Proteins related to the mouse L-cell major heat shock protein are synthesized in the absence of heat shock gene expression

Characterization of the porcine seminal plasma proteome comparing ejaculate portions

Full identification of boar seminal plasma (SP) proteins remains challenging. This study aims to provide an extensive proteomic analysis of boar SP and to generate an accessible database of boar SP-proteome. A SP-pool (33entire ejaculates/11 boars; 3ejaculates/boar) was analyzed to characterize the boar SP-proteome. Twenty ejaculates (5 boars, 4ejaculates/boar) collected in portions (P1: first 10mL of sperm rich ejaculate fraction (SRF), P2: rest of SRF and P3: post-SRF) were analyzed to evaluate differentially expressed SP-proteins among portions. SP-samples were analyzed using a combination of SEC, 1-D SDS PAGE and NanoLC-ESI-MS/MS followed by functional bioinformatics. The identified proteins were quantified from normalized LFQ intensity data. A total of 536 SP-proteins were identified, 409 of them in Sus scrofa taxonomy (374 validated with ≥99% confidence). Barely 20 of the identified SP-proteins were specifically implicated in reproductive processes, albeit other SP-proteins could be indirectly involved in functionality and fertility of boar spermatozoa. Thirty-four proteins (16 identified in S. scrofa taxonomy) were differentially expressed among ejaculate portions, 16 being over-expressed and 18 under-expressed in P1-P2 regarding to P3. This major proteome mapping of the boar SP provides a complex inventory of proteins with potential roles as sperm function- and fertility- biomarkers.

BIOLOGICAL SIGNIFICANCE

This proteomic study provides the major characterization of the boar SP-proteome with >250 proteins first reported. The boar SP-proteome is described so that a spectral library can be built for relative 'label free' protein quantification with SWATH approach. This proteomic profiling allows the creation of a publicly accessible database of the boar SP-proteome, as a first step for further understanding the role of SP-proteins in reproductive outcomes as well as for the identification of biomarkers for sperm quality and fertility.

Age-related increases of macroautophagy and chaperone-mediated autophagy in rat nucleus pulposus

OBJECTIVE

Excessive apoptosis plays an important role in the progression of intervertebral disc degeneration. However, the effect of autophagy, another type of programmed cell death, on the pathogenesis of disc degeneration is still unclear. Macroautophagy and chaperone-mediated autophagy (CMA) change and intervertebral disc degeneration aggravates with age. This study aims at examining the expression changes of light chain 3 (LC3), lysosome-associated membrane protein 2A (LAMP-2A), and Hsc70, the indicator substrates of macroautophagy and CMA, in rat nucleus pulposus (NP) to prove that macroautophagy and CMA are both related with age.

METHODS

Female Sprague-Dawley rats of 3, 12, and 24 months (n = 8 per age) were used in this study. Autophagic vacuoles in NP cells were detected by transmission electron microscopy. In NP, the expressions of LC3-II and LAMP-2A protein and mRNA were examined by immunohistochemistry and reverse transcription polymerase chain reaction, respectively. LC3-II, LC3-I, and LAMP-2A protein were also measured by western blot. The mRNA and protein level of myocyte enhancer factor-2D regulated by LAMP-2A and Hsc70 were detected by reverse transcriptase polymerase chain reaction and western blot, respectively.

RESULTS

Transmission electron microscopy showed more autophagic vacuoles in 12- and 24-month groups than in 3-month group. Expression of LC3-II and LC3-II/LC3-I in 24-month group was significantly higher than in 3-month group (p < 0.05). Meanwhile, LAMP-2A expression was significantly higher in 24-month group than in 3-month group (p < 0.05). However, lower expression of Hsc70 and myocyte enhancer factor-2D was found in the 24-month rats than in 3-month group (p < 0.05, p < 0.05, respectively).

CONCLUSION

Macroautophagy and CMA were present and increased with age in rat NP.

Age-related decrease in the inducibility of heat-shock protein 70 in human peripheral blood mononuclear cells

We have investigated the effect of age and of the presence of proinflammatory cytokines on Hsp 70 production in human peripheral blood mononuclear cells, using flow cytometry. Twenty-seven women and 23 men, all apparently healthy, participated in the study. At 37 degrees C, the percentage of Hsp 70-producing monocytes and lymphocytes, as well as the level of Hsp 70 in monocytes, were negatively influenced by age. After exposure of the cells to 42 degrees C, the increase of Hsp 70 production was more pronounced in monocytes than in lymphocytes; both the intensity of Hsp 70 production and the percentage of Hsp 70-producing cells were negatively influenced by the age of the subjects, as well for monocytes as for lymphocytes. There was a negative correlation between the intensity of Hsp 70 production by monocytes exposed to 42 degrees C and the serum levels of tumor necrosis factor-alpha and interleukin-6. In conclusion, in human monocytes and lymphocytes, heat-induced Hsp 70 production is reduced with increasing age and is negatively influenced in monocytes by proinflammatory cytokines.

The Hsp70 homolog gene, Hsc70t, is expressed under translational control during mouse spermiogenesis

Hsc70t is a member of the Hsp70 family of genes and is constitutively expressed after meiosis in mouse spermatogenesis. Immunohistochemistry and in situ hybridization techniques were used to examine the precise localization of the Hsc70t product during the various stages of spermatogenesis. A rabbit antiserum raised againstthe mouse Hsc70t-lacZ fusion protein detected the Hsc70t protein in the late spermatid-enriched fraction after two-dimensional Western blot analyses. On histological sections, the protein appears in the cytoplasm of spermatids as they progress from step 9 to the final step of spermatogenesis. An antisense RNA probe generated from the 3' untranslated region of Hsc70t cDNA detected Hsc70t mRNA in late round spermatids from step 7 onward with the signal disappearing in spermatids at step 15. Thus, Hsc70t mRNA first appears after meiosis in haploid cells but is not translated effectively until these cells progress to the transcriptionally inactive stage which coincides with chromatin condensation. These results establish that the synthesis of Hsc70t protein is under strict translational control.

The role of tumor rejection antigens in host antitumor defense mechanisms

BACKGROUND

Normal cells undergo contact inhibition of growth when their surface molecules interact. Tumor cells, however, have undergone a mutation that prevents this arrest of growth upon contact inhibition and allows constant growth. Thus, growth inhibition fails to occur despite the interaction of surface molecules. In recent years a subgroup of these surface molecules has been of interest to cancer investigators. This subgroup has been termed the tumor rejection antigens (TRAs). As the name implies, these are specific to the tumor of origin and may direct the immune system of the host to target the tumor cells and kill them.

METHODS

A literature search was carried out on TRAs to ascertain the current thinking on the subject.

RESULTS

Initial studies of TRAs have revealed that some of them may be heat shock proteins (HSPs). In particular, grp96, a number of the HSP90 family, has been implicated. More recent studies, however, have shown that HSPs alone may not be immunogenic but may act as carrier proteins for tumor specific peptides.

CONCLUSION

Such findings have led to speculation that HSPs or their associated peptides may have a role in the diagnosis and/or treatment of specific cancers. Immunotherapy and bispecific antibodies in particular are areas in which HSPs may prove to be useful.

Chemical modifications of a recombinant bovine stress-inducible 70 kDa heat-shock protein (Hsp70) mimics Hsp70 isoforms from tissues

A cDNA clone for the stress-inducible 70 kDa heat-shock protein (Hsp70) has been isolated from a bovine skeletal-muscle cDNA library. This mRNA encodes a protein with a calculated molecular mass of 70250 Da. The cDNA has one continuous open reading frame capable of encoding a 641-amino-acid protein. Expression of this cDNA in a bacterial expression system produced a protein with a mobility identical with that of the inducible Hsp70 protein from bovine skeletal muscle as determined by SDS/PAGE. Two-dimensional gel electrophoresis demonstrated this protein to have focusing properties identical with that of a minor isoform from bovine skeletal muscle. Upon carbamylation of this bacterially expressed protein, a train of charged proteins with charge differences of -1 were produced. These carbamylated proteins were shown to have similar focusing mobilities to the Hsp70 isoforms isolated from bovine skeletal muscle. These results demonstrate the identification of a skeletal-muscle inducible Hsp70 gene and suggest that the presence of multiple Hsp70 isoforms may be the product of post-translational modifications to the Hsp70 proteins.

Emerging role of heat shock proteins in biology and medicine

All cells, procaryotic and eucaryotic, respond to an elevation in temperature by increasing the synthesis of a family of proteins collectively known as heat shock proteins (HSPs). HSPs are among the most highly conserved and abundant proteins in nature. Studies on the regulation of the synthesis of HSPs have for several years shed light on the mechanisms regulating gene expression. The results from recent years, showing that HSPs play crucial roles in a wide variety of normal cellular processes, has made them an object of even broader interest, first to molecular and cellular biologists and later to specialists in various fields of medicine including oncology, immunology, infectious disease, autoimmunity, embryology, neurology and endocrinology. The aim of this review is to briefly summarize our present knowledge of the regulation of the heat shock response and the structure of the relevant gene products, HSPs. Moreover, some of the exciting associations between HSPs and various fields of medicine will be discussed.

Expression of heat shock protein 70 and heat shock cognate 70 messenger RNAs in rat cortex and cerebellum after heat shock or amphetamine treatment

The expression of strictly inducible hsp70 mRNAs and constitutively expressed hsc70 mRNAs was compared in cerebellum and cerebral cortex of control rats, heat-shocked rats, and rats made hyperthermic with amphetamine. An hsc70-specific oligonucleotide probe identified a 2.55-kb mRNA in cerebellum and cerebral cortex of all rats. An hsp70-specific oligonucleotide probe identified a 3.05-kb mRNA and a 3.53-kb mRNA in cerebellum and cerebral cortex of heat-shocked and amphetamine-treated rats, but not in control rats. Quantitation demonstrated that both hsp70 and hsc70 mRNA levels, relative to 18S rRNA levels, were increased following each treatment. The relative levels of both mRNAs were higher in cerebellum than in cerebral cortex. In amphetamine-treated rats, hsc70 mRNA relative levels increased at body temperatures greater than 39 degrees C, whereas hsp70 mRNA synthesis was induced at temperatures greater than 40 degrees C. Total thermal response values and relative levels of both mRNAs were compared. The results suggested that both the transcription and turnover of hsp70 mRNAs differed between cerebellum and cerebral cortex. At equivalent total thermal response values, amphetamine-treated rats had higher relative levels of hsp70 mRNAs than heat-shocked rats, suggesting that amphetamine enhanced the induction of hsp70 mRNAs.

Heat stress increases delivery of a unique sub-population of proteins conveyed by fast axonal transport

The effect of heat stress on protein synthesis and fast axonal transport was examined in vitro in bullfrog dorsal root ganglion (DRG) and associated spinal/sciatic nerve. Qualitative and quantitative changes of individual 35S-methionine-labelled proteins were determined following DRG labelling and fast transport in respective nerves via two-dimensional gel electrophoresis/autoradiography. Elevation of temperature from 18 degrees C to 33 degrees C for up to 6 hr resulted in a marked increase in synthesis of five individual DRG species of approximately 74,000 daltons that comigrate with heat shock proteins (HSPs). A quantitative comparison of species within this subset revealed two subgroups differentially affected by stress. The three most basic proteins were induced to approximately 1300% of unstressed controls after 6 hr of stress, while the two most acidic species demonstrated an increase to only 300% of controls over the same period. The relative abundance of 25 additional DRG proteins were uneffected by heat stress. Of 70 35S-labelled fast-transported proteins similarly analyzed, 15, comprising 5 families, were consistently transported at greater than 150% of controls following up to 6 hr of heat stress. Over this period all 15 proteins shared a similar profile of abundance relative to non-induced proteins. Transport was elevated to the greatest extent after 2 hr of stress, declined after 3 hr, and tended to rebound at later times. The remaining 55 fast-transported protein spots analyzed were unaffected. An increased delivery of this unique sub-population of 15 fast-transported proteins suggests a possible involvement in early cellular events that mediate heat stress in the nervous system.

A role for a 70-kilodalton heat shock protein in lysosomal degradation of intracellular proteins

A 73-kilodalton (kD) intracellular protein was found to bind to peptide regions that target intracellular proteins for lysosomal degradation in response to serum withdrawal. This protein cross-reacted with a monoclonal antibody raised to a member of the 70-kD heat shock protein (hsp70) family, and sequences of two internal peptides of the 73-kD protein confirm that it is a member of this family. In response to serum withdrawal, the intracellular concentration of the 73-kD protein increased severalfold. In the presence of adenosine 5'-triphosphate (ATP) and MgCl2, the 73-kD protein enhanced protein degradation in two different cell-free assays for lysosomal proteolysis.

HSP70-related proteins in bovine skeletal muscle

Constitutive expression of HSP70-related proteins was detected in a variety of bovine tissues using a specific antibody. All tissues contained a 73 kilodalton protein. A lower molecular weight form (72 kilodaltons) that co-migrated on two-dimensional gels with the stressed-induced HSP70 was present in high levels in bovine skeletal muscle, but absent from rat skeletal muscle. Two-dimensional gel analysis revealed several isoforms for both the 73 and 72 kilodalton forms. Purification of HSP70-related proteins from bovine skeletal muscle, thymus gland and rat skeletal muscle demonstrated that the antibody recognized all the forms present in the tissue homogenates. The two proteins are similar but distinct as detected by one-dimensional peptide mapping. The lower molecular form was not present in fetal tissue but was detectable in newborn animals, suggesting that the levels are regulated during development.

Heat shock protects WEHI-164 target cells from the cytolysis by tumor necrosis factors alpha and beta

Elevated temperatures and a number of other types of stress induce synthesis of a small number of highly conserved proteins, the heat shock proteins, in a wide variety of cells. The structure and regulation of these proteins have been intensively studied but the question of the function of this universal response has remained unanswered. We studied the effect of heat shock on tumor necrosis factor-alpha (TNF-alpha)- and -beta (TNF-beta)-mediated cytolysis of WEHI-164 clone 13 target cells. One hour pretreatment of target cells at 42 degrees C decreased rTNF-alpha-mediated lysis by 65.3%, 50.5% and 44.8% and TNF-beta-mediated lysis by 61.9%, 43.2% and 38.9% at cytokine concentrations of 0.5 ng/ml, 5 ng/ml and 50 ng/ml, respectively, in an 18-h Cr-release assay. The effect was maximal when TNF-alpha was added 1 h after the heat shock and then gradually declined, being almost undetectable after 2 days. This pattern was found to roughly coincide with the kinetics of hsp68, the major heat-induced protein in murine cells. Heat shock treatment had no protective effect when given 1 h after addition of recombinant TNF-alpha. The heat-induced target cell resistance was not associated with decreased binding of recombinant TNF-alpha to its receptor. Inhibition of protein synthesis by cycloheximide diminished this effect by 76% and inhibition of transcription by actinomycin D abolished it completely, suggesting that de novo synthesized heat-induced proteins protect target cells from TNF-mediated lysis in heat shock-treated WEHI cells.

Expression of different members of heat shock protein 70 gene family in liver and hepatomas

The levels of expression of some genes of the HSP 70 family have been assessed in rat liver and in a series of transplantable hepatomas with different growth rates, subjected to heat shock in vivo. For this purpose, the mRNAs for the constitutive cognate HSC 73, the heat-inducible HSP 70 and the glucose-regulated GRP 78 have been analyzed by: (i) translation in reticulocyte lysates; (ii) hybrid-selected translation, and (iii) Northern blot analysis. In comparison with the liver, the fast-growing 3924A hepatoma has an increased constitutive amount of HSC 73 mRNA and a lower induction of HSP 70 mRNA after heat shock. The behavior of the 9618A slow-growing hepatoma is more similar to that of the liver, indicating that the changes detected in the fast-growing hepatoma are correlated to the high growth rate of the tumor rather than to carcinogenesis. This conclusion is reinforced by the results obtained with Yoshida AH-130 cells, growing at two different rates imposed by the environment in which they develop. When the Yoshida hepatoma grows rapidly in the peritoneal cavity, constitutive expression of HSC 73 mRNA is high and the inducibility of HSP 70 mRNA is poor: the opposite occurs when the tumor grows slowly in the subcutaneous compartment. The amount of GRP 78 mRNA increases progressively from the liver to the fast-growing hepatoma. The level of HSC 73 mRNA seems to correlate with the methylation state of the corresponding gene.

Expression of heat shock proteins by isolated mouse spermatogenic cells

Proteins of the hsp70 family are abundant in mouse spermatogenic cells. These cells also synthesize relatively large amounts of a 70,000-molecular-weight protein (P70) that appears to be a cell-specific isoform of hsp70, the major heat-inducible protein (R.L. Allen, D.A. O'Brien, and E.M. Eddy, Mol. Cell. Biol. 8:828-832, 1988). In this study, proteins of unstressed and heat-stressed spermatogenic cells consisting of purified preparations of preleptotene, leptotene-zygotene, pachytene spermatocytes, and round spermatids were analyzed by two-dimensional polyacrylamide gel electrophoresis. Unstressed preleptotene and leptotene-zygotene spermatocytes contained little P70, whereas relatively large amounts of P70 were present in pachytene spermatocytes and round spermatids. Labeling studies showed that P70 was synthesized primarily in pachytene spermatocytes and that little synthesis occurred in round spermatids or in preleptotene and leptotene-zygotene stages of spermatogenesis. Synthesis of hsp70 was not detectable in unstressed cells but was induced in all stages of isolated germ cells following heat stress. These results indicate that P70 is expressed in a stage-specific manner during cell differentiation, whereas hsp70 is synthesized in response to stress in all populations of isolated spermatogenic cells examined.

The induction of phenylpropanoid biosynthetic enzymes by ultraviolet light or fungal elicitor in cultured parsley cells is overriden by a heat-shock treatment

The normal (25° C) response of parsley (Petroselinum crispum Mill.) cell suspension cultures to ultraviolet (UV) light was suppressed by a simultaneous 37° C heat-shock treatment, as indicated by the loss of the inducibility of two enzymes of flavonoid biosynthesis, phenylalanine ammonia-lyase (EC 4.3.1.5) and chalcone synthase. The effects on enzyme activity and on enzyme synthesis in vitro and in vivo were similar, indicating that regulatory control is at an early step of gene expression, presumably transcription. When heat shock was given during the course of an ongoing UV induction, both enzyme synthesis and enzyme activities ceased rapidly. Likewise, the induction of phenylalanine ammonia-lyase by an elicitor from Phytophthora megasperma f. sp. glycinea was terminated upon transfer from 25° C to 37° C. Based on these and previously published data, it is concluded that stress responses in this system are preferentially expressed in the order of heat shock, fungal elicitor and UV light.

Identification and sequence analysis of a new member of the mouse HSP70 gene family and characterization of its unique cellular and developmental pattern of expression in the male germ line

A unique member of the mouse HSP70 gene family has been isolated and characterized with respect to its DNA sequence organization and expression. The gene contains extensive similarity to a heat shock-inducible HSP70 gene within the coding region but diverges in both 3' and 5' nontranslated regions. The gene does not yield transcripts in response to heat shock in mouse L cells. Rather, the gene appears to be activated uniquely in the male germ line. Analysis of RNA from different developmental stages and from enriched populations of spermatogenic cells revealed that this gene is expressed during the prophase stage of meiosis. A transcript different in size from the major heat-inducible mouse transcripts is most abundant in meiotic prophase spermatocytes and decreases in abundance in postmeiotic stages of spermatogenesis. This pattern of expression is distinct from that observed for another member of this gene family, which was previously shown to be expressed abundantly in postmeiotic germ cells. These observations suggest that specific HSP70 gene family members play distinct roles in the differentiation of the germ cell lineage in mammals.

Expression of heat shock proteins by isolated mouse spermatogenic cells

Proteins of the hsp70 family are abundant in mouse spermatogenic cells. These cells also synthesize relatively large amounts of a 70,000-molecular-weight protein (P70) that appears to be a cell-specific isoform of hsp70, the major heat-inducible protein (R.L. Allen, D.A. O'Brien, and E.M. Eddy, Mol. Cell. Biol. 8:828-832, 1988). In this study, proteins of unstressed and heat-stressed spermatogenic cells consisting of purified preparations of preleptotene, leptotene-zygotene, pachytene spermatocytes, and round spermatids were analyzed by two-dimensional polyacrylamide gel electrophoresis. Unstressed preleptotene and leptotene-zygotene spermatocytes contained little P70, whereas relatively large amounts of P70 were present in pachytene spermatocytes and round spermatids. Labeling studies showed that P70 was synthesized primarily in pachytene spermatocytes and that little synthesis occurred in round spermatids or in preleptotene and leptotene-zygotene stages of spermatogenesis. Synthesis of hsp70 was not detectable in unstressed cells but was induced in all stages of isolated germ cells following heat stress. These results indicate that P70 is expressed in a stage-specific manner during cell differentiation, whereas hsp70 is synthesized in response to stress in all populations of isolated spermatogenic cells examined.

Identification and sequence analysis of a new member of the mouse HSP70 gene family and characterization of its unique cellular and developmental pattern of expression in the male germ line

A unique member of the mouse HSP70 gene family has been isolated and characterized with respect to its DNA sequence organization and expression. The gene contains extensive similarity to a heat shock-inducible HSP70 gene within the coding region but diverges in both 3' and 5' nontranslated regions. The gene does not yield transcripts in response to heat shock in mouse L cells. Rather, the gene appears to be activated uniquely in the male germ line. Analysis of RNA from different developmental stages and from enriched populations of spermatogenic cells revealed that this gene is expressed during the prophase stage of meiosis. A transcript different in size from the major heat-inducible mouse transcripts is most abundant in meiotic prophase spermatocytes and decreases in abundance in postmeiotic stages of spermatogenesis. This pattern of expression is distinct from that observed for another member of this gene family, which was previously shown to be expressed abundantly in postmeiotic germ cells. These observations suggest that specific HSP70 gene family members play distinct roles in the differentiation of the germ cell lineage in mammals.

A novel hsp70-like protein (P70) is present in mouse spermatogenic cells

Mouse spermatogenic cells contain relatively large amounts of a 70-kilodalton protein (P70) that is closely related to hsp70, the major inducible heat shock protein. When hsp70 from spermatogenic cells is heat induced, it migrates to the same location as does P70 on two-dimensional polyacrylamide gels, indicating that it has an apparently identical mass and isoelectric point. P70 reacts strongly and specifically with an anti-Drosophila hsp70 monoclonal antibody that is specific for products of the hsp70 gene family. Both P70 and hsp70 are also ATP-binding proteins and are purified by using ATP-affinity chromatography. However, P70 and hsp70 are unique proteins on the basis of peptide map analysis and are regulated differently in germ cells. P70 appears to be a novel heat shock protein of spermatogenic cells which is synthesized in association with germ cell differentiation.

A normal mitochondrial protein is selectively synthesized and accumulated during heat shock in Tetrahymena thermophila

We have identified and purified a 58-kilodalton protein of Tetrahymena thermophila whose synthesis during heat shock parallels that of the major heat shock proteins. This protein, hsp58, was found in both non-heat-shocked as well as heat-shocked cells; however, its concentration in the cell increased approximately two- to threefold during heat shock. The majority of hsp58 in both non-heat-shocked and heat-shocked cells was found by both cell fractionation studies and immunocytochemical techniques to be mitochondrially associated. During heat shock, the additional hsp58 was found to selectively accumulate in mitochondria. Nondenatured hsp58 released from mitochondria of non-heat-shocked or heat-shocked cells sedimented in sucrose gradients as a 20S to 25S complex. We suggest that this protein may play a role in mitochondria analogous to the role the major heat shock proteins play in the nucleus and cytosol.

Mitogen activation induces the enhanced synthesis of two heat-shock proteins in human lymphocytes

We have used mitogenic lectin (PHA) and a monoclonal antibody (OKT3) to stimulate human peripheral blood (G0) lymphocytes, in the presence of monocytes, and have found two major preferentially synthesized proteins, 73 and 95 kD, which are induced by the mitogens. The elevated synthesis of both proteins begins approximately 4-6 h after mitogen addition (early to mid G0/G1) before entry into first S phase. Maximum synthesis of both proteins is reached by 12 h after mitogen addition when P95 synthesis represents approximately 4%, and P73 approximately 2%, of the total protein synthesis, compared with less than 0.5% for each protein in cells cultured without mitogen. Thus, the proteins appear to be major components of activated cells. We find that both P73 and P95 are induced by heat stress as well as mitogenic stimulation. The induction of the proteins is not affected by either deleting glucose from the culture media or, alternatively, by supplementing it. Using polyclonal antibodies prepared to each of the proteins isolated from mitogen activated cells and monoclonal antibodies that were raised to heat shock proteins, we are able to show that P95 is electrophoretically and immunologically identical to the HSP 90 induced by heat stress. P73 is one of the 70 kD HSPs, (termed HSC 70; Pelham, H. R. B. 1986. Cell. 46: 959-961), but is different from the most strongly heat inducible form of HSP 70 (72 kD). The distribution of both proteins in subcellular fractions of mitogen activated lymphocytes is similar to the reported localization of the respective HSP's in other cell types. The results suggest that HSP 90 and HSC 70 may have functional roles in stress response and growth processes of human lymphocytes.

A second antigenic heat shock protein of Plasmodium falciparum

We describe here an antigen of Plasmodium falciparum, defined by a cDNA clone designated Ag361. The antigen is a soluble cytoplasmic 70-kD polypeptide present in all isolates analyzed and in all stages of asexual development in the blood. The antigen is a natural immunogen, although it lacks repeating epitopes of many P. falciparum antigens. Ag361 shares extensive sequence homology with the hsp70 proteins of Xenopus laevis, Drosophila melanogaster, Escherichia coli, and man, as well as a previously isolated P. falciparum hsp70 protein. The genome of P. falciparum contains at least five hsp70-like genes, located on at lest four different chromosomes.

Complex regulation of heat shock- and glucose-responsive genes in human cells

We have isolated a human genomic clone that encodes the glucose-responsive protein GRP78 and have used this cloned gene probe, together with a cloned HSP70 gene, to study the expression of both stress-induced genes in response to inhibitors of cellular metabolism. On the basis of the effects of this group of chemicals on GRP78 and HSP70 expression, we have identified three classes of stress gene inducers. The first class induces GRP78 expression and includes inhibitors of glycoprotein processing. The second class results in coordinate activation of both GRP78 and HSP70 synthesis and includes amino acid analogs and heavy metals. Chemicals in the third class coordinately induce GRP78 and repress HSP70 expression; this class includes the calcium ionophore A23187 and the glucose analog 2-deoxyglucose. Whereas induction of GRP78 or HSP70 expression is primarily due to transcriptional activation, chemicals that repress HSP70 expression act through posttranscriptional regulation. These results reveal that the regulation of GRP78 and HSP70 expression is complex and may be dependent on the specificity and magnitude of physiological damage.

A novel hsp70-like protein (P70) is present in mouse spermatogenic cells

Mouse spermatogenic cells contain relatively large amounts of a 70-kilodalton protein (P70) that is closely related to hsp70, the major inducible heat shock protein. When hsp70 from spermatogenic cells is heat induced, it migrates to the same location as does P70 on two-dimensional polyacrylamide gels, indicating that it has an apparently identical mass and isoelectric point. P70 reacts strongly and specifically with an anti-Drosophila hsp70 monoclonal antibody that is specific for products of the hsp70 gene family. Both P70 and hsp70 are also ATP-binding proteins and are purified by using ATP-affinity chromatography. However, P70 and hsp70 are unique proteins on the basis of peptide map analysis and are regulated differently in germ cells. P70 appears to be a novel heat shock protein of spermatogenic cells which is synthesized in association with germ cell differentiation.

Complex regulation of heat shock- and glucose-responsive genes in human cells

We have isolated a human genomic clone that encodes the glucose-responsive protein GRP78 and have used this cloned gene probe, together with a cloned HSP70 gene, to study the expression of both stress-induced genes in response to inhibitors of cellular metabolism. On the basis of the effects of this group of chemicals on GRP78 and HSP70 expression, we have identified three classes of stress gene inducers. The first class induces GRP78 expression and includes inhibitors of glycoprotein processing. The second class results in coordinate activation of both GRP78 and HSP70 synthesis and includes amino acid analogs and heavy metals. Chemicals in the third class coordinately induce GRP78 and repress HSP70 expression; this class includes the calcium ionophore A23187 and the glucose analog 2-deoxyglucose. Whereas induction of GRP78 or HSP70 expression is primarily due to transcriptional activation, chemicals that repress HSP70 expression act through posttranscriptional regulation. These results reveal that the regulation of GRP78 and HSP70 expression is complex and may be dependent on the specificity and magnitude of physiological damage.

A normal mitochondrial protein is selectively synthesized and accumulated during heat shock in Tetrahymena thermophila

We have identified and purified a 58-kilodalton protein of Tetrahymena thermophila whose synthesis during heat shock parallels that of the major heat shock proteins. This protein, hsp58, was found in both non-heat-shocked as well as heat-shocked cells; however, its concentration in the cell increased approximately two- to threefold during heat shock. The majority of hsp58 in both non-heat-shocked and heat-shocked cells was found by both cell fractionation studies and immunocytochemical techniques to be mitochondrially associated. During heat shock, the additional hsp58 was found to selectively accumulate in mitochondria. Nondenatured hsp58 released from mitochondria of non-heat-shocked or heat-shocked cells sedimented in sucrose gradients as a 20S to 25S complex. We suggest that this protein may play a role in mitochondria analogous to the role the major heat shock proteins play in the nucleus and cytosol.

Structure and expression of a human gene coding for a 71 kd heat shock 'cognate' protein

In all eukaryotes examined so far, hsp70 gene families include cognate genes (hsc70) encoding proteins of about 70 Kd which are expressed constitutively during normal growth and development. We have investigated the structural relationship of heat-inducible and cognate members of the human hsp70 gene family. Among several human genomic clones isolated using Drosophila hsp/hsc70 probes, one contained an hsc70 gene. Its complete sequence is reported here. It is split by eight introns and encodes a predicted protein of 70899 d that would be 81% homologous to hsp70. Structural comparisons with corresponding genes from other species provide one of the most striking examples of gene conservation. Isolation of a corresponding cDNA clone, RNA-mapping and in vitro translation data demonstrate that the gene is expressed constitutively and directs the synthesis of a 71 kd protein. The latter is very likely to be identical to a clathrin uncoating ATPase recently identified as a member of the hsp70-like protein family.

Heat-shock proteins and mRNAs in liver and hepatoma

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A hsp70-related gene is constitutively highly expressed in testis of rat and mouse

The expression pattern of major heat shock related genes (hsp70 gene family) in various organs of mouse and rat was investigated using Northern blot analysis. Heat shock gene related transcripts were detected in total RNA by hybridization with cloned mouse hsp70 gene sequences. Cells of various organs of intact mouse and rat constitutively synthesize a 2.2 kb and a 2.5 kb RNA. Exceptionally high levels of the 2.5 kb RNA, 50-250 fold higher than in other tissues are found in testis of both rodents. The 2.5 kb RNA hybridizes strongly to an extended region of mouse hsp70 gene; it also hybridizes poorly to the Drosophila hsp70 gene. The data suggest that the 2.5 kb RNA is transcribed from a hsp70-related gene in mouse and rat.

Effects of cycloheximide on thermotolerance expression, heat shock protein synthesis, and heat shock protein mRNA accumulation in rat fibroblasts

A single hyperthermic exposure can render cells transiently resistant to subsequent high temperature stresses. Treatment of rat embryonic fibroblasts with cycloheximide for 6 h after a 20-min interval at 45 degrees C inhibits protein synthesis, including heat shock protein (hsp) synthesis, and results in an accumulation of hsp 70 mRNA, but has no effect on subsequent survival responses to 45 degrees C hyperthermia. hsp 70 mRNA levels decreased within 1 h after removal of cycloheximide but then appeared to stabilize during the next 2 h (3 h after drug removal and 9 h after heat shock). hsp 70 mRNA accumulation could be further increased by a second heat shock at 45 degrees C for 20 min 6 h after the first hyperthermic exposure in cycloheximide-treated cells. Both normal protein and hsp synthesis appeared increased during the 6-h interval after hyperthermia in cultures which received two exposures to 45 degrees C for 20 min compared with those which received only one treatment. No increased hsp synthesis was observed in cultures treated with cycloheximide, even though hsp 70 mRNA levels appeared elevated. These data indicate that, although heat shock induces the accumulation of hsp 70 mRNA in both normal and thermotolerant cells, neither general protein synthesis nor hsp synthesis is required during the interval between two hyperthermic stresses for Rat-1 cells to express either thermotolerance (survival resistance) or resistance to heat shock-induced inhibition of protein synthesis.

Expression and localization of Drosophila melanogaster hsp70 cognate proteins

Monoclonal antibodies have been used to identify three proteins in Drosophila melanogaster that share antigenic determinants with the major heat shock proteins hsp70 and hsp68. While two of the proteins are major proteins at all developmental stages, one heat shock cognate protein, hsc70, is especially enriched in embryos. hsc70 is shown to be the product of a previously identified gene, Hsc4. We have examined the levels of hsp70-related proteins in adult flies and larvae during heat shock and recovery. At maximal induction in vivo, hsp70 and hsp68 never reach the basal levels of the major heat shock cognate proteins. Monoclonal antibodies to hsc70 have been used to localize it to a meshwork of cytoplasmic fibers that are heavily concentrated around the nucleus.

The brain 68-kilodalton microtubule-associated protein is a cognate form of the 70-kilodalton mammalian heat-shock protein and is present as a specific isoform in synaptosomal membranes

The relationship between the 68-kilodalton microtubule-associated protein (68KMAP) and the major heat-induced protein (HSP70) in rat and human cells was investigated by comparison of their heat induction properties and by tryptic and Cleveland peptide mapping procedures. HSP70 synthesis was induced by heat shock of rat and human cells, whereas 68KMAP was a major synthesised protein in the absence of heat shock, with its synthesis being only slightly increased on heat shock. Tryptic peptide mapping, however, indicated strong peptide homology between the two proteins. These data, therefore, confirm that 68KMAP represents a constitutively expressed, heat-shock cognate gene. Two-dimensional gel electrophoretic analysis of subcellular fractions of rat brain, combined with peptide mapping procedures, indicated that 68KMAP exists as at least two isoforms separable by isofocussing, the more acidic of which (alpha 68KMAP) is present in fractions enriched in microtubules, cytosol, microsomes, synaptosomal plasma membranes, and synaptic vesicles, and the more basic of which (beta 68KMAP) is present predominantly in fractions enriched in synaptic vesicles and synaptosomal plasma membranes. These two forms are distinguishable in terms of changes in Cleveland peptide maps, and we conclude that alpha- and beta 68KMAP, therefore, represent distinct forms. The significance of these findings to the molecular pathogenesis of Down's syndrome in the human brain is discussed.

Mutations in cognate genes of Saccharomyces cerevisiae hsp70 result in reduced growth rates at low temperatures

Expression of two Saccharomyces cerevisiae genes (YG101 and YG103) that are related to the gene encoding inducible 70K protein (hsp70) is repressed upon heat shock. Mutations of the two genes were constructed in vitro and substituted into the yeast genome in place of the wild-type alleles. No phenotypic effect of single mutations of either gene was detected. However, cells containing both YG101 and YG103 mutations showed altered growth properties; double-mutation cells possess an optimal growth temperature of 37 degrees C rather than 30 degrees C and grow increasingly poorly as the temperature is lowered. Mutations of two other members of this hsp70-related multigene family, YG100 and YG102, have been analyzed (E. A. Craig and K. Jacobsen, Cell 38:841-849, 1984). Cells containing both YG100 and YG102 mutations cannot form colonies at 37 degrees C. Fusions between the YG101 and YG102 promoter regions and the YG100 and YG101 structural genes, respectively, were constructed. The YG101 promoter-YG100 structural gene fusion was not able to restore normal growth properties to the yg101- yg103- mutant. Also, yg100- yg102- cells containing the YG102 promoter-YG101 structural gene fusion were unable to grow at 37 degrees C. Failure of the protein products of related genes to rescue the relative cold sensitivity of growth suggests that members of the hsp70 multigene family are functionally distinct.

The 73 kilodalton heat shock cognate protein purified from rat brain contains nonesterified palmitic and stearic acids

A protein related to the 71 kilodalton inducible rat heat shock protein was purified to electrophoretic homogeneity in milligram amounts from brain tissue of nonheat-stressed rats. The protein has been designated as a stress cognate protein based on previous studies and data presented herein that this protein cross-reacted with a monoclonal antibody originally raised against the Drosophila 70 kilodalton heat shock protein. The purified protein had an apparent molecular mass of 73 kilodaltons when analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and an apparent mass of 150 kilodaltons as determined by nondissociative gel chromatography, suggesting that the purified protein is a homodimer. The purified protein had isoelectric points of 5.0 under nondissociative conditions and 5.6 when exposed to protein denaturants, suggesting loss of bound anionic molecules and/or net exposure of basic residues upon denaturation. Chloroform/methanol extraction of the purified protein and subsequent analyses by thin layer and gas-liquid chromatography resulted in the identification of palmitic and stearic acids noncovalently bound to the protein. Approximately four molecules of fatty acids were bound per dimer with palmitic and stearic acids present in a one-to-one ratio. The purified protein did not bind exogenously added radioactive palmitate, indicating that the fatty acid-binding sites of the cognate protein were fully occupied and that the associated fatty acids were too tightly bound to exchange readily. The possible significance of the fatty acids associated with the 73 kilodalton stress cognate protein is discussed.

A mouse tumor-specific transplantation antigen is a heat shock-related protein

A tumor-specific transplantation antigen has been purified to homogeneity from the cytosol of a methylcholanthrene-induced tumor, Meth A. The purified antigen is highly immunogenic and specific against challenge with Meth A, providing greater than 95% inhibition of tumor growth in immunized syngeneic mice. Immunofluorescence analysis of Meth A showed that the antigen is a highly abundant cytosolic protein but that it is also present at the cell surface and, therefore, accessible to the host's immune system. The antigen consists of two polypeptide isoforms present in equimolar amounts, having similar masses (84 and 86 kDa), pI values (4.95 and 4.90), and amino acid compositions. Both are phosphoproteins, and neither is glycosylated. The NH2-terminal sequences of the two isoforms are identical except that each chain contains a portion of unique sequence. Comparison of the NH2-terminal and CNBr-fragment sequence data to the sequences of the yeast and Drosophila heat shock proteins (Hsp90 and Hsp83, respectively) reveals that 73 of 91 residues compared are identical. In addition, an anti-Meth A tumor antigen serum that defects the isoforms from a variety of tumors also immunoprecipitates proteins of identical mass and pI from both normal and heat-shocked mouse embryo cells.

Expression and localization of Drosophila melanogaster hsp70 cognate proteins

Monoclonal antibodies have been used to identify three proteins in Drosophila melanogaster that share antigenic determinants with the major heat shock proteins hsp70 and hsp68. While two of the proteins are major proteins at all developmental stages, one heat shock cognate protein, hsc70, is especially enriched in embryos. hsc70 is shown to be the product of a previously identified gene, Hsc4. We have examined the levels of hsp70-related proteins in adult flies and larvae during heat shock and recovery. At maximal induction in vivo, hsp70 and hsp68 never reach the basal levels of the major heat shock cognate proteins. Monoclonal antibodies to hsc70 have been used to localize it to a meshwork of cytoplasmic fibers that are heavily concentrated around the nucleus.

Effects of cycloheximide on thermotolerance expression, heat shock protein synthesis, and heat shock protein mRNA accumulation in rat fibroblasts

A single hyperthermic exposure can render cells transiently resistant to subsequent high temperature stresses. Treatment of rat embryonic fibroblasts with cycloheximide for 6 h after a 20-min interval at 45 degrees C inhibits protein synthesis, including heat shock protein (hsp) synthesis, and results in an accumulation of hsp 70 mRNA, but has no effect on subsequent survival responses to 45 degrees C hyperthermia. hsp 70 mRNA levels decreased within 1 h after removal of cycloheximide but then appeared to stabilize during the next 2 h (3 h after drug removal and 9 h after heat shock). hsp 70 mRNA accumulation could be further increased by a second heat shock at 45 degrees C for 20 min 6 h after the first hyperthermic exposure in cycloheximide-treated cells. Both normal protein and hsp synthesis appeared increased during the 6-h interval after hyperthermia in cultures which received two exposures to 45 degrees C for 20 min compared with those which received only one treatment. No increased hsp synthesis was observed in cultures treated with cycloheximide, even though hsp 70 mRNA levels appeared elevated. These data indicate that, although heat shock induces the accumulation of hsp 70 mRNA in both normal and thermotolerant cells, neither general protein synthesis nor hsp synthesis is required during the interval between two hyperthermic stresses for Rat-1 cells to express either thermotolerance (survival resistance) or resistance to heat shock-induced inhibition of protein synthesis.

Specific interaction between the p53 cellular tumour antigen and major heat shock proteins

The protein p53 is capable of participating in neoplastic transformation and can form specific complexes with the large-T antigen of simian virus 40 (SV40). This interaction probably results in the stabilization of p53 (refs 7,8) and may contribute to SV40-mediated transformation. Several non-SV40-transformed cells also exhibit a stabilized p53 which is present in elevated levels. Recently, this stabilization was shown to coincide with the ability to precipitate a polypeptide (p68) of relative molecular mass (Mr) 68,000-70,000 by anti-p53 monoclonal antibodies. We now report that this co-precipitation indeed represents a specific complex between the two proteins; the complex sediments on a sucrose gradient as a relatively broad peak of 10-14S and can be dissociated in vitro. Furthermore, p68 is the HSP70 heat shock protein cognate, found in elevated levels in a p53-overproducing cell line. On heat-shock treatment of such overproducers, p53 also forms a complex with the related highly inducible HSP68.

Heat shock response of the rat lens

The sequence relationship between the small heat shock proteins and the eye lens protein alpha-crystallin (Ingolia, T. D., and E. E. Craig, 1982, Proc. Natl. Acad. Sci. USA, 79: 2360-2364) prompted us to subject rat lenses in organ culture to heat shock and other forms of stress. The effects on protein synthesis were followed by labeling with [35S]methionine and analysis by one- and two-dimensional gel electrophoresis and fluorography. Heat shock gave a pronounced induction of a protein that could be characterized as the stress protein SP71. This protein probably corresponds to the major mammalian heat shock protein hsp70. Also two minor proteins of 16 and 85 kD were induced, while the synthesis of a constitutive heat shock-related protein, P73, was considerably increased. The synthesis of SP71 started between 30 and 60 min after heat shock, reached its highest level after 3 h, and had stopped again after 8 h. In rat lenses that were preconditioned by an initial mild heat shock, a subsequent shock did not cause renewed synthesis of SP71. This effect resembles the thermotolerance phenomenon observed in cultured cells. The proline analogue azetidine-2-carboxylic acid, zinc chloride, ethanol, and calcium chloride did not, under the conditions used, induce stress proteins in the rat lens. Sodium arsenite, however, had very much the same effects as heat shock. Calcium ionophore A23187 specifically and effectively induced the synthesis of the glucose-regulated protein GRP78. No special response to stress on crystallin synthesis was noticed.

Expression of the major heat shock protein (hsp 70) family during early mouse embryo development

Stress or heat shock proteins (hsp) are synthesized by most cells in response to adverse environmental conditions. In mammalian cells, the major proteins synthesized in response to stress have relative molecular weights (Mr) in the range of 68 to 74 kilodaltons (kD) and are encoded by a small multi-gene family collectively referred to as hsp 70 genes. In unfertilized mouse eggs, no members of the hsp 70 family appear to be synthesized under normal or stressful (heat shock) conditions. At the two-cell stage, two proteins with Mr = 74 kD and Mr = 70 kD are expressed as a consequence of developmentally activated transcription of these hsp 70 genes. No stress-induced synthesis in response to heat shock is observed at this stage. At the eight-cell stage, constitutive synthesis of the 70-kD protein continues, but, as in the two-cell embryo, no heat shock induced synthesis of a novel heat shock protein is observed. By the blastocyst stage, however, an inducible protein with Mr = 68 kD is synthesized in response to heat shock in addition to constitutive synthesis of the 70-kD protein. The constitutively synthesized cognate proteins are coded for by a set of mRNAs about 2,000 nucleotides in length. The induced hsp 68 proteins are coded for by mRNAs of larger size (about 2,600 nucleotides). Only the smaller mRNA class is detectable on Northern blots of RNA extracted from control or heat shock cleavage stage embryos and control blastocysts. As predicted from protein synthetic studies, both classes are resolved in RNA preparations derived from heat-shocked blastocysts.

Mutations in cognate genes of Saccharomyces cerevisiae hsp70 result in reduced growth rates at low temperatures

Expression of two Saccharomyces cerevisiae genes (YG101 and YG103) that are related to the gene encoding inducible 70K protein (hsp70) is repressed upon heat shock. Mutations of the two genes were constructed in vitro and substituted into the yeast genome in place of the wild-type alleles. No phenotypic effect of single mutations of either gene was detected. However, cells containing both YG101 and YG103 mutations showed altered growth properties; double-mutation cells possess an optimal growth temperature of 37 degrees C rather than 30 degrees C and grow increasingly poorly as the temperature is lowered. Mutations of two other members of this hsp70-related multigene family, YG100 and YG102, have been analyzed (E. A. Craig and K. Jacobsen, Cell 38:841-849, 1984). Cells containing both YG100 and YG102 mutations cannot form colonies at 37 degrees C. Fusions between the YG101 and YG102 promoter regions and the YG100 and YG101 structural genes, respectively, were constructed. The YG101 promoter-YG100 structural gene fusion was not able to restore normal growth properties to the yg101- yg103- mutant. Also, yg100- yg102- cells containing the YG102 promoter-YG101 structural gene fusion were unable to grow at 37 degrees C. Failure of the protein products of related genes to rescue the relative cold sensitivity of growth suggests that members of the hsp70 multigene family are functionally distinct.