Transformation of glucocorticoid-receptor complex from rat thymocytes and its accumulation in chromatin in a cell-free system.

The accumulation of glucocorticoid-receptor complex from rat thymocyte cytosol in a thymocyte chromatin preparation has been studied. A thymocyte 100 000 X g supernatant was prepared and the receptor and the receptor stabilized by the addition of glycerol until 40%. Tritiated glucocorticoid-receptor complex was formed by incubation of this solution with tritiated glucocorticoids at -5 degree C. The chromatin accumulated part of the complex at incubations at 4 degrees C. Receptor without hormone was not accumulated in the chromatin. The accumulation from cytosol diluted and preincubated at 4 degrees C prior to the addition of the chromatin occurred with a high rate, whereas a low rate was seen without preincubation. This indicated a transformation of the complex during the preincubation. This transformation was found to be obligatory for the accumulation and to be promoted by dilution of the supernatant and by high ionic strength. The transformed and the untransformed complexes differed with respect to partition coefficients in an aqueous dextran-polyethylene glycol two-phase system and in their behaviour during adsorptions with dextran-coated charcoal, where great loss of transformed complex was observed. The accumulation of complex in the chromatin was found to be unsaturable in the concentration interval studied (0.07--0.25 nM).     

Conversions of the glucocorticoid · receptor complex of rat thymocyte cytosol, studied by partition in an aqueous dextra-polyethylene glycol two-phase system

Tritiated glucocorticoid · receptor complex was formed by incubation of [³H] triamcinalone acetonide at –5°C with thymocyte cytosol, made 40% with respect to glycerol. The cytosol was then incubated at various temperatures, ionic strengths and cytosol concentrations for various times. At the end of the incubations, the partition coefficient of the complex in an aqueous dextranpolyethylene glycol two-phase system was determined. By the criterion of time-dependent changes of the partition coefficient, two differential conversions of the complex were distinguished: 1. A rapid, ionic strength-dependent process, increasing the partition coefficient. 2. A slower, temperature-, ionic strenght- and cytosol concentration-dependent process, increasing the partition coefficient.The effect of the salt composition of the partition mixture on the partition coefficient indicated, that the complex has a pI below 6. The effect of pH of the partition mixture indicated that the conformation of the state of aggregation of the complex is dependent on pH.     

An analysis of the binding of the chick oviduct progesterone-receptor to chromatin

The binding of progesterone-receptor complexes to chromatin from target and nontarget tissues was studied in vitro. Chromatin from both target and non-target tissues responds in a similar manner to saly and cofactors and has the same K_D (approx. 3·10⁻⁹ M) for the progesterone-receptor complex. The only observed difference in the binding of the progesterone-receptor complex to target and nontarget chromatins is the difference in total number of acceptor sites. Oviduct chromatin has approx. 1300 sites/pg DNA, spleen chromatin has approx. 840 sites/pg DNA, and erythrocyte chromatin has about 330 sites/pg DNA. The K_D and number of acceptor sites for progesterone-receptor complex binding to oviduct chromatin remains the same even after extensive purification of the progesterone-receptor complex. Activation of cytosol labeled with [³H]progesterone by preincubation at 25°C, analogous to that required for maximal nuclear binding, occurs if the binding studies to chromatin are performed in 0.025 M salt. The absence of an observable temperature effect when the studies are performed at 0.15 M salt is due to the activation of the receptor by salt. The dissociation of the progesterone-receptor complex from chromatin exhibits a single dissociation rate and the initial event is the appearance of free progesterone rather than a progesterone-receptor complex. Lastly, the treatment of chromatin with an antibody prepared against either single-stranded DNA or double-stranded DNA does not alter the extent of binding of the progesterone-receptor complex. Similarly, pretreatment of chromatin with a single-stranded nuclease does not inhibit the capacity of chromatin to bind the hormone-receptor complex.     

The role of sulfhydryl groups in permitting transformation and DNA binding of the glucocorticoid receptor

Treatment of rat liver cytosol containing temperature-transformed, [3H]dexamethasone-bound receptors at 0 degree C with the sulfhydryl-modifying reagent methyl methanethiosulfonate (MMTS) inhibits the DNA-binding activity of the receptor, and DNA-binding activity is restored after addition of dithiothreitol (DTT). When cytosol containing untransformed receptors is heated at 25 degrees C in the presence of MMTS, the 90-kDa heat shock protein dissociates from the receptor in the same manner as in the absence of MMTS, and the receptor will bind to DNA-cellulose if DTT is added subsequently at 0 degree C. These observations are consistent with the conclusion of Bodwell et al. (Bodwell, J. E., Holbrook. N. J. and Munck, A. (1984) Biochemistry 23, 1392-1398) that sulfhydryl moieties on the receptor are absolutely required for the receptor to bind to DNA, and they show that the sulfhydryl-modifying reagent does not inhibit the temperature-mediated dissociation of the heteromeric receptor complex that accompanies transformation to the DNA-binding state. When steroid-receptor complexes that are prebound to DNA-cellulose are exposed to MMTS, the steroid rapidly dissociates, but the receptor remains bound to DNA. Thus, the presence of steroid is not required for the receptor to remain bound to DNA in a high affinity manner. Treatment of cytosol containing transformed glucocorticoid-receptor complexes at 0 degrees C with 20 mM hydrogen peroxide also inactivates the DNA-binding activity of the receptor. The peroxide-induced inactivation is reversed by DTT. Incubation of rat liver cytosol containing untransformed glucocorticoid-receptor complexes at 25 degrees C with hydrogen peroxide prevents their transformation to the DNA-binding form as shown by their inability to bind to DNA-cellulose after addition of DTT. The presence of peroxide during heating of the cytosol also prevents dissociation of the receptor complex as assayed both by reduction in sedimentation value of the receptor and by dissociation of the 90-kDa heat shock protein from the steroid-binding protein. These results strongly suggest that critical sulfur moieties in the receptor complex must be in a reduced form for the temperature-mediated dissociation of the receptor to occur.     

Cryotolerance and Cold Adaptation in Lactococcus lactis Subsp. lactis IL1403

The physiology of the cold-shock response in Lactococcus lactis subsp. lactis IL1403 at a subzero temperature, and cold-induced adaptation to heat shock, were investigated. Preincubation of cells at 8°C led to the development of cryotolerance, i.e., an enhanced capacity to survive exposure to freezing temperature (-20°C). Pretreatment with chemicals considered to be chaotropic agents did not induce cryotolerance or, in contrast, led to a decrease in survival capacity at -20°C. Interestingly, preincubation at 8°C led also to thermololerance to a 52°C challenge, but preincubation of cells at 42°C for 30 min did not improve their capacity to survive freezing-thawing exposure. These results demonstrate that cold- and heat-shock responses are physiologically linked by a complex relation. Furthermore, food processing at low temperature before subzero or heat treatment may need to be reconsidered.     

Effect of dextran-charcoal treatment on the dissociation kinetics of glucocorticoid-receptor complexes: possible involvement of lipid

Dissociation kinetics were determined at 0 degrees C for molybdate-stabilized glucocorticoid-receptor complexes in rat thymus cytosol. Exposure of complexes to dextran-coated charcoal had no effect on their chromatographic properties or transformation status, but dissociation rates measured after charcoal treatment were significantly lower than those determined by displacement with excess competing steroid. The dissociation rate of the [2,4,6,7-3H]prednisolone-receptor complex was similarly modified by chromatography on Lipidex 1000, but not by chromatography on Sephadex G-25 or G-75. It is concluded that treatment of glucocorticoid-receptor complexes with dextran-charcoal or Lipidex 1000 brings about a change in dissociation rate as a consequence of the removal of a lipid component from the complex.     

Characterization of the progesterone receptor of rabbit uterus with the synthetic progestin 16α-ethyl-21-hydroxy-19-norpregn-4-ene-3,20-dione

The synthetic progestin 16α-ethyl-21-hydroxy-19-norpregn-4-ene-3,20-dione (Org 2058) was used to characterize the progesterone receptor in the uterine cytosol of the rabbit. [³H] Org 2058 binds to a homogeneous population of protin binding sites with an apparent association equilibrium constant of 7.7· 10⁸ M⁻¹ at 0°C. The concentration of protein-bound steroid at saturation is 2.3 pmol per mg of cytosol protein. [³H] Progesterone binds to the same set of binding sites but exhibits a 4–5 fold lower apparent association constant. The difference in affinity is mainly due to a 13-fold slower rate of dissociation of the synthetic progestin compared with progesterone. Org 2058 competes very efficiently for the binding of [³H] progesterone to the uterine cytosol, and progesterone also competes, although less efficiently, for the binding of [³H]-Org 2058. There is a good correlation between the progestational activity of various steroids and their ability to compete with [³H] Org 2058 binding to the cytosol. At 0°C, there is no metabolic transformation of either Org 2058 or progesterone in the uterine cytosol.When filled with the steroid, the progesterone receptor is stable, but in the absence of the steroid the receptor binding sites are thermolabile and show a rapid decay at 20°C . Org 2058 is more effective than progesterone in protecting the receptor against thermal inactivation. The rate constant of association and dissociation of [³H] Org 2058 and the cytosol receptor are strongly dependent on temperature and the activation energy of the dissociation reaction is 17.8 kcal/mol. The equilibrium association constant is less dependent on temperature and exhibits ΔH° of −4.7 kcal/mol. The binding reaction shows a positive entropy change of 23 cal · K⁻¹ · mol⁻¹.At low ionic strength the complex of Org 2058 and the progesterone receptor tends ot aggregate. It sediments as a broad peak on sucrose gradients (4–6 S), and is excluded from columns of Sephadex G-100 and G-200. At concentrations of NaCl above 0.15 M, the receptor sediments in sucrose gradients as an homogeneous peak at 3.6 S, but upon gel filtration it aggregates and a complex elution pattern is observed, that prevents a precise estimation of the molecular weight.     

Stabilization of glucocorticoid-receptor complexes in rat thymus cytosol by a factor from WEHI-7 cells

Using a variety of physico-chemical techniques we have recently characterized three distinct forms of glucocorticoid-receptor complexes present in the cytosol from rat thymus cells incubated with glucocorticoid; the relative proportions of these complexes are dependent on the conditions to which the cells or cytosols are exposed. Two of these complexes correspond to the well established nonactivated and activated receptor forms, while the third has properties consistent with mero-receptor. Based on their differential affinities for DNA- and DEAE-cellulose we have developed a rapid mini-column chromatographic procedure for separating these three forms and have used it to examine the stability of complexes in cytosol preparations. We have found that activated glucocorticoid-receptor complexes from rat thymus cells are relatively unstable under cell-free conditions in that they undergo time-dependent losses in DNA binding and are converted to mero-receptor. In contrast, cytosolic glucocorticoid-receptor complexes prepared from WEHI-7 mouse thymoma cells are remarkably stable under similar conditions. Mixing experiments with equal portions of rat thymus and WEHI-7 cytosol revealed that the difference between the two tissues cannot be accounted for merely by differences in amounts of proteolytic enzymes, since addition of rat thymus cytosol to WEHI-7 cytosol containing activated glucocorticoid-receptor complexes does not result in their conversion to mero-receptor. However, the WEHI-7 cytosol affords considerable protection to activated glucocorticoid-receptor complexes in thymus cytosol. The stabilizing factor from WEHI-7 cytosol is heat stable (survives 100 degrees C for 30 min), insensitive to pH over a wide range (4.0-10.0), and appears to be macromolecular. It does not inhibit activation, and thus appears distinct from the previously described endogenous glucocorticoid receptor stabilizing factor responsible for stabilization of thymocyte receptor binding capacity (Leach et al., J. Biol. Chem. 257: 381-388, 1982). We propose that the factor is an endogenous inhibitor of the protease(s) responsible for mero-receptor formation.     

Transformation of glucocorticoid-receptor complex oligomers to DNA-binding forms in the absence of monomerization

The contention that transformation of steroid-receptor complexes is represented by dissociation of receptor oligomers was tested by comparing sedimentation and DNA binding properties of glucocorticoid-receptor complexes from HeLa cell cytosol under several conditions. Transformation of glucocorticoid-receptor complexes could be induced by heat, and/or salt treatment of cytosolic extracts, but not by dilution. Heat-induced transformation of receptor complexes was also confirmed by DEAE-cellulose chromatography. Analysis of cytosolic extracts showed that sedimentation and DNA binding properties of glucocorticoid-receptor complexes did not correlate. Both oligomeric and monomeric receptor complexes, in fact, were found to be either transformed, or untransformed, depending on the treatments cytosolic extracts underwent, before being subjected to analysis. We then concluded that release of glucocorticoid receptor monomers cannot account for their transformation to a DNA-binding form in vitro, and suggested that exposure of positive charges on the surface of receptors in the course of transformation occurs in some region of the glucocorticoid receptor which is not involved in interactions between the proteinaceous components of oligomers.     

Interactions of concanavalin A with chick embryo fibroblasts transformed by rous sarcoma virus Study with an RSV mutant thermosensitive for transformation

The interactions between concanvalin A and chick embryo fibroblasts, normal and infected with Rous sarcoma virus (RSV-BH) or its thermosensitive mutant RSV-BH-Ta, have been studied. Normal chick embryo cells and RSV-BH transformed cells showed at 4 and 25 °C a similar number of concanavalin A receptors per cell. Analysis of the binding data by the Scatchard relation showed that apparent changes in binding as a function of temperature are due to the thermodynamic properties of the process and and not to endocytosis. The lectin receptors on the cell surface of normal and RSV-BH infected cells showed homogeneity in their binding properties. Chick cells infected with RSV-BH-Ta showed a lectin binding behavior that was dependent on the temperature at which the cells were grown. At the permissive temperature for transformation (37 °C), the binding process was similar to that observed for normal and RSV-BH infected cells. At the nonpermissive temperature (41 °C), the cells showed at least two sets of concanavalin A receptors. The new set of receptors on the cell surface had a lower lectin affinity than those observed in the same cells at 37 °C.Chick cells infected with RSV-BH showed an enhanced agglutinability by concanavalin A, as compared with normal cells. Cells infected with RSV-BH-Ta showed a reversal of the correlation between increased concanavalin A agglutinability and the transformed state. At the permissive temperature for transformation, the cells were not agglutinable, whereas at the nonpermissive temperature they presented agglutinability indexes as high as those observed with RSV-BH infected cells. This enhanced agglutinability observed with cells maintained at the nonpermissive temperature for transformation may be related to the new set of low affinity receptors present at 41 °C.     

The activated hepatic glucocorticoid-receptor complex: A simple one-step method for its separation from nonactivated complex

Protamine sulfate was found to precipitate completely the nonactivated [³H]-dexamethasone-receptor complex of rat liver. This observation was then used as the basis of a method to separate activated from nonactivated complex. Thus, addition of 10 mg/ml of protamine sulfate to the rat hepatic cytosol [³H]dexamethasone-receptor complex, incubated at 0–4°C for 2 hr, resulted in the complete precipitation of [³H]dexamethasone-receptor complex. The remaining supernatant obtained on centrifugation at 800g was unable to bind either to nuclei or to DNA-cellulose. An increase in temperature to 25°C or the addition of 10 mm CaCl₂ to the cytosol resulted in the appearance of activated [³H]dexamethasone-receptor complex in the supernatant obtained by addition of protamine sulfate. This was determined by characteristic binding to nuclei or DNA cellulose and by pI. Protamine sulfate could not affect the separation of activated [³H]dexamethasone-receptor complex at salt concentrations above 100 mm NaCl. This procedure therefore had to be carried out under conditions of relatively low ionic strength. Finally, a one-step rapid method is described for the separation of activated [³H]dexamethasone-receptor complex from nonactivated receptor complex. The homogeneous population of activated complex thus obtained should have considerable applicability in studies of the mechanisms of in vitro glucocorticoid-receptor activation.     

Degradation without apparent change in size of molybdate-stabilized nonactivated glucocorticoid-receptor complexes in rat thymus cytosol

We have investigated the stability of the [3H]dexamethasone 21-mesylate-labeled nonactivated glucocorticoid-receptor complex in rat thymus cytosol containing 20 mM sodium molybdate. Cytosol complexes were analyzed under nondenaturing conditions by gel filtration chromatography in the presence of molybdate and under denaturing conditions by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. When analyzed under nondenaturing conditions, complexes from fresh cytosol and from cytosol left for 2 h at 3 degrees C eluted from gel filtration as a single peak of radioactivity with a Stokes radius of approximately 7.7 nm, suggesting that no proteolysis of the complexes had occurred in either cytosol. When analyzed under denaturing conditions, however, whereas the fresh cytosol gave a receptor band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis at Mr approximately 90,000 (corresponding to the intact complex), the cytosol that had been left for 2 h at 3 degrees C gave only a fragment (Mr approximately 50,000). This fragment, just as the intact complex, could be thermally activated to a DNA-binding form. Proteolysis of the receptor could be blocked by preparing the cytosol in the presence of EGTA, leupeptin, or a heat-stable factor present in the cytosol of rat liver and WEHI-7 mouse thymoma cells. From these results we conclude: (i) 20 mM molybdate does not protect the nonactivated glucocorticoid-receptor complex present in rat thymus cytosol against proteolysis under conditions which are commonly used for cell-free labeling of the receptor, and (ii) the demonstration of a Stokes radius of approximately 8 nm for the nonactivated glucocorticoid-receptor complex is not sufficient to indicate that the receptor complex is present in its intact form.     

Effects of preincubation temperature on the detection of fastidious organisms in delayed-entry samples in the BacT/ALERT 3D blood culture system

This study evaluates the effect of preincubation on delayed-entry samples for fastidious organisms including the HACEK group, Streptococcus species, Neisseria meningitidis, Haemophilus species and Corynebacterium species for the BacT/ALERT 3D System (bioMérieux) using the FA (aerobic) medium.Bottles were inoculated with two different concentrations (0.5 McFarland and a 1:100,000 dilution) of each organism and either loaded into the system immediately or stored at 4 °C, room temperature (RT) or 37 °C for 24 hours (h) prior to loading.The detection rate (DR) was 92.5% for bottles loaded immediately for both concentrations with a mean time to detection (TTD) of 26.7 h (standard deviation (SD): 14.7 h) for the low concentration and 9.21 h (SD: 5.3 h) for the high concentration. Preincubation at 4 °C did not affect the DR for either of the two concentrations in comparison to no preincubation. The DR at RT was 90.0% for the low concentration and 83.6% for the high concentration. At 37 °C the DR was 76.3% and 66.3% for the low and the high concentrations respectively. The average TTD was inversely correlated with the preincubation temperature. An incubation of four days was sufficient, with the exception of Eikenella corrodens and Gemella sanguinis. The serotype of Streptococcus pneumoniae or Neisseria meningitidis did not influence the TTD. Kingella kingae remained undetected.For the retrieval of the above mentioned bacteria we recommend storage of bottles at room temperature. In case of erroneous storage at 37 °C subcultivation is advisable.All cases with a negative result on day four should be reevaluated and eventually new material for alternative diagnostic procedures should be retrieved.     

Chromatographic separation of nontransformed and transformed glucocorticoid-receptor complexes from rat liver cytosol. Use of tungstate in the purification, inactivation, and resolution of receptor forms

Aliquots of rat liver cytosol glucocorticoid-receptor complexes (GRc) were transformed by an incubation with 8-10 mM ATP at 0 degrees C and were compared with those transformed by an exposure to 23 degrees C. The extent of receptor transformation was measured by chromatography of the samples over columns of DEAE-Sephacel. The ATP-transformed complexes, like those which were heat-transformed, exhibited lower affinity for the positively charged ion-exchange resin and were eluted with 0.12 M KCl (peak-I): the nontransformed complexes appeared to possess higher affinity and required 0.21 M KCl (peak II) for their elution. As expected, the receptor in the peak-I exhibited the DNA-cellulose binding capacity and sedimented as 4S in sucrose gradients. Peak II contained an 8-9S glucocorticoid receptor (GR) form that showed reduced affinity for DNA-cellulose. Presence of sodium tungstate (5 mM) prevented both heat and ATP transformation of the GRc resulting in the elution of the complexes in the region of nontransformed receptors. When parallel experiments were performed, binding of the cytosol GRc to rat liver nuclei or DNA-cellulose was seen to increase 10-15 fold upon transformation by heat or ATP: tungstate treatment blocked this process completely. The transformed and nontransformed GRc were also differentially fractionated by (NH4)2SO4: tungstate-treated (nontransformed) receptor required higher salt concentration and was precipitated at 55% saturation. In addition, the GRc could be extracted from DNA-cellulose by an incubation of the affinity resin with sodium tungstate resulting in approximately 500-fold purification of the receptor with a 30% yield. These studies show that the nontransformed, and the heat-, salt-, and ATP-transformed GRc from the rat liver cytosol can be separated chromatographically, and that the use of tungstate facilitates the resolution of these different receptor forms. In addition, extraction of the receptor from DNA-cellulose by tungstate provides another new and efficient method of partial receptor purification.     

Inactivation of rat liver glucocorticoid receptor by molybdate. Effects on both non-activated and activated receptor complexes.

When freshly prepared glucocorticoid-receptor complex from rat liver cytosol was incubated at 23 degrees C in the presence of sodium molybdate, its subsequent binding to isolated nuclei, DNA-cellulose and ATP-Sepharose was blocked. In addition, binding to these acceptors by cytosol receptor complex fractionated with (NH4)2SO4 was also blocked by incubation of the complexes with 50 mM-sodium molybdate. However, molybdate had no effect on the binding of activated receptor complexes to ATP-Sepharose. Molybdate was also effective in extracting the nuclear- and DNA-cellulose-bound glucocorticoid-receptor complexes in a dose-dependent manner. Molybdate appears to exert its effects directly on the receptor by interacting with both non-activated and activated receptor forms.     

Resolution of the molecular forms of rat liver glucocorticoid receptor by affinity chromatography on immobilized heparin

Rat liver cytosolic glucocorticoid receptor labelled with [³H] dexamethasone and stabilized with molybdate was bound to heparin-ultrogel and eluted with NaCl or heparin as a single peak of radioactivity. After heat exposure of cytosol, two steroid receptor complexes could be separated by NaCl or heparin. Characterization of the two forms was performed by means of affinity towards isolated nuclei, ssucrose gradient centrigugation and gel exclusion high performance liquid chromatography. The results presented here suggest that the two forms eluted from heparin-agarose correspond to the untransformed and transformed states of the glucocorticoid receptor complex. Taken together, these observations argue in favor of heparin-ultrogel as a suitable procedure to study the mechanism of glucocorticoid-receptor transformation.     

Immunofluorescence microscopy of the intracellular translocation of glucocorticoid-receptor complexes in rat hepatoma (HTC) cells

Antibodies to the two dexamethasone-binding proteins from rat liver cytosol have been elicited in rabbits. These antibodies precipitate the dexamethasone binding activities from rat liver cytosol as weil as cytosol from Hepatoma Tissue Culture (HTC) cells. Antibodies to the 45 000 D protein have been used for demonstration of the intracellular dynamics of the glucocorticoid receptor complex by immunofluorescence microscopy, comparing HTC cells treated with dexamethasone at 4 and 37 °C.     

Formamide denaturation of chromosomal DNA for in situ hybridization and C-band preparation in the guinea pig, Cavia porcellus

Cytological preparations were incubated in 0.07 N NaOH at room temperature or 90% formamide (final salt concentration 2 × SSC) at either 65 °C or 37 °C for 2.5 h to denature guinea pig chromosomes. Chromosomes treated with NaOH or formamide at 65 °C showed a large amount of DNA loss, while chromosomes treated with formamide at 37 °C showed little or no DNA loss. Repeated sequences were isolated from guinea pig DNA and [³H]cRNA was transcribed with Escherichia coli RNA polymerase for in situ hybridization. Localization of the [³H]cRNA occurred in the centromeric regions and C-band positive short arms of almost all of the chromosomes in the NaOH preparations. Chromosomes treated with formamide at 65 °C showed the same grain distribution with a decrease in the number of grains/cluster. Slides incubated in formamide at 37 °C showed localization in only a few chromosomes and the number of grains/cluster was greatly diminished. Thermal denaturation of isolated chromatin indicated that incubation of chromosomes in formamide at 37 °C did not fully denature the DNA. C-bands could be induced by treating slides in formamide at either 65 °C or 37 °C when followed by a “reassociation” in 2 × SSC at 65 °C for 16 h. If the “reassociation” step was omitted, C-bands were found in the 65 °C formamide slides but not the 37 °C formamide slides.