PMCA2 regulates mammary gland involution and breast cancer

PMCA 2是一种钙泵，表达于乳腺上皮细胞（MEC）的顶膜， 哺乳期它负责运输60-70%的乳钙。断奶后，乳汁淤积迅速减少 PMCA 2表达，导致细胞内钙持续增加。初步数据显示， 细胞内钙离子的升高可能是一种生化信号，它将乳汁停滞与细胞内钙离子的激活联系起来， 溶酶体生物发生、STAT 3磷酸化和溶酶体依赖性细胞死亡（LDCD）。在最后一个周期中， 在这项研究中，我们证明PMCA 2也在乳腺癌中重新表达，并与乳腺癌相关。 ErbB 2/HER 2水平和死亡率增加。我们现在已经定义了PMCA 2，NHERF 1， Ezrin、HSP 90和ErbB 2是ErbB 2及其下游生物化学物质的膜保留所需的 信号抑制PMCA 2可增加细胞内钙，并导致PKCa依赖性的 这种多蛋白复合物以及ErbB 2的泛素化、内化和降解。正常 MEC、NHERF 1、ezrin和PMCA 2在顶端质膜内相互作用，而ErbB 2与一个细胞因子相互作用。 一种叫做Erbin的支架蛋白，位于基底外侧膜。初步数据显示， 在浸润性乳腺癌细胞中，PMCA 2、Ezrin和NHERF 1与Erbin和ErbB 2混合 这种复合物在曲妥珠单抗耐药的乳腺癌中大大上调， 癌细胞这项拨款申请的前提/假设有三个方面：1）乳汁淤积迅速减少 PMCA 2表达导致细胞内钙持续增加，进而引发LDCD; 2） 细胞极性的丧失使得顶端PMCA 2-NHERF 1-Ezrin复合物和细胞间的新型相互作用成为可能。 基底外侧，Erbin-ErbB 2复合物，其加速ErbB 2介导的转化;和3）上调 PMCA 2和ErbB 2之间的相互作用有助于曲妥珠单抗耐药性的发展。我们 提出三个具体目标。目的1将研究细胞内钙离子增加的机制， 浓度激活溶酶体生物发生、STAT 3和LDCD。目标2将测试PMCA 2的改变是否 ErbB 2/HER 2定位加速恶性转化。AIM 3将测试是否进一步上调 PMCA 2、NHERF 1、Ezrin、Erbin、HSP 90和ErbB 2之间的相互作用有助于曲妥珠单抗 阻力这些实验将提供重要的新知识的机制， 引发了退化他们将通过以下方式为MEC转型的早期步骤提供重要见解： ErbB2。他们将验证ErbB 2/HER 2阳性肿瘤的新型癌细胞特异性药物靶点，并将测试 在曲妥珠单抗耐药癌症中破坏这些相互作用的潜在治疗价值。

PMCA2 is a calcium pump expressed in the apical membrane of mammary epithelial cells (MECs) during lactation. It is responsible for transporting 60-70% of milk calcium. After weaning, milk stasis rapidly decreases PMCA2 expression, causing a sustained increase in intracellular calcium. Preliminary data suggest that this rise in intracellular calcium may serve as the biochemical signal that couples milk stasis to activation of lysosome biogenesis, STAT3 phosphorylation and lysosome-dependent cell death (LDCD). In the last cycle of this grant, we documented that PMCA2 is also re-expressed in breast cancers and correlates with ErbB2/HER2 levels and increased mortality. We have now defined interactions between PMCA2, NHERF1, Ezrin, HSP90 and ErbB2 that are required for membrane retention of ErbB2 and its downstream biochemical signaling. Inhibition of PMCA2 increases intracellular calcium and causes a PKCa-dependent disassembly of this multiprotein complex as well as the ubiquitinylation, internalization and degradation of ErbB2. In normal MECs, NHERF1, ezrin and PMCA2 interact within the apical plasma membrane while ErbB2 interacts with a different scaffolding protein called Erbin, at the basolateral membrane. Preliminary data show that, in DCIS lesions and in invasive breast cancer cells, PMCA2, Ezrin and NHERF1 intermix with Erbin and ErbB2 throughout the plasma membrane and that this complex is greatly upregulated in trastuzumab-resistant breast cancer cells. The premise/hypothesis of this grant application is three-fold: 1) that milk stasis rapidly decreases PMCA2 expression causing sustained increases in intracellular calcium, which, in turn, trigger LDCD; 2) that loss of cell polarity enables novel interactions between the apical, PMCA2-NHERF1-Ezrin complex and the basolateral, Erbin-ErbB2 complex that accelerate ErbB2-mediated transformation; and 3) that upregulation of interactions between PMCA2 and ErbB2 contribute to the development of trastuzumab resistance. We propose 3 specific aims. Aim 1 will examine the mechanisms whereby increased intracellular calcium concentrations activate lysosome biogenesis, STAT3 and LDCD. Aim 2 will test whether alterations in PMCA2 localization accelerate malignant transformation by ErbB2/HER2. Aim 3 will test whether further upregulation of interactions between PMCA2, NHERF1, Ezrin, Erbin, HSP90 and ErbB2 contributes to trastuzumab resistance. These experiments will provide important new knowledge of the mechanisms by which milk stasis triggers involution. They will contribute important insight into the early steps of transformation of MECs by ErbB2. They will validate novel cancer cell-specific drug targets for ErbB2/HER2-positive tumors and will test the potential therapeutic value of disrupting these interactions in trastuzumab-resistant cancers.