scholarly journals Identification of a Novel LXXLL Motif in α-Actinin 4-spliced Isoform That Is Critical for Its Interaction with Estrogen Receptor α and Co-activators

2012 ◽  
Vol 287 (42) ◽  
pp. 35418-35429 ◽  
Author(s):  
Simran Khurana ◽  
Sharmistha Chakraborty ◽  
Xuan Zhao ◽  
Yu Liu ◽  
Dongyin Guan ◽  
...  
Keyword(s):  
Estrogen Receptor ◽  
Nuclear Receptors ◽  
Actin Filaments ◽  
Estrogen Receptor Α ◽  
Full Length ◽  
Cross Linking ◽  
Cytoskeletal Organization ◽  
Activation Domains ◽  
Lxxll Motif ◽  
Flanking Sequences

α-Actinins (ACTNs) are a family of proteins cross-linking actin filaments that maintain cytoskeletal organization and cell motility. Recently, it has also become clear that ACTN4 can function in the nucleus. In this report, we found that ACTN4 (full length) and its spliced isoform ACTN4 (Iso) possess an unusual LXXLL nuclear receptor interacting motif. Both ACTN4 (full length) and ACTN4 (Iso) potentiate basal transcription activity and directly interact with estrogen receptor α, although ACTN4 (Iso) binds ERα more strongly. We have also found that both ACTN4 (full length) and ACTN4 (Iso) interact with the ligand-independent and the ligand-dependent activation domains of estrogen receptor α. Although ACTN4 (Iso) interacts efficiently with transcriptional co-activators such as p300/CBP-associated factor (PCAF) and steroid receptor co-activator 1 (SRC-1), the full length ACTN4 protein either does not or does so weakly. More importantly, the flanking sequences of the LXXLL motif are important not only for interacting with nuclear receptors but also for the association with co-activators. Taken together, we have identified a novel extended LXXLL motif that is critical for interactions with both receptors and co-activators. This motif functions more efficiently in a spliced isoform of ACTN4 than it does in the full-length protein.

scholarly journals Ligands Differentially Modify the Nuclear Mobility of Estrogen Receptors α and β

Endocrinology ◽  
2007 ◽  
Vol 149 (1) ◽  
pp. 339-345 ◽  
Author(s):  
Anastasios E. Damdimopoulos ◽  
Giannis Spyrou ◽  
Jan-Åke Gustafsson
Keyword(s):  
Estrogen Receptor ◽  
Comparative Analysis ◽  
Nuclear Receptors ◽  
Estrogen Receptor Α ◽  
Estrogen Response Element ◽  
Subnuclear Localization ◽  
Estrogen Response ◽  
Subtype Specificity ◽  
Helix 12 ◽  
Moderate Effect

Signaling of nuclear receptors depends on the structure of their ligands, with different ligands eliciting different responses. In this study using a comparative analysis, an array of ligands was examined for effects on estrogen receptor α (ERα) and ERβ mobility. Our results indicated that these two receptors share similarities in response to some ligands but differ significantly in response to others. Our results suggest that for ERα, ligands can be classified into three distinct groups: 1) ligands that do not affect the mobility of the receptor, 2) ligands that cause a moderate effect, and 3) ligands that strongly impact mobility of ERα. Interestingly, we found that for ERβ such a classification was not possible because ERβ ligands caused a wider spectrum of responses. One of the main differences between the two receptors was the response toward the antiestrogens ICI and raloxifene, which was not attributable to differential subnuclear localization or different conformations of helix 12 in the C-terminal domain. We showed that both of these ligands caused a robust phenotype, leading to an almost total immobilization of ERα, whereas ERβ retained its mobility; we provide evidence that the mobility of the two receptors depends upon the function of the proteasome machinery. This novel finding that ERβ retains its mobility in the presence of antiestrogens could be important for its ability to regulate genes that do not contain classic estrogen response element sites and do not require DNA binding and could be used in the investigation of ligands that show ER subtype specificity.

scholarly journals Ligand-Selective Interdomain Conformations of Estrogen Receptor-α

2007 ◽  
Vol 21 (1) ◽  
pp. 49-61 ◽  
Author(s):  
Adrian Padron ◽  
Li Li ◽  
Eric M. Kofoed ◽  
Fred Schaufele
Keyword(s):  
Breast Cancer ◽  
Estrogen Receptor ◽  
Energy Transfer ◽  
Hormone Replacement ◽  
Estrogen Receptor Α ◽  
Full Length ◽  
Estrogen Receptor Modulators ◽  
Interaction Kinetics ◽  
Receptor Modulators

Abstract Selective estrogen receptor modulators (SERMs) inhibit estrogen activation of the estrogen receptor (ER) in some tissues but activate ER in other tissues. These tissue-selective actions suggest that SERMs may be identified with tissue specificities that would improve the safety of breast cancer and hormone replacement therapies. The identification of an improved SERM would be aided by understanding the effects of each SERM on the structure and interactions of ER. To date, the inability to obtain structures of the full-length ER has limited our structural characterization of SERM action to their antiestrogenic effects on the isolated ER ligand binding domain. We studied the effects of estradiol and the clinically useful SERMs 4-hydroxytamoxifen and fulvestrant on the conformation of the full-length ERα dimer complex by comparing, in living human breast cancer cells, the amounts of energy transfer between fluorophores attached to different domains of ERα. Estradiol, 4-hydroxytamoxifen, and fulvestrant all promoted the rapid formation of ERα dimers with equivalent interaction kinetics. The amino- and carboxyl-terminal ERα domains both contain activation functions differentially affected by these ligands, but the positions of only the carboxyl termini differed upon binding with estradiol, 4-hydroxytamoxifen, or fulvestrant. The association of a specific ERα dimer conformation with the binding of ligands of different clinical effect will assist the identification of a SERM with optimal tissue-selective estrogenic and antiestrogenic activities. These studies also provide a roadmap for dissecting important structural and kinetic details for any protein complex from the quantitative analysis of energy transfer.

scholarly journals Renoprotective impact of estrogen receptor-α and its splice variants in female mice with type 1 diabetes

2018 ◽  
Vol 315 (3) ◽  
pp. F512-F520 ◽  
Author(s):  
Debra L. Irsik ◽  
Melissa J. Romero-Aleshire ◽  
Erin M. Chavez ◽  
Rachel W. Fallet ◽  
Heddwen L. Brooks ◽  
...  
Keyword(s):  
Type 1 Diabetes ◽  
Estrogen Receptor ◽  
Splice Variants ◽  
Estrogen Receptor Α ◽  
Full Length ◽  
Inhibitory Influence ◽  
Renal Hypertrophy ◽  
Female Mice ◽  
Positive Immunostaining

Estrogen has been implicated in the regulation of growth and immune function in the kidney, which expresses the full-length estrogen receptor-α (ERα66), its ERα splice variants, and estrogen receptor-β (ERβ). Thus, we hypothesized that these splice variants may inhibit the glomerular enlargement that occurs early in type 1 diabetes (T1D). T1D was induced by streptozotocin (STZ) injection in 8- to 12-wk-old female mice lacking ERα66 (ERα66KO) or all ERα variants (αERKO), and their wild-type (WT) littermates. Basal renal ERα36 protein expression was reduced in the ERα66KO model and was downregulated by T1D in WT mice. T1D did not alter ERα46 or ERβ in WT-STZ; however, ERα46 was decreased modestly in ERα66KO mice. Renal hypertrophy was evident in all diabetic mice. F4/80-positive immunostaining was reduced in ERα66KO compared with WT and αERKO mice but was higher in STZ than in Control mice across all genotypes. Glomerular area was greater in WT and αERKO than in ERα66KO mice, with T1D-induced glomerular enlargement apparent in WT-STZ and αERKO-STZ, but not in ERα66KO-STZ mice. Proteinuria and hyperfiltration were evident in ERα66KO-STZ and αERKO-STZ, but not in WT-STZ mice. These data indicate that ERα splice variants may exert an inhibitory influence on glomerular enlargement and macrophage infiltration during T1D; however, effects of splice variants are masked in the presence of the full-length ERα66, suggesting that ERα66 acts in opposition to its splice variants to influence these parameters. In contrast, hyperfiltration and proteinuria in T1D are attenuated via an ERα66-dependent mechanism that is unaffected by splice variant status.

scholarly journals Expression of Estrogen Receptor α and β in Rat Astrocytes in Primary Culture: Effects of Hypoxia and Glucose Deprivation

2011 ◽  
pp. 951-960 ◽  
Author(s):  
M. D. AL-BADER ◽  
S. A. MALATIALI ◽  
Z. B. REDZIC
Keyword(s):  
Estrogen Receptor ◽  
Estrogen Receptor Alpha ◽  
Biological Effects ◽  
Estrogen Receptor Beta ◽  
Glucose Deprivation ◽  
Estrogen Receptor Α ◽  
Full Length ◽  
Control Group ◽  
Rat Astrocyte

Estrogen replacement therapy could play a role in the reduction of injury associated with cerebral ischemia in vivo, which could be, at least partially, a consequence of estrogen influence of glutamate buffering by astrocytes during hypoxia/ischemia. Estrogen exerts biological effects through interaction with its two receptors: estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ), which are both expressed in astrocytes. This study explored effects of hypoxia and glucose deprivation (HGD), alone or followed by 1 h recovery, on ERα and ERβ expression in primary rat astrocyte cultures following 1 h exposure to: a) 5 % CO2 in air (control group-CG); b) 2 % O2/5 % CO2 in N2 with glucose deprivation (HGD group-HGDG); or c) the HGDG protocol followed by 1 h CG protocol (recovery group-RG). ERα mRNA expression decreased in HGDG. At the protein level, full-length ERα (67 kDa) and three ERα-immunoreactive protein bands (63, 60 and 52 kDa) were detected. A significant decrease in the 52 kDa band was seen in HGDG, while a significant decrease in expression of the full length ERα was seen in the RG. ERβ mRNA and protein expression (a 54 kDa single band) did not change. The observed decrease in ERα protein may limit estrogen-mediated signalling in astrocytes during hypoxia and recovery.

scholarly journals Regulation ofGREB1Transcription by Estrogen Receptor α through a Multipartite Enhancer Spread Over 20 kb of Upstream Flanking Sequences

2007 ◽  
Vol 282 (24) ◽  
pp. 17335-17339 ◽  
Author(s):  
Julie Deschênes ◽  
Véronique Bourdeau ◽  
John H. White ◽  
Sylvie Mader
Keyword(s):  
Estrogen Receptor ◽  
Estrogen Receptor Α ◽  
Flanking Sequences

scholarly journals Selective Estrogen Receptor Modulators 4-Hydroxytamoxifen and Raloxifene Impact the Stability and Function of SRC-1 and SRC-3 Coactivator Proteins

2004 ◽  
Vol 24 (1) ◽  
pp. 14-24 ◽  
Author(s):  
David M. Lonard ◽  
Sophia Y. Tsai ◽  
Bert W. O'Malley
Keyword(s):  
Estrogen Receptor ◽  
Steady State ◽  
Nuclear Receptors ◽  
Transcriptional Activity ◽  
Estrogen Receptor Α ◽  
Biological Action ◽  
Protein Levels ◽  
Estrogen Receptor Modulators ◽  
Steady State Levels ◽  
Coactivator Protein

ABSTRACT Proteasome-mediated protein degradation has been implicated in playing a role in nuclear receptor-mediated gene expression; inhibition of the proteasome impairs the transcriptional activity of estrogen receptor α (ERα) and most other nuclear receptors. This coincides with blockage of agonist-dependent degradation of the receptor and elevation of the steady-state levels of SRC family coactivators and CBP. Here, we examined the effects that different ERα ligands have on coactivator protein steady-state levels and demonstrate that the selective ER modulators (SERMs) 4-hydroxytamoxifen (4HT) and raloxifene are able to elevate SRC-1 and SRC-3 protein levels. Using the HeLa cell line, we show that this effect is ERα dependent. Consistent with the observed increase in coactivator protein levels, we were also able to observe an increase in the transcriptional activity of other nuclear receptors in SERM-treated cells. Information presented here demonstrates an unexpected consequence of SERM treatment, which could help further define the complex tissue responses to 4HT and raloxifene, and suggests that these ligands can have a broad biological action, stimulating the transcriptional activity of other nuclear receptors.

Full-length sequence and expression analysis of estrogen receptor α mRNA in feline mammary tumors

2005 ◽  
Vol 96 (2) ◽  
pp. 109-118 ◽  
Author(s):  
Barbara Cardazzo ◽  
Valentina Zappulli ◽  
Federica Frassineti ◽  
Tomaso Patarnello ◽  
Massimo Castagnaro ◽  
...  
Keyword(s):  
Estrogen Receptor ◽  
Expression Analysis ◽  
Mammary Tumors ◽  
Estrogen Receptor Α ◽  
Full Length ◽  
Full Length Sequence
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