Interactions of exogenous endocrine active substances with nuclear receptors

2003 ◽  
Vol 75 (11-12) ◽  
pp. 1797-1817 ◽  
Author(s):  
J. A. Katzenellenbogen ◽  
R. Muthyala
Keyword(s):  
Ligand Binding ◽  
Nuclear Receptors ◽  
Endocrine Disruption ◽  
Transcriptional Activation ◽  
Progesterone Receptors ◽  
Binding Pocket ◽  
Receptor Interaction ◽  
Hormone Production ◽  
Binding Domains ◽  
Equilibrium Dissociation

Nuclear receptors function as ligand-regulated transcription factors and modulate the expression of sets of genes in response to varying concentrations of ligands. The ligand modulators can be endogenous metabolites that function as hormones, or they can be exogenous substances, such as pharmaceutical agents or environmental substances of natural or man-made origin, which in some cases can cause endocrine disruption. Ligands modulate nuclear receptor activity by binding to their ligand-binding domains and stabilizing conformations that lead either to transcriptional activation or repression. The ligand-binding pocket is somewhat flexible, and binding affinities can be measured over a 10-million-fold range (i.e., with equilibrium dissociation constant values ranging from ca. 0.01 nM to 100 μM). Thus, it is not surprising that by binding a large variety of structures, some nuclear receptors can appear to be promiscuous; however, when affinity is considered, the binding patterns are more restricted. The spectrum of ligands that bind to the estrogen receptor has been most thoroughly investigated. Those from natural sources include natural products in food, such as soy isoflavones and whole grain lignans, as well as microbial products and components from wood. Aside from pharmaceuticals, man-made estrogen ligands can be found in industrial products, such as alkyl phenols from nonionic detergents, bisphenols from plastics, indicator dye impurities, polymer chemicals, and chlorinated aromatics and pesticides. Exogenous ligands are also known for the androgen and progesterone receptors. While it is possible that endocrine disruption can result from exogenous chemicals acting directly as ligands for the nuclear receptors, endocrine disruption needs to be considered in the broader context; thus, compounds also need to be assessed for their effects at other levels, such as on endogenous hormone production, transport, metabolism, and clearance, and at points in signal transduction cascades that are beyond the ligand-receptor interaction.

Expression of SMRTβ promotes ligand-induced activation of mutated and wild-type retinoid receptors

Blood ◽  
2004 ◽  
Vol 104 (13) ◽  
pp. 4226-4235 ◽  
Author(s):  
Sylvie Côté ◽  
Suzan McNamara ◽  
Daria Brambilla ◽  
Andrea Bianchini ◽  
Giovanni Rizzo ◽  
...  
Keyword(s):  
Ligand Binding ◽  
Nuclear Receptors ◽  
Transcriptional Activation ◽  
Leukemic Cell ◽  
Wild Type ◽  
Specific Expression ◽  
Retinoid Receptors ◽  
Leukemic Cell Lines ◽  
All Trans Retinoic Acid ◽  
New Evidence

Abstract Nuclear receptors are ligand-modulated transcription factors regulated by interactions with corepressors and coactivators, whose functions are not fully understood. Acute promyelocytic leukemia (APL) is characterized by a translocation, t(15;17), that produces a PML/RARα fusion oncoprotein, whose abnormal transcriptional function is successfully targeted by pharmacologic levels of all-trans-retinoic acid (ATRA). Mutations in the ligand-binding domain of PML/RARα that confer resistance to ATRA have been studied by expression in nonhematopoietic cells, such as Cos-1. Here, we show that ATRA binding and transcriptional activation by the same PML/RARα mutant differ markedly between nonhematopoietic and leukemic cell lines. Differential expression of the corepressor isoform silencing mediator for retinoid and thyroid receptors β (SMRTβ) correlates with increased ligand binding and transcription by the mutant PML/RARα. Transient and stable overexpression of SMRTβ in hematopoietic cells that only express SMRTα increased ATRA binding, ligand-induced transcription, and ATRA-induced cell differentiation. This effect may not be limited to abnormal nuclear receptors, because overexpression of SMRTβ increased ATRA-induced binding and transcriptional activation of wild-type receptors PML/RARα and RARα. Our results suggest a novel role for the SMRTβ isoform whereby its cell-specific expression may influence the binding and transcriptional capacities of nuclear receptors, thus providing new evidence of distinct functions of corepressor isoforms and adding complexity to transcriptional regulation.

scholarly journals Ligand-binding domains of nuclear receptors facilitate tight control of split CRISPR activity

2016 ◽  
Vol 7 (1) ◽  
Author(s):  
Duy P. Nguyen ◽  
Yuichiro Miyaoka ◽  
Luke A. Gilbert ◽  
Steven J. Mayerl ◽  
Brian H. Lee ◽  
...  
Keyword(s):  
Ligand Binding ◽  
Nuclear Receptors ◽  
Tight Control ◽  
Binding Domains

scholarly journals SUN-LB138 Dynamic Structural Model of Testosterone Entry Into the Unliganded Androgen Receptor

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Irina Krylova ◽  
Fred J Schaufele ◽  
Christophe Guilbert
Keyword(s):  
Amino Acids ◽  
Androgen Receptor ◽  
Ligand Binding ◽  
Nuclear Receptors ◽  
Nuclear Receptor ◽  
Binding Pocket ◽  
Binding Domain ◽  
Receptor Ligand ◽  
Ligand Binding Pocket ◽  
Crystallographic Structures

Abstract Background: Crystallographic structures of nuclear receptor ligand binding domains provide a static model of a receptor stably wrapped around an internalized ligand. Understanding the dynamics of a receptor at different stages of ligand binding has been hampered by the paucity of crystal structures for unliganded nuclear receptors. Molecular dynamic models have been constructed for some nuclear receptors to fill that void. Methods: The molecular simulation docking program MORDOR (MOlecular Recognition with a Driven dynamics OptimizeR)(1) was used to study the structural dynamics of the androgen receptor ligand binding domain (AR LBD) modeled from the static structure of the AR LBD bound to testosterone (T) (PDB ID: 2AM9). The goals of the study were to understand a) the dynamic interaction of the T in its binding pocket, b) AR LBD structural flexibilities that permit T entry/exit from the binding pocket and c) a model of the unliganded AR LBD. Results: Modeling AR LBD structure flexibility over time revealed possible alternative dynamic structures, including those without ligand, overlaid against the canonical nuclear receptor structure. The model dynamically tracks the structural changes as a ligand enters into the ligand binding domain and nestles into the ligand binding pocket. The model predicted the appearance of alpha helices within the AR LBD that transiently fold/unfold during the ligand entry phases. Once in the pocket, the ligand itself remains very dynamic in a still flexible pocket. The model predicted also AR LBD amino acids that sequentially interact with the ligand during its dynamic entry into the AR LBD. Intriguingly, those AR amino acids include those mutated in castration-resistant prostate tumors that continue to grow during androgen suppression therapy. Functional studies showed those mutant ARs had a primary consequence of enhancing response to lower level T, and other androgens, consistent with their role in creating a higher affinity AR that can scavenge low-level androgens in an androgen-suppressed patient. Conclusions: The molecular model of T binding to the AR LBD suggests a degree of structural dynamism not evident in the crystallographic structures commonly associated with nuclear receptors. Some AR mutations activating prostate tumor growth may do so by impacting androgen entry/exit, rather than by altering androgen fit into the ligand binding pocket. Reference: (1) Guilbert C, James TL (2008) J Chem Inf Model. 2008 48(6): 1257-1268. doi: 10.1021/ci8000327

Transcriptional repression by nuclear receptors: mechanisms and role in disease

2000 ◽  
Vol 28 (4) ◽  
pp. 390-396 ◽  
Author(s):  
J. D. Love ◽  
J. T. Gooch ◽  
L. Nagy ◽  
V. K. K. Chatterjee ◽  
J. W. R. Schwabe
Keyword(s):  
Diabetes Mellitus ◽  
Thyroid Hormone ◽  
Ligand Binding ◽  
Nuclear Receptors ◽  
Transcriptional Repression ◽  
Dominant Negative ◽  
Receptor Interaction ◽  
Hormone Resistance ◽  
Thyroid Hormone Resistance ◽  
Repressor Proteins

Co-repressor proteins mediate transcriptional repression by nuclear receptors in the absence of ligand. The identification of a co-repressor-receptor interaction motif, and the finding that compressors and co-activators compete for the same site on the receptor, suggests a simple mechanism for the switch from repression to activation upon ligand binding. Defects in this mechanism result in dominant-negative receptors that repress transcription. Such receptors have been implicated in several clinically important diseases, including thyroid hormone resistance and diabetes mellitus.

scholarly journals Doubling the Size of the Glucocorticoid Receptor Ligand Binding Pocket by Deacylcortivazol

2007 ◽  
Vol 28 (6) ◽  
pp. 1915-1923 ◽  
Author(s):  
Kelly Suino-Powell ◽  
Yong Xu ◽  
Chenghai Zhang ◽  
Yong-guang Tao ◽  
W. David Tolbert ◽  
...  
Keyword(s):  
Glucocorticoid Receptor ◽  
Ligand Binding ◽  
Binding Pocket ◽  
Affinity Binding ◽  
Receptor Ligand ◽  
Ligand Binding Pocket ◽  
Steroid Receptor Coactivator ◽  
High Affinity ◽  
Binding Domains ◽  
Lxxll Motif

ABSTRACT A common feature of nuclear receptor ligand binding domains (LBD) is a helical sandwich fold that nests a ligand binding pocket within the bottom half of the domain. Here we report that the ligand pocket of glucocorticoid receptor (GR) can be continuously extended into the top half of the LBD by binding to deacylcortivazol (DAC), an extremely potent glucocorticoid. It has been puzzling for decades why DAC, which contains a phenylpyrazole replacement at the conserved 3-ketone of steroid hormones that are normally required for activation of their cognate receptors, is a potent GR activator. The crystal structure of the GR LBD bound to DAC and the fourth LXXLL motif of steroid receptor coactivator 1 reveals that the GR ligand binding pocket is expanded to a size of 1,070 Å3, effectively doubling the size of the GR dexamethasone-binding pocket of 540 Å3 and yet leaving the structure of the coactivator binding site intact. DAC occupies only ∼50% of the space of the pocket but makes intricate interactions with the receptor around the phenylpyrazole group that accounts for the high-affinity binding of DAC. The dramatic expansion of the DAC-binding pocket thus highlights the conformational adaptability of GR to ligand binding. The new structure also allows docking of various nonsteroidal ligands that cannot be fitted into the previous structures, thus providing a new rational template for drug discovery of steroidal and nonsteroidal glucocorticoids that can be specifically designed to reach the unoccupied space of the expanded pocket.

scholarly journals Determinants of spironolactone binding specificity in the mineralocorticoid receptor

2003 ◽  
Vol 31 (3) ◽  
pp. 573-582 ◽  
Author(s):  
FM Rogerson ◽  
YZ Yao ◽  
BJ Smith ◽  
N Dimopoulos ◽  
PJ Fuller
Keyword(s):  
Crystal Structure ◽  
Experimental Data ◽  
Amino Acids ◽  
Ligand Binding ◽  
Mineralocorticoid Receptor ◽  
Binding Specificity ◽  
Binding Pocket ◽  
Clinical Use ◽  
Ligand Binding Pocket ◽  
Binding Domains

Spironolactone is a mineralocorticoid receptor (MR) antagonist in clinical use. The compound has a very low affinity for the glucocorticoid receptor (GR). Determinants of binding specificity of spironolactone to the MR were investigated using chimeras created between the ligand-binding domains (LBDs) of the MR and the GR. These chimeras had previously been used to investigate aldosterone binding specificity to the MR. Spironolactone was able to compete strongly for [(3)H]-aldosterone and [(3)H]-dexamethasone binding to a chimera containing amino acids 804-874 of the MR, and weakly for [(3)H]-dexamethasone binding to a chimera containing amino acids 672-803 of the MR. Amino acids 804-874 were also critical for aldosterone binding specificity. Models of the MR LBD bound to aldosterone and spironolactone were created based on the crystal structure of the progesterone receptor LBD. The ligand-binding pocket of the MR LBD model consisted of 23 amino acids and was predominantly hydrophobic in nature. Analysis of this model in light of the experimental data suggested that spironolactone binding specificity is not governed by amino acids in the ligand-binding pocket.

scholarly journals Ligand control of interaction in vivo between ecdysteroid receptor and ultraspiracle ligand-binding domain

2004 ◽  
Vol 378 (3) ◽  
pp. 779-784 ◽  
Author(s):  
Thomas BERGMAN ◽  
Vincent C. HENRICH ◽  
Uwe SCHLATTNER ◽  
Markus LEZZI
Keyword(s):  
Ligand Binding ◽  
Fusion Proteins ◽  
Point Mutations ◽  
Binding Pocket ◽  
Binding Studies ◽  
Global Features ◽  
Ecdysteroid Receptor ◽  
Binding Domains ◽  
Dimerization Interface

Ecdysteroids (Ecs) enhance the formation of Ec receptor–ultraspiracle protein (EcR–USP) heterodimers which regulate gene transcription. To study EcR–USP heterodimerization, fusion proteins were constructed from the LBDs (ligand-binding domains) of Drosophila EcR or USP and the activation or DNA-binding region of GAL4 respectively. Reporter gene (lacZ) activation was fully dependent on the co-expression of the two fusion proteins and thus constitutes a reliable measure for the interaction in vivo between the two LBDs in the yeast cell. To identify structures involved in heterodimerization, a total of 27 point mutations were generated in the EcR and USP LBDs at selected sites. Heterodimerization and its inducibility by ligand were mainly affected by mutations in the dimerization interface and in the ligand-binding pocket of EcR respectively. However, also mutations not located in these structures or even in the LBD of USP influenced ligand-dependent heterodimerization. Together with previously reported ligand-binding studies, the existence of such local, intra- and inter-molecular mutation effects suggest that ligand-induced dimerization results from a synergistic interaction between ligand-binding and heterodimerization functions in EcR LBD, and that it depends on global features of the LBDs of EcR and USP and on their mutual surface compatibility.

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