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

项目摘要/摘要 钙敏感受体(CaSR)是一种G蛋白偶联受体(GPCR)，它通过 细胞外钙离子的变化。它作为专有二聚体与不同的G蛋白偶联， 包括GAI或Gas，以特定于上下文或单元类型的方式。CASR被广泛表达和改变 多种细胞类型的增殖、分化、死亡和离子转运，包括乳腺上皮细胞 (MECS)，在那里它调节甲状旁腺激素相关蛋白(PTHrP)和牛奶钙的产生 运输。在哺乳期，MECs上CaSR的激活通过刺激GAI和PTHrP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 减少PTHrP的分泌，因为在这些细胞中，CaSR激活Gas并增加cAMP水平。这个 CASR在哺乳期生理学和乳腺癌病理生理学中都具有重要作用，因此， 更好地了解其下游信号事件在乳腺上皮细胞中的调节。新兴数据 证明CaSR可以与两种代谢性GABAB受体、GABBR1和GABBR1异源二聚体。 GABBR2和这一应用的中心前提是CaSR与 GABBR1和/或GABBR2改变CaSR信号、PTHrP产生和跨皮细胞钙 乳腺上皮细胞的运输。具体地说，我们假设，在哺乳期， GABBR1表达和GABBR2表达增加促进CaSR/GABBR2的形成 MECs中的异二聚体，这反过来增加了膜CaSR的表达，并加强了 CASR转到GAI。为了探索这一假说，我们提出了三个具体目标。目标1将研究如何 与GABBR1或GABBR2的异源二聚改变CaSR的表达、信号和PTHrP的产生 乳腺上皮细胞体外培养。AIM 2将使用转基因小鼠来检查异源二聚体 GABBR2在体内调节CaSR在哺乳期乳腺的表达和功能。AIM 3将使用 转基因小鼠检测与GABBR1的异源二聚是否调节CaSR表达 并在体内的哺乳乳房中发挥作用。这项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，对乳腺癌病理生理学也有影响。这些 研究有可能发现治疗靶向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.