In this study, we analyzed signal transduction by equine follicle-stimulating hormone receptor (eFSHR) on stimulation with recombinant eelFSHβ/α (rec-eelFSHβ/α), natural porcine FSH (pFSH), and natural human FSH (hFSH). cAMP stimulation in CHO-K1 cells expressing eFSHR was determined upon exposure to different doses (0-1450 ng/mL) of these hormones. The EC50 value of rec-eelFSHβ/α was 53.35 ng/mL. The Rmax values of rec-eelFSHβ/α and pFSH were 28.12 and 2.88 ng/mL, respectively. The activity of rec-eelFSHβ/α was much higher than that of natural pFSH. However, signal transduction in CHO PathHunter Parental cells expressing eFSHR was not enhanced by stimulation with natural hFSH. Thus, rec-eelFSHβ/α was completely active in cells expressing eFSHR. However, natural hFSH did not invoke a signal response in cells expressing eFSHR. Particularly, natural pFSH was weakly active in the same cells. These results showed that eelFSHβ/α has potent activity in cells expressing eFSHR. Thus, rec-eelFSHβ/α may efficiently bind to eFSHR, where as natural hFSH does not bind to eFSHR.

The glycoprotein hormone family consists of follicle-stimulating hormone (FSH; GTH1), luteinizing hormone (LH; GTH2), and thyroid-stimulating hormone (TSH), which are secreted by the pituitary gland in all mammalian species, and chorionic gonadotropin, which is secreted by placental trophoblast cells in primates and equids. These hormones consist of non-covalently associated α-, β- subunits. Within a species, the amino acid sequence of α-subunit is identical across all glycoprotein hormones and is encoded by a single gene. The αβ dimer is the active form of the hormone, and biological specificity is conferred by the β-subunit. Both of α and β subunit of eel FSH has two N-glycosylation sites (α-subunit: Asn56 and Asn79; β -subunit: Asn5 and Asn22, respectively). In the present study, we constructed deglycosylated mutants at single and double sites in each subunits of eel FSH for identification of Asn linked oligosaccharides' biological role. Mutant cDANs were cloned into pcDNA3 expression vector and transiently transfected into CHO suspension cells. The quantity of rec-eelFSHs were quantified by sandwich ELISA system, using monoclonal antibodies produced in our lab. The wild type rec-FSH protein was detected at the predicted molecular weight of 34 kDa by western blot. The molecular weight of deglycosylated mutants at single site decreased with about 4 kDa and of mutants at double sites decreased with 8 kDa. After PNGase treatment in the rec-eel FSH proteins, molecular weight also decreased to 7-8 kDa. We generated stably parental cell lines, engineered to express a β-arrestin 2EA fusion protein, expressing eel FSHR and C-terminal deleted mutant. 2 out of 5 receptor cells each were selected by G-418 and we tested these cell lines in a receptor functionality using PathHunter β arrestin assay (DiscoverX). Follicle stimulating hormone acts through binding to its specific receptor. Binding of ligand to the receptor activates the adenosine 3',5'-cyclic monophosphate (cAMP) pathway (McFarland et al., 1989; Ji and Ji, 1991a; Rose, 1998) and the inositol 1phosphate (IP1) the second messenger systems. After stimulation of eelFSH receptor stably transfected Parental CHO cells with FSH wild type and mutant hormones as a ligand, production of cAMP and IP-1 were evaluated (Cisbio). cAMP IC-50 values by eelFSHwt; αΔ56; αΔ79; αΔ56_79; and βΔ5 were 33.1; 1154.7; 22; 410 and 311.9 ng/ml, respectively. IP-1 IC-50 values by eelFSHwt; αΔ56; αΔ79; αΔ56_79 and βΔ5 were 6.8; 7.1; 4.4; 3.8 and 10.2 ng/ml, respectively too. The cAMP activation was greatly decreased in the αΔ56αmutant. Thus, the site of α56 oligosaccharide in the eel plays an pivotal role for the cAMP stimulation using eel FSH receptor cell lines. In the IP-one assay, the activity in the αΔ56 and βΔ5 mutants was a little decreased than the wt. The biological roles of N-linked oligosaccharides in GPCR internalization are going to be estimated by measuring β arrestin recruitment system.

Soluble-NSF attachment protein receptor (SNARE) proteins play a role in vesicle fusion, exocytosis, and intracellular trafficking in neuronal cells as well as in fertilization and embryogenesis. We investigated the expression patterns of two SNARE proteins, SNAP-25 and synaptotagmin VII (SytVII), and their regulation by pregnant mare serum gonadotropin (PMSG) during mouse ovarian follicular development. Ovaries were obtained at 0, 12, 24, 36, and 48 h post-PMSG injection of immature mice. SNAP-25 and SytVII mRNA expression levels increased gradually in a time-dependant manner. However, protein levels revealed different patterns of expression, suggesting different translational regulation following PMSG stimulation. SNAP-25 and SytVII expression was closely associated with thickening of the granulosa cell (GC) layer and follicle morphological changes from a flattened to a cuboidal shape. To explore follicle stimulating hormone receptor (FSHR)-mediated regulation of their expression, GCs from preantral follicles were cultured to examine the effects of FSHR siRNA knockdown. FSHR siRNA abolished upregulation of the SNAREs in both PMSG and FSH-stimulated GCs. This abolished gene expression was rescued by adding dibutyryl cyclic AMP to the cultures. These results suggest that SNAP-25 and SytVII expression is regulated via the FSHR-cAMP pathway during follicular development.

In ultrastructure study of testis, Sertoli cells start to differentiate at 16 days of gestation. Transcripts of FSH receptor, IGF-I receptor, ER receptor and androgen receptor were highly and initially expressed at 16 day of gestation. As results of in situ PCR at 16 day of gestation, transcripts of FSH, IGF-I receptor were detected in Sertoli cells and spermatogonia, whereas the receptors of and androgen were detected in Sertoli cells. Therefore, expression of FSH and estrogen androgen, IGF-I and could play an important role during fetal and prepubertal testicular development by stage specific manner in mouse.