• Korean Journal of Animal Reproduction
• /
• v.26 no.3
• /
• pp.299-308
• /
• 2002

In horse, a single gene encodes both eCG and eLH $\beta$ subunits. The difference between eCG and eLH lies in the structure of their glycoresidues, which are both sialylated and sulfated in LH and sialylated in CG eCG consists of highly glycosyiated $\alpha$- and $\beta$-subunits and is an unique member of the gonadotropin family because it elicits response characteristics of both FSH and LH in other species than the horse. This dual activity of eCG in heterologous species is of fundamental interest to the study of gonadotropin structure-function relationships and the understanding of the molecular bases of the specific interactions of these hormones with their receptors. Thus, eCG is a dintinct molecule from the view points of its biological function and glycoresidue structures. The oligosaccharide at Asn 56 of the $\alpha$-subunit plays an indispensable role, whereas the carboxyl-terminal extension of the eCG $\beta$-subunit with its associated O-linked oligosaccharides is not improtant for, the in vitro LH-like activity of eCG. In contrast, both N- and O-linked oligosaccharides play important roles for FSH-like activity and increase FSH-like activity by removal of N- and O-linked oligosaccharides. Therefore, the dual LH- and FSH-like activities of eCG can be clearly separated by removal of either the N-linked oligosaccharide on the $\alpha$-subunit or CTP-associated O-linked oligosaccharides from its $\beta$-subunit. The glycoresidues seem to play crucial roles fer biological activities. The tethered-eCG was effciently secreted and showed similar LH-like activity to the dimeric eCG $\alpha$/ $\beta$ and native eCG. FSH-like activity of the tethered-eCG was also shown similarly in comparison with the native and wild type eCG $\alpha$/ $\beta$. Our data for the first time suggest that the tethered-eCG can be expressed efficiently and the produced product by the CHO-Kl cells is fully LH- and FSH-like activities in rat in vitro bioassay system. Our results also suggest that this molecular can imply particular models ot FSH-like activity not LH-like activity in the eCG. Taken together, these data indicate that the constructs of tethered molecule will be useful in the study of mutants that affect subunit association and/or secretion.

• Journal of Life Science
• /
• v.11 no.2
• /
• pp.103-107
• /
• 2001

The equine chorionic gonadotropin (eCG) subunits $\alpha$ and ${\beta}$ are transcribed from different genes and associate noncovalently to form the bioactive eCG heterodimer. Dimerization is rate limiting for eCG secretion, and dissociation leads to hormone inactivation. The correct conformation of the heterodimer is alto important for efficient secretion, hormone-specific post-translational modifications, receptor binding and signal transduction. To determine whether ${\alpha}$ and ${\beta}$ subunits can be synthesized as a single polypeptide chain (tethered-eCG) and also display biological activity, the tethered-eCG molecule by fusing the carboxyl terminus of the eCG ${\beta}$-subunit to the amino terminus of the af-subunit was construe-ted and transfected into chinese hamster ovary (CHO-Kl) cells. LH- and FSH-like activities were assayed in terms of testosterone production and aromatase activity in primary cultured rat Leydig cells and granulosa cells, respectively. The tethered-eCG was efficiently secreted and showed similar LH-like activity to the dimeric eCG ${\alpha}$/${\beta}$ and native eCG. FSH-like activity of the tethered-eCG was also shown similarly in comparison with the native and wild type eCG ${\alpha}$/${\beta}$. Our data for the first time suggest that the tethered-eCG can be expressed efficiently and the produced product by the CHO-K1 cells is fully LH- and FSH-like activities in rat in vitro bioassay system. Our results also suggest that this molecular can imply particular models of FSH-like activity not LH-like activity in the eCG. Taken together, these data indicate that the constructs of tethered molecule will be useful in the study of mutants that affect subunit association and/or secretion.

• Reproductive and Developmental Biology
• /
• v.34 no.1
• /
• pp.33-40
• /
• 2010

Equine chorionic gonadotropin (eCG) is a heavily glycosylated glycoprotein composed of non-covalently linked $\alpha$- and $\beta$-subunits. To study the function and signal transduction of tethered recombinant-eCG (rec-eCG), a single chain eCG molecule was constructed, and the rec-eCG protein was prepared. In this study, we constructed 5 mutants (${\Delta}1$, ${\Delta}2$, ${\Delta}3$, ${\Delta}4$, and ${\Delta}5$) of rec-eCG using data about known glycoprotein hormones to analyze the role of specific follicle stimulating homone (FSH)-like activity. Three amino acids of certain specific sites were replaced with alanine. The expression vectors were transfected into CHO cells and subjected to G418 selection for 2~3 weeks. The media were collected and the quantity of secreted tethered rec-eCGs was quantified by ELISA. The LH- and FSH-like activities were assayed in terms of cAMP production by rat LH/CG and rat FSH receptors. Then, the metabolic clearance rate analyzed by the injection of rec-eCG (5 IU) into the tail vein was analyzed. The mutant eCGs (${\Delta}l$, ${\Delta}4$, and ${\Delta}5$) were transcripted, but not translated into proteins. Rec-eCG A2 was secreted in much lower amounts than the wild type. Only the rec-eCG ${\Delta}3$ ($\beta$-subunit: $Gln^{94}-Ile^{95}-Lys^{96}{\rightarrow}Ala^{94}-Ala^{95}-Ala^{96}$) was efficiently secreted. Although activity is low, its LH-like activity was similar to that of tethered $eCG{\beta\alpha}$. However, the FSH-like activity of rec-$eCG{\beta\alpha\Delta}3$ was completely flat. The result of the analysis of the metabolic clearance rate shoed the persistence of the mutant in the blood until 4 hours after the injection. After then, it almost disappeared at 8 hours. Taken together, these data suggest that 94~96 amino acid sequences in eCG $\beta$-subunit appear to be of utmost importance for signal transduction of the FSH receptor.

• Reproductive and Developmental Biology
• /
• v.34 no.1
• /
• pp.47-53
• /
• 2010

Glycoprotein hormones have a common $\alpha$-subunit that is involved in the signaling pathway together with G protein, adenylcyclase and cAMP induction; however, it is an unclear how this common structure is related to hormonal action. To determine the biological functions of the COOH-terminal amino acids in the $\alpha$-subunit of these glycoprotein hormones, a tethered-molecule was constructed by fusing the $NH_2$-terminus of the $\alpha$-subunit to the COOH-terminus of the $\beta$-subunit of equine chorionic gonadotropin (eCG). The following deletion mutants were created by PCR; Ile was inserted at position 96 to form ${\Delta}96$, Lys was substituted at position 95 to form ${\Delta}95$, His was inserted at position 93 to form ${\Delta}93$ and Tyr was substituted at position 87 to form ${\Delta}87$. Each mutant was transfected into CHO-K1 cells. Tethered-wt eCG, and ${\Delta}96$, ${\Delta}95$, and ${\Delta}93$ mutants were efficiently secreted into the medium but the ${\Delta}87$ mutant was not secreted. Interestingly, the RT-PCR, real-time PCR, and northern blot analyses confirmed that the RNA was transcribed in the ${\Delta}87$ mutant. However, the ${\Delta}87$ mutant protein was not detected in the medium or the intracellular fraction of the cell lysates. The LH- and FSH-like activities of the recombinant proteins were assayed in terms of cAMP production using rat LH/CG and rat FSH receptors. The metabolic clearance rate (MCR) was determined by injecting rec-eCG (2 IU) into the tail vein. The ${\Delta}95$ and ${\Delta}93$ mutants were completely inactive in both the LH- and FSH-like activity assays. The ${\Delta}96$ mutant showed slight activity in the LH-like activity assay. In comparison to the wild type, the activity of the ${\Delta}96$ mutant in the FSH-like activity assay was the highest among all the mutants. The MCR assay in which rec-eCG was injected showed a peak at 10 min in all the treatment groups, which disappeared 4 h after injection. These results imply a direct interaction between the receptor and the COOH-terminal region of the a-subunit. The data also reveal a significant difference in the mechanism by which the eCG hormone interacts with the rLH and rFSH receptors. The COOH-terminal region of the $\alpha$-subunit is very important for the secretion and functioning of this hormone.

• Proceedings of the KSAR Conference
• /
• 2000.10a
• /
• pp.10-12
• /
• 2000

Members of the glycoprotein family, which includes CG, LH, FSH and TSH, comprise two noncovalently linked $\alpha$- and $\beta$-subunits. Equine chorionic gonadotropin (eCG), known as PMSG, has a number of interesting and unique characteristics since it appears to be a single molecule that possesses both LH- and FSH-like activities in other species than the horse. This dual activity of eCG in heterologous species is of fundamental interest to the study of the structure-function relationships of gonadotropins and their receptors. CG and LH $\beta$ genes are different in primates. In horse, however, a single gene encodes both eCG and eLH $\beta$-subunits. The subunit mRNA levels seem to be independently regulated and their imbalance may account for differences in the quantities of $\alpha$ - and $\beta$ -subunits in the placenta and pituitary. The dual activities of eCG could be separated by removal of the N-linked oligosaccharide on the $\alpha$-subunit Asn 56 or CTP-associated O-linked oligosaccharides. The tethered-eCG was. efficiently secreted and showed similar LH-like activity to the dimeric eCG. Interestingly, the FSH-like activity of the tethered-eCG was increased markedly in comparison with the native and wild type eCG. These results also suggest that this molecular can implay particular models of FSH-like activity not LH-like activity in the eCG/indicate that the constructs of tethered molecule will be useful in the study of mutants that affect subunit association and/or secretion. A single-chain analog can also be constructed to include additional hormone-specific bioactive generating potentially efficacious compounds that have only FSH-like activity. The LH/CG receptor (LH/CGR), a membrane glycoprotein that is present on testicular Leydig cells and ovarian theca, granulosa, luteal, and interstitial cells, plays a pivotal role in the regulation of gonadal development and function in males as well as in nonpregnant and pregnant females. The LH/CGR is a member of the family of G protein-coupled receptors and its structure is predicted to consist of a large extracellular domain connected to a bundle of seven membrane-spanning a-helices. The LH/CGR phosphorylation can be induced with a phorbol ester, but not with a calcium ionophore. The truncated form of LHR also was down-regulated normally in response to hCG stimulation. In contrast, the cell lines expressing LHR-t63I or LHR-628, the two phosphorylation-negative receptor mutant, showed a delay in the early phase of hCG-induced desensitization, a complete loss of PMA-induced desensitization, and an increase in the rate of hCG-induced receptor down-regulation. These results clearly show that residues 632-653 in the C-terminal tail of the LHR are involved in PMA-induced desensitization, hCG-induced desensitization, and hCG-induced down-regulation. Recently, constitutively activating mutations of the receptor have been identified that are associated with familial male-precocious puberty. Cells expressing LHR-D556Y bind hCG with normal affinity, exhibit a 25-fold increase in basal cAMP and respond to hCG with a normal increase in cAMP accumulation. This mutation enhances the internalization of the free and agonist-occupied receptors ~2- and ~17-fold, respectively. We conclude that the state of activation of the LHR can modulate its basal and/or agonist-stimulated internalization. Since the internalization of hCG is involved in the termination of hCG actions, we suggest that the lack of responsiveness detected in cells expressing LHR-L435R is due to the fast rate of internalization of the bound hCG. This statement is supported by the finding that hCG responsiveness is restored when the cells are lysed and signal transduction is measured in a subcellular fraction (membranes) that cannot internalize the bound hormone.

• Korean Journal of Animal Reproduction
• /
• v.24 no.4
• /
• pp.357-364
• /
• 2000

Members of the glycoprotein family, which includes CG, LH, FSH and TSH, comprise two noncovalently linked $\alpha$- and $\beta$-subunits. Equine chorionic gonadotropin (eCG), known as PMSG, has a number of interesting and unique characteristics since it appears to be a single molecule that possesses both LH- and FSH-like activities in other species than the horse. This dual activity of eCG in heterologous species is of fundamental interest to the study of the structure-function relationships of gonadotropins and their receptors. CG and LH $\beta$ genes are different in primates. In horse, however, a single gene encodes both eCG and eLH $\beta$ -subunits. The subunit mRNA levels seem to be independently regulated and their imbalance may account for differences in the quantities of $\alpha$ - and $\beta$-subunits in the placenta and pituitary. The dual activities of eCG could be separated by removal of the N-linked oligosaccharide on the $\alpha$-subunit Asn 56 or CTP-associated O-linked oligosaccharides. The tethered-eCG was efficiently secreted and showed similar LH-like activity to the dimeric eCG. Interestingly, the FSH-like activity of the tethered-eCG was increased markedly in comparison with the native and wild type eCG. These results also suggest that this molecular can implay particular models of FSH-like activity not LH-like activity in the eCG/indicate that the constructs of tethered molecule will be useful in the study of mutants that affect subunit association and/or secretion. A single-chain analog can also be constructed to include additional hormone-specific bioactive generating potentially efficacious compounds that have only FSH-like activity. The LH/CG receptor (LH/CGR), a membrane glycoprotein that is present on testicular Leydig cells and ovarian theca, granulosa, luteal, and interstitial cells, plays a pivotal role in the regulation of gonadal development and function in males as well as in nonpregnant and pregnant females. The LH/CGR is a member of the family of G protein-coupled receptors and its structure is predicted to of a large extracellular domain connected to a bundle of seven membrane-spanning a-helices. The LH/CGR phosphorylation can be induced with a phorbol ester, but not with a calcium ionophore. The truncated form of LHR also was down-regulated normally in response to hCG stimulation. In contrast, the cell lines expressing LHR-t631 or LHR-628, the two phosphorylation-negative receptor mutant, showed a delay in the early phase of hCG-induced desensitization, a complete loss of PMA-induced desensitization, and an increase in the rate of hCG-induced receptor down-regulation. These results clearly show that residues 632~653 in the C-terminal tail of the LHR are involved in PMA-induced desensitization, hCG-induced desensitization, and hCG-induced down-regulation. Recently, constitutively activating mutations of the receptor have been identified that are associated with familial male-precocious puberty. Cells expressing LHR-D556Y bind hCG with normal affinity, exhibit a 25-fold increase in basal cAMP and respond to hCG with a normal increase in cAMP accumulation. This mutation enhances the internalization of the free and agoinst-occupied receptors ~2- and ~17- fold, respectively. We conclude that the state of activation of the LHR can modulate its basal and/or agonist-stimulated internalization. Since the internalization of hCG is involved in the termination of hCG actions, we suggest that the lack of responsiveness detected in cells expressing LHR-L435R is due to the fast rate of internalization of the bound hCG. This statement is supported by the finding that hCG responsiveness is restored when the cells are lysed and signal transduction is measured in a subcellular fraction (membranes) that cannot internalize the bound hormone.

• Advances in Traditional Medicine
• /
• v.6 no.2
• /
• pp.86-95
• /
• 2006

The ethanol extract of the Crotalaria juncea seeds, which showed promising antispermatogenic and antiandrogenic activities in albino mice, was taken up further for the isolation of the active fractions present in it. Two fractions that were obtained from thin layer chromatography were subjected for testing to know their antispermatogenic and antiandrogenic activities. After preliminary trials the fraction I showed maximum antifertility activity at the dose level of 200 mg/kg body weight when administered orally to the rats for 50 days. The fraction I was found to affect spermatogenesis as well as the endocrine functions of the testis as indicated by gravimetric, histopathological and biochemical changes. Further this fraction has caused degenerative changes in the seminiferous tubules and Leydig cells of the testis. The accessory reproductive organs like epididymis, seminal vesicles, vas deferens, prostrate, Cowper's gland and Levator Ani muscle showed significant malfunction. Cauda epididymal sperm count and sperm motility were reduced significantly. The treatment has also resulted in increase in the cholesterol level and alkaline phosphatase activity, and decrease in protein, glycogen, sialic acid contents and acid phosphatase activity in testis. It is noteworthy that RIA studies have shown significant reduction in serum FSH, LH and testosterone. Scanning electron microscopic observations revealed abnormalities in sperm structure.

• Development and Reproduction
• /
• v.25 no.4
• /
• pp.199-211
• /
• 2021

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.

• Korean Journal of Animal Reproduction
• /
• v.24 no.2
• /
• pp.125-142
• /
• 2000

13). Analysis of a purified preparation of eCG revealed that its $\beta$ -subunit consists of 149 amino acids, which was confirmed by the molecular cloning of its cDNA. There seem to be at least four to six, or even as many as 11, O-glycosylation sites on the extended C-tenninal region of the eCG $\beta$-subunit. Interestingly, eCG is a unique member of this family, as it appear to be a single molecule that possesses both LH- and FSH-like activities. Using the cDNA prepared from mRNA extracted from equine placental and pituitary tissues, we cloned the cDNA of eCG $\alpha$- and $\beta$ -subunits and eFSH $\beta$ -subunit. The mRNA expression of each subunit seems to be independently regulated, which may account for differences in the quantities of $\alpha$ - and $\beta$ -subunits in the placenta and pituitary. Thus, eCG is a distinct molecule from the view points of its biological function and glycoresidue structures. Recombinant eCGs including the mutants which lack oligosaccharides will be useful tools for analyzing the structure-function relationships of gonadotropins in the horse as well as other species. Similar experiments will also clarify the proposed structure and biological functions for the glycoprotein hormones. These experimental are now possible, and hopefully a resolution of the existing controversy will be forthcoming in the near future.

• Development and Reproduction
• /
• v.22 no.1
• /
• pp.55-64
• /
• 2018

Previous studies showed that recombinant equine chorionic gonadotropin ($rec-eCG{\beta}/{\alpha}$) 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 $rec-eCG{\beta}/{\alpha}$ 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 $rec-eCG{\beta}/{\alpha}$ and native eCG. The $EC_{50$ values of $rec-eCG{\beta}/{\alpha}$ and native eCG were 172.4 and 786.6 ng/mL, respectively. The activity of $rec-eCG{\beta}/{\alpha}$ 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 $rec-eCG{\beta}/{\alpha}$ and native eCG. We concluded that $rec-eCG{\beta}/{\alpha}$ and native eCG were completely active in cells expressing eelLHR, similar to the activity in the mammalian cells expressing LHRs. However, $rec-eCG{\beta}/{\alpha}$ 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 $rec-eCG{\beta}/{\alpha}$ can induce eel maturation by administering gonadotropic reagents (LH), such as salmon pituitary extract.