8-Bromo-Cyclic AMP Induces Phosphorylation of Two Sites in SRC-1 That Facilitate Ligand-Independent Activation of the Chicken Progesterone Receptor and Are Critical for Functional Cooperation between SRC-1 and CREB Binding Protein

Rowan, Brian G.; Garrison, Nefretiti; Weigel, Nancy L.; O’Malley, Bert W.

doi:10.1128/mcb.20.23.8720-8730.2000

Cited by 229 publications

(179 citation statements)

References 60 publications

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“…In what may be the first evidence of this kind, Rowan et al [35,36] showed that steroid receptor co-activator-1 (SRC-1) contains several consensus sequences for phosphorylation by MAPK (ERK-1 and ERK-2), three of which were phosphorylated in vitro by ERK-2. More importantly, evidence was provided that potentiation of ligand-dependent, progesterone receptor-mediated transcription by EGF treatment of intact cells was mediated by SRC-1.…”

Section: Discussionmentioning

confidence: 99%

Vanadate increases glucocorticoid receptor-mediated gene expression: a novel mechanism for potentiation of a steroid receptor

Calzi

Periyasamy

et al. 2002

The Journal of Steroid Biochemistry and Molecular Biology

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Transition metal oxyanions, such as molybdate, tungstate and vandadate, have been shown to prevent in vitro hormone-induced activation of the glucocorticoid receptor (GR) by blocking dissociation of the GR/heat shock protein heterocomplex. In this work, we report a novel effect of vanadate: in vivo potentiation of GR-mediated gene expression. In cells stably-transfected with complex (mouse mammary tumor virus (MMTV)) or minimal GR-regulated CAT reporters, treatment with 500 M vanadate caused CAT gene expression to dramatically increase, even at saturating concentrations of dexamethasone; while no such effect was seen in response to RU486 antagonist. Similar treatment with molybdate had no effect on GR activity, suggesting that the response to vanadate was not a general property of transition metal oxyanions. Treatment with vanadate after hormone-induced nuclear translocation of the GR also caused potentiation, demonstrating that vanadate was acting on a post-transformation event, perhaps by affecting the transactivation function of DNA-bound GR. Paradoxically, vanadate caused an apparent but temporary "loss" of GR protein immediately after treatment (as measured by loss of reactivity to BuGR2 antibody and of hormone-binding capacity) that returned to normal at approximately 8 h post-treatment, suggesting that potentiation of GR transactivation function (as measured by our CAT assays) was probably occurring during the later stages (8-24 h) of this assay. However, gel shift analyses revealed that vanadate could induce binding of the hormone-free GR to glucocorticoid response element (GRE)-containing oligonucleotides immediately after treatment. Thus, the rapid vanadate-induced "loss" of GR was not due to degradation of GR protein. Yet, vanadate in the absence of hormone had no effect on CAT reporter expression, demonstrating that this form of the GR still requires agonist for its enhanced transcriptional activity. As an indication of the potential mechanism of vanadate action, vanadate was found to dramatically stimulate the mitogen-activated protein kinases, ERK-1 and ERK-2. In addition, vanadate potentiation of GR reporter gene expression was completely blocked by the tyrosine kinase inhibitor herbimycin A. Taken as a whole, our results suggest that vanadate can have dramatic and complex effects on GR structure and function, resulting in hormone-free activation of GR DNA-binding function, as well as alterations to the BuGR2 epitope and hormone-binding domains-while at the same time stimulating tyrosine phosphorylation pathways controlling GR-mediated gene transcription.

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Section: Discussionmentioning

confidence: 99%

Vanadate increases glucocorticoid receptor-mediated gene expression: a novel mechanism for potentiation of a steroid receptor

Calzi

Periyasamy

et al. 2002

The Journal of Steroid Biochemistry and Molecular Biology

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“…Interestingly, there are several coactivators, including the p72/ p68 RNA-binding DEAD box proteins (64,65) and the RNA coactivator, SRA, 2 which have been found to interact selectively with the AF-1 domain of ER␣ but not that of ER␤. Moreover, in addition to p68 being a phosphorylated protein (66), all three of these coactivators are found in complexes with other coactivator molecules, such as CBP, SRC-1, TIF2, and AIB1 (64,65), which are known to be phosphoproteins (34,(67)(68)(69).…”

Section: Discussionmentioning

confidence: 99%

“…Forskolin/IBMX-stimulated ER␣ Activity Is Not Caused by cAMP/PKA-dependent SRC-1 Phosphorylation-It had been demonstrated previously that the chicken PR is not phosphorylated in response to cell treatment with 8-bromo-cAMP, but rather cAMP activation of transcription seems to be mediated by an increase in SRC-1 phosphorylation (34). Moreover, SRC-1 binds to both the EF domain of ER␣ as well as c-Jun (61, 62) and is therefore a good candidate for mediating indirect interactions between these two transcription factors, as described above.…”

Section: Functional Interactions With the Tre-bound Factor(s) Can Be mentioning

confidence: 99%

“…Although an increase in receptor phosphorylation accompanies the cAMP-mediated activation of ER␣ (31,32), there is no increase in chicken PR phosphorylation associated with its activation in cells treated with 8-bromocAMP (33). Rather, cAMP/protein kinase A (PKA) signaling enhances chicken PR-dependent transcription, in part by increasing phosphorylation of a receptor-interacting coactivator, steroid receptor coactivator-1 (SRC-1), and thereby promotes a more stable interaction between this coactivator and p300/ CREB-binding protein (CBP)-associated factor and facilitates functional synergism between SRC-1 and CBP (34). Although it is still unknown how the unliganded ER␣ is activated by cAMP/ PKA, there is evidence that the transcription factor, CREB, can interact functionally with ER␣ and thereby mediate synergism between the 17␤-estradiol (E 2 )-dependent and cAMP-dependent signaling pathways (35).…”

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confidence: 99%

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Mechanistic Differences in the Activation of Estrogen Receptor-α (ERα)- and ERβ-dependent Gene Expression by cAMP Signaling Pathway(s)

Coleman

Dutertre

El-Gharbawy

et al. 2003

Journal of Biological Chemistry

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Although increases in intracellular cAMP can stimulate estrogen receptor-␣ (ER␣) activity in the absence of exogenous hormone, no studies have addressed whether ER␤ can be similarly regulated. In transient transfections, forskolin plus 3-isobutyl-1-methylxanthine (IBMX), which increases intracellular cAMP, stimulated the transcriptional activities of both ER␣ and ER␤. This effect was blocked by the protein kinase A inhibitor H89 (N-(2-(p-bromocinnamylamino)-ethyl)-5-isoquinolinesulfonamide) and was dependent on an estrogen response element. A 12-O-tetradecanoylphorbol-13-acetate response element (TRE) located 5 to the estrogen response element was necessary for cAMP-dependent activation of gene expression by ER␤ but not ER␣, indicating that the former subtype requires a functional interaction with TRE-interacting factor(s) to stimulate transcription. Both p160 and CREB-binding protein coactivators stimulated cAMP-induced ER␣ and ER␤ transcriptional activity. However, mutation of the two cAMP-inducible SRC-1 phosphorylation sites important for cAMP activation of chicken progesterone receptor or all seven known SRC-1 phosphorylation sites did not specifically impair cAMP activation of ER␣. The E/F domains of ER␣ are sufficient for activation by forskolin/IBMX, and this is accompanied by an increase in receptor phosphorylation. In contrast, cAMP signaling reduces the phosphorylation of the corresponding region of ER␤, and this correlates with the lack of forskolin/IBMX stimulated transcriptional activity. Our data suggest that cAMP activation of ER␣ transcriptional activity is associated with receptor instead of SRC-1 phosphorylation. Moreover, differences in the cofactor requirements, domains of ER␣ and ER␤ sufficient for forskolin/IBMX activation, and the effect of cAMP on receptor phosphorylation indicate that this signaling pathway utilizes distinct mechanisms to stimulate ER␣ and ER␤ transcriptional activity.

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“…CBP has been shown in numerous studies to act as a nuclear receptor cofactor. Specifically it has been shown that CBP has a synergistic effect in combination with R5020 on the transcriptional activity of the chicken PR (39). In addition, CBP has been shown previously to associate with the MMTV array upon activation of GR and the induction of transcription at the MMTV promoter (24).…”

Section: Analysis Of Pr Ligand Binding In Cytosolic and Nuclearmentioning

confidence: 99%

Progesterone Receptor Deficient in Chromatin Binding Has an Altered Cellular State

Botos

Xian²,

Smith³

et al. 2004

Journal of Biological Chemistry

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Our previous work has shown that the progesterone receptor (PR) can exist in two distinct functional states in mammary adenocarcinoma cells. The differences in function included the ability to activate a promoter in organized chromatin, sensitivity to ligand, and ligandindependent activation. To determine whether these functional differences were because of altered cellular processing, we carried out biochemical analyses of the functionally distinct PRs. Although the majority of PR is localized to the nucleus, biochemical partitioning resulted in a loosely bound (cytosolic) fraction, and a tightly bound (nuclear) fraction. In the absence of progestins, the functionally distinct PRs differed significantly in partitioning between the two fractions. To characterize these fractions further, we analyzed interactions of unliganded PR with chaperones by coimmunoprecipitation. We determined that PR in the cytosolic fraction associated with hsp90 and p23. In contrast, PR in the nuclear fraction consisted of complexes containing hsp90, p23, and FKBP51 as well as PR that was dimerized and highly phosphorylated. Hormone treatment significantly reduced the formation of all PR-chaperone complexes. The hsp90 inhibitor, geldanamycin, similarly blocked transcriptional activity of both functionally distinct receptors. However, the two forms of the PR differed in their ability to associate with the mouse mammary tumor virus promoter in organized chromatin. These findings provide new information about the composition and distribution of mature progesterone receptor complexes in mammary adenocarcinoma cells, and suggest that differences in receptor subcellular distribution have a significant impact on their function. These findings also reveal that transiently expressed steroid receptors may not always be processed like their endogenous counterparts.Progesterone receptor (PR) 1 functions in the development of lobular alveolar structures in the normal mammary gland (1, 2). Data from in vitro studies using cultured breast cancer cells suggest that PR exerts its effects on mammary epithelium by regulating cell cycle progression. PR positive breast cancer cells exhibit a biphasic response to progestins, initial cell division followed by long term G 1 phase growth arrest (3, 4). In mammary adenocarcinoma, PR-mediated growth regulation is frequently lost. However, loss of function through receptor deletion or receptor mutation occurs only in a subset of tumors (5). Therefore, in the majority of cases, other mechanisms must be involved in loss of PR function. A better understanding of the mechanisms by which PR function can be modulated would be beneficial to developing therapy for tumors in which PR function has been lost or altered.In vivo, steroid receptors must interact with transcriptionally inactive promoters having complex chromatin structure. Accordingly, their transcriptional activity is dependent upon a variety of proteins that modify chromatin structure, such as ATP-dependent chromatin remodelers, histone acetyltransferases, and...

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8-Bromo-Cyclic AMP Induces Phosphorylation of Two Sites in SRC-1 That Facilitate Ligand-Independent Activation of the Chicken Progesterone Receptor and Are Critical for Functional Cooperation between SRC-1 and CREB Binding Protein

Cited by 229 publications

References 60 publications

Vanadate increases glucocorticoid receptor-mediated gene expression: a novel mechanism for potentiation of a steroid receptor

Vanadate increases glucocorticoid receptor-mediated gene expression: a novel mechanism for potentiation of a steroid receptor

Mechanistic Differences in the Activation of Estrogen Receptor-α (ERα)- and ERβ-dependent Gene Expression by cAMP Signaling Pathway(s)

Progesterone Receptor Deficient in Chromatin Binding Has an Altered Cellular State

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