FKBP51 and Cyp40 are positive regulators of androgen-dependent prostate cancer cell growth and the targets of FK506 and cyclosporin A

Prostate cancer (PCa) growth is dependent on androgens and the androgen receptor (AR), which acts by modulating gene transcription. Tetratricopeptide repeat (TPR) proteins (FKBP52, FKBP51 and Cyp40) interact with AR in PCa cells, suggesting roles in AR-mediated gene transcription and cell growth. We report here that FKBP51 and Cyp40, but not FKBP52, are significantly elevated in PCa tissues and in androgen-dependent (AD) and -independent (AI) cell lines. Overexpression of FKBP51 in AD LNCaP cells increased AR transcriptional activity in the presence and absence of androgen, whereas siRNA knockdown of FKBP51 dramatically decreased AD gene transcription and proliferation. Knockdown of Cyp40 also inhibited androgen-mediated transcription and growth in LNCaP cells. However, disruption of FKBP51 and Cyp40 in the AI C4-2 cells caused only a small reduction in proliferation, indicating that Cyp40 and FKBP51 predominantly regulate AD cell proliferation. Under knock-down conditions, the inhibitory effects of TPR ligands, CsA and FK506, on AR activity were not observed, indicating that Cyp40 and FKBP51 are the targets of CsA and FK506, respectively. Our findings demonstrate that FKBP51 and Cyp40 are positive regulators of AR that can be selectively targeted by CsA and FK506 to achieve inhibition of androgen-induced cell proliferation. These proteins and their cognate ligands thus provide new strategies in the treatment of PCa

Stepwise assembly of a glucocorticoid receptor.hsp90 heterocomplex resolves two sequential ATP-dependent events involving first hsp70 and then hsp90 in opening of the steroid binding pocket

A system of five purified proteins that assembles stable glucocorticoid receptor (GR)-hsp90 heterocomplexes has been reconstituted from reticulocyte lysate. Two proteins, hsp90 and hsp70, are required for the activation of steroid binding activity that occurs with heterocomplex assembly, and three proteins, Hop, hsp40, p23, act as co-chaperones that enhance activation and assembly (Morishima, Y., Kanelakis, K. C., Silverstein, A.M., Dittmar, K. D., Estrada, L., and Pratt, W. B. (2000) J. Biol. Chem. 275, 6894-6900). Here we demonstrate that the first step in assembly is the ATP-dependent and hsp40 (YDJ-1)-dependent binding of hsp70 to the GR. After elimination of free hsp70, these preformed GR.hsp70 complexes can be activated to the steroid binding state by the hsp70 free assembly system in a second ATP-dependent step. hsp90 is required for opening of the steroid binding pocket and is converted to its ATP-dependent conformation during this second step. We predict that hsp70 in its ATP-dependent conformation binds initially to the folded receptor and is then converted to the ADP-dependent form with high affinity for hydrophobic substrate. This conversion initiates the opening of the hydrophobic steroid binding pocket such that it can now accept the hydrophobic binding form of hsp90, which in turn must be converted to its ATP-dependent conformation for the pocket to be accessible by steroid.

Cyclosporin A potentiates the dexamethasone-induced mouse mammary tumor virus-chloramphenicol acetyltransferase activity in LMCAT cells: a possible role for different heat shock protein-binding immunophilins in glucocorticosteroid receptor-mediated gene expression

As previously observed for FK506, we report here that cyclosporin A (CsA) treatment of mouse fibroblast cells stably transfected with the mouse mammary tumor virus-chloramphenicol acetyltransferase (MMTV-CAT) reporter plasmid (LMCAT cells) results in potentiation of dexamethasone (Dex)-induced CAT gene expression. Potentiation by CsA is observed in cells treated with 10-100 nM Dex but not in cells treated with 1 microM Dex, a concentration of hormone which results in maximum CAT activity. At 10 nM Dex, 1-5 microM CsA provokes an approximately 50-fold increase in CAT gene transcription, compared with transcription induced by Dex alone. No induction of CAT gene expression is observed in cells treated with CsA or FK506 in the absence of Dex. The antisteroid RU 486 abolishes effects obtained in the presence of Dex. Using a series of CsA, as well as FK506, analogs, including some devoid of calcineurin phosphatase inhibition activity, we conclude that the potentiation effects of these drugs on Dex-induced CAT gene expression in LMCAT cells do not occur through a calcineurin-mediated pathway. Western-blotting experiments following immunoprecipitation of glucocorticosteroid receptor (GR) complexes resulted in coprecipitation of GR, heat shock protein hsp90 and two immunophilins: the FK506-binding protein FKBP59 and the CsA-binding protein cyclophilin 40 (CYP40). Two separate immunophilin-hsp90 complexes are present in LMCAT cells: one containing CYP40-hsp90, the other FKBP59-hsp90. Thus, both FKBP59 and CYP40 can be classified as hsp-binding immunophilins, and their possible involvement as targets of immunosuppressants potentiating the GR-mediated transcriptional activity is discussed.

Stabilization in vitro of the untransformed glucocorticoid receptor complex of S49 lymphocytes by the immunophilin ligand FK506

Untransformed steroid receptors are large heteromeric complexes which have been shown to contain the mammalian heat shock proteins hsp56, hsp70 and hsp90. Based on functional and sequence homology studies, it was recently discovered that hsp56 also belongs to the FKBP class of immunophilin proteins, which are thought to mediate the actions of the immunosuppressive drugs FK506 and rapamycin. This discovery has led to the speculation that FK506 and related drugs could influence the actions of steroid receptors. In this work, we have examined the effects of FK506 on the transformation and hormone-binding properties of glucocorticoid receptors (GR) present in the cytosolic fraction of mouse S49 lymphocyte cells. Based on immunoprecipitation studies, it was found that hsp56 was indeed a component of untransformed GR complexes in S49 cytosols. It was also found that the untransformed but not the transformed GR was retained following affinity chromatography with FK506-affigel resin, reinforcing the possibility that hsp56 within the untransformed GR complex could be a target for the actions of FK506. Using a DNA-cellulose-binding assay, FK506 exhibited a 60% inhibition of dexamethasone (Dex)-induced transformation of the GR to the DNA-binding state, while sodium molybdate, a transition metal oxyanion known to stabilize GR complexes, was 100% effective. This inhibition of GR transformation by FK506 was shown to correlate with an inhibition of Dex-induced GR/hsp90 dissociation, with 10 microM FK506 preventing 48% of the GR/hsp90 complexes from dissociating. Scatchard analysis of GR hormone-binding function was performed, with FK506 treatment of cytosols causing Kd values to decrease (3.36 nM) as compared to vehicle (8.42 nM) and no-addition (9.82 nM) controls. Taken together, our results suggest that FK506 can stabilize the untransformed GR complex of S49 cells and that this stabilization in turn results in an increase in GR ligand-binding affinity. Although we speculate that these actions of FK506 on the GR complex are mediated by the associated hsp56 component, other possible mechanisms are also discussed.

Potentiation of glucocorticoid receptor-mediated gene expression by heat and chemical shock

We have examined the effects of heat shock on glucocorticoid receptor (GR)-mediated gene transcription in an L929 cell line derivative (LMCAT2) stably transfected with the mouse mammary tumor virus-chloramphenicol acetyltransferase (MMTV-CAT) reporter plasmid. Exposure of the LMCAT2 cells to heat or chemical shock resulted in a large increase in dexamethasone (Dex)-induced expression of CAT enzyme activity. This potentiation of hormone-induced MMTV-CAT expression was dependent on the magnitude of the stress event and on the Dex concentration, with maximal increases observed for 1 microM Dex after 2 h at 43 C or 2 h at 200 microM sodium arsenite. Heat shock potentiation of MMTV-CAT expression was not seen in an L929 cell derivative devoid of GR or in LMCAT2 cells treated with RU486 antagonist, suggesting that this effect of stress on CAT gene expression was mediated by the GR. Using a quantitative Western blot procedure, the amount of GR protein in the nucleus of cells subjected to combined heat shock and Dex treatment was no greater than the amount of nuclear GR in cells treated with hormone alone, indicating that the stress potentiation effect was not the result of increased nuclear translocation or retention by the GR. In addition, equally strong potentiations of MMTV-CAT expression were observed for cells subjected to heat shock either before or after Dex-mediated translocation of the GR to the nucleus. Thus, the major effect of stress on GR transcription enhancement activity appears to occur after the GR is bound to its high affinity nuclear acceptor sites. We have used a series of MMTV-CAT reporter constructs containing varying portions of the long terminal repeat regulatory region to show that a putative heat shock transcription factor-binding sequence at position -437 of the long terminal repeat is not required for this effect of heat shock on MMTV-CAT expression. A stress-induced increase in hormone-mediated CAT gene expression was observed for a minimal CAT reporter controlled by two synthetic glucocorticoid response elements and a TATA box sequence. Thus, it is unlikely that any DNA-binding transcription factor, other than GR, is required for this effect of stress on transcription by the hormone-bound GR. Based on these results, a model of heat shock enhancement of GR-mediated gene expression is developed in which stress acts on the DNA-bound GR, on a putative heat shock-activated adaptor, or on components of the RNA-polymerase-II complex.

FK506 binding to the 56-kilodalton immunophilin (Hsp56) in the glucocorticoid receptor heterocomplex has no effect on receptor folding or function

It has recently been reported that the hsp56 component of glucocorticoid receptor heterocomplexes is an immunophilin of the FK506 binding class [Yem, A. W., Tomasselli, A. G., Heinrikson, R. L., Zurcher-Neely, H., Ruff, V. A., Johnson, R. A., & Deibel, M. R. (1992) J. Biol. Chem. 267, 2868-2871; Tai, P. K., Albers, M. W., Chang, H., Faber, L. E., & Schreiber, S. L. (1992) Science 256, 1315-1318]. The existence of binding proteins for these two potent groups of immunosuppressants in the same molecular complex compels us to ask whether FK506 affects glucocorticoid receptor function. We show here that hsp56 is a component of the native L-cell glucocorticoid receptor heterocomplex and that [3H]FK506 binds to the immunopurified, untransformed receptor complex. However, at concentrations in excess of those required to occupy all of its binding sites on hsp56, FK506 does not affect the steroid binding activity of the receptor nor does it stabilize or dissociate the receptor-hsp90 complex. FK506 does not affect steroid-mediated hsp90 dissociation from the receptor in vitro, and it does not affect steroid-mediated nuclear transfer of the receptor or steroid-mediated transcriptional enhancement from a reporter in intact cells. When immunopurified mouse glucocorticoid receptor is reconstituted into a heat shock protein complex by rabbit reticulocyte lysate, hsp56 is present in the reconstituted complex in addition to hsp90 and hsp70. FK506, however, does not affect reconstitution of the complex or return of the receptor to the steroid binding state, a change of conformation that occurs upon receptor association with hsp90.(ABSTRACT TRUNCATED AT 250 WORDS)

A heat shock protein complex isolated from rabbit reticulocyte lysate can reconstitute a functional glucocorticoid receptor-Hsp90 complex

When unliganded glucocorticoid receptor that has been stripped free of associated proteins is incubated with rabbit reticulocyte lysate, the receptor becomes associated with the 70- and 90-kDa heat shock proteins (hsp70 and hsp90), and the untransformed state of the receptor is functionally reconstituted [Scherrer, L. C., Dalman, F. C., Massa, E., Meshinchi, S., & Pratt, W. B. (1990) J. Biol. Chem. 265, 21397-21400]. Recently, an hsp70-containing protein complex (200-250 kDa) purified from rabbit reticulocyte lysate was shown to maintain a fusion protein bearing the mitochondrial matrix-targeting signal in a state that is competent for mitochondrial import [Sheffield, W. P., Shore, G. C., & Randall, S. K. (1990) J. Biol. Chem. 265, 11069-11076]. In this work, we show that this partially purified mitochondrial import-competent fraction contains both hsp90 and hsp70. When the purified fraction is immunoadsorbed with a monoclonal antibody specific for hsp90, a significant portion of the hsp70 is co-immunoadsorbed, suggesting that hsp90 and hsp70 are present together as a complex. The partially purified fraction maintains a hybrid precursor protein containing the mitochondrial matrix-targeting signal of rat pre-ornithine carbamyl transferase in an import-competent state. Incubation of immunopurified glucocorticoid receptor with this fraction of reticulocyte lysate results in ATP-dependent association of the receptor with both hsp70 and hsp90, and the resulting complexes are functional as assessed by return of the receptor to the high-affinity steroid binding conformation. The glucocorticoid receptor hetero-complex reconstituting activity of the lysate fraction is low relative to its mitochondrial import activity. Importantly, however, this is the first demonstration of the functional and structural reconstitution of the untransformed state of any steroid receptor utilizing a partially purified system.

Heat shock induces translocation to the nucleus of the unliganded glucocorticoid receptor

There have been many reports demonstrating the specific association of several heat shock proteins with unliganded steroid hormone receptors. However, little evidence to date has been proposed to link steroid receptor action with the heat shock response in cells. In this paper, we demonstrate the effect of heat and chemical stress on glucocorticoid receptor subcellular localization in mouse L929 cells and in a stably transfected Chinese hamster ovary cell line (WCL2) which over-expresses the mouse glucocorticoid receptor. When WCL2 cells are exposed to 43 degrees C, there is a time-dependent decrease in glucocorticoid receptor hormone-binding capacity in the cytosolic fraction of these cells that correlates with a decrease in amount of glucocorticoid receptor protein. Analysis of both cytosolic and nuclear fractions for glucocorticoid receptor protein via quantitative Western blotting reveals that the unliganded glucocorticoid receptor of non-shocked L929 and WCL2 cells is localized primarily in the cytosolic fraction, whereas unliganded receptor of heat-shocked cells is found almost exclusively in the nuclear fraction. A similar shift to nuclear localization for unliganded glucocorticoid receptor is noted in L929 and WCL2 cells subjected to chemical shock (sodium arsenite). As treatment of these cells with glucocorticoid hormone also results in glucocorticoid receptor that is tightly bound within the nuclear fraction, it is speculated that heat and chemical stress provide a hormone-independent mechanism by which glucocorticoid receptor is transformed to the high affinity nuclear-binding state characteristic of the hormone-bound, transcriptionally active receptor.

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.

Hormone-free mouse glucocorticoid receptors overexpressed in Chinese hamster ovary cells are localized to the nucleus and are associated with both hsp70 and hsp90

In this work, we examine the cellular localization and protein interactions of mouse glucocorticoid receptors that have been overexpressed in Chinese hamster ovary (CHO) cells (Hirst, M. A., Northrop, J. P., Danielsen, M., and Ringold, G. M. (1990) Mol. Endocrinol. 4, 162-170). We demonstrate that wild-type unliganded mouse glucocorticoid receptor, which is expressed in CHO cells to a level approximately 10 times that of L cells, is localized entirely to the nucleus by indirect immunofluorescence with the BuGR antireceptor monoclonal antibody. Overexpressed receptors that have either no hormone binding activity or no DNA binding activity because of point mutations also localize to the nucleus, providing genetic proof that the nuclear localization cannot reflect a steroid-mediated shift of the receptor from the cytoplasm to the nucleus and that DNA binding activity is not required for nuclear localization. Like unliganded progesterone receptors, which also associate in a loosely bound "docking" complex with the nucleus, the mouse glucocorticoid receptor overexpressed in CHO cells is associated with both hsp90 and hsp70. This is in contrast to the untransformed mouse glucocorticoid receptor in L cell cytosol, which is associated with hsp90 but not hsp70. The difference in hsp70 association between cell types could reflect overexpression of the receptor in CHO cells. However, like receptors in CHO cells selected for very high levels of overexpression, receptors in CHO cells selected for an intermediate level of receptor expression that is comparable to that of L cells are also bound to hsp70. This observation argues against an explanation of hsp70 association based purely on receptor overexpression, and we speculate that association of the unliganded glucocorticoid receptor with hsp70 might be a consequence of its nuclear localization in the CHO cells. Although there are differences between the mouse receptor in CHO cells and L cells, the nuclear localization signal of the untransformed mouse receptor reacts equivalently with the AP64 antibody against NL1 in cytosols prepared from both cell types.

Evidence that the conserved region in the steroid binding domain of the glucocorticoid receptor is required for both optimal binding of hsp90 and protection from proteolytic cleavage. A two-site model for hsp90 binding to the steroid binding domain

Steroid hormone receptors contain a conserved sequence of amino acids within the steroid binding domain, and we have previously speculated that this conserved region is the site of interaction of the glucocorticoid receptor with hsp90 (Danielsen, M., Northrop, J. P., and Ringold, G. M. (1986) EMBO J. 5, 2513-2522; Pratt, W. B., Jolly, D. J., Pratt, D. V., Hollenberg, S. M., Giguere, V., Cadepond, F. M., Schweizer-Groyer, G., Catelli, M.-G., Evans, R. M., and Baulieu, E.-E. (1988) J. Biol. Chem. 263, 267-273). In this work, we transfect COS-7 cells with three mutants of the mouse glucocorticoid receptor deleted for all or part of this conserved region. The mutant receptor missing the entire conserved region is very unstable and is found predominantly as cleavage products. Approximately one-third of the cleavage products have lost most or all of the steroid binding domain. This mutant receptor has a constitutive activity that is about one-third that of the steroid-bound wild type receptor in stimulating transcription from a reporter gene. We propose that the partial constitutive activity results from proteolytic cleavage of the steroid binding domain from the rest of the receptor, thus removing the functional repression determined by this domain. This mutant receptor is associated with hsp90 in cytosols prepared in the presence of molybdate but, when molybdate is not present, the receptor is unstable and there is very little receptor-associated hsp90. This observation is consistent with the proposal that binding of hsp90 helps to stabilize the glucocorticoid receptor against proteolysis, and it demonstrates that the site of molybdate interaction with the receptor lies outside of the conserved sequence. Our data are interpreted according to a two-site model in which hsp90 interacts with the steroid binding domain at two sites. One site is in the conserved sequence, and the other is at a transition metal oxyanion binding site, located between the conserved sequence and the COOH terminus.

The 56-59-kilodalton protein identified in untransformed steroid receptor complexes is a unique protein that exists in cytosol in a complex with both the 70- and 90-kilodalton heat shock proteins

It has previously been shown that 9S, untransformed progestin, estrogen, androgen, and glucocorticoid receptor complexes in rabbit uterine and liver cytosols contain a 59-kDa protein [Tai, P. K., Maeda, Y., Nakao, K., Wakim, N. G., Duhring, J. L., & Faber, L. E. (1986) Biochemistry 25, 5269-5275]. In this work we show that the monoclonal antibody KN 382/EC1 raised against the rabbit 59-kDa protein reacts with 9S, untransformed glucocorticoid receptor complexes in cytosol prepared from human IM-9 lymphocytes but not with 4S salt-transformed receptors. The human protein recognized by the EC1 antibody is a 56-kDa protein (p56) of moderate abundance located predominantly in the cytoplasm by indirect immunofluorescence. There are at least six isomorphs of p56 by two-dimensional gel analysis. N-Terminal sequencing (20 amino acids) shows that p56 is a unique human protein. When p56 is immunoadsorbed from IM-9 cell cytosol, both the 70- and 90-kDa heat shock proteins are coadsorbed in an immune-specific manner. Neither heat shock protein reacts directly with the EC1 antibody. We conclude that p56 exists in cytosol in a higher order complex containing hsp70 and hsp90, both of which in turn have been found to be associated with untransformed steroid receptors.

Elimination and reconstitution of the requirement for hormone in promoting temperature-dependent transformation of cytosolic glucocorticoid receptors to the DNA-binding state

Cytosols contain a heat-stable, chelatable, anionic, molybdate-like factor that stabilizes glucocorticoid receptors in a heteromeric complex with hsp90 (refers to the 90-kDa heat shock protein) and inhibits their transformation to the DNA-binding state (Meshinchi, S., Grippo, J.F., Sanchez, E.R., Bresnick, E.H., and Pratt, W.B. (1988) J. Biol. Chem. 263, 16809-16817). In this work, we demonstrate that removal of this factor by passage of L cell cytosol through the metal-chelating resin Chelex-100 makes the glucocorticoid receptor unstable, thus markedly facilitating both its dissociation from hsp90 and its transformation to the DNA-binding state. In normal cytosol, both temperature-mediated dissociation of hsp90 and temperature-mediated receptor transformation are hormone-dependent events. In the Chelex-treated, metal-depleted cytosol, however, temperature-mediated dissociation of hsp90 and receptor transformation occur very rapidly in a manner that is no longer hormone-dependent. When boiled L cell cytosol is added to the metal-depleted receptor system, the hormone dependence of both temperature-mediated dissociation of receptor from hsp90 and receptor transformation to the DNA-binding state is reconstituted. Like boiled cytosol, molybdate stabilizes the receptor complex and inhibits its transformation in metal-depleted cytosol, but it does not reconstitute the hormone dependence of the system. These results support the proposal that an endogenous metal anion interacts with the glucocorticoid receptor to stabilize it in the heteromeric, inactive, non-DNA-binding state in cytosol and that binding of the hormone promotes conversion of the receptor to the DNA-binding state through an effect on this metal anion center.

Immunofluorescence colocalization of the 90-kDa heat-shock protein and microtubules in interphase and mitotic mammalian cells

A mouse monoclonal antibody (AC88) that was raised against the 88-kDa heat-shock protein of the water mold, Achlya ambisexualis, and that cross-reacts with the 90-kDa mammalian heat-shock protein (hsp90), and an antibody against tubulin were used to localize hsp90 and microtubules, respectively, in the same cultured rat endothelial and PtK1 epithelial cells by indirect immunofluorescence. AC88 and tubulin antibodies labeled the same structures in cells at all stages of the cell cycle, regardless of whether cells were permeabilized before or after fixation. Labeling of cell structures by both AC88 and anti-tubulin antibodies was identically affected by treating cells with colcemid. Double labeling with AC88 and anti-tubulin antibodies in interphase and mitotic cells is consistent with the conclusion that all microtubules are labeled and that no subclass of microtubules is preferentially labeled. Fluorescent labeling by AC88 was prevented by preabsorption of the antibody with purified rat hsp90 but was unaffected by preabsorption with purified 6S tubulin dimer. In contrast to AC88, fluorescent labeling by an anti-tubulin antibody was prevented by preabsorption with tubulin dimer but was unaffected by preabsorption with rat hsp90. Western-blot analysis demonstrated no cross-reactivity of AC88 for tubulin and no cross-reactivity of the anti-tubulin antibody for hsp90. A polyclonal antiserum fraction from a rabbit immunized with the 89-kDa heat-shock protein from chicken also labeled the mitotic apparatus in dividing cells and, somewhat less distinctly, fibrous structures in interphase cells. Labeling by hsp89 anti-serum was prevented by absorption with hsp90. AC88 also labeled microtubules in cultured mouse (L929 and 3T3), rat (endothelium and TRST), hamster (CHO) and primate (BSC, COS-1 and HeLa) cell lines. The demonstration of colocalization of hsp90 with microtubules should provide a valuable clue to eventual understanding of the cellular function of this ubiquitous, conserved and abundant stress-response protein.

Characterization of 2,3,7,8-tetrachlorodibenzo-p-dioxin-mediated decreases in dexamethasone binding to rat hepatic cytosolic glucocorticoid receptor

An investigation of the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the liver cytosolic glucocorticoid receptor (GRc) in intact and adrenalectomized (ADX) rats, using equilibrium binding analysis, sucrose gradient sedimentation, and affinity labeling experiments, clearly demonstrated that TCDD significantly reduced the binding capacity (Bmax) of the hepatic GRc but did not alter the apparent equilibrium dissociation constant (Kd). This effect was maximal after 24 hr and was still present 22 days after treatment. Western blot analysis revealed that TCDD treatment did not cause a comparable decrease in the levels of immunodetectable receptor protein, which suggests that the steroid-binding properties of the hepatic GRc are altered, rather than the absolute concentration of receptor protein. Studies of TCDD effects on the uptake of GRc by nuclei indicated that TCDD treatment did not alter the ability of the steroid-GRc complex to be taken up by nuclei; however, TCDD treatment did increase the total capacity of liver nuclei to bind steroid-GRc complexes. TCDD dose-response studies that compared the hepatic GRc steroid binding of ADX and intact rats indicated that adrenalectomy markedly enhanced the response to TCDD. Significant effects on the GRc binding in ADX animals were induced at TCDD doses that were 10,000 times lower than those required for a response in intact rats. Analysis of two other biochemical markers demonstrated that ADX rats were 10-fold more sensitive to the induction of microsomal benzo[a]pyrene hydroxylase but of similar sensitivity to reduction of epidermal growth factor receptor binding, when compared with the responses of intact animals. These data indicate that adrenal status may be important in modulating the responses of the animals to TCDD and that the alteration of the hepatic GRc pathway may have a role in some of the actions of TCDD.

Interaction of the glucocorticoid receptor with the Mr 90,000 heat shock protein: an evolving model of ligand-mediated receptor transformation and translocation

Reports from several laboratories support a model for glucocorticoid receptor (GR) transformation in cytosol in which a heteromeric 9S complex of GR and the Mr 90,000 heat shock protein undergo a temperature-dependent and hormone-promoted dissociation to yield the free DNA-binding form of the receptor. In this paper, we review evidence that the 9S heteromeric complex is derived from the normal inactive state of the receptor in the intact cell and that both Mr 90,000 heat shock protein and the untransformed GR localize by immunofluorescence with specific monoclonal antibodies to microtubules in a variety of cell types in culture. We propose that an association with cytoskeleton may be required for translocating the GR from its cytoplasmic site of synthesis to its nuclear site of action and that the 9S complex is derived from this cytoskeleton-associated form. Similar molybdate-stabilized 9S complexes can be obtained for all of the steroid receptors, several of which clearly are localized to the nucleus prior to exposure to hormone. These receptors may have moved to the terminus of the translocation pathway where they remain in a cytoskeleton-bound "docking" position. We speculate that, in the intact cell, ligand-dependent dissociation of Mr 90,000 heat shock protein permits the steroid receptors to progress by some ordered mechanism to their high affinity sites of action within the nucleus.

Evidence that the 90-kDa heat shock protein is necessary for the steroid binding conformation of the L cell glucocorticoid receptor

Using L cell glucocorticoid receptors that have been immunopurified by adsorption to protein A Sepharose with a monoclonal antireceptor antibody, we have developed an assay to study the requirements for maintenance of steroid-binding capacity. After rapid purification by immunoadsorption, heteromeric receptor complexes retain the ability to bind glucocorticoid hormone. When the receptor complexes are warmed at 20 degrees C, steroid-binding capacity is lost, and the 90-kDa heat shock protein (hsp90) dissociates from the receptor. The rates of both temperature- and salt-dependent dissociation of hsp90 parallel the rates of loss of hormone-binding activity. Molybdate and hydrogen peroxide stabilize the hsp90-receptor complex against temperature-dependent dissociation. Molybdate, however, is much more effective in stabilizing steroid-binding capacity than peroxide. Receptors that have been inactivated in the absence of molybdate or peroxide cannot be reactivated. Inactivation of steroid-binding capacity occurs in the presence or absence of reducing agent, and inactivation is not accompanied by receptor cleavage or dephosphorylation. Under no conditions does an hsp90-free receptor bind steroid. Receptor bound to hsp90 can be cleaved to the 27-kDa meroreceptor in the presence of molybdate with retention of both hsp90 and steroid-binding activity. These observations lead us to propose that hsp90 is necessary but not sufficient for maintaining a competent high affinity glucocorticoid-binding site. Although the 27-kDa meroreceptor fragment is not itself sufficient for a competent binding site, it is sufficient when it is associated with hsp90.

Evidence that the endogenous heat-stable glucocorticoid receptor stabilizing factor is a metal component of the untransformed receptor complex

Boiled cytosols prepared from a wide variety of sources contain a low Mr factor that inhibits glucocorticoid receptor transformation to the DNA-binding state (Leach, K.L., Grippo, J.F., Housley, P.R., Dahmer, M.K., Salive, M.E., and Pratt, W.B. (1982) J. Biol. Chem. 257, 381-388). In this work, we show that this endogenous factor, which is partially purified from rat liver, produces all of the effects of the group VI-A transition metal oxyanions molybdate and vanadate on the structure and function of glucocorticoid receptors in cytosol preparations. Like molybdate, the endogenous factor behaves as a strong anion with an apparent Mr of 340 on Bio-Gel P-2, and it binds to both hydroxylapatite and Chelex 100 resins. The receptor stabilizing activity of the factor is completely stable to heating at 320 degrees C for 1 h. The small size, profound heat stability, and absorption by a metal chelating resin strongly suggest that the factor is an endogenous metal anion. As reduction of the concentration of the factor in cytosol promotes generation of the DNA-binding form of the receptor, we suggest that this endogenous metal anion interacts with the receptor to stabilize the 9 S complex and maintain the receptor in its untransformed, non-DNA-binding state. We propose that molybdate and vanadate may exert their effects on the untransformed receptor by interacting with the binding site for the endogenous metal anion.

Localization of phosphorylation sites with respect to the functional domains of the mouse L cell glucocorticoid receptor

Digestion of the rat liver glucocorticoid receptor with chymotrypsin results in the generation of a 42-kDa fragment which contains the steroid-binding and DNA-binding domains and the antigenic site for the BuGR anti-glucocorticoid receptor monoclonal antibody, while digestion with trypsin generates a 15-kDa receptor fragment containing only the DNA-binding function and the BuGR epitope (Eisen, L.P., Reichman, M.E., Thompson, E.B., Gametchu, B., Harrison, R. W., and Eisen, H.J. (1985) J. Biol. Chem. 260, 11805-11810). In this paper, glucocorticoid receptor of mouse L cells that were grown in the presence of [32P]orthophosphate was digested with trypsin or chymotrypsin (either before or after immune purification with BuGR antibody) and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, autoradiography, and Western blotting. The receptor is endogenously phosphorylated only on serine residues. Chymotrypsin digestion results in a 32P-labeled 42-kDa receptor fragment which contains steroid-binding, DNA-binding, and BuGR-reactive sites. Trypsin digestion generates a 27-kDa steroid-bound fragment (meroreceptor) which is not labeled with 32P and a 32P-labeled 15-kDa fragment which contains both the DNA-binding domain and the BuGR epitope. We have calculated that there are 4 times as many phosphate residues in the intact receptor than in the 42-kDa chymotrypsin fragment. From examination of 32P-labeled receptor fragments, we have deduced that one phosphate is located between amino acids 398 and 447, a region containing the BuGR epitope and about one-third of the DNA-binding domain, and the remaining three phosphates appear to be clustered just to the amino-terminal side of the BuGR epitope in a region defined by amino acids 313 to 369. Treatment of intact 32P-labeled receptor in cytosol with alkaline phosphatase removes these three phosphates, but it does not remove the phosphate from the DNA-binding-BuGR-reactive fragment and it does not affect the ability of the transformed receptor to bind to DNA-cellulose.

Evidence that the 90-kilodalton heat shock protein is associated with tubulin-containing complexes in L cell cytosol and in intact PtK cells

It has been established that the 90-kilodalton murine heat shock protein, hsp90, is associated with the untransformed, non-DNA-binding form of the glucocorticoid receptor in L cell cytosol. In this work, we show that incubation of L cell cytosol with Affi-Gel-coupled monoclonal antibodies directed against either alpha-tubulin alone or both alpha- and beta-tubulin results in the immune-specific adsorption of hsp90 identified by Western blotting with the AC88 monoclonal antibody. Similarly, the AC88 antibody, which is specific for hsp90, causes the immune-specific isolation of both alpha- and beta-tubulin from hypotonic cytosol. The distribution of hsp90 in cultured Potorous tridactylis kidney cells was examined by indirect immunofluorescence using the AC88 monoclonal as primary antibody. In interphase cells, AC88-dependent fluorescence was distributed like antitubulin antibody-dependent fluorescence in a fibrillar array located in the cytoplasm and around the periphery of the nucleus. In cells undergoing mitosis, AC88 fluorescence was located in the mitotic spindle. These observations suggest that a significant portion of hsp90 is associated with a tubulin-containing complex both in a hypotonic cytosol preparation from mouse fibroblasts and in intact marsupial kidney epithelial cells. The distribution of AC88 fluorescence in interphase Potorous tridactylis kidney cells is similar to the distribution of glucocorticoid receptor demonstrated by Wikstrom, A. C., Bakke, O., Okret, S., Bronnegard, M., and Gustafsson, J. A in rat hepatoma and human uterine cells.

Hydrogen peroxide stabilizes the steroid-binding state of rat liver glucocorticoid receptors by promoting disulfide bond formation

Hydrogen peroxide and diamide inactivate the steroid-binding capacity of unoccupied glucocorticoid receptors in rat liver cytosol at 0 degrees C, and steroid-binding capacity is reactivated with dithiothreitol. Treatment of cytosol with peroxide or sodium molybdate, but not diamide, inhibits the irreversible inactivation (i.e., inactivation not reversed by dithiothreitol) of steroid-binding capacity that occurs when cytosol is incubated at 25 degrees C. Pretreatment of cytosol with the thiol derivatizing agent methyl methanethiosulfonate at 0 degrees C prevents the ability of peroxide, but not molybdate, to stabilize binding capacity at 25 degrees C. As derivatization of thiol groups prevents peroxide stabilization of steroid-binding capacity and as treatment with dithiothreitol reverses the effect, we propose that peroxide acts by promoting the formation of new disulfide linkages. The receptor in our rat liver cytosol preparations is present as three major degradation products of Mr 40,000, 52,000, and 72,000 in addition to the Mr 94,000 intact receptor. Like the intact receptor, these three forms exist in the presence of molybdate as an 8-9S complex, they bind glucocorticoid in a specific manner, and they copurify with the intact Mr 94,000 receptor on sequential phosphocellulose and DNA-cellulose chromatography. Despite the existence of receptor cleavage products, it is clear that peroxide does not stabilize steroid-binding capacity by inhibiting receptor cleavage.

Relationship between glucocorticoid receptor steroid-binding capacity and association of the Mr 90,000 heat shock protein with the unliganded receptor

Treatment of rat liver cytosol with hydrogen peroxide (H2O2) or sodium molybdate (MoO4(2-)) inhibits thermal inactivation of glucocorticoid receptor steroid-binding capacity at 25 degrees C. Dithiothreitol (DTT) prevents the stabilization of receptors by H2O2. Heating (25 degrees C) of immune pellets formed by immunoadsorption of L-cell murine glucocorticoid receptor complexes to protein-A-Sepharose with an anti-receptor monoclonal antibody (BuGR2) results in dissociation of the M 90,000 heat shock protein (hsp90) from the steroid binding protein. Such thermal-induced dissociation of hsp90 is inhibited by H2O2. Pretreatment of immunoadsorbed receptor complexes with the thiol derivatizing agent, methyl methanethiosulfonate (MMTS) prevents the ability of H2O2 to stabilize the hsp90-receptor interaction. These data suggest a role for hsp90 in maintaining an active steroid-binding conformation of the glucocorticoid receptor.

Glucocorticoid receptor phosphorylation, transformation, and DNA binding

Glucocorticoid receptors were isolated by immunoadsorption from cytosol of L cells that were cultured for 18 h in the presence of [32P]orthophosphate, and the phosphorylation state of the receptor was examined before and after transformation to the DNA-binding state. Temperature-mediated transformation of the glucocorticoid receptor under cell-free conditions results in no change in receptor size or degree of phosphorylation. When cytosol containing transformed receptors is incubated with DNA-cellulose, 30-50% of the receptors are able to bind to DNA and the remainder do not bind to DNA. Both the heated receptors that bind to DNA and the receptors that do not bind to DNA are phosphorylated to the same degree. When intact cells containing 32P-labeled receptors are incubated for 2 h at 0 degree C with triamcinolone acetonide and then for 20 min at 37 degrees C in the presence of the hormone, 80% of the receptor becomes tightly associated with the nucleus in a manner that is both temperature-dependent and ligand-dependent. Approximately 80% of the nuclear-bound receptor is extracted with 0.4 M NaCl. Both the cytosolic receptor from cells incubated at 0 degree C and the salt-extracted nuclear receptor from cells incubated at 37 degrees C have been resolved by immunoadsorption to protein A-Sepharose with the BuGR1 monoclonal antibody and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, followed by immunoblotting and autoradiography of the immunoblots. In addition, direct measurements of the amounts of 32P contained per unit of receptor protein were performed for receptors transformed both in the intact cell and in cell-free lysates. The results demonstrate that the untransformed receptor and the nuclear-bound transformed receptor are labeled with 32P to the same extent.

Demonstration that the 90-kilodalton heat shock protein is bound to the glucocorticoid receptor in its 9S nondeoxynucleic acid binding form

The 9S molybdate-stabilized form of the glucocorticoid receptor of mouse L cell lysates was immunoadsorbed to protein-A-Sepharose with antiserum directed against the 89-kilodalton chicken heat shock protein (anti-hsp89). In order to achieve this, "free" (nonreceptor associated) hsp90 was first separated from the molybdate-stabilized 9S receptor by sucrose gradient sedimentation. Incubation of the 9S [3H]triamcinolone acetonide-labeled receptor peak with anti-hsp89 results in the immune-specific adsorption of 20% of the specifically bound radioactivity and adsorption of the 100-kilodalton receptor protein, as detected by Western-blotting, using the GR49 antireceptor monoclonal antibody as probe. These observations provide the only direct proof that hsp90 is a component of the 9S form of a steroid receptor.

Relationship of the 90-kDa murine heat shock protein to the untransformed and transformed states of the L cell glucocorticoid receptor

Incubation of molybdate-stabilized L cell cytosol with a monoclonal antibody directed against the 100-kDa glucocorticoid-binding protein causes the immune-specific adsorption to protein A-Sepharose of both the 100-kDa glucocorticoid receptor and the 90-kDa murine heat shock protein (hsp90) (Sanchez, E. R., Toft, D. O., Schlesinger, M. J., and Pratt, W. B. (1985) J. Biol. Chem. 260, 12398-12401). When the glucocorticoid receptor in cytosol is transformed to the DNA-binding state, hsp90 dissociates. In this paper, we show that temperature-mediated dissociation of hsp90 from the receptor is a hormone-dependent event in the same manner as temperature-mediated transformation to the DNA-binding state. In contrast to temperature-mediated transformation, ammonium sulfate causes both dissociation of hsp90 from the receptor and conversion of the receptor to the DNA-binding form in a manner that does not require the presence of steroid. The untransformed form of the glucocorticoid receptor and the strongly negatively charged hsp90 protein behave similarly on DEAE-cellulose chromatography, suggesting that the hsp90 component may contribute significantly to the net negative charge behavior of the non-DNA-binding form of the 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.

Glucocorticoid receptor phosphorylation in mouse L-cells

This paper summarizes our observations on the phosphorylation state of untransformed and transformed glucocorticoid receptors isolated from 32P-labeled L-cells. The 300-350-kDa 9S untransformed murine glucocorticoid receptor complex is composed of a 100-kDa steroid-binding phosphoprotein and one or possibly two units of the 90-kDa heat shock protein (hsp90), which is also a phosphoprotein. Transformation of this complex to the 4S DNA-binding state is accompanied by dissociation of hsp90. When receptors in cytosol are transformed by heating at 25 degrees C, there is no gross change in the degree of phosphorylation of the steroid-binding protein. Both receptors that are bound to DNA after transformation under cell-free conditions and receptors that are located in the nucleus of cells incubated at 37 degrees C in the presence of glucocorticoid are labeled with 32P. The results of experiments in which the 32P-labeled receptor was submitted to limited proteolysis suggest that the 16-kDa DNA-binding domain is phosphorylated and that the 28-kDa steroid-binding domain is not.

Phosphorylation of L-cell glucocorticoid receptors in immune complexes: evidence that the receptor is not a protein kinase

Two phosphoproteins are absorbed to protein A-Sepharose when cytosol from 32P-labeled L-cells is incubated with a monoclonal antibody against the glucocorticoid receptor: one is a 98K phosphoprotein that contains the steroid binding site, and the other is a 90K non-steroid-binding phosphoprotein that is associated with the molybdate-stabilized receptor [Housley, P. R., Sanchez, E. R., Westphal, H. M., Beato, M., & Pratt, W. B. (1985) J. Biol. Chem. 260, 13810-13817]. In this paper we have incubated L-cell cytosol with rabbit antiserum against the mouse glucocorticoid receptor and show that incubation of protein A-Sepharose-bound immune complexes with [gamma-32P]ATP and Mg2+ results in phosphorylation of the 98K steroid-binding protein but not of the 90K receptor-associated protein. Phosphorylation occurs regardless of whether the receptor is unoccupied or is present as the untransformed or transformed steroid-receptor complex. No phosphorylation occurs in the presence of Ca2+ instead of Mg2+. If protein A-Sepharose-bound immune complexes prepared with a monoclonal antibody against the receptor are incubated with [gamma-32P]ATP and Mg2+, neither protein is phosphorylated. If the protein A-Sepharose pellet is obtained from molybdate-stabilized cytosol that has been incubated both with monoclonal antibody to provide the 98K receptor and its 90K associated protein and with preimmune rabbit serum, which causes the nonspecific adsorption of an L-cell protein kinase, then incubation with [gamma-32P]ATP and Mg2+ causes receptor phosphorylation.(ABSTRACT TRUNCATED AT 250 WORDS)

The molybdate-stabilized glucocorticoid binding complex of L-cells contains a 98-100 kdalton steroid binding phosphoprotein and a 90 kdalton nonsteroid-binding phosphoprotein that is part of the murine heat-shock complex

This paper summarizes our work performed with glucocorticoid-binding complexes in molybdate-stabilized cytosol prepared from 32P-labeled L-cells. In our early work, we showed that cytosol prepared from 32P-labeled L-cells contains two phosphoproteins (a 90 and a 98-100 kdalton protein) that elute from an affinity resin of deoxycorticosterone agarose in a manner consistent with the predicted behavior of the glucocorticoid receptor. Both phosphoproteins are immunoadsorbed onto protein-A-Sepharose from molybdate-stabilized cytosol incubated with a monoclonal antibody against the receptor. The 98-100 kdalton phosphoprotein binds steroid and the 90 kdalton phosphoprotein is a structurally different, nonsteroid-binding protein that is bound to the untransformed, molybdate-stabilized glucocorticoid receptor. The 90 kdalton protein reacts on Western blots with a monoclonal antibody raised against a 90 kdalton protein from the water mold Achlya ambisexualis. This antibody recognizes an epitope that is conserved in 90 kdalton phosphoproteins from rodent and human cells, and it reacts with the 90 kdalton phosphoprotein that copurifies with the molybdate-stabilized, untransformed chick oviduct progesterone receptor. The 90 kdalton nonsteroid-binding phosphoprotein is an abundant cytosolic protein that dissociates from the glucocorticoid receptor when it is transformed, and unlike the steroid-binding protein, it does not bind to DNA. The 90 kdalton phosphoprotein determines the acidic behavior of the untransformed glucocorticoid receptor on DEAE-cellulose. This abundant cytosolic 90 kdalton phosphoprotein reacts with rabbit antiserum raised against the gel purified 89 kdalton chicken heat-shock protein (hsp89). This antiserum recognizes 90 kdalton heat-shock proteins in human, rodent, frog and Drosophila cells. Immunoadsorption of molybdate-stabilized cytosol with antibody directed against the 98-100 kdalton steroid receptor results in the immune-specific adsorption of a 90 kdalton phosphoprotein that reacts with anti-hsp89 antibody on Western blots. These observations suggest that, like the transforming proteins from several avian sarcoma viruses, the untransformed glucocorticoid receptor exists in a complex with the 90 kdalton heat-shock protein.

The molybdate-stabilized L-cell glucocorticoid receptor isolated by affinity chromatography or with a monoclonal antibody is associated with a 90-92-kDa nonsteroid-binding phosphoprotein

We have previously reported that molybdate-stabilized cytosol prepared from 32P-labeled L-cells contains two phosphoproteins (a 90-92- and a 98-100-kDa protein) that elute from an affinity resin of deoxycorticosterone-derivatized agarose in a manner consistent with the predicted behavior of the glucocorticoid receptor (Housley, P. R., and Pratt, W. B. (1983) J. Biol. Chem. 258, 4630-4635). In the present work we report that both the 90-92- and 98-100-kDa 32P-labeled proteins are also extracted from molybdate-stabilized cytosol by incubation with a monoclonal antibody and protein A-Sepharose. Only the 98-100-kDa protein is specifically labeled when either L-cell cytosol or L-cell cytosol proteins bound to the affinity resin are labeled with the glucocorticoid binding site-specific affinity ligand [3H]dexamethasone 21-mesylate. The 98-100-kDa protein labeled with [3H]dexamethasone mesylate is adsorbed to protein A-Sepharose in an immune-specific manner after reaction with the monoclonal antibody. Sodium dodecyl sulfate-polyacrylamide gel analysis of the protein A-Sepharose-bound material resulting from incubating the monoclonal antibody with a mixture of 32P-labeled cytosol and [3H]dexamethasone mesylate-labeled cytosol demonstrates identity of the 98-100-kDa [3H]dexamethasone mesylate-labeled band with the 98-100-kDa 32P-labeled band and clear separation from the nonsteroid-binding 90-92-kDa phosphoprotein. The results of immunoblot experiments demonstrate that the 90-92-kDa protein is structurally distinct from the 98-100-kDa steroid-binding protein. As the 90-92-kDa nonsteroid-binding phosphoprotein co-purified with the 98-100-kDa uncleaved form of the glucocorticoid receptor by two independent methods, one of which is based on recognizing a steroid-binding site and the other of which is based on recognizing an antibody binding site, we propose that the 90-92-kDa phosphoprotein is a component of the molybdate-stabilized, untransformed glucocorticoid-receptor complex in L-cell cytosol.

Evidence that the 90-kDa phosphoprotein associated with the untransformed L-cell glucocorticoid receptor is a murine heat shock protein

Two phosphoproteins are adsorbed to protein-A-Sepharose when cytosol from 32P-labeled L-cells is incubated with a monoclonal antibody against the glucocorticoid receptor: one is a 98-100-kDa phosphoprotein that contains the steroid-binding site and the other is a 90-kDa nonsteroid-binding phosphoprotein that is associated with the untransformed, molybdate-stabilized receptor (Housley, P. R., Sanchez, E. R., Westphal, H.M., Beato, M., and Pratt, W.B. (1985) J. Biol. Chem. 260, in press). In this paper we show that the 90-kDa receptor-associated phosphoprotein is an abundant cytosolic protein that reacts with a monoclonal antibody that recognizes the 90-kDa phosphoprotein that binds steroid receptors in the chicken oviduct. The 90-kDa protein immunoadsorbed from L-cell cytosol with this antibody reacts on Western blots with rabbit antiserum prepared against the 89-kDa chicken heat shock protein. Immunoadsorption of molybdate-stabilized cytosol by antibodies against the glucocorticoid receptor results in the presence of a 90-kDa protein that interacts on Western blots with the antiserum against the chicken heat shock protein. The association between the 90-kDa protein and the receptor is only seen by this technique when molybdate is present to stabilize the complex; and when steroid-bound receptors are incubated at 25 degrees C to transform them to the DNA-binding state, the 90-kDa protein dissociates. These observations are consistent with the proposal that the untransformed glucocorticoid receptor in L-cells exists in a complex with the murine 90-kDa heat shock protein.

A new t-complex embryonic lethal (tcl0) has arisen in the Thp chromosome of the mouse and is allelic to t0

Complement testing of aThpline revealed a failure of survival ofThp/t0embryos. The genetic factor responsible for this lethality maps between Brachyury (T) and tufted (tf) on the murine seventeenth chromosome. This lethal factor permits recombination betweenTandtfand does not affect the transmission of its seventeenth chromosome. Its effect upon embryonic development is similar to that of thet0haplotype. It would appear to represent a point mutation of a single gene,t-complex lethal zero(tcl0).

Treatment of gastric pyrosis with almagate in patients with and without endoscopically demonstrable duodenal ulcer. A multicentre clinical trial

An open multicentre trial of a new clinical antacid, almagate (hydrated aluminium-magnesium hydroxycarbonate, Al2Mg6(OH)14(CO3)2 X 4H2O, Almax) has been made in 169 patients suffering from gastric pyrosis (heartburn). Clinical and endoscopical exploration revealed that 104 of the patients had an active duodenal ulcer and 60 of these (group II) were treated with antisecretory drugs (cimetidine or ranitidine) plus Almax and 44 (group III) with Almax alone. Endoscopic exploration in the remaining 65 patients (group I) failed to reveal the presence of an ulcer and they were also treated with Almax alone. In all groups Almax proved to be very effective and the majority of patients were symptom free by the end of the two week trial. 79.5% of the ulcer patients in group III required doses of 6-8 g/d whereas only 21.7% of those in group II with concomitant treatment with antisecretory drugs took more than 4 g/d. The nonulcer patients of group I also used lower doses and only 29.3% needed to reach 6-8 g/d. There was a significant increase in daily bowel movements in all groups which was considered to be advantageous by most patients. Overall tolerance was excellent and side effects (diarrhoea 7 cases, nauseas 5 cases and constipation 1 case) were few and transient and 84.2% of the patients expressed a clear preference for Almax over their previous antacid treatment.