Biological Activities of Tethered Equine Chorionic Gonadotropin (eCG) and Its Deglycosylated Mutants

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.

Systematic review of hormonal strategies to improve fertility in rams

Reviewing the current state of knowledge on reproductive performance and productive traits in rams has many advantages. First, the compilation of this information will serve as a literature resource for scientists conducting research around the world and will contribute to the understanding of the data collected and interpreted by researchers on the different hormonal strategies used to improve reproductive performance in rams. Second, it will allow scientists to identify current knowledge gaps and set future research priorities in ram reproduction. Rams play an important role in the global flock economy, but their reproductive analysis has been limited in the use of hormonal technologies to increase the productivity of sheep flocks. In this review, we cite the most important works on six hormones that, in one way or another, modify the hypothalamus-pituitary-gonadal axis, at different doses, in and out of the reproductive season, breeds, application methods, among other factors. The overall aim is to increase the reproductive efficiency of rams in different scenarios and, in some cases, of other species due to the lack of limited information on rams.

Effects of Leptin antagonist treatments on testosterone and testis histological characteristics of immature male mice

The present study aimed to ascertain how leptin antagonist injection affected testis weights, testis morphology and testosterone levels in immature male Swiss mice. Animals were administered with anti-leptin antibody subcutaneously, with or without equine chorionic gonadotropin (eCG). Control animals were treated with non-immune serum. Blood and testis were collected. The Androgen profile was analyzed in serum and tissue homogenates, and testes were histologically examined. Compared to controls, mice treated with an anti-leptin antibody with or without gonadotropins had a significant (p<0.05) increase in testis weight. Testosterone concentrations in the testis were significantly (p<0.05) higher in mice administered with anti-leptin antibody compared to control, but testosterone concentrations in blood were not affected. The diameter of seminiferous tubules, the diameter of the lumen and the width of spermatogenic cells were significantly (p<0.05) higher in mice in treatment groups compared to controls. We conclude that anti-leptin antibody administration in immature male mice increased testosterone concentrations in the testis and improved testis histological characteristics. Keywords: leptin; mouse; histology; testis; testosterone; immature male

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.

Signal Transduction of C-Terminal Phosphorylation Regions for Equine Luteinizing Hormone/Chorionic Gonadotropin Receptor (eLH/CGR)

This study aimed to investigate the signal transduction of phosphorylation sites at the carboxyl (C)-terminal region of equine luteinizing hormone/chorionic gonadotropin receptor (eLH/ CGR). The eLH/CGR has a large extracellular domain of glycoprotein hormone receptors within the G protein-coupled receptors. We constructed a mutant (eLH/CGR-t656) of eLH/ CGR, in which the C-terminal cytoplasmic tail was truncated at the Phe656 residue, through polymerase chain reaction. The eLH/CGR-t656 removed 14 potential phosphorylation sites in the intracellular C-terminal region. The plasmids were transfected into Chinese hamster ovary (CHO)-K1 and PathHunter Parental cells expressing β-arrestin, and agonist-induced cAMP responsiveness was analyzed. In CHO-K1 cells, those expressing eLH/CGR-t656 were lower than those expressing eLH/CGR wild-type (eLH/CGR-wt). The EC₅₀ of the eLH/ CGR-t656 mutant was approximately 72.2% of the expression observed in eLH/CGR-wt. The maximal response in eLH/CGR-t656 also decreased to approximately 43% of that observed in eLH/CGR-wt. However, in PathHunter Parental cells, cAMP activity and maximal response of the eLH/CGR-t656 mutant were approximately 173.5% and 100.8%, respectively, of that of eLH/CGR-wt. These results provide evidence that the signal transduction of C-terminal phosphorylation in eLH/CGR plays a pivotal role in CHO-K1 cells. The cAMP level was recovered in PathHunter Parental cells expressing β-arrestin. We suggest that the signal transduction of the C-terminal region phosphorylation sites is remarkably different depending on the cells expressing β-arrestin in CHO-K1 cells.

Specific Biological Activity of Equine Chorionic Gonadotropin (eCG) Glycosylation Sites in Cells Expressing Equine Luteinizing Hormone/CG (eLH/CG) Receptor

Equine chorionic gonadotropin (eCG), produced by the endometrial cups of the placenta after the first trimester, is a specific glycoprotein that displays dual luteinizing hormone (LH)-like and follicle-stimulating hormone (FSH)-like effects in non-equid species. However, in equidaes, eCG exhibits only LH-like activity. To identify the specific biological functions of glycosylated sites in eCG, we constructed the following site mutants of N- and O-linked glycosylation: eCGβ/αΔ56, substitution of α-subunit⁵⁶ N-linked glycosylation site; eCGβ-D/α, deletion of the O-linked glycosylation sites at the β-subunit, and eCGβ-D/αΔ56, double mutant. We produced recombinant eCG (rec-eCG) proteins in Chinese hamster ovary suspension (CHO-S) cells. We examined the biological activity of rec-eCG proteins in CHO-K1 cells expressing the eLH/CG receptor and found that signal transduction activities of deglycosylated mutants remarkably decreased. The EC₅₀ levels of eCGβ/αΔ56, eCGβ-D/α, and eCGβ-D/αΔ56 mutants decreased by 2.1-, 5.6-, and 3.4-fold, respectively, compared to that of wild-type eCG. The Rmax values of the mutants were 56%-80% those of wild-type eCG (141.9 nmol/10⁴ cells). Our results indicate that the biological activity of eCG is greatly affected by the removal of N- and O-linked glycosylation sites in cells expressing eLH/CGR. These results provide important information on rec-eCG in the regulation of specific glycosylation sites and improve our understanding of the specific biological activity of rec-eCG glycosylation sites in equidaes.

Constitutively Activating Mutants of Equine LH/CGR Constitutively Induce Signal Transduction and Inactivating Mutations Impair Biological Activity and Cell-Surface Receptor Loss In Vitro

The signal transduction of the equine lutropin/choriogonadotropin receptor (eLH/CGR) is unclear in naturally occurring activating/inactivating mutants of this receptor, which plays an important role in reproductive physiology. We undertook the present study to determine whether conserved structurally related mutations in eLH/CGR exhibit similar mechanisms of signal transduction. We constructed four constitutively activating mutants (M398T, L457R, D564G, and D578Y) and three inactivating mutants (D405N, R464H, and Y546F); measured cyclic adenosine monophosphate (cAMP) accumulation via homogeneous time-resolved fluorescence assays in Chinese hamster ovary cells; and investigated cell-surface receptor loss using an enzyme-linked immunosorbent assay in human embryonic kidney 293 cells. The eLH/CGR-L457R-, -D564G-, and -D578Y-expressing cells exhibited 16.9-, 16.4-, and 11.2-fold increases in basal cAMP response, respectively. The eLH/CGR-D405N- and R464H-expressing cells presented a completely impaired signal transduction, whereas the Y546F-expressing cells exhibited a small increase in cAMP response. The cell-surface receptor loss was 1.4- to 2.4-fold greater in the activating-mutant-expressing cells than in wild-type eLH/CGR-expressing cells, but was completely impaired in the D405N- and Y546F-expressing cells, despite treatment with a high concentration of agonist. In summary, the state of activation of eLH/CGR influenced agonist-induced cell-surface receptor loss, which was directly related to the signal transduction of constitutively activating mutants.

Roles of N-linked and O-linked glycosylation sites in the activity of equine chorionic gonadotropin in cells expressing rat luteinizing hormone/chorionic gonadotropin receptor and follicle-stimulating hormone receptor

Background

Equine chorionic gonadotropin (eCG), which comprises highly glycosylated α-subunit and β-subunit, is a unique member of the glycoprotein hormone family as it elicits both follicle-stimulating hormone (FSH)-like and luteinizing hormone (LH)-like responses in non-equid species. To examine the biological function of glycosylated sites in eCG, the following glycosylation site mutants were constructed: eCGβ/αΔ56, substitution of Asn⁵⁶ of α-subunit with Gln; eCGβ-D/α, deletion of the O-linked glycosylation site at the carboxyl-terminal peptide (CTP) region of the β-subunit; eCGβ-D/αΔ56, double mutant. The recombinant eCG (rec-eCG) mutants were expressed in Chinese hamster ovary suspension (CHO-S) cells. The FSH-like and LH-like activities of the mutants were examined using CHO-K1 cells expressing rat lutropin/CG receptor (rLH/CGR) and rat FSH receptor (rFSHR).

Results

Both rec-eCGβ/α and rec-eCGβ/αΔ56 were efficiently secreted into the CHO-S cell culture medium on day 1 post-transfection. However, the secretion of eCGβ-D/α and eCGβ-D/αΔ56, which lack approximately 12 O-linked glycosylation sites, was slightly delayed. The expression levels of all mutants were similar (200–250 mIU/mL) from days 3 to 7 post-transfection. The molecular weight of rec-eCGβ/α, rec-eCGβ/αΔ56 and rec-eCG β-D/α were in the ranges of 40–45, 37–42, and 34–36 kDa, respectively. Treatment with peptide-N-glycanase F markedly decreased the molecular weight to approximately 5–10 kDa. Rec-eCGβ/αΔ56 exhibited markedly downregulated LH-like activity. The signal transduction activity of both double mutants was completely impaired. This indicated that the glycosylation site at Asn⁵⁶ of the α-subunit plays a pivotal role in the LH-like activity of eCG. Similarly, the FSH-like activity of the mutants was markedly downregulated. eCGβ-D/α exhibited markedly downregulated LH-like and FSH-like activities.

Conclusions

Rec-eCGβ/α exhibits potent biological activity in cells expressing rLH/CGR and rFSHR. The findings of this study suggest that the LH-like and FSH-like activities of eCG are regulated by the N-linked glycosylation site at Asn⁵⁶ of the eCG α-subunit and/or by the O-linked glycosylation sites of the eCG β-subunit. These findings improved our understanding of the mechanisms underlying both LH-like and FSH-like activities of eCG.

Luteinizing hormone-like and follicle-stimulating hormone-like activities of equine chorionic gonadotropin β-subunit mutants in cells expressing rat luteinizing hormone/chorionic gonadotropin receptor and rat follicle-stimulating hormone receptor

To identify the specific region of eCG involved in FSH-like activity, the following mutant expression vectors were constructed targeting the amino acid residues 102–104 of the eCG β-subunit: single mutants, eCGβV102G/α, eCGβF103P/α, and eCGβR104K/α; double mutants, eCGβV102G;F103P/α, eCGβV102G;R104K/α, and eCGβF103P;R104K/α; triple mutant, eCGβV102G;F103P;R104K/α. The LH-like and FSH-like activities of eCG mutants were examined in CHO-K1 cells expressing rat LH/CG receptor and rat FSH receptor. The levels of eCGβV102G/α, eCGβR104K/α, and eCGβV102G;R104K/α in the culture supernatant were markedly lower than those of eCGβ/α-wt. The other mutants and rec-eCGβ/α-wt were efficiently secreted into the culture supernatant. The LH-like activities of eCGV104G/α, eCGβV102G;R104K/α, and eCGβF103P;R104K/α were approximately 61%, 52%, and 54%, respectively, of those of eCG-wt. The Rmax values of the mutants were 58.9%–78.8% those of eCG-wt with eCGβR104K/α exhibiting the lowest value. The FSH-like activities of single mutants were only 16%–20% of those of eCG-wt. Additionally, the FSH-like activity of double mutants was less than 10% of that of eCG-wt. In particular, the FSH-like activities of βV102G;R104K/α and βF103P;R104K/α were 2.5–2.9% of that of eCG-wt. These results suggest that the amino acid residues 102–104 of the eCG β-subunit are dispensable and that the residue 104 of the eCG β-subunit plays a pivotal role in signal transduction through the rat FSH receptor. Thus, these mutants may aid future studies on eCG interactions with mammalian FSH receptors in vitro and in vivo.

Comparative gene expression profiling of mouse ovaries upon stimulation with natural equine chorionic gonadotropin (N-eCG) and tethered recombinant-eCG (R-eCG)

BACKGROUND

Equine chorionic gonadotropin (eCG) induces super-ovulation in laboratory animals. Notwithstanding its extensive usage, limited information is available regarding the differences between the in vivo effects of natural eCG (N-eCG) and recombinant eCG (R-eCG). This study aimed to investigate the gene expression profiles of mouse ovaries upon stimulation with N-eCG and R-eCG produced from CHO-suspension (CHO-S) cells. R-eCG gene was constructed and transfected into CHO-S cells and quantified. Subsequently, we determined the metabolic clearance rate (MCR) of N-eCG and R-eCG up to 24 h after intravenous administration through the mice tail vein and identified differentially expressed genes in both ovarian tissues, via quantitative real-time PCR (qRT-PCR) and immunohistochemistry (IHC).

RESULTS

R-eCG was markedly expressed initially after transfection and maintained until recovery on day 9. Glycan chains were substantially modified in R-eCG protein produced from CHO-S cells and eliminated through PNGase F treatment. The MCR was higher for R-eCG than for N-eCG, and no significant difference was observed after 60 min. Notwithstanding their low concentrations, R-eCG and N-eCG were detected in the blood at 24 h post-injection. Microarray analysis of ovarian tissue revealed that 20 of 12,816 genes assessed therein were significantly up-regulated and 43 genes were down-regulated by > 2-fold in the group that received R-eCG (63 [0.49%] differentially regulated genes in total). The microarray results were concurrent with and hence validated by those of RT-PCR, qRT-PCR, and IHC analyses.

CONCLUSIONS

The present results indicate that R-eCG can be adequately produced through a cell-based expression system through post-translational modification of eCG and can induce ovulation in vivo. These results provide novel insights into the molecular mechanisms underlying the up- or down-regulation of specific ovarian genes and the production of R-eCG with enhanced biological activity in vivo.

Characterization of tethered equine chorionic gonadotropin and its deglycosylated mutants by ovulation stimulation in mice

Background

To directly assess the biological role of oligosaccharides in recombinant equine chorionic gonadotropin (rec-eCG) functioning, cDNA encoding the full-length eCGβ-subunit was fused with the mature protein part of the α-subunit, and we examined the expression levels of deglycosylated eCG mutants, the ovulation rate for deglycosylated mutants in C57BL/6 mice.

Results

The characterizations of heterodimeric and tethered mutants were studied following their respective secretions in culture medium, molecular weight and ovulation in vivo. Rec-eCG variants containing mutations at glycosylation sites at Asn82 of the α-subunit (eCGβ/αΔ82) and Asn13 of the β-subunit (eCGβΔ13/α) were not efficiently secreted into the culture medium from transfected cells. Western blot analysis revealed that the rec-eCGβ/α proteins have an approximate broad range of molecular weights of 40–46 kDa. Three rec-eCG mutants—a deglycosylated site at Asn56 of the α-subunit (eCGβ/αΔ56), a deletion of the C-terminal region of the β-subunit (eCGβ-D/α), and the double mutant (eCGβ-D/αΔ56)—turned out to have clearly lower (approximately 4–23 kDa) molecular weights. Protein N-glycosydase F (PNGase F) treatment markedly decreased the molecular weight to approximately 2–10 kDa. Normal oocytes were significantly more abundant in the natural eCG–treated group than in mutant rec-eCG–treated groups. In particular, numbers of nonfuntional oocytes were remarkably lower in all rec-eCG groups.

Conclusions

Our results indicate that the ovulation rates of oocytes are not affected by the deglycosylated rec-eCGβ/α mutant proteins. There are around 20% non-functional oocytes with natural eCG and only 2% with the rec-eCGs tested. These results provide insight into the molecular mechanisms underlying the production of rec-eCG hormones with excellent bioactivity in vivo.

Electronic supplementary material

The online version of this article (10.1186/s12896-019-0550-6) contains supplementary material, which is available to authorized users.

Site-specific roles of N-linked oligosaccharides in recombinant eel follicle-stimulating hormone for secretion and signal transduction

Eel follicle-stimulating hormone (eelFSH) is composed of a common α-subunit and a hormone specific β-subunit, both of which contain two N-linked carbohydrate residues. We characterized the biologically active single chains by fusing the α-subunit to the carboxyl terminal region of the eelFSH β-subunit. Expression vectors were constructed and the biological activity of the recombinant hormones (rec-hormones) was characterized using Chinese hamster ovary (CHO) K1 cells expressing the eelFSH receptor gene. Mutagenesis of the individual and double glycosylated sites was performed to determine the functions of the oligosaccharide chains on signal transduction. The absence of the Asn²² (eelFSHβΔ22/α) and Asn^5.22 (eelFSHβΔ5.22/α) N-linked oligosaccharide chain in the eelFSH β-subunit completely reduced the secretion level in the medium and cell lysate of CHO-K1 cells. The expression levels of eelFSHβ/α wild-type in CHO suspension (CHO-S) cells was approximately 4-fold higher in CHO-k1 cells. The molecular weight of rec-eelFSHβ/α wild-type by western blotting analysis was found to be 34 kDa. Mutants (β/αΔ56, β/αΔ79, and βΔ5/α) lacking single oligosaccharide sites showed molecular weights that were reduced by approximately 10%. The digestion of N-linked oligosaccharides using PNGaseF treatment showed that the molecular weights of all mutants were reduced to 27-kDa. The oligosaccharide chains in rec-eelFSHβ/α wild-type were modified to a molecular weight of approximately 7-10 kDa in CHO-K1 and CHO-S cells. Oligosaccharide site deletions at positions Asn⁵⁶ and Asn⁷⁹ on the α-subunit and Asn⁵ on the β-subunit were found to play an essential role in cAMP signal transduction through the eelFSH receptor. The EC₅₀ values of Asn⁵⁶ and Asn⁵ resulted in a significant decrease in potency to 64% and 53% of the wild type, respectively. Specifically, the removal of the carbohydrates at Asn⁷⁹ of the α-subunit (β/αΔ79) was drastically reduced to 53.8% of the wild-type levels in maximum response. These results have allowed for the identification of the site-specific roles of carbohydrate residues in eel FSH. Our data suggest that N-linked oligosaccharide chains play a pivotal role in biological activity through the eelFSH receptor as suggested in similar studies of other mammalian FSH hormones.

Site specificity of eel luteinizing hormone N-linked oligosaccharides in signal transduction

Eel luteinizing hormone (eelLH) is composed of a common α-subunit and hormone specific β-subunit, both of which contain asparagine-linked carbohydrate residues, located at positions 56 and 79 on the α-subunit and position 10 on the β-subunit. The specific roles of the individual carbohydrate chains are poorly defined in eel. Thus, we characterized the biologically active single chains by fusing the α-subunit to the carboxyl terminal region of the eelLH β-subunit. Site-directed mutagenesis of the three N-linked glycosylation sites was performed to examine the function of individual glycosylation sites in secretion and signal transduction. The absence of the Asn⁷⁹N-linked sugar chain slightly reduced secretion in Chinese hamster ovary (CHO) cells. The expression of eelLHβ/α (wild-type) in CHO suspension cells was increased by approximately 2-fold higher than that of attached CHO cells. By western blotting analysis, the molecular weight of wild-type was found to be 32 kDa. Mutants (β/α△56, β/α△79, and β△10/α) of the oligosaccharide chain at a single site showed molecular weights that were reduced by approximately 10%. However, the double mutant (β/α△56.79) molecular weight was decreased by more than 20% compared to the wild-type. Enzymatic digestion of oligosaccharides using PNGaseF treatment showed that the molecular weights of all mutants, including wild-type, were reduced to 25 kDa. The results obtained in the absence of carbohydrates at Asn⁵⁶ of the α-subunit and at Asn¹⁰ of the β-subunit revealed their roles in signal transduction through the eelLH receptor. The EC₅₀ value of the cAMP response at Asn⁷⁹ of the α-subunit was increased by 5-fold, whereas the maximum response was dramatically reduced to 17.8% of wild-type levels. Specifically, removal of the carbohydrates at double mutant (β/α△56.79) is approximately 85% to wild-type levels in biopotency. These results revealed the site-specific roles of eelLH carbohydrate residues. Our data suggest that N-linked oligosaccharide chains play a pivotal role in biological activity through the eelLH receptor.

The C-terminal Phosphorylation Sites of eel Follicle-Stimulating Hormone Receptor are Important Role in the Signal Transduction

The large extracellular domain of glycoprotein hormone receptors is a unique feature within the G protein-coupled receptors (GPCRs) family. After interaction with the hormone, the receptor becomes coupled to Gs, which, in turn stimulates adenylyl cyclase and the production of cAMP. Potential phosphorylation sites exist in the C-terminal region of GPCRs. The experiments described herein represent attempts to determine the functions of the eel follicle-stimulating hormone receptor (eelFSHR). We constructed a mutant of eelFSHR, in which the C-terminal cytoplasmic tail was truncated at residue 614 (eelFSHR-t614). The eelFSHR-t614 lacked all potential phosphorylation sites present in the C-terminal region of eelFSHR. In order to obtain the eelFSHR ligand, we produced recombinant follicle-stimulating hormone (rec-eelFSHβ/α) in the CHO-suspension cells. The expression level was 2-3 times higher than that of the transient expression of eelFSH in attached CHO-K1 cells. The molecular weight of the rec-eelFSHβ/α protein was identified to be approximately 34 kDa. The cells expressing eelFSHR-t614 showed an increase in agonist-induced cAMP responsiveness. The maximal cAMP responses of cells expressing eelFSHR-t614 were lower than those of cells expressing eelFSHR-wild type (eelFSHR-WT). The EC₅₀ following C-terminal deletion in CHO-K1 cells was approximately 60.4% of that of eelFSHR-WT. The maximal response in eelFSHR-t614 cells was also drastically lower than that of eelFSHR-WT. We also found similar results in PathHunter Parental cells expressing β-arrestin. Thus, these data provide evidence that the truncation of the C-terminal cytoplasmic tail phosphorylation sites in the eelFSHR greatly decreased cAMP responsiveness and maximal response in both CHO-K1 cells and PathHunter Parental cells expressing β-arrestin.

Signal Transduction of Eel Luteinizing Hormone Receptor (eelLHR) and Follicle Stimulating Hormone Receptor (eelFSHR) by Recombinant Equine Chorionic Gonadotropin (rec-eCG) and Native eCG

Previous studies showed that recombinant equine chorionic gonadotropin (rec-eCGβ/α) exhibits both follicle-stimulating hormone (FSH) and luteinizing hormone (LH)-like activities in rat LHR- and FSHR-expressing cells. In this study, we analyzed signal transduction by eelFSHR and eelLHR upon stimulation with rec-eCGβ/α and native eCG. The cyclic adenosine monophosphate (cAMP) stimulation in CHO-K1 cells expressing eelLHR was determined upon exposure to different doses (0-1,450 ng/mL) of rec-eCGβ/α and native eCG. The EC₅₀ values of rec-eCGβ/α and native eCG were 172.4 and 786.6 ng/mL, respectively. The activity of rec-eCGβ/α was higher than that of native eCG. However, signal transduction in the CHO PathHunter Parental cells expressing eelFSHR was not enhanced by stimulation with both agonist rec-eCGβ/α and native eCG. We concluded that rec-eCGβ/α and native eCG were completely active in cells expressing eelLHR, similar to the activity in the mammalian cells expressing LHRs. However, rec-eCGβ/α and native eCG did not invoke any signaling response in the cells expressing eelFSHR. These results suggest that eCG has a potent activity in cells expressing eelLHR. Thus, we also suggest that rec-eCGβ/α can induce eel maturation by administering gonadotropic reagents (LH), such as salmon pituitary extract.

Internalization of Rat FSH and LH/CG Receptors by rec-eCG in CHO-K1 Cells

Equine chorionic gonadotropin (eCG) is a unique molecule that elicits the response characteristics of both follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in other species. Previous studies from this laboratory had demonstrated that recombinant eCG (rec-eCG) from Chinese hamster ovary (CHO-K1) cells exhibited both FSH- and LH-like activity in rat granulosa and Leydig cells. In this study, we analyzed receptor internalization through rec-eCGs, wild type eCG (eCGβ/α) and mutant eCG (eCGβ/αΔ56) with an N-linked oligosaccharide at Asn⁵⁶ of the α-subunit. Both the rec-eCGs were obtained from CHO-K1 cells. The agonist activation of receptors was analyzed by measuring stimulation time and concentrations of rec-eCGs. Internalization values in the stably selected rat follicle-stimulating hormone receptor (rFSHR) and rat luteinizing/chorionic gonadotropin receptor (rLH/CGR) were highest at 50 min after stimulation with 10 ng of rec-eCGβ/α. The dose-dependent response was highest when 10 ng of rec-eCGβ/α was used. The deglycosylated eCGβ/αΔ56 mutant did not enhance the agonist-stimulated internalization. We concluded that the state of activation of rFSHR and rLH/CGR could be modulated through agonist-stimulated internalization. Our results suggested that the eLH/CGRs are mostly internalized within 60 min by agonist-stimulation by rec-eCG. We also suggested that the lack of responsiveness of the deglycosylated eCGβ/ αΔ56 was likely because the site of glycosylation played a pivotal role in agonist-stimulated internalization in cells expressing rFSHR and rLH/CGR.

Production and characterization of monoclonal antibodies against recombinant tethered follicle-stimulating hormone from Japanese eel Anguilla japonica

We prepared monoclonal antibodies (mAbs) against a recombinant tethered follicle-stimulating hormone (rec-FSH) from Japanese eel Anguilla japonica that was produced in Escherichia coli. Positive hybridomas (clones eFA-C5, eFA-C10, eFA-C11, eFA-C12, eFA-C13, and eFB-C14) were selected by using the eel FSH antigen in ELISA, and anti-eel FSH mAbs were purified from culture supernatants by performing affinity chromatography. Three of the 6mAbs were characterized and their isotypes were identified as IgG2b (eFA-C5 and eFA-C11) and IgG1 (eFB-C14). In western blotting assays, the mAbs recognized the antigen as a 24.3-kDa band, and further detected bands of 34 and 32kDa in the supernatants of CHO cells transfected with cDNA encoding tethered eel FSHβ/α and LHβ/α, respectively. PNase F-mediated deglycosylation of the recombinant proteins resulted in a drastic reduction in their molecular weight, to 7-9kDa. The mAbs eFA-C5 and eFA-C11 recognized the eel FSHα-subunit that is commonly encoded among glycoprotein hormones, whereas eFB-C14 recognized the eel FSHβ-subunit, and immunohistochemical analysis revealed that the staining by these mAbs was specifically localized in the eel pituitary. We also established an ELISA system for detecting rec-tethered FSHβ/α and LHβ/α produced from CHO cell lines. Measurement of biological activities in vitro revealed that only weak activity of rec-FSHβ/α was detected. The activity of rec-LHβ/α was found to be increased in a dose-dependent manner for eel oocyte maturation.

Data on the characterization of follicle-stimulating hormone monoclonal antibodies and localization in Japanese eel pituitary

Monoclonal antibodies were generated against recombinant follicle-stimulating hormone (rec-FSH) from Japanese eel Anguilla japonica; rec-FSH was produced in Escherichia coli and purified using Ni-NTA Sepharose column chromatography.

In support of our recent publication, "Production and characterization of monoclonal antibodies against recombinant tethered follicle-stimulating hormone from Japanese eel Anguilla japonica" [1], it was important to characterize the specificity of eel follicle-stimulating hormone antibodies. Here, the production and ELISA system of these monoclonal antibodies are presented. The affinity-purified monoclonal antibodies specifically detected eel rec-FSH in ELISA and on western blots of rec-FSH produced from CHO cells. Immunohistochemical analysis revealed that FSH staining was specifically localized in the eel pituitary.

The transcription factor Ap-1 regulates monkey 20α-hydroxysteroid dehydrogenase promoter activity in CHO cells

Background

Monkey 20α-hydroxysteroid dehydrogenase (20α-HSD) is a catabolic enzyme responsible for converting progesterone into biologically inactive 20α-hydroxyprogesterone, thereby playing a key role in the estrous cycle or pregnancy and allowing ovulation and parturition to occur in most mammalian animals. Monkey 20α-HSD was highly abundant in ovarian and placental tissues during the pre-ovulation and pre-parturition phase and was primarily localized in the syncytiotrophoblast of the placenta. In this study, we focused on the molecular characterization of the monkey 20α-HSD promoter region by conducting reporter assays in Chinese hamster ovary (CHO) K1 cells.

Results

A reporter assay using constructs of various lengths of the 5′-flanking region (-890-Luc, -513-Luc, -306-Luc, -273-Luc, and -70-Luc) revealed that a region corresponding to the activator protein 1 (Ap-1) located between -281 and -274 bp was essential for the transcriptional activity. Absence of the Ap-1 site in -273-Luc dramatically decreased the transcription levels to the control levels. When the reporter constructs were co-transfected with Ap-1 (Jun) and specificity protein (Sp-1) genes, the transcription activities of the constructs increased with the exception of -273 and -70, while that of the double construct was reduced compared to that of Ap-1 alone. Furthermore, mutational analysis demonstrated that a putative Ap-1 site played an important role in the expression of the reporter gene. These findings were confirmed by EMSA examining the interactions of the protein Ap-1 in a nuclear extract from CHO-K1 cells and the expression levels of the Ap-1 transcription factor in pre-parturition placenta and CHO-K1 cells. Although mut-1 and mut-2 of Ap-1 bound with nuclear extracts from CHO-K1 cells, the transcriptional activity of mut-3 was almost completely suppressed.

Conclusions

Our results indicate that the Ap-1 site (-281 → -274) (5′-TGTCTCAT-3′) plays a crucial role in the activation of the monkey 20α-HSD gene. Thus, we demonstrated that monkey 20α-HSD promoter activity is regulated by the transcription factor Ap-1 in CHO-K1 cells.

Ovarian and placental expression of 20α-hydroxysteroid dehydrogenase during pregnancy in deer

The enzyme 20α-hydroxysteroid dehydrogenase (20α-HSD) catalyzes the conversion of progesterone to its inactive form, 20α-hydroxyprogesterone. This enzyme has been shown to play a critical role in the regulation of luteal function in experimental animals. In this study, we cloned and expressed the gene encoding elk deer 20α-HSD from reproductive placental and ovarian tissues. PCR, 3'- and 5'-RACE, and northern blot analysis were performed for the cloning and characterization of deer 20α-HSD gene. We expressed recombinant deer 20α-HSD protein and used western blot analysis to determine protein expression levels in the placenta and ovary during pregnancy. The full cDNA sequence of 20α-HSD was used to clone an open reading frame encoding 323 amino acids and consisting of 1142 bp. The nucleotide sequence of deer 20α-HSD showed high homology with the sequences of the bovine (96%), goat (96%), and human (83%) 20α-HSD genes. 20α-HSD mRNA was strongly expressed in the placenta on days 30, 60, and 70 of pregnancy. A high level of the protein was also detected in the placenta but not in fetal skin tissue. The recombinant 20α-HSD protein produced in mammalian cells and bacterial systems had a molecular weight of approximately 37-kDa. The deer 20α-HSD protein signal was specifically localized in the basal part of the primary chorionic villi and chorionic stem villus of the placenta during early pregnancy. The 20α-HSD protein was also intensively localized in the larger luteal cells of the corpus luteum during pregnancy.

Aberrant phenotypes of transgenic mice expressing dimeric human erythropoietin

BACKGROUND

Dimeric human erythropoietin (dHuEPO) peptides are reported to exhibit significantly higher biological activity than the monomeric form of recombinant EPO. The objective of this study was to produce transgenic (tg) mice expressing dHuEPO and to investigate the characteristics of these mice.

METHODS

A dHuEPO-expressing vector under the control of the goat beta-casein promoter, which produced a dimer of human EPO molecules linked by a 2-amino acid peptide linker (Asp-Ile), was constructed and injected into 1-cell fertilized embryos by microinjection. Mice were screened using genomic DNA samples obtained from tail biopsies. Blood samples were obtained by heart puncture using heparinized tubes, and hematologic parameters were assessed. Using the microarray analysis tool, we analyzed differences in gene expression in the spleens of tg and control mice.

RESULTS

A high rate of spontaneous abortion or death of the offspring was observed in the recipients of dHuEPO embryos. We obtained 3 founder lines (#4, #11, and #47) of tg mice expressing the dHuEPO gene. However, only one founder line showed stable germline integration and transmission, subsequently establishing the only transgenic line (#11). We obtained 2 F1 mice and 3 F2 mice from line #11. The dHuEPO protein could not be obtained because of repeated spontaneous abortions in the tg mice. Tg mice exhibited symptoms such as short lifespan and abnormal blood composition. The red blood cell count, white blood cell count, and hematocrit levels in the tg mice were remarkably higher than those in the control mice. The spleens of the tg mice (F1 and F2 females) were 11- and -21-fold larger than those of the control mice. Microarray analysis revealed 2,672 spleen-derived candidate genes; more genes were downregulated than upregulated (849/764). Reverse transcriptase-polymerase chain reaction (RT-PCR) and quantitative real-time PCR (qRT-PCR) were used for validating the results of the microarray analysis of mRNA expression.

CONCLUSIONS

In conclusion, dHuEPO tg mice caused excessive erythrocytosis that led to abnormal blood composition, short lifespan, and abnormal splenomegaly. Further, we identified 2,672 genes associated with splenomegaly by microarray analysis. These results could be useful in the development of dHuEPO-producing tg animals.

Expression of aldo-keto reductase family 1 member C1 (AKR1C1) gene in porcine ovary and uterine endometrium during the estrous cycle and pregnancy

BACKGROUND

The aldo-keto reductase family 1 member C1 (AKR1C1) belongs to a superfamily of NADPH-dependent reductases that convert a wide range of substrates, including carbohydrates, steroid hormones, and endogenous prostaglandins. The 20 alpha-hydroxysteroid dehydrogenase (20 alpha-HSD) is a member of AKR family. The aims of this study were to determine its expression in the ovary and uterus endometrium during the estrous cycle and pregnancy.

METHODS

Rapid amplification of cDNA ends (RACE) experiments were performed to obtain the 5' and 3' ends of the porcine 20 alpha-HSD cDNA. Reverse-transcriptase-PCR (RT-PCR), real-time PCR, northern blot analysis, and western blot analysis were performed to examine the expression of porcine 20 alpha-HSD. Immunohistochemical analysis was also performed to determine the localization in the ovary.

RESULTS

The porcine 20 alpha-HSD cDNA is 957 bp in length and encodes a protein of 319 amino acids. The cloned cDNA was virtually the same as the porcine AKR1C1 gene (337 amino acids) reported recently, and only differed in the C-terminal region (the AKR1C1 gene has a longer C-terminal region than our sequence). The 20 alpha-HSD gene (from now on referred to as AKR1C1) cloned in this paper encodes a deletion of 4 amino acids, compared with the C-terminal region of AKR1C1 genes from other animals. Porcine AKR1C1 mRNA was expressed on day 5, 10, 12, 15 of the cycle and 0-60 of pregnancy in the ovary. The mRNA was also specifically detected in the uterine endometrium on day 30 of pregnancy. Western blot analysis indicated that the pattern of AKR1C1 protein in the ovary during the estrous cycle and uterus during early pregnancy was similar to that of AKR1C1 mRNA expression. The recombinant protein produced in CHO cells was detected at approximately 37 kDa. Immunohistochemical analysis also revealed that pig AKR1C1 protein was localized in the large luteal cells in the early stages of the estrous cycle and before parturition.

CONCLUSIONS

Our study demonstrated that AKR1C1 mRNA and protein are coordinately expressed in the luteal cell of ovary throughout the estrous cycle and in the uterus on day 30 of pregnancy. Thus, the porcine AKR1C1 gene might control important mechanisms during the estrous cycle.

Molecular characterization of bovine placental and ovarian 20α-hydroxysteroid dehydrogenase

The enzyme 20α-hydroxysteroid dehydrogenase (20α-HSD) catalyzes the conversion of progesterone to its inactive form, 20α-hydroxyprogesterone. This enzyme plays a critical role in the regulation of luteal function in female mammals. In this study, we conducted the characterization and functional analyses of bovine 20α-HSD from placental and ovarian tissues. The nucleotide sequence of bovine 20α-HSD showed significant homology to that of goats (96%), humans (84%), rabbits (83%), and mice (81%). The mRNA levels increased gradually throughout the estrous cycle, the highest being in the corpus luteum (CL) 1 stage. Northern blot analysis revealed a 1.2 kb mRNA in the bovine placental and ovarian tissues. An antibody specific to bovine 20α-HSD was generated in a rabbit immunized with the purified, recombinant protein. Recombinant 20α-HSD protein produced in mammalian cells had a molecular weight of ∼37 kDa. Bacterially expressed bovine 20α-HSD protein showed enzymatic activity. The expression pattern of the 20α-HSD protein in the pre-parturition placenta and the CL1 stage of the estrous cycle was similar to the level of 20α-HSD mRNA expression. Immunohistochemical analysis also revealed that bovine 20α-HSD protein was intensively localized in the large luteal cells during the late estrous cycle.

Ectopic expression of tethered human follicle-stimulating hormone (hFSH) gene in transgenic mice

To determine whether the mammary gland can be used to secrete large quantities of a bioactive heterodimeric protein into milk, we used a bovine beta-casein promoter to target and express human follicle-stimulating hormone (hFSH) in the mammary gland into the milk of transgenic mice. We also identified the effects of hFSH leaked into the bloodstream. Transgenic mice produced a high level (up to 300 mIU/ml) of recombinant hFSH in the mammary gland. Human FSH was expressed in the mammary gland and brain, as determined by reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry. In vitro bioactivity was also identified by cyclic AMP (cAMP) assay. The highest activity was showed in the transgenic mice line 11. However, hFSH leaked into the bloodstream was a powerful factor in the generation of breast and ovarian tumors from the transgenic mice line 11. These results suggest that change of endogenous hormones (FSH and progesterone) may affect the morphology and blood cell counts of peripheral blood and, especially, provoke breast and ovarian tumors.