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Identification of Key Receptor Residues Discriminating Human Chorionic Gonadotropin (hCG)- and Luteinizing Hormone (LH)-Specific Signaling.

ABSTRACT: (1) The human luteinizing hormone (LH)/chorionic gonadotropin (hCG) receptor (LHCGR) discriminates its two hormone ligands and differs from the murine receptor (Lhr) in amino acid residues potentially involved in qualitative discerning of LH and hCG. The latter gonadotropin is absent in rodents. The aim of the study is to identify LHCGR residues involved in hCG/LH discrimination. (2) Eight LHCGR cDNAs were developed, carrying "murinizing" mutations on aminoacidic residues assumed to interact specifically with LH, hCG, or both. HEK293 cells expressing a mutant or the wild type receptor were treated with LH or hCG and the kinetics of cyclic adenosine monophosphate (cAMP) and phosphorylated extracellular signal-regulated kinases 1/2 (pERK1/2) activation was analyzed by bioluminescence resonance energy transfer (BRET). (3) Mutations falling within the receptor leucine reach repeat 9 and 10 (LRR9 and LRR10; K225S +T226I and R247T), of the large extracellular binding domain, are linked to loss of hormone-specific induced cAMP increase, as well as hCG-specific pERK1/2 activation, leading to a Lhr-like modulation of the LHCGR-mediated intracellular signaling pattern. These results support the hypothesis that LHCGR LRR domain is the interaction site of the hormone ?-L2 loop, which differs between LH and hCG, and might be fundamental for inducing gonadotropin-specific signals. (4) Taken together, these data identify LHCGR key residues likely evolved in the human to discriminate LH/hCG specific binding.

SUBMITTER: Lazzaretti C

PROVIDER: S-EPMC7794846 | biostudies-literature | 2020 Dec

REPOSITORIES: biostudies-literature

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Identification of Key Receptor Residues Discriminating Human Chorionic Gonadotropin (hCG)- and Luteinizing Hormone (LH)-Specific Signaling.

Lazzaretti Clara C Secco Valentina V Paradiso Elia E Sperduti Samantha S Rutz Claudia C Kreuchwig Annika A Krause Gerd G Simoni Manuela M Casarini Livio L

International journal of molecular sciences 20201225 1

(1) The human luteinizing hormone (LH)/chorionic gonadotropin (hCG) receptor (LHCGR) discriminates its two hormone ligands and differs from the murine receptor (Lhr) in amino acid residues potentially involved in qualitative discerning of LH and hCG. The latter gonadotropin is absent in rodents. The aim of the study is to identify LHCGR residues involved in hCG/LH discrimination. (2) Eight LHCGR cDNAs were developed, carrying "murinizing" mutations on aminoacidic residues assumed to interact spe ...[more]

PMID: 33375708

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Project description:BackgroundLuteinizing hormone secreted by the anterior pituitary gland regulates gonadal function. Luteinizing hormone secretion is regulated both by alterations in gonadotrope responsiveness to hypothalamic gonadotropin releasing hormone and by alterations in gonadotropin releasing hormone secretion. The mechanisms that determine gonadotrope responsiveness are unknown but may involve regulators of G protein signaling (RGSs). These proteins act by antagonizing or abbreviating interaction of Galpha proteins with effectors such as phospholipase Cbeta. Previously, we reported that gonadotropin releasing hormone-stimulated second messenger inositol trisphosphate production was inhibited when RGS3 and gonadotropin releasing hormone receptor cDNAs were co-transfected into the COS cell line. Here, we present evidence for RGS3 inhibition of gonadotropin releasing hormone-induced luteinizing hormone secretion from cultured rat pituitary cells.ResultsA truncated version of RGS3 (RGS3T = RGS3 314-519) inhibited gonadotropin releasing hormone-stimulated inositol trisphosphate production more potently than did RSG3 in gonadotropin releasing hormone receptor-bearing COS cells. An RSG3/glutathione-S-transferase fusion protein bound more 35S-Gqalpha than any other member of the G protein family tested. Adenoviral-mediated RGS3 gene transfer in pituitary gonadotropes inhibited gonadotropin releasing hormone-stimulated luteinizing hormone secretion in a dose-related fashion. Adeno-RGS3 also inhibited gonadotropin releasing hormone stimulated 3H-inositol phosphate accumulation, consistent with a molecular site of action at the Gqalpha protein.ConclusionsRGS3 inhibits gonadotropin releasing hormone-stimulated second messenger production (inositol trisphosphate) as well as luteinizing hormone secretion from rat pituitary gonadotropes apparently by binding and suppressing the transduction properties of Gqalpha protein function. A version of RGS3 that is amino-terminally truncated is even more potent than intact RGS3 at inhibiting gonadotropin releasing hormone-stimulated inositol trisphosphate production.

Project description:BackgroundThe normal physiological function of LH requires a certain concentration range, but because of pituitary desensitization, even on the day of HCG, endogenous levels of LH are low in the follicular-phase long protocol. Therefore, our study aimed to determine whether it is necessary to monitor serum LH concentrations on the day of HCG (LHHCG) and to determine whether there is an optimal LHHCG range to achieve the desired clinical outcome.MethodsA retrospective cohort study included 4502 cycles of in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) from January 1, 2016, to June 30, 2019, in a single department. The main outcome measures included retrieved eggs, available embryos, and live birth rate.ResultsThe LHHCG was divided into five groups: Group A (LH ≤ 0.5), Group B (0.5 IU/L < LH ≤ 1.2 IU/L), Group C (1.2 IU/L < LH ≤ 2.0 IU/L), Group D (2.0 IU/L < LH ≤ 5.0 IU/L), Group E (LH > 5 IU/L). In terms of the numbers of retrieved eggs (15.22 ± 5.66 vs. 13.54 ± 5.23 vs. 12.90 ± 5.05 vs. 12.30 ± 4.88 vs. 9.6 ± 4.09), diploid fertilized oocytes (9.85 ± 4.70 vs. 8.69 ± 4.41 vs. 8.39 ± 4.33 vs. 7.78 ± 3.96 vs. 5.92 ± 2.78), embryos (7.90 ± 4.48 vs. 6.83 ± 4.03 vs. 6.44 ± 3.88 vs. 6.22 ± 3.62 vs. 4.40 ± 2.55), and high-quality embryos (4.32 ± 3.71 vs. 3.97 ± 3.42 vs. 3.76 ± 3.19 vs. 3.71 ± 3.04 vs. 2.52 ± 2.27), an increase in the LHHCG level showed a trend of a gradual decrease. However, there was no significant difference in clinical outcomes among the groups (66.67% vs. 64.33% vs. 63.21% vs. 64.48% vs. 63.33%). By adjusting for confounding factors, with an increase in LHHCG, the number of retrieved eggs decreased (OR: -0.351 95%CI - 0.453-[- 0.249]).ConclusionIn the follicular-phase long protocol among young women, monitoring LHHCG is recommended in the clinical guidelines to obtain the ideal number of eggs.

Project description:LH triggers the biosynthesis of androgens in the theca-interstitial (T-I) cells of ovary through the activation of a cAMP-dependent pathway. We have previously shown that LH/human chorionic gonadotropin (hCG) activates mammalian target of rapamycin complex 1 (mTORC1) signaling network, leading to cell proliferation. In the present study, we provide evidence that the LH/hCG-mediated activation of the mTORC1 signaling cascade is involved in the regulation of steroidogenic enzymes in androgen biosynthesis. Treatment with LH/hCG increased the expression of downstream targets of mTORC1, ribosomal protein S6 kinase 1, and eukaryotic initiation factor 4E as well as steroidogenic enzymes. LH/hCG-mediated stimulation of the steroidogenic enzyme mRNA was blocked by the mTORC1 inhibitor, rapamycin. This inhibitory effect was selective because rapamycin failed to block hCG-mediated increase in the expression of Star mRNA levels. Furthermore, pharmacological targeting of mTORC1 with rapamycin also blocked LH/hCG- or forskolin-induced expression of cAMP response element-binding protein (CREB) and steroidogenic enzymes (P450 side-chain cleavage enzyme, 3?-hydroxysteroid dehydrogenase type 1, and 17?-hydroxylase/17,20 lyase) but produced no effect on steroidogenic acute regulatory protein levels. These results were further confirmed by demonstrating that the knockdown of mTOR using small interfering RNA selectively abrogated the LH/hCG-induced increase in steroidogenic enzyme expression, without affecting steroidogenic acute regulatory protein expression. LH/hCG-stimulated androgen production was also blocked by rapamycin. Furthermore, the pharmacological inhibition of mTORC1 or ribosomal protein S6 kinase 1 signaling prevented the LH/hCG-induced phosphorylation of CREB. Chromatin immunoprecipitation assays revealed the association of CREB with the proximal promoter of the Cyp17a1 gene in response to hCG, and this association was reduced by rapamycin treatment. Taken together, our findings show for the first time that LH/hCG-mediated activation of androgen biosynthesis is regulated by the mTORC1 signaling pathway in T-I cells.

Dataset Information

Identification of Key Receptor Residues Discriminating Human Chorionic Gonadotropin (hCG)- and Luteinizing Hormone (LH)-Specific Signaling.

Publications

Identification of Key Receptor Residues Discriminating Human Chorionic Gonadotropin (hCG)- and Luteinizing Hormone (LH)-Specific Signaling.

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