FSH receptor-specific residues L501 and I505 in extracellular loop 2 are essential for its function

Stable Production of a Recombinant Single-Chain Eel Follicle-Stimulating Hormone Analog in CHO DG44 Cells

This study aimed to produce single-chain recombinant Anguillid eel follicle-stimulating hormone (rec-eel FSH) analogs with high activity in Cricetulus griseus ovary DG44 (CHO DG44) cells. We recently reported that an O-linked glycosylated carboxyl-terminal peptide (CTP) of the equine chorionic gonadotropin (eCG) β-subunit contributes to high activity and time-dependent secretion in mammalian cells. We constructed a mutant (FSH-M), in which a linker including the eCG β-subunit CTP region (amino acids 115-149) was inserted between the β-subunit and α-subunit of wild-type single-chain eel FSH (FSH-wt). Plasmids containing eel FSH-wt and eel FSH-M were transfected into CHO DG44 cells, and single cells expressing each protein were isolated from 10 and 7 clones. Secretion increased gradually during the cultivation period and peaked at 4000-5000 ng/mL on day 9. The molecular weight of eel FSH-wt was 34-40 kDa, whereas that of eel FSH-M increased substantially, with two bands at 39-46 kDa. Treatment with PNGase F to remove the N glycosylation sites decreased the molecular weight remarkably to approximately 8 kDa. The EC50 value and maximal responsiveness of eel FSH-M were approximately 1.23- and 1.06-fold higher than those of eel FSH-wt, indicating that the mutant showed slightly higher biological activity. Phosphorylated extracellular-regulated kinase (pERK1/2) activation exhibited a sharp peak at 5 min, followed by a rapid decline. These findings indicate that the new rec-eel FSH molecule with the eCG β-subunit CTP linker shows potent activity and could be produced in massive quantities using the stable CHO DG44 cell system.

Stable Production of a Tethered Recombinant Eel Luteinizing Hormone Analog with High Potency in CHO DG44 Cells

We produced a recombinant eel luteinizing hormone (rec-eel LH) analog with high potency in Chinese hamster ovary DG44 (CHO DG44) cells. The tethered eel LH mutant (LH-M), which had a linker comprising the equine chorionic gonadotropin (eLH/CG) β-subunit carboxyl-terminal peptide (CTP) region (amino acids 115 to 149), was inserted between the β-subunit and α-subunit of wild-type tethered eel LH (LH-wt). Monoclonal cells transfected with the tethered eel LH-wt and eel LH-M plasmids were isolated from five to nine clones of CHO DG44 cells, respectively. The secreted quantities abruptly increased on day 3, with peak levels of 5000-7500 ng/mL on day 9. The molecular weight of tethered rec-eel LH-wt was 32-36 kDa, while that of tethered rec-eel LH-M increased to approximately 38-44 kDa, indicating the detection of two bands. Treatment with the peptide N-glycanase F decreased the molecular weight by approximately 8 kDa. The oligosaccharides at the eCG β-subunit O-linked glycosylation sites were appropriately modified post-translation. The EC50 value and maximal responsiveness of eel LH-M increased by approximately 2.90- and 1.29-fold, respectively, indicating that the mutant exhibited more potent biological activity than eel LH-wt. Phosphorylated extracellular regulated kinase (pERK1/2) activation resulted in a sharp peak 5 min after agonist treatment, with a rapid decrease thereafter. These results indicate that the new tethered rec-eel LH analog had more potent activity in cAMP response than the tethered eel LH-wt in vitro. Taken together, this new eel LH analog can be produced in large quantities using a stable CHO DG44 cell system.

Relevance of augmented kisspeptin signaling through H364 KISS1R in central precocious puberty

Understanding the pathophysiology of idiopathic central precocious puberty (ICPP) is essential, in view of its consequences on reproductive health and metabolic disorders in later life. Towards this, estimation of circulating levels of the neuropeptides, viz; Kisspeptin (Kp-10), Neurokinin B (NKB) and Neuropeptide Y (NPY), acting upstream to Gonadotropin-Releasing Hormone (GnRH), has shown promise. Insights can also be gained from functional studies on genetic variations implicated in ICPP. This study investigated the pathophysiology of ICPP in a girl by exploring the therapeutic relevance of the circulating levels of Kp-10, NKB, NPY and characterizing the nonsynonymous KISS1R variant, L364H, that she harbours, in a homozygous condition. Plasma levels of Kp-10, NKB and NPY before and after GnRH analog (GnRHa) treatment, were determined by ELISA. It was observed that GnRHa treatment resulted in suppression of circulating levels of Kp-10, NKB and NPY. Further, the H364 variant in KISS1R was generated by site directed mutagenesis. Post transient transfection of either L364 or H364 KISS1R variant in CHO cells, receptor expression was ascertained by western blotting, indirect immunofluorescence and flow cytometry. Kp-10 stimulated signalling response was also determined by phospho-ERK and inositol phosphate production. Structure-function studies revealed that, although the receptor expression in H364 KISS1R was comparable to L364 KISS1R, there was an enhanced signalling response through this variant at high doses of Kp-10. Thus, elevated levels of Kp-10, acting through H364 KISS1R, contributed to the manifestation of ICPP, providing further evidence that dysregulation of Kp-10/KISS1R axis impacts the onset of puberty.

The N-Linked Glycosylation Site N191 Is Necessary for PKA Signal Transduction in Eel Follicle-Stimulating Hormone Receptor

The follicle-stimulating hormone receptor (FSHR) contains several N-linked glycosylation sites in its extracellular region. We conducted the present study to determine whether conserved glycosylated sites in eel FSHR are necessary for cyclic adenosine monophosphate (cAMP) signal transduction. We used site-directed mutagenesis to induce four mutations (N120Q, N191Q, N272Q, and N288Q) in the N-linked glycosylation sites of eel FSHR. In the eel FSHR wild-type (wt), the cAMP response was gradually increased in a dose-dependent manner (0.01–1500 ng/mL), displaying a high response (approximately 57.5 nM/10⁴ cells) at the Rmax level. Three mutants (N120Q, N272Q, and N288Q) showed a considerably decreased signal transduction as a result of high-ligand treatment, whereas one mutant (N191Q) exhibited a completely impaired signal transduction. The expression level of the N191Q mutant was only 9.2% relative to that of the eel FSHR-wt, indicating a negligible expression level. The expression levels of the N120Q and N272Q mutants were approximately 35.9% and 24% of the FSHG-wt, respectively. The N288Q mutant had an expression level similar to that of the eel FSHR-wt, despite the mostly impaired cAMP responsiveness. The loss of the cell surface agonist-receptor complexes was very rapid in the cells expressing eel FSHR-wt and FSHR-N288Q mutants. Specifically, the N191Q mutant was completely impaired by the loss of cell surface receptors, despite treatment with a high concentration of the agonist. Therefore, we suggest that the N191 site is necessary for cAMP signal transduction. This finding implies that the cAMP response, mediated by G proteins, is directly related to the loss of cell surface receptors as a result of high-agonist treatment.

Expression Levels of Follicle-Stimulating Hormone Receptor and Implication in Diagnostic and Therapeutic Strategy of Ovarian Cancer

BACKGROUND

Follicle-stimulating hormone receptor (FSHR) has been shown to be expressed in ovarian cancer.

METHODS

Here we have summarized the potential therapeutic and diagnostic implication of FSHR in the ovarian cancers based on a review of the literature.

RESULTS

Current research indicates that FSHR comprises several variants: FSHR-1, FSHR-2, FSHR-3 and FSHR-4. Only FSHR-1 and FSHR-3 have biological roles. Although the level of FSHR differs in ovarian cancer tissues, few quantitative correlations have so far been reported on the expression levels of FSHR and carcinogenesis and progression of cancers.

CONCLUSION

A comprehensive understanding of the role of FSHR in the ovarian cancers may help the search for novel therapeutic and diagnostic regimens and improve the management of cancer patients.

Functional characterization of two naturally occurring mutations V221G and T449N in the follicle stimulating hormone receptor

Naturally occurring mutations in follicle stimulating hormone receptor (FSHR) affect the receptor function. Here, we characterized two such previously reported mutations, V²²¹G and T⁴⁴⁹N, in the extracellular domain and transmembrane helix 3, of FSHR, respectively. Functional studies with the V²²¹G mutant demonstrated an impairment in FSH binding and signaling. Validation of X-ray crystallography data indicating the contribution of FSHR specific residues in the vicinity of V²²¹ to contribute to FSH-FSHR interaction was carried out. In vitro mutational studies showed that these residues are determinants of both FSH binding and FSH induced signaling. Analysis of the T⁴⁴⁹N mutation revealed that it results in an increase in FSH binding and high cAMP response at lower doses of FSH. A marginal hCG induced and no TSH induced cAMP production was also observed. These findings corroborated with the clinical manifestations of primary amenorrhea (V²²¹G) and spontaneous ovarian hyperstimulation syndrome (T⁴⁴⁹N) in women harbouring these mutations.

Polymorphisms of the Ovine BMPR-IB, BMP-15 and FSHR and Their Associations with Litter Size in Two Chinese Indigenous Sheep Breeds

The Small Tailed Han sheep and Hu sheep are two prolific local sheep in China. In this study, the polymorphisms of BMPR-IB (Bone morphogenetic protein receptor IB), BMP-15 (Bone morphogenetic protein 15) and FSHR (follicle stimulating hormone receptor) were investigated to check whether they are associated with litter size in Small Tailed Han sheep and Hu sheep. Consequently, three polymorphisms, FecB mutation in BMPR-IB (c.746A>G), FecG mutation in BMP-15 (c.718C>T) and the mutation (g. 47C>T) in FSHR were found in the above two sheep breeds with a total number of 1630 individuals. The single marker association analysis showed that the three mutations were significantly associated with litter size. The ewes with genotype FecBB/FecBB and FecBB/FecB+ had 0.78 and 0.58 more lambs (p < 0.01) than those with genotype FecB+/FecB+, respectively. The heterozygous Han and Hu ewes with FecXG/FecX+ genotype showed 0.30 (p = 0.05) more lambs than those with the FecX+/FecX+ genotype. For FSHR gene, the ewes with genotype CC had 0.52 (p < 0.01) and 0.75 (p < 0.01) more lambs than those with genotypes TC and TT, respectively. Combined effect analyses indicated an extremely significant interaction (p < 0.01) between the random combinations of BMPR-IB, BMP-15 and FSHR genes on litter size. In addition, the Han and Hu ewes with BB/G+/CC genotype harbor the highest litter size among ewes analyzed in current study. In conclusion, BMPR-IB, BMP-15 and FSHR polymorphisms could be used as genetic markers in multi-gene pyramiding for improving litter size in sheep husbandry.

Role of the Extracellular and Intracellular Loops of Follicle-Stimulating Hormone Receptor in Its Function

Follicle-stimulating hormone receptor (FSHR) is a leucine-rich repeat containing class A G-protein coupled receptor belonging to the subfamily of glycoprotein hormone receptors (GPHRs), which includes luteinizing hormone/choriogonadotropin receptor (LH/CGR) and thyroid-stimulating hormone receptor. Its cognate ligand, follicle-stimulating hormone binds to, and activates FSHR expressed on the surface of granulosa cells of the ovary, in females, and Sertoli cells of the testis, in males, to bring about folliculogenesis and spermatogenesis, respectively. FSHR contains a large extracellular domain (ECD) consisting of leucine-rich repeats at the N-terminal end and a hinge region at the C-terminus that connects the ECD to the membrane spanning transmembrane domain (TMD). The TMD consists of seven α-helices that are connected to each other by means of three extracellular loops (ELs) and three intracellular loops (ILs) and ends in a short-cytoplasmic tail. It is well established that the ECD is the primary hormone binding domain, whereas the TMD is the signal transducing domain. However, several studies on the ELs and ILs employing site directed mutagenesis, generation of chimeric receptors and in vitro characterization of naturally occurring mutations have proven their indispensable role in FSHR function. Their role in every phase of the life cycle of the receptor like post translational modifications, cell surface trafficking, hormone binding, activation of downstream signaling, receptor phosphorylation, hormone-receptor internalization, and recycling of hormone-receptor complex have been documented. Mutations in the loops causing dysregulation of these processes lead to pathophysiological conditions. In other GPHRs as well, the loops have been convincingly shown to contribute to various aspects of receptor function. This review article attempts to summarize the extensive contributions of FSHR loops and C-terminal tail to its function.