Human Luteinizing Hormone Receptor Research Articles

SAT649 Org43553, The First Low-molecular-weight Agonist Of The Human Luteinizing Hormone Receptor Induces Leanness And Energy Expenditure In Mice

Abstract Disclosure: D. Lizneva: None. A. Gumerova: None. K. Ievleva: None. O. Barak: None. F. Korkmaz: None. J. Gimenez Roig: None. T. Frolinger: None. G. Pevnev: None. F. Sultana: None. N. Kramskiy: None. S. Wizman: None. M. Orloff: None. A.R. Pallapati: None. S. Rojekar: None. V. Ryu: None. O. Moldavski: None. T. Yuen: None. M. Zaidi: None. We provide compelling evidence that LH is a pro–lean hormone, and that ORG43553, the first low-molecular-weight agonist of the luteinizing hormone receptor (LHCGR) induces leanness and promotes energy expenditure in mice. We detected Lhcgr transcripts in white adipose tissue (WAT) depots in male and female C57BL/6 mice (qPCR, IHC, RNAscope, Sanger sequencing), but not in Lhcgr-/- mice. Intraperitoneal AlexaFluor-488–labeled hCG bound to gonadal and subcutaneous fat pads in wild type mice, but not in Lhcgr-/- mice. Following i.v. 89Zr–LH injection, radioactivity was detected in mesenteric, inguinal and gonadal WAT. LH, hCG and ORG43553 rapidly induced ERK1/2 phosphorylation in differentiated 3T3.L1 cells. Female and male Lhcgr+/- mice on normal chow and high–fat diet, respectively, became obese, importantly, without changes in sex steroids. The gene–dosage effect of Lhcgr depletion suggests a dominant physiologic action of LH on body composition. 14–week–old male C57BL/6 mice were fed on high–fat diet and injected, i.p., with LH, hCG or vehicle, twice–a–week, for 6 weeks. Both LH and hCG markedly reduced body fat accrual (qNMR) but triggered a rise in serum testosterone. The hCG–induced lean phenotype persisted despite androgen receptor blockade by flutamide—confirming that the pro–lean actions of LH and hCG were largely independent of testosterone. Furthermore that LH failed to inhibit fat accrual in Lhcgr-/- mice testified to its action via the LHCGR. Injection of ORG43553 into male C57BL/6 mice for 9 weeks caused a significant reduction in fat mass (qNMR), with reduced WAT weight in fat depots. Remarkably, serum testosterone remained unchanged confirming that the anti–adiposity effect of ORG43553 was independent of testosterone. To study the mechanism of LHCGR activation on body fat, 3T3.L1 adipocytes were treated with hCG or ORG43553 for 12 hours. This resulted in reduced oil droplet accumulation. 3T3-L1–derived organoids treated with LH, hCG or ORG43553 also displayed a substantial reduction in the differentiated layer compared to vehicle–treated organoids. To study whether, in addition to reducing adipocyte differentiation, LHCGR agonism also enhanced thermogenesis, 3T3-L1 adipocytes were pretreated with ORG43553 for 1 hour before measuring oxygen consumption rate (OCR) on a Seahorse Xf96 Analyzer. ORG43553 increased OCR at baseline and upon oligomycin exposure, indicating mitochondria proton leak (thermogenesis). To confirm increased energy expenditure in vivo, mice were injected, s.c., with ORG43553 or vehicle. Oxygen consumption (VO2) and energy expenditure (EE) increased acutely in ORG43553–treated mice, with no change in locomotor activity. The findings suggest that ORG45335, which has been tested in humans for infertility, can potentially become a candidate drug for obesity. Presentation: Saturday, June 17, 2023

Cell-Surface Loss of Constitutive Activating and Inactivating Mutants of Eel Luteinizing Hormone Receptors

The present study aimed to investigate the mechanism of cell surface receptor loss by two constitutively activating mutants (designated L469R, and D590Y) and two inactivating mutants (D417N and Y558F) of the luteinizing hormone receptor (LHR) in the Japanese eel Anguilla japonica, known to naturally occur in human LHR transmembrane domains. We investigated cell surface receptor loss using an enzyme-linked immunosorbent assay in HEK 293 cells. The expression level of wild-type eel LHR was considered to be 100%, and the expression levels of L469R and D417N were 97% and 101%, respectively, whereas the expression levels of D590Y and Y558F slightly increased to approximately 110% and 106%, respectively. The constitutively activating mutants L469R and D590Y exhibited a decrease in cell surface loss in a manner similar to that of wild-type eel LHR. The rates of loss of cell surface agonist-receptor complexes were observed to be very rapid (2.6-6.2 min) in both the wild-type eel LHR and activating mutants. However, cell surface receptor loss in the cells expressing inactivating mutants D417N and Y558F was slightly observed in the cells expressing inactivating mutants D417N and Y558F, despite treatment with a high concentration of agonist. These results provide important information on LHR function in fish and the regulation of mutations of highly conserved amino acids in glycoprotein hormone receptors.

P–139 The role of hormones and LH receptor expression of granulosa cells collected from large and small follicles in natural/minimal stimulation cycle IVF

Abstract Study question Do different follicle sizes influence gonadotropins (LH, FSH) and sex steroid (estradiol) in follicular fluids and LH receptor expression (LHCGR) in cumulus oocyte complexes (COCs)? Summary answer It was found that differences in levels of FSH, estradiol values and LHCGR mRNA expression level in COCs between small and large follicles. What is known already The maturity rate in oocytes of small follicle is significantly lower compared to that of large follicles. Study design, size, duration After obtaining written consents from 78 infertile patients, we aspirated the large (>15 mm) and small (<5 mm) follicles, and collected follicular fluids at oocyte retrieval. Participants/materials, setting, methods We measured levels of LH, FSH and estradiol by enzyme immunoassay from large and small follicular fluids after oocytes retrievals. All collected oocytes were distinguished from large and small follicles, we confirmed the maturity of retrieved oocytes by the presence of first polar body. Then we extracted total RNA from granulosa cells and measured mRNA expression of LHCGR, encoding the human LH receptor, by quantitative real-time PCR. Each value was normalized to ACTB mRNA levels. Main results and the role of chance LH levels were nearly equal between small and large follicles (P = 0.8356). Whereas FSH and estradiol levels were significantly lower in small follicles (P < 0.0001). The expression levels of LHCGR mRNA were significantly lower in small follicles than in large follicles during natural cycles. The maturity rate in oocytes of small follicle was significantly lower compared to that of large follicles (96.0% vs. 21.7%, P < 0001). Limitations, reasons for caution The main limitation of the present study was collected by 42 natural cycles and 36 mild stimulation cycles with letrozole following low-dose clomiphene. Wider implications of the findings: In spite of almost the same LH levels between two groups, the reason why the significantly lower maturation rates of oocytes collected from small follicles is poor LHCGR mRNA expression due to insufficient granulosa cells glowth because of low FSH and estradiol levels. Trial registration number Not applicable

Discovery of BAY-298 and BAY-899: Tetrahydro-1,6-naphthyridine-Based, Potent, and Selective Antagonists of the Luteinizing Hormone Receptor Which Reduce Sex Hormone Levels in Vivo.

The human luteinizing hormone receptor (hLH-R) is a member of the glycoprotein hormone family of G-protein-coupled receptors (GPCRs), activated by luteinizing hormone (hLH) and essentially involved in the regulation of sex hormone production. Thus, hLH-R represents a valid target for the treatment of sex hormone-dependent cancers and diseases (polycystic ovary syndrome, uterine fibroids, endometriosis) as well as contraception. Screening of the Bayer compound library led to the discovery of tetrahydrothienopyridine derivatives as novel, small-molecule (SMOL) hLH-R inhibitors and to the development of BAY-298, the first nanomolar hLH-R antagonist reducing sex hormone levels in vivo. Further optimization of physicochemical, pharmacokinetic, and safety parameters led to the identification of BAY-899 with an improved in vitro profile and proven efficacy in vivo. BAY-298 and BAY-899 serve as valuable tool compounds to study hLH-R signaling in vitro and to interfere with the production of sex hormones in vivo.

Vitreous Levels of Luteinizing Hormone and VEGF are Strongly Correlated in Healthy Mammalian Eyes

ABSTRACTPurpose/Aim: Luteinizing hormone (LH) is known to function as a key regulator of vascular endothelial growth factor (VEGF) expression in reproductive organs. In recent years, LH has also been detected in human vitreous and LH receptors have been identified in human retina. This study was aimed to investigate a potential correlation between LH and VEGF levels in healthy mammalian eyes to provide supporting evidence of LH’s potential involvement in intraocular VEGF regulation.Methods: 18 bovine and 30 porcine eyes were procured from an abattoir and VEGF and LH levels were measured in the vitreous extracted from these eyes by commercially available bovine & porcine ELISA assay kits. Total protein of the vitreous was measured by using Micro BSA protein assay kit.Results: After total protein normalization, the Pearson Correlation Coefficients (PCC) showed a strong and significant correlation between LH and VEGF levels. (Bovine LH/VEGF PCC: 0.89, p < 0.001; Porcine LH/VEGF PCC: 0.80, p < 0.001). Linear regression analyses, adjusted for gender, showed significant linear relationships between LH and VEGF levels in both bovine and porcine vitreous. (Bovine: t-value = 7.69, p < 0.0001, adjusted r2 = .79; Porcine: t-value = 6.71, p < 0.001, adjusted r2 = .62)Conclusions: We show that VEGF and LH are strongly correlated in healthy, adult mammalian eyes. The robustness of the correlation is shown both by its strength of association and reproducibility in two species. Given that LH is well known to regulate VEGF levels in several tissue types, the LH/VEGF linear relationship in vitreous potentially implicates LH in homeostatic VEGF regulation of the eye. Because we also found that the correlation between LH and VEGF only became manifest when our targeted analytes were normalized by total amount of protein, preclinical and clinical investigators should consider normalizing analytes in vitreous by total protein when assessing potential correlations among them.

Loss-of-Function Mutations in the Human Luteinizing Hormone Receptor Predominantly Cause Intracellular Retention.

Mutations in G protein-coupled receptors (GPCRs) have been identified for many endocrine hormone signaling deficiencies. Inactivating mutations can impair ligand binding, receptor activation/coupling to signaling pathways, or can cause receptor misfolding and consequent impaired expression at the cell membrane. Here we examine the cell surface expression, ligand binding, and signaling of a range of mutant human luteinizing hormone receptors (LHRs) identified as causing reproductive dysfunction in human patients. The data obtained reveal how mutations in GPCRs can have diverse and severely deleterious effects on receptor function. Furthermore, it was found that impaired functionality of the majority of the mutant LHRs was due to reduced expression at the cell surface (14/20) while only two mutations caused impaired binding affinity and two impaired in signaling. An additional two mutations were found to cause no impairment of receptor function. These data demonstrate that the majority of LHR mutations lead to intracellular retention and highlight the potential for novel pharmacological chaperone therapeutics that can "rescue" expression/function of retained mutant GPCRs.

Luteinizing Hormone Receptors are Confined in Mesoscale Plasma Membrane Microdomains Throughout Recovery from Receptor Desensitization

We examined the involvement of membrane microdomains during human luteinizing hormone (LH) receptor recovery from receptor desensitization after removal of bound hormone. Lateral motions of individual desensitized LH receptors expressed on the surface of Chinese hamster ovary cells and transient association of these receptors with detergent-resistant membrane (DRM) microdomains isolated using isopycnic sucrose gradient ultracentrifugation were assessed. Single particle tracking experiments showed untreated individual LH receptors to be confined within cell-surface membrane compartments with an average diameter of 199 ± 17 nm and associated with membrane fractions characteristic of bulk plasma membrane. After brief exposure to human chorionic gonadotropin (hCG), LH receptors remained for several hours desensitized to hCG challenge. Throughout this period, significantly increased numbers of LH receptors were confined within smaller diameter (<120 nm) membrane compartments and associated with DRM fragments of characteristically low density. By 5 h, when cells again produced cAMP in response to hCG, unoccupied LH receptors were found in larger 169 ± 22 nm diameter cell-surface membrane compartments and >90 % of LH receptors were again found in high-density membrane fragments characteristic of bulk plasma membrane. Taken together, these results suggest that, during recovery from LH receptor desensitization, LH receptors are both located with DRM lipid environments and confined within small, mesoscale (80-160 nm) cell-surface compartments. This may reflect hormone-driven translocation of receptors into DRM and formation there of protein aggregates too large or too rigid to permit effective signaling. Once bound hormone is removed, receptor structures would have to dissociate before receptors can again signal effectively in response to hormone challenge. Moreover, such larger protein complexes would be more easily constrained laterally by membrane structural elements and so appear resident in smaller cell-surface compartments.

Precocious Puberty and Leydig Cell Hyperplasia in Male Mice With a Gain of Function Mutation in the LH Receptor Gene

The LH receptor (LHR) is critical for steroidogenesis and gametogenesis. Its essential role is underscored by the developmental and reproductive abnormalities that occur due to genetic mutations identified in the human LHR. In males, activating mutations are associated with precocious puberty and Leydig cell hyperplasia. To generate a mouse model for the human disease, we have introduced an aspartic acid to glycine mutation in amino acid residue 582 (D582G) of the mouse LHR gene corresponding to the most common D578G mutation found in boys with familial male-limited precocious puberty (FMPP). In transfected cells, mouse D582G mLHR exhibited constitutive activity with a 23-fold increase in basal cAMP levels compared with the wild-type receptor. A temporal study of male mice from 7 days to 24 weeks indicated that the knock-in mice with the mutated receptor (KiLHR(D582G)) exhibited precocious puberty with elevated testosterone levels as early as 7 days of age and through adulthood. Leydig cell-specific genes encoding LHR and several steroidogenic enzymes were up-regulated in KiLHR(D582G) testis. Leydig cell hyperplasia was detected at all ages, whereas Sertoli and germ cell development appeared normal. A novel finding from our studies, not previously reported in the FMPP cases, is that extensive hyperplasia is commonly found around the periphery of the testis. We further demonstrate that the hyperplasia is due to premature proliferation and precocious differentiation of adult Leydig cells in the KiLHR(D582G) testis. The KiLHR(D582G) mice provide a mouse model for FMPP, and we suggest that it is a useful model for studying pathologies associated with altered LHR signaling.

3D-QSAR Modeling of Non-peptide Antagonists for the Human Luteinizing Hormone-releasing Hormone Receptor

The application of ligand-based drug design methods such as quantitative structure-activity relationship (QSAR) is a mandatory issue in the design of luteinizing hormone-releasing hormone (LHRH) receptor antagonists because the lack of information on the molecular structure for this target protein. The relationship between the structures and the antagonistic activities of 128 non-peptide antagonists for the LHRH receptor were modeled by using the classic QSAR methods comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA). The best model included CoMSIA steric, electrostatic, hydrophobic and hydrogen bond donor fields, had a Q2 value of 0.780 and predicted adequately the activity of external compounds. The tridimensional contour maps generated were used to identify the key structural requirements responsible for a high biological activity of the compounds. These features should represent the ligand features involved in interactions with the target protein that modulate their potency as antagonists.

Inactivating Mutations of the Human Luteinizing Hormone Receptor in Both Sexes

The human luteinizing hormone/chorionic gonadotropin receptor (LHCGR) plays a fundamental role in male and female reproductive physiology. Over the past 15 years, several homozygous or compound heterozygous loss-of-function mutations in the LHCGR gene have been described in males and females. In genetic males, mutations in LHCGR were associated with distinct degrees of impairment in pre- and postnatal testosterone secretion resulting in a phenotypic spectrum. Patients with the severe form of LH resistance have predominantly female external genitalia and absence of secondary sex differentiation at puberty. Patients with milder forms have predominantly male external genitalia with micropenis and/or hypospadias or only infertility without ambiguity. The undermasculization is associated with low basal, as well as human CG-stimulated, testosterone levels and elevated LH levels after pubertal age, without abnormal step-up in testosterone biosynthesis precursors. The testes have only slightly reduced size but mature Leydig cells are absent or scarce (Leydig cell hypoplasia). Genetic females with inactivating LHCGR mutations have female external genitalia, spontaneous breast and pubic hair development at puberty, and normal or late menarche followed by oligoamenorrhea and infertility. Estradiol and progesterone levels are normal for the early to midfollicular phase, but do not reach ovulatory or luteal phase levels. Serum LH levels are high whereas follicle-stimulating hormone levels are normal or only slightly increased. Pelvic ultrasound has demonstrated a small or normal uterus and normal or enlarged ovaries with cysts. The inactivating mutations of the LHCGR have provided important insights into distinct physiological roles of LH in reproduction of both sexes.

Precocious Puberty, Elevated Steroidogenesis, and Leydig Cell Hyperplasia in Male Mice with a Gain of Function Mutation in the Luteinizing Hormone Receptor Gene.

The activation of the luteinizing hormone receptor (LHR) in the gonads by luteinizing hormone (LH) is critical for steroidogenesis and gametogenesis. Several activating mutations in human LHR have been identified in boys with sporadic or familial male limited precocious puberty (FMPP) or testotoxicosis. Boys with this mutation present with elevated levels of testosterone in the context of prepubertal LH levels, the onset of puberty by age four or earlier and Leydig cell hyperplasia. The majority of the activating mutations are in transmembrane helix 6 of the 7 transmembrane G protein-coupled receptor, the most common being a mutation of aspartic acid 578 to glycine. We have created a knock-in mouse (KiLHR) with an activating point mutation, caused by substitution of glycine for aspartic acid at position 582 (D582G) in mouse LHR, corresponding to the common D578G mutation in human LHR. In this study, we have examined the effects of the mutated LHR on reproductive and metabolic function in male KiLHR mice. RT-PCR analysis of RNA from multiple tissues of heterozygous KiLHR mice demonstrated expression of the WT and mutant alleles only in the gonads and brain. Male KiLHR mice exhibited precocious puberty as evidenced by premature balanopreputial separation at postnatal day 14.5 compared to 22.4 days for WT mice and presence of major urinary proteins (MUPs), which are secreted at the onset of puberty, in KiLHR mice at postnatal day 15 compared to day 22 in WT mice. KiLHR mice were fertile. Male KiLHR mice were analyzed at neonatal (7 and10d), prepubertal (2 and 3 weeks), pubertal (6 weeks) and adult (12 and 24 weeks) ages. Hormonal analysis indicated that the KiLHR mice had significantly elevated serum and testicular testosterone levels as early as postnatal day 7 and remained elevated through adulthood. No significant difference was seen in serum estradiol levels; however testicular estradiol levels were elevated in KiLHR mice compared to WT mice. Gonadotropin levels were decreased in KiLHR compared to WT mice. Expression of the steroidogenic enzyme genes was upregulated as early as 7 days consistent with the elevated testosterone levels. The levels of LHR mRNA were significantly upregulated at all ages, but not those of the follicle stimulating hormone or steroid hormone receptors. Histological analysis revealed premature Leydig cell proliferation and the presence of Leydig cell hyperplasia as early as 7 days of age. Gene expression analysis suggested the precocious development of adult Leydig cells. At 24 weeks, Leydig cell adenomas were apparent is some of the KiLHR mice. However, there were no apparent differences in testicular germ cell or Sertoli cell development. KiLHR mice at 24 weeks of age exhibited impaired glucose tolerance compared to WT mice although there was no difference in fasting glucose or insulin levels. No changes in body weight or body fat were measured between the genotypes. The overall phenotype of precocious puberty, elevated testosterone and Leydig cell hyperplasia in the KiLHR male mice is similar to that seen in humans with FMPP. These studies suggest that the KiLHR mice will be a novel model to understand the effects of premature LHR activation during early Leydig cell development as well as the consequences of chronic elevated testosterone levels on adult testicular and metabolic function. Supported by NIH HD044119.

Functional study of an aberrant splicing variant of the human luteinizing hormone (LH) receptor

The luteinizing hormone receptor (LHR) is a member of a subfamily of G protein-coupled receptors that is characterized by its alternative splicing. In a previous study, we identified a splice site mutation of intron 6 (IVS6-3C>A) in a patient suffering from Leydig cell hypoplasia, which leads to aberrant splicing of LHR mRNA. In vitro expression analysis confirmed that this mutation results in the skipping of exon 7 in the mature mRNA of the LHR gene. In this study, we determined the impact of IVS6-3C>A on the RNA secondary structure and function of LHR-Del7. The three-dimensional structure of the leucine-rich repeats in LHR was predicted by molecular modeling. Radioactive ligand-binding assays verified that LHR-Del7 has no binding affinity for hCG. Furthermore, we detected negligible cAMP production in cells transfected with LHR-Del7. Cells co-expressing LHR-WT and LHR-Del7 were able to generate cAMP in response to hCG, but there was no significant difference between cells transfected with LHR-WT/vector and LHR-WT/LHR-Del7, although the variant was able to localize to cell surface, similar to wild-type receptor. These results indicated that LHR-Del7 does not have a dominant negative effect on LHR-WT cell surface expression, and although the pathological splicing variant LHR-Del7 was able to localize to cell membranes it failed to bind hCG and had no effect on wild-type LHR.

Restricted Lateral Diffusion of Luteinizing Hormone Receptors in Membrane Microdomains

Single particle tracking was used to evaluate lateral motions of individual FLAG-tagged human luteinizing hormone (LH) receptors expressed on CHO cells and native LH receptors on both KGN human granulosa-derived tumor cells and M17 human neuroblastoma cells before and after exposure to human chorionic gonadotropin (hCG). Compared with LH receptors on untreated cells, LH receptors on cells treated with 100 nm hCG exhibit restricted lateral diffusion and are confined in small, nanometer-scale, membrane compartments. Similar to LH receptors labeled with Au-hCG, LH receptors labeled with gold-deglycosylated hCG, an hCG antagonist, also exhibit restricted lateral diffusion and are confined in nanoscale membrane compartments on KGN cells treated with 100 nm hCG. LH receptor point mutants lacking potential palmitoylation sites remain in large compartments despite treatment with 100 nm hCG as do LH receptors on cells treated with cytochalasin D. Finally, both polarization homotransfer fluorescence resonance energy transfer imaging and photon counting histogram analysis indicate that treatment with hCG induces aggregation of YFP-coupled LH receptors stably expressed on CHO cells. Taken together, our results demonstrate that binding of hCG induces aggregation of LH receptors within nanoscale, cell surface membrane compartments, that hCG binding also affects the lateral motions of antagonist binding LH receptors, and that receptor surface densities must be considered in evaluating the extent of hormone-dependent receptor aggregation.

The Extreme C-Terminal Region of Gαs Differentially Couples to the Luteinizing Hormone and β2-Adrenergic Receptors

The mechanisms of G protein coupling to G protein-coupled receptors (GPCR) share general characteristics but may exhibit specific interactions unique for each GPCR/G protein partnership. The extreme C terminus (CT) of G protein α-subunits has been shown to be important for association with GPCR. Hypothesizing that the extreme CT of Gα(s) is an essential component of the molecular landscape of the GPCR, human LH receptor (LHR), and β(2)-adrenergic receptor (β(2)-AR), a model cell system was created for the expression and manipulation of Gα(s) subunits in LHR(+) s49 ck cells that lack endogenous Gα(s). On the basis of studies involving truncations, mutations, and chain extensions of Gα(s), the CT was found to be necessary for LHR and β(2)-AR signaling. Some general similarities were found for the responses of the two receptors, but significant differences were also noted. Computational modeling was performed with a combination of comparative modeling, molecular dynamics simulations, and rigid body docking. The resulting models, focused on the Gα(s) CT, are supported by the experimental observations and are characterized by the interaction of the four extreme CT amino acid residues of Gα(s) with residues in LHR and β(2)-AR helix 3, (including R of the DRY motif), helix 6, and intracellular loop 2. This portion of Gα(s) recognizes the same regions of the two GPCR, although with differences in the details of selected interactions. The predicted longer cytosolic extensions of helices 5 and 6 of β(2)-AR are expected to contribute significantly to differences in Gα(s) recognition by the two receptors.

Rescue of expression and signaling of human luteinizing hormone G protein-coupled receptor mutants with an allosterically binding small-molecule agonist

Naturally occurring mutations of G protein-coupled receptors (GPCRs) causing misfolding and failure to traffic to the cell surface can result in disease states. Some small-molecule orthosteric ligands can rescue such misfolded receptors, presumably by facilitating their correct folding and shuttling to the plasma membrane. Here we show that a cell-permeant, allosterically binding small-molecule agonist (Org 42599) rescues the folding and cell surface expression, and therefore target cell signaling, of mutant human luteinizing hormone (LH) receptors (A593P and S616Y) that cause Leydig cell hypoplasia in man. Both mutant receptors were retained in the cytoplasm whereas WT receptor localized at the cell membrane, and binding of LH to cells expressing the mutant receptors was markedly lower than to those expressing the WT receptor. Incubation with Org 42599 increased mutant receptor expression, cell surface localization, and the proportion of mutant receptor in the mature glycosylated form. Importantly, although LH stimulated little (S616Y) or no (A593P) activation of cells expressing mutant receptors, incubation of cells with Org 42599 facilitated rescue of expression and stimulation by the native ligand, LH. Although Org 42599 could activate these receptors, it could not displace (125)I-labeled human LH binding to the WT receptor, indicating that it acts in an allosteric manner. Here we demonstrate a small-molecule GPCR allosteric agonist that functionally rescues intracellularly retained mutant LH receptors by facilitating their cell surface expression. This approach may have application for treatment of infertile patients bearing such mutations and, more broadly, for other misfolded GPCR mutants resulting in human pathologic processes.

Pharmacologic profiling of corifollitropin alfa, the first developed sustained follicle stimulant

Corifollitropin alfa (Elonva®, MSD, previously N.V. Organon or Schering-Plough Oss, The Netherlands) is a newly developed sustained follicle stimulant composed of the α subunit of human follicle-stimulating hormone (FSH) and a hybrid β subunit formed by fusion of the human chorionic gonadotropin β subunit carboxy terminal peptide with the β subunit of human FSH. Binding characteristics of corifollitropin alfa at the rat FSH receptor and transactivation properties at the rat FSH receptor, human luteinizing hormone (LH) receptor, and human thyroid-stimulating hormone receptor (TSH receptor) were assessed in vitro. Bioactivity of corifollitropin alfa in rats was also assessed. Serum corifollitropin alfa levels in rats and dogs were used to derive the main pharmacokinetic parameters of corifollitropin alfa. Binding and transactivation profile of corifollitropin alfa to rat FSH receptor was specific and comparable to that of recombinant human FSH, with no intrinsic TSH receptor or LH receptor activation. From pharmacokinetic studies, circulating half-life of corifollitropin alfa was calculated to be 17.3h in rats and 46.9h in dogs, 1.5- to 2-fold longer than recombinant FSH. Corifollitropin alfa demonstrated a 2- to 4-fold increase in bioactivity (ovarian weight, serum estradiol and progesterone, ovulated ova) over recombinant FSH across all in vivo parameters assessed. These data demonstrate that corifollitropin alfa is a specific ligand with high affinity for FSH receptor, lacking intrinsic activity for LH receptor and TSH receptor. By virtue of its increased in vivo half-life, corifollitropin alfa can be a valuable alternative to FSH by acting as a sustained follicle stimulant.

Differential Expression and Functional Characterization of Luteinizing Hormone Receptor Splice Variants in Human Luteal Cells: Implications for Luteolysis

The human LH receptor (LHR) plays a key role in luteal function and the establishment of pregnancy through its interaction with the gonadotropins LH and human chorionic gonadotropin. We previously identified four splice variants of the LHR in human luteinized granulosa cells (LGCs) and corpora lutea (CL). Real-time quantitative PCR revealed that expression of the full-length LHR (LHRa) and the most truncated form (LHRd) changed significantly in CL harvested at different stages of the ovarian cycle (P < 0.01, ANOVA). LHRa expression was reduced in the late luteal CL (P < 0.05). Conversely, an increase in LHRd expression was observed in the late luteal CL (P < 0.01). Chronic manipulation of human chorionic gonadotropin in LGC primary cultures supported the in vivo findings. LHRd encodes a protein lacking the transmembrane and carboxyl terminal domains. COS-7 cells expressing LHRd were unable to produce cAMP in response to LH stimulation. COS-7 cells coexpressing LHRd and LHRa also failed to generate cAMP in response to LH, suggesting that this truncated form has a negative effect on the signaling of LHRa. Immunofluorescence staining of LGC and COS-7 cells implied that there is a reduction in cell surface expression of LHRa when LHRd is present. Overall, these results imply expression of LHR splice variants is regulated in the human CL. Furthermore, during functional luteolysis a truncated variant could modulate the cell surface expression and activity of full-length LHR.

Induction of ovulation by a potent, orally active, low molecular weight agonist (Org 43553) of the luteinizing hormone receptor

In assisted reproductive technology, human chorionic gonadotrophin (hCG) is administered subcutaneously for the induction of oocyte maturation and ovulation. Our efforts to develop orally bioavailable luteinizing hormone (LH) receptor agonists have led to the discovery of Org 43553, a low molecular weight (LMW) LH receptor (LH-R) agonist. Org 43553 was tested in vitro and in vivo in pre-clinical pharmacological models to demonstrate efficacy and oral availability. Org 43553 is a potent stimulator of the human LH-R in vitro (EC(50) 3.7 nM). In primary mouse Leydig cells, Org 43553 stimulated testosterone production. Pharmacokinetic analyses showed high oral bioavailability in rats (79%) and dogs (44%) with a shorter half-life compared with hCG (3.4 versus 5.6 h in the rat). Ovulation induction by Org 43553 was demonstrated in immature mice as well as in cyclic rats after single-dose oral administration (50 mg/kg). The ovulated oocytes were of good quality as demonstrated by successful fertilization and implantation of normal embryos. In male rats, testosterone production was substantially induced after oral administration. Org 43553 is the first LMW LH-R mimetic with demonstrated in vivo efficacy upon oral administration and could therefore replace subcutaneously administered hCG. The elimination half-life of Org 43553 is substantially shorter than hCG, which could potentially represent a clinical benefit in reducing the risk of ovarian hyperstimulation syndrome (OHSS).

The extracellular domain of luteinizing hormone receptor dictates its efficiency of maturation

The processing of luteinizing hormone receptor (LHR) shows marked differences in different species. While the human LHR is predominantly expressed as the mature, 90 kDa species, rat LHR exists mostly in the 70 kDa precursor form. Since the extracellular domain of the LHR is unusually large in comparison with other G protein-coupled receptors, the present studies examined the role of extracellular domain in its processing. FLAG-tagged chimeric LH receptors were constructed by substituting the extracellular domain of the human receptor in rat LHR ( hrr) and the extracellular domain of the rat receptor in human LHR ( rhh). The intracellular processing, ligand binding and recycling of the chimeric receptors were compared with that of the wild type receptors in 293T cells. The results showed that the human and rat LHR were expressed predominantly as 90 and 70 kDa species, respectively, as expected. The introduction of the rat extracellular domain into the human LHR ( rhh) decreased the abundance of the mature form with an increase in the precursor form. Conversely, substitution of the extracellular domain of the rat LHR by the extracellular domain of the human LHR ( hrr) led to an increase in the mature form with a corresponding decrease in the precursor form. Changes were also observed in the ligand binding and recycling of the wild type and chimeric receptors. These results suggest that the extracellular domain of the LHR is one of the determinants that confer its ability for proper maturation and cell surface expression.

Asp330 and Tyr331 in the C-terminal Cysteine-rich Region of the Luteinizing Hormone Receptor Are Key Residues in Hormone-induced Receptor Activation

The luteinizing hormone (LH) receptor plays an essential role in male and female gonadal function. Together with the follicle-stimulating hormone (FSH) and thyroid stimulating hormone (TSH) receptors, the LH receptor forms the family of glycoprotein hormone receptors. All glycoprotein hormone receptors share a common modular topography, with an N-terminal extracellular ligand binding domain and a C-terminal seven-transmembrane transduction domain. The ligand binding domain consists of 9 leucine-rich repeats, flanked by N- and C-terminal cysteine-rich regions. Recently, crystal structures have been published of the extracellular domains of the FSH and TSH receptors. However, the C-terminal cysteine-rich region (CCR), also referred to as the "hinge region," was not included in these structures. Both structure and function of the CCR therefore remain unknown. In this study we set out to characterize important domains within the CCR of the LH receptor. First, we mutated all cysteines and combinations of cysteines in the CCR to identify the most probable disulfide bridges. Second, we exchanged large parts of the LH receptor CCR by its FSH receptor counterparts, and characterized the mutant receptors in transiently transfected HEK 293 cells. We zoomed in on important regions by focused exchange and deletion mutagenesis followed by alanine scanning. Mutations in the CCR specifically decreased the potencies of LH and hCG, because the potency of the low molecular weight agonist Org 41841 was unaffected. Using this unbiased approach, we identified Asp(330) and Tyr(331) as key amino acids in LH/hCG mediated signaling.