Heterodimerization of the Calcium-sensing receptor with the GabaB receptors in the breast.

项目概要/摘要 钙敏感受体（CaSR）是一种G蛋白偶联受体（GPCR）， 细胞外钙离子的变化它作为一种专性二聚体发挥作用，并与不同的G蛋白偶联， 包括Gai或Gas。CaSR广泛表达， 包括乳腺上皮细胞在内的多种细胞类型中的增殖、分化、死亡和离子转运 （MEC），其中它调节甲状旁腺相关蛋白（PTHrP）和乳钙的产生 运输在哺乳期，MEC上CaSR的激活通过刺激Gai和Ca 2+抑制PTHrP分泌， 降低cAMP水平。然而，在乳腺癌细胞中，CaSR的激活增加，而不是增加。 减少PTHrP分泌，因为在这些细胞中，CaSR激活Gas并增加cAMP水平。的 CaSR在哺乳生理学和乳腺癌病理生理学中具有重要功能，因此， 更好地了解其在乳腺上皮细胞中下游信号事件的调节。新出现的数据 证明CaSR可以与2种代谢型GabaB受体GABBR 1和GABBR 2异源二聚化。 GABBR 2的异源二聚化，并且本申请的中心前提是CaSR与GABBR 2的异源二聚化。 GABBR 1和/或GABBR 2改变CaSR信号传导、PTHrP产生和跨上皮钙 通过乳腺上皮细胞转运。具体来说，我们假设，在哺乳期， GABBR 1表达和GABBR 2表达的增加促进CaSR/GABBR 2的形成。 在MEC中的异二聚体，这反过来又增加了膜CaSR的表达，并加强了细胞间的偶联。 CaSR到Gai。为了探索这一假设，我们提出了三个具体目标。目标1将研究如何 与GABBR 1或GABBR 2的异源二聚化改变了细胞中CaSR的表达、信号传导和PTHrP的产生。 体外培养乳腺上皮细胞。AIM 2将使用转基因小鼠来检测异源二聚化是否 GABBR 2在体内调节泌乳乳腺中的CaSR表达和功能。目标3将使用 基因修饰小鼠，以检查GABBR 1的异源二聚化是否调节CaSR表达 并在体内哺乳乳房中发挥作用。该提案中概述的研究将探索新的生物学， 对哺乳生理学非常重要，也对乳腺癌病理生理学有影响。这些 研究有可能发现治疗性靶向CaSR的新方法。

PROJECT SUMMARY/ABSTRACT The calcium-sensing receptor (CaSR) is a G protein-coupled receptor (GPCR) that signals in response to changes in extracellular calcium. It functions as an obligate dimer and couples to different G-proteins, including Gai or Gas, in a context- or cell type-specific manner. The CaSR is widely expressed and alters proliferation, differentiation, death and ion transport in a variety of cell types, including mammary epithelial cells (MECs), where it regulates the production of parathyroid hormone-related protein (PTHrP) and milk calcium transport. During lactation, activation of the CaSR on MECs inhibits PTHrP secretion by stimulating Gai and reducing cAMP levels. However, in breast cancer cells, activation of the CaSR increases, rather than decreases, PTHrP secretion because, in these cells, the CaSR activates Gas and increases cAMP levels. The CaSR has important functions in both lactation physiology and breast cancer pathophysiology, so it is critical to better understand the regulation of its downstream signaling events in breast epithelial cells. Emerging data demonstrate that the CaSR can heterodimerize with the 2 metabotropic, GabaB receptors, GABBR1 and GABBR2 and the central premise of this application is that heterodimerization of the CaSR with GABBR1 and/or GABBR2 alters CaSR signaling, PTHrP production and transepithelial calcium transport by mammary epithelial cells. Specifically, we hypothesize that, during lactation, reductions in GABBR1 expression and increases in GABBR2 expression promote the formation of CaSR/GABBR2 heterodimers in MECs, which, in turn, increases membrane CaSR expression and reinforces coupling of the CaSR to Gai. In order to explore this hypothesis, we propose 3 Specific Aims. Aim 1 will examine how heterodimerization with GABBR1 or GABBR2 alters CaSR expression, signaling and PTHrP production in breast epithelial cells in vitro. Aim 2 will use genetically modified mice to examine whether heterodimerization with GABBR2 regulates CaSR expression and function in the lactating breast in vivo. Aim 3 will use genetically modified mice to examine whether heterodimerization with GABBR1 regulates CaSR expression and function in the lactating breast in vivo. The studies outlined in this proposal will explore novel biology of great importance for lactation physiology that also has implications for breast cancer pathophysiology. These studies have the potential to discover novel ways to target the CaSR therapeutically.