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Luteinizing hormone/choriogonadotropin receptor




Luteinizing hormone/choriogonadotropin receptor
Identifiers
Symbol(s) LHCGR; LHR; LCGR; LGR2; hLHR
External IDs OMIM: 152790 MGI: 96783 Homologene: 37276
RNA expression pattern

More reference expression data

Orthologs
Human Mouse
Entrez 3973 16867
Ensembl ENSG00000138039 ENSMUSG00000024107
Uniprot P22888 P30730
Refseq NM_000233 (mRNA)
NP_000224 (protein)
NM_013582 (mRNA)
NP_038610 (protein)
Location Chr 2: 48.77 - 48.84 Mb Chr 17: 88.65 - 88.7 Mb
Pubmed search [1] [2]

The luteinizing hormone/choriogonadotropin receptor (LHCGR), also lutropin/choriogonadotropin receptor (LCGR) is a transmembrane receptor that interacts with both luteinizing hormone (LH) and chorionic gonadotropins (such as hCG in humans) and represents a G protein-coupled receptor (GPCR). It has also been called luteinizing hormone receptor (LHR). Its activation is necessary for the hormonal functioning during reproduction. LHCGRs are found in the ovary, testis, and many extragonadal tissues.

Additional recommended knowledge

Contents

LHCGR gene

The gene for the LHCGR is found on chromosome 2 p21 in humans, close to the FSH receptor gene. It consists of 70kbp (versus 54 kpb for the FSHR).[1] The gene is similar to the gene for the FSH receptor and the TSH receptor.

Receptor structure

The LHCGR consists of 674 amino acids and has a molecular mass of about 85-95 kDA based on the extent of glycolization.[2]

 

Like other GPCRs the LHCG receptor possess seven membrane-spanning domains or transmembrane helices.[3] The extracellular domain of the receptor is heavily glycosylated. These transmembrane domain contains two highly conserved cysteine residues which build disulfide bonds to stabilize the receptor structure. The transmembrane part is highly homologous with other members of the rhodopsin family of GPCRs. The C-terminal domain is intracellular and brief, rich in serine and threonine residues for possible phosphorylation.

Ligand binding and signal transduction

Upon binding LH externally to the membrane, a transduction of the signal takes place that activates the G protein that is bound to the receptor internally. With LH attached, the receptor shifts conformation and thus mechanically activates the G protein, which detaches from the receptor and activates the cAMP system.[4]

It is believed that a receptor molecule exists in a conformational equilibrium between active and inactive states. The binding of LH (or CG) to the receptor shifts the equilibrium between active and inactive receptors. LH and LH-agonists shift the equilibrium in favor of active states; LH antagonists shift the equilibrium in favor of inactive states. For a cell to respond to LH only a small percentage (~1%) of receptor sites need to be activated.

Phosphorylation by cAMP-dependent protein kinases

Cyclic AMP-dependent protein kinases (protein kinase A) are activated by the signal chain coming from the G protein (that was activated by the LHCG-receptor) via adenylate cyclase and cyclic AMP (cAMP). These protein kinases are present as tetramer with two regulatory units and two catalytic units. Upon binding of cAMP to the regulatory units, the catalytic units are released and initiate the phosphorylation of proteins leading to the physiologic action. The cyclic AMP-regulatory dimers are degraded by phosphodiesterase and release 5’AMP. DNA in the cell nucleus binds to phosphorylated proteins through the cyclic AMP response element (CRE) which results in the activation of genes.[1]

The signal is amplified by the involvement of cAMP and the resulting phosphorylation. The process is modified by prostaglandins. Other cellular regulators are participate are the intracellular calcium concentration modified by phospholipase, nitric acid, and other growth factors.


In a feedback mechanism, these activated kinases phosphorylate the receptor. The longer the receptor remains active, the more kinases are activated, the more receptors are phosphorylated.

Other pathways of signaling exist for the LHCGR.[2]

Action

Ovary

In the ovary, the LHCG receptor is necessary for follicular maturation and ovulation, as well as luteal function. Its expression requires appropriate hormonal stimulation by FSH and estradiol. The LHCGR is present on granulosa cells, theca cells, luteal cells, and interstitial cells[2] The LCGR is restimulated by increasing levels of chorionic gonadotropins in case a pregnancy is developing. In turn, luteal function is prolonged and the endocrine milieu is supportive of the nascent pregnancy.

Testis

In the male the LHCGR has been identified on the Leydig cells that are critical for testosterone production, and support spermatogenesis.

Normal LHCGR functioning is critical for male fetal development, as the fetal Leydig cells produce testosterone to induce masculinization.

Extragonadal

LHCGR have been found in many types of extragonadal tissues, and the physiologic role has remained largely unexplored. Thus receptors have been found in the uterus, sperm, seminal vesicles, prostate, skin, breast, adrenals, thyroid, neural retina, neuroendocrine cells, and (rat) brain.[2]

Receptor regulation

Upregulation

Upregulation refers to the increase in the number of receptor sites on the membrane. Estrogen and FSH upregulate LHCGR sites in preparation for ovulation. After ovulation, the luteinized ovary maintains LHCGR s that allow activation in case there is an implantation.

Desensitization

The LHCGRs become desensitized when exposed to LH for some time. A key reaction of this downregulation is the phosphorylation of the intracellular (or cytoplasmic) receptor domain by protein kinases. This process uncouples Gs protein from the LHCGR. Another way to desensitize is to uncouple the regulatory and catalytic units of the cAMP system.

Downregulation

Downregulation refers to the decrease in the number of receptor sites. This can be accomplished by metabolizing bound LHCGR sites. The bound LCGR complex is brought by lateral migration to a “coated pit” where such units are concentrated and then stabilized by a framework of clathrins. A pinched-off coated pit is internalized and degraded by lysosomes. Proteins may be metabolized or the receptor can be recycled. Use of long-acting agonists will downregulate the receptor population.

Modulators

Antibodies to LHCGR can interfere with LHCGR activity.

LHCGR abnormalities

Loss-of-function mutations in females can lead to infertility. In 46, XY individuals severe inactivation can cause male pseudohermaphroditism, as fetal Leydig cells during may not respond and induce masculinization.[5] Less severe inactivation can result in hypospadias or a micropenis.[2]

History

Alfred G. Gilman and Martin Rodbell received the 1994 Nobel Prize in Medicine and Physiology for the discovery of the G Protein System.

References

  1. ^ a b Simoni M, Gromoll J, Nieschlag E (1997). "The follicle-stimulating hormone receptor: biochemistry, molecular biology, physiology, and pathophysiology". Endocr. Rev. 18 (6): 739–73. doi:10.1210/er.18.6.739. PMID 9408742.
  2. ^ a b c d e Ascoli M, Fanelli F, Segaloff DL (2002). "The lutropin/choriogonadotropin receptor, a 2002 perspective". Endocr. Rev. 23 (2): 141–74. doi:10.1210/er.23.2.141. PMID 11943741.
  3. ^ Dufau ML (1998). "The luteinizing hormone receptor". Annu. Rev. Physiol. 60: 461–96. doi:10.1146/annurev.physiol.60.1.461. PMID 9558473.
  4. ^ Ryu KS, Gilchrist RL, Koo YB, Ji I, Ji TH (1998). "Gene, interaction, signal generation, signal divergence and signal transduction of the LH/CG receptor". International journal of gynaecology and obstetrics: the official organ of the International Federation of Gynaecology and Obstetrics 60 Suppl 1: S9–20. doi:10.1016/S0020-7292(98)80001-5. PMID 9833610.
  5. ^ Wu SM, Chan WY (1999). "Male pseudohermaphroditism due to inactivating luteinizing hormone receptor mutations". Arch. Med. Res. 30 (6): 495–500. doi:10.1016/S0188-4409(99)00074-0. PMID 10714363.

Further reading

  • Ji TH, Ryu KS, Gilchrist R, Ji I (1997). "Interaction, signal generation, signal divergence, and signal transduction of LH/CG and the receptor.". Recent Prog. Horm. Res. 52: 431-53; discussion 454. PMID 9238862.
  • Dufau ML (1998). "The luteinizing hormone receptor.". Annu. Rev. Physiol. 60: 461-96. doi:10.1146/annurev.physiol.60.1.461. PMID 9558473.
  • Ascoli M, Fanelli F, Segaloff DL (2002). "The lutropin/choriogonadotropin receptor, a 2002 perspective.". Endocr. Rev. 23 (2): 141-74. PMID 11943741.
  • Amsterdam A, Hanoch T, Dantes A, et al. (2003). "Mechanisms of gonadotropin desensitization.". Mol. Cell. Endocrinol. 187 (1-2): 69-74. PMID 11988313.
  • Fanelli F, Puett D (2003). "Structural aspects of luteinizing hormone receptor: information from molecular modeling and mutagenesis.". Endocrine 18 (3): 285-93. PMID 12450321.
  • Latronico AC, Segaloff DL (2007). "Insights learned from L457(3.43)R, an activating mutant of the human lutropin receptor.". Mol. Cell. Endocrinol. 260-262: 287-93. doi:10.1016/j.mce.2005.11.053. PMID 17055147.
  • Nagayama Y, Russo D, Wadsworth HL, et al. (1991). "Eleven amino acids (Lys-201 to Lys-211) and 9 amino acids (Gly-222 to Leu-230) in the human thyrotropin receptor are involved in ligand binding.". J. Biol. Chem. 266 (23): 14926-30. PMID 1651314.
  • Jia XC, Oikawa M, Bo M, et al. (1991). "Expression of human luteinizing hormone (LH) receptor: interaction with LH and chorionic gonadotropin from human but not equine, rat, and ovine species.". Mol. Endocrinol. 5 (6): 759-68. PMID 1922095.
  • Minegishi T, Nakamura K, Takakura Y, et al. (1990). "Cloning and sequencing of human LH/hCG receptor cDNA.". Biochem. Biophys. Res. Commun. 172 (3): 1049-54. PMID 2244890.
  • Rousseau-Merck MF, Misrahi M, Atger M, et al. (1991). "Localization of the human luteinizing hormone/choriogonadotropin receptor gene (LHCGR) to chromosome 2p21.". Cytogenet. Cell Genet. 54 (1-2): 77-9. PMID 2249480.
  • Xie YB, Wang H, Segaloff DL (1991). "Extracellular domain of lutropin/choriogonadotropin receptor expressed in transfected cells binds choriogonadotropin with high affinity.". J. Biol. Chem. 265 (35): 21411-4. PMID 2254302.
  • Frazier AL, Robbins LS, Stork PJ, et al. (1991). "Isolation of TSH and LH/CG receptor cDNAs from human thyroid: regulation by tissue specific splicing.". Mol. Endocrinol. 4 (8): 1264-76. PMID 2293030.
  • Keutmann HT, Charlesworth MC, Mason KA, et al. (1987). "A receptor-binding region in human choriogonadotropin/lutropin beta subunit.". Proc. Natl. Acad. Sci. U.S.A. 84 (7): 2038-42. PMID 3470775.
  • Atger M, Misrahi M, Sar S, et al. (1995). "Structure of the human luteinizing hormone-choriogonadotropin receptor gene: unusual promoter and 5' non-coding regions.". Mol. Cell. Endocrinol. 111 (2): 113-23. PMID 7556872.
  • Latronico AC, Anasti J, Arnhold IJ, et al. (1995). "A novel mutation of the luteinizing hormone receptor gene causing male gonadotropin-independent precocious puberty.". J. Clin. Endocrinol. Metab. 80 (8): 2490-4. PMID 7629248.
  • Shenker A, Laue L, Kosugi S, et al. (1993). "A constitutively activating mutation of the luteinizing hormone receptor in familial male precocious puberty.". Nature 365 (6447): 652-4. doi:10.1038/365652a0. PMID 7692306.
  • Yano K, Saji M, Hidaka A, et al. (1995). "A new constitutively activating point mutation in the luteinizing hormone/choriogonadotropin receptor gene in cases of male-limited precocious puberty.". J. Clin. Endocrinol. Metab. 80 (4): 1162-8. PMID 7714085.
  • Kremer H, Kraaij R, Toledo SP, et al. (1995). "Male pseudohermaphroditism due to a homozygous missense mutation of the luteinizing hormone receptor gene.". Nat. Genet. 9 (2): 160-4. doi:10.1038/ng0295-160. PMID 7719343.
  • Kosugi S, Van Dop C, Geffner ME, et al. (1995). "Characterization of heterogeneous mutations causing constitutive activation of the luteinizing hormone receptor in familial male precocious puberty.". Hum. Mol. Genet. 4 (2): 183-8. PMID 7757065.
  • Kremer H, Mariman E, Otten BJ, et al. (1994). "Cosegregation of missense mutations of the luteinizing hormone receptor gene with familial male-limited precocious puberty.". Hum. Mol. Genet. 2 (11): 1779-83. PMID 8281137.
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Luteinizing_hormone/choriogonadotropin_receptor". A list of authors is available in Wikipedia.
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