Prolactin Receptor | |||||||
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Identifiers | |||||||
Symbol | PRLR | ||||||
NCBI gene | 5618 | ||||||
HGNC | 9446 | ||||||
OMIM | 176761 | ||||||
PDB | 1RW5 | ||||||
RefSeq | NM_000949 | ||||||
UniProt | P16471 | ||||||
Other data | |||||||
Locus | Chr. 5 p13-p12 | ||||||
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The prolactin receptor (PRLR) is a type I cytokine receptor [1] encoded in humans by the PRLR gene on chromosome 5p13-14. It is the receptor for prolactin (PRL). The PRLR can also bind to and be activated by growth hormone (GH) and human placental lactogen (hPL). The PRLR is expressed in the mammary glands, pituitary gland, and other tissues. It plays an important role in lobuloalveolar development of the mammary glands during pregnancy and in lactation.
The prolactin receptor (PRLR) is a membrane-bound protein of the cytokine receptor superfamily. In humans, it is encoded by a single gene which contains 11 exons and is located on chromosome 5. [2] PRLR expression can be found in several tissues such as the gonads, breast, uterus, heart, liver, kidney, brain, immune cells, as well as adrenal and pituitary glands.
Several PRLR isoforms have been described in different tissues. These have varying lengths and cytoplasmic domain composition, but share identical extracellular domains, which are the regions binding to PRLR.
Diversity of PRLR is a result of transcription initiation in different sites of the PRLR promoter region. Additionally, post-translational modifications, like alternative splicing are the events that result in the different isoforms that allow for all the different actions of prolactin in the body. [3]
The PRLR is a class 1 cytokine receptor that uses messenger pathways to control cell proliferation, migration, intracellular ion concentration and inhibit programmed cell death (apoptosis). [4] [5] PRLRs also have functions in the second messenger cascades, including:
Expression of the PRLR protein is found within cells of the mammary glands [10] in accordance with its role in lactation, but also is the subject of attention for its diverse and emerging roles by its expression in adipose tissue, [11] pancreatic islet cell proliferation, [12] and immune responses. [13] The PRLR has been found to be essential for lobuloalveolar maturation of the mammary glands during pregnancy, as evidenced by the fact that PRLR knockout mice show severely impaired development of lobuloalveolar structures. [14] [15] Disruption of PRLR signaling pathways have been linked to tumorigenesis and breast cancer development. [16]
Prolactin receptor antagonists such as Del1-9-G129R-hPRL have been developed. [18] [19] [20] [21] [22]
Dopamine agonists are currently the most common methods used for treating hyperprolactinemia. However, since dopamine agonists only negatively regulate prolactin production from the pituitary gland, a few studies have tried to develop prolactin receptor antagonists for potentially treating the dopamine-resistant local hyperprolactinemia. [18] [23] Δ1–9-G129R-hPRL is one of the prolactin receptor antagonists been studied. Δ1–9-G129R-hPRL as a mutant (inactivated) form of prolactin which exerts its antagonist effect by competing with prolactin to bind with prolactin receptors; thereby, inhibiting the agonist effects of prolactin on prolactin receptors. [18] Besides molecular antagonists, antibodies can also potentially be used to inhibit prolactin receptor signaling. LFA102 is a monoclonal antibody that has been studied and tested for disrupting prolactin receptor's signaling in breast cancers and prostate cancers. [24] Although LFA102 has been proved sufficient to reduce prolactin receptor signaling based on in vitro and in vivo (mouse) studies, LFA102 likely has low effects on limiting tumor growth (breast and prostate cancer) as shown in phase I clinical trials. [24] [25]
PRLR dysfunction has been seen to positively regulate the proliferation of malignant cells in breast cancer. Defects on prolactin receptor signalling can trigger tumour activity, rather than suppress. Signal control is monitored by a variety of genes, and the PRLR gene has been identified in the tissue of metastatic primary breast cancer cells. [26] The defect in the gene is thought to have built a resistance to chemotherapy, and has lost the ability to regulate the apoptosis of cells with mutated DNA. [27] This signalling defect then fails to promote the cellular differentiation, and promotes the upstream survival of the cancerous cells. In breast cancer, the survival of the breast epithelial cells resemble the malignant cells, characteristically known to have an increased proliferative rate. [28]
Prolactin (PRL), also known as lactotropin, is a protein best known for its role in enabling mammals to produce milk. It is influential in over 300 separate processes in various vertebrates, including humans. Prolactin is secreted from the pituitary gland in response to eating, mating, estrogen treatment, ovulation and nursing. It is secreted heavily in pulses in between these events. Prolactin plays an essential role in metabolism, regulation of the immune system and pancreatic development.
A mammary gland is an exocrine gland in humans and other mammals that produces milk to feed young offspring. Mammals get their name from the Latin word mamma, "breast". The mammary glands are arranged in organs such as the breasts in primates, the udder in ruminants, and the dugs of other animals. Lactorrhea, the occasional production of milk by the glands, can occur in any mammal, but in most mammals, lactation, the production of enough milk for nursing, occurs only in phenotypic females who have gestated in recent months or years. It is directed by hormonal guidance from sex steroids. In a few mammalian species, male lactation can occur. With humans, male lactation can occur only under specific circumstances.
Mouse mammary tumor virus (MMTV) is a milk-transmitted retrovirus like the HTL viruses, HI viruses, and BLV. It belongs to the genus Betaretrovirus. MMTV was formerly known as Bittner virus, and previously the "milk factor", referring to the extra-chromosomal vertical transmission of murine breast cancer by adoptive nursing, demonstrated in 1936, by John Joseph Bittner while working at the Jackson Laboratory in Bar Harbor, Maine. Bittner established the theory that a cancerous agent, or "milk factor", could be transmitted by cancerous mothers to young mice from a virus in their mother's milk. The majority of mammary tumors in mice are caused by mouse mammary tumor virus.
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G protein-coupled estrogen receptor 1 (GPER), also known as G protein-coupled receptor 30 (GPR30), is a protein that in humans is encoded by the GPER gene. GPER binds to and is activated by the female sex hormone estradiol and is responsible for some of the rapid effects that estradiol has on cells.
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Eduardo Arzt is an Argentine molecular biologist, Master in Experimental Biology, Doctor (Ph.D) from the Faculty of Pharmacy and Biochemistry. Currently, he is a senior researcher at CONICET, distinguished professor of the Faculty of Natural Sciences of the University of Buenos Aires, External Scientific Member of the Max Planck Society (Germany) and director of the Biomedicine Research Institute of Buenos Aires – CONICET – Partner Institute of the Max Planck Society.
Benita S. Katzenellenbogen née Schulman is an American physiologist and cell biologist at the University of Illinois at Urbana-Champaign. She has studied cancer, endocrinology, and women's health, focusing on nuclear receptors. She also dedicated efforts to focusing on improving the effectiveness of endocrine therapies in breast cancer.
Cathrin Brisken is a German and Swiss medical doctor, researcher, and professor at the École Polytechnique Fédérale de Lausanne (EPFL). Her research focuses on the mechanisms of hormonal control in breast cancer development.