scholarly journals In Vivo Interaction of Steroid Receptor Coactivator (SRC)-1 and the Activation Function-2 Domain of the Thyroid Hormone Receptor (TR) β in TRβ E457A Knock-In and SRC-1 Knockout mice

Endocrinology ◽  
2009 ◽  
Vol 150 (8) ◽  
pp. 3927-3934 ◽  
Author(s):  
Manuela Alonso ◽  
Charles Goodwin ◽  
XiaoHui Liao ◽  
Tania Ortiga-Carvalho ◽  
Danielle S. Machado ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Hormone Receptor ◽  
Steroid Receptor ◽  
Activation Function ◽  
Steroid Receptor Coactivator ◽  
Pituitary Thyroid Axis ◽  
Serum T4 ◽  
Thyroid Axis

The activation function-2 (AF-2) domain of the thyroid hormone (TH) receptor (TR)-β is a TH-dependent binding site for nuclear coactivators (NCoA), which modulate TH-dependent gene transcription. In contrast, the putative AF-1 domain is a TH-independent region interacting with NCoA. We determined the specificity of the AF-2 domain and NCoA interaction by evaluating thyroid function in mice with combined disruption of the AF-2 domain in TRβ, due to a point mutation (E457A), and deletion of one of the NCoAs, steroid receptor coactivator (SRC)-1. The E457A mutation was chosen because it abolishes NCoA recruitment in vitro while preserving normal TH binding and corepressor interactions resulting in resistance to TH. At baseline, disruption of SRC-1 in the homozygous knock-in (TRβE457A/E457A) mice worsened the degree of resistance to TH, resulting in increased serum T4 and TSH. During TH deprivation, disruption of AF-2 and SRC-1 resulted in a TSH rise 50% of what was seen when AF-2 alone was removed, suggesting that SRC-1 was interacting outside of the AF-2 domain. Therefore, 1) during TH deprivation, SRC-1 is necessary for activating the hypothalamic-pituitary-thyroid axis; 2) ligand-dependent repression of TSH requires an intact AF-2; and 3) SRC-1 may interact with the another region of the TRβ or the TRα to regulate TH action in the pituitary. This report demonstrates the dual interaction of NCoA in vivo: the TH-independent up-regulation possibly through another domain and TH-dependent down-regulation through the AF-2 domain.

scholarly journals The Interaction of TRβ1-N Terminus with Steroid Receptor Coactivator-1 (SRC-1) Serves a Full Transcriptional Activation Function of SRC-1

Endocrinology ◽  
2006 ◽  
Vol 147 (3) ◽  
pp. 1452-1457 ◽  
Author(s):  
Toshiharu Iwasaki ◽  
Akira Takeshita ◽  
Wataru Miyazaki ◽  
William W. Chin ◽  
Noriyuki Koibuchi
Keyword(s):  
Thyroid Hormone ◽  
Nuclear Receptor ◽  
Thyroid Hormone Receptor ◽  
Steroid Receptor ◽  
Activation Function ◽  
Binding Domain ◽  
Expression Vectors ◽  
Response Element ◽  
Steroid Receptor Coactivator ◽  
N Terminus

Steroid receptor coactivator-1 (SRC-1) plays a crucial role in nuclear receptor-mediated transcription including thyroid hormone receptor (TR)-dependent gene expression. Interaction of the TR-ligand binding domain and SRC-1 through LXXLL motifs is required for this action. However, potential interactions between the TRβ1-N terminus (N) and SRC-1 have not been explored and thus are examined in this manuscript. Far-Western studies showed that protein construct containing TRβ1-N + DNA binding domain (DBD) bound to nuclear receptor binding domain (NBD)-1 (amino acid residue, aa 595–780) of SRC-1 without ligand. Mammalian two-hybrid studies showed that NBD-1, as well as SRC-1 (aa 595-1440), bound to TRβ1-N+DBD in the absence of ligand in CV-1 cells. However, NBD-2 (aa 1237–1440) did not bind to this protein. Glutathione-S-transferase pull-down studies showed that TRβ1-N (aa 1–105) bound to the broad region of SRC-1-C terminus. Expression vectors encoding a series of truncations and/or point mutations of TRβ1 were used in transient transfection-based reporter assays in CV-1 cells. N-terminal truncated TRβ1 (ΔN-TRβ1) showed lower activity than that of wild-type in both artificial F2-thyroid hormone response element and native malic enzyme response element. These results suggest that there is the interaction between N terminus of TRβ1 and SRC-1, which may serve a full activation of SRC-1, together with activation function-2 on TRβ1-mediated transcription.

scholarly journals Modulation by Steroid Receptor Coactivator-1 of Target-Tissue Responsiveness in Resistance to Thyroid Hormone

Endocrinology ◽  
2003 ◽  
Vol 144 (9) ◽  
pp. 4144-4153 ◽  
Author(s):  
Yuji Kamiya ◽  
Xiao-Yong Zhang ◽  
Hao Ying ◽  
Yusuhito Kato ◽  
Mark C. Willingham ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Target Genes ◽  
Thyroid Hormone Receptor ◽  
Expression Patterns ◽  
Steroid Receptor ◽  
Target Tissue ◽  
Dependent Manner ◽  
Resistance To Thyroid Hormone ◽  
Steroid Receptor Coactivator

Abstract Mutations in the thyroid hormone receptor-β gene (TRβ) cause resistance to thyroid hormone. How the action of mutant thyroid hormone nuclear receptors (TRs) is regulated in vivo is not clear. We examined the effect of a TR coactivator, steroid receptor coactivator-1 (SRC-1), on target-tissue responsiveness by using a mouse model of resistance to thyroid hormone, TRβPV knockin mice, in the SRC-1 null background. Lack of SRC-1 intensified the dysfunction of the pituitary-thyroid axis and impaired growth in TRβPV/+ mice but not in TRβPV/PV mice. In TRβPV/PV mice, however, lack of SRC-1 intensified the pathological progression of thyroid follicular cells to papillary hyperplasia, reminiscent of papillary neoplasia. In contrast, lack of SRC-1 did not affect responsiveness in the liver in regulating serum cholesterol in either TRβPV/+ or TRβPV/PV mice. Lack of SRC-1 led to changes in the abnormal expression patterns of several T3 target genes in the pituitary and liver. Thus, the present studies show that a coactivator such as SRC-1 could modulate the in vivo action of TRβ mutants in a tissue-dependent manner.

scholarly journals Dual Functions of the Steroid Hormone Receptor Coactivator 3 in Modulating Resistance to Thyroid Hormone

2005 ◽  
Vol 25 (17) ◽  
pp. 7687-7695 ◽  
Author(s):  
Hao Ying ◽  
Fumihiko Furuya ◽  
Mark C. Willingham ◽  
Jianming Xu ◽  
Bert W. O'Malley ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Hormone Receptor ◽  
Thyroid Hormone Receptor ◽  
Steroid Hormone ◽  
Serum Insulin ◽  
Steroid Hormone Receptor ◽  
Resistance To Thyroid Hormone ◽  
Pituitary Thyroid Axis ◽  
Thyroid Axis

ABSTRACT Mutations of the thyroid hormone receptor β (TRβ) gene cause resistance to thyroid hormone (RTH). RTH is characterized by increased serum thyroid hormone associated with nonsuppressible thyroid-stimulating hormone (TSH) and impaired growth. It is unclear how the actions of TRβ mutants are modulated in vivo to affect the manifestation of RTH. Using a mouse model of RTH that harbors a knockin mutation of the TRβ gene (TRβPV mouse), we investigated the effect of the steroid hormone receptor coactivator 3 (SRC-3) on RTH. In TRβPV mice deficient in SRC-3, dysfunction of the pituitary-thyroid axis and hypercholesterolemia was lessened, but growth impairment of RTH was worsened. The lessened dysfunction of the pituitary-thyroid axis was attributed to a significant decrease in growth of the thyroid and pituitary. Serum insulin-like growth factor 1 (IGF-1) was further reduced in TRβPV mice deficient in SRC-3. This effect led to reduced signaling of the IGF-1/phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway that is known to mediate cell growth and proliferation. Thus, SRC-3 modulates RTH by at least two mechanisms, one via its role as a receptor coregulator and the other via its growth regulatory role through the IGF-1/PI3K/AKT/mTOR signaling.

scholarly journals The TRH Gene Is Regulated by Thyroid Hormone at the Level of Transcription in Vivo

2010 ◽  
Vol 31 (1) ◽  
pp. 136-136
Author(s):  
Michelle L. Sugrue ◽  
Kristen R. Vella ◽  
Crystal Morales ◽  
Marisol E. Lopez ◽  
Anthony N. Hollenberg
Keyword(s):  
Thyroid Hormone ◽  
Genomic Region ◽  
Model System ◽  
Model Systems ◽  
In Vivo Model ◽  
Pituitary Thyroid Axis ◽  
Thyroid Axis ◽  
Normal Production

ABSTRACT The expression of the TRH gene in the paraventricular nucleus (PVH) of the hypothalamus is required for the normal production of thyroid hormone (TH) in rodents and humans. In addition, the regulation of TRH mRNA expression by TH, specifically in the PVH, ensures tight control of the set point of the hypothalamic-pituitary-thyroid axis. Although many studies have assumed that the regulation of TRH expression by TH is at the level of transcription, there is little data available to demonstrate this. We used two in vivo model systems to show this. In the first model system, we developed an in situ hybridization (ISH) assay directed against TRH heteronuclear RNA to measure TRH transcription directly in vivo. We show that in the euthyroid state, TRH transcription is present both in the PVH and anterior/lateral hypothalamus. In the hypothyroid state, transcription is activated in the PVH only and can be shut off within 5 h by TH. In the second model system, we employed transgenic mice that express the Cre recombinase under the control of the genomic region containing the TRH gene. Remarkably, TH regulates Cre expression in these mice in the PVH only. Taken together, these data affirm that TH regulates TRH at the level of transcription in the PVH only and that genomic elements surrounding the TRH gene mediate its regulation by T3. Thus, it should be possible to identify the elements within the TRH locus that mediate its regulation by T3 using in vivo approaches.

scholarly journals The role of leptin in the regulation of TSH secretion in the fed state: in vivo and in vitro studies

2002 ◽  
Vol 174 (1) ◽  
pp. 121-125 ◽  
Author(s):  
TM Ortiga-Carvalho ◽  
KJ Oliveira ◽  
BA Soares ◽  
CC Pazos-Moura
Keyword(s):  
Fold Increase ◽  
Adult Rats ◽  
Fed State ◽  
Rat Pituitary ◽  
Pituitary Thyroid Axis ◽  
Tsh Secretion ◽  
Thyroid Axis

Leptin has been shown to stimulate the hypothalamus-pituitary-thyroid axis in fasting rodents; however, its role in thyroid axis regulation under physiological conditions is still under investigation. Here it was investigated in freely fed rats whether leptin modulates thyrotroph function in vivo and whether leptin has direct pituitary effects on TSH release. Since leptin is produced in the pituitary, the possibility was also investigated that leptin may be a local regulator of TSH release. TSH was measured by specific RIA. Freely fed adult rats 2 h after being injected with a single s.c. injection of 8 microg leptin/100 g body weight showed a 2-fold increase in serum TSH (P<0.05). Hemi-pituitary explants incubated with 10(-9) and 10(-7) M leptin for 2 h showed a reduced TSH release of 40 and 50% respectively (P<0.05). Conversely, incubation of hemi-pituitary explants with antiserum against leptin, aiming to block the action of locally produced leptin, resulted in higher TSH release (45%, P<0.05). In conclusion, also in the fed state, leptin has an acute stimulatory effect on TSH release in vivo, acting probably at the hypothalamus. However, the direct pituitary effect of leptin is inhibitory and data also provide evidence that in the rat pituitary leptin may act as an autocrine/paracrine inhibitor of TSH release.

scholarly journals The Thyrotropin-Releasing Hormone Gene Is Regulated by Thyroid Hormone at the Level of Transcription in Vivo

Endocrinology ◽  
2010 ◽  
Vol 151 (2) ◽  
pp. 793-801 ◽  
Author(s):  
Michelle L. Sugrue ◽  
Kristen R. Vella ◽  
Crystal Morales ◽  
Marisol E. Lopez ◽  
Anthony N. Hollenberg
Keyword(s):  
Thyroid Hormone ◽  
Genomic Region ◽  
Model System ◽  
Model Systems ◽  
In Vivo Model ◽  
Pituitary Thyroid Axis ◽  
Thyroid Axis ◽  
Normal Production

The expression of the TRH gene in the paraventricular nucleus (PVH) of the hypothalamus is required for the normal production of thyroid hormone (TH) in rodents and humans. In addition, the regulation of TRH mRNA expression by TH, specifically in the PVH, ensures tight control of the set point of the hypothalamic-pituitary-thyroid axis. Although many studies have assumed that the regulation of TRH expression by TH is at the level of transcription, there is little data available to demonstrate this. We used two in vivo model systems to show this. In the first model system, we developed an in situ hybridization (ISH) assay directed against TRH heteronuclear RNA to measure TRH transcription directly in vivo. We show that in the euthyroid state, TRH transcription is present both in the PVH and anterior/lateral hypothalamus. In the hypothyroid state, transcription is activated in the PVH only and can be shut off within 5 h by TH. In the second model system, we employed transgenic mice that express the Cre recombinase under the control of the genomic region containing the TRH gene. Remarkably, TH regulates Cre expression in these mice in the PVH only. Taken together, these data affirm that TH regulates TRH at the level of transcription in the PVH only and that genomic elements surrounding the TRH gene mediate its regulation by T3. Thus, it should be possible to identify the elements within the TRH locus that mediate its regulation by T3 using in vivo approaches.

Specificity of thyroid hormone receptor subtype and steroid receptor coactivator-1 on thyroid hormone action

2003 ◽  
Vol 284 (1) ◽  
pp. E36-E46 ◽  
Author(s):  
Peter M. Sadow ◽  
Olivier Chassande ◽  
Karine Gauthier ◽  
Jacques Samarut ◽  
Jianming Xu ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Hormone Receptor ◽  
Thyroid Hormone Receptor ◽  
Steroid Receptor ◽  
Receptor Subtype ◽  
Thyroid Function Tests ◽  
Hormone Action ◽  
Peripheral Tissues ◽  
Steroid Receptor Coactivator ◽  
Thyroid Hormone Action

Isoforms of the thyroid hormone receptor ( TR) α and TRβ genes mediate thyroid hormone action. How TR isoforms modulate tissue-specific thyroid hormone (TH) action remains largely unknown. The steroid receptor coactivator-1 (SRC-1) is among a group of transcriptional coactivator proteins that bind to TRs, along with other members of the nuclear receptor superfamily, and modulate the activity of genes regulated by TH. Mice deficient in SRC-1 possess decreased tissue responsiveness to TH and many steroid hormones; however, it is not known whether or not SRC-1-mediated activation of TH-regulated gene transcription in peripheral tissues, such as heart and liver, is TR isoform specific. We have generated mice deficient in TRα and SRC-1, as well as in TRβ and SRC-1, and investigated thyroid function tests and effects of TH deprivation and TH treatment compared with wild-type (WT) mice or those deficient in either TR or SRC-1 alone. The data show that 1) in the absence of TRα or TRβ, SRC-1 is important for normal growth; 2) SRC-1 modulates TRα and TRβ effects on heart rate; 3) two new TRβ-dependent markers of TH action in the liver have been identified, osteopontin (upregulated) and glutathione S-transferase (downregulated); and 4) SRC-1 may mediate the hypersensitivity to TH seen in liver of TRα-deficient mice.

scholarly journals Cold Exposure Increases the Biosynthesis and Proteolytic Processing of Prothyrotropin-Releasing Hormone in the Hypothalamic Paraventricular Nucleus via β-Adrenoreceptors

Endocrinology ◽  
2007 ◽  
Vol 148 (10) ◽  
pp. 4952-4964 ◽  
Author(s):  
Mario Perello ◽  
Ronald C. Stuart ◽  
Charles A. Vaslet ◽  
Eduardo A. Nillni
Keyword(s):  
Paraventricular Nucleus ◽  
Molecular Mechanisms ◽  
Protein Biosynthesis ◽  
Camp Response Element Binding ◽  
Proteolytic Processing ◽  
Hypothalamic Paraventricular Nucleus ◽  
Pituitary Thyroid Axis ◽  
Thyroid Axis

Different physiological conditions affect the biosynthesis and processing of hypophysiotropic proTRH in the hypothalamic paraventricular nucleus, and consequently the output of TRH. Early studies suggest that norepinephrine (NE) mediates the cold-induced activation of the hypothalamic-pituitary-thyroid axis at a central level. However, the specific role of NE on the biosynthesis and processing of proTRH has not been fully investigated. In this study, we found that NE affects gene transcription, protein biosynthesis, and secretion in TRH neurons in vitro; these changes were coupled with an up-regulation of prohormone convertase enzymes (PC) 1/3 and PC2. In vivo, NE is the main mediator of the cold-induced activation of the hypothalamic-pituitary-thyroid axis at the hypothalamic level, in which it potently stimulates the biosynthesis and proteolytic processing of proTRH through a coordinated up-regulation of the PCs. This activation occurs via β-adrenoreceptors and phosphorylated cAMP response element binding signaling. In contrast, α-adrenoreceptors regulate TRH secretion but not proTRH biosynthesis and processing. Therefore, this study provides novel information on the molecular mechanisms of control of hypophysiotropic TRH biosynthesis.

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