PMCA2 regulates mammary gland involution

描述(申请人提供)：质膜钙ATPase 2(PMCA2)将钙转运到牛奶中，并调节哺乳后退化过程中乳腺上皮细胞(MEC)的死亡。此外，乳腺癌中PMCA2的表达与患者的生存呈负相关。NHERF1是一种支架分子，它利用PDZ-Motif相互作用将离子通道、离子泵和受体连接到肌动蛋白细胞骨架上，以促进上皮细胞顶端表面的信号复合体。我们现在已经产生了大量的初步数据表明，PMCA2与NHERF1和ErbB2/HER2/Neu(HER2)相互作用，调节MEC存活和哺乳期间的HER2信号。初步数据还表明，PMCA2表达的基因操作深刻地影响了HER2介导的肿瘤形成。我们的主要假设是，PMCA2、NHERF1和HER2在哺乳期形成一个功能复合体，需要将钙转运出MEC，维持活跃的HER2信号，并防止MEC过早死亡。我们认为，在断奶后，MEC因乳汁停滞而膨胀，破坏了这种复合体，导致细胞内钙增加和HER2信号的抑制，这两者结合在一起激活了MEC死亡的溶酶体通透性(LMP)途径。最后，我们认为PMCA2/NHERF1/HER2复合体在恶性转化过程中重新表达并激活HER2信号，支持新出现的癌细胞的生存，并推动HER2阳性乳腺癌的进展。为了验证这一假设，我们提出了4个具体目标。目标1将研究在哺乳期PMCA2、NHERF1和HER2是否在一个多蛋白质复合体中相互作用，以及早期退化期间的乳汁停滞是否扰乱这个复合体。目的2研究PMCA2是否在哺乳期和退化期调节细胞死亡和HER2活性的钙-钙蛋白-LMP途径。目的3将研究NHERF1的缺失是否通过激活LMP途径和抑制HER2活性来模拟PMCA2的缺失。目的4将研究PMCA2和/或NHERF1是否调节HER2介导的小鼠肿瘤形成。这些研究将促进我们对LMP细胞死亡途径的认识，有助于我们更好地理解乳汁淤积如何启动乳腺退缩，并将为HER2在哺乳期和恶变过程中的表达、定位和信号调节提供新的见解。最后，我们的研究将验证HER2阳性乳腺癌潜在新治疗靶点的新途径。

DESCRIPTION (provided by applicant): The plasma membrane calcium ATPase 2 (PMCA2) transports calcium into milk and regulates mammary epithelial cell (MEC) death during post-lactation involution. Furthermore, PMCA2 expression in breast cancers correlates inversely with patient survival. NHERF1 is a scaffolding molecule that utilizes PDZ- motif interactions to connect ion channels, ion pumps and receptors to the actin cytoskeleton in order to facilitate signaling complexes at the apical surface of epithelial cells. We now have generated considerable preliminary data showing that PMCA2 interacts with NHERF1 and ErbB2/HER2/Neu (HER2) to regulate MEC survival and HER2 signaling during lactation. Preliminary data also suggest that genetic manipulation of PMCA2 expression profoundly affects HER2-mediated tumor formation. Our overarching hypothesis is that PMCA2, NHERF1 and HER2 form a functional complex during lactation that is required to transport calcium out of MECs, to maintain active HER2 signaling and to prevent premature MEC death. We propose that, after weaning, distension of the MECs in response to milk stasis disrupts this complex, which causes an increase in intracellular calcium and an inhibition of HER2 signaling, both of which combine to activate the lysosomal permeability (LMP) pathway of MEC death. Finally, we propose that the PMCA2/NHERF1/HER2 complex is re-expressed and activates HER2 signaling during malignant transformation, supporting the survival of emerging cancer cells and driving the progression of HER2-positive breast cancers. In order to test this hypothesis, we propose 4 specific aims. Aim 1 will examine whether PMCA2, NHERF1 and HER2 interact within a multi-protein complex during lactation and whether milk stasis during early involution disrupts this complex. Aim 2 will examine whether PMCA2 regulates a calcium-calpain-LMP pathway of cell death and HER2 activity during lactation and involution. Aim 3 will examine whether loss of NHERF1 mimics loss of PMCA2 by activating the LMP pathway and inhibiting HER2 activity during involution. Aim 4 will examine whether PMCA2 and/or NHERF1 regulate HER2-mediated tumor formation in mice. These studies will advance our knowledge of the LMP pathway of cell death, will help us better understand how milk stasis initiates mammary involution and will provide new insight into the regulation of HER2 expression, localization and signaling during lactation and during malignant transformation. Finally, our studies will validate novel pathway for potential new therapeutic targets in HER2-positive breast cancer.