Estrogen receptor alpha (ERα), also known as NR3A1 (nuclear receptor subfamily 3, group A, member 1), is one of two main types of

estrogen receptor Estrogen receptors (ERs) are proteins found in cell (biology), cells that function as receptor (biochemistry), receptors for the hormone estrogen (17β-estradiol). There are two main classes of ERs. The first includes the intracellular estrogen ...

, a

nuclear receptor In the field of molecular biology, nuclear receptors are a class of proteins responsible for sensing steroids, thyroid hormones, vitamins, and certain other molecules. These intracellular receptors work with other proteins to regulate the ex ...

(mainly found as a chromatin-binding protein) that is activated by the sex hormone

estrogen Estrogen (also spelled oestrogen in British English; see spelling differences) is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three ...

. In humans, ERα is encoded by the

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

''ESR1'' (EStrogen Receptor 1).

Structure

The estrogen receptor (ER) is a

ligand In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's el ...

-activated

transcription factor In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription (genetics), transcription of genetics, genetic information from DNA to messenger RNA, by binding t ...

composed of several domains important for hormone binding, DNA binding, and

activation In chemistry and biology, activation is the process whereby something is prepared or excited for a subsequent reaction. Chemistry In chemistry, "activation" refers to the reversible transition of a molecule into a nearly identical chemical or ...

of transcription.

Alternative splicing Alternative splicing, alternative RNA splicing, or differential splicing, is an alternative RNA splicing, splicing process during gene expression that allows a single gene to produce different splice variants. For example, some exons of a gene ma ...

results in several ESR1

mRNA In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of Protein biosynthesis, synthesizing a protein. mRNA is ...

transcripts, which differ primarily in their 5-prime untranslated regions. The translated receptors show less variability.

Ligands

Agonists

Non-selective

Endogenous Endogeny, in biology, refers to the property of originating or developing from within an organism, tissue, or cell. For example, ''endogenous substances'', and ''endogenous processes'' are those that originate within a living system (e.g. an ...

s (e.g.,

estradiol Estradiol (E2), also called oestrogen, oestradiol, is an estrogen steroid hormone and the major female sex hormone. It is involved in the regulation of female reproductive cycles such as estrous and menstrual cycles. Estradiol is responsible ...

estrone Estrone (E1), also spelled oestrone, is a steroid, a weak estrogen, and a minor female sex hormone. It is one of three major endogenous estrogens, the others being estradiol and estriol. Estrone, as well as the other estrogens, are synthesized ...

estriol Estriol (E3), also spelled oestriol, is a steroid, a weak estrogen, and a minor female sex hormone. It is one of three major endogenous estrogens, the others being estradiol and estrone. Levels of estriol in women who are not pregnant are almost ...

estetrol Estetrol (E4), or oestetrol, is one of the four natural estrogenic steroid hormones found in humans, along with estrone (E1), estradiol (E2), and estriol (E3). Estetrol is a major estrogen in the body. In contrast to estrone and estradiol, estet ...

) *

Natural Nature is an inherent character or constitution, particularly of the ecosphere or the universe as a whole. In this general sense nature refers to the laws, elements and phenomena of the physical world, including life. Although humans are part ...

s (e.g., conjugated equine estrogens) *

Synthetic Synthetic may refer to: Science * Synthetic biology * Synthetic chemical or compound, produced by the process of chemical synthesis * Synthetic elements, chemical elements that are not naturally found on Earth and therefore have to be created in ...

s (e.g.,

ethinylestradiol Ethinylestradiol (EE) is an estrogen medication which is used widely in birth control pills in combination with progestins. Ethinylestradiol was widely used for various indications such as the treatment of menopausal symptoms, gynecological ...

diethylstilbestrol Diethylstilbestrol (DES), also known as stilbestrol or stilboestrol, is a nonsteroidal estrogen medication, which is presently rarely used. In the past, it was widely used for a variety of indications, including pregnancy support for those with ...

)

Selective

Agonists of ERα selective over

ERβ Estrogen receptor beta (ERβ) also known as NR3A2 (nuclear receptor subfamily 3, group A, member 2) is one of two main types of estrogen receptor—a nuclear receptor which is activated by the sex hormone estrogen. In humans ERβ is encoded by t ...

include: *

Propylpyrazoletriol Propylpyrazoletriol (PPT) is a synthetic, nonsteroidal agonist of ERα with 400-fold selectivity over ERβ that is used widely in scientific research to study the function of ERα. Though originally thought to be highly selective for ERα, PPT ha ...

(PPT) * 16α-LE₂ (Cpd1471) * 16α-IE₂ *

ERA-63 ERA-63, also known as ORG-37663, as well as 3-methylene-7α-methyl-17α-ethynylestra-5(10)-en-17β-ol, is a synthetic, steroidal estrogen and a selective agonist of the ERα that was under development for the treatment of rheumatoid arthritis bu ...

(ORG-37663) *

SKF-82,958 SKF-82,958 is a synthetic compound of the benzazepine class that acts as a D1/ D5 receptor full agonist. SKF-82,958 and similar D1-like-selective full agonists like SKF-81,297 and 6-Br-APB produce characteristic anorectic effects, hyperac ...

– also a D₁-like receptor

full agonist An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the agoni ...

(R,R)-Tetrahydrochrysene (''R'',''R'')-Tetrahydrochrysene ((''R'',''R'')-THC) is a drug used to study the estrogen receptors (ERs) in scientific research. It is an ERβ antagonist and an ERα agonist with 10-fold higher affinity for ERβ relative to ERα. (''R'',''R'')- ...

((R,R)-THC) – actually not selective over ERβ, but rather an antagonist instead of an agonist of ERβ

Mixed

Phytoestrogen A phytoestrogen is a plant-derived xenoestrogen (a type of estrogen produced by organisms other than humans) not generated within the endocrine system, but consumed by eating plants or manufactured foods. Also called a "dietary estrogen", it ...

s (e.g., coumestrol,

daidzein Daidzein (7-hydroxy-3-(4-hydroxyphenyl)-4H-chromen-4-one) is a naturally occurring compound found exclusively in soybeans and other legumes, and structurally belongs to a class of compounds known as isoflavones. Daidzein and other isoflavones a ...

genistein Genistein (C15H10O5) is a plant-derived, aglycone isoflavone. Genistein has the highest content of all isoflavones in soybeans and soy products, such as tempeh. As a type of phytoestrogen, genistein has estrogenic activity in vitro; consequ ...

, miroestrol) *

Selective estrogen receptor modulator Selective estrogen receptor modulators (SERMs), also known as estrogen receptor agonists/antagonists (ERAAs), are a class of drugs that act on estrogen receptors (ERs). Compared to pure ER agonists–antagonists (e.g., full agonists and silent ...

s (e.g.,

tamoxifen Tamoxifen, sold under the brand name Nolvadex among others, is a selective estrogen receptor modulator used to prevent breast cancer in women and men. It is also being studied for other types of cancer. It has been used for Albright syndrome ...

clomifene Clomifene, also known as clomiphene, is a medication used to treat infertility in women who do not ovulate, including those with polycystic ovary syndrome. It is taken by mouth. Common side effects include pelvic pain and hot flashes. Oth ...

raloxifene Raloxifene, sold under the brand name Evista among others, is a medication used to prevent and treat osteoporosis in postmenopausal women and those on glucocorticoids. For osteoporosis it is less preferred than bisphosphonates. It is also used ...

)

Antagonists

Non-selective

Antiestrogen Antiestrogens, also known as estrogen antagonists or estrogen blockers, are a class of drugs which prevent estrogens like estradiol from mediating their biological effects in the body. They act by blocking the estrogen receptor (ER) and/or inh ...

s (e.g.,

fulvestrant Fulvestrant, sold under the brand name Faslodex among others, is an antiestrogenic medication used to treat hormone receptor (HR)-positive metastatic breast cancer in postmenopausal women with disease progression as well as HR-positive, HER2-n ...

, ICI-164384,

ethamoxytriphetol Ethamoxytriphetol (developmental code name MER-25) is a synthetic nonsteroidal antiestrogen that was studied clinically in the late 1950s and early 1960s but was never marketed. MER-25 was first reported in 1958, and was the first antiestrogen t ...

)

Selective

Antagonists of ERα selective over ERβ include: *

Methylpiperidinopyrazole Methylpiperidinopyrazole (MPP) is a synthetic, nonsteroidal, and highly selective antagonist of ERα that is used in scientific research to study the function of this receptor. It has 200-fold selectivity for ERα over ERβ and 1000-fold selectiv ...

(MPP)

Affinities

Tissue distribution and function

ERα plays a role in the physiological development and function of a variety of

organ systems An organ system is a biological system consisting of a group of organs that work together to perform one or more bodily functions. Each organ has a specialized role in an organism body, and is made up of distinct tissues. Humans There ar ...

to varying degrees, including the

reproductive The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are al ...

, central nervous,

skeletal A skeleton is the structural frame that supports the body of most animals. There are several types of skeletons, including the exoskeleton, which is a rigid outer shell that holds up an organism's shape; the endoskeleton, a rigid internal fram ...

, and cardiovascular systems. Accordingly, ERα is widely expressed throughout the body, including the

uterus The uterus (from Latin ''uterus'', : uteri or uteruses) or womb () is the hollow organ, organ in the reproductive system of most female mammals, including humans, that accommodates the embryonic development, embryonic and prenatal development, f ...

and

ovary The ovary () is a gonad in the female reproductive system that produces ova; when released, an ovum travels through the fallopian tube/ oviduct into the uterus. There is an ovary on the left and the right side of the body. The ovaries are end ...

male reproductive organs The male reproductive system consists of a number of sex organs that play a role in the process of human reproduction. These organs are located on the outside of the body, and within the pelvis. The main male sex organs are the penis and the scr ...

mammary gland A mammary gland is an exocrine gland that produces milk in humans and other mammals. Mammals get their name from the Latin word ''mamma'', "breast". The mammary glands are arranged in organs such as the breasts in primates (for example, human ...

bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...

heart The heart is a muscular Organ (biology), organ found in humans and other animals. This organ pumps blood through the blood vessels. The heart and blood vessels together make the circulatory system. The pumped blood carries oxygen and nutrie ...

hypothalamus The hypothalamus (: hypothalami; ) is a small part of the vertebrate brain that contains a number of nucleus (neuroanatomy), nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrin ...

pituitary gland The pituitary gland or hypophysis is an endocrine gland in vertebrates. In humans, the pituitary gland is located at the base of the human brain, brain, protruding off the bottom of the hypothalamus. The pituitary gland and the hypothalamus contr ...

liver The liver is a major metabolic organ (anatomy), organ exclusively found in vertebrates, which performs many essential biological Function (biology), functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of var ...

lung The lungs are the primary Organ (biology), organs of the respiratory system in many animals, including humans. In mammals and most other tetrapods, two lungs are located near the Vertebral column, backbone on either side of the heart. Their ...

kidney In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organ (anatomy), organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and rig ...

spleen The spleen (, from Ancient Greek '' σπλήν'', splḗn) is an organ (biology), organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The spleen plays important roles in reg ...

, and

adipose Adipose tissue (also known as body fat or simply fat) is a loose connective tissue composed mostly of adipocytes. It also contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, Blood vessel, vascular endothel ...

tissue. The development and function of these tissues is disrupted in

animal models A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workings of other organisms. Mod ...

lacking active ERα genes, such as the ERα

knockout mouse A knockout mouse, or knock-out mouse, is a genetically modified mouse (''Mus musculus'') in which researchers have inactivated, or " knocked out", an existing gene by replacing it or disrupting it with an artificial piece of DNA. They are importan ...

(ERKO), providing a preliminary understanding of ERα function at specific

target Target may refer to: Warfare and shooting * Shooting target, used in marksmanship training and various shooting sports ** Bullseye (target), the goal one for which one aims in many of these sports ** Aiming point, in field artille ...

organs.

Uterus and ovary

ERα is essential in the maturation of the female reproductive phenotype. In the absence of ERα, the ERKO mouse develops an adult

, indicating that ERα may not mediate the initial growth of the uterus. However, ERα plays a role in the completion of this development, and the subsequent function of the tissue. Activation of ERα is known to trigger

cell proliferation Cell proliferation is the process by which ''a cell grows and divides to produce two daughter cells''. Cell proliferation leads to an exponential increase in cell number and is therefore a rapid mechanism of tissue growth. Cell proliferation ...

in the uterus. The

of female ERKO mice is

hypoplastic Hypoplasia (; adjective form ''hypoplastic'') is underdevelopment or incomplete development of a Tissue (biology), tissue or Organ (biology), organ.mitosis Mitosis () is a part of the cell cycle in eukaryote, eukaryotic cells in which replicated chromosomes are separated into two new Cell nucleus, nuclei. Cell division by mitosis is an equational division which gives rise to genetically identic ...

and differentiation in the uterus in response to

stimulation. Similarly, prepubertal female ERKO mice develop

ovaries The ovary () is a gonad in the female reproductive system that produces ova; when released, an ovum travels through the fallopian tube/oviduct into the uterus. There is an ovary on the left and the right side of the body. The ovaries are endocr ...

that are nearly indistinguishable from those of their

wildtype The wild type (WT) is the phenotype of the typical form of a species as it occurs in nature. Originally, the wild type was conceptualized as a product of the standard "normal" allele at a locus, in contrast to that produced by a non-standard, "m ...

counterparts. However, as the ERKO mice mature they progressively present an abnormal ovarian phenotype in both

physiology Physiology (; ) is the science, scientific study of function (biology), functions and mechanism (biology), mechanisms in a life, living system. As a branches of science, subdiscipline of biology, physiology focuses on how organisms, organ syst ...

and function. Specifically, female ERKO mice develop enlarged

containing

hemorrhagic Bleeding, hemorrhage, haemorrhage or blood loss, is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethra, va ...

follicular cysts A cyst is a closed sac, having a distinct envelope and division compared with the nearby tissue. Hence, it is a cluster of cells that have grouped together to form a sac (like the manner in which water molecules group together to form a bubb ...

, which also lack the

corpus luteum The corpus luteum (Latin for "yellow body"; : corpora lutea) is a temporary endocrine structure in female ovaries involved in the production of relatively high levels of progesterone, and moderate levels of estradiol, and inhibin A. It is the ...

, and therefore do not

ovulate Ovulation is an important part of the menstrual cycle in female vertebrates where the egg cells are released from the ovaries as part of the ovarian cycle. In female humans ovulation typically occurs near the midpoint in the menstrual cycle and ...

. This adult ovarian phenotype suggests that in the absence of ERα,

is no longer able to perform

negative feedback Negative feedback (or balancing feedback) occurs when some function (Mathematics), function of the output of a system, process, or mechanism is feedback, fed back in a manner that tends to reduce the fluctuations in the output, whether caused ...

on the

, resulting in chronically elevated LH levels and constant ovarian stimulation. These results identify a pivotal role for ERα in the

, in addition to its role in the

-driven maturation through

theca In biology, a theca (: thecae) is a sheath or a covering. Botany In botany, the theca is related to plant's flower anatomy. The theca of an angiosperm consists of a pair of microsporangia that are adjacent to each other and share a common ar ...

and

interstitial cell {{Short pages monitor