The progesterone receptor (PR), also known as NR3C3 or nuclear receptor subfamily 3, group C, member 3, is a protein found inside cells. It is activated by the steroid hormone progesterone.
In humans, PR is encoded by a single PGRgene residing on chromosome 11q22,[1][2][3] it has two isoforms, PR-A and PR-B, that differ in their molecular weight.[4][5][6] The PR-B is the positive regulator of the effects of progesterone, while PR-A serve to antagonize the effects of PR-B.[7]
Progesterone is necessary to induce the progesterone receptors. When no binding hormone is present the carboxyl terminal inhibits transcription. Binding to a hormone induces a structural change that removes the inhibitory action. Progesterone antagonists prevent the structural reconfiguration.
After progesterone binds to the receptor, restructuring with dimerization follows and the complex enters the nucleus and binds to DNA. There transcription takes place, resulting in formation of messenger RNA that is translated by ribosomes to produce specific proteins.
In common with other steroid receptors, the progesterone receptor has a N-terminal regulatory domain, a DNA binding domain, a hinge section, and a C-terminal ligand binding domain. A special transcription activation function (TAF), called TAF-3, is present in the progesterone receptor-B, in a B-upstream segment (BUS) at the amino acid terminal. This segment is not present in the receptor-A.
As demonstrated in progesterone receptor-deficient mice, the physiological effects of progesterone depend completely on the presence of the human progesterone receptor (hPR), a member of the steroid-receptor superfamily of nuclear receptors. The single-copy human (hPR) gene uses separate promoters and translational start sites to produce two isoforms, hPR-A and -B, which are identical except for an additional 165 amino acids present only in the N terminus of hPR-B.[8] Although hPR-B shares many important structural domains with hPR-A, they are in fact two functionally distinct transcription factors, mediating their own response genes and physiological effects with little overlap. Selective ablation of PR-A in a mouse model, resulting in exclusive production of PR-B, unexpectedly revealed that PR-B contributes to, rather than inhibits, epithelial cell proliferation both in response to estrogen alone and in the presence of progesterone and estrogen. These results suggest that in the uterus, the PR-A isoform is necessary to oppose estrogen-induced proliferation as well as PR-B-dependent proliferation.
Functional polymorphisms
Six variable sites, including four polymorphisms and five common haplotypes have been identified in the human PR gene .[9] One promoter region polymorphism, +331G/A, creates a unique transcription start site. Biochemical assays showed that the +331G/A polymorphism increases transcription of the PR gene, favoring production of hPR-B in an Ishikawa endometrial cancer cell line.[10]
Several studies have now shown no association between progesterone receptor gene +331G/A polymorphisms and breast or endometrial cancers.[11][12] However, these follow-up studies lacked the sample size and statistical power to make any definitive conclusions, due to the rarity of the +331A SNP. It is currently unknown which if any polymorphisms in this receptor are of significance to cancer.
Biological role
Knockout mice of the PR have been found to have severely impaired lobuloalveolar development of the mammary glands[13] as well as delayed but otherwise normal mammary ductal development at puberty.[14][15]
↑Misrahi M, Atger M, d'Auriol L, Loosfelt H, Meriel C, Fridlansky F, Guiochon-Mantel A, Galibert F, Milgrom E (March 1987). "Complete amino acid sequence of the human progesterone receptor deduced from cloned cDNA". Biochemical and Biophysical Research Communications. 143 (2): 740–8. doi:10.1016/0006-291X(87)91416-1. PMID3551956.
↑Gadkar-Sable S, Shah C, Rosario G, Sachdeva G, Puri C (2005). "Progesterone receptors: various forms and functions in reproductive tissues". Frontiers in Bioscience. 10: 2118–30. doi:10.2741/1685. PMID15970482.
↑Kase NG, Speroff L, Glass RL (1999). Clinical gynecologic endocrinology and infertility. Hagerstown, MD: Lippincott Williams & Wilkins. ISBN0-683-30379-1.
↑Fritz MA, Speroff L (2005). Clinical gynecologic endocrinology and infertility. Hagerstown, MD: Lippincott Williams & Wilkins. ISBN0-7817-4795-3.
↑Feigelson HS, Rodriguez C, Jacobs EJ, Diver WR, Thun MJ, Calle EE (June 2004). "No association between the progesterone receptor gene +331G/A polymorphism and breast cancer". Cancer Epidemiology, Biomarkers & Prevention. 13 (6): 1084–5. PMID15184270.
↑Dossus L, Canzian F, Kaaks R, Boumertit A, Weiderpass E (July 2006). "No association between progesterone receptor gene +331G/A polymorphism and endometrial cancer". Cancer Epidemiology, Biomarkers & Prevention. 15 (7): 1415–6. doi:10.1158/1055-9965.EPI-06-0215. PMID16835347.
↑Hilton HN, Graham JD, Clarke CL (September 2015). "Minireview: Progesterone Regulation of Proliferation in the Normal Human Breast and in Breast Cancer: A Tale of Two Scenarios?". Molecular Endocrinology. 29 (9): 1230–42. doi:10.1210/me.2015-1152. PMID26266959.
↑Zhang XL, Zhang D, Michel FJ, Blum JL, Simmen FA, Simmen RC (June 2003). "Selective interactions of Kruppel-like factor 9/basic transcription element-binding protein with progesterone receptor isoforms A and B determine transcriptional activity of progesterone-responsive genes in endometrial epithelial cells". The Journal of Biological Chemistry. 278 (24): 21474–82. doi:10.1074/jbc.M212098200. PMID12672823.
Guiochon-Mantel A, Loosfelt H, Lescop P, Sar S, Atger M, Perrot-Applanat M, Milgrom E (June 1989). "Mechanisms of nuclear localization of the progesterone receptor: evidence for interaction between monomers". Cell. 57 (7): 1147–54. doi:10.1016/0092-8674(89)90052-4. PMID2736623.
Oñate SA, Tsai SY, Tsai MJ, O'Malley BW (November 1995). "Sequence and characterization of a coactivator for the steroid hormone receptor superfamily". Science. 270 (5240): 1354–7. doi:10.1126/science.270.5240.1354. PMID7481822.
Zhang Y, Beck CA, Poletti A, Edwards DP, Weigel NL (December 1994). "Identification of phosphorylation sites unique to the B form of human progesterone receptor. In vitro phosphorylation by casein kinase II". The Journal of Biological Chemistry. 269 (49): 31034–40. PMID7983041.
Mansour I, Reznikoff-Etievant MF, Netter A (August 1994). "No evidence for the expression of the progesterone receptor on peripheral blood lymphocytes during pregnancy". Human Reproduction. 9 (8): 1546–9. doi:10.1093/oxfordjournals.humrep.a138746. PMID7989520.
Kalkhoven E, Wissink S, van der Saag PT, van der Burg B (March 1996). "Negative interaction between the RelA(p65) subunit of NF-kappaB and the progesterone receptor". The Journal of Biological Chemistry. 271 (11): 6217–24. doi:10.1074/jbc.271.11.6217. PMID8626413.
Wang JD, Zhu JB, Fu Y, Shi WL, Qiao GM, Wang YQ, Chen J, Zhu PD (February 1996). "Progesterone receptor immunoreactivity at the maternofetal interface of first trimester pregnancy: a study of the trophoblast population". Human Reproduction. 11 (2): 413–9. doi:10.1093/humrep/11.2.413. PMID8671234.
Thénot S, Henriquet C, Rochefort H, Cavaillès V (May 1997). "Differential interaction of nuclear receptors with the putative human transcriptional coactivator hTIF1". The Journal of Biological Chemistry. 272 (18): 12062–8. doi:10.1074/jbc.272.18.12062. PMID9115274.
Shanker YG, Sharma SC, Rao AJ (September 1997). "Expression of progesterone receptor mRNA in the first trimester human placenta". Biochemistry and Molecular Biology International. 42 (6): 1235–40. doi:10.1080/15216549700203701. PMID9305541.
Richer JK, Lange CA, Wierman AM, Brooks KM, Tung L, Takimoto GS, Horwitz KB (April 1998). "Progesterone receptor variants found in breast cells repress transcription by wild-type receptors". Breast Cancer Research and Treatment. 48 (3): 231–41. doi:10.1023/A:1005941117247. PMID9598870.
Williams SP, Sigler PB (May 1998). "Atomic structure of progesterone complexed with its receptor". Nature. 393 (6683): 392–6. doi:10.1038/30775. PMID9620806.
