Estrogen receptor
Chr. 6 q24-q27 | |||||||
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Chr. 14 q21-q22 | |||||||
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Estrogen receptors (ERs) are a group of
Once activated by estrogen, the ER is able to translocate into the nucleus and bind to DNA to regulate the activity of different genes (i.e. it is a DNA-binding transcription factor). However, it also has additional functions independent of DNA binding.[2]
As
Proteomics
There are two different forms of the estrogen receptor, usually referred to as α and β, each encoded by a separate gene (ESR1 and ESR2, respectively). Hormone-activated estrogen receptors form dimers, and, since the two forms are coexpressed in many cell types, the receptors may form ERα (αα) or ERβ (ββ) homodimers or ERαβ (αβ) heterodimers.[3] Estrogen receptor alpha and beta show significant overall sequence homology, and both are composed of five domains designated A/B through F (listed from the N- to C-terminus; amino acid sequence numbers refer to human ER).[citation needed]
The
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Due to alternative RNA splicing, several ER isoforms are known to exist. At least three ERα and five ERβ isoforms have been identified. The ERβ isoforms receptor subtypes can transactivate transcription only when a heterodimer with the functional ERß1 receptor of 59 kDa is formed. The ERß3 receptor was detected at high levels in the testis. The two other ERα isoforms are 36 and 46kDa.[4][5]
Only in fish, but not in humans, an ERγ receptor has been described.[6]
Genetics
In humans, the two forms of the estrogen receptor are encoded by different genes, ESR1 and ESR2 on the sixth and fourteenth chromosome (6q25.1 and 14q23.2), respectively.
Distribution
Both ERs are widely expressed in different tissue types, however there are some notable differences in their expression patterns:[7]
- The ERα is found in endometrium, breast cancer cells, ovarian stromal cells, and the hypothalamus.[8] In males, ERα protein is found in the epithelium of the efferent ducts.[9]
- The expression of the ERβ protein has been documented in ovarian intestinal mucosa, prostate, and endothelialcells.
The ERs are regarded to be cytoplasmic receptors in their unliganded state, but visualization research has shown that only a small fraction of the ERs reside in the cytoplasm, with most ER constitutively in the nucleus.[11] The "ERα" primary transcript gives rise to several alternatively spliced variants of unknown function.[12]
Ligands
Agonists
- )
- Natural estrogens (e.g., conjugated estrogens)
- )
Mixed (agonist and antagonist mode of action)
- Phytoestrogens (e.g., coumestrol, daidzein, genistein, miroestrol)
- Selective estrogen receptor modulators (e.g., tamoxifen, clomifene, raloxifene)
Antagonists
- Antiestrogens (e.g., fulvestrant, ICI-164384, ethamoxytriphetol)
Affinities
Ligand | Other names | Relative binding affinities (RBA, %)a |
Absolute binding affinities (Ki, nM)a |
Action | ||
---|---|---|---|---|---|---|
ERα |
ERβ |
ERα |
ERβ
| |||
Estradiol | E2; 17β-Estradiol | 100 | 100 | 0.115 (0.04–0.24) | 0.15 (0.10–2.08) | Estrogen |
Estrone | E1; 17-Ketoestradiol | 16.39 (0.7–60) | 6.5 (1.36–52) | 0.445 (0.3–1.01) | 1.75 (0.35–9.24) | Estrogen |
Estriol | E3; 16α-OH-17β-E2 | 12.65 (4.03–56) | 26 (14.0–44.6) | 0.45 (0.35–1.4) | 0.7 (0.63–0.7) | Estrogen |
Estetrol | E4; 15α,16α-Di-OH-17β-E2 | 4.0 | 3.0 | 4.9 | 19 | Estrogen |
Alfatradiol | 17α-Estradiol | 20.5 (7–80.1) | 8.195 (2–42) | 0.2–0.52 | 0.43–1.2 | Metabolite |
16-Epiestriol |
16β-Hydroxy-17β-estradiol | 7.795 (4.94–63) | 50 | ? | ? | Metabolite |
17-Epiestriol |
16α-Hydroxy-17α-estradiol | 55.45 (29–103) | 79–80 | ? | ? | Metabolite |
16,17-Epiestriol |
16β-Hydroxy-17α-estradiol | 1.0 | 13 | ? | ? | Metabolite |
2-Hydroxyestradiol | 2-OH-E2 | 22 (7–81) | 11–35 | 2.5 | 1.3 | Metabolite |
2-Methoxyestradiol | 2-MeO-E2 | 0.0027–2.0 | 1.0 | ? | ? | Metabolite |
4-Hydroxyestradiol | 4-OH-E2 | 13 (8–70) | 7–56 | 1.0 | 1.9 | Metabolite |
4-Methoxyestradiol | 4-MeO-E2 | 2.0 | 1.0 | ? | ? | Metabolite |
2-Hydroxyestrone | 2-OH-E1 | 2.0–4.0 | 0.2–0.4 | ? | ? | Metabolite |
2-Methoxyestrone | 2-MeO-E1 | <0.001–<1 | <1 | ? | ? | Metabolite |
4-Hydroxyestrone | 4-OH-E1 | 1.0–2.0 | 1.0 | ? | ? | Metabolite |
4-Methoxyestrone | 4-MeO-E1 | <1 | <1 | ? | ? | Metabolite |
16α-Hydroxyestrone | 16α-OH-E1; 17-Ketoestriol | 2.0–6.5 | 35 | ? | ? | Metabolite |
2-Hydroxyestriol | 2-OH-E3 | 2.0 | 1.0 | ? | ? | Metabolite |
4-Methoxyestriol | 4-MeO-E3 | 1.0 | 1.0 | ? | ? | Metabolite |
Estradiol sulfate | E2S; Estradiol 3-sulfate | <1 | <1 | ? | ? | Metabolite |
Estradiol disulfate | Estradiol 3,17β-disulfate | 0.0004 | ? | ? | ? | Metabolite |
Estradiol 3-glucuronide | E2-3G | 0.0079 | ? | ? | ? | Metabolite |
Estradiol 17β-glucuronide |
E2-17G | 0.0015 | ? | ? | ? | Metabolite |
Estradiol 3-gluc. 17β-sulfate | E2-3G-17S | 0.0001 | ? | ? | ? | Metabolite |
Estrone sulfate | E1S; Estrone 3-sulfate | <1 | <1 | >10 | >10 | Metabolite |
Estradiol benzoate | EB; Estradiol 3-benzoate | 10 | ? | ? | ? | Estrogen |
Estradiol 17β-benzoate | E2-17B | 11.3 | 32.6 | ? | ? | Estrogen |
Estrone methyl ether | Estrone 3-methyl ether | 0.145 | ? | ? | ? | Estrogen |
ent-Estradiol | 1-Estradiol | 1.31–12.34 | 9.44–80.07 | ? | ? | Estrogen |
Equilin | 7-Dehydroestrone | 13 (4.0–28.9) | 13.0–49 | 0.79 | 0.36 | Estrogen |
Equilenin | 6,8-Didehydroestrone | 2.0–15 | 7.0–20 | 0.64 | 0.62 | Estrogen |
17β-Dihydroequilin | 7-Dehydro-17β-estradiol | 7.9–113 | 7.9–108 | 0.09 | 0.17 | Estrogen |
17α-Dihydroequilin | 7-Dehydro-17α-estradiol | 18.6 (18–41) | 14–32 | 0.24 | 0.57 | Estrogen |
17β-Dihydroequilenin | 6,8-Didehydro-17β-estradiol | 35–68 | 90–100 | 0.15 | 0.20 | Estrogen |
17α-Dihydroequilenin | 6,8-Didehydro-17α-estradiol | 20 | 49 | 0.50 | 0.37 | Estrogen |
Δ8-Estradiol | 8,9-Dehydro-17β-estradiol | 68 | 72 | 0.15 | 0.25 | Estrogen |
Δ8-Estrone | 8,9-Dehydroestrone | 19 | 32 | 0.52 | 0.57 | Estrogen |
Ethinylestradiol | EE; 17α-Ethynyl-17β-E2 | 120.9 (68.8–480) | 44.4 (2.0–144) | 0.02–0.05 | 0.29–0.81 | Estrogen |
Mestranol | EE 3-methyl ether | ? | 2.5 | ? | ? | Estrogen |
Moxestrol | RU-2858; 11β-Methoxy-EE | 35–43 | 5–20 | 0.5 | 2.6 | Estrogen |
Methylestradiol | 17α-Methyl-17β-estradiol | 70 | 44 | ? | ? | Estrogen |
Diethylstilbestrol | DES; Stilbestrol | 129.5 (89.1–468) | 219.63 (61.2–295) | 0.04 | 0.05 | Estrogen |
Hexestrol | Dihydrodiethylstilbestrol | 153.6 (31–302) | 60–234 | 0.06 | 0.06 | Estrogen |
Dienestrol | Dehydrostilbestrol | 37 (20.4–223) | 56–404 | 0.05 | 0.03 | Estrogen |
Benzestrol (B2) | – | 114 | ? | ? | ? | Estrogen |
Chlorotrianisene | TACE | 1.74 | ? | 15.30 | ? | Estrogen |
Triphenylethylene | TPE | 0.074 | ? | ? | ? | Estrogen |
Triphenylbromoethylene | TPBE | 2.69 | ? | ? | ? | Estrogen |
Tamoxifen | ICI-46,474 | 3 (0.1–47) | 3.33 (0.28–6) | 3.4–9.69 | 2.5 | SERM |
Afimoxifene | 4-Hydroxytamoxifen; 4-OHT | 100.1 (1.7–257) | 10 (0.98–339) | 2.3 (0.1–3.61) | 0.04–4.8 | SERM |
Toremifene | 4-Chlorotamoxifen; 4-CT | ? | ? | 7.14–20.3 | 15.4 | SERM |
Clomifene | MRL-41 | 25 (19.2–37.2) | 12 | 0.9 | 1.2 | SERM |
Cyclofenil | F-6066; Sexovid | 151–152 | 243 | ? | ? | SERM |
Nafoxidine | U-11,000A | 30.9–44 | 16 | 0.3 | 0.8 | SERM |
Raloxifene | – | 41.2 (7.8–69) | 5.34 (0.54–16) | 0.188–0.52 | 20.2 | SERM |
Arzoxifene | LY-353,381 | ? | ? | 0.179 | ? | SERM |
Lasofoxifene | CP-336,156 | 10.2–166 | 19.0 | 0.229 | ? | SERM |
Ormeloxifene | Centchroman | ? | ? | 0.313 | ? | SERM |
Levormeloxifene | 6720-CDRI; NNC-460,020 | 1.55 | 1.88 | ? | ? | SERM |
Ospemifene | Deaminohydroxytoremifene | 0.82–2.63 | 0.59–1.22 | ? | ? | SERM |
Bazedoxifene | – | ? | ? | 0.053 | ? | SERM |
Etacstil | GW-5638 | 4.30 | 11.5 | ? | ? | SERM |
ICI-164,384 |
– | 63.5 (3.70–97.7) | 166 | 0.2 | 0.08 | Antiestrogen |
Fulvestrant | ICI-182,780 | 43.5 (9.4–325) | 21.65 (2.05–40.5) | 0.42 | 1.3 | Antiestrogen |
Propylpyrazoletriol | PPT | 49 (10.0–89.1) | 0.12 | 0.40 | 92.8 | ERα agonist |
16α-LE2 | 16α-Lactone-17β-estradiol | 14.6–57 | 0.089 | 0.27 | 131 | ERα agonist |
16α-Iodo-E2 | 16α-Iodo-17β-estradiol | 30.2 | 2.30 | ? | ? | ERα agonist |
Methylpiperidinopyrazole | MPP | 11 | 0.05 | ? | ? | ERα antagonist |
Diarylpropionitrile | DPN | 0.12–0.25 | 6.6–18 | 32.4 | 1.7 | ERβ agonist |
8β-VE2 | 8β-Vinyl-17β-estradiol | 0.35 | 22.0–83 | 12.9 | 0.50 | ERβ agonist |
Prinaberel | ERB-041; WAY-202,041 | 0.27 | 67–72 | ? | ? | ERβ agonist |
ERB-196 | WAY-202,196 | ? | 180 | ? | ? | ERβ agonist |
Erteberel | SERBA-1; LY-500,307 | ? | ? | 2.68 | 0.19 | ERβ agonist |
SERBA-2 | – | ? | ? | 14.5 | 1.54 | ERβ agonist |
Coumestrol | – | 9.225 (0.0117–94) | 64.125 (0.41–185) | 0.14–80.0 | 0.07–27.0 | Xenoestrogen |
Genistein | – | 0.445 (0.0012–16) | 33.42 (0.86–87) | 2.6–126 | 0.3–12.8 | Xenoestrogen |
Equol | – | 0.2–0.287 | 0.85 (0.10–2.85) | ? | ? | Xenoestrogen |
Daidzein | – | 0.07 (0.0018–9.3) | 0.7865 (0.04–17.1) | 2.0 | 85.3 | Xenoestrogen |
Biochanin A | – | 0.04 (0.022–0.15) | 0.6225 (0.010–1.2) | 174 | 8.9 | Xenoestrogen |
Kaempferol | – | 0.07 (0.029–0.10) | 2.2 (0.002–3.00) | ? | ? | Xenoestrogen |
Naringenin | – | 0.0054 (<0.001–0.01) | 0.15 (0.11–0.33) | ? | ? | Xenoestrogen |
8-Prenylnaringenin | 8-PN | 4.4 | ? | ? | ? | Xenoestrogen |
Quercetin | – | <0.001–0.01 | 0.002–0.040 | ? | ? | Xenoestrogen |
Ipriflavone | – | <0.01 | <0.01 | ? | ? | Xenoestrogen |
Miroestrol | – | 0.39 | ? | ? | ? | Xenoestrogen |
Deoxymiroestrol |
– | 2.0 | ? | ? | ? | Xenoestrogen |
β-Sitosterol |
– | <0.001–0.0875 | <0.001–0.016 | ? | ? | Xenoestrogen |
Resveratrol | – | <0.001–0.0032 | ? | ? | ? | Xenoestrogen |
α-Zearalenol | – | 48 (13–52.5) | ? | ? | ? | Xenoestrogen |
β-Zearalenol | – | 0.6 (0.032–13) | ? | ? | ? | Xenoestrogen |
Zeranol | α-Zearalanol | 48–111 | ? | ? | ? | Xenoestrogen |
Taleranol | β-Zearalanol | 16 (13–17.8) | 14 | 0.8 | 0.9 | Xenoestrogen |
Zearalenone | ZEN | 7.68 (2.04–28) | 9.45 (2.43–31.5) | ? | ? | Xenoestrogen |
Zearalanone | ZAN | 0.51 | ? | ? | ? | Xenoestrogen |
Bisphenol A | BPA | 0.0315 (0.008–1.0) | 0.135 (0.002–4.23) | 195 | 35 | Xenoestrogen |
Endosulfan | EDS | <0.001–<0.01 | <0.01 | ? | ? | Xenoestrogen |
Kepone |
Chlordecone | 0.0069–0.2 | ? | ? | ? | Xenoestrogen |
o,p'-DDT |
– | 0.0073–0.4 | ? | ? | ? | Xenoestrogen |
p,p'-DDT |
– | 0.03 | ? | ? | ? | Xenoestrogen |
Methoxychlor | p,p'-Dimethoxy-DDT | 0.01 (<0.001–0.02) | 0.01–0.13 | ? | ? | Xenoestrogen |
HPTE | Hydroxychlor; p,p'-OH-DDT | 1.2–1.7 | ? | ? | ? | Xenoestrogen |
Testosterone | T; 4-Androstenolone | <0.0001–<0.01 | <0.002–0.040 | >5000 | >5000 | Androgen |
Dihydrotestosterone | DHT; 5α-Androstanolone | 0.01 (<0.001–0.05) | 0.0059–0.17 | 221–>5000 | 73–1688 | Androgen |
Nandrolone | 19-Nortestosterone; 19-NT | 0.01 | 0.23 | 765 | 53 | Androgen |
Dehydroepiandrosterone | DHEA; Prasterone | 0.038 (<0.001–0.04) | 0.019–0.07 | 245–1053 | 163–515 | Androgen |
5-Androstenediol |
A5; Androstenediol | 6 | 17 | 3.6 | 0.9 | Androgen |
4-Androstenediol | – | 0.5 | 0.6 | 23 | 19 | Androgen |
4-Androstenedione |
A4; Androstenedione | <0.01 | <0.01 | >10000 | >10000 | Androgen |
3α-Androstanediol | 3α-Adiol | 0.07 | 0.3 | 260 | 48 | Androgen |
3β-Androstanediol | 3β-Adiol | 3 | 7 | 6 | 2 | Androgen |
Androstanedione | 5α-Androstanedione | <0.01 | <0.01 | >10000 | >10000 | Androgen |
Etiocholanedione | 5β-Androstanedione | <0.01 | <0.01 | >10000 | >10000 | Androgen |
Methyltestosterone | 17α-Methyltestosterone | <0.0001 | ? | ? | ? | Androgen |
Ethinyl-3α-androstanediol |
17α-Ethynyl-3α-adiol | 4.0 | <0.07 | ? | ? | Estrogen |
Ethinyl-3β-androstanediol |
17α-Ethynyl-3β-adiol | 50 | 5.6 | ? | ? | Estrogen |
Progesterone | P4; 4-Pregnenedione | <0.001–0.6 | <0.001–0.010 | ? | ? | Progestogen |
Norethisterone | NET; 17α-Ethynyl-19-NT | 0.085 (0.0015–<0.1) | 0.1 (0.01–0.3) | 152 | 1084 | Progestogen |
Norethynodrel |
5(10)-Norethisterone | 0.5 (0.3–0.7) | <0.1–0.22 | 14 | 53 | Progestogen |
Tibolone | 7α-Methylnorethynodrel | 0.5 (0.45–2.0) | 0.2–0.076 | ? | ? | Progestogen |
Δ4-Tibolone | 7α-Methylnorethisterone | 0.069–<0.1 | 0.027–<0.1 | ? | ? | Progestogen |
3α-Hydroxytibolone | – | 2.5 (1.06–5.0) | 0.6–0.8 | ? | ? | Progestogen |
3β-Hydroxytibolone | – | 1.6 (0.75–1.9) | 0.070–0.1 | ? | ? | Progestogen |
Footnotes: a = (1) ERβ proteins (except the ERβ values from Kuiper et al. (1997), which are rat ERβ). Sources: See template page.
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Binding and functional selectivity
The ER's helix 12 domain plays a crucial role in determining interactions with coactivators and corepressors and, therefore, the respective agonist or antagonist effect of the ligand.[13][14]
Different ligands may differ in their affinity for alpha and beta isoforms of the estrogen receptor:
- estradiol binds equally well to both receptors[15]
- estrone, and raloxifene bind preferentially to the alpha receptor[15]
- estriol, and genistein to the beta receptor[15]
Subtype selective estrogen receptor modulators preferentially bind to either the α- or the β-subtype of the receptor. In addition, the different estrogen receptor combinations may respond differently to various ligands, which may translate into tissue selective agonistic and antagonistic effects.[16] The ratio of α- to β- subtype concentration has been proposed to play a role in certain diseases.[17]
The concept of selective estrogen receptor modulators is based on the ability to promote ER interactions with different proteins such as
Signal transduction
Since estrogen is a
Genomic
In the absence of hormone, estrogen receptors are largely located in the cytosol. Hormone binding to the receptor triggers a number of events starting with migration of the receptor from the cytosol into the nucleus, dimerization of the receptor, and subsequent binding of the receptor dimer to specific sequences of DNA known as
The receptor also interacts with
Direct acetylation of the estrogen receptor alpha at the lysine residues in hinge region by p300 regulates transactivation and hormone sensitivity.[20]
Non-genomic
Some estrogen receptors associate with the
In addition, some ER may associate with cell membranes by attachment to
17β-Estradiol has been shown to activate the
Differences and malfunction
Cancer
Estrogen receptors are over-expressed in around 70% of
- First, binding of estrogen to the ER stimulates proliferation of mammary cells, with the resulting increase in cell division and DNA replication, leading to mutations.
- Second, estrogen metabolism produces genotoxicwaste.
The result of both processes is disruption of cell cycle, apoptosis and DNA repair, which increases the chance of tumour formation. ERα is certainly associated with more differentiated tumours, while evidence that ERβ is involved is controversial. Different versions of the ESR1 gene have been identified (with single-nucleotide polymorphisms) and are associated with different risks of developing breast cancer.[19]
Estrogen and the ERs have also been implicated in
However,
Menopause
The metabolic effects of estrogen in postmenopausal women has been linked to the genetic polymorphism of estrogen receptor beta (ER-β).[32]
Aging
Studies in female mice have shown that estrogen receptor-alpha declines in the pre-optic
Obesity
A dramatic demonstration of the importance of estrogens in the regulation of fat deposition comes from transgenic mice that were genetically engineered to lack a functional aromatase gene. These mice have very low levels of estrogen and are obese.[33] Obesity was also observed in estrogen deficient female mice lacking the follicle-stimulating hormone receptor.[34] The effect of low estrogen on increased obesity has been linked to estrogen receptor alpha.[35]
SERMs for other treatment purposes
SERMs are also being studied for the treatment of uterine fibroids[36] and endometriosis.[37]
Estrogen insensitivity syndrome
Discovery
Estrogen receptors were first identified by Elwood V. Jensen at the University of Chicago in 1958,[40][41] for which Jensen was awarded the Lasker Award.[42] The gene for a second estrogen receptor (ERβ) was identified in 1996 by Kuiper et al. in rat prostate and ovary using degenerate ERalpha primers.[43]
See also
- Membrane estrogen receptor
- Estrogen insensitivity syndrome
- Aromatase deficiency
- Aromatase excess syndrome
References
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- ^ PMID 15705661.
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- ISBN 978-1-60913-345-0.
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- PMID 12796359.
- PMID 21888507.
- ^ David Bracey, 2004 "UC Scientist Wins 'American Nobel' Research Award." University of Cincinnati press release.
- PMID 8650195.
External links
- Estrogen Receptors at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
- David S. Goodsell (2003-09-01). "Estrogen Receptor". Protein Data Bank, Research Collaboratory for Structural Bioinformatics (RCSB). Archived from the original on March 11, 2006. Retrieved 2008-03-15.