock protein is a 70 kDa protein, we have analyzed the relationship of hydra hsp60 to the highly conserved 70 kDa heat shock protein family. Genes and proteins related to the 70 kDa class of stress proteins are present in hydra. However, antibodies known to cross-react with hsp70 proteins in several different organisms do not cross-react with hydra hsp60 suggesting that hsp60 is not related to the conserved hsp70 proteins.     

Human humoral immunity to hsp70 during Trypanosoma cruzi infection

Immunologic screening of cDNA expression libraries has been widely used for the identification of DNA sequences encoding the immunologically relevant proteins of many pathogenic microorganisms. For reasons that are not entirely clear, sequences encoding 70-kDa heat shock and related proteins (hsp70), which are among the most highly conserved proteins known, have routinely been identified by this approach. Consequently, hsp70 proteins have been proposed to be involved in the autoimmune processes thought responsible for the pathogenesis of the diseases caused by some of these organisms, e.g., chronic Trypanosoma cruzi infection (Chagas' disease). Therefore, we investigated whether hsp70 might be a specific target of the human humoral immune response to T. cruzi infection, and, if so, whether humoral autoimmunity to hsp70 might play a role in pathogenesis. We found that hsp70 is indeed a major polypeptide Ag in Chagas' disease, but that the antibodies to T. cruzi hsp70 do not react with human hsp70--even though the proteins display 73% amino acid sequence identify. These results indicate that self-tolerance to hsp70 is maintained during chronic T. cruzi infection and strongly argue against a role for humoral autoimmunity to hsp70 in the pathogenesis of Chagas' disease.     

Protein and peptide binding and stimulation of in vitro lysosomal proteolysis by the 73-kDa heat shock cognate protein.

Lysosomal degradation of intracellular proteins during serum withdrawal is stimulated by a member of the 70-kDa heat shock protein (hsp70) family (Chiang, H.-L., Terlecky, S. R., Plant, C. P., and Dice, J. F. (1989) Science 246, 382-385). This hsp70, isolated by affinity chromatography with RNase S-peptide-Sepharose, is referred to as the 73-kDa peptide recognition protein (prp73). We now report that prp73 binds to several proteins and peptides whose degradative rates are increased during serum withdrawal. prp73 also binds to the pentapeptide, KFERQ, and more weakly to most modified RNase S-peptide derivatives with a single amino acid substitution within the KFERQ sequence. Taken together, these results suggest that prp73 binds to a variety of proteins at peptide regions biochemically related to KFERQ. Three lines of evidence indicate that prp73 is the heat shock cognate protein of 73 kDa (hsc73): (a) among five hsp70s tested, hsc73 binds to RNase S-peptide most avidly, (b) both prp73 and hsc73 also bind to RNase A and aspartate aminotransferase but not to ovalbumin, lysozyme, or ubiquitin, and (c) both prp73 and hsc73 promote uptake and degradation of [3H] RNase S-peptide by lysosomes in vitro, while three other hsp70s are without activity in this assay.     

Hsp56: a novel heat shock protein associated with untransformed steroid receptor complexes

The recently-described p59 protein has been shown to be associated with untransformed steroid receptors present in rabbit uterus and rat liver cytosols (Tai, P. K., Maeda, Y., Nakao, K., Wakim, N. G., Duhring, J. L., and Faber, L. E. (1986) Biochemistry 25, 5269-5275; Renoir, J.-M., Radanyi, C., Faber, L. E., and Baulieu, E.-E. (1990) J. Biol. Chem. 265, 10740-10745), while a smaller version of this protein (p56) interacts with glucocorticoid receptors in human IM-9 cell cytosols (Sanchez, E. R., Faber, L. E., Henzel, W. J., and Pratt, W. B. (1990) Biochemistry 29, 5145-5152). In addition to interacting with glucocorticoid receptors, the p56 protein of IM-9 cell cytosol is also found as part of a large heteromeric complex that contains both the 70-kDa and 90-kDa heat shock proteins (hsp70 and hsp90, respectively). Given this association of p56 with the two major stress proteins, I have speculated that p56 may itself be a heat shock protein. In this paper, the effect of heat stress on the rate of synthesis of p56 is determined. Intact IM-9 cells were exposed to 37 or 43 degrees C for 4 h, followed by pulse-labeling with [35S]methionine. Analysis of whole cytosolic extracts by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography reveal an increased rate of radiolabeling for hsp70, hsp90, hsp100, ad hsp110, but no heat-inducible protein of smaller relative molecular mass is detected. However, immune-purification of p56 from normal and heat-stressed cytosols with the EC1 monoclonal antibody results in the presence of a 56-kDa protein that exhibits an increased rate of synthesis in response to heat stress. The results of two-dimensional gel Western blots employing the EC1 antibody demonstrate that this heat-inducible protein is indeed the EC1-reactive p56 protein and that the induction effect is not due to unequal yields of p56 during immune-purification. Heat stress has no effect on the composition of the p56.hsp.70.hsp90 complex, except that the complex derived from heat shocked-cells contains both the constitutive and heat-inducible forms of hsp70. Induction of p56 also occurs in IM-9 cells subjected to chemical stress (sodium arsenite). It is proposed that p56 is a steroid receptor-associated heat shock protein which can now be termed hsp56. Like hsp90, hsp56 likely serves in some vital cellular role apart from any specific function it provides in steroid receptor action.     

Interactions of the heme-regulated eIF-2 alpha kinase with heat shock proteins in rabbit reticulocyte lysates.

Inhibition of protein synthesis in rabbit reticulocyte lysates occurs in response to a variety of conditions including heme deficiency, addition of oxidants, and heat stress. The inhibition of translation is due to the activation of a heme-regulated protein kinase (HRI) which specifically phosphorylates the alpha-subunit of the eukaryotic initiation factor eIF-2. In this report, immunoadsorption with monoclonal antibodies (mAbs) and Western blot analysis were used to investigate the interaction of HRI, the 90-kDa heat shock protein (hsp 90), hsp 70, and the EC1 antigen in rabbit reticulocyte lysates under protein synthesizing conditions. The data indicate that hsp 90, hsp 70, and the EC1 antigen interact with HRI in rabbit reticulocyte lysate. The EC1 antigen is a protein that has been demonstrated to be associated with several steroid hormone receptor-hsp 90 complexes and reacts with the KN 382/EC1 mAb (EC1). The association of HRI with hsp 90 and the EC1 antigen in the reticulocyte lysate was found to be dependent on the presence of hemin at a concentration of 5 microM or higher; little HRI was coadsorbed by the 8D3 anti-hsp 90 mAb or the EC1 mAb in the absence of hemin. Hsp 70 remains associated with HRI in the absence of hemin, suggesting that hsp 90 and 70 may bind to HRI at different sites. The immunological properties of the hsp 70 associated with HRI indicate that it may be the constitutively express heat shock cognate protein (hsc 73). The results suggest that the association of HRI with hsp 90 and the EC1 antigen may be in a dynamic equilibrium, in which complex formation is either facilitated or stabilized by the presence of hemin, and supports the notion that these proteins in conjunction with hsp 70 may play a role in regulating HRI activity or activation in situ.     

T lymphocyte stress response. II. Protection of translation and DNA replication against some forms of stress by prior hyperthermic stress

We have compared the effects of a mild heat shock and febrile temperatures on heat-shock protein (hsp) synthesis and development of stress tolerance in T lymphocytes. Our previous studies demonstrated that febrile temperatures (less than or equal to 41 degrees C) induced the synthesis of hsp110, hsp90, and the constitutive or cognate form of hsp70 (hscp70; a weak induction of the strongly stress-induced hsp70 was also observed. In the studies reported herein, we demonstrate that a mild heat shock (42.5 degrees C) reverses this ratio; that is, hsp70 and not hscp70 is the predominate member of this family synthesized at this temperature. Modest heat shock also enhanced the synthesis of hsp110 and hsp90. In order to assess the relationship between hsp synthesis and the acquisition of thermotolerance, purified T cells were first incubated at 42.5 degrees C (induction temperature) and then subsequently subjected to a severe heat-shock challenge (45 degrees C, 30 min). T cells first incubated at a mild heat-shock temperature were capable of total protein synthesis at a more rapid rate following a severe heat shock than control cells (induction temperature 37 degrees C). This phenomenon, which has been previously termed translational tolerance, did not develop in cells incubated at the febrile temperature (induction temperature 41 degrees C). Protection of translation also extended to immunologically relevant proteins such as interleukin-2 and the interleukin-2 receptor. Because clonal expansion is a critical event during an immune response, the effects of hyperthermic stress on DNA replication (mitogen-induced T cell proliferation) was also evaluated in thermotolerant T cells. DNA synthesis in control cells (induction temperature 37 degrees C) was severely inhibited following heat-shock challenge at 44 degrees C or 45 degrees C; in contrast, T cells preincubated at 42.5 degrees C rapidly recovered their DNA synthetic capacity. T cells preincubated at a febrile temperature were moderately protected against hyperthermic stress. The acquisition of thermotolerance was also associated with enhanced resistance to chemical (ethanol)-induced stress but not to heavy metal toxicity (cadmium) or dexamethasone-induced immunosuppression. These studies suggest that prior hsp synthesis may protect immune function against some forms of stress (e.g., febrile episode) but would be ineffective against others such as elevated glucocorticoid levels which normally occur during an immune response.     

Members of the Drosophila HSP 70 family share ATP-binding properties

In Drosophila, the hsp 70 family consists of a group of proteins of similar molecular masses (hsps 68, 70 and 72) that exist as multiple isoforms. In this report, it is shown that hsps 68, 70 and 72 from Drosophila cells can be purified by affinity chromatography on ATP-agarose. Furthermore it is demonstrated that the multiple members of the hsp 70 family, which accumulate in large amounts in the nucleus during a heat shock, can be specifically solubilized from the isolated nuclei fraction by ATP. One of the major cognate proteins (hsc 70) also shows similar behavior. These data suggest that most, if not all, of the related Drosophila hsps 70 possess, like their mammalian counterparts, an ATP-binding site which could be related to their function in the stress response.     

Examination of the expression of the heat shock protein gene, hsp110, in Xenopus laevis cultured cells and embryos

Eukaryotic organisms respond to various stresses with the synthesis of heat shock proteins (HSPs). HSP110 is a large molecular mass HSP that is part of the HSP70/DnaK superfamily. In this study, we have examined, for the first time, the expression of the hsp110 gene in Xenopus laevis cultured cells and embryos. Sequence analysis revealed that the protein encoded by the hsp110 cDNA exhibited 74% identity with its counterparts in mammals and only 27-29% with members of the Xenopus HSP70 family. Hsp110 mRNA and/or protein was detected constitutively in A6 kidney epithelial cells and was inducible by heat shock, sodium arsenite, and cadmium chloride. However, treatment with ethanol or copper sulfate had no detectable effect on hsp110 mRNA levels. Similar results were obtained for hsp70 mRNA except that it was inducible with ethanol. In Xenopus embryos, hsp110 mRNA was present constitutively during development. Heat shock-inducible accumulation of hsp110 mRNA occurred only after the midblastula stage. Whole mount in situ hybridization analysis revealed that hsp110 mRNA accumulation in control and heat shocked embryos was enriched in selected tissues. These studies demonstrate that Xenopus hsp110 gene expression is constitutive and stress inducible in cultured cells and developmentally- and tissue specifically-regulated during early embryogenesis.     

Nucleosomal organization of a BPV minichromosome containing a human H4 histone gene

Summary When the body temperature of rats is elevated to 42°C, four heat shock proteins, with the molecular weights of 70000, 71000, 85000, and 100000 (hsp 70, hsp 71, hsp 85, and hsp 100, respectively), are induced in various tissues of rats (Fujio et al., J Biochem 101, 181–187, 1987). Heat shock proteins are induced by various stresses other than heat in varieties of cultured cells, so we studied whether heat shock proteins are induced in intact rats by different treatments. Analysis of the translation products of poly(A) + RNA isolated from the livers of rats recovering from ischemia of the liver showed that mRNAs for hsp 70, hsp 71, and hsp 85 were induced. These hsp-mRNAs were also induced in the livers of rats 6 h after a partial hepatectomy, and had returned to control levels 24 h after the surgery. These results suggested that heat shock proteins have not only the function of protection against various stresses but also physiological functions in the normal growth and development of animals.