Physiology of LGR7 and LGR8 in Gonadal Tissues

描述(申请人提供)：经典激素松弛素属于一个具有保守的双链结构的多肽激素家族。广泛的研究表明，松弛素在怀孕和非怀孕状态下对女性生理起着重要作用，而与其同源的基因INSL3在男性生殖发育中起着重要作用。虽然松弛素是由卵巢黄体细胞产生的，而INSL3是由睾丸间质细胞以及卵巢的钙和黄体细胞产生的，但它们在性腺中的生理作用尚不清楚。早期的研究表明，在包括性腺在内的靶组织中存在松弛蛋白和INSL3结合部位。然而，对这些配体的假定受体的研究是有限的，因为对这些低水平表达的蛋白质进行配体结合分析遇到了困难。我们最近的研究表明，松弛素能激活孤儿受体LGR7和LGR8，而INSL3特异性地激活LGR8。除了证明cAMP通路在LGR7和LGR8信号中的作用外，我们还产生了LGR7的可溶性配体结合外区作为功能拮抗剂。LGR7可溶性胞外区对妊娠小鼠的延缓分娩作用。在这里，我们建议通过检测嵌合受体的配基信号来分析LGR7和LGR8的结构域对受体功能的重要作用。基于我们在隐睾症患者中发现的LGR8变体，我们将进一步测试LGR8变体的INSL3激活。我们已经获得了LGR7和LGR8在睾丸和卵巢中表达的初步数据，并建议阐明LGR7和LGR8在性腺生理中的生理作用。我们将根据cAMP的产生和其他反应来表征LGR7和LGR8在特定类型的性腺细胞中的表达以及它们对松弛素和INSL3的反应性。我们将利用LGR7和LGR8的可溶性胞外结构域作为功能拮抗剂，在体内研究松弛素和INSL3在睾丸和卵巢生理中的生理作用。拟议的研究应该能更好地了解松弛素相关激素以及LGR7和LGR8受体在性腺生理和其他生殖过程中的作用。

DESCRIPTION (provided by applicant): The classic hormone relaxin belongs to a family of peptide hormones with a conserved two-chain structure. Extensive studies have demonstrated that relaxin plays important roles in female physiology during pregnant and nonpregnant states and a paralogous gene, INSL3, is important in male reproductive development. Although relaxin is produced by ovarian luteal cells whereas INSL3 is produced by testis Leydig cells as well as ovarian the cal and luteal cells, their physiological roles in the gonads are unclear. Earlier studies suggested the presence of relaxin and INSL3 binding sites in target tissues including the gonads. However, studies on the putative receptors for these ligands were limited due to difficulties involved in performing ligand-binding assays for these proteins expressed at low levels. Our recent studies demonstrated that relaxin activates the orphan receptors LGR7 and LGR8 whereas INSL3 specifically activates LGR8. In addition to demonstrating the role of cAMP pathways in LGR7 and LGR8 signaling, we generated the soluble ligand-binding ectodomain of LGR7 to serve as a functional antagonist. Treatment with the soluble ectodomain of LGR7 delayed parturition of pregnant mice. Here, we propose to analyze the domains of LGR7 and LGR8 that are important for receptor function by testing ligand signaling of chimeric receptors. Based on our findings of LGR8 variants in cryptorchid patients, we will further test INSL3 activation of a LGR8 variant. We have obtained preliminary data indicating the expression of LGR7 and LGR8 in the testis and ovary and propose to elucidate the physiological roles of LGR7 and LGR8 in gonadal physiology. We will characterize the expression of LGR7 and LGR8 in specific gonadal cell types and their responsiveness to relaxin and INSL3 based on cAMP production and other responses. We will use the soluble ectodomains of LGR7 and LGR8 as functional antagonists to demonstrate the physiological roles of relaxin and INSL3 in testis and ovarian physiology in vivo. The proposed studies should provide a better understanding on the role of relaxin-related hormones and LGR7 and LGR8 receptors in gonadal physiology and other reproductive processes.