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The Calcium-Sensing Receptor Is Involved in Follicle-Stimulating Hormone-Induced Cumulus Expansion in in vitro Cultured Porcine Cumulus-Oocyte Complexes. Liu H et al. (2021) The Calcium-Sensing Receptor (CASR) is a G protein-coupled receptor of the C family that reportedly promotes maturation of porcine oocytes. However, its role in cumulus expansion of cumulus-oocyte complexes (COCs) is not well known. This study was conducted to determine the role of CASR and potential mechanisms involved during in vitro maturation (IVM) of porcine COCs. After culture of COCs in follicle-stimulating hormone (FSH)-supplement maturation medium for 24 h, the time of breakdown of the germinal vesicle (GVBD), indicative of initiation of meiotic maturation, resulted in an increased (p < 0.05) CASR mRNA expression level in cumulus cells. Moreover, IVM of COCs in 10 μM of the CASR agonist NPS R-568 promoted (p < 0.05) cumulus expansion but only in FSH-containing medium. Conversely, 20 μM of the CASR inhibitor NPS2390 precluded cumulus expansion. We next tested the effect of the CASR agonist/inhibitor on the expression of cumulus expansion-related genes. The CASR agonist significantly upregulated the expression of hyaluronan acid synthase 2 (HAS2), whereas the CASR inhibitor downregulated the expression of all HAS2, prostaglandin-endoperoxide synthase 2 (PTGS2), and tumor necrosis factor a-induced protein 6 (TNFAIP6). Altogether, these results suggest that CASR activity is involved in FSH-stimulated porcine cumulus expansion.//////////////////Role of calcium-sensing receptor in regulating spontaneous activation of post-ovulatory aging rat oocytes†. Yang R et al. (2017) Mechanisms for post-ovulatory aging (POA) of oocytes and for spontaneous activation (SA) of rat oocytes are largely unknown. Expression of calcium-sensing receptor (CaSR) in rat oocytes and its role in POA remain unexplored. In this study, expression of CaSR in rat oocytes aging for different times was detected by immunofluorescence microscopy and western blotting and the role of CaSR in POA was determined by observing the effects of regulating its activity on SA susceptibility and cytoplasmic calcium levels of oocytes. The results showed that CaSR was expressed in rat oocytes. Oocytes recovered 19 h post hCG injection were more susceptible to SA and expressed more functional CaSR than oocytes recovered 13 h after hCG injection, although both expressed the same level of total CaSR protein. Treatment with CaSR antagonist significantly suppressed cytoplasmic calcium elevation and SA of oocytes. Activation of Na-Ca2+ exchanger with NaCl inhibited SA to a greater extent than suppression of CaSR with NPS-2143, suggesting that calcium sources other than CaSR-controlled channels contributed to the elevation of cytoplasmic calcium. Treatment with T- or L-type calcium channel blockers significantly reduced SA. Suppression of all calcium channels tested reduced SA to minimum. It is concluded that the level of CaSR functional dimer protein, but not that of the total CaSR protein, was positively correlated with the SA susceptibility during POA of rat oocytes confirming that CaSR is involved in POA regulation. Blocking multiple calcium channels might be a better choice for efficient control of SA in rat oocytes.//////////////////
The Extracellular Calcium-Sensing Receptor (CASR) Regulates Gonadotropins-Induced Meiotic Maturation of Porcine Oocytes. Liu C et al. (2015) Gonadotropins and epidermal growth factor (EGF) play crucial roles in promoting oocyte maturation. The regulatory network downstream these key factors are not well understood. The present study was designed to investigate the role of the calcium-sensing receptor (CASR) in porcine oocyte in vitro maturation. CASR expression was up-regulated in oocytes matured in gonadotropin-containing medium. Cortical distribution of CASR was enhanced with gonadotropins but not EGF. Supplement of a CASR agonist (NPS R-568) in the gonadotropin (FSH and/or LH) containing maturation medium significantly enhanced oocyte nuclear maturation. Addition of NPS2390, a CASR antagonist, compromised oocyte nuclear maturation. Furthermore, increased cortical distribution and decreased expression of CASR was observed after the NPS R-568 treatment. Oocytes treated with NPS R-568 had higher concentration of CYCLIN B1, decreased reactive oxygen species and increased glutathione levels, indicating of advanced cytoplasmic maturation. In contrast, NPS2390 treatment compromised oocyte cytoplasmic maturation. A higher blastocyst formation rate after parthenogenetic activation was observed when oocytes were matured in the presence of the CASR agonist, NPS R-568. MAPK3/1 phosphorylation was increased during IVM and after NPS R-568 treatment, and decreased following CASR antagonist supplementation. Taken together, our data showed that the CASR is a gonadotropin regulated factor that promotes porcine oocyte maturation in a MAPK dependent manner.//////////////////
The extracellular Calcium Sensing Receptor (CaSR) is expressed in the cumulus-oocyte complex in mammalians and modulates oocyte meiotic maturation. De Santis T et al. The extracellular Calcium Sensing Receptor (CaSR) plays an important role in cells involved in calcium (Ca2+) homeostasis by directly sensing changes in the extracellular Ca2+ ion concentration. We previously reported the localization and quantitative expression of CaSR protein in human oocytes. In this study, we examined the expression and the functional role of CaSR during oocyte meiotic maturation in a large mammal animal model, equine. As in human, CaSR protein was found to be expressed in equine oocytes and cumulus cells. Western blot analysis revealed a single 130 kDa band in denuded oocytes and a doublet of 130-120 kDa in cumulus cells. CaSR labeling was observed by confocal microscopy in cumulus cells and in oocytes on the plasma membrane and within the cytoplasm at all examined stages of meiosis. Functionally, the CaSR allosteric effector NPS R-467, in presence of 2.92 mM external Ca2+, increased oocyte maturation rate in a dose-dependent manner and its stimulatory effect was attenuated by pre-treatment with the CaSR antagonist NPS 2390. NPS R-467 had no effect in suboptimal external Ca2+ (0.5 mM), indicating that it requires higher external Ca2+ to promote oocyte maturation. In oocytes treated with NPS R-467, CaSR staining increased at the plasmalemma and was reduced in the cytosol. Moreover, NPS R-467 increased the activity of mitogen-activated protein kinases (MAPK), also called extracellular-signal-regulated kinases (ERK), in cumulus cells and oocytes. These results provide evidence of a novel signal transduction pathway modulating oocyte meiotic maturation in mammals in addition to the well known systemic hormones.
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Expression of Calcium-Sensing Receptor in Quail Granulosa Explants: A Key to Survival During Folliculogenesis. Diez-Fraile A et al. This study investigated the potential role of the calcium-sensing receptor (CaR) in mediating survival of granulosa cells (GCs) in follicles of the Japanese quail (Coturnix coturnix japonica). Immunoreactivity of CaR was shown in GCs of quail preovulatory follicles as well as in the remnants of the GC layer after ovulation. Conversely, the CaR could not be detected by immunocytochemistry in the granulosa of smaller undifferentiated follicles. The presence of CaR in follicles destined to ovulate was confirmed by immunoblot and the receptor was identified as a protein of 115-125 kDa. Addition of different CaR agonists to granulosa explants in culture for 24 hr caused inhibition of apoptosis elicited by gonadotropin withdrawal on its own or in combination with C(8)-ceramide addition. Furthermore, R-568, a specific, positive allosteric modulator of CaR, not only inhibited apoptosis but also increased GC number per viewing field in cultured granulosa explants. This observation could be attributed not to a rise in GC proliferation but to a more compact tissue structure, including a distinct distribution pattern of connexin-43 gap junction proteins. Incubation in the presence of LY294002, a specific phosphatidylinositol-3 kinase inhibitor, increased GC apoptosis, indicating that this pathway is involved in GC survival signaling. However, LY294002-induced apoptosis was considerably attenuated by incubation with R-568, indicating that other pathways might be major contributors to the survival mediated by CaR agonists. We provide direct evidence for the presence of CaR in preovulatory granulosa explants and suggest a pivotal role for CaR in follicle selection. Anat Rec, 2010. (c) 2010 Wiley-Liss, Inc.
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Mutations |
2 mutations
Species: human
Mutation name:
type: naturally occurring
fertility: subfertile
Comment: Influence of gene variants related to calcium homeostasis on biochemical parameters of women with polycystic ovary syndrome. Ranjzad F et al. (2011) The purpose of this study was to evaluate the associations between polymorphisms in vitamin D receptor (VDR), parathyroid hormone (PTH), calcium sensing receptor (CASR), insulin receptor (INSR), and adiponectin (ADIPOQ) genes and biochemical characteristics of women with polycystic ovary syndrome (PCOS). Serum levels of LH, FSH, estradiol, testosterone, prolactin, SHBG, glucose, IGF-1, IGFBP-1, calcium, phosphorus, PTH, 25(OH)D, and 1,25(OH)(2) D were measured in 56 women with PCOS. Furthermore, genotyping five, one, one, two, and two polymorphisms of the VDR, PTH, CASR, INSR, and ADIPOQ genes, respectively, were performed. The VDR TaqI "CC" genotype was associated with elevated serum levels of LH (p = 0.011). There were significant associations between decreased levels of SHBG and both VDR BsmI "GG" (p = 0.009) and ADIPOQ BsmI "CC" (p = 0.016) genotypes. Furthermore, patients with CaSR Hin1I "TG" genotype showed higher HoMA-IR (p = 0.008). All these associations remained significant after Bonferroni correction. In addition, phosphorus correlated negatively with estradiol (r = -0.298, P = 0.026) and positively with glucose (r = 0.287, P = 0.032). These data indicated for the first time that it is possible that the VDR and CASR gene variants through their effects on LH and SHBG levels, and insulin resistance are involved in pathogenesis of PCOS.//////////////////
Species: mouse
Mutation name:
type: null mutation
fertility: embryonic lethal
Comment: Rescue of the skeletal phenotype in CasR-deficient mice by transfer onto the Gcm2 null background. Tu Q et al. (2003) To understand the role of the calcium-sensing receptor (CasR) in the skeleton, we used a genetic approach to ablate parathyroid glands and remove the confounding effects of elevated parathyroid hormone (PTH) in CasR-deficient mice. CasR deficiency was transferred onto the glial cells missing 2-deficient (Gcm2-deficient) background by intercrossing CasR- and Gcm2-deficient mice. Superimposed Gcm2 deficiency rescued the perinatal lethality in CasR-deficient mice in association with ablation of the parathyroid glands and correction of the severe hyperparathyroidism. In addition, the double homozygous CasR- and Gcm2-deficient mice demonstrated healing of the abnormal mineralization of cartilage and bone associated with CasR deficiency, indicating that rickets and osteomalacia in CasR-deficient mice are not due to an independent function of CasR in bone and cartilage but to the effect of severe hyperparathyroidism in the neonate. Analysis of the skeleton of 6-week-old homozygous CasR- and Gcm2-deficient mice also failed to identify any essential, nonredundant role for CasR in regulating chondrogenesis or osteogenesis, but further studies are needed to establish the function of CasR in the skeleton. In contrast, concomitant Gcm2 and CasR deficiency failed to rescue the hypocalciuria in CasR-deficient mice, consistent with direct regulation of urinary calcium excretion by CasR in the kidney. Double Gcm2- and CasR-deficient mice provide an important model for evaluating the extraparathyroid functions of CasR.//////////////////
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