CAV-1 in Jak/STAT Signaling, Lactation, & Breast Cancer

描述(由申请人提供)：这项建议的长期目标是了解小窝蛋白-1在i)JAK/STAT信号转导、ii)哺乳和iii)乳腺癌发病机制中的作用。小窝是调节信号转导的“信息中心”。小窝蛋白-1(Cav-1)是小窝细胞膜的主要结构蛋白，存在于大多数细胞中。我们将人CAV-1定位于一个可疑的肿瘤抑制基因(7q31.1/D7S522)。此外，在多达16%的人类乳腺癌中，Cav-1基因发生了突变(P132L)。这一建议的目的是验证Cav-1的表达对调节哺乳的重要作用的假说，该假说是通过调节JAK/STAT信号来实现的，并且Cav-1的缺失有助于乳腺癌细胞的致瘤性。为了验证这一假设，我们将使用多种体内互补的方法，例如i)Cav-1缺失的小鼠模型和ii)在人类乳腺癌中发现的表达显性阴性Cav-1(PI32L)的转基因小鼠的发展。该项目的三个具体目标是：1)确定Cav-1在负调控JAK/STAT信号中的作用。我们将研究Cav-1在对催乳素反应的培养乳腺上皮细胞中Jak/STAT信号激活的影响。我们的初步结果表明，Cav-1通过抑制Jak介导的Stat5a的磷酸化来负向调节Jak/Stat5a信号转导；2)研究Cav-1在哺乳期和上皮细胞增殖中的作用。从荷尔蒙催乳素小瓶发出的信号，JAK/STAT通路控制着正常的乳腺发育。因此，如果Cav-1是JAK/STAT信号的负调控因子，我们可以预测Cav-1的表达缺失会导致早产。事实上，我们的初步结果表明，Cav-1基因缺失的小鼠表现出早产，以及JAK/Stat5a信号级联的过度激活；3)确定Cav-1(P132L)的转基因表达是否容易导致乳腺肿瘤的发生。为此，我们将产生在乳腺中转基因表达这种形式的Cav-1(P132L)的小鼠。我们的初步结果表明，Cav-1(P132L)在培养细胞中的作用是显性-负性的。此外，我们对Cav-1基因缺失的小鼠的初步结果显示，广泛的乳腺上皮增生发生在早期。我们预测，这种表型将加速Cav-1(P132L)转基因小鼠。我们将把Cav-1(P132L)转基因小鼠与其他成熟的乳腺肿瘤发生模型进行杂交，如MMTVErbB2和MMTV-多瘤中T小鼠。这些研究有望为了解Cav-1在JAK/STAT信号转导和体内乳腺肿瘤发生中的作用提供基础知识。

DESCRIPTION (provided by applicant): The long-term objective of this proposal is to understand the role of caveolin-1 in i) Jak/STAT signaling, ii) lactation, and iii) the pathogenesis of breast cancer. Caveolae function as "message centers" for regulating signal transduction. Caveolin-1 (Cav-1) is the principal structural protein of caveolae membranes that are found in most cells. We mapped human CAV-1 to a suspected tumor suppressor locus (7q31.1/D7S522). In addition, the Cav-1 gene is mutated (P132L) in up to 16% of human breast cancers. The aim of this proposal is to test the hypothesis that Cav-1 expression is important for regulating lactation via modulation of Jak/STAT signaling and that loss of Cav-1 contributes to the oncogenicity of breast cancer cells. To test this hypothesis, we will use a variety of complementary in vivo approaches, such as i) a Cav-1 null mouse model and ii) the development of transgenic mice that express dominant-negative Cav-1 (PI32L) found in human breast cancers. The three Specific Aims of the project are: 1) To determine the role of Cav-1 in negatively regulating Jak/STAT signaling. We will examine the effects of Cav-1 on the activation of Jak/STAT signaling in cultured mammary epithelial cells that are responsive to prolactin. Our preliminary results indicate that Cav-1 negatively regulates Jak/STAT5a signaling by inhibiting Jak-mediated phosphorylation of STAT5a; 2) To examine the role of Cav-1 in lactation and epithelial cell hyperplasia. Signaling from the hormone prolactin vial the Jak/STAT pathway controls normal mammary gland development. Thus, if Cav-1 were a negative regulator of Jak/STAT signaling, we would predict that a loss of Cav-1 expression leads to premature lactation. Indeed, our preliminary results show that Cav-1 null mice exhibit premature lactation, as well as hyper-activation of the Jak/STAT5a signaling cascade; and 3) To determine if transgenic expression of Cav-1 (P132L) predisposes towards mammary tumor development. For this purpose, we will generate Cav-1 (P132L) mice that transgenically express this form of Cav-1 in the mammary gland. Our preliminary results indicate that Cav-1 (P132L) acts in a dominant-negative fashion in cultured cells. In addition, our preliminary results with Cav-1 null mice show early development of wide-spread mammary epithelial hyperplasia. We predict that this phenotype will be accelerated Cav-1 (P132L) transgenic mice. We will cross Cav-1 (P132L) transgenic mice with other well-established models of mammary tumorigenesis, such as MMTVErbB2 and MMTV-polyoma middle T mice. It is expected that these studies will contribute fundamental knowledge towards understanding the role of Cav-1 in Jak/STAT signaling and mammary tumorigenesis in vivo.